1. Explaining Evolution

2.  Darwin published “On the Origin of Species” in 1859  He had spent 20 years amassing evidence and developing his theory of NATURAL SELECTION

3.  The way in which nature favours the reproductive success of some individuals within a population over others  Over time the population changes as advantageous heritable characteristics become more common generation after generation  Evolution is the result of natural selection occurring over many generations

4.  A term coined by Herbert Spencer to describe the process of natural selection  The key to natural selection is an individual’s REPRODUCTIVE SUCCESS and its ability to ADAPT  ADAPTATION: a characteristic or feature of a species that makes it well suited for reproductive success and survival

5.  Darwin’s theory of evolution by means of natural selection is able to:  Explain how adaptation can arise in a species  Make predictions about the future evolution of a species  Be a testable scientific theory

6.  Evolutionary biology has made tremendous advances since Darwin because of the following:  RADIOMETRIC DATING  MODERN EVOLUTIONARY SYNTHESIS  PALEONTOLOGY

7.  Involves the use of radioisotopes to obtain precise estimates of the ages of rocks  RADIOISOTOPE: an atom with an unstable nucleus that is capable of undergoing radioactive decay  HALF-LIFE: the time required for half the quantity of a radioactive substance to undergo decay; the half-life is constant for any isotope

8.  The modern theory of evolution that takes into account all branches of Biology  Involves changes in the GENE POOL of a species over time  GENE POOL: the complete set of all alleles contained within a species or a population  RECALL: genetic mutations provide a continuous supply of new heritable information and variation within a species

9.  Vestigial genes that no longer code for functioning proteins  Are found in virtually all species  EXAMPLE: Dolphins have genes that code for smell however they have no need for a sense of smell

10.  We have made many important discoveries over the last 100 years:  Fossils of early human ancestors in Pakistan  Feathered dinosaurs in China  PLATE TECTONICS: the scientific theory that describes the large scale movements and features of Earth’s crust  Explains species distributions

11.  There are FOUR types of selection: 1. DIRECTIONAL 2. STABILIZING 3. DISRUPTIVE 4. SEXUAL

12.  A selection that favours an increase or decrease in the value of a trait from the current population average  Common in artificial selection where individuals with an enhanced trait are selected  EXAMPLE: A habitat with long flowers will favour hummingbirds with longer bills, and thus create future generations of birds with longer bills

13.  A selection against individuals exhibiting traits that deviate from the current population average  EXAMPLE: An environment with medium length flowers will select against long billed or short billed hummingbirds

14.  A selection that favours two or more variations of a trait that differ from the current population average  EXAMPLE: An environment with long and short flowers will select against hummingbirds with medium sized bills

15.  The favouring of any trait that specifically enhances the mating success of an individual  Results in males and females of a species differing in behaviour and appearance

16.  EXAMPLE: Polar bears and white fur  Ability to sneak up on seals on snow covered ice  EXAMPLE: Wolves keen sense of smell  Ability to locate and track the movements of prey  EXAMPLE: A human’s large brain  Ability to reason and communicate

17.  Changes to allele frequency as a result of chance  Such changes are much more pronounced in small populations  Can result in the allele becoming very common or disappearing entirely over a number of generations

18.  A dramatic, often temporary reduction in population size  Usually results in significant genetic drift and a loss of genetic diversity  EXAMPLE: Cheetahs

19.  In large populations in which only random chance is at work, allele frequencies are expected to remain constant from generation to generation  Evolution occurs:  If natural selection occurs  In a small population  If there is a mutation  There is immigration or emigration  If there is a gaining of new alleles from a different species

20.  EXAMPLE: Commercial fishing  The alleles that code for large adult sized cod are being lost  EXAMPLE: Insecticide use  Bedbugs are becoming resistant to pesticides  EXAMPLE: Antibiotic and antimicrobial use  Many infectious bacteria (MRSA) are becoming resistant to a variety of antibiotics