Variation and Natural Selection Flashcards
What are the 2 types of variation?
Continuous and discontinuous variation.
What is continuous variation, give an example and how would you display it?
It is measured on a scale and gives a range of results.
E.g. Height.
You would display it using a histogram.
What is discontinuous variation, give an example and how would you display it?
In discontinuous variation data gives distinct groups.
E.g. tongue rolling.
You would display it using a bar chart.
What are the 2 sources of variation?
Genes and the environment.
How do genes cause variation?
Genes can determine the characteristics an organism shows. E.g. eye colour, hair colour. Colour differences in these characteristics are caused by sexual reproduction or mutations.
How does the environment cause variation?
The environment can lead to variation between individuals e.g. the height a human grows to will be affected by availability or quality of food.
What is a histogram?
A histogram should show normal distribution, with most individuals around the average value and a few at the extremes.
What conclusions did Charles Darwin make after his observations?
- There is variation among the phenotypes of individuals in a population.
- Competition (for food, mates etc) causes a struggle for existence.
- The best-adapted individuals survive and the less well-adapted individuals do not survive – this is differential survival.
- The surviving phenotype (the fittest) is able to reproduce.
- The surviving phenotype passes its beneficial gene to the next generation.
What is the theory of evolution?
The theory of evolution is a continuing process of natural selection that leads to gradual changes in
organisms over time, which may result in the formation of a new species.
What is extinction?
Extinction of a species over time is a consequence of failure to adapt to environmental change.
E.g. loss of habitat.
What is selective breeding?
People deliberately select particular characteristics in plants and animals that are of use to us.
Why is selective breeding carried out?
For appearance.
Increased crop yield.
Increased crop quality.
Resistance to disease.
What does repeated selective breeding do?
Repeated selection and breeding over many generations causes all the offspring to show the desired characteristic.
