Struggle for existence. Natural selection
Answers are for parents and teachers.
1
Compare natural and artificial selection in a table (selector, aim, result).
Natural: the environment, survival of the organism, adaptation; artificial: humans, human benefit, breeds and varieties.
2
What kind of struggle occurs in densely sown wheat and how does a farmer reduce it?
Competition within the species (light, water, nutrients); choosing the proper sowing rate and thinning.
3
Of 1 000 bacterial cells, 50 are resistant. What percent are resistant? (Number only.)
5
4
Explain the difference between stabilising and directional selection with an example.
Stabilising: after a storm average-winged birds survive; directional: in a sooty environment the share of dark moths rises.
5
Why are predators needed for an ecosystem?
They control the number of prey, remove sick and weak individuals and prevent overpopulation.