Read the explanations given below and name the structures: (a) The canal through which the testes descend down into the scrotum just before the birth of a male baby. (b) The part of the brain that regulates the peristaltic movement of the alimentary canal. (c) A structure that collects the soundwaves and conducts them through the external auditory canal. (d) The point of attachment of two chromatids of a chromosome. (e) Regulation of the opening and closing of stomata.

Mention the two pairs of nitrogenous bases which pair with each other with hydrogen bonds.

Differentiate between Mitosis in plant cell and animal cell based on Cytokinesis.

Duplicated chromosomes are joined at a point termed: (a) Centrosome (b) Centromere (c) Centriole (d) Chromatid

A male gorilla has 48 chromosomes in each body cell. How many chromosomes will be present in each of its sperms? (a) 24 (b) 48 (c) 12 (d) 16

Draw a neat, labelled diagram of an animal cell showing the Prophase stage of Mitosis with four chromosomes.

Draw a neat, labelled diagram of an animal cell showing Metaphase with four chromosomes.

What is the structure of DNA as proposed by Watson and Crick?

Expand the abbreviation — DNA.

Differentiate between Karyokinesis and Cytokinesis.

Name the following: (i) The organelle that forms the aster during cell division. (ii) A genetic disorder in which the blood does not clot. (iii) The permanent stoppage of menstruation in human females around the age of 45 years. (iv) The openings on the barks of trees through which transpiration occurs. (v) A gaseous plant hormone which promotes ripening of fruits.

Mention the two pairs of nitrogenous bases that are present in a DNA strand and pair with each other by hydrogen bonds.