Download Mechanisms of Evolution

Mechanisms of Evolution
a. Species: a group of organisms that can interbreed and produce
fertile offspring
b. Population: a group of interbreeding species occupying a
particular area
c. Evolution is simply a change in the frequency of genes in a
population.
Evolution occurs by Natural Selection. Natural selection states:
1. More organisms are born than can survive.
2. Resources are limited, so there is competition for those
resources.
3. Organisms with favorable adaptations (characteristics) to a
particular environment survive and leave more offspring than
those without favorable adaptations.
*variations exist within a species; some adaptations are advantageous to
survival so those with the variation can survive & reproduce
What results is a change in the frequency of genes in a populationEvolution.
Conceptually, there are two types of evolution.
Microevolution- change in gene frequencies within a population over time
Macroevolution- tells us how species of higher levels of classification are
related to one another
Changes in the frequency of genes in a population can be characterized by
three types of selection:
What kind of selection favors medium sized spiders?
What kind of selection favors large spiders?
What kind favors large and small spiders?
What kind of selection favors small spiders?
Changes in the frequency of genes may result from a number of different
scenarios.
How could migration change the frequency of genes in a population?
How could isolation change the frequency of genes in a population?
How could mutation change the frequency of genes in a population?
Patterns of evolution
Divergent evolution: individuals become more and more different from
the common ancestor as they adapt to different environments
Convergent evolution: different species adapt to similar environments and
develop similar characteristics
Mimicry: a species may develop a favorable adaptation by “mimicking”
another type of species
Choose the term which best fits each example.
1. Polar bears evolved from a group of brown bears that became
geographically isolated in the north. A polar bear’s white coat helps it to
blend in on the ice as it hunts sea mammals.
2. The orangutan line split off first. The gorilla and chimpanzee lines
split later.
3. The swordfish is a fish, the beaked whale is a mammal, and the
ichthyosaur is an extinct reptile. All three show adaptations to an aquatic
life.
4. The climate of an area becomes colder, and most of the thin coated
rabbits die.
5. A species of nonpoisonous snake has evolved to look almost exactly
like the brilliantly colored poisonous coral snake.
6. A river changes course, dividing a population of ground squirrels and
forming a barrier that keeps the two groups from mating.
7. A species of sparrow becomes established on a newly formed volcanic
island. After 50,000 years this one species had evolved into several
different species.