1. Evolution within a species Aims: Must be able to state the observations and subsequent deductions that Darwin and Wallace based their theories on. Should be able to outline the processes involved in evolution within species. Could be able to explain the use of mitochondrial DNA in tracing species evolution.

2. Darwin and Wallace Charles Darwin (1809 – 1882) Alfred Russel Wallace (1823 – 1913) Proposed a theory of evolution based upon natural selection in 1858 The theory was based on 3 Observations and Deductions:

3. Observation 1: In the wild, the number of offspring produced by plants and animals over their lifetime is greater than the number of parents. Deduction: A struggle for survival occurs.

4. Observation 2: Over time, the size of the natural population tends to remain fairly constant. (Fluctuations may occur from time to time due to drought, disease, food supply etc) Deduction: In the struggle to survive, some organisms have a greater chance of survival than others. These variations between organisms are favoured under the conditions in a particular environment and are reproductively more successful.

5. Observation 3: Variation exists in populations of plants and animals; that is no two organisms in a population are identical and some variations are inherited. Deduction: Inherited traits preset in surviving parents are passed on to their offspring so that the genetic composition of populations can change over time

6. Evolution within a species (speciation) Members of one population may be separated into a number of isolated populations. Over time: The separate populations may be exposed to different selecting pressures, Genetic drift may produce different changes in each population Mutation may result in new alleles

7. Species A biological species is: a grouping of organisms that can interbreed and are reproductively isolated from other such groups. Species are recognized on the basis of their morphology (size, shape, and appearance) and, more recently, by genetic analysis. For example, there are up to 20 000 species of butterfly; they are often very different in appearance and do not interbreed.

8. Answer the questions from pages 309 to 310 and 319 to 320 in the Biozone books. Activity

9. Studying populations - mtDNA Mitochondrial DNA (mtDNA) is an important tool for tracing the evolutionary history of a species – including humans… Structurally identical to nuclear DNA (double stranded with complementary base pairing) Why mtDNA?

10. Reasons for mtDNA: 1. mtDNA descents via the maternal line: Inherited from the mother only. All offspring receive just one kind of mtDNA exclusively from the mother.

11. Three reasons for mtDNA: 2. Lack of recombination mtDNA passes unchanged from a female parent to all of her offspring (i.e.: no recombination as can occur during meiosis). 3. High copy number Each mitochondrion contains 2 to 10 mtDNA molecules and each cell has several hundred mitochondria… so many copies of mtDNA (and genes that it carries) are present in each cell. In contrast to only two copies of each autosomal chromosome in each somatic cell.

12. mtDNA - population differences Over time, populations that are geographically isolated accumulate mutations in their mtDNA. In the past, human population sizes were small and isolated – and mtDNA mutations began to become established in these groups. Members of an indigenous population in one region are characterized by closely related mtDNA sequences – these sequences differ from those present in members of indigenous populations in other regions. The longer that two populations have been separated the greater the differences in their mtDNA.

13. The distinctive mtDNA sequences found in different populations are known as haplogroups and each designated a capital letter.