4. Inheritance and selection

4.1 Variation

• Define variation as differences between individuals of the same species.

• Discuss the causes of genetic and environmental variation.

• Describe continuous and discontinuous variation.

• Design and conduct an investigation to measure continuous and discontinuous variation.

• Collect and analyse data, presenting it in the form of tables and graphs.

4.2 Genes, chromosomes and alleles

• Define the term gene as a length of DNA that codes for a protein.

• Define a chromosome as a thread-like structure of DNA, carrying genetic information in the form of genes.

• Describe DNA (deoxyribonucleic acid) as the molecule that makes up genes and chromosomes and carries genetic information inherited from parents.

4.3 Dominant and recessive alleles

• Describe the difference between dominant and recessive alleles.

• Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1:1 and 3:1 ratio.

• Interpret pedigree diagrams for the inheritance of a given characteristic.

• Describe the symptoms of cystic fibrosis and use pedigree diagrams to determine the chances of offspring inheriting disease of parents.

4.4 Selective breeding

• Describe how farmers can use natural selection to increase desirable traits in animals.

• Describe how farmers can use natural selection to increase desirable traits in plants.

• Outline the advantages and disadvantages of selective breeding

4.5 Adaptive features

• Describe what is meant by an adaptation and give examples of how animals are adapted to different environments

4.7 Natural selection

• Describe how organisms can adapt to environmental change

• Discuss the work of Darwin in developing the scientific theory of natural selection.

• Discuss how natural selection changes the gene frequencies of a population and leads to adaptation to the environment.