Transcript Evidence Supporting The Theory of Evolution

The Theory of Evolution
Evolution – changes in a population over time
2 views of evolution
• Microevolution
– Small changes over SHORT periods of time
– Supports improvements in existing species
• Macroevolution
– Small changes accumulating over LONG periods of
time result in major changes
– Supports the formation of new species
3 types of evolution:
1.Divergent –
similar organisms
become increasingly
different because of
different types of
environments
3 types of evolution:
2. Convergent different organisms
become increasingly
similar because of
similar types of
environments
3 types of evolution:
3. Coevolution two nonrelated
species change
because of the close
interaction
ex. predator/prey
ex. plant/pollinator
Cladogram
• Diagram showing evolutionary relationships
based on similar characteristics
• Usually shows divergent evolution
Which are more related?
crocs and rabbits
or
crocs and birds
Which organism is the
most “primitive” (evolved
earliest)?
What causes evolution to happen?
1.NATURAL SELECTION***
(“survival of the fittest”)
Development of the
Natural Selection Theory
• 1700s – Lamarck was the
first person to state that
organisms change over
time and that new
organisms are modified
descendants of older
organisms (with his theory
of acquired traits)
Development of the
Natural Selection Theory
• 1800s – Charles Darwin sailed on the H.M.S.
Beagle and gathered data from organisms
(fossils, finches, etc.)
• From this data, Darwin
inferred that all species
had descended from
one or few original types
of life
• Darwin also concluded
that the way
species/organisms
change over time was by
natural selection
The Process of Natural Selection
There must be variation in the traits of a
population. (This variation is caused by
organisms having different genes.)
The Process of Natural Selection
There must be environmental pressures that
favor one variation of the trait over the other.
The Process of Natural Selection
• Organisms with the better traits will survive
better and longer, reproduce, and pass those
good traits on to their offspring.
The result will be
a population
better suited for
the environment.
What causes evolution to happen?
2. Geographic isolation
• organisms of a population
can become isolated from
one another by a geographic
barrier
• if they are no longer able to
reproduce, they may become
two separate species
• the formation of a new
species is called speciation
What causes evolution to happen?
3. Artificial Selection
• Humans cause evolution
to happen because we
“choose” which traits to
select for
• Examples:
– Breeding dogs to have
desirable traits
– Genetic engineering