BIOLOGY 2 Marks Questions

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.