Question

Describe the four-species symbiosis in leafcutter ants.

What are four mechanisms of vegetative reproduction, for example, tubers

What factors influence the virulence (harmfulness) of cholera?

Answer 1

Leafcutter ants is a non generic name belonging to two genera Atta and Acromyrmex. They are basically tropically growing ants. The show mutualistic association.They cultivate fungus by feeding them with fresh cut plant material and by protecting them from pests. This interaction is further enhanced by another species, namely a bacterium. It grows on the ants and secretes specific chemicals; the ants make use of those substances. Ambrosia based beetles also feed on the fungus. The fungus is also used to feed the larvae of the ants. So the fungus- ants-termites-bacterium are dependant on each other.

Vegetative reproduction is a form of asexual reproduction where the new plants grows from a fragment of a plant or by the use of specialised structures. These include:

• Rhizome which is a modified underground stem. It serves as a unit for propagation. Ex: Polypodium.
• Tubers which are enlarged structures in some plants, also serve as units of propagation. Ex: Potato.
• Stolons which are modified aerial stems are used for propagation in Strawberry.
• Bulbs which are short stems consisting of fleshy leaves are used foor reproduction in onion.

Factors affecting virulence of cholera are Toxin Co-regulated Pilus (TCP) and cholera toxin (CT) which are essential for colonization of host and enterotoxicity. Further, motility is also an important virulence factor which is mediated by flagella. TCP and CT re important for adherence. Cholera toxin is an A-B enterotoxin which causes chloride ions to move out of the cell causing dehydration.