Natural selection of human population

1. Medical Academy named after S.I. Georgievsky of Vernadsky CFU

2.

NATURAL
SELECTION OF
HUMAN POPULATION
REPRESENTED BY :
DHRUV MANGAL
195 b (LA-2)
SUPERVISOR- ANNA ZHUKOVA

3. Darwin’s Theory of Evolution by Natural Selection

4. NATURAL SELECTION

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

5.

6. HOW NATURAL SELECTION WORKS?

To make natural selection more concrete, let's consider a simplified, hypothetical example.
In this example, a group of mice with heritable variation in fur color (black vs. tan) has just
moved into a new area where the rocks are black. This environment features hawks, which
like to eat mice and can see the tan ones more easily than the black ones against the
black rock.
Because the hawks can see and catch the tan mice more easily, a relatively large fraction
of the tan mice are eaten, while a much smaller fraction of the black mice are eaten. If we
look at the ratio of black mice to tan mice in the surviving ("not-eaten") group, it will be
higher than in the starting population.

7. Heritable variation comes from random mutations

The original source of the new gene variants that produce new heritable
traits, such as fur colors, is random mutation (changes in DNA
sequence). Random mutations that are passed on to offspring typically
occur in the germline, or sperm and egg cell lineage, of organisms.
Sexual reproduction "mixes and matches" gene variants to make more
variation.

8.

FACT 1: Individuals in a population vary or differ in
traits. Most of this variation is heritable (passed
from parent to offspring).

9. Variation in Pumpkins

Pumpkin Mass (N=40)
7
Pumpkins
6
5
4
3
2
1
0
Mass (g)

10. Variation in Humans

11. Genetic mutation can produce new variations

Genetic mutations are RANDOM!

12. Sexual (two parent) reproduction “shuffles” existing variations into new combinations

13.

FACT 2: A population of any species has the potential
to produce far more offspring than will survive to
produce offspring of their own.
What are some of the challenges living
things must overcome to survive?

14.

Inference 1: Certain inherited variations give some
individuals a better chance to survive in their
environment. Those that survive will produce more
offspring. This is called natural selection.

15.

Inference 2: Each generation will contain a greater
percentage of individuals with these favorable traits
leading to a change in the average characteristics of a
population over time. This is called evolution.

16. Grant Finch Study: state and explain the specific data that supports each postulate in natural selection

Individuals in a
population vary in their
traits
2. Most of this variation is
heritable – passed on to
offspring
3. More offspring are
produced than can
survive (due to limited
resources such as food)
4. Individuals with
advantageous traits are
more likely to survive
and reproduce
1.
Medium Ground Finch
Geospiza fortis

17. The Big Misconception: need-driven evolution

How would Darwin explain how the giraffe’s neck became long?

18. The Big Misconception: need-driven evolution

19. The Big Misconception: need-driven evolution

20. SUMMARY

By biological evolution we mean that many of the organisms that inhabit the Earth today are different from those that inhabited it in the
past.
Natural selection is one of several processes that can bring about evolution, although it can also promote stability rather than change. It
follows that natural selection is not the same thing as evolution.
The four propositions underlying Darwin's theory of evolution through natural selection are: (1) more individuals are produced than can
survive; (2) there is therefore a struggle for existence; (3) individuals within a species show variation; and (4) offspring tend to inherit their
parents' characters.
The three necessary and sufficient conditions for natural selection to occur are: (1) a struggle for existence; (2) variation; and (3)
inheritance.
Endler's experiment with guppies demonstrated that evolution through natural selection can occur in relatively few generations.
Mutation is the ultimate source of variation.
The frequency of a particular character in a particular population may be due to chance events (e.g. the founder effect and/or genetic drift)
rather than to natural selection.