1. 7.3 Evolution of Species

2. Key Ideas What factors have contributed to the diversity of species?
How do new species form?
How do scientists infer evolutionary relationships among species?
What causes the extinction of species?

3. A Variety of Species
Over time, different environments and genetic variation have produced, through natural selection, the variety of organisms that exist today
Habitat: specific environment that provides the things the organism needs to live, grow, and reproduce

4. Genetic Diversity : organisms within the same species do not all have identical traits.
Some genetic differences, or variations, may result from mutations in DNA or rearrangement of genes during meiosis

5. High variety in gene pools VS. Low variety
All the genetic variations in a species make up the total “gene pool” of that species
High variety in gene pools VS. Low variety
Corn, cheetah

6. How do new species form?
A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits
Geographic isolation – one of the main possible ways new species form.
Kaibab squirrel
Abert’s
squirrel

7. Inferring Species Relationships
Scientists have combined the evidence from DNA, proteins structure, fossils, early development, and body structure to determine the evolutionary relationships among species

8. Elephant and elephant shrew : the mouse-like elephant shrews are more closely related to elephants than rodents based on DNA comparisons.

9. Extinction of Species
Extinct: no members of that species are still alive. (Woolly mammoths)
Extinction if caused by a change in a species’ environment. The members of the species may not have adaptations that allow them to survive and reproduce in the changed environment

10. Climate change : climate change can destroy organisms’ habitats
It has been the leading cause of extinction
Adaptation and survival – environmental change does not always lead to extinction. Some organisms may have traits that help them survive in a changed env.

11. Some Q’s to think about…
What causes extinction?
How can isolation lead to the formation of new species?