1. (a) Where are sperms produced in mammals?
(b)(i) In what part of the body does fertilisation occur in a mammal.
(ii) Give the name of a vertebrate with external fertilisation.
(c) In what way are the nuclei of gametes different from the nuclei of other body cells?
(d) What is the fertilised ovum called?
(e) What type of nuclear division occurs when the fertilised ovum begins to divide into many cells?
(f) In what organ does the developing mammalian embryo grow?
(g) Write a short account of the nutrition of the mammalian embryo using the following terms: umbilical cords, placenta, capillary, amino acids.
2. Figure 2.1 is a diagram of a developing mammalian fetus and part of the uterus wall.
(a) On the diagram, label structure A, B and C.
(b) State the function of R.
(c)What type of tissue is found in S?
(d) Figure 2.2 shows a section through structure B taken at P-Q.
(i) On the diagram label W and X.
(ii) With reference to structures W and X, state how they are involved in the nutrition, excretion and gas exchange of fetus.
1. (a) Testes of male
(b) (i) In the oviduct of the female
(c) The nuclei of gametes have only one set of chromosomes, while the other body cells have two sets.
(g) Amino acids in the maternal blood spaces diffuse into the capillaries in the placenta. From these capillaries, the amino acids are carried to the embryo via the umbilical vein in the umbilical cord.
2. (a) A – Amnion
B – Umbilical cord
C – Placenta
(b) Acts as a shock absorber
(c) smooth muscle tissue
(d) (i) W – Umbilical artery
X – Umbilical vein
(ii) Nutrition: Dissolved food molecules e.g. glucose and amino acids are carried from the placenta to the fetus via X
Excretion: Waste products e.g. urea are carried from the fetus to the placenta via W.
Gas exchange: Oxygen is brought to the fetus from the placenta via X while carbon dioxide is carried away from the fetus to the placenta.