(a) Fig. 2.1 is a diagram of the female reproductive system in humans.
Table 2.1 shows some of the functions of the female reproductive system.
Complete Table 2.1 by writing the letters from Fig. 2.1 to show which structure is responsible for each function.
(b) Complete the sentences about fertilisation.
Fertilisation occurs when the …………… of two gametes fuse.
The fertilised egg cell is called a?
(c) Fig. 2.2 shows the changes in the thickness of the uterus lining in one menstrual cycle in a human.
Using the information in Fig. 2.2:
(i) State the days of the menstrual cycle when the uterus lining is lost.
(ii) State the days of the menstrual cycle when the uterus lining is thickest.
(d) State the name and describe the role of a hormone produced in the testes.
▶️ Answer/Explanation
(a)
1st row: G (Ovary – produces eggs and hormones)
2nd row: F (Oviduct/Fallopian tube – site of fertilisation)
3rd row: C (Uterus – implantation and development of embryo)
The ovary (G) produces eggs, the oviduct (F) is where fertilisation occurs, and the uterus (C) supports embryo development.
(b)
Fertilisation occurs when the nuclei of two gametes fuse.
The fertilised egg cell is called a zygote.
During fertilisation, the nuclei of sperm and egg fuse to form a diploid zygote, which undergoes mitosis to form an embryo.
(c)
(i) The uterus lining is lost from day 1 to day 8 (menstruation phase).
(ii) The lining is thickest from day 22 to day 28 (luteal phase).
Menstruation occurs early in the cycle (days 1–8), while the lining thickens post-ovulation (days 22–28) to prepare for potential pregnancy.
(d)
Name: Testosterone
Role: Regulates puberty, develops secondary sexual characteristics (e.g., facial hair, deep voice).
Testosterone is the primary male sex hormone, responsible for male traits and sperm production.
Fig. 4.1 is a diagram of part of the human male reproductive system.
(a) Identify the letter in Fig. 4.1 for the structure that:
- produces sperm,
- places sperm into the vagina,
- carries urine out of the body,
- holds the testes outside the body.
(b) Scientists investigated the link between testis size and length of sperm in bird species. Fig. 4.2 shows the results.
Using the information shown in Fig. 4.2:
(i) Describe how the length of the sperm changes as the testis size increases.
(ii) Calculate the difference in length between the longest sperm and the shortest sperm.
(iii) State the testis size that has the longest sperm.
▶️ Answer/Explanation
(a)
Ans: U; S/T; T; R
Explanation: In the male reproductive system, the testes (U) produce sperm, the penis (S/T) places sperm into the vagina, the urethra (T) carries urine out of the body, and the scrotum (R) holds the testes outside the body.
(b)
(i) Ans: It increases and then decreases.
Explanation: The graph shows that sperm length rises as testis size increases up to a certain point (6 arbitrary units) and then declines.
(ii) Ans: 58 µm
Explanation: The longest sperm is ~90 µm (at testis size 6), and the shortest is ~32 µm (at testis size 1). The difference is \(90 – 32 = 58\) µm.
(iii) Ans: 6 arbitrary units
Explanation: The peak sperm length occurs when the testis size is 6 arbitrary units, as seen in Fig. 4.2.