EVOLUTION

Big Picture: Evolution refers to an orderly succession of changes. Biological evolution is the change of populations of organisms over generations. Early scientists studied population of species over time, fossil records and geography to help understand the process of change.

Population and genes? Population – an inter-breeding group of organisms Genes – are passed from generation to generation within a population

Meiosis and fertilization Cause genetic variation within a population

Evolution: history Jean Baptiste Lamarck (1744-1829) – one of the first to propose a theory hypothesizing how species developed modifications over time.

Lamarck – acquired traits Studied extensive fossil record of invertebrates Theorized that similar species descended from a common ancestor Descendents from similar but extinct species Acquired traits – proposed that behaviors caused by environmental factors lead to new and better adapted traits in the next generation of offspring Ex. giraffe’s neck and web-feet of shore birds

Charles Darwin (1809-1882) Alfred Wallace (1823-1913)

NATURAL SELECTION organisms best suited to their environment reproduce more successfully than other organisms therefore their genes and traits get passed along to the next generation

Charles Darwin

Descent with Modification Newer forms of life (including those in the fossil records) are actually modified descendants of older species. The cause for the modification was natural selection – the environment selecting for favored traits over time.

Two major influences on Darwin: Lyell – age of Earth, changes in Earth over time = changes in environments over time Malthus – human populations are maintained due to environmental limits – food, shelter, disease

Darwin’s theory Environmental conditions affect individuals in a population Environment may affect organisms differently because no two individuals are exactly the same (genetic variation)

Some organisms have traits that are favored because they are beneficial – these organisms tend to have a higher success in reproduction so those favorable traits get passed to their offspring

The organisms adapt to their environment because these traits are passed along to the next generation where the proportion of favorable genes has increased Fitness refers to the individual’s contribution to the next generation.

Evolution is… the change in genetic makeup of a population over time. Some genes are favored to be passed along – others not as much

How are certain genes selected for and others not? Selection is based on the individual – so the phenotype of an individual is selected for by nature.

Can an individual evolve over time? NO! – individuals do not change – the genes you have are it! Populations evolve – not individuals!

Evidence for Evolution Fossil Records Embryology Biogeography Homologous and vestigial structures Similarities in macromolecules

Grouping of 5 experts One person will become an expert on one area of evidence. Meet as a group first – then all fossil experts will get together, embryology experts, etc. Once you have gathered sufficient info. You will return to your original group and take turns reporting on the various evidence for evolution – completing the notes.