PRESENTATION BY PASMAS COFFIE

1. MECHANISMS OF EVOLUTION

2. Natural Selection

3. NATURAL SELECTION
• Natural selection also known as survival of the fittest is the process of maintaining organisms that are best adapted to the
environment.
• Organisms not possessing beneficial traits either die or don’t have many offspring.
PRINCIPLESOF NATURAL SELECTION
• Variation
• Inheritance
• Overproduction
• Competition

4. TYPES OF NATURAL SELECTION
 Directional selection
Stabilizing selection
Diversity / Disruptive selection
Kin selection
Sexual selection

5. Dominance hierarchy

6. GENETIC DRIFT

7. GENETIC DRIFT
GENETIC DRIFT
• Genetic drift is the change in the frequency of an existing
gene variant in a population due to random chance.
• Two forms; Founder Effect and Bottleneck Effect.
CONSEQUENCES
• Random Fixation of alleles
• Loss of heterozygosity
• Variation Among Population increases

8. FOUNDER EFFECT

9. GENETIC DRIFT
Founder effect
• The founder effect is another
extreme example of drift, one
that occurs when a small group
of individuals breaks off from a
larger population to establish a
colony.
• EFFECTS OF FOUNDER EFFECT
• Reduced Diversity
• Change in allele frequency

10. Bottleneck Effect

11. BOTTLENECK EFFECT

12. REFERENCES
Gould SJ (2002). "Chapter 7, section "Synthesis as Hardening"". The Structure of Evolutionary Theory.
Jump up to:a b c Masel J (October 2011). "Genetic drift". Current Biology. Cell Press. 21 (20): R837-
8. doi:10.1016/j.cub.2011.08.007. PMID 22032182.
Star B, Spencer HG (May 2013). "Effects of genetic drift and gene flow on the selective maintenance of genetic
variation". Genetics. 194 (1): 235–44.