CIE iGCSE Co-Ordinated Science B15.4 Sexual reproduction in humans Exam Style Questions Paper 3
Question
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B15.1 — Asexual reproduction (Part (a))
• Topic B15.2 — Sexual reproduction (Part (a))
• Topic B15.4 — Sexual reproduction in humans (Part (b))
• Topic B15.3 — Sexual reproduction in plants (Part (c))
▶️ Answer/Explanation
(a)
Asexual reproduction involves only one parent and produces offspring that are genetically identical to each other and to the parent (clones). Sexual reproduction involves two parents, each contributing genetic material through gametes, resulting in offspring that are genetically different from one another and from both parents. This genetic variation arises from the fusion of male and female gametes during fertilisation.
(b)
produces sperm = C (testes)
secretes a fluid to make semen = B (prostate gland)
deposits semen into the female = E (penis)
The testes are the male gonads where sperm are produced by meiosis. The prostate gland secretes an alkaline fluid that nourishes and protects sperm, forming part of semen. The penis is the copulatory organ that transfers semen into the female reproductive tract during sexual intercourse.
(c)
Pollination is the transfer of pollen grains from an anther to a stigma.
Fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule.
Pollination must occur before fertilisation can take place, and it can happen via wind or insects depending on the plant species. Once a pollen grain lands on the stigma, it grows a pollen tube down through the style to reach the ovule, allowing the male nucleus to fuse with the female nucleus inside.
Question
carries urine and semen ………………………………
produces sperm ………………………………
transfers sperm to the urethra. ………………………………
Sperm cells are 0.05 mm in length.
Female gametes are 0.1 mm in length.
Respiration releases the ……………………………… needed for cell division and movement.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B15.4 — Sexual reproduction in humans (Parts (a), (b), (d))
• Topic B12.1 — Respiration (Part (c))
▶️ Answer/Explanation
(a)(i) carries urine and semen = B; produces sperm = D; transfers sperm to urethra = A
The urethra (B) is the shared tube for urine and semen.
The testis (D) is the site of sperm production.
The sperm duct (A) carries sperm from the testis to the urethra.
(a)(ii) X drawn on the prostate gland (the structure labelled E, below the bladder)
The prostate gland surrounds the urethra just below the bladder.
It adds fluid to semen to nourish and help transport sperm.
(b)(i) egg cell / ovum
The female gamete in humans is called the egg cell, ovum, or oocyte.
(b)(ii) 2 times
Using \( \dfrac{0.1}{0.05} = 2 \).
So the female gamete is twice as long as the male gamete.
(c)(i) glucose + oxygen → carbon dioxide + water
Aerobic respiration requires oxygen to fully break down glucose.
The products are carbon dioxide and water, with energy released.
(c)(ii) energy
Respiration releases the energy needed for cell division (mitosis/meiosis) and for the movement of the flagellum/tail of the sperm.
(d) Fusion of the nucleus of the sperm with the nucleus of the egg cell; this occurs in the oviduct
Fertilisation is the fusion of the male gamete (sperm) nucleus with the female gamete (egg) nucleus.
This forms a single diploid nucleus in the resulting zygote.
In humans, fertilisation takes place in the oviduct (fallopian tube).