(a)(i) What is placentation?
(ii) Name two organs associated with the human placenta.
(b) State five functions of the human placenta.
(c) Write short notes on the following:
(i) viviparity
(ii) territoriality
(iii) seasonal migration
Explanation
(a)(i) Placentation: This is the arrangement of ovules, within the ovary.
(b) (i) Organs Associated with human
placenta: Umbilical cord, Uterus
(b)(ii) Functions of Placenta:
- Establishes connection between the embryo and the mother.
- Carries oxygen/water/food/ nutrients from mother's blood to foetus.
- Removes waste/urea/salt/carbon dioxide from foetus blood to mother's blood for elimination.
- Produces progesterone/hormone for maintenance of uterine wall/ endometrium/pregnancy.
- Carries antibodies from mother's blood to foetus.
(c) Viviparity: This is a type of reproduction in which the young develops inside the mother's body. Obtaining nutrients directly from the parent. When fully developed, the young are born alive.
(ii) Territoriality: In many animal species individuals, usually males mark out areas/territories where they can live and breed.
- They guard these territories fiercely.
- Chasing away other members of the species.
- Only vigorous individuals are able to establish large territories, secure suitable mates and produce many offspring.
- Territoriality limits overcrowding.
- Animals that carry out this phenomenon are lizards, lions, etc.
(iii) Seasonal migration:
- In many habitats food supply is affected by seasonal changes. Food is abundant in rainy seasons but scarce in dry seasons.
- Animals overcome these seasonal food shortages by moving to other habitats during unfavourable seasons.
- Such large scale seasonal movements of animals between habitats are called migrations.
- Other causes of migrations are temperature changes and breeding seasons.