Genetic and environmental variation, mutations, natural selection, antibiotic resistance, fossils, extinction and how new species form.
What you will learn
- Sort variation into genetic, environmental or both
- Explain natural selection step by step
- Explain how antibiotic resistance spreads and use resistance data
- Describe the evidence for evolution, extinction and speciation (Biology only)
Where variation comes from
Differences between individuals of a species are variation.
Some is genetic (blood group), some is environmental (a scar), and much is both (height, body mass).
Variation that can take any value in a range, such as height, is continuous; variation that falls into separate groups, such as blood group, is discontinuous. Identical twins have the same genes, so differences between them are caused by the environment; non-identical twins differ in genes and environment.
New alleles come from mutations: random changes in DNA that happen all the time. Most have no effect on the phenotype. Very rarely a mutation gives a phenotype that suits the environment, and it can spread quickly through a population.
The rest of this lesson and its 10 practice questions are locked.
In this lesson
- Where variation comes from
- Natural selection
- Evidence, extinction and new species
10 practice questions, marked as you go; about 25 minutes in all.
Key terms
Variation, Genetic, Environmental, Continuous, Discontinuous, Evolution, Natural selection, Antibiotic resistance, Fossils, Extinct
In this unit: Inheritance, variation and evolution
Meiosis and DNA, Punnett squares and family trees, inherited disorders and embryo screening, natural selection, selective breeding, genetic engineering and cloning, and classification.