1. Evolution

2. is the process of biological change by which descendants come to
Evolution
is the process of biological change
by which descendants come to
differ from their ancestors.
This change is the
result of mutations

3. Darwin was struck by the variation of traits
between species of finches in the Galapagos Islands.
The most striking difference
among them are their beaks.

4. Their beak shapes seemed well suited to their diets.
These observations led Darwin to realize that species may
somehow be able to adapt to their surroundings.
An adaptation is a feature that allows an organism
to better survive in its environment.

5. The Theory of Evolution by Natural Selection

6. Charles Darwin challenged traditional views of a
young Earth inhabited my unchanging species.
Many species of organisms
presently inhabiting Earth are
descendants of ancestral species,
that is, species evolve.
Darwin proposed a reasonable
mechanism explaining how
species evolve by natural selection.

7. Organisms had
more offspring than can ever survive.

8. Populations in nature were also limited by factors
such as food, water, shelter, disease, and predators
…..so organisms struggle to survive
Struggle for existence

9. A population is all the individuals of a species
that live in an area.

10. The individuals in a population vary in their characteristics or traits.
A variation is the difference in a physical trait
of an individual from those of other individuals
in the population.

11. Individuals with the adaptation have greater fitness.
Fitness describes how well an organism can survive
and reproduce in its environment.

12. Individuals with the adaptation will be able to eat more, and produce more offspring.
The adaptation will be inherited by its offspring,
making the offspring better adapted to the environment.

13. Natural Selection
Over generations, the individuals with the adaptation
tend to accumulate in the population.
Natural selection will result in species with adaptations
that are well suited for survival and reproduction
in an environment.

14. More and more individuals in the population
will have the new adaption.
In time, the number of individuals that carry the
favorable adaptation will increase in the population.
Simultaneously, individuals that do not have
the adaptation will die, or produce fewer offspring.
Eventually, the population will consists
only of individuals with the adaptation.
The nature of the population has changed.
Evolution has occurred.

15. Natural selection is a mechanism by which individuals
that have inherited beneficial adaptations produce
more offspring on average than do other individuals.

16. EVIDENCE OF EVOLUTION

17. Fossils provide evidence that
Earth is very old…4.6 billion years old
Life is very old…3.5 billion years old
Life on Earth has changed…evolved

18. Fossils show a pattern of development from early ancestors to modern descendants.

19. The similar features of embryos in very different organisms suggest
evolution from a distant common ancestor.
Fish
Human
They share a
common ancestor!

20. Homologous Structures
Similar arrangement of bones.
limbs that perform very different functions are built from the same kinds of bones.
These animals share a common ancestor.
WHY?

21. Some organisms have similar structures,
however, they are not closely related.
The wings of bats and insects are analogous structures.

22. Analogous structures are structures that perform
a similar function , such as flight,
but did not evolve form a common ancestor.
They do not share
a common ancestor.

23. What is one function of the pelvis? _________________
Aids in locomotion
Pelvis
Lion

24. Why do whales have a pelvis?

25. Whales evolved from
terrestrial ancestors
with four legs.
Snakes evolved
from lizards with
four legs.
The human appendix is a vestigial
structure, reduced from the cecum
of primate ancestors, which was
involved in digestion of significant
plant material.

26. Vestigial Structures Vestigial structure is a remnant of a structure
that served an important function
in the organism’s ancestor.

27. Hind leg bones on a whale fossil
Vestigial
Structure

28. Biological Molecules Species share a more recent ancestor
Fewer amino acid sequence differences means that ….
Species share a more recent ancestor
amino
acid
amino
acid
Protein A
in Humans
amino
acid
amino
acid
Protein A’
in Chimps
amino
acid
amino
acid
Protein A ‘’
in Lemurs

29. All living things use the same genetic code! LET’S ALSO REMEMBER…
TTA codes for Leucine
in bacteria as well as in human.
The most logical explanation
is that all species descended
from a common ancestor.

30. Not closely related TAIL What type of structure is it?
homologous structure
analogous structure
vestigial structure
mammal
fish
Not closely
related
TAIL

31. These bones an example of….. __________________________
Homologous structures
Why are homologous structures important?
____________________________________
They provide evidence of a common ancestor…evolution.

32. Pelvic bones provide support for walking.
Whales have a much reduced pelvic bones.
This is an example of:
Homologous structure
Analogous structure
Vestigial structure

33. What are the sources of genetic variation?
Mutations:
A mutation is a change in the DNA of a cell.
Mutations change genes sometimes resulting
in new phenotypes.
Ex: Blue eyes