Evolution

Lesson

Part 1 — which traits can be passed on, and how populations change until new species arise. (This chapter is assessed through school-based activities and projects, not the board theory paper.)

In this lesson you will

Distinguish acquired traits from inherited traits with examples
Explain how natural selection changes a population over generations
Explain genetic drift and how it differs from natural selection
Explain how geographical isolation, genetic drift and natural selection lead to new species

Concept

What evolution is, and what it is not

Evolution is the change in the inherited characteristics of a population over many generations. Individuals grow and change during their lives, but only populations evolve.

Table of three situations, only one of which, an inherited change in a mosquito population over generations, is evolution
Situation	Is it evolution?	Why
A child grows taller every year	No	Change in one individual’s lifetime
A cricketer’s arms become strong with practice	No	Not passed on through DNA
Over 40 years, most mosquitoes in a town survive an insecticide	Yes	Inherited change in a population over generations

Concept

Acquired and inherited traits

An acquired trait develops during an individual’s lifetime, through use, training, injury or surroundings. An inherited trait comes from the DNA received from the parents. Only inherited traits are passed on.

Table comparing acquired and inherited traits: how they arise, whether they change germ-cell DNA, whether they are passed on, and examples
	Acquired trait	Inherited trait
How it arises	During an individual’s life, through use, training, injury or surroundings	From the DNA received from the parents
Changes the DNA of germ cells?	No	It is in the DNA
Passed to offspring?	No	Yes
Examples	Strong muscles from exercise, a scar, a language learnt, a trimmed tail	Blood group, natural eye colour, flower colour in peas

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