Download The Evolution of Populations

Friday, March 27, 2015
The Evolution of Populations
Patterns in Evolution
- Evolution occurs in patterns.
- Evolution through natural selection is not random.
- Species can shape each other over time.
- Species can become extinct.
- Speciation often occurs in patterns.
- Mutations and genetic drift cannot be predicted, they are called random events.
- These random events are sources of genetic diversity.
- Natural selection, which acts on this diversity, is not random.
- Individuals with traits that are better adapted for their environment have a better
chance of surviving and reproducing than do individuals with these traits.
- Natural selection pushes a population’s traits in an advantageous direction.
- Alleles associated with these traits add up in the population’s gene pool.
- The response of species to environmental challenges and opportunities is not
random.
- Evolution toward similar characteristics in unrelated species is called convergent
evolution.
- Analogous structures are examples of convergent evolution.
- Closely related species evolve in different direction, and become increasingly different
is called divergent evolution.
- The evolution of the red fox and the kit fox is an example of the trend.
- Species interact with each other in many different ways.
- Coevolution is the process in which two or more species evolve in response to
changes in each other.
- Coevolution can also occur in competitive relationships.
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Friday, March 27, 2015
-These
interactions
can lead to
“evolutionary
arms races,”
in which
each
species
responds to
pressure
from the
other
through
better
adaptations over many generations.
- The rise and fall of species are natural processes of evolution.
- The eliminations of a species from Earth is called extinction. Extinction often occurs
when a species as a whole is unable to adapt to a change in its environment.
- Biologists divide extinction events into two categories-background extinction and
mass extinctions. The effects of both are the same: the permanent loss of species
from Earth.
- Extinctions that occur continuously but at a very low rate are called background
extinction.
- Background extinction occur at roughly the same rate as speciation.
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Friday, March 27, 2015
- Background extinction events usually affect only one or a few species in a relatively
small area.
- The can be caused by local changes in the environment.
- Mass extinctions are much more rare than background extinctions.
- But, they are more intense.
- These events often operate at the global level.
- They destroy many species-even entire orders of families.
- Mass extinctions are though to occur suddenly in geologic time, usually because of
catastrophic events such as an ice age or asteroid impact. The fossil record confirms
that there have been at least five mass extinction in the last 600 million years.
- Punctuated equilibrium, which states that episodes of speculation occur suddenly in
geologic time and are followed by long periods of little evolutionary change.
- The diversification of one ancestral species into many descendent species is called
adaptive radiation.
- These descendent species are usually adapted to a wide range of environments.
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