Reproduction in Animals

Reproduction is the production of new individuals of the same kind, and it ensures the continuation of a species. Animals reproduce in two ways. In sexual reproduction, male and female gametes fuse. In this chapter you will study the human male reproductive organs (testes, sperm ducts and penis) and female reproductive organs (ovaries, oviducts and uterus), the structure of a sperm and an egg, and fertilisation, the fusion of a sperm and an egg to form a zygote. Fertilisation is internal in humans, cows and hens but external in frogs and fish. The zygote divides to form an embryo, which in humans develops into a foetus in the uterus. You will learn the difference between viviparous animals, which give birth to young ones, and oviparous animals, which lay eggs, and study metamorphosis in the frog and the silkworm. You will also study asexual reproduction by budding in Hydra and binary fission in Amoeba, and cloning, through which Dolly the sheep was produced in 1996.

Detailed Worksheet: Reproduction in Animals Section A - Definitions (10 marks) 1. Distinguish between sexual and asexual reproduction, giving one example of each. (2 marks) 2. Define gametes, fertilisation and zygote. (2 marks) 3. Distinguish between internal and external fertilisation, giving two examples of each. (2 marks) 4. Define viviparous and oviparous animals, giving two examples of each. (2 marks) 5. What is metamorphosis? Name two animals that show metamorphosis. (2 marks) Section B - Calculations and Applications (15 marks) 6. An Amoeba divides into two by binary fission every 24 hours under favourable conditions. Starting with one Amoeba, how many Amoebae will be present after 5 days? Why is this type of reproduction called asexual? (3 marks) 7. A female frog lays about 2000 eggs at a time in a pond. If only 5% of the eggs develop into adult frogs, how many adult frogs result? Explain why frogs and fish lay such a large number of eggs. (3 marks) 8. In humans, an ovary releases one egg about every 28 days. Taking 1 year as 365 days, about how many eggs are released in a year? Compare this with the millions of sperms produced by a male, and explain why so many sperms are produced. (3 marks) 9. A hen's egg needs about 21 days of incubation for the chick to hatch. If eggs are placed in an incubator on 3 March, on which date will the chicks hatch? Why must the eggs be kept warm during this period? (3 marks) 10. Classify the following as viviparous or oviparous: cow, hen, frog, dog, lizard, human, butterfly, cat. Give one reason why we do not find the young ones of a hen inside her body. (3 marks) Section C - Diagrams (10 marks) 11. Draw neat labelled diagrams of the human male and female reproductive organs. (4 marks) 12. Draw a labelled diagram of a human sperm showing its head, middle piece and tail, and an egg. State one function of the tail of the sperm. (3 marks) 13. Draw a labelled diagram showing budding in Hydra or binary fission in Amoeba. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Draw a flowchart and explain the life cycle of a frog from egg to adult. Explain why the eggs of a frog are surrounded by a layer of jelly, and why this change in form is called metamorphosis. (5 marks) 15. Explain how Dolly the sheep was produced by cloning. Why did Dolly look like the sheep that gave the nucleus and not like the sheep that gave the egg? Why is cloning considered a form of asexual reproduction? (5 marks) 16. What are "test-tube babies"? Explain IVF in simple terms and why it is used. Is the baby actually grown in a test tube? Explain why fertilisation is internal in land animals like humans and hens. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every part clearly.