Evolution
What role does the environment play in an
organism’s survival, reproduction and evolution?
FOCUS
1. Study each of the living things above.
2. Describe the ecosystem that each lives in.
3. What traits/characteristics do each of the
living things have that make it suited to live
in its ecosystem?
4. Do you think those traits always existed?
Evolution and
Natural Selection
• The processes of evolution have acted to change
earth over time. (1.5 million years to be exact)
• Evolution = change over time.
• Biological Evolution = a change in a population’s
gene pool over time.
• A gene is a sequence of DNA that codes
for a particular trait.
Mechanisms of
Biological Evolution
• Mutation: accidental changes in DNA that can give rise to
genetic variation.
• Migration: movement of individuals in or out of a
population thus removing or adding genetic variation.
• Genetic Drift: biological evolution that occurs by
chance…like a forest fire, hurricane, etc. Certain
individuals are separated and develop separate
characteristics.
• Natural Selection: the process by which traits that
improve an organism’s chances for survival and
reproduction are passed on more frequently to future
generations than those that do not.
1
Mutation:
changes in DNA
that can give rise
to genetic
variation.
3
Genetic Drift: biological
evolution that occurs
by chance…like a forest
fire, hurricane, etc.
2
4
Natural Selection: the process
by which traits that improve an
organism’s chances for survival
and reproduction are passed on
more frequently to future
generations than those that do
not.
Migration:
movement of
individuals in or
out of a
population thus
removing or
adding genetic
variation.
Conditions of
Natural Selection
• Natural selection is a simple concept that offers a
great explanation for how things are in nature.
1. Organisms produce more offspring than can survive.
2. Individuals of a species vary in their characteristics.
3. Individuals vary in their fitness. Fitness = reproductive
success. Adaptations are heritable traits that increases
chances for survival.
•
In 1859, Charles Darwin published, On the Origin
of Species, where he presented the scientific theory
of Natural Selection.
Organisms produce more
offspring than can survive.
Survival of the Fittest
•The fish with the best traits for survival
will live.
•That fish will reproduce, thus creating
more fish with that desirable trait.
•“Fit”ness is defined by the
environment…as it changes, so must the
things living in it. BEST EXAMPLE…as
Earth changed, organisms had to change
with it to survive…or evolve! That
evolution was in response to the changing
world around them!
Individuals vary in
fitness, or reproductive
success.
What is the Difference Between Natural
Selection and Artificial Selection?
Natural Selection
• Environmental
conditions create
variations in organisms.
• Selection occurs
naturally.
• “Survival of the fittest”
Artificial Selection
• Artificial breeding of
organisms to produce
the most desirable
traits.
• The process of selection
conducted under
human direction
• Dogs and plants!
Speciation
• Imagine this…
– 2 islands…pretty close together.
– On each island a specie of squirrel specific to
the island.
– They seem similar, but they have enough
similarities that it seems odd.
– How can they be related? They live in 2
different places and never interact?
Speciation and
Extinction
• Speciation – the process by which new species
are generated. Most often as a result of
geographic isolation.
– Over time led to the creation of many different
species on Earth.
• Extinction – the disappearance of a species
from Earth.
– Occurs when environmental conditions change
rapidly and organisms can’t adapt quickly enough.
– 99% of the species that ever lived are now gone.