Transcript Natural Selection

Natural Selection
EQ: How does natural
selection lead to
evolution?
1. What was Darwin’s reasoning?
1. Plants and animals that arrived on the
Galapagos faced environmental factors
that were different from the mainland.
2. Species gradually changed over many
generations and became better adapted
to the new environment.
2. What is evolution?
• The gradual change in a species over a
long period of time
3. What is a species?
• A group of similar organisms that can
mate and produce fertile offspring.
4. What is selective breeding?
• The practice by which humans select
plants or animals for breeding based on
desired traits.
• Ex: dogs
If we could achieve these
differences in a few
hundred years, what is
possible in millions of
years?
5. What is natural selection?
• The process in which individuals that are better
adapted to their environment are more likely to
survive and reproduce than other members of
the same species.
• Also known as “survival of the fittest”
6. What factors affect the
process of natural selection?
1. Overproduction:
(more organisms are born
than will survive)
2. Variation:
(each individual has its own
unique set of traits; similar
but not the same)
6. What factors affect the
process of natural selection?
3. Competition
[or Struggle to survive]
(species compete for food,
space, and other resources)
4. Selection
(organisms that are best
suited to their environment
will survive)
6. What factors affect the
process of natural selection?
5. Survival and
Successful
Reproduction
( the survivors reproduce
and pass along their
beneficial traits)
7. Can natural selection lead to
change?
• YES! Over a long period of time natural
selection can lead to change.
• Helpful variations increase while harmful
variations decrease.
• Nature “selects” characteristics.
8. What are environmental
factors?
• Things in the environment that can affect
an organism’s ability to survive.
• Ex: predators and food supply
9. What about genetic variation?
• Individuals need to be different for natural
selection to work, otherwise, all individuals
would have an equal chance of survival!
• Only traits that are inherited, or controlled
by genes, can be acted upon by natural
selection.
1. Overproduction
• organisms produce more offspring than
can survive.
• Ex: too many sea turtles!
2. Variation
• Each individual has its own unique
combination of traits. Similar but not
identical.
• Ex: some turtles are faster than others
3. Competition (Struggle to Survive)
• Some may get caught by predators or
starve or get disease. Only some make
it to adulthood.
• Ex: not enough food + predators
4. Selection
• Turtles that are best adapted to their
environment are likely to have many
offspring that survive.
11. Example of natural selection:
• Peppered moth
variation: black form and white form
environment: trees in England