EVOLUTION 1A

1 EJC H2 Biology T4W9 Evolution IA Evolution IA 1. Introduction Charles Darwin’s ideas were published in "On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life" in 1859. Darwin used this concept of natural selection to explain the variation he observed wit hin and between species. It was clear to him that those adaptations which conferred survival advantages in a given environment would come to dominate a population, all else being equal. Darwin never knew or mentioned anything about genes, alleles or muta tions. Neo-Darwinism is the theory of evolution that represents a synthesis of Darwin’s theory in terms of natural selection and modern population genetics. It supports natural selection as the major process that would account for biological evolution. 2. Learning Outcomes (a) Explain why variation (as a result of mutation, meiosis and sexual reproduction) is important in natural selection (b) Explain, with examples, how environmental factors act as forces of natural selection (c) Explain the role of natural selection in evolution (d) Explain why the population is the smallest unit that can evolve (f) Define biological evolution as descent with modification and explain the link between micro-evolution and macro-evolution (h) Explain the various concepts of the species (biological, ecological, morphological, genetic and phylogenetic concepts) (j) Explain how new species are formed with respect to geographical isolation (allopatric speciation) and behavioural or physiological isolation within the same geographical location (sympatric speciation) 3. References Campbell, N.A. and Reece, J.B. (2008). Biology, 9th edition. Pearson. Contents 1. Introduction ............................................................................................................... 1 2. Learning Outcomes.................................................................................................... 1 3. References ................................................................................................................. 1 4. Microevolution & Macroevolution ............................................................................ 2 5. Five Agents of Evolutionary Change .......................................................................... 3 6. Populations Evolve, Not Individuals ........................................................................ 14

2 EJC H2 Biology T4W9 Evolution IA 4. Microevolution & Macroevolution Broadly, biological evolution is defined as descent with modification from a common ancestor: Modification: Evolution only occurs when there are changes in allele frequency within a population over time . (Allele frequency is a measure of the chances of finding a particular allele of a gene within the population.) Descent: Evolution involves passing on of these heritable genetic changes to