Question

Question 4:

a. Give two examples of invertebrate animals that have different forms or shapes at different points in their life

b. What is pollen? When did it evolve (in what group of plants)? What capability did it give plants?

Answer 1

Invertibrate that have different forms or shape at different points in their life have indirect development or larval form in their life.

Larva stage in development of many animals ,occuring after birth or hatching and before the adult form is reached . This immature ,active form structurally different from adults and adapted to different environment.

EXAMPLE: 1. cnideria have a simple ciliated larva called planula.

Planula ,plural planulae , free- swimming or crawling larva . The planula body is less cylindrical or egg shaped & bear cilia but after metamorphosis to become adult have soft body, with stinging tentacles ,body summetry or attached to substrate.

2. insect larva : the insect lay egg ,the egg hatches into larva.the larva has an enormous appetite and grows . The larva makes itself a hard outer coating and become a pupa inside that coating. During this stage,the pupa undergoes metamorphosis. The last stage is adult. Here the insect feeds and reproduces ( eventually laying eggs.)eg. Butterfly ,beetles.

Ans b. A fine powdery ,typically yellow ,microscopic grain discharge from male part of a flower or male cone ,each grain contain male gamete that can fertilize the female ovule, to which pollen is transported by wind , insect or other animal.

The evolution of seed plant and adaptation for land. The evolution of seeds allowed plant to reproduce independently of water , pollen allows them to disperse their gametes great distances.

Palm trees grow along the shoreline,wheat is a crop grown in most of the world,the flower of the cotton plant produces fibers that are woven into fabric.

The capability give the plant ,pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the sigma of another in cross-pollination . In a case of self-pollination ,this process takes place from the anther of flower to the stigma of same flower.