Download Other important evolution theory and facts….

Other important evolution
theory and facts….
Darwin’s theory of gradualism..
• Darwin believed that seldom are their drastic
changes in species from one generation to the
next, but they are usually small continuous
changes that accumulate over thousands of
years.
• Population gradualism says that new traits
happen by increasing their frequency through
generations. Initially the trait is a only in a small
fraction of a population and then over time it
becomes a frequent trait.
Gradualism continued..
• Phenotypic gradualism – New traits ONLY
evolve in small incremental steps. This is
still VERY controversial.
• Punctuated Equilibrium – Contradicts the
above theory. It says there are large
changes over small periods, followed by
long periods of no change.
Adaptations
• Adaptations: All developmental,
physiological, anatomical and behavioral
changes to help organisms survive and
reproduce in their environments.
Polar Bear Physical Adaptations
• Polar Bears can survive in temperatures as low as -150
degrees F. Two layers of fur provide the bears with such
good insulation that they experience almost no heat loss.
In addition, they are protected with a layer of blubber that
can measure 11.5 cm (4.5 inches) thick. Compact ears
and a small tail also prevent heat loss.
Other adaptations include small bumps called papillae
that keep their feet from slipping on ice; strong, powerful
claws that enable them to catch seals; and a nose
powerful enough to detect prey that is miles away.
Polar Bear Swimming Adaptations
• Polar bears are strong swimmers. They can
swim for several hours at a time over long
distances. They've been tracked swimming
continuously for 62 mi.
• A thick layer of blubber, up to 4.3 inches thick,
keeps the polar bear warm while swimming in
cold water. A polar bear's nostrils close when
under water diving. They have been seen diving
to depths of over 20 feet.
Behavioral Adaptations
• Polar Bear’s main source of food is the
ringed seal. They wait at breathe holes for
the seals to pop up and grab them by their
head. They will cover their black nose
with snow so they are more camouflaged
when preying upon the seal.
Sorting…and genetic drift
• Sorting is the different survival and
reproduction rates among various
individuals.
• Genetic Drift is the chance fluctuation in
allelic frequency from one generation to
the next; or in English the chance that your
parents traits or relatives traits will be
passed to you and your offspring.
Relative fitness
• The ability of a trait (a genotype of certain
gene) to survive from one generation to
the next. If a genotype has a higher
relative fitness it will be passed down from
one generation to the next.
Macro vs. Micro
• Macro – Large scale events in evolutions.
Drastic changes…
• Micro – Small scale changes that cause
small changes in species.
Mass Extinctions
• Events, which cause large number of
species to go extinct simultaneously.
• The causes are uncertain, perhaps huge
geologic events, meteor strikes, drought,
etc.
• Currently species are going extinct at rate
over 100 greater than the last mass
extinction.