Download Evolution of Species

Evolution of
Species
7.3
Read and Discuss
This is what we should know by
the end of this section
 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?
Review
 What
 In
is selective breeding?
natural selection, what determines
which organisms reproduce and pass on
their traits?
A
person who is breeding the organisms
 The
environment
Over time, different environments and
genetic variations have produced, through
natural selection, the variety of organisms
that exist today
A Variety of Species
1.
Different environments – the habitat is
the environment that one needs to live
and reproduce
2. Genetic Diversity• Organisms of the same species have
variations and different traits
• Many species have a lot of variety in their
gene pool
• Example: humans
• Some species have very similar gene
pools
• Example: cheetahs
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
 Species get separated from one another
 Example: Grand Canyon squirrels
Inferring Species Relationships
Similarities in DNA
 Comparing the sequence of nitrogen
bases in DNA (A,T, C, G)
 More similar = more closely related
Combining Evidence
 Use evidence from the development of
the animal, anatomy, and DNA
Extinction of Species
Extinction and the Environment
Extinction is 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.
Climate Change
• Can destroy the organisms habitat
Example: woolly mammoth
Adaptation and survival
• Some organisms will still survive
• Example: horseshoe crabs have been here
before the dinosaurs
Now that we have read and took notes, please
write a 4-5 sentence summary using the
following words
• Habitat
• Species
• Extinction