The diagram below shows the appearance of chromosomes during a cell division. Use it to answer question 39.

39. The diagram shows homologous chromosomes paired up with visible points of crossing over, which are called chiasmata. This process occurs during prophase I of meiosis.
The correct option is C.

• C) chiasma formation

40. DNA replication, the process of making an exact copy of DNA, occurs during the S phase of interphase, which precedes both mitosis and meiosis.
The correct option is A.

• A) interphase of mitosis

41. Organisms that excrete uric acid (like birds, reptiles, and insects) do so primarily because it is a highly insoluble waste product that can be excreted with very little water loss, which is crucial for survival in dry environments.
The correct option is C.

• C) is excreted with minimal water loss

42. Homeostasis refers to the body's ability to maintain a stable internal environment despite external changes.
The correct option is C.

• C) maintenance of a steady internal environment of the body

43. The medulla oblongata is a part of the brainstem responsible for regulating vital involuntary functions such as heartbeat, respiration, and blood pressure.
The correct option is D.

• D) medulla oblongata

44. Oestrogen (estrogen) is the primary female sex hormone responsible for the development of female secondary sexual characteristics, such as breast development and widening of hips.
The correct option is A.

• A) oestrogen

45. Imbibition is the process by which solid particles absorb water and swell. This is the primary mechanism by which dry seeds take up water to initiate germination.
The correct option is C.

• C) imbibition

46. The diagram illustrates multiple sperm surrounding an egg, with one sperm appearing to penetrate it. This process, where a sperm fuses with an egg, is called fertilization.
The correct option is B.

• B) fertilization

47. The product of fertilization is a zygote. This zygote then undergoes a series of rapid cell divisions through mitosis (known as cleavage) to form an embryo.
The correct option is A.

• A) undergo mitotic division

48. An earthworm possesses a hydrostatic skeleton, which uses the pressure of fluid within its body cavity to provide support and facilitate movement.
The correct option is B.

• B) earthworm and hydrostatic skeleton