BIOLOGY 2 Marks Questions

Phycobiont refers to the algal component of the lichens and mycobiont refers to the fungal component. Both of these are present in symbiotic relationship in which Algae prepare food for Fungi due to presence of chlorophyll whereas the fungus provides shelter to algae and absorbs water and nutrients from the soil.

Archaebacteria

1. Methane gas is produced from the dung of ruminants by the methanogens.
2. Methanogens are also involved in the formation of biogas and sewage treatment.

Characteristic Features of Euglenoids:

1. Fresh water organisms found in stagnant water.
2. Instead of cell wall they have a protein rich layer called pellicle whick makes their body flexible.
3. They are autotrophs in the presence of sunlight and heterotrophs in the absence of sunlight.
4. A small light sensitive eye spot is present.

1.  

1. Halophiles.
2. Thermoacidophiles.

2. They have a cell wall structure, which is responsible for this.

S.No.	Bacteria	Algae
i.	Most are heterotrophic, some are autotrophic.	All are heterotrophic.
ii.	Prokaryotic.	Eukaryotic.
iii.	Cell wall present.	Cell wall present.
iv.	Unicellular.	Multicellular.

1. Curdling of milk.
2. Lactobacillus is an important commensal in the gut flora of humans.
3. Penicillin antibiotics are prepared by bacteria.
4. Bacteria is a good decomposer, so it assists in completing the energy cycle.
5. Rhizobium bacteria helps in nitrogen fixation.

Difference between algae and fungi:

1. Algae is autotrophic, while fungi is heterotrophic.
2. Algae cannot be a parasite, while fungi can be a parasite.

1. Lignocolous: Growing on wood.
2. Saxicolous: Growing on rock.
3. Certicolous: Growing on bark.
4. Terricolous: Growing on soil.

Ascospore formation is the characteristic of class-Ascomycetes. Ascospores are a type of non-motile meiospores which are produced inside special sacs called asci (sing. ascus). An ascus often contains 8 ascospores because meiosis is accompanied by one mitotic division.

The four classes of fungi are as follows:

1. Phycomycetes: Mycelium is aseptate and branched.
2. Ascomycetes: Mycelium is septate and branched.
3. Basidiomycetes: Mycelium is septate and branched.
4. Deuteromycetes: Mycelium is septate and branched.

The four categories of bacteria are:

1. CoccusSpherical cell.
2. Bacillus Rod-shaped cell.
3. Vibrio Comma-shaped cell.
4. Spirillum Spiral-shaped cell.

1. Basidiomycetes.
2. Deuteromycetes.
3. Phycomycetes.
4. Basidiomycetes.

Differences between Phycomycetes and Ascomycetes are:

S. No.	Phycomycetes	Ascomycetes
1.	Hyphae are aseptate and coenocytic.	Hyphae or septate and branched.
2.	Asexual spores are zoospores.	Asexual spores are conidia.

Some fungi have evolved essential relationships with the roots of many living plants.These fungi grow around and into the roots. Both partners benefit so that neither would thrive without the other. This partnership is called mycorrhizal symbiosis.

Polluted waters usually have high amounts of phosphates and other nutritional elements that enhance the growth of the algae. This increased nutrient content in the polluted water becomes suitable for the growth of algae such as Nostoc and Oscillatoria.

1. They help in making curd from milk.
2. Some fix atmospheric nitrogen in the soil, as symbionts in legumes.
3. Some of them produce antibiotics.
4. Many are decomposers and help to get rid of organic wastes (garbage).

Lichens growing on rocks secrete organic acids like oxalic acid. The acids enter the rock and produce a number of honey comb-like small crevices. Dust and organic matter collect in the crevices. Mass spores are able to grow over such crevices and start the process of succession and soil formation.

Types of lichens are:

1. Crustose (crust-like).
2. Foliose (flat and lobed-like).
3. Fruticose (branched-like a bush).

Euglena is a taxonomic puzzle since, it shows both plant and animal characters. Absence of cell wall is an animal feature and presence of chloroplast is a plant character of Euglena. It have mixotrophic nutrition. In the presence of sunlight, it can photosynthesise its food and in the absence of sunlight, it behaves like a heterotroph by predating on other smaller organisms.

Lichens are industrially important in the following ways:

1. They are used to make perfumes and soaps.
2. They are used to obtain alcohol after brewing and distillation.
3. Their absence in the environment indicates air pollution.
4. They are used to create medicines to various lung diseases and hydrophobia.

HIV has two single RNA strands in its nucleoid. Reverse transcriptase enzyme catalyses the formation of DNA from RNA. It is found in some RNA viruses called retroviruses, e.g., HIV

1. They lack a cell wall.
2. They are the smallest living cells.
3. They can survive without oxygen.
4. They are pathogenic, i.e. cause diseases in plants and animals.

Malarial parasite Plasmodium has following two hosts:

1. Female Anopheles mosquito: It is a primary host of malarial parasite. The sexual phase of parasite occurs in mosquito.
2. Human beings: These are intermediate or secondary host of Plasmodium. The asexual phase of parasite occurs in humans.

1. Photosynthetic Protists - Dinoflagellata, Euglenophyta, Chrysophyta
2. Chrysophyta

1. Red rot: Colletotrichum falcatum.
2. Early blight: Alternaria solani.
3. Wilts: Fusarium oxysporum.
4. Brown leaf spot of rice: Helminthosporium oryzae.

Nucleus is not well defined in prokaryotes, which means that genetic materials are not enclosed in a capsule. Nucleus is well defined in eukaryotes, which means that genetic materials are enclosed in a capsule.

Cynobacteria, also known as 'blue green algae' help in carbon fixation in a major way on the ocean surface. They are helpful in nitrogen fixation in paddy fields leading to a better harvest. About 80% of photosynthesis on ocean surface is done by cynobacteria. So, it can be said that they play a major role in our ecology.

Protozoans take in water in bulk. As they mostly live in aquatic environments. They are highly likely to burst due to excessive intake of water. Therefore, protozoans need to osmoregulate continuously to keep only the required amount of water in their cells. They get rid of excess water through contractile vacuoles.

Locomotion in protists occurs by flagella, cilia, pseudopodia, wriggling to cells and by mucilage secretion. Flagella: In euglenoids, dinoflagellates ans zooflagellates. Pseudopodia: In Amoeba and slime moulds.

1.  

1. The intervening condition, is a dikaryon.
2. It is the dikaryophase.

2.  

1. Lichens.
2. Mycorrhizae.

R.H. Whittaker. The kingdoms are:

1. Monera.
2. Protista.
3. Fungi.
4. Plantae.
5. Animalia.

Ernst Haeckel in 1866 proposed three kingdom system of classification, i.e., Plantae, Protista and Animalia. The new kingdom was Protista that included the organisms that lack the capability of tissue differentiation.

It means 'infectious living fluid'. M.W. Beijerinek gave this idea.

Slime moulds possess the characters of both animals and fungi. Therefore, they are commonly called fungus animals. Modern biologists called them protistan fungi. They are like Protozoa in their amoeboid plasmodial stage and similar to true fungi in spore formation. Examples Physarum, Physarella, Fuligo, Lycogala and Tubifera.

The following observable features in Trypanosoma would make us classify it under the kingdom Protista.

1. Unicellular.
2. Well defined nucleus.
3. Membrane bound organelles.
4. The presence of Flagella.

Unicellular nature: These are unicellular eukaryotic organisms. Some of them also form colonies. Here, the individual cells do not lose their independent identity. Body organization: Cellular differentiation is absent. Organisation is protoplasmic or acellular.

Bacterial viruses or bacteriophages (viruses that infect the bacteria) are usually double stranded DNA viruses. The bacteriophage enters its nuclear content inside the nucleus of bacteria. As a result the bacteria nucleus starts behaving like a virus and replicates more such viruses.

The common name "pea' is an English word and this can have different names in different languages. It is easier to remember a standard scientific name as compared to so many names. Hence, instead of using simple common names; it is preferred to use scientific names which may appear complicated but universally accepted.

The two kingdom system of classification of living organisms was proposed by Linnaeus. He divided organisms into two kingdoms-Animalia (including all animals) and Plantae (including all plants).

1. Aplanospores, zoospores, conidia.
2. Oospores, zygospores, ascospores, basidiospores.

S.No.	Zygospore	Sporangiospore
1.	This is produced after asexual formed for reproduction.	These are the spores sexual reproduction.
2.	Zygospore is thick walled.	Sporangiospore is thinwalled.
3.	They undergo a period of dormancy.	They germinate without any period of dormancy.
4.	Zygospore is multi-nucleate and diploid.	Sporangiospore is uni-nucleate and haploid.

S.No.	Euglenoids	Chrysophytes
1.	They have no cell wall but pellicle.	They have a cell wall.
2.	They show mixotrophic nutrition.	They are photoautotrophs.
3.	They have flagella for locomotion.	They are planktons and have no flagella.
4.	They occur in stagnant freshwater.	They are freshwater and marine.

• The sex organs are absent and sexual reproduction is by somatogamy. Plasmogamy is effected by the fusion of two vegetative/ somatic cells of different strains or genotypes.
• It results in a dikaryon, which ultimately becomes the basidium.
• Karyogamy and meiosis occur in the basidium, l resulting in the production of four basidiospores, that are cut off exogenously on the basidium.
• The basidia become arranged into fruiting bodies,called basidiocarps.

1. Phycomycetes.
2. Rhizrpus.
3. Albugo, Plasmcpora.
4. Mita shows awareness, consciousness and alertness.

Trichoderma, is a soil fungus used in biological control of other fungi as it produces allelochemicals against them. If this fungus happens to pass into human alimentary canal, it produces leukopenia called alimentary canal aleukia.

• It is because, when the sexual stage is identified, it is shifted to ascomycetes or basidiomycetes.
• It is also possible that the vegetative and asexual stages have been given a name and placed under Deuteromycetes and the sexual stage is given another name and placed under a different class.

Cyanobacteria evolved more than three million years back. They are the self-contained photosynthetic organisms. They can, therefore, live under any type of environment and on any of substrate. Because of this, they are one of the earliest colonisers of barren areas.

Causative agents of the following diseases are:

• Tuberculosis: Mycobacterium tuberculosis.
• Leprosy: Mycobacterium leprae.
• Diphtheria: Corynebacterium diphtheriae.
• Pneumonia: Diplococcus pneumoniae.

1. Nutrition: It is photosynthetic or autotrophic. Some forms are saprotrophic, parasitic and symbionts.
2. Locomotion: Dinoflagellates show rolling and spinning type of locomotion due to the presence of two flagella. Hence, they are also called whirling whips.
3. Reproduction: It occurs by asexual and sexual methods. Asexual reproduction occurs by cell division, spores and cysts. Sexual reproduction occurs by conjugation.

Lichens are the pioneer organisms in the new terrains which colonise bare rocks, mountains and cliffs. They corrode the rocks and accumulate a certain amount of minerals and organic matter. The plants like mossess and grasses appear later in succession, utilising the first soil formed by lichens. Lichens thus, can convert a barren area into one that can support vegetation.

• Lichens are composite organisms showing symbiosis between an alga and a fungus.
• The algal component (phycobiont) is autotrophic and prepares food for the fungus too.
• The fungal component (mycobiont) is heterotropic and absorbs water and mineral nutrients for the alga and also provides protection to the alga.
• Thus, both the alga and fungus are mutually benefitted.

1. Euglenoids have no cell wall but a protein rich layer, called pellicle that makes their bodyflexible.
2. They have two flagella (one short and one long) at their anterior end. They are photosynthetic in the presence of light, but are heterotrophs (predators) in the absence of light.
3. The pigments of euglenoids are identical to the pigments of higher plants.

S.No.	Gametophyte	Sporophyte
1.	It is the haploid phase in the life cycle	It is the diploid phase in the life cycle
2.	It reproduces sexually by the formation of and gives rise to the sporophyte.	It reproduces asexually by the formation of gametes and gives rise spores to the gametophyte.

Bracket or shelf fungi arelignocolous fungi which produce bracket or shelf-shaped, hard, leathery basidiocarps that are found to come out from the tree trunk on loss of wood, e.g., Fomes tomentarius, etc.

1. The morphology of the mycelium.
2. Mode of spore formation.
3. Mode of sexual reproduction, and
4. Nature of fruiting bodies.

• Plasmodium is the aggregation.
• During unfavourable conditions, it differentiates to form fruiting bodies that bear spores at their tips.
• The spores have a true wall and are extremely resistant and survive for many years under adverse conditions.
• The spores are dispersed by wind.

Cyanobacteria have the following harmful effects:

1. They discolour the walls and roofs of buildings.
2. Excessive growth in water bodies decreases oxygen levels, thereby killing aquatic animals.

Deuteromycetes are called imperfect fungi because only asexual or vegetative phase of them is known; there is no sexual/ perfect stage of these fungi.Their mycelium is:

1. septate.
2. branched.

Mumps, influenza (flu), chicken pox, AIDS, Herpes, Hepatitis.

Cell wall is present in bacteria, while cell wall is absent in protozoa. Some bacteria can be autotrophs, while all protozoans are heterotrophs.

Organisms like diatoms and desmids are called chrysophytes. They are found in both marine and freshwater and constitute the major phytoplanktons. Therefore, they are the chief producers in the ocean.

1. Leaf mosaics
2. Leaf curling and rolling
3. Yellowing and vein clearing
4. Dwarfing and stunted growth.

S.No.	Dinoflagellates	Euglenoids
1.	they have a cell wall with stiff cellulosic plates on the outer surface.	They have no cell wall, but pellicle, which gives shape and flexibility to body.
2.	They are mostly found in stagnant water.	They are freshwater forms marine.
3.	They are always photoautophotoautotrophic.	They may be trophic or heterotrophic and predaceous in the absence of sunlight.
4.	They have two flagella, one lies transversely and the other longitudinally.	They have two flagella, both anterior in position but one is very short and one is long.

Mesosomes help in invagination of the membranes. Large septal mesosomes occur near centre of the cell and smaller lateral mesosomes away from the centre. Septal mesosomes help in cell division and lateral mesosomes assist in the reproduction of bacterial DNA chromosome.

S. No.	Mycobiont	Phycobiont
i.	This is the part of lichen composed of fungal part.	This is the part of lichen composed flat of algal part.
ii.	Mycobiont is dependent on algae for nutrition.	Phycobiont makes its own food.
iii.	Mycobiont is attached to the substratum.	Phycobiont is not attached to the substratum.

Methanogens are a type of bacteria which live in the gut of ruminating animals. They assist those animals in digestion and the byproduct of that digestive process is methane. More number of livestock population results in increased methane level in the environment leading to global warming. So, indirectly methanogens can be responsible for global warming.

Zooflagellates like Trichonympha and Lophomonas live as a symbiont in the intestine of termites and wood roaches, respectively. They secrete cellulose digesting enzymes which convert cellulose into glucose. The digested food (glucose) is shared by both zooflagellates and the hosts.