Download Evolution and Lab 4-4

Change Over Time
Evolution
• A cumulative change in the
characteristics of organisms or
populations from generation to
generation
– Slow process
– Many small changes collect to form a new
species
– Species - group of the same organism,
organisms that can breed together
Charles Darwin
• Observed the main mechanism of
evolution on his travels around the
world.
Natural Selection
Galapagos Islands
• Island chain off the coast of Peru
• Islands vary in terrain and vegetation
• Darwin studied finches on several of the
islands
Galapagos Finches
• Many different
species are found on
the island
– Each finch is well
adapted to their island
habitat
– How? Why?
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• (Potential for) Overpopulation Unchecked reproduction causes
exponential population growth.
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• Competition - for
resources occurs
because resources are
limited (space, clean
water, food, etc…)
– Ex. Predator Prey
relationship
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• Variation with in a
population.
– Some organisms may be…
•
•
•
•
faster or slower,
stronger or weaker,
more resistant to a disease
Blend in with surroundings
better
• Etc.
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• Selection - some variations increase the
chance of survival because they
– Out run a predator
– Hide from a predator
– Find clean water
– Use different food sources
– Etc..
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• Reproduction - organisms that are
selected for survival can pass on their
traits
– Over time the frequency of favorable traits
will increase in the population
Darwin’s Theory of Evolution
by Natural Selection
(OCVSRS)
• Speciation - Process of forming a new
species
– Over time many changes accumulate
– If populations are different enough that
they can no longer mate with each other.
The two populations are considered
different species.