The document is a PowerPoint presentation on natural selection and evolution submitted by DLS PG College, Bilaspur. It outlines Charles Darwin's theory, including the four steps of natural selection: overproduction, variation, competition, and selection, as well as evidence supporting the theory of evolution such as the fossil record and homologous structures. The presentation emphasizes the importance of variation for survival and describes how natural selection acts on phenotypes.

1. Power point presentation
Submitted by :-
DLS PG College, Bilaspur
Topic – Natural selection
Chetna Yadav
M.sc.(Zoology),3rd
sem.
Submitted to:-
Mrs. SUNITA DWIVEDI
Session- 2022-23

2. Darwin & Natural Selection
Darwin & Natural Selection

3. INTRODUCTION:-
Natural selection is the process
through which populations of
living organisms adapt and
change. Individuals in a
population are naturally variable,
meaning that they are all different
in some ways. This variation
means that some individuals
have traits better suited to the
environment than others.

4. 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.

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

6. Charles Darwin
Charles Darwin
 Father of Evolution
 Proposed a mechanism for
evolution, natural selection
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, “
Wrote a book, “Origin of the Species
Origin of the Species”
”

8. Darwin’s Finches

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

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

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

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

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

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

15. 4. Selection
4. Selection
 The individuals with the best traits /
best traits /
adaptations will survive and have the
adaptations will survive and have the
opportunity to pass on it’s traits
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)

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

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

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

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

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

22. Archaeopteryx
 Missing link between
reptiles and birds

23. Biogeography

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

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

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

30. Biochemical Evidence
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

31. REFERENCES:-