Reproduction and Variation

By the end of the lesson, you should be able to:  Describe asexual reproduction.  Describe sexual reproduction.  Explain why sexual reproduction results in variation, but asexual reproduction does not produce variation.  Describe differences in characteristics due to genetic or environmental causes or a combination of both.

There are two very different ways of reproducing: –Asexual reproduction –Sexual reproduction

BULBS Onions Daffodils Look at the examples of asexual reproduction. Can you give a definition of the process? Look at the examples of asexual reproduction. Can you give a definition of the process?

TUBERS Potatoes

RHIZOMES Iris

RUNNERS StrawberrySpider plant

No fusion of gametes. Only one individual is needed as the parent. There is no mixing of genetic information and so no genetic variation in the offspring. These genetically identical individuals are known as clones.

Advantages of Asexual Reproduction AdvantagesDisadvantages Asexual Reproduction Sexual Reproduction

Only involves one parent. Offspring are completely identical to the parent – clones! No gametes (sex cells) are needed. Very safe and easy – no need to find a partner! Common in small/simple animals, plants and bacteria. Also happens in our body all the time – to replace worn out or dead cells. It also happens in some bigger plants.

Involves the joining (fusion) of the male and female gametes (sperm and egg). The mixture of the genetic information from two parents leads to variety in the offspring.

VARIATION Genetic Variation Environmental Variation Which of the following characteristics are the result of genetic variation, environmental variation or both? GenderWeightHair length HeightTattooEye colour Hair colourTongue-rollingShoe size Which of the following characteristics are the result of genetic variation, environmental variation or both? GenderWeightHair length HeightTattooEye colour Hair colourTongue-rollingShoe size Why is variation in a population important?

In plants, the eggs are found in ovules (in the ovary of flowers), and the sperm cells are found in pollen.

Pollen grains

When the flower has been pollinated, the sperms meet the eggs, and seeds form (the offspring!) The ovary turns into the fruit – with seeds inside ready for dispersal. Which of the following are fruits? Vegetables? Are they produced by sexual or asexual reproduction?

VEGETABLE! ASEXUAL

FRUIT ! SEXUAL

FRUIT! SEXUAL

VEGETABLE ! ASEXUAL

FRUIT! SEXUAL

FRUIT! SEXUAL

VEGETABLE! ASEXUAL

Fruits always come from a ______. Fruits are made through ______ reproduction! flower sexual