1. Part 1: The Pace of Evolutionary Change

2. How fast is Evolution?
Evolution does not always occur at the same rate all the time.
Evidence: Looking at the fossil record, it shows some groups of organisms remaining unchanged for millions of years, while others are rapidly changing over time.

4. Gradualism
The pattern of slow and gradual evolutionary change over long periods of time.
Populations slowly diverge from one another due to different selective pressure:
Constant allele frequencies
Constant environmental conditions
Few chromosomal mutations

5. Gradualism
Some examples include:
Cockroaches
Sharks

6. Gradualism
Results from transitional forms that are seen in the fossil record. (Giant Spider – ifls.com)
Example: Trilobites

7. Punctuated Equilibrium
The pattern of long stable periods in which species stayed much the same.
Interrupted (punctuated) by short periods in which there was quick evolution, rapidly resulting in formations of new species.
Some reasons for it include:
Mass extinction of many life forms
Rapidly changing environmental conditions
Exploitation of new environments

8. Punctuated Equilibrium
Some examples include:
Galapagos finches
Cambrian (time period) explosion of animal types

9. Punctuated Equilibrium
The fossil record shows rapid bursts of evolution following mass extinctions.
Cretaceous extinction = Lots of mammals

11. Part 2: Genetic Variation
What causes a population to change?
Part 2: Genetic Variation

12. 1) Mutations constantly occur
Mutations provide the source of new alleles, or variation upon which natural selection can act.
Examples:
Butterfly colour, giraffe’s long necks, rabbits long ears

13. 2) Immigration and Emigration Occur
These both affect allele frequencies and the gene flow in a population.
Examples:
Immigrants come to Canada, thus affecting the gene flow. Immigration affecting phenotype (animals in the wild)

14. 3) Small Populations
Changes have more of an effect on a smaller population.
Examples:
Founder effect: when a small # of individuals from a population wander away to start (found) their own population.
Bottleneck effect: when a population is reduced to low number due to disease, predation, climate change, etc.

17. Founder Effect
See article on Ellis-van Crevald Syndrome

18. 4) Non-Random Mating Occurs
This often produces a change in alleles within populations.
Examples:
Animals’ sexual selection is intrasexual (competition within 1 sex like deer) or intersexual (completion for a mate like peacocks).

20. 5. Natural Selection Occurs
Only the most fit survive and pass their genes on to successive generations.
Therefore, change occurs because the most fit are always being selected for.
Examples:
Finches, peppered moths

21. Hardy-Weinberg Equation
This equation can be used to check if a population is changing.
If the equation is NOT EQUAL to 1, the population is CHANGING
If the equation is EQUAL to 1, the population is in equilibrium