BIOLOGY 3 Marks Question

1. Cell wall:

• It is made of peptidoglycan, i.e., polysaccharide + amino acids, in Monera.
• Cell wall is present only in some protists.
• In Fungi, cell wall is made of chitin.
• In Plantae, it is made of cellulose.
• Cell wall is absent in Animalia.

2. Body organization:

• It is cellular and prokaryotic in Monera.
• It is cellular and eukaryotic in Protista.
• In Fungi, it is multicellular with loose tissue formation.
• In Plantae, it is multicellular with tissue systems and organs.
• In Animalia, it is multicellular with tissue, organ, and organ system levels of organisation.

A bacterial cell consists of following components:

1. Cell envelope: It is the outer covering of protoplasm of bacterial cell. It contains mucilage sheath, cell wall and plasma membrane.
2. Cytoplasm: It is a crystallo colloidal complex that forms the protoplasm excluding its nucleoid. Membrane bound cell organelles are absent. Cytoplasm along with nucleoid are together called as protoplasm.
3. Nucleoid: It represents the genetic material of prokaryotes. Nucleoid consists of a single circular strand of DNA duplex which is super coiled with the help of RNA. No nuclear envelope is present.
4. Plasmids: These are self-replicating, extrachromosomal segments of double-stranded, circular, naked DNA.
5. Flagella: These are unstranded, equivalent to a single microtubular fibre. These help in movement and locomotion.
6. Pili and fimbriae: Pili are longer, fewer and thicker tubular outgrowths made up of protein pilin. Fimbriae are small bristle-like fibres sprouting from cell surface in large number. Pili are helpful in attaching to recipient cell and forming conjugation tube. Fimbriae cause agglutination of RBC. They also help in mutual clinging of bacteria.

All photosynthetic organisms contain one or more organic pigments that are capable of absorbing visible radiations, which will initiate the photochemical reaction of photosynthesis. Three major classes of pigments found in plants and algae, are the chlorophylls, the carotenoids and the phycobilins. Carotenoid and phycobilins are called accessory pigments since; the quanta (packets of light) absorbed by these pigments can be transferred to chlorophyll. The diversity of light harvesting pigments in alga implies that the common ancestor was primitive and that no close affinity exist between blue, green, red, brown, golden brown and green algae, to use their common names. The characteristic pigments of different classes are mentioned below.

Class	Common Name	Major Pigments
Chlorophyceae	Green algae	Chlorophyll- a and chlorophyll-b. Chlorophyll-a,
Phaeophyceae	Brown algae	Chlorophyll- c, Fucoxanthin. Chlorophyll-a,
Rhodophyceae	Red algae	Chlorophyll- d. Phycoerythrin.

Viruses are non-cellular, ultramicroscopic, infectious particles. They are made up of envelope, capsid, nucleoid and occasionally one or two enzymes. Viruses possess an outer thin loose covering called envelope. The central portion of nucleoid is surrounded by capsid that is made up of smaller sub-units known as capsomeres. The nucleic acid present in the viruses is known as nucleoid. It is the infective part of the virus which utilises the host cell machinery. The genetic material of viruses is of four types:

1. Double stranded DNA (dsDNA) as found in pox virus, hepatitis-B virus and herpes virus, etc.
2. Single stranded DNA (ssDNA) occur in coliphage fd, coliphage fx174.
3. Double Stranded RNA (cteRNA) occurs in Reo virus
4. Single stranded RNA: (dsRNA) occur in TMV virus, polio virus, etc. Four common viral diseases are (i) Polio, (ii) AIDS, (iii) Hepatitis-B, (iv) Rabies.

The four major groups of Protozoa are:

1. Amoeboid protozoans: These organisms live in fresh water, sea water or moist soil. They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba. Marine forms have silica shells on their surface. Some of them such as Entamoeba are parasites.

2. Flagellated protozoans: The members of this group are either free-living or parasitic. They have flagella. The parasitic forms cause diaseases such as sleeping sickness. Example: Trypanosoma.

3. Ciliated protozoa or ciliates: They are aquatic individuals that form a large group of protozoa. Their characteristic features are the presence of numerous cilia on the entire body surface and the presence of two types of nuclei. All the cilia beat in the same direction to move the water laden food inside a cavity called gullet. Example: Paramoecium, Vorticella,etc.

4. Sporozoans: They include disease causing endoparasites and other pathogens. They are uninucleate and their body is covered by a pellicle. They do not possess cilia or flagella. They include the malaria causing parasite Plasmodium.

In two kingdom classifications, there was no differentiation between the eukaryotes and prokaryotes, unicellular and multicellular and photosynthetic and non-photosynthetic organisms. In the two-kingdom classification the bacteria, blue-green algae, fungi, mosses all were included under the kingdom Planate. It placed together groups which widely differed from each other. A large number of organisms did not fall into any category. Thus, the two-kingdom classification was insufficient and inadequate. The five kingdom classification resolved the issues as it considered other factors like cell structure, mode of nutrition, thallus organisation, reproduction and phylogenetic relationships. This system of classification placed the organisms into five different categories. All the prokaryotes were placed under Kingdom Monera. The unicellular eukaryotes were placed under Kingdom Protista. The fungi occupied a separate kingdom. Thus, it proved to be adequate and much better than the two-Kingdom classification.

1. Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the groups in a hierarchy of categories.
2. Biological classification is helpful to collect sufficient information about the essential features of the group by studying one or two organisms. It also helps in knowing the relationship amongst different groups of organisms.
3. The objectives of biological classification are, to describe and identify all the possible types of species and to arrange the species in various categories on the basis of their similarities and dissimilarities.
4. Atul is curious, inquisitive and sincere towards his studies.

Cyanobacteria:

• They are unicellular, colonial or form trichomes.
• The colonies are surrounded by a gelationous sheath.
• They have chlorophylla, similar to green plants.
• They are photosynthetic autotrophs.
• They have a pigment, c-phycocyanin, that gives them the characteristic blue-green colour.
• Some of them can fix atmospheric nitrogen in the specialised cells, called heterocysts.
• They show vegetative reproduction by fragmentation or cell division.
• No sexual reproduction has been reported. as genetic material.

S.No.	Ascomycetes	Basidiomycetes
1.	In the ascocarp, the fruiting body, each ascus produces eight ascospores.	In the basidiocarp, the fruiting body, each basidium produces four basidiospores.
2.	The sexual spores, ascospores are produced endogenously.	The sexual spores, basidiospores are produced exogenously.
3.	Asexual spores are formed.	No asexual spores are formed.
4.	Sex organs are formed.	Sex organs are absent.
5.	Oogamy is common.	Somatogamy is common.

1. AIDS is a viral disease.
2. HIV (retrovirus).
3. RNA.
4. Value shown by Ankit and his friend are team work, motivational capacity, sense of understanding AIDS and application in life, national responsibility and commitment towards society.

1. Social responsibility, commitment towards community health and respect for elders.
2. The causal agent of malaria is Plasmodium the malarial parasite. It is a digenetic parasite with two hosts, i.e., humans and female Anopheles mosquito.

Female Anopheles injects saliva, while puncturing human skin for obtaining blood. The infected mosquito contains a large number of sporozoites in its saliva. The same are passed into human blood.

3. Plasmodium has three phases in its life cycle-schizogony, gamogony and sporogony.
4. One can do following activities to avoid malaria in your surroundings:

1. Covering open water drains.
2. Proper drainage for quick transfer of waste water into streams.
3. Spraying of insecticides, fumigation in surroundings, cattle sheds, etc.
4. Using mosquito net, repellents and antimosquito cream.

Diatoms and desmids are inducted under chrysophytes, kingdom-Protista. These are the main producers in the ocean. They prepare food not only for themselves but also for the other life forms in the ocean. This is the reason they are also called as 'pearls of ocean. Body of diatoms is covered by siliceous shell known as frustules. 'Diatomaceous earth' is the accumulation of large deposits of diatoms that forms a siliceous covering extending for several 100 m formed in billions of years. The material obtained from these deposits is used in polishing and filtration of oils and syrups.

S.No.	Basidiomycetes	Phycomycetes
1.	The mycelium is septate.	The mycelium is aseptate and coenocytic.
2.	No asexual spores are formed.	Asexual reproduction is by zoospores or aplanospores.
3.	Sexual reproduction is by somatogamy.	Sexual reproduction is isogamous, anisogamous or oogamous.
4.	A fruiting body, the basidiocarp is formed.	No fruiting body is formed; the zygospore or oospore directly undergoes development.
5.	A dikaryophase is seen in the life cycle.	No dikaryophase is found in the life cycle.

Neurospora crassa is known as’Drosophila of Plant Kingd om’. Itisau sefulmodel organism as it can be easily cultured in laboratories due to simple life cycle and simple nutrient requirements. Neurospora crassa is the subject of intensive research leading to significant contributions. By using Neurospora mutants, Mary Mitchell reported the first example of gene conversion. Barbara McClintock, famous for her work in transposition, showed for the first time, that fungal chromosomes were typically eukaryotic using it. Further, several aspects of metabolism and cytogenetic were first studied in it. The first sequencing of a mitochondrial nucleic acid came from this fungus and self-splicing of a mitochondrial intron was demonstrated for the first time. Neurospora also made significant contributions to the study of the mechanisms underlying protein import into mitochondria. Moreover, mitochondrial plasmids were discovered and characterized. It has also been important in areas of biological research, including recombination, DNA repair, differentiation, morphogenesis and cell biology, and notably, DNA methylation and silencing, findings applicable not only to the fungi, but to other eukaryotes as well.

Some bacteria are autotrophs, i.e., they synthesise their own organic food or ATP from inorganic substances, they are of two types:

1. They may be photosynthetic autotrophs and use light energy to synthesise their food.
2. They may be chemosynthetic autotrophs, which oxidise some inorganic compounds and use the energy released for the synthesis of their food.

Many are heterotrophs, i.e. they do not synthesise their food, but depend on an external source; they are of two types:

1. Some are parasites and depend on living organisms for their food.
2. Some are saprotrophs and depend on dead and decaying organic matter for food.

Virus is an obligate parasite. It is inert outside the host cell. It does not grow, divide or reproduce like normal organisms. Viruses are intermediate between living and non-living entities. Characters of virus similar to non-living objects are–

1. Absence of protoplast,
2. Ability to get crystallized, e.g., TMV, poliomyelitis virus,
3. Inability to live independent of a living cell,
4. High specific gravity which is found only in non-living objects,
5. Absence of respiration,
6. Absence of energy storing system,
7. Absence of growth and division, instead different parts are synthesized separately.

Ans. The criteria for five-kingdom classification are as follows:

1. Complexity of cell structure- All prokaryotic organisms are separated into kingdom Monera.
2. Body organisation- All unicellular organismsare grouped under Protista, while multicellular organisms are placed under kingdoms Fungi,Plantae and Animalia.
3. Mode of nutrition- Autotrophs, heterotrophs and holozoic organisms are separated in the kingdoms Plantae, Fungi and Animalia, respectively.
4. Life style- Producers are placed in kingdom Plantae, while consumers are in Animalia and decomposers in Fungi.
5. Phylogenetic relationships:

• The primitive prokaryotic organisms are placed in kingdom Monera.
• Kingdom Protista includes all unicellular and eukaryotic forms of life and it shows resemblances to the other kingdoms Fungi, Animalia and Plantae.
• The highly evolved organisms are placed in kingdoms Plantae and Animalia.

1. Kingdom Plantae: All green plants are taken under this kingdom. Majority of members are autotrophic. Exceptions are certain parasitic plants, like Venus fly trap. Plants show alternation of generation. Reproduction is vegetative, asexual and sexual.
2. Kingdom Animalia: Animals are mobile. They show holozoic nutrition, i.e., they ingest their food and break complex food substance into simpler compounds. Animals can be unicellular and multicellular. Reproduction is asexual and sexual.
3. Bacteria: Bacteria are unicellular. Among bacteria there are certain species which are believed to be on earth since life began on earth. Bacteria can be beneficial and harmful to humans. Nutrition is heterotrophic and autotrophic.
4. Lichens: Lichens are a very good example of symbiosis. Lichens are combination of algae and fungi. The algal part provides food and base to the fungal part, while the fungal part provides gases to the algal part. They are supposed to be very good tool to identify level of pollution in a given ecosystem.