IB Biology Topic 5.4 Evolution

Topics Define evolution Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures State that populations tend to produce more offspring than the environment can support Explain that the consequence of the potential overproduction of offspring is a struggle for survival State that the members of a species show variation

Topics Cont’d Explain how sexual reproduction promotes variation in a species Explain how natural selection leads to evolution Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria

5.4.1 Evolution is the cumulative change in the heritable characteristics of a population.

5.4.2 Fossils show that organisms are not identical but have similarities between each other.

5.4.2 Cont’d elective breeding of domesticated animals also provides this evidence as the domestic breeds have similar characteristics to the wild ones and can still breed with them. As selected wild individuals with desirable characteristics were bred, over time this resulted in a more desirable species from a human point of view.

5.4.2 Cont’d

5.4.3 Populations tend to produce more offspring than the environment can support.

5.4.4 If the mortality rate remains lower than the natality rate then a population will keep growing.

5.4.4 Cont’d If there is an over production of offspring this will result in a struggle for survival within the species as the resources become scarce and individuals in the population will start to compete for these.

3.4.4 Cont’d This results in an increase in mortality rate as the weaker individuals in the population will lose out on these vital resources that are essential for their survival

5.4.5 Members of a species show variation

5.4.6 Sexual reproduction is important for promoting variation as even though mutations form new genes or alleles, sexual reproduction forms a new combination of alleles

5.4.7 During meiosis, a large variety of genetically different gametes are produced by each individual. hill.com/sites/ /student_view0/chapter 11/meiosis_with_crossing_over.html

5.4.7 Individuals in a population differ from each other. Some individuals will have characteristics that make them well adapted to their environment whereas others will have characteristics that make them less adapted to their environment.

5.4.7 This is called natural selection. Natural selection results in the better adapted individuals to pass on their characteristics to more offspring as the lesser adapted ones are more likely to die before they reproduce.