1. Organisms
and
change over time.

2. Helpful vocabulary reminders!
Species – A group of similar organisms that can mate and produce offspring.
Examples and Non-examples:
Birds belong to different species and do not mate between species. A hawk and a robin will not mate to produce a new kind of bird.
All dogs are the same species and can interbreed to form new or mixed ones.

3. Adaptation -
A trait that helps
an organism survive
and reproduce.

4. Finches on the isolated islands of the Galapagos developed different beaks because of the food they ate. They adapted to the food sources available. F

5. Natural selection -
individuals that are better adapted to survive in an environment are able to live to reproduce and pass on their genetic material.
Adaptation and natural selection occur
together as organisms change over time.
Click here to watch a video segment on natural selection

6. What factors affect how natural selection works?
Overproduction – species produce more offspring than the environment can hold
Competition – offspring must compete for resources. Those that succeed, live to pass on genetic information.
Variations – offspring always differ from each other. Sometimes these variations help individuals be more successful.
The successful variations accumulate over many generations which causes the species to change over time.

7. An example of changes in a population over time.

8. Peppered Moths of England – Natural Selection
Before the industrial revolution in Britain most peppered moths were of the pale variety that were well camouflaged against the pale birch trees that they like to sit on. Moths with the mutant black coloring were easily spotted and eaten by birds - giving the white peppered variety an advantage.
Then the industrial revolution came along in the 19th century. Airborne pollution in industrial areas darkened the birch tree bark with soot, and now the mutant black-peppered moths blended better against the darkened bark, while the white variety became much more vulnerable to predators. Over time the mutated black peppered moths were naturally selected to survive and became far more numerous in urban areas than the pale variety.

9. Extinction:
Many organisms
that cannot adapt to
a changing
environment
disappear from
Earth.

10. Many organisms have gone extinct!
Of all the species that have ever lived on earth, 99.9% have gone extinct.
Think of all the species we now have on earth. Those make up only 0.1% of all the species that have ever been on earth.
This is why many new species are discovered each year by digging fossils!
Scientists estimate that we are now loosing about 27,000 species a year.

11. of changes occurring with
Fossil evidence shows
scientists
many examples
of changes occurring with
species over time.

12. Homologous structures – same structure, different function.
The forearms from a
cat, bat, whale and
human are used
for entirely different
things (walking, flying,
swimming, grasping)
and yet they all
have the exact same
bones, just arranged
differently and with
slight changes in shapes.
Homologous structures – same structure, different function.

13. Branching tree -
a diagram that
explains how
scientists think
different species
are related.

14. Branching
tree
Scientists look at DNA to determine how closely related different species are.

15. Fossils show changes in horses during the past 50 million years.
Notice the
branching
tree to the
left.

16. Evolution
is defined as the
gradual change in a
species over time.

17. From dinosaur to birds.