Human reproduction passes life to the next generation. Fertilisation joins a sperm and an egg.
The idea
In the male, the testes produce sperm and the male sex hormone. Sperm travel through the sperm duct. Along the way glands add fluid, and the mixture is semen. The penis deposits semen in the vagina. In the female, the ovaries produce eggs and the female sex hormones. Usually one egg is released at a time. The egg passes into the oviduct, also called the fallopian tube.
Fertilisation is the fusion of the nucleus of a sperm with the nucleus of an egg. It normally happens in the oviduct. The fertilised egg divides as it moves to the uterus, and it implants in the thickened lining. The placenta is the organ of exchange. Food and oxygen pass from the mother to the embryo, and carbon dioxide and other wastes pass back. The blood of the mother and the blood of the embryo do not mix. The umbilical cord joins the embryo to the placenta.
What earns the marks
Use the biological names and the job of each part. Fertilisation is fusion of nuclei, not simply "when the sperm meets the egg", and it happens in the oviduct, not in the uterus. The uterus is where the embryo develops. Do not say the placenta is a filter that mixes the two bloods. At puberty the organs mature and the body becomes able to reproduce. Name two changes rather than one vague sentence.
Practice questions
These are practice questions in the style of the paper, with a model answer and a mark scheme. They are not a promise of what your paper will ask.
1Question 1
4 marks
(a) Define fertilisation. (2 marks)
(b) Name the part of the female reproductive system where fertilisation normally takes place. (1 mark)
(c) Name the organ where the embryo develops. (1 mark)
Model answer
(a) Fertilisation is the fusion of the nucleus of a sperm with the nucleus of an egg.
(b) The oviduct.
(c) The uterus.
Mark scheme
Fusion of nuclei, not merely the meeting of sperm and egg1 mark
Sperm nucleus and egg nucleus both named1 mark
Oviduct or fallopian tube1 mark
Uterus or womb1 mark
2Question 2
6 marks
State two roles of the placenta. (2 marks)
State two changes that occur in boys at puberty and two changes that occur in girls at puberty. (4 marks)
Model answer
The placenta passes food and oxygen to the embryo and removes carbon dioxide and other wastes.
In boys the voice deepens and sperm production begins. In girls the breasts develop and menstruation starts.
Mark scheme
Passes food or oxygen from mother to embryo1 mark
Removes carbon dioxide or wastes from the embryo1 mark
Two male puberty changes, such as deepening voice, growth of hair on the face, broadening shoulders, or start of sperm production. One mark each2 marks
Two female puberty changes, such as breast development, widening hips, or start of menstruation. One mark each2 marks
3Question 3
3 marks
A student wrote that the blood of the mother mixes with the blood of the baby inside the placenta. Explain why that statement is wrong, and name the cord that joins the baby to the placenta. (3 marks)
Model answer
The two bloods do not mix. Materials diffuse across thin membranes in the placenta. The umbilical cord joins the baby to the placenta.
Mark scheme
Maternal and fetal blood do not mix1 mark
Exchange is by diffusion across a membrane or a thin barrier1 mark
Umbilical cord1 mark
Practise Science with Kevin
More questions on this topic are inside GLearn, marked as you answer, with the reason written out. The first ones need no account.
In the oviduct, also called the fallopian tube. The uterus is where the embryo implants and develops. Implantation is not fertilisation.
What does the placenta do?+
It is the exchange surface between the mother and the embryo. Food and oxygen move to the embryo. Carbon dioxide and other wastes move away. The two blood supplies stay separate. All BECE Science past questions