BIOZOOM

CELL NUCLEUS STRUCTURE-FUNCTION

noreply@blogger.com (amith) — Tue, 27 Dec 2016 17:59:00 +0000

Structure and Functions of NUCLEAS In Cell

In 1832 " Robert Brown" discovered nucleus. It is the essential part of the cell

A definite nucleus is absent in prokaryotic cell. Instead of it a DNA molecules is present. It is called by “Prokaryotic cell". Ex : Bacteria.

Definite nucleus is present. It is covered by nuclear membrane.

The position of a nucleus in the cell is definite. It occupies more or less central position. Now and then it is pushed to die periphery.

Number:

a) Anurfeate: Nucleus is absent Ex : RBC of mammal

b) Mononucleate : It is very common. Usually the cell contains a single nucleus

b) Binucleate : Two nuclei are present. Ex : cells of cartilage.

c) poly nucleate: Three to many nuclei are present. In animals poly nucleate cell is called "Syncytial cell". Ex : Syncytial cell of osteoblast.

Shape :

It is usually oval. But its shape is dependent on the cell type.

a) Cylindrical: Ex : Columunar epithelium.

b) Horse shoe shape : Ex : Paramecium meganucleus.

c) tri lobed nucleus : Ex : WBC of mammals.

d) branched nucleus : Ex : Silk spining cell of insect larvae.

e) irregular nucleus : Ex : Glandular cell of insect.

Size :

The size of the nucleus varies with cell type . It is directly proportional to the amount of cytoplasm. "Hertwig " gave nucleo plasmic index.

Structure :The nucleus will show.

a) Nuclear membrane.

b) Nucleo-plasm or karyolymph.

c) Chromatin net work.

d) Nucleolus.

Nuclear membrane :

It is called nuclear envelope. It is 100 to 150 A⁰. The membr< nes are unit membranes. The outer membrane bears ribosomes, It is cor, nuous with endoplasmic reticulum.

Nuclear pores :

Nuclear membrane is not continuous. Here and there pores are present. Each pore is 500 tc 800 A ⁰ in diameter. Each pore is covered by annulus membrane The pore and annulus will be called "Pore Complex". Because of ithese pores nucleoplasm and cytoplasm will be continuous.

Nucleoplasm :

Below the nuclear membrane a transparent semifluid is present. It is granular. In this a chromatin network is present. It contains proteins, ions, enzymes, and nuclic acids. It is believed that nucleoplasm will take part in spindle formation.

3) Chromatin network :

In the nucleoplasm chromatin net work is present. In the inter phase nucleus the -chromosomes are fine threads, and in the form.of a net work.

Euchromatin & Heterochromatin :

In the interphase nucleus the chromatin net work shows dark stained regions. They are called heterochromatin regions, Light stained regions are called euchromatin.

In 1928 "Hertz" defined heterochromatin as condensed chromatin part. The hetero-chromatin is two types.

a) Facultative-hetero-chromatin :

This is a temporary state of inactivation of chromatin. In which one chromosome of the pair will becomes hetero chromatin. Ex : In mammals the second X chromosome in the somatic cells of female will become hetero-chromatin, it is called ban* body.

b) Constitutive hetero-chromatin :

It is present permanently. It is present in both chromosomes of the pair. It is common in nucleolar organising chromosomes.

Hetero-chromatic regions genitically inactive. Now a days it is believed that it contains polygens, for the synthesis of t RNA and 5S RNA. Functions :

1) It gives protection to the genome.

2)Helps in the reflection of DNA.

3)During synaptic pairing in meiosis it attracts the homologous chromosomes.

4) Nucleolus :

It was discovered by "Fontana". In almost all the cells in the inter-phase nucleus, nucleolus is present. The number may be one or two. In some cases hundreds of nuclei will be present. Ex. Amphibian oocyte.

The size of the nucleolus is depended upon the activity of the cell. They may be smaller or big.

The nucleous shows two parts,

a) Amorphous part,

b) Filamentous part

a) Amphorophous part contains four parts

i) Granular zone

ii) Fibrillar zone

iii) Protenaceious part,

iv) Nucleolar associated chromatid.

Nucleous contains RNA, proteins and enzymes. It is formed with the help of nucleolar organising chromosome. Functions :

1} It is helpful in biogenesis of ribosomes.

2) It plays a major role in mitosis.

Constitution of Nucleus:

It contains nucleo proteins, enzymes and inorganic salts. Low molecular weight proteins like histones, protamines are present. High molecular proteins contain tryptophan, tyrosine are constituent particles, DNA, RNA nuclei acids will be present. Salts of sodium, magnesium, calcium etc., some phospholipids are also present.

Functions of Nucleus:

1) Nucleus plays a major role in the general metabolism of the cell

2) It is helpful in the synthesis of ribosomes.

3) It is helpful in the synthesis of RNA.

4) It controls the synthesis of proteins.

5) It is the seat of heredity.

RIBOSOMES -STRUCTURE - FUNCTION

noreply@blogger.com (amith) — Tue, 27 Dec 2016 16:30:00 +0000

Ribosome Structure Types And Functions

In 1949 Claude observed ribosomes and called them as microsomes. In 1955 Pallade named them as Ribosomes.

Occurance:

In both eukaryotic and prokaryotic cells the ribosomes are present.

Number:

The number of Ribosomes is directly proportional to the RNA content of the cell. In a liver cell of Rabbit 10^s ribosomes are present.

Ribosomes are usually two kinds.

1) Ribosomes of prokaryotes are 70S type.

2) Ribosomes of eukaryotes are SOS type.

Each ribosome is made by two subunits, one is smaller and the other is bigger.

Association & Dissociation of the sub units :

At low concentration of Mg" the two ribosomal sub units remain united. If Mg" concentration increased by TO' times two ribosomes Unite and a dimmer is formed. If magnesium concentration much below then the ribosome divides into two sub-units

A) Types of Ribosomes :

1) 70S ribosome : These are present in bacteria and prokaryotes. Such 70S ribosomes are also seen in mitochondria and chloroplasts of the cell.

2) 80S ribosome : They are present in eukaryotic cells. They are comparatively larger than 70S ribosomes.

3) 70S and 60S ribosomes: The mitochondrial ribosomes of fungi arc 70S type. But the mitochondria ribosomes of animal are 60S type. This was stated by "Levine" in 1974.

Chemical composition: Ribosome is made by RNA and proteins. Small amounts of lipids and metallic ions are seen in it. In SOS ribosome RNA content is 45% and protein content is 50%.

On dissociation of ribosomes different types of proteins and RNA will be resulted.

1) Ribosomal RNA: !n SOS ribosomes 28S, 18S, 5S RNA are present

a) 28S RNA is present in 60S subunit.

b) 1SS RNA is present in 40S subunit.

c) 5S ribosomal RNA is seen in 60S subunit. It has only 12 nucleotides. It looks like clover leaf.

2) Ribosomal proteins : Primary binding proteins are present in the sub units. On dissociation split proteins are liberated.

Ribosome structure:

1) Ribosome shows two sub-units,

Larger sub-unit.
Smaller sub-unit.

The larger sub-unit will be attached to endoplasmic membrane.

2)In between the smaller and bigger subunits a channel is present. The channel is parallel to the membrane of the endoplasmic reticulum.

3)In this channel the m RNA moves, m RNA is bond to the smaller subunit.

4)-t RNA will attach to the larger sub-unit

5)On the larger sub unit two sites are present.

a) P site: It is the site where polypeptide chain is attached.

b) A site: To this site t RNA will attach which will transfer its amino acid to the growing polypeptide chain.

6)The recent studies have shown that the two sub units of the ribosome' will exist freely in the cytoplasm. During protein synthesis the two subunits are united. After the protein synthesis the two sub units will be separated.

Biogenesis of ribosome:

In prokaryotic cells synthesis of ribosomes will take place in the cytoplasm.

In eukaryotic cells the synthesis of ribosomes is carried on by the nucleus.

1) Nucleolar organizing chromosomes will give rise to 28S and 18S RNAs.

2) In the nucleolar region 4OS RNA will be present. This gives rise to 28S and 18S RNAs.

3) This 45S nucleolar RNA molecules will get CH₃ groups and these methylated molecules will unite with proteins. Thus 80S ribonucleo-protein molecule is formed. It is called RMP. (Ribonucleo protein molecule particle).

4) 45S RNA of 80S ribonucleoprotein molecule particle will split into 28S & 18S particle.

5) In the nucleus outside the nucleolus 5S r RNA will form.

6) 18S R RNA with proteins will come out of the nucleus and enter into cytoplasm. It associates with other proteins it becomes 40S sub unit.

7) The 28S r RNA & 5S r RNA with some proteins will enter into cytoplasm they give 60S sub unit.Thus ribosome is synthesized.

Functions :

Its main function is protein synthesis. With the help of m RNA, t RNA ribosome will produce new protein.
Many ribosomes are united with m RNA filament. It is called polysomes
They produce proteins.

ENDOPLASMIC RETICULUM-STRUCTURE- TYPES RETICULUM (ROUGH ER- SMOOTH ER) FUNCTIONS

noreply@blogger.com (amith) — Tue, 27 Dec 2016 08:23:00 +0000

Structure –Types And Functions Of Endoplasmic Reticulum

In the cytoplasm of the cell complex membrane bounded system is present. It was called cytoplasmic vacuolar system by "Sacz & De robertis" in 1975. This system contains endoplasmic reticule, nuclear envelop, and Golgi.

Endoplasmic Reticulum (E.R.) was first observed by "Porter, Claude, Fullam" in 1945.

Occurrence: In all eukaryotic cells E.R. is present. It is absent in R.B.C. of mammals and prokaryotes. In the embryonic cells E.R. is small. It is undifferentiated.

Types of E.R.: E.R. occurs in two forms a) Smooth E.R. b) Rough E.R.

Smooth E.R..- The E.R. without ribosomes is called smooth E.R. This is present in cells which synthesis steroids. In intestine cell, liver cells, retinal cells it is present.

Rough E.R: The E.R. shows ribosomes on its outer surface. They take up protein synthesis. This reticulum is more in protein synthesing cells.

Morphology: E.R. is represented in three forms; a) Cisternae b) Vesicles c) Tubules.

a) Cisternae : These are long unbranched flat structures. They are arranged parallely. They show 40 to 50 mill microns in diameter. They are more in liver pancreas, brain cells, etc.

b) Vesicles : They are oval membrane bounded structures. They are 25 to 500 mill microns in diameter. They occur in liver and pancreatic cells.

c) Tubules : They are small and branched. They show 50 to 190 mill microns in diameter. They are arranged irregularly in cell. They are seen in almost all the cells.

Electron microscopic structure of E.R.: All the three forms of E.R. will show double unit membranes. Each membrane shows 60 A⁰ thickness. The unit membrane show fluid mosaic nature of plasma membrane. Usually E.R. membrane is in contact with plasma membrane, nuclear membrane and Golgi. In 1965 "Palade" observed secretory granules in the E.R.

Biogenesis of E.R. : The origin and development of E.R. is not clearly

Known.

' l)From nuclear membrane: The membrane of E.R. resembles nuclear membrane and plasma membrane. Hence we believe that E.R. might have come from them.

2) E.R. Developed 'Denovo': It developed as it is.

3) Multistep mechanism: Rough E.R. is developed in the following way. a) Annulated lamellae: It was reported by "Meculloch" in 1952. From the nuclear membrane small structures are liberated as buds. They unite to form annulate lamellae. These lamellae are united to form cisternae. Thus E.R. is formed.

Functions:

1) Mechanical support: E.R. will give mechanical support to cytoplasm. Hence it is called cytoskeleton.

2) Intracellular transport: E.R. functions as circulatory system of the cell. It transport substance from one place to another place, in the cell it is called intracellular transport.

3) Protein synthesis : ER. will provide surface for the attachment of ribosomes. These ribosomes will synthesise the proteins.

4) Synthesis of lipoproteins : Smooth E.R. will synthesise lipids. In the Golgi complex the glycerides get associated with proteins produced by the E.R. Thus complex lipoproteins are formed.

5) Detoxification : Smooth E.R. will detoxify internal, or external toxins. If toxins are more in the body more smooth E.R. will be produced.

6) A.T.P. Synthesis : E.R. membranes are the sites of A.T.P, synthesis in the cell.

7) Formation of other membranes : In the cell E.R. gives rise to.

a) Cisternae of Golgi apparatus .

b) Outer membrane of nucleus.

8) impulse conduction : In the muscle sarcoplasmic eticulum will release calcium which is responsible for the muscle action In 1926 "Porter" stated that E.R. membrane shows ionic grandients, and electric potential.

Interrelationship of different cell membranes :

1) The outer membrane of the nucleus will give buds. They unite to form annulate lamellae.

2) Annulate lamellae will give rough E.R.

3) From smooth E.R. golgi will form.

4) Vesicles will give plasma lemma.

5)According to GERL system Golgi will give rise to primary lysosomes. Thus there is an interrelationship among the membrane systems.

GOLGI APPARATUS (GOLGI BODY)-STRUCTURE AND FUNCTIONS

noreply@blogger.com (amith) — Tue, 27 Dec 2016 07:33:00 +0000

GOLGI COMPLEX –STRUCTURE-FUNCTION

In the animal and plant cells clusters of fat filled structures are present. They are called Golgi apparatus or complex. In 1898 Camillo Golgi' recognised it in the nerve cell of the owl. The Golgi complex of invertebrates is called dictyosome.

Occurence : Golgi complex is seen in all eukaryotic cells. Golgi complex is not seen in mature sperm, red blood cell and prokaryotes.

Golgi complex occurs in two forms

a) Localized form : Golgi complex occurs singly and has a fixed position. (In between nucleus and secretory pore)

b) Diffused form: In the nerve and liver cells Golgi complex is scattered, in it each unit is called dictyosome.

Structure : Golgi body is seen in the form of three components.

1. Cisternae: These are tubular, flat, fluid filled sacs. They show 200 to 300A⁰ width. Each sac is covered by two membranes. In a dictyosome 3 to 7 cisterne are present. They are arranged one above the other. Their convex side is towards nucleus and their concave surface is towards plasma membrane. The convex side of the cisternae is called forming face. The concave surface is called maturing face. It shows big secreting vesicles. These secretory vesicles store secretory substances. They may develop into lysosomes.

Polarity of cisternae: The cisternae shows maturing face and forming face. Forming face is convex and towards nucleus. The smooth E.R. gives vesicles. They unite to form cisternae.

2.Golgi vesicles : On the forming face of golgi cisternae small vesicles are present. They are 400 A⁰ width. They usually develop form E.R.

3) Secretory vesicles: On the maturing face of golgi cisternae secretory vesicles are present. They contain secretory products of golgi. They finally change into lysosomes.

Chemical composition.

Golgi complex will be rich in chemical substances.

1) Phospholipids: These substances have a composition which is in between the structure of phospholipids of endoplasmic reticulum and plasma membrane.

2) Enzymes: ATP-ase, CPT-ase, transphorases, etc. enzymes are. present.

3) Carbohydrates: Glucose, manose, galactose carbohydrates are seen.

Origin of Golgi complex

1) From E R :beams&Kessel' in 1968 proposed that Golgi system cisternae arise from Endoplasmic reticulum.

2) Rough E.R. produces protein which will be transfer to smooth ER.

3) Vesicles are developed from smooth E.R.

4) By the fusion of vesicles cisternae are formed. From the cisternae secretory vesicles are formed on the maturing face. (These sides are called "G.E.R.L" - Golgi-Endoplasmic Reticulum-Lysosome)

2) From nuclear membrane: In 1965 "Bouch" described the origin of golgi from the outer membrane of the nucleus. Vesicles are pinched off from the outer nuclear membrane and they are united to form cistemae.

3) By the division pre-existing dictyosome During the cell division the number of dictyosomes will increase. In each daughter cell the number of dictyosomes will be equal to the dictyosome of parent cell.

4) Zones of exclusion: Each golgi complex is surrounded by a specific zone of cytoplasm. In this zone ribosomes and other organelles are absent. Such zone is called "Exclusive zone". E. R. present in this zone will show smooth surface.

Functions: Golgi complex is mainly connected with secretory function. In different types of cells different types of secretions are produced.

Golgi complex & secretion: The secretory mechanism will follow

1) Proteins are produced by ribosome.

2) They will be transmitted to smooth E.R.

3) From there they are concentrated at Golgi complex.

4) From the Golgi complex the secretory vesicles are formed.

They produce the secretion

The secretions are three types.

a) Holocrine secretion: The entire cell is filled with secretory product, it gives rise to secretions. Ex: Sebaceous gland.

b) Apocrine secretion: The secretory vesicles will come out of the plasma membrane. They take away small amount of cytoplasm. Ex : Apocrine sweat gland.

c) Merocrine secretion: Secretory vesicles will unit with P.M. and open to the exterior. Ex : Salivary gland.

S.No. ' Cell type-------- Golgi function

1. Pancreas -------Digestive enzymes

2. Haepatic cells of liver -----Secretion of lipids

3. Plasma cells of blood ------Immunoglobulins

4. Thyroid gland -------Thyroxin

2) Synthesis of glycoprotein: Most of the cells will produce glycoproteins. The glycoprotein contains a protein part and carbohydrate part. They are important for secretions.

3) Storage of secretory products : Ribosome synthesize proteins, they are discharged into E.R. They are concentrated in the cistemae. They are stored in secretory vesicles. Thus the glycoproteins are stored in Golgi.

4) Formation of lysosomes : From the maturing face of cistemae granules are produced. They are united to form lysosomes.

5) Acrosome formation. - "Burgos" stated that acrosome of the sperm is formed because of golgi spermatogensis golgi complex will develop into each vacuole

a small proacrosomal granule is formed. If spherical body. Inside each vacuoleIt increases in size and they are many, they unite to form a single granule . acrosomal granule is formed It forms the acrosome. Acrosome is helps

penetrate into ovum during fertilization.

LYSOSOMES –STRUCTURE-FUNCTIONS

noreply@blogger.com (amith) — Sun, 25 Dec 2016 18:06:00 +0000

Lysosomes-Structure –Enzymes-Polymorphic Nature-Function-Biogenesis

Lysosome : These are first observed in liver cells. They are 1.5 to 2 milii micron in size These are single membrane bounded structures. They were first called pericanalicular-dense bodies. "Christian De Duve" called them lysosomes in 1955. They were named as lysosomes because they contain hydrolytic enzymes.

Occurence: They are present in all animal cells ,except mammalian R.B.C. They are more in liver cells spleen cells, kidney cells etc.. In bacteria they are absent.

Shape & size : They are round or spherical bodies. They are .4 to .8 milli microns in size.

Structure : Each lysosome is covered by a unit membrane. It encloses a dense matrix. It shows 2 regions, outer dense part and central less dense part.

Chemical composition: Every lysosome will show hydrolytic enzyme. They are important in digestion of food such as 40 enzymes arc recognized in lysosome.

Polymorphism in lysosomes or kinds of lysosomes :

In the same cell at different times or in different cells 4 kinds of lysosome are reported.

a) Primary lysosome or storage granule :

1. It is a newly formed lysosome. -

2. It is formed from golgi.

3. it forms from G.E.R.L, which means 'Golgi associated with Endoplasmic Reticulum will give Lysosome". This was stated by Dyson 1978.

4. This is called original lysosome.

b) Phagosome or pinosome or digestive vacuole :

1. A original lysosome units with a phagocytic or pinocync vesicle and forms a phagosome.

2. In this phagosome the food is digested.

c) Autophagic vacuole or autolysosome :

When the organism is in a state of starvation the lysosome will start digesting the cell contents. Such lysosome is called autophagic vacuole.

d) Residual body :

After the process of digestion in phagosome or autophagic vacuole some materials are not digested. Such Iysosomes with undigested food is called residual body. This residual body will send the undigested matter through plasma membrane.

In nerve and muscle cells residual bodies are more in number. They are called, "Lipofucine granules". (By the estimation of these granules the age can be decided)

The polymorphic tendency of lysosome is not real, it is connected with the digestive activity of the lysosome.

List of some hydrolytic enzymes seen in Lysosome :

	Enzyme	Substrate on which	Result
		they act
1) Nucleases :
a)	Acid ribonu-	Polypeptides of	pentose sugar, radical,
	c lease...	R.N.A...	phosphate, nitrogen bases
b)	Acid deoxiribo-	Polypeptides of	Pentose sugar. Phosphate,
	nuclease	D.N.A...	nitrogen bases.
2)	Lipase :	Lipids	Fatty acids
3)	Pret eases &
	Peptidases	Proteins	Amino acids
4)	Phosphotases	:
a)	Acid phospho-	Phospho - rfTonoe-	Phosphates, fatty
	tase...	ters	acids etc.
b)	Phospho dies-	Oligonuclendes...	Phosphates,
	terase...		nitrogentases etc.
5)	Gvoycosidase
	Many enzyme
	groups are
	included...	Carbohydrates...	Monosaccharides.

Bio genesis of lysosomes :

The origin of lysosome is not clearly known. According to 'Dyson' 1978 the lysosomes arise from Golgi complex and endoplasmic reticulum. The protein granules produced by ribosome is stored in endoplasmic reticulum. They move in to smooth endoplasmic reticulum. From there they move into Golgi. There they are concentrated and modified as primary lysosomes.

Functions of lysosomes:

Lysosome will perform the following functions.

1) Digestion of large extracellular particles on the out side.

Liposomal enzymes will be discharged out side of the cell and digest the material present out side the cell.

2) Digestion In cell or intracellular digestion :

Lysosomes will digest the food that enters into the cell.

3) Cellular digestion :

The lysosome can digest the entire cell. It is called autolysis. Because of which De Duve called them suicidal bags of the cells. Autolysis is very important to the organisms.

Eg : The degeneration of tadpole tail in the fife history of frog is a result of autolysis.

4) Autophagy :

When the cell is in starvation the lysosome of a cell, will start the digesting the cell contents. This is called autophagy.

5) Sperm penetration :

During fertilization the acrosome of the sperm will produce lysosomal enzymes. They are useful to dissolve the tissue present around the ovum.

6) Chromosome Breaks :

Lysosome shows acid DNA ase it will break the chromosome and cause the rearrangement.

MITOCHONDRIA- DEFINITION-STRUCTURE- FUNCTION

noreply@blogger.com (amith) — Thu, 22 Dec 2016 11:54:00 +0000

MITOCHONDRIA STRUCTURE AND FUNCTIONS

DEFINITION OF MITOCHONDRIA: mitochondria are center for cellular respiration. It converts chemical energy into kinetic energy

Information About Mitochondria

1) In 1857 Kolliker observed mitochondria and called them as sarco-somes.

2) Flemming called them as Fila.

3) Altmann in 1890 called them as Bioplasts.

4) Benda gave the name mito-chondria.

5) Porter & Palade described their electron microscopic structure.

6) Mitochondria are present in all eukaryotic cells.

Size : The length varies from 1.5 to 10 microns. The smallest mitochondrion is seen in yeast. It is 1 mill micron in length. The width is .5 to .7 microns (Oocyte of amphibian show 20 to 40 microns length mitochondria.)

Shape: They are filamentous or they may show rod, spherical, or thread like structures.

Number: In Micro monas only one mitochondrion is present. In a liver cell 1000 to 1600 mitochondria are present. The highest number of mitochondria are seen in the cell of flight muscles. However cells of green plants contain less number of mitochondria. In red blood corpuscles of mammals and other higher animals mitochondria are absent.

Structure Of Mitochondria: The mitochondria is covered by 2 layers. It shows outer membrane and inner membrane. In each mitochondrion 2 chambers are present.

a) Outer chamber

b) Inner chamber.

Outer membrane: It is a continuous membrane which covers and protects the mitochondrion. !t separates the mitochondrion from the cytosol. It is permeable.

Inner membrane: It is projected in wards as a cristae. The membrane shows two faces. The outer face "C" face (Cytosol face) and inner face is called "M" face (Matrix face). On this M-face a number of knob like structures are present

Outer chamber: It is the space between outer and inner membranes. It is 60 to 80A°. It is filled with a fluid.

Inner chamber: It is called mitochondrial matrix. It is filled with jel like substance. It contains many enzyme systems. In 1963 "Nass" observed the presence of DNA molecule in the mitochondria

Variations of cristae: Normally the cristae are perpendicular but various arrangements can be noticed.

Parallel cristae : In the nerve cells, and cells of striated muscles the mitochondria will show parallel cristae.

Concentric cristae: In the spermatogonia of man the mitochondria will show concentric cristae.

Haphazard arrangement: In choas-choas the mitochondria will show irregular arrangement of cristae

Spherical cristae : In the spermatocytes the cristae are spherical.

Mitochondria without cristae: Very rarely the inner membrane is smooth. It will not show cristae.

Reduced cristae: In the cells of opossum testis the aristae are reduced in the mitochondria.

Chemical composition: Mitochondria contain 73% of proteins, 25 to 30% of lipids, 5% of RNA and small amount of DNA. The enzyme complexes are more. The lipids contain 90% phospholipids, cholesterol, carotenoids etc.

Enzymes : In 1969 Lehninger gave the account of enzymes in mitochondria.

1) Enzymes of the outer membrane of mitochondria

a) Mono mine oxidase enzyme.

b) Fatty acid activating enzymes.

2) Enzymes of the outer chamber of mitochondria

1) Adenylate kinase.

2) Neuckocyte diphosphokinase.

3) Enzymes of the inner membrane

In the inner membrane electron transport enzymes are present. They are cytochromes, flavor proteins, dehydroginases etc.

a) ATP synthetase oxidase.

b) Carnitine fatty acid acyltransferase etc., enzymes are present. Enzymes of matrix : These enzymes systems bebng to krebs cycle and fatty acid cycle.

a) Fumarase.

b) Aconitase.

c) Citrate synthatase etc

Elementary particles : On the inner membrane of the mitochondrion stalked particles are present. They are called F, or elementary ry particles. They are equidistantly placed. Each particle shows a stalk and head piece. The stalk is 50A° in length. The head is 100A° in diameter. The distance between 2 particles is 100A°. The head piece contains enzymes of ATP-ase system and bring oxidative phosphorelation. Hence they are called oxysomes.

Respiratory chains : Respiratory chain contains a series of complex proteins and electron carriers. These electron carriers are represented by 4 complexes.

Complex I : It contains flavo-protein of NADH dehydroginase. It contains non-haemiron which combine with protein. It receives hydrogen from NADH.

Complex II: It contains flavo-protein of succinic dehydrogenase. It receives hydrogen from succinic dehydroginase.

Complex III : It contains Cytochrome b1 , Cytochrome c_r

Complex IV: It contains Cytochome a_t Cytochrome a₃.

These complexes are connected by ubino-quinone. Cytochrome C will be present. Ubinoquinone connects complex 1,2 and 3. Cytochrome C will connect complex 384.

'Respiratory chain is proposed by 'Mochenan' and 'Green' and 'Baum'
in 1970. , '

Biogenesis of mitochondria: 1) Luck stated free existing mitochondria will elongate and divide and new mitochondria are formed.

2) Morrison stated mitochondria arise from either plasma membrane or endoplasmic reticulum.

3) In the cytoplasm small particles may-be present they are called promitochondria they may give rise to mitochondria.

Mitochondrial D.N.A.: Mitochondria contain one or two molecules of D.N.A. Mitochondrial D.N.A. is circular. It is highly twisted double strand molecule. "Rabino- with" stated that mitochondrial D.N.A. contains more G and C content thatunclear D.N.A. Moleculer weight of mitochondrial D.N.A is 9 to 11 millions. This D.N.A. has the capacity of multiplication. D.N.A. polymerase enzyme is present. This D.N.A. will produce R.N.A. It is believed that it may take up the production of some proteins.

Origin of mitochondria

Mitochondria semi auto nous or prokaryotic origin :

In 1890 'Akmann' suggested that mitochondria and chloroplasts may be intracellular parasites of the cells which have entered the cytoplasm of eukaryotic cell. And they live as symbotonts. Hence Akmann called them as Bioplats.

1) In Bacteria & Mitochondria electron transport system is present in plasma membrane and in inner membrane respectively.

2) Bacterial plasma membrane shows mesosomes, mitochondrial crystae can be compared with them.

3) Both bacteria & Mitochondria will show circular D.N.A.

4) In both bacteria and mitochondria ribosomes are reported.

5) Both bacteria and mitochondria will produce AT.P. and R.N.A. Hence we consider the mitochondria might have originated from bacterial

cell. In the cell mitochondria will function as semi-autonomous body.

Mitochondria Functions :

1) A.T.P. Synthesis : It is the power house of the cell. It brings oxidation of food. Hence Kreb's cycle reactions, electron transport system enzymes are located in mitochondria. By the oxidation of food energy is liberated in the form of A.T.P. (Oxidative phosphorelation takes place.)

2. Yolk formation: Mitochondria are responsible for the fcri soiydk in the developing ovum Granules are formed in the matrix They oeconie large masses Mitochondrion is converted into yolk storing body.

3. Mitochondrian sperm formation : When spermatid become? <pe'm mitochondria will form a spiral around the axial filament. This is called Neben-kem. It forms the middle piece of the sperm.

4. Origin of new system : It is believed that some of the ceil organelles may originate from mitochondria.

5. Heat production: In the oxidation of food ATP is released. Only 45% of the total energy is trapped in the form of ATP. The remaining 35% of ATP will come out as heat. (In birds and mammals this heat is useful for the maintenance of body temperature.).

6. ATP released during respiration (because of mitochondria ) will take part in many biosynthetic paths of the cell.

PLASMA MEMBRANE –CELL MEMBRANE- STRUCTURE -FUNCTIONS

noreply@blogger.com (amith) — Sun, 18 Dec 2016 10:57:00 +0000

CELL MEMBRANE- PLASMA MEMBRANE STRUCTURE -FUNCTIONS

The cytoplasm of the animal cell is bounded by a thin limiting membrane called "Cell membrane".

1) Nageli and Cramer called this membrane as cell membrane in 1855

2) In 1931 "Plowe" named this as plasmalemma.

3) Modem cell biologists prefer to call it plasma membrane (According to De Robertis).

4) Danielli & Davson in 1952 proposed molecular model of plasma membrane.

5) Robertson proposed unit membrane concept in 1960.

1) Material used for study of plasma membrane :

1) Human R.B.C. are kept in dilute solution (Hypotonic). Then it swells. It breakes and protoplasm will go out (Haemolysis). The remaining membrane is called Ghost. It is used for plasma membrane studies.

2) Liver cell or the membrane surrounding the nerve fibre are used as a material for the study of plasma membrane.

2) Physical nature of plasma membrane :

Danielli described the nature of plasma membrane. Robertson by using electron microscope and X-ray diffraction methods proposed the structure of plasma membrane. The plasma membrane shows 3 layers. (Trilaminar).

1) Outer layer is made by proteins....20 A°

2) Middle layer is bimolecular lipid layer....35A°

3) Inner layer is made by proteins ...20A°

3) Membrane model:

The membrane models are many. This model represents the molcular srganisation of the membrane.

a) Danielli Davsons model : It shows thin lipid layer with protein absorbed on both the sides. The lipid contains polar heads pointing out sides and ion poiar parts run transversly. In 1954 Danielli modified this model and gave a new model.

b) Robertson unit membrane concept: Robertson in 1959 described trilaminar structure of plasma membrane. It contains an outer and inner protein layers in between them a bimolecular lipid layer is present.

1) The unit membrane is 75A° thick.

2) The Outer and inner protein layers are 20A° thick.

3) In between them the lipid layer will show 35A° units.

4) The polar hydrophyllic ends of the lipid layer will face the proteins. Where as the hydrophobic ends of the lipids are away from the proteins.

c) Fluid Mosaic model: In 1972 "Singer" & "Nicholson" proposed this model.

1)Cell membrane is a mosaic of lipids and proteins.

2)Lipids are arranged in a bilayer way. It forms the structural frame work of plasma membrane.

3)Protein molecules are arranged in 2 ways.

1)Extrinsic proteins : These proteins are located adjacent to the outer and inner surfaces of the lipid layer.

2)Intrinsic proteins: These proteins will penetrate into the lipid layers partially or totally. They are called integral or intrinsic proteins.

This fluid mosaic model is accepted universally. The differential distribution of protein in the various regions of membrane is known as "Membrane asymmetry".

4) Chemical composition of plasma membrane :

Plasma membrane Shows proteins, lipids and small percent of carbohydrates.

a) Lipids:- The lipids of the plasma membrane are phospholipid, lecithin cholesterol glycolipids. the distribution of phospholipids in the bilayer of plasma membrane is highly asymmetrical The phospholipid will show 2 ends.

1) Hydrophobic end : It is water hating, non polar end.

2) Hydrophilic end : It is water loving part. It is called polar end. It is present near the proteins.

Hydrophobic end contains fatty acids and Hydrophilic end contains a phosphate group.

b) Proteins : The peripheral proteins or extrinsic proteins are free from lipids. They are loosely attached to the membrane. The integral proteins or intrinsic proteins will penetrate into the lipid layer. These proteins will give mechanical strength to the plasma membrane. They regulate cell activities.

c) Carbohydrates : Very small percentage of carbohydrates are present. Hexoses, Hexosamine, Fructose etc., are present. They may be attached to lipids glycolipids; and they are attached to proteins... Glycoproteins. These glycolipids and glycoproteins are present on the external surface.

d) Enzymes : More than 30 enzymes are isolated from plasma membrane. They are phosphotase, ATP ase, RNA ase etc.

5) Pores in plasma membrane : Plasma membrane shows some pores. The diameter is 35 Nm (nanometer). There are several models to describe the structure of pore.

1) Structural pore : These are permanent openings.

2) Dyanamic pores :They form during the intake of material.

3) Protein channel pores : These are small channels of specific proteins through which some ions can diffuse.

5) Modification of plasma membrane : To perform specialised functions plasma membrane will show some modifications.

6) They are

1) Microvilli.

2) Inter digitations.

3) Desomosomes, tight junctions etc.

a)Microvilli: In certain parts the plasma membrane will show minute infloldings they are called microvilli. They show -1 mili micron diameter and 6 milli micron length. In some cases the villi are connected with endoplasmic reticulum. These microvilli are more in intestinal mucosa cells. The microvilli show cytoplasm with micro filaments. The microvilli will increase the absorptive surface of the intestinal epithelium.

b) Inter digitations : At-some places the plasma membrane of adjacent cells will develop into finger like projections they are called inter digitations.

c) Desmosomes : The plasma membranes of adjacent cells become thicker in certain regions. On these thick areas fine, filaments are present. They are called tonbfilaments or tonofibrils. Such parts are called desmosomes. Desmosome is concerned with cell adhesion and maintenance of cell shape.

d) Terminal bar : It is a desmosome without tonofibrils. It is called terminal bar.

e) Zonula acculdens : These are special area of adjacent cells where the 2 plasma membranes fuse. These tight junctions are present below the apical boarder. It gives mechanical attachment between cells.

7) Properties of plasma membrane:

The substances which either enter the cell or leave the cell should pass through plasma membrane. The plasma membrane will' show permeability. It shows the following properties.

i) Osmosis : The diffusion of water molecular from low concentrated solution to high concentrated solution through plasma membrane is called osmosis.

ii) Passive transport: The movement of molecules from higher concentration to lower concentration without the expenditure of .energy, through plasma membrane is called passive transport.

a) Endocytosis: It is the process of by which large particles of food are engulfed. 1) Pinocytosis or cell drinking : Ingestion of liquid through plasma membrane is called pinocytosis.

b) Micro pinocytosis is observed at submicroscopic level. When a liquid come nearer to plasma membrane, it forms a vesicles. It is called pinoc : vesicle. After some time it is pinched off from the plasma membrane and becomes pinocytic vesicle in the cytoplasm

c) Phagocytosis: The process of taking solid food or solid material through the cell membrane into the cell is called phagocytosis. Phagocytosis means to eat. It is first discovered by "Metknikoff

d) Exocytosis: It is also called cell vomiting . The process of sending out products from the cell to the out side is called exocytosis or emeiocytosis.

e) iii) Active transport: If molecules or ions move against the concentrate gradient through plasma membrane, it is called active transport. For this energy is required. Now a days it is proved that carrier system is seen in the
plasma membrane and it is responsible for active transport.

8) Origin of plasma membrane :

1) It is believed that it develop de novo.
2) It is formed by the assembly of lipids & proteins.

3) It is believed that it develops from other membrane systems.

AN ANIMAL CELL-STRUCTURE

noreply@blogger.com (amith) — Sun, 27 Nov 2016 18:21:00 +0000

ANIMAL CELL-STRUCTURE-ORGANELLES

Cell is a fundamental, structural and functional unit of living organism. The science which deals with cells and their organelles is called cell-biology. The term cell was first used by Robert Hooke in 1665. He described the cell first as cella which means hollow space. Robert Hooke observed cells in the section of cork. In 1831 Robert Brown observed nucleus in plant cells. In 1858 Rudolf Virchow stated that new cells arise from pre-existing cells

"Omnis cellulae cellula. Schilden, German Botanist in 1938 described cell theory with regard to plant cell. T. Schwann German Zoologist in 1939 described cell theory with regard to animal cells. Cell theory denotes that "Cell is the structural and functional unit of life."

SHAPE OF CELL:

The shape of the cells is variable. The cells of unicellular forms, leucocytes and-bacteria, exhibit a number of shapes and those of multicellular organisms exhibit still further variation. Their shapes may be rounded, cylindrical, irregular, triangular and tubular.

SIZE OF CELLS:

Size is extremely variable, measuring from one micron to 175 mm. The ostrich egg cell is 176 mm. in diameter, thus visible to the naked eye. The nerve cell found in mammals may reach a length of 3 or 3.5 feet. Smaller cells are those of the Pleuropneumonia like organisms.

Plasma membrane:

A porous membrane surrounds the cytoplasm called plasma membrane. Electron microscopic studies reveal that the plasma membrane is composed of outer, inner protein layers and in between them double layered lipids are present Robertson called plasma membrane unit membrane.

The main function of plasma membrane is to regulate the entry and exist of substances.

cytoplasm :

The part of protoplasm outside the nucleus is known as cytoplasm. It is distinguished as an outer non-granular thick ectoplasm and inner granular thin endoplasm. In the cytoplasm many organelles are present.

Cell organells :

In the cytoplasm many cell organelles are present.

1.Centrosome :

It is the center of the cell discovered by van Benden in 1887. It is found near the nucleus and includes a specialised portion of cytoplasm, called centirosome. Its matrix is called as kinoplasm, in which two centrioles are embedded. Each centriole consists of nine fibrillar units and each fibrillar unit is found to contain three microtubules. The function of centrioles is to form the spindle at the time of cell division.

2.Endoplasmic reticulum :

In the cytoplasm a network of tubules are present. It is called endoplasmic reticulum. This network of tubules will be two types.

i. Smooth endoplasmic reticulum :

On the surface of the tubules ribosomes are absent. Hence they are ce Sled smooth endoplasmic reticulum or agranular endoplasmic reticulum.

ii. Rough endoplasmic reticulum :

On the surface of the tubules ribosomes are present. It is rough endoplasmic reticulum. This is called granular endoplasmic reticulum.

Endoplasmic reticulum will connect plasma-membrane nucleus and other organells.

Functions:

1. It gives strength to the cell and forms cytoskeleton.

2. Granular endoplasmic reticulum will produce proteins.

3. Agranular endoplasmic reticulum will produce lipids.

4. It forms the work bench for many biochemical reactions in the cell.

3.Ribosomes :

It is a small particle present in the cytoplasm. They will be attached to the cell organelles and they are also freely distributed in the cytoplasm.

In a Eukaryotic cell 80s ribosomes are present. This ribosome is made by 2 sub units. They are 40s, 60s sub units.

Ribosome is made by proteins and RNA. Ribosome shows 150 to 200A° diameter. Ribosome combine with m RNA and produce proteins. A group of ribosomes with m RNA is called polysome.

4.Golgi complex :

They are described by Golgi. They are also called dictyosomes, Bpochondria, and idosomes. The complex shows three types of structures,

a. Cisternae :

These are flat sacs. They are arranged one above the other. They are 150 V in length, 60 A° in thickness. b. Vacuoles :

These are oval in shape. They are big.

C. Vesicles:

They are in the form of groups. All these structures totally called Golgi complex. Functions :

They are more in secretory cells. Hence they are connected with secretory function. They store proteins and lipids. During cell division they produce cell, plate. During the formation of sperm they will form the acrosome of the sperm.

5.Mitochondria :

These are first described by Altamann as Bioplasts, in 1894. They were m i led as mitochondria by Benda in 1897.

They are filamentous or rod like structures. The mitochondria are covered by layers. Inner membrane is folded inside. Those folding's are called cristae. On these cristae oxysomes are present.

i)In the central matrix of mitochondria respiratory enzymes are present. The take up Krebs cycle reactions.

ii)In the inner membrane of mitochondria electron transport enzymes are present.

iii) Mitochondria helps in the oxidation of the food material and liberates
energy , Hence they are called power houses of cell.

iv) In the mitochondria a circular DNA is present. Hence mitochondria is also c. led semi autonomous body.

6. Lysosome :

These are described by De-Duve. Each lysosome is round in shape. It shows .4 to .8 microns in diameter. It is covered by lipoprotein layer. It contains hydrolytic enzymes. It is useful for intracellular digestion and autolysis of the cell.

Functions :

¹ i) Lysosome is helpful in the digestion of the food.

ii)At starvation lysosome will digest cell organelles.

iii)Lysosome can dissolve the cell. It is called suicide. Henc lysosomes are called suicidal bags of cells.

Inclusions of the cytoplasm:

In the cytoplasm vacuoles and duetoplasmic bodies are pr-sent. In the young stages vacuoles are absent in the cytoplasm. When the cell is growing the .Cytoplasm vacuoles are formed. In a older cell big vacuole is present. It is filled with cell sap. A vacuole is covered by tonoplast. In the cell sap water, some excretory substances, some pigments, and other substances are present.

Duetoplasmic bodies :

In the cytoplasm reserve food materials, excretory wastes a<\l secretory substances are stored. They are called duetoplasmic bodies.

Nucleus : -

In a eukaryotic cell a definite nucleus is present. It is 5 to 25 microns in, size. It shows the following parts.

a) Nuclear membrane :

Nucleus is covered by a nuclear membrane. It is made by 2 layers. In between the two layers perinuclear space is present. In the nuclear membrane small openings are present. Around each opening on the out side a small annulus is present.

Hammerling proved that nucleus is the seat of heredity through grafting experiments on Acetabularia.

b) Nucleoplasm :

Below the nuclear membrane nucleoplasm is present. In this glycoproteins, RNA and enzymes are present.

c) Chromatin network :

In the nuclear spa many chromosomes are present. They are thin and filamentous. They are in the form of a network. On the chromosomes genes are present. They are units of heredity.

d) Nucleolus :

In the nucleoplasm one or two round structures are present They are called nucleoli. They contain proteins and RNA. They produce ribosomes.

Functions:

1. It is the seat of life in the cell.

2. It carries hereditary characters from one generation to another generation.

3. It produces nucleic acids.

PROKARYOTIC CELL- EUKARYOTIC CELL- DIFFERENCES

noreply@blogger.com (amith) — Wed, 16 Nov 2016 19:31:00 +0000

Differences between Prokaryotic Cell and Eukaryotic Cell

Feature		Prokaryotic cell	Eukaryotic cell
1.	Nuclear envelope	absent	present
2.	DN A '	single, circular and naked	more than one and combined with proteins
3.	Chromosome	single	multiple
4.	Nucleolus	absent	present
5.	Division	amrtosis	mitosis or meiosis
6.	Ribosomes	70S(50S+30S scattered in cytoplasm	80S(60S+40S) Found attached to ER or free in cytoplasm.
7.	Endo membranes	absent	present
8.	Mitochondria	absent	present
9.	Chloroplasts	absent	present in plant cells, absent in animal cell
10.	Lysosomes	absent	present
11.	Peroxisomes	absent	present
12.	Cytoskeleton	absent	present
13.	Cell wall	non-cellulose	cellulose only in plants cells
14.	Respiratory enzymes	located in plasma membrane	enclosed in mitochondria.

PROKARYOTIC CELL -STRUCTURE

noreply@blogger.com (amith) — Wed, 16 Nov 2016 19:20:00 +0000

BASIC STRUCTURE OF A PROKARYOTIC CELL

The cells which lack true nuclear membrane are called prokaryotic cells. Blue green algae, bacteria are the examples for prokaryotic cells.

Prokaryotic cells lack chloroplasts mitochondria, Golgi complex and endoplasmic reticulum

Prokaryotic cells are simple and primitive cells.

1) In blue green algae cell shows a cell wall, enclosing protoplasm. In the protoplasm the peripheral coloured part is the chromateplasm and the central colorless part is the centroplasm. In the centroplasm there is DNA as the genetic material.

2) Bacterial cell consists of a rigid cell enclosing protoplasm. The rigid cell is surrounded by slime layer or capsule. The protoplasm shows a peripheral plasma membrane which is often producing coiled mesosomes to carry respiration. The central part of the cell shows a long coiled thread like DNA. Protoplasm contains many ribosomes, fat bodies, volutin granules etc. The cells also show pili and flagella.

CELL BIOLOOY-INTRODUCTION (brief history of cytology)

noreply@blogger.com (amith) — Wed, 16 Nov 2016 19:01:00 +0000

Cell biology (Gr., kytos-hollow vessel or cell, logos-to discourse) is a biological science which deals with the study of cells. The cell itself can be regarded as the vital unit of organisms.

'Aristotle' and 'Paracelsus' concluded that "all animals and plants, however, complicated are constituted by few elements which are repeated in each one of them."

The beginning of cell biology dates back to the 15th century, when 'Da Vinci in 1485 has stressed upon the use of lenses in viewing small objects. In 1658, 'Jan Swammerdam' gave the first description of the cell in his account of the red blood cells of the frog. The cytology came in its actual existence with the discovery of cell in 1665, by "Robert Hooke", while examining a thin slice of cork under his crude compound microscope, Hooke observed its honey-combed structure. He gave them the name "cells" (cellulae -little room).

Malphighi' studied a variety of animal tissues microscopically and therefore, he is generally considered as the father of 'microscopic anatomy '.

'A.V.Leeuwen hoek (1632-1723) discovered the animalcules, infusoria (Protozoa), bacteria, etc., and made microscopical observations on protozoa, ants, aphids, spermatozoa, red blood cells etc.

The cell theory was proposed by two German biologists'M.J.Schleiden' (1804-1881), and Theodor Schwann' (1810-1882) independently in 1838 and 1839, respectively. The cell theory holds that the animals and plants have same pattern of organization and construction. The bodies of both animals and plants are composed of cells and that each cell can act independently. In words of 'Schwann' and 'Schleiden' cell is "functional biological unit'.'

"Rudolf Virchow" in 1885 stated, "where a cell exists there must have been a pre-existing cell, just as the animal arises only from an animal and the plants only from a plant".

"Purkinje" in 1840 coined the term protoplasm. The protoplasm was first of all observed by "Corti" (1772) and the French Zoologist 'Dujardin' (1835) called it sarcode.

"Huxley" in 1868 referred to protoplasm as the "physical basis of life".

The protoplasm theory states that all living matter of animals and plants is protoplasm. The part of the protoplasm which occurs between the plasma membrane and nucleus is named as cytoplasm.

20th century brought many modern micro techniques. New histo chemical and cyto chemical methods have been developed to detect various molecular components of the cell. Different biochemical events of the cell could be known by autoradiography. Methods of tissue culturing have made possible the study of living cells.

Year	Names of contributor	Cytological contribution
1824	R.J.H. Dutrochet	Showed that all animals and plants composed of cells.
1826	Turpin	Reported the occurrence of cell division.
1831	R. Brown	Described the nucleus
1835	Felix Dujardin	Described protoplasm as ("Sarcode")
1838	M.J.Schleiden	Proposed "Cell theory"
1839	T.Schwann	Applied "Cell theory" to animals.
1840	J.E. Purkinje	Named the cell contents as Protoplasm.
1855	R.Virchow	Stated that all cells arise from pre-existing cell.
1857	Kollieker	Discovered mitochondrian
1863	Waldeyer	Chromosomes of cell
1871	F. Miescher	discovered nucleo-protein and nucleic acid.

1882	Strasburger	described mitosis in plant cells
1887	E.Van Benden	discovered centrioles.
1888	T.Boweri	described the centrioles.
1888	Waldeyer	Introduced the term chromosome.
1902	W.S.Sutton	Proposed "the chromosome theory" heredity.
1905	J.B.Farmer along with J.E.Moore.	Coined the term meiosis
1943	A.Claude	Isolated cell components like ribosomes, mitochondria and nuclei
1952	C. Du Duve	Identified hysosomes.
1953	J.D.Watson and F.H.C. Crick	Proposed the double helixmodel for the DNA molecule.

1959	S.Ochoa	Synthesis of polyribonuclotide in vitro.
1959	A.Kornberg	Synthesis of polydeoxiri-
1968	M.W.Nirenberg and H.G.Khorana.	Triplet genetic code.
1968	R.H.HoIley	discovery of base sequence of RNA

BALANOGLOSSUS-AFFINITIES-PHYLOGENITC RELATIONS

noreply@blogger.com (amith) — Tue, 19 Jan 2016 07:07:00 +0000

BALANOGLOSSUS-SYSTEMATIC POSITION IN THE ANIMAL KINGDOM

Hemichordates show non-chordate and chordate features. These animals show more non-chordate hence Hyman objected its inclusion in the phylum chordata. Bateson included it in the phylum chordata.

1. Gegenbaen kept Balanoglossus in Enteropneusta group.

2. Sedgewick and Huxley described its chordate nature.

3. 1887 Bateson kept this in pnyl um chordate.

I. Affinities with Annelida: Spengel stated that Balanoglossus resembles annelids more,

(a) Resemblences :

1. Presence of worm like-body.

2. Presence of burrowing or tubicolous habit.

3. Presence of dorsal heart.

4. Presence of similar blood vascular system in both groups.

5. Presence of ventral nerve cord.

6. Tornaria resembles trochophore larva of annelids,

(b) Differences :

1. Presence of dorsal tubular nerve cord.

2. Presence of gills in the pharynx.

3. Absence of Nephridia in tornaria larva.

4. Presence of stomochord.

5. Development differs from anneliden development.

II. Affinities with Echinodermata :

(a) Resemblences :

1) Presence of enterocoelic coelome.

2) Presence of heart in Balanoglossus is homologus to dorsal sinus of echinoderms. "S”

3) Presence of poorly developed nervous system.

4) Presence of creatin a muscular phosphogen.

5) Tornaria resembles Bipinnaria of echinoderm.

Serological tests and biochemical tests proved that both groups are closely related.

(b) Differences :

1) Bipinnaria will not show apical tuft of cilia which is seen in tornaria.

2) Echinoderms show radial symmetry whereas Balanoglossus will show bilateral symmetry.

3) Echinoderms will show water vascular system where as it is absent in Balanoglossus

III. Affinities with Nemertines :

(a) Resemblences:

1) Presence of worm like appearance.

2) Presence of ciliary mode of feeding.

3) Presence of burrowing life.

4) Presence of segmental arrangement of gonads.

(b) Differences :

1) Balanoglossus contains dorsal tubular nerve corel, it is absent in nemer-
tines.

2) Lateral nerves are present in hemertines they are absent in Balanoglossus
IV. Affinities with chordates :

a) Resemblences :

1) Presence of notochord.

2) Presence of dorsal tubular nerve cord.

3) Presence of pharyngeal gills.

4) The structure of pharynx resemble in both groups.

5) Presence of entero coelic coelom.

b) Differences :

1) The stomochord of Balanoglossus should not be compared with the notochord. Stomochord is present only in the proboscis. It is not covered by sheaths. It is hoilow. It will not give strength hence it should not be called notochord.

2} Balanoglossus will show ventral nerve cord.

3) Balanoglossus dorsal nerve cord is hollow in the collar region only.

4) In Balanoglossus the gills are present towards dorsal side, but in chordales
they are lateral in pwsitia. Thus Balanoglossus differs from chordata.

Conclusion : ,

1. Most probably Hemichordates and chordates might have evolved from
the same ancestor.

2. Newman kept thisgroup in between echinodermate and chordate.

3. Hyman considered them as invertebrates.

We can consider this as primitive chordate group.

HEMICHORDATE CHARACTERS -CLASSIFICATION

noreply@blogger.com (amith) — Tue, 19 Jan 2016 06:55:00 +0000

HEMICHORDATES -GENERAL CHARACTERS- CLASSIFICATION

Balfour classified urochordata, cephalochordata and vertebrata as phylum chordata. But Bateson included Hemichordata in this phylum chordata. These members are considered as primitive chordata.

1. The body of these animals is long and worm like.

2. These are marine animals. They make burrows in the coastal sandy shores.

3. Their body is divisible into proboscis, collar and trunk.

4. They emit strong idoform smell.

5. Their body is covered by ciliated epidermis.

6. Their body wall is muscular.

7. They show enterocoeliccofelome. This coelome is divided into 5 cavities, one in the proboscis, two in the collar and two in the trunk region.

8. In the proboscis buccal diverticulum is present. It is called stctnochord. It is comparable to notochord.

9. In these animals excretory organs are absent. In the proboscis glomerulus is present. It will help in excretion.

10. Digestive system is well developed. The alimentary canal is long. It starts with mouth and ends with anus. Pharynx is useful for food collection and respiration. These are filter feeders.

11. On the lateral sides of Pharynx gill slits are present.

12. Blood vascular system resembles annelids, blood vascular system more.

13. Heart and Pericardium are present in the proboscis.

14. In the collar lateral blood vessels are present.

15. Nervous system includes a dorsal tubular nerve cord and solid ventral nerve cord.

16. These animals will not show brain and cranium. Hence this is grouped aeraniata.

17. These are unisexual animals gonads will give gonoducts.

18. Fertilization is external.

19. Holoblastic clevage is seen.

20. In the life history a larval form is seen. Tornaria larva is usually seen.

Classification :

Hemichordata subphyllum is classified into two classes.

1. Enteropneusta

2. Pterobranchia

Class 1 : Enteropneusta :

1. These animals are worm like and cylindrical.

2. They are burrowing animals.

3. They show many pairs of gills.

4. Alimentary canal is long and straight. Ex : Balanoglossus, Ptychodera.

Class: 2 : Pterobranchia :

1. They lead sedentary life.

2. They are tubicolous.

3. They are colonial organisms.

4. They show less number of gills.

5. Alimentary canal is 'U' shaped.

Ex : 1. Cephalodiscus

2. Rhabdopleura.

BALANOGLOSSUS -REPRODUCTIVE SYSTEM, AND EMBRYO DEVELOPMENT

noreply@blogger.com (amith) — Tue, 19 Jan 2016 06:45:00 +0000

BALANOGLOSSUS-REPRODUCTION

Balanoglossus performs asexual and sexual reproduction

Asexual reproduction: Gilchrist described asexual reproduction in Balanoglossus capsensis. In the summer season its posterior end will divide into a number of bits. Each bit will develop into a new individual.

Sexual Reproduction : Sexes are separate, sexual dimorphism is absent. The gonads are simple. They are present in one or many rows in the branchio-genital region.

Each gonad will give gonoduct. This gonoduct will open out through a pore externally. In male the gonads are called testes. They produce sperms. In female the gonads are called ovaries. They produce ova. They are liberated into water. Fertilization will take place in water. It is called external fertilization.

The fertilized zygote will undergo holoblastic clevage.

1. In Balanoglossus kowaiowsley the development is direct. No larval form is seen in its life history.

2. In other species of Balanoglossus a larval form called 'Tonaria" is seen in the development. It Will undergo metamorphosis and becomes adult.

Development:

1. The fertilized egg contain some yolk. It is meselecithal egg.

2. It undergoes holoblastic clevage.

3. Because of clevage it gives Morula, blastula stages.

4. In Blastula stage a cavity is present called Blasto coel.

5. The blastula is round in the beginning then it becomes flat.

6. It undergoes invagination and gives two layered gastrula.

7. This stage will show blastopore, which will slowly closer.

8. This stage will develop cilia.

9. It will also develop apical tuft.

10. It shows ectoderm and endoderm.

11. It will develop enterocociic coelom.

12. At this stage the ciliated embryo will be liberated into water. It elongates
and transforms into Tornaria" larva.

Tornaria larva:

1. Mulier proposed the name Tornaria". He considered it as Fxhinoderm larva.

2. Metacoff first identified it as the larva of Balanoglossus

3. This larva free swims in the sea water.

4. It is oval in shape.

5. It is transparent.

6. Its ciliary bands are pre-oral and post-oral ciliated bands.

7. It shows distinct digestive tract. It opens with mouth on the ventral side. At the posterior end it opens out through anus. This tract is curved.

8. It will swim with the help of cilia.

a) Pre oral band of cilia is significant one. It surrounds the mouth and then it transforms as post oral band of cilia.

b) Around anus a band of cilia is present called anal ciliated band.

9. Tornaria takes micro-organisms of sea water as food.

10. It shows two eye spots and nerve cells.

11. It can notice the light intensity with the help of eye spots.

This larva after leading a free swimming lobe for some time it will transform into adult. It is called metamorphosis.

Metamorphosis:

1. Eye spots and ciliated bands will slowly reduce.

2. By the development of two constrictions in the body, it is divisible into 3 parts.

a. anterior part proboscis

b. Middle part collar

c. Posterior part trunk

3. Trunk will grow quickly more than proboscis and collar.

4. In the pharynx gills are developed.

5. In the intestinal region hepatic caecae are developed.

6. Stomochord, Pygochord etc. will be developed.

7. Heart, blood vessels, and glonurukis are developed.

8. Coelom will be divided into 5 cavities.

9. From ectoderm nervous system is developed.

Thus slowly the tornaria will transform into adult. It will sink into the water. It will lead burrowing life.

BALANOGLOSSUS-CIRCULATORY SYSTEM

noreply@blogger.com (amith) — Tue, 19 Jan 2016 06:32:00 +0000

BLOOD VASCULAR SYSTEM IN BALANOGLOSSUS

Balanoglossus will show open type of blood vascularsystem. It shows

1. Blood

2. Dorsal sinus

3. Heart

4. Afferent vessel

5. Distributing vessels

6. Collecting vessels.

1. Blood: It is in liquid form. It is colourless. It has no haemoglobin. It contains few blood cells.

2. Dorsal sinus : In the proboscis above the buccal diverticulum a dorsal sinus is present. In this biood flows from posterior end to anterior end. It gets blood from collecting blood vessels. At the antei ior end it will push the blood into afferent blood vessel.

3. Heart: It present above the dorsal sinus. It is triangular in shape. It shows contractions and relaxation. This brings movement in dorsal sinus.

4. Afferent blood vessel : From anterior end of Dorsal sinus afferent
blood vessels will arise. They unite to form a plexues. This is called glomerulus.
This works as a excretory organ.

5. Distributing vessels: From glomerulus blood will enter into 4 blood
vessels.

1 Mid dorsal proboscis artery hill supply blood to proboscis parts.

2. Mid Ventral Proboscis artery supplies blood to ventral side

3. Two afferent glomerular arteries wilffravel backwards and unite to form ventral artery.

Ventral artery: It is muscular. It travels to the end of trunk. Blood flows backwards in this blood vessel. This gives the following blood vessels.

a) Ventral collar blood vessel

b) Ring blood vessel in collar

c) Afferent branchial vessel carry blood to gills of pharynx.

6. Collecting.blood vessels : It travels on the dorsal side. It is muscular.
It will collect blood from all body parts. This vessel will supply blood to the dorsal
sinus.

Thus blood flows in the blood vascular system.

BALANOGLOSSUS- RESPIRATION

noreply@blogger.com (amith) — Tue, 19 Jan 2016 06:20:00 +0000

RESPIRATION MECHANISM IN BALANOGLOSSUS

Balanoglossus lives in burrows in the intertidal sandy areas.
Its body is long cylindrical.
In its pharynx 'U' shaped gills are present with increase in its age the number of gills will increase in number.
Each gill has two lobes.
These two lobes are separated by tongue bar. This tongue bar is hollow.
It contains coelom.
Each gill opens into pharynx.
Near by gills are separated by septa are present.
Gill is supported by gill bar.
These gill bars are primary and secondary.
They are transversely connected by synaptaculae.
The gills are supplied with blood capillaries.
These gills open out through gill slits.
The water from pharynx will enter into the gills.
Oxygen present in this water will diffuse into the blood of blood capillaries present in the walls of gills like that C0₂ from blood will diffuse into the water.
Thus branchial respiration is carried on in Balanoglossus.

BALANOGLOSSUS-DIGESTIVE SYSTEM

noreply@blogger.com (amith) — Mon, 18 Jan 2016 17:06:00 +0000

DIGESTIVE SYSTEM OF BALANOGLOSSUS

Balanoglossus is a worm like chordate animal. It is cylindrical organism and lives in burrows of the sand. This animal shows a long alimentary canal and associated glands. This is called digestive system. The alimentary canal starts as mouth and ends with anus.

1. Mouth : It is present on the ventral side of the body between proboscis and collar. It is a permanent pore.

Recent investigations proved that this animal can open or close its mouth.

2. Buccal cavity: Mouth leads into buccal cavity. It is present in the Collar region. This will extend into the proboscis as stomochord.

3. Pharynx : Buccal cavity will lead into pharynx. It is present in the branchio - genital region of the trunk. This can be divisible into dorsal respiratory chamber and ventral food collecting chamber. The food collecting chamber is covered by ciliated glandular epithelium. This part will concentrate the food organisms present in the water that enters into this chamber, in the dorsal respiratory chamber gills are present. They are useful to perform respiration and send out water through the openings of gill on the body wall.

4 .Oesophagus: Pharynx will lead into the oesophagus. It is a very smallpart in the alimentary canal.

5. Intestine : It is a long straight tube. It travels all along the trunk and it is divisible into 2 parts

i) the first part containing hepatic caecae.

ii)the second part will not contain hepatic caecae.

6. Anus : At the tip of the trunk the alimentary canal will end as Anus.

Food : The food of Balanoglossus is small micro-organisms and small organic particles present in water.

Feeding : Balanoglossus shows ciliary mode of feeding or it is a niter feeder.

By the movement of cilia of the gills water is brought into the pharynx. The food is collected in the pharynx and pushed into oesophagus and then into intestine. The water is sent out through gills.

Digestion : The glandular cells of the pharynx, intestine will produce digestive juices. The hepatic caecae will also produce digestive juices. They will digest the food in the intestine.

The digested food is absorbed by the blood through intestine wall and is utilized.

Egestion : The undigested food along with sand will be sent out through the anus.

BALANOGLOSSUS-ANATOMY-BODY WALL

noreply@blogger.com (amith) — Mon, 18 Jan 2016 16:54:00 +0000

BALANOGLOSSUS -INTERNAL STRUCTURES AND BODY WALL

Balanoglossus is a long cylindrical worm like hemichordate animal. It lives in burrows in the sand of intertidal region.

It's body wall is smooth. It is soft, moist and slimy. It is ciliated. This body wall is helpful in locomotion.

The body wall of Balanoglossus will show epidermis, muscles and peritonium.

1. Epidermis : It is made by a single row of cells. These cells are long and columner. They are ciliated. Some cells are gland cells. Some cells are connected with nerve ends and form receptors. They receive sensory stimule.

2. Muscle layer : Below the epidermis muscle layer is present.

i) In the proboscis and collar region circular muscles are on the outerside and longitudinal muscles are towards the innerside.

ii)In the trunk region only longitudinal muscle layer is present.

3. Peritonium : The innermost layer of body wall is called peritonium. It is a thin layer. It is derived from mesoderm.

Functions of Body wall :,

1. It will cover and protect the body organs.

2. It will secrete slime which helps the animal to move in the burrows.

3. It will absorb the external stimule.

4. It will help in locomotion.

Coelom: The coelom of this animal is divided into 5 cavities. It is derived in enterocoelic way.

1. Proboscis coelom : It is a single cavity. It opens out through a pore on the proboscis. It is filled with coelomic fluid. It helps in burrowing.

2. Collar coelom : In this region coelom is represented by two cavities. In this region coelomic cavity is reduced because of the high muscular development. This coelomic cavities will open into first gill slit.

3. Trunk coelom: In the trunk region two coelomic cavities are present. In these cavities gills, gonads, hepatic caecae etc. are placed.

Skeletal structure of Balanoglossus :

In Balanoglossus different skeletal structures are present. They are

1. Stomochord : It is present in the proboscis. It gives strength to proboscis. It is formed as an extension of Buccal epithelium. This stomochord includes a central cavity. It is considered as a homologous organ with notochord of chor'dales.

2. Branchial skeleton : The gill pouches are supported by chitinous structures. They are primary gill bars and secondary gill bars.

3. Pygochord : On the ventral sideof the gut a longitudinal pygochord is present. Its function is not clearly known.

BALANOGLOSSUS-EXTERNAL MORPHOLOGY

noreply@blogger.com (amith) — Mon, 18 Jan 2016 16:39:00 +0000

BALANOGLOSSUS.-HABIT, HABITAT-EXTERNAL CHARACTERS

Balanoglossus is a worm like Protochordate organism. It belongs to

Phylum: Chordata
Subphylum: Hemichordata
Order: Enteropneusta.

Habit and Habitat: It lives in burrows in the sand of intertidal regions of sea water. It lives in 'IT shaped tubes. These tubes will open on both ends.

Shape : It resembles earthworm. Its body is long worm like, it is cylindrical. This animal is called Acorn Worm. It is called tongue worm.

Size : It is 3 cm. to 2 meter in length. Balanoglossus gigas will grow to 2 meters in length.

Colour: Different species of this genus will show different colours. They may be light brown or yellow or light red in colour.

Smell : They give strong smell resembling idoform smell.

Divisions of the Body : The body is bng and is divided into 3 parts.

1. Proboscis

2. Collar

3. Trunk

Proboscis: It is club shaped structure. It is at the anterior end of the body. Its body wall is muscular. It encloses a coelomic cavity called proboscis coebme. In this proboscis stomochord, Heart, pericardium and glomerulus are present.

The posterior end of proboscis is called neck. It connects proboscis with collar. Below this neck a pre-oral ciliated structure is present. It will test the water and food that enters into the mouth.

Collar : It is the middle part. It is a short part. In between collar and proboscis ventrally a big mouth is present. It is permanent opening. Collar contains two coelomic cavities.

Trunk : It is an elongated, posterior part-The body wall is folded hence it gives wrinkled appearance to the body. This trunk is divided into 3 parts.

a) Branchio-genital region

b) Hepatic region

c) Candal region

a) Branchio genital region : This is the first part of the trunk. It includes gills and gonads hence it is called branchio-genital region.

b) Hepatic region: In this part hepatic caecae are seen hence it is called Hepatic region.

c) Candal region : This is the posterior part of the body. At its tip anus is present.

The body of this animal is covered by ciliated epidermis.

This animal will make burrows in the sand with the help of proboscis and collar.

ECHINODERMATA WATER VASCULAR SYSTEM

noreply@blogger.com (amith) — Fri, 08 Jan 2016 17:53:00 +0000

WATER VASCULAR SYSTEM-AMBULACRAL SYSTEM IN DIFFERENT ECHINODERMS

Water vascular system (or) Ambulacral system is a peculiar system which is seen in only Echinoderms. This system is modified in different ways in the members belonging to different classes of phylum echinodermata.

The water vascular system in Asteroidea is considered as typical system.

1. Water vascular system in Asteroidea :

vie water : water vascular system in star fish

2. Water vascular system in Echinoidea : Water vascular system of
Echinoidea will resemble the typical water vascular system of Star fish.

1) On the aboral side Madreporite is present.

2) Madreporite is connected to ring canal by 'S shaped stone canal.

3) Around the pharynx ring canal is present. It is placed above the aristotle lantren.

4) From ring canal 5 radial canals will arise. They end as tentacles at the end of each arm.

5) From radial canals lateral canals will arise. These lateral canals will end as tube feet.

6) Each tube foot shows ampulla, podium and sucker.

7) At the five inter radii of the ring canal five polian vesicles are present. They produce amoebpcytes.

8) Tiedmann's bodies are absent.

3. Water Vascular System in Holothuroidea : The members of this
class are called sea-cucumbers.

1) Madreporite hangs into the body cavity.

2) From madreporite stone canal will reach the ring canal. One or many ring canals may be present.

3) The ring canal is present around the oesophagus.

4) From ring canal 5 radial canals will arise. They travel to the oral region give branches to tentacles. Then they travel aborally.

5) From each radial canal lateral canals will arise.

6) Each lateral canal will end with tube foot.

7) Tube foot has no sucker.

8) From ring canal 10 to 50 polian vesicles will hang into the body cavity.

4. Water vascular system in Crinoidea: This class includes sea lilies.
They are sedentary animals.

1) Madreporite is absent.

2) Ring canal is present around mouth.

3) From ring canal 5 radial canals will arise. Each radial canal will divide into two. Thus 10 radial canals will travel into 10 arms.

4) From radial canals lateral canals will arise.'

5) Each lateral canal gives tube foot.

6) Tube foot will not show ampulla and sucker. Hence they are useful as tactile sense organs and for respiration.

5. Water vascular system in Ophuroidea :

Brittle stars are included in this class.

1) Madreporite is present on the oral surface.

2) Stone canal will connect madreporite vctth ring canal.

3) Ring canal is present around the mouth.

4) From ring canal 5 radial canals will arise.

5) Each radial canal will give lateral canals.

6) Each lateral canal ends in tube foot.

7) Tube foot has no ampulla and sucker. Hence they are useful for respiration and work as tactile sense organs.

8) At the 4 inter radii 4 polian vesicles are present. Tiedmann bodies are absent.

Thus water vascular system is modified in different classes of Echinodermata.

ECHINODERMATA CHAHACTERS- CLASSIFICATION

noreply@blogger.com (amith) — Fri, 08 Jan 2016 17:33:00 +0000

ECHINODERMATA GENERAL CHARACTERS AND CLASSIFICATION

Echinodermata means spiny skinned animals. This name was first proposed by Jacob Kelin (1734) for echi-noids. It was Leuckert (1847) who first established Echinodermata as a distinct group of the animal kingdom.

1) They are exclusively marine.

2) They are free living. Some are pelagic. Some are creeping on the sea bottom.

3) These are all triploblastic and co-elomate animals.

4) Adults show pentaradial symmetry and larval form show bilateral symmetry.

5) The size varies from moderate to considerable size.

6) Shape of the body is spherical or globular or elongated. It shows oral aboral and sides.

7) Exo and endo skeletons will be present.

8) Endo-skeletoh is mesodermal. It is made by hard polygonal plants.

9) Body walls include only Epidermis, dermis and peritonium.

10) Body cavity or coelome is large. It is an entero-coelome. It is lined by
ciliated peritonium.

11) Respiration is carried on by

a) Papullae-Star fish.

b) Peristomial gills - Sea urchin.

c) Genital bursae - Brittle star.

d) Respiratory trees - Holothurians.

12) Excretory organs are absent.

13) Nervous system is primitive. Brain is absent.

14) Special sense organs are poorly developed. Eye spots and statocysts are present.

15) Reproduction is sexual. Sexes are separate. Sexual dimorphism is absent. Gonads are iarge.

16) Gametes are iiberated into the water. Fertilisation is external.

17) Eggs are homolethial. Cleavage is radial and indeterminate type.

18) Life history includes larval stage.

19) They can show autotomy and regeneration.

Classification of Echinodermata:

The classification followed here is based on Hyman's Classification.

SUB PHYLUM I : PELMATOZOA : Mostly extinct echinoderms. Mouth and anal.aperture present on the oral surface. Tube feet are primarily food catching. They do not show suckers, pelmatozoa has only one living class.

Class : Crinoidia: Extinct and living forms. Living members are with stalk. Oral surface is directed upwards. Mouth is usually central. Anus is usually excentric. They are present on the oral surface. Arms movable, simple mostly branched, usually five or ten in number. Madreporite, spines and pedicellariae are present. Larva is doliolaria.

Order : Articulata : Mouth and ambulacra! grooves remain exposed.

Ex : Antedon, Metacrinus.

SUB PHYLUM D : ELEUTHEROZOA : Mostly living echinoderms. Stem or stalk is absent. They are living forms. Body structure is usually pentamerous. Oral surface has mouth. It is downwards. Anus usually on the aboral surface.

Class 1 : Holothuroidea : Body bilaterally symmetrical, usually elongated in the oral aboral axis having mouth at or near one end and anus or near the other end.

Order 1: Aspidochirota : A pair of well developed respiratory trees is present.

Ex: Holothuria.

Order 2 : Elaslpoda : Many tube feet. Mouth is usually ventral and surrounded by 10-20 branched tentacles: Ex: Elphidia.

Order 3 : Dendrochlrota : Tube feet are numerous. Oral tentacles are dendritic or branched like tree branches. Respiratory trees are present. Ex : Thyone, Cucumaria.

Order 4: Molpadonia : Tube feet are absent. Oral tentacles are digitate or finger shaped.

Ex : Molpadia.

Order 5: Apoda: Body vermiform having smooth or watry surface. Tube feet are absent. Oral tentacles are 10-20, simple, digitate or pinnate. Ex : Synapta.

Class 2 : Echinodea : Body is spherical, disc like, oval or heart shaped. Body is enclosed in an endoskeletal shell or test of closely fitted calcareous plates covered with movable spines. Ambulacral grooves are absent. Pedicellariae are stalked and three jawed. Sexes are separate. Larval form is echinopluteus larva.

Subclass 1: Regularla : Body is gbbular, mostly circular and sometimes oval in shape. Symmetry is pentamerous. Aristotle's lantern is well developed.

Order 1: Lepidocentroida :

Ex : Poormosoma.

Order 2 : Cidaroidea :

Ex : Cidaris, Notocidaris.

Order 3 r Auhdonta :

Ex.: Diodema, Astropyga.

Order 4 : Camarodonta ;

Ex : Echinus, Strongylocentrotus.

Subclass 2 : Irregularia : Test is mostly flattened oval to circular. Symmetry is bilateral. Mouth centrally placed on the oral surface. '

Order 1 : Clypeatrolda : Aristotle's lantern is present. Gills are absent. Ex : Clypeaster.'

Order 2 : Spatangoida : Test is oval or heart shaped, Gills absent. Ex : Lovenia, Echinocardium.

Class 3: Asteroidea : Body is flat, pentagonal or star shaped. Oral and aboral surfaces are distinct. Sexes separate, gonads radially arranged. Development includes bipinnaria or brachiolaria larva..

Order 1; Phanerozonia: Arms are provided with two rows of conspicuous marginal plates. Pedicellariae are alveolar or sessile type. Tube feet are arranged in two rows.

Ex : Astropecten.

Order 2: Spinulosa : Arms are generally without conspicuous marginal plates. Pedicellariae are rarely present. Ex : Astorina, Echinaster.

Order 3: Forcipulata : Podia or tube feet are arranged in four rows and provided with suckers. Papulae are on both surfaces. Mouth frame is of ambulacral type.

Ex: Asterias.

Clsss 4 : Ophiuroidea : Body is flattened with a pentamerous or rounded central disc. Oral and aboral surfaces are distinct. Arms usually five, rarely six or seven, are long and slender. Ambulacral grooves are absent. Madreporite is on the oral surface. Sexes are separate.

Order 1 : Ophiurae : Arms are simple, mostly five in number.

Ex : Ophioderma, Ophiothrix.

Order 2 : Euryalae ; Arms are simple or branched. Disc and arms are without or poorly developed. One madreporite in each inter radius. Ex : Astrophyton, Astroporpa.

ECHINODERMATA LARVAE

noreply@blogger.com (amith) — Fri, 08 Jan 2016 09:23:00 +0000

Echinodermata larval forms

Echinoderms are unisexual animals. Sexual dimorphism is absent. Fertilisation takes place in water. The development may be direct or indirect. If the development is indirect it includes larva stages. In different classes of echinoderms, different types of larvae complete the development. The larval form is bilaterally symmetrical. It undergoes metamorphosis and radial symmetrical adult is developed.

Class of Phylum Echinodermata

Larval form

1. Asteriodea

2. Ophiuroidea

3. Echinoidea

4. Hobturoidea

5. Crinoidea

Bipinnaria & Brachiolaria

Ophiopkiteus

Echinopkrteus

Auricularia

Dobolaria & Pentacrinoid

1. Bipinnaria larva :

It is the larva form seen in the life history of Star fish. The fertilised egg is homolecithal. ft undergoes hobblastic cleavage and devebps into blastula and gastrula stages. The gastrula elongates in length and it gives rise to Bipinnaria larva.

1. It is a bilaterally symmetrical free swimming pelagic larva.

2. The pre-oral region is elongated. Post-oral region is broad. The anterior end forms pre-oral lobe.

The ciliated band at the pre-iral lobe 'orms into 2 separate bands, Pre-oral band of cilia, and post oral band of cilia. These 2 bands of cilia are drawn into many arms. They are nothing to do with the arms of the star fish. They are,

1) Ventro-median arm.

2) A pair of pre-oral arm.

3) Median dorsal arm.

4) A pair of antero-dorsai arm. 5; A pair of posterio-dorsal arm.

6) A pair of posterio-lateral arm.

7) A pair of post oral arm.

8) The digestive system is developed with mouth and anus. This larva resembles Tomaria larva of Balanoglossus.

This larva slowly grow s into the next larval form called Brachiolaria larva.

2. Brachiolaria Larva :

Bipinnaria larva swims for few weeks in the sea water.lt finally transforms into next larval stage called Brachiolaria larva.

1) It is bilaterally symmetrical larva.

2) It is pelagic larval form, it shows 3 brachiolar arms with suckers. They are one median and two lateral in position.

3) At the tip of brachiolar arms adhesive structures will make their appearance and they are for attachment.

4) The larva shows all the arms that areseen in the Bipinnaria, but these arms are very long and hanging. These ciliated arms will be helpful for swimming in the water.

5) The digestive system is completely developed with definite stomach and intestine.

This larva after swimming few settle-on a solid object and gets attached to it by its adhesive arms. Posterior end of the larva enlarges and lifts to the right-side. From this rudiments of 5 arms will arise. Thus slowly the larva metamorphosis into an adult.

3. Auricularia Larva : In Holothuroidea this larval form is seen.

1. It is a free swimming pelagic larva.

2. Arms are absent. Alimentary canal is developed. It opens with mouth and ends with anus.

3. Intestine is curved.

4. In Japan and Bermuda very big auricularia larval forms are developed. They are 15 mm in length. Usually this larva is 1 mm in length.

5. Ciliated bands are well-developed. Ciliated band continues through oral loop and anal loop.

4. Ophiopluteus larva : This larva is seen in the life history of opuriodea (Brittle star). It shows many long arms. It is bilaterally symmetrical. It is transparent. It is Pelagic. The arms are supported by calcareous rods. The arms are directed upwards. Preoral loop is reduced . Ciliated band is undivided. The posterc-lateral arms are very long and they are directed forwards. The digestive system is developed. It opens with mouth and ends with anus. This larva swims for some timebefore undergoing metamorphosis.

Echinopluteus larva : It is seen in the life history of Echinoidea.

1. It is a microscopic larva.

2. It swims in water.

3. This larva shows ciliated bands which are developed into arms.

4. Fully developed echinopluteus larva 4 or 5 pairs of arms are present.
Usually 6 pairs of arms should be resulted.

5. The arms are supported by (CaC0₃) Calcareous rods.

6. The digestive system is developed which shows mouth and anus.

7. It develops hydrocoel and vestibule. These parts grow on the oral side of the animal. From the hydrocoel five radial canals will develop.

This larva undergoes rapid metamorphosis and develops into an adult.

5 Doliolaria :

In crinoidea group of animals the larval form is Doliolaria larva.

1. It is a free swimming larval form.

2. It contains an apical tuft of cilia which will be sensory.

3. On the mid ventral line near apical plate adhesive pit will be present.

4. The body shows 4 or 5 ciliated bands

5. In between 3rd and 2nd ciliated bands vestibule is present.

After swimming for some time it will develop a stalk. It is called Pantacrinoid larva. It will attach to the substartum. The internal organs will rotate at 90°. It develops into an adult.

Significance of Echinoderm larva : The larval forms of all classes in Echinodermata will show general resemblance. The crinoidea larva differs from this pattern. In general all the larvae show that they might have come from same ancestor. Hence the common ancestor is coelomate, bilaterally symmetrical and free swimming.

These larvae also show resemblance with Toronaria of Balanoglossus. Thus the study of Echinoderm larva has a phylogenetic significance.

STAR FISH-REPRODUCTIVE SYSTEM

noreply@blogger.com (amith) — Fri, 08 Jan 2016 08:38:00 +0000

REPRODUCTIVE SYSTEM-FERTILIZATION - DEVELOPMENT IN STAR FISH

Star fish is unisexual. Male and female animals are separate. Sexual dimorphism is not seen. Only during the breeding season they can be recognized.

Gonads: Rve pairs of gonads are present in star fish. One pair is present at the base of each arm. The gonads of male are called testis. The gonads of female are called ovaries. They are present between the pyloric caecae and the ampullae. The ducts and other structures are absent usually.

Each gonad is a branched structure. It looks like bunch of grapes. It is surrounded by blood sinus. The side of gonads differ in different seasons. In breeding season they increase in size, and may reach upto the tip of the arm.

Each gonad gives a small ciliated duct which is termed as gono duct This duct opens through a small gonopore on the aboral surface at the angle of two adjacent arms, Sperms and ova are produced in gonads.

Fertilisation : Fertilisation is external. It takes place in water-sperm fertilises an ovum and a zygote is formed.

Development : The fertilised egg is 0.5 mm in diameter. The egg is homolecethal. Cleavage is holoblastJc. A ciliated coeloblastula is formed. This swims in water. It undergoes invagination and gives two layered gastrula. The outer layer is ectoderm and inner layer is endoderm. A narrow archenteron is formed in the endoderm. The archentron opens to the outside by blastopore. The blastopore gives a larval anus. Gastrula develops into a larva called Bipinnaria.

BIPINNARIA LARVA :

The gastrula elongates in length and it gives rise to Bipinnaria larva.

1. It is a bilaterally symmetrical, free swimming pelagic larva.

2. The pre oral region is elongated. Post oral region is broad. The anterior end forms pre oral lobe.

The ciliated band at the pre oral fobe forms into 2 separate bands.

a) Pre oral band of cilia,

b) Post oral band of cilia.

These 2 bands of cilia are drawn into many arms. They are nothing to do with the arms of the starfish. They are

1. Ventro median arm

2. A pair of pre oral arm

3. Median dorsal arm

4. A pair of antero-dorsal arm

5. A pair of posterio-dorsal arm

6. A pair of posierio-lateral arm

7. A pair of post-oral arm

8. The digestive system is developed with mouth and arms.

This larva slowly grows into the next larval form called Brachiolaria larva.

BRACHIOLARIA LARVA :

Bipinnaria larva swims for few weeks in the sea water. It finally transforms into next larval stage called Brachiolaria larva.

1. It is bilaterally symmetrical.

2. It is pelagic larval form, ft shows 3 brachiolar arms with suckers. They are one median and two lateral in position.

3. At the tip of brachiolar arms adhesive disc will make their appearance and they are for attachment.

4. The larva shows all the arms that are seen in the Bipinnaria, but these arms are very long and hanging. These ciliated arms will be helpful for swimming in the water.

5. The digestive system is completely developed with definite stomach and intestine.

This larva after swimming for few weeks settle on a solid object and gets attached to it by its adhesive arms.Posterior end of the larva enlarges and pushed to the right side. From this rudiments of 5 arms will arise. Thus slowly the larva metamorphosis into adult.

Metamorphosis :

1. The brachiolaria larva is bilaterally symmetrical.

2. After swimming for 7 or 8 weeks it settles down on some substratum and attached by its sucker and adhesive arms to it.

3. The posterior end of the larva enlarges and bends to the right side.

4. Five projections are formed. They develop into five arms of the adult.

5. The larva undergoes clock wise rotation of 90° because of which right side of the posterior part becomes the aboral surface and the left side becomes the oral surface.

6. The ciliated bands and the larval arms disappear.

7. Water vascular system and haemel system will d eve lope. It slowly transforms into adult, ft can creep on the substratum with the help of tube feet.

STAR FISH-NERVOUS SYSTEM AND SENSE ORGANS

noreply@blogger.com (amith) — Fri, 08 Jan 2016 08:10:00 +0000

NERVOUS SYSTEM AND SENSE ORGANS OF STAR FISH

In Star fish the nervous system is primitive and diffuse type. It has no ganglia. It is associated with the epidermis. It has nerve fibres.

J. Smith (1937) divided the nervous system into three parts.

1. Oral or ectoneural system : It is called superficial system, as it is present below the epidermis. It is sensory in function. It has nerve ring around the mouth. It supplies nerves to the oesophagus and peristomial membrane . Five large radial nerve cords arise from angles of the nerve ring. They travel to the arms. Each nerve cord terminates in a optic cushion near the base of the tentacle. In a cross section the radial nerve cord is 'V shaped. It is covered by epidermis on its outside. It gives nerves to the tube feet. Below the body wall sub-epidermal nerve plexus is present. Radial nerve cords will unite with it.

2. Aboral (or) entoneural System : The sub-epidermal plexus is thickened on the outer margins of an ambulacral groove and from marginal nerve cords. They travel the whole length of the arms. They give lateral nerves. They form a plexus below the coebmic lining. It is mesodermal in origin. It is motor in function.

3. Deep or hyponeural system: It is developed from the mesoderm and is primarily motor in function. Like ectoneural system, it forms a double nerve ring, which lies aboral to the main nerve ring. In each arm, it gives off a pair of lateral cords, called Lange's nerves. Each Lange's nerve is a plate of nervous tissue. It lies in the outer oral wall of the radial hyponeural sinus. The branches of Lange's nerve go to muscles of the arm.

Sense Organs :

Poorly developed sense organs are seen in Star fish. They are,

1. Neurosensory cells and

2. Eyes

1. Neurosensory cells : Certain neurosensory cells occur scattered all over the body surface. A sensory cell is slender and fusiform. It has a nucleus. Thread like process is developed on the outer surface. The cell is connected to the subepidermal nerve plexus by the fibre. These cells are tactile or olfactory in function.

2. Eyes: At the base of each tentacle, one eye spot is present on the oral side. It is the optic cushion of radial nerve cord. It has ocelli. An ocellus is a cup shaped pocket of the ectoderm. It has a lens like transparent thickening formed by the epidermis.

The wall of the cup has pigment cells. Among the pigment cells retinal cells are present. Each retinal cell ends in a bulb, which is projecting upto the cavity of the pit. It is connected with a fine fibre to a radial nerve cord. Eye spots are able to detect changes in light intensity.

STAR FISH-BLOOD VASCULAR SYSTEM

noreply@blogger.com (amith) — Fri, 08 Jan 2016 07:59:00 +0000

BLOOD VASCULAR SYSTEM IN STAR FISH

A true blood vascular system is absent. In star fish, this system circulates digested food to all body parts. It can be studied under two parts.

1. Perihaemal system.

2. Haemal system.

1. Perihaemal system : h has many tubular coelomic sinuses called perihaemal system because they enclose channels or Haemal system. The perihaemal vessels run parallel to

water vascular system and encircle it.

1. Axial sinus It is a small tube. It encloses stone canal and axial gland forming an axial complex.

2. Aboral ring sinus: It is five sided sinus found inside the aboral wall of the central disc. It is incomplete in the region of the canal"

3. Genital sinuses: Each gonad is encircled by a small genital sinus. It
is connected with the aboral ring sinus by very small branch.

4. Oral ring sinus: It is present around the mouth. It is divided into two
a) A smaller inner ring. b) A larger outer ring.

The oral end of the axial sinus communicates with the inner division of the ring sinus.

5. Radial perihaemal sinuses: It arises from the outer division of the oral ring sinus and goes into each arm. This sinus in each arm is divided into two by septum. Small, thin branches are given from the radial perihaemal sinuses into the podia.

6. Marginal sinuses : Longitudinal marginal sinus is present just aboral to the marginal nerve cord.

7. Peri-branchial sinuses : These are present in the form of circular spaces encircling the basal parts of the gills.

2. Haemal system : It is reduced. It has spaces which do not show epithelial lining These spaces inter-communicate with each other. The haemal channels are enclosed in the coelomic spaces of the perehaemal system. They contain coebmic fluids.

The mouth is surrounded by a oral haemal ring. This runs into the septum dividing the hyponeural ring sinus. From the oral haemal sinus arises radial haemal sinuses. Each one enters into one arm.

The oral haemal ring is connected with the aboral haemal ring through the axial gland. A pair of gastric haemal tufts arise from the sinus in the region of cardiac stomach wall. They open into the haemal plexus of the axial gland.

These haemal channels are in fact not true blood vessels. They contain fluid which helps in the circulation and distribution of digested food materials.

BIOZOOM

CELL NUCLEUS STRUCTURE-FUNCTION

Structure and Functions of NUCLEAS In Cell

RIBOSOMES -STRUCTURE - FUNCTION

Ribosome Structure Types And Functions

ENDOPLASMIC RETICULUM-STRUCTURE- TYPES RETICULUM (ROUGH ER- SMOOTH ER) FUNCTIONS

Structure –Types And Functions Of Endoplasmic Reticulum

GOLGI APPARATUS (GOLGI BODY)-STRUCTURE AND FUNCTIONS

GOLGI COMPLEX –STRUCTURE-FUNCTION

LYSOSOMES –STRUCTURE-FUNCTIONS

Lysosomes-Structure –Enzymes-Polymorphic Nature-Function-Biogenesis

MITOCHONDRIA- DEFINITION-STRUCTURE- FUNCTION

MITOCHONDRIA STRUCTURE AND FUNCTIONS

PLASMA MEMBRANE –CELL MEMBRANE- STRUCTURE -FUNCTIONS

CELL MEMBRANE- PLASMA MEMBRANE STRUCTURE -FUNCTIONS

AN ANIMAL CELL-STRUCTURE

ANIMAL CELL-STRUCTURE-ORGANELLES

PROKARYOTIC CELL- EUKARYOTIC CELL- DIFFERENCES

Differences between Prokaryotic Cell and Eukaryotic Cell

PROKARYOTIC CELL -STRUCTURE

BASIC STRUCTURE OF A PROKARYOTIC CELL

CELL BIOLOOY-INTRODUCTION (brief history of cytology)

BALANOGLOSSUS-AFFINITIES-PHYLOGENITC RELATIONS

BALANOGLOSSUS-SYSTEMATIC POSITION IN THE ANIMAL KINGDOM

HEMICHORDATE CHARACTERS -CLASSIFICATION

HEMICHORDATES -GENERAL CHARACTERS- CLASSIFICATION

Classification :

BALANOGLOSSUS -REPRODUCTIVE SYSTEM, AND EMBRYO DEVELOP­MENT

BALANOGLOSSUS-CIRCULATORY SYSTEM

BLOOD VASCULAR SYSTEM IN BALANOGLOSSUS

BALANOGLOSSUS- RESPIRATION

RESPIRATION MECHANISM IN BALANOGLOSSUS

BALANOGLOSSUS-DIGESTIVE SYSTEM

DIGESTIVE SYSTEM OF BALANOGLOSSUS

BALANOGLOSSUS-ANATOMY-BODY WALL

BALANOGLOSSUS -INTERNAL STRUCTURES AND BODY WALL

BALANOGLOSSUS-EXTERNAL MORPHOLOGY

BALANOGLOSSUS.-HABIT, HABITAT-EXTERNAL CHARACTERS

ECHINODERMATA WATER VASCULAR SYSTEM

WATER VASCULAR SYSTEM-AMBULACRAL SYSTEM IN DIFFERENT ECHINO­DERMS

ECHINODERMATA CHAHACTERS- CLASSIFICATION

ECHINODERMATA GENERAL CHARACTERS AND CLASSIFICATION

Classification of Echinodermata:

ECHINODERMATA LARVAE

Echinodermata larval forms

STAR FISH-REPRODUCTIVE SYSTEM

REPRODUCTIVE SYSTEM-FERTILIZATION - DEVELOP­MENT IN STAR FISH

STAR FISH-NERVOUS SYSTEM AND SENSE ORGANS

NERVOUS SYSTEM AND SENSE ORGANS OF STAR FISH

Sense Organs :

STAR FISH-BLOOD VASCULAR SYSTEM

BLOOD VASCULAR SYSTEM IN STAR FISH

BALANOGLOSSUS -REPRODUCTIVE SYSTEM, AND EMBRYO DEVELOPMENT

WATER VASCULAR SYSTEM-AMBULACRAL SYSTEM IN DIFFERENT ECHINODERMS

REPRODUCTIVE SYSTEM-FERTILIZATION - DEVELOPMENT IN STAR FISH