Transcript Natural Selection

Warm ups:
1. We have many species currently living that are
so rare or otherwise threatened that they may
soon disappear.
What term is used to refer to these animals?
a. endangered
b. exotic
c. extinct
d. Beloved
Natural Selection Notes
OBJECTIVE:
You will be able to explain how natural
selection works
Natural Selection
Notes
“How the changes in the
environment can bring
about changes in species”
1. Artificial selection – breeding animals
and plants for certain characteristics
2. Darwin explains evolution
a. 1858 Darwin writes “The Origin of Species”,
explains evolution through the theory of
NATURAL SELECTION.
b. Natural selection –individuals that are
better adapted to their environment = more
likely to survive and reproduce than other
members of the same species. (“Survival
of the Fittest”)
c. Four steps to natural selection!!
NATURAL SELECTION
Step 1: OVERPRODUCTION – each species
makes more offspring than will survive
NATURAL SELECTION
Step 2 – GENETIC VARIATION –
Any difference between individuals of the same
species
- some traits help, some hurt them.
- Some variations are helpful = adaptation
Step 2 – GENETIC VARIATION
Not everyone is identical
a. Different genes = different traits
b. Fast swimmers, better camouflage
NATURAL SELECTION
Step 3: STRUGGLE TO SURVIVE - COMPETITION
– A natural environment doesn’t have enough
resources for everyone, so only some
individuals survive to adulthood.
Step 3 - Competition:
Usually indirect – no actual physical fights
Not enough food, not be able to escape from
predators
Only strong organisms will survive long enough to
reproduce
NATURAL SELECTION
Step 4: SUCCESSFUL REPRODUCTION
– the individuals that are well adapted to the
environment are more likely to survive and
reproduce. Their genes will be passed on.
**Over a long period of time, natural selection
can lead to evolution.**
Peppered moth story
The case of the English peppered moth is an
example of how human actions can affect
natural selection. In the late 1700’s, most
English peppered moths were light gray in
color. The light-colored moths had an
advantage over black peppered moths because
birds could not see them against the light-gray
trees. Natural selection favored the light
colored moths over the black moths.
The industrial revolution began in England in
the late 1700’s. People built factories to
make cloth and other goods. Over time,
smoke form the factories blackened the
trunks of the trees Now the light-colored
moths were easier to see than the black
ones. As a result, birds caught more lightcolored moths. Natural selection favored
the black moths. By about 1850, almost
all the peppered moths were black.
Before Industrial
Revolution
After Industrial
Revolution
The Heike or Oni-gani (“demon spirit” crab, Dorippe japonica),
whose name derives from a Japanese legend. The pattern on
its shell is thought to resemble the face of a Samurai warrior.
Natural or artificial selection? Intentional or accidental?
Sexual Selection (“Darwin’s headache”)
Archaeopteryx,
discovered 1861
Exit Slip
1. Give me an adaptation that rabbits have to
help them survive?
2. What is Natural Selection and who came up
with this theory?
3. How does competition result in Natural
Selection?
4. Give an example of an animal that we have
changed through the process of Artificial
Selection.