Variation
Science: KS3, topic 1.2.15
Natural Selection
Natural selection is the process by which the least-well adapted organisms die. The best-adapted organisms survive, breed and pass their advantageous genes onto the next generation.
Continuous vs discontinuous
- Continuous
- Continuous variation is hard to group, with few extreme examples and most people in the middle.
- Examples are height and weight.
- Continuous data can be shown on a line graph.
Discontinuous variation
- Discontinuous
- Discontinuous variation is easier to group because groups have hard borders and no overlap.
- Examples are sex and blood group.
- Data can be shown on a bar or pie chart.
Why do animals vary?
- Animals within the same species vary from one another.
- Variation happens because animals have slightly different genes.
Cheetah speed
- Not all cheetahs can run at the same speed.
- Some cheetahs are slightly faster and some are slower than others.
- Speed depends on genes that control muscle size and aerodynamic head shape.
Competition
- Because of these differences, or variation, some cheetahs are better adapted to survive.
- Better-adapted cheetahs find it easier to hunt and eat, so they live longer and are more likely to breed.
Passing on genes
- Better-adapted cheetahs that breed pass on the genes that made them good hunters.
- Slower cheetahs do not survive, so they do not pass on genes for slowness or poor aerodynamics.
Population change
- Over time, the cheetah population changes to become better suited to its environment.
Test yourself on Variation
Natural Selection
Which of these are true of natural selection?
Which type of variation can be easily represented on a line graph?
Why does a cheetah population gradually become faster over many generations?