6.2 Causes Of Variation

6.2 Causes of Variation

Causes of variation •

Two main factors: 1. Genetic factors 2. Environmental factors

1. Genetic factors • Influenced by crossing-over, independent assortment, mutation and random fertilisation

Crossing over, independent assortment and fertilisation.

Genetic variation caused by mutation • • 1. 2. • 1. 2. 3.

Mutation – sudden permanent change in the nucleotide sequence of the DNA or in the amount of DNA. Two types: Gene mutation Chromosome mutation Mutation can cause by: Chemical or physical agents (mutagens) Mistakes that occur during DNA replication Uneven distribution of the chromosomes during cell division

2. Environmental factors • Caused by surrounding condition such as: 1.Water 2.Sunlight 3.Nutrients 4.pH 5.Temperature • The effect depends on how much condition received by an organism during growth

• E.g. - Chinese primrose (Primula sinensis) will produce white flower when grow in a warm temperature and will produce red flower when grow in cool temperature.

• Environmentally induced cannot be passed to offspring but genetic variation can be inherited • Some variation in characteristics results from interaction between genetic and environmental factors • E.g. the action of sunlight on genes for lighted-coloured skin may result in darker skin

What are the importance of variation in the survival of a species?

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Provides the necessary adaptations for the species to compete and survive. Essential for survival of the species.

Exercise Do Checkpoint 6.2 on page 202 in the textbook