Exercises: Asexual and sexual reproduction

Define asexual reproduction and state how many parents are needed.

Match each organism to its method of asexual reproduction: binary fission, budding, runners, spores.

1. a) Strawberry plant

1. b) Yeast

1. c) Bacteria

1. d) Mushroom

State whether the offspring from asexual reproduction are genetically identical to the parent or different from it. Name the term used for a group of genetically identical organisms.

A single bacterium divides by binary fission every $20$ minutes under ideal conditions.

1. a) Calculate how many bacteria there are after $2$ hours, starting from one.

1. b) Explain why this type of reproduction can lead to a rapid spread of infection.

1. c) Name one disadvantage for a population of bacteria of being genetically identical.

Copy and complete the comparison by giving one difference for each point between sexual and asexual reproduction:

1. a) Number of parents

1. b) Gametes

1. c) Genetic variation in offspring

1. d) Speed of reproduction

A gardener in Co. Kilkenny takes cuttings from one apple tree to grow new trees, rather than planting seeds.

1. a) Name this type of reproduction.

1. b) Give one advantage of using cuttings if the parent tree has very tasty apples.

1. c) Explain why the cuttings may all be wiped out by the same disease.

Potatoes were the main food crop in Ireland in the 1840s, and were grown from tubers, which is a form of asexual reproduction. A fungus-like disease devastated the crop.

1. a) Explain why growing potatoes by asexual reproduction made the crop particularly vulnerable.

1. b) Explain how a population produced by sexual reproduction would be more likely to contain survivors.

1. c) Suggest two ways modern farmers reduce this risk.

Some organisms, such as aphids, can reproduce asexually in good conditions and sexually when conditions get harsh.

1. a) Explain the advantage of asexual reproduction in a stable and favourable environment.

1. b) Explain the advantage of sexual reproduction when the environment changes.

1. c) Link your answers to the idea of natural selection.

Dolly the sheep was produced in 1996 by transferring the nucleus of a body cell from an adult sheep into an egg cell whose nucleus had been removed.

1. a) Explain why Dolly was genetically identical to the sheep that donated the nucleus.

1. b) Explain why Dolly is described as a clone but was not produced by fertilisation.

1. c) Discuss two ethical concerns raised by cloning animals or humans.