Reproduction and Variation. By the end of the lesson, you should be able to: Describe asexual...

Reproduction and Variation

LEARNING OUTCOMES

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.

TYPES OF REPRODUCTION

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

ASEXUAL REPRODUCTION IN PLANTS

BULBS

Onions Daffodils

Look at the examples of asexual reproduction.

Can you give a definition of the process?

TUBERS

Potatoes

RHIZOMES

Iris

RUNNERS

Strawberry Spider plant

ASEXUAL REPRODUCTION

• 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

Advantages Disadvantages

Asexual ReproductionSexual Reproduction

ASEXUAL 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.

SEXUAL REPRODUCTION

• 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?

Gender Weight Hair length

Height Tattoo Eye colour

Hair colour Tongue-rolling Shoe size

Why is variation in a population important?

SEXUAL REPRODUCTION IN PLANTS

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

Pollen grains

FRUIT OR VEGETABLE?

• 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

SUMMARY

• Fruits always come from a ______.

• Fruits are made through ______ reproduction!

flower

sexual