notes

Protista and Paramoecium

Mon, 20 Sep 2010 14:11:35 +0100

PROTISTA

CLASSIFICATION

Phylum Opalinata

· They have numerous cilia in longitudinal oblique rows on entire body.

· Cytostome is absent

· Body is covered by thin and tough pellicle.

· Mouth, cytopyge, food vacuoles and contractile vacuoles are absent.

· Two or more monomorphic nuclei are present.

· Asexual reproduction takes place by binary fission.

· Sexual reproduction takes place by flagellated gametes.

· They are endoparasites of mainly anurans.

Eg. Opalinata, Protoopalinata

Phylum Ciliiophora

· Body is naked.

· They have two nuclei- a macro nucleus and a micro nucleus.

· Definite mouth and gullet are present except in parasites.

· Temporary anal aperture, cytopyge, is present.

· Contractile vacuoles are present.

· Asexual reproduction by binary fission.

· Sexual reproduction by conjugation.

Eg. Paramoecium, Vorticella

Phylum Sarcodina

· Body is naked or with a hard shell or test.

· Locomotion and food ingestion by pseudopodia.

· Cytoplasm is differentiated into outer ectoplasm and inner endoplasm.

· Nucleus is single.

· Contractile vacuoles are present.

· Asexual reproduction by binary fission.

· Sexual reproduction by flagellated or amoeboid gametes.

Eg. Amoeba, Entamoeba histolytica

Fig. Amoeba

Phylum Dinophyta

· They are unicellular algae with cellulose wall divided into plates.

· The cellulosic plates give them armoured appearance.

· They have two flagella- Longitudinal and transverse.

· They reproduce asexually only.

· Nutrition by photosynthesis.

· Reserve food material in starch or amyloid substance.

Eg. Noctiluca, Ceratium

Phylum Euglenophyta:

· Body covered with pellicle.

· Anterior end have gullet or cytopharynx (cyto- cell, pharynx- initial part of mouth)

· One or two flagella arising from anterior gullet.

· Chromatophores are present (contain chlorophyll).

· Reserve food material is paramylon or oils.

· No sexual reproduction.

· Asexual reproduction by longitudinal binary fission.

· Under adverse conditions they form cysts.

Eg. Euglena, Paranema

Possible questions:

Define/Explain:

Give one example each of:

a. Opalinata

b. Ciliophora

c. Sarcodina

d. Dinophyta

e. Euglenophyta

Write short notes on:

a. Opalinata

b. Ciliophora

c. Sarcodina

d. Dinophyta

e. Euglenophyta

STUDY OF PARAMOECIUM

Systematic Position:

Kingdom : Protista

Phylum : Ciliophora

Class : Ciliata

Order : Holotricha

Family : Paramoecidae

Genus : Paramoecium

Species : caudatum

Pellicle:

· The shape of the body is definite and constant because of the body is covered by a thin, firm and flexible outer covering called as pellicle.

· The pellicle has a double membrane.

· The outer membrane is continuous with cilia and inner with ectoplasm.

· Under microscope, it shows a large number of hexagonal depressions.

· Each depression is perforated by a central aperture.

· A cilium projects out through this central aperture.

· The pellicle can be regenerated if it is lost in injury.

Cilia and its structure

· The entire body of the Paramoecium is covered by short hair like processes called as Cilia.

· They serve as organs of locomotion and food capture.

· The length of cilia is uniform throughout but they are longer at the posterior end. Therefore, the specific name caudatum.

· The outer part of cilium is surrounded by plasma membrane.

· Inside, there are nine pairs of longitudinal fibrils present in the peripheral rings.

· There are two central fibrils.

· Each cilium is connected to a small spherical basal granule or kinetosome in the cytoplasm.

· The diameter of peripheral fibres is 260Å and the fibres are composed of two subfibrils having diameter 180 to 250 Å. The subfibrils are called as subfibril A and B.

· The subfibril A gives out two arms on one side which show clockwise direction.

· The central fibrils have diameter of about 250 Å.

Infraciliary System

· The cilia of Paramoecium are connected below pellicle with a fibriller system called infraciliary system.

· From each kinetosome or basal granule, a fine fibril called kinetodesmos is given out.

· From each kinetosome, a kinetodesmos extends to the right.

· Each kinetodesmos runs parallel to similar fibrils from other kinetosomes.

· This bundle of parallel fibrils is known as kinetodesma.

· The longitudinal row of kinetosomes with their kinetodesmata (singular of kinetodesma) is called as kinety.

The infraciliary system is thought to coordinate the beating of cilia and formation of organelles in the cell division.

General characters of Phylum Porifera

Mon, 20 Sep 2010 11:57:43 +0100

Phylum Porifera (Sponges)

General Characters of phylum Porifera
1. They are aquatic, mostly marine, and few fresh water, solitary or colonial, fixed to rocks, shell or other objects.
2. The body is multicellular.
3. They are diploblastic having two layer of cells viz. ectoderm and endoderm separated by gelatinous mesoglea.
4. The body is perforated by numerous pores called ostia through which water enters into the large central body cavity called as spongocoel . The water leaves the body through single large anterior opening called osculum.
5. Canal system is present.
6. They possess an internal skeleton made of calcareous spicules or siliceous spicules and sponging fibres.
7. Digestive system is not well developed, nutrition is holozoic and digestion is intracellular.
8. Respiration and excretion by simple diffusion.
9. Nervous system is absent.
10. Reproduction is sexual as well as asexual.
11. Fertilization is internal.
12. Development includes free swimming larva.

Phylum Porifera is divided into three classes: Calcarea, Hexactinellida and Demospongiae.

Class Calcarea:
1. They are commonly called as calcareous sponges.
2. Body is cylindrical or vase shaped.
3. Skeleton composed calcareous spicules
4. Canal system is Ascon, Sycon or Leucon type.
5. Asexual reproduction by budding. Free swimming larva is called as amphiblastula.
e.g. Leucosolenia, Clathrina

Fig: Leucosolenia

Class Hexactinellida:

1. They are popularly known as Glass sponges.

2. Body is cylindrical, vase shaped or funnel shaped.

3. The skeleton consists of Hexactinal silicious spicules.

4. Canal system is Leucon type (Eurypylous).

e.g. Euplectella

Fig. Euplectella

Class Demospongiae:
1. Body is compact, often massive and brightly coloured.
2. Skeleton consists of silicious spicules or spogin fibres or both.
3. Canal system is Leucon type (Eurypylous, aphodal, diplodal).
4. Asexual reproduction by gemmules.
5. Larva is called as stereogastrula.
e.g. Spongilla, Chalina

Fig: Spongilla

Probable Question(s):

Describe the general characters of Phylum Porifera giving the characters of its classes with examples.

Reproduction in Paramoecium

Tue, 21 Sep 2010 07:41:00 +0100

Reproduction in Paramoecium

Paramoecium reproduces sexually as well as asexually. Commonly, it reproduces asexually by transverse binary fission under favourable conditions of food. The sexual reproduction occurs by conjugation but at times by processes such as endomixis, autogamy, cytogamy and hemimixis.

Binary Fission:

It is the most common type of reproduction in Paramoecium in which the division is transverse. It takes place during favourable conditions.

1. Paramoecium stops feeding.

2. Becomes less active.

3. Develops two minute pores near the middle of its body for the future contractile vacuoles of daughter individuals.

4. Doubles its cilia

5. Oral groove disappears

6. Micronucleus divides by mitosis and they move away from each other.

7. Macronucleus divides by amitosis. It simply becomes elongated and constricted in the middle forming two daughter nuclei.

8. A transverse constriction forms a round in the middle of the body.

9. A new cytopharynx and cytostome are formed for the future daughter.

10. The furrow deepens till the cytoplasm is completely divided resulting in two daughter paramecia of equal size.

11. Each daughter paramecium receives one contractile vacuole from the parent and develops one new contractile vacuole.

12. The time required for the process of Binary fission is two hours and it may occur one to four times per day.

13. The individuals produced are genetically identical (clones).

Conjugation:

Conjugation is a means of sexual reproduction in Paramoecium.

1. In conjugation, two different mating types come in contact and attach to each other by their oral surfaces.

2. The individuals which take part in conjugation are called as conjugants.

3. The pellicle and ectoplasm of both individuals from the attached surface disintegrate and a protoplasmic bridge is formed between them.

4. The macronucleus disintegrates as it does not take part in the process.

5. Micronucleus divides by meiosis to form four haploid nuclei. Out of the four, three degenerate.

6. The remaining nucleus divides mitotically to form a smaller, motile male pronucleus and a larger, immotile female pronucleus.

7. The male pronucleus of each conjugant migrates to the other through the protoplasmic bridge and fuses with the female pronucleus to form diploid zygote. This process of fusion of nuclear material is known as amphimixis.

8. The conjugants now separate and are called as exconjugants.

9. The zygote nucleus of each exconjugant divides three times to form eight nuclei. Four enlarge and become macronuclei and other four become micronuclei. Three micronuclei degenerate.

10. Each exconjugant now has four macronuclei and one micronucleus. The micronucleus divides mitotically into two.

11. Each exconjugant now divides by binary fission into two so that each individual has two macronuclei and one micronucleus.

12. The micronucleus of each individual again divides with the division of each daughter Paramoecium forming two individuals, each containing one macronucleus and one micronucleus.

13. Thus, from each exconjugant, four young Paramoecia are formed at the end of conjugation.

Significance of Conjugation:

1. Rejuvenation

2. Nuclear reorganization

3. Hereditary variation

Endomixis: Endomixis is a process of nuclear reorganization which occurs in a single individual without the fusion of gametic nuclei.

Autogamy: Autogamy is the process of nuclear reorganization which occurs in a single individual. In this process, micronuclei of the same individual fuse together.

Hemixis: Hemixis is the process of reorganization of macronucleus without any change in micronucleus.

By: S. A. Pingle

Introduction to Branches of Zoology

Sat, 14 Aug 2010 01:29:08 +0100

Introduction to branches of Zoology

Zoology is branch of Science that deals with the study of animals. Large number of animals are useful to human beings and others are harmful as well. These animals are of great economic importance to man. The applied and economic aspects of zoology are included in syllabi of Indian as well as foreign Universities.

The subject Zoology is interrelated with other branches of science such as Physics, Chemistry, Geology and Statistics.

Some of the important branches of zoology are:

a. Physiology b. Cell biology c. Biochemistry d. Biostatistics

e. Molecular biology f. Biotechnology g. Biophysics h. Entomology

i. Immunology j.Aquaculture

Physiology:

Physiology is the study of various functions and mechanisms of cells, organs or the entire living organism. Different organs perform different functions. For example physiology of kidney refers to the study of excretion, the lungs perform respiration. There are different branches of physiology.

a. General Physiology: Different organisms have some common structures and functional properties of these structures are common as well. The study of these general physiological activities is called as general physiology.

b. Cellular Physiology: It deals with the functions of the cell and includes processes such as cellular respiration, cell excretion etc.

c. Animal Physiology: It involves the study of various life processes such as digestion, respiration, circulation and excretion etc.

d. Comparative physiology: It deals with the functional aspects of various organs in defferent animals. For example study of excretion, digestion, respiration and circulation in frog, birds and humans.

Cell Biology:

It is a specialized branch which deals with the study of fine structure of cell, its organelles, physiology, multiplication, heredity and development. A cell is bound by plasma membrane which enables the exchange of certain molecules with the surroundings. The matrix bound by plasma membrane is called as cytoplasm. The cytoplasm contains membrane bound structures called as organelles which perform specific functions. The organelles include the endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria and plastids. These organelles, their structures, form, composition and functions are studied under cell biology.

Biochemistry:

It is the branch of science concerned with the chemical substances and the processes that occur in animal, plant and microorganisms. It involves the quantitative determination and structural analysis of organic compounds that comprise the basic constituent of the cells like protein, carbohydrates and lipids. Biochemistry is the study of all the complex interrelated changes occurring within the cell.

Biostatistics:

Biostatistics is the study of application of statistical methodology to analyze biological measurements. Biostatistics can be applied in Physiology, anatomy, pharmacology, medical science, community medicine and public health.

Molecular biology:

It is the field of science that deals with the study of chemicals, structures and processes of biological phenomena at the molecular level. It is associated with the macromolecules such as nucleic acid, enzymes, and proteins etc. that are essential for life processes. It also deals with the molecular basis of genetic processes.

Biotechnology:

Biotechnology is the advanced branch of science which deals with the use of living organisms for the industrial production of chemicals, drugs, vaccines, enzymes, hormones etc. of human interest. In biotechnology, various microorganisms like bacteria, fungi and algae are employed for the production of alcohol, biogases, drugs, vaccine, hormones, enzymes etc. There are several divisions of biotechnology such as

· Pharmaceutical technology

· Fermentation technology

· Enzyme technology

· Agriculture biotechnology

· Tissue culture technology

· Food biotechnology

Biophysics:

It is the discipline of science concerned with the application of principles and methods of physical science to biological science. Biophysics deals with biological functions when the functions depend upon the physical agents such as electricity, mechanical force, light, heat, sound and radiation etc.

Entomology:

Entomology is the branch of zoology that deals with the study of insects. Entomology is divided into basic entomology and applied entomology. Basic entomology deals with the morphology, physiology, biochemistry and taxonomy of insects. Applied entomology deals with the economically important insects i.e. useful and harmful insects. Several insects affect the health of man and domestic animals. The study of these insects is called as medical entomology.

Immunology:

It is the branch of zoology which deals with the study of body’s defense against the disease causing microorganisms. The immune system is the collection of the cells that keep record of invading pathogens, so that, if they reappear, they can be destroyed. The term immunity describes all the bodily mechanisms that prevent entry or establishment of parasite or destroy the parasite.

Aquaculture:

Aquaculture involves production of useful aquatic plant and animal such as fish, prawns, shrimps, lobsters, frogs, crabs, oysters under controlled conditions. The main purpose of aquaculture is to step up the production of aquatic food utilizing the available water sources.

By: S. A. Pingle