Practise selection questions by sequencing natural selection, applying selective breeding steps and explaining antibiotic resistance or artificial-selection differences.
Sickle-cell anaemia is an inherited disease.
Fig. 5.1 is a photomicrograph of some blood cells from a person who has sickle-cell anaemia.
Fig. 5.1
Sickle-cell anaemia is most common in areas of the world where the infectious disease malaria is found.
Some species of the genus Plasmodium cause malaria in humans.
The distribution of sickle-cell anaemia is the result of natural selection.
Explain the distribution of the sickle-cell allele in human populations.
Anthocyanin is a red pigment found in carnation flowers. Some carnation plants have a gene for making anthocyanin.
A flower grower bred red carnations.
Describe how growers selectively breed plants.
Tasmania is an island off the south coast of Australia. Sheep were introduced to Tasmania in the nineteenth century.
Fig. 3.1 shows the population of sheep in Tasmania from 1820 to 1940. The dashed line shows the trend in the population growth.
The sheep that were first introduced to Tasmania were not well adapted to the environment.
Describe how farmers can use selective breeding to improve their sheep so that they are better adapted to the environment.