Transport in Plants — BIOLOGY STD 11 Science — Question

While examining the mitotic stage in a tissue, one finds some cells with 16 chromosomes and some with 32 chromosomes. What possible reasons could you assign to this difference in chromosome number. Do you think cells with 16 chromosomes could have arisen from cells with 32 chromosomes or vice versa?

Which one of the following statements is incorrect?

1. In cockroaches and prawns excretion of waste material occurs through malpighian tubules.
2. In ctenophores, locomotion is mediated by comb plates.
3. In Fasciola, flame cells help in excretion.
4. Earthworms are hermaphrodites and yet cross fertilization take place among them.

In the figure of Sigmoid growth curve given below, label segments 1, 2 and 3.

Highlight the contribution of Succus entericus in the digestion of (a) proteins and (b) disaccharides.

What is the difference between fibrous roots and adventitious roots?

Name the stages of cell division at which the following events occur:

1. Chromosomes cluster at opposite spindle poles.
2. Centromere splits and chromatids separate.
3. Chromosomes move to spindle equator.
4. Crossing over between non-sister chromatids takes place.

Name the type of cells that line the inner surface of PCT. Bring out the role of PCT in a human body.

The flow of impulse in a nerve is unidirectional. Give reason.

Mitosis results in producing two cells are similar to other. What would be the consequence if the following irregularities occur during mitosis? Cytokinesis does not occur.

Define a taxon. Give some examples of taxa at different hierarchical levels.