Darwin and Natural Selection: Evolution

Contributed by:

kevin Mon, Jan 24, 2022 10:29 AM UTC

The process whereby organisms better adapted to their environment tends to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as to be the main process that brings about evolution.

1. Darwin & Natural
Selection
Unit 6: Evolution
Chapter 15

2. Learning Goals
 1. Define "Evolution" & "Natural Selection".
 2. Describe the 4 steps of Natural Selection,
giving an example of each.
 3. Explain the importance of "Variation".
 4. Does Natural Selection act on an
organism phenotype or genotoype? Explain!
 5. List the 5 evidences that support the
Theory of Evolution.

3. Theory of Evolution
Evolution
 Evolution: The process of change
over time
 Specifically, a change in the frequency
of a gene or allele in a population over
time

4. Charles Darwin
 Father of Evolution
 Proposed a mechanism for
evolution, natural selection
 Darwin went on a 5-year trip
around the world on the ship,
the HMS Beagle
 As the ship’s naturalist, he
made observations of
organisms in South America
and the Galapagos Islands
•Wrote a book, “Origin of the Species”

6. Darwin’s Finches

7. Natural Selection
 Natural Selection: Organisms that are
best adapted to an environment survive
and reproduce more than others

8.  Darwin’s Theory of Natural Selection
occurs in four steps:
 Overproduction
 Variation
 Competition
 Selection

9. 1. Overproduction
 Each species produces more
offspring that can survive

10. 2. Variation
 Each individual has a
unique combination of
inherited traits.
 Adaptation: an inherited
trait that increases an
organism’s chances of
survival

11. What adaptations do you see?

12. What adaptations do you see?

13.

14. Why is Variation
 Because the environment changes.
 The more variation within a species,
species the
more likely it will survive
 EX: If everyone is the same, they are all
vulnerable to the same environmental
changes or diseases
 The more variation of types of species in
an habitat, the more likely at least some
will survive
 EX: Dinosaurs replaced by mammals

15. Which community
community has
has aa better
better
chance of
of surviving
surviving a
a natural
natural
Community A Community B

16. Peppered Moth A
 Which moth will the bird catch?
B

17. 3. Competition
 Individuals COMPETE for limited
resources:
 Food, water, space, mates
 Natural selection occurs through
“Survival of the fittest”
fittest
 Fitness:
Fitness the ability to survive long enough to
reproduce
 Not all individuals survive to adulthood

18. 4. Selection
 The individuals with the best traits /
adaptations will survive and have the
opportunity to pass on it’s traits to
offspring.
 Natural selection acts on the phenotype
(physical appearance), not the genotype
(genetic makeup)
 Ex: When a predator finds its prey, it is due
to the prey’s physical characteristics, like
color or slow speed, not the alleles (BB, Bb)

19.  Individuals with traits that are not
well suited to their environment
either die or leave few offspring.
 Evolution occurs when good traits
build up in a population over many
generations and bad traits are
eliminated by the death of the
individuals.
individuals

20. Descent with
 Descent with Modification – each
living species has descended, with
changes, from other species over
time.
 Common Descent – all living
organisms are related to one another

21.

22. Evidence of Evolution
Learner Outcomes
 I can explain the evidence that supports
evolution.

23. Evidence for Evolution:
 Fossil Record
 Homologous Body Structures
 Vestigial Organs
 Embryology
 Biochemical Evidence

24. The Fossil Record
 Fossils:
Fossils a record of the history of life
on Earth

25.  Missing link between
reptiles and birds

26.

27. Homologous Body
 Homologous
Body Structures:
Structures
similar anatomy in
different types of
animals because
of common
ancestor

28.

29. Vestigial Organs
 Vestigial Organs: “leftover” traces of
evolution that serve no purpose

30.

31.  Embryology:
Embryology embryos of all
vertebrates are very similar early on

32.

33. Biochemical Evidence
 Biochemistry:
Biochemistry DNA with more similar
sequences suggest species are more
closely related
 EX: Humans and chimpanzees share
more than 98% of identical DNA
sequences

34. Learning Goals
 1. Define "Evolution" & "Natural Selection".
 2. Describe the 4 steps of Natural Selection,
giving an example of each.
 3. Explain the importance of "Variation".
 4. Does Natural Selection act on an
organism phenotype or genotoype? Explain!
 5. List the 5 evidences that support the
Theory of Evolution.

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