1. Lecture #30: POPULATION & EVOLUTION
Ms. Day
Honors Biology

2. Population & Evolution
Group of the same species living in the same place at the same time that can interbred
Species:
a group of populations whose individuals can to interbreed and produce living offspring that can reproduce themselves
Gene pool:
ALL of the genes (alleles) in a population at any one time

3. “Individuals are selected, but populations evolve.”
Populations = smallest unit of evolution

4. Causes of Microevolution
A change in the gene pool of a population over many generations
There are 5 reasons why populations can evolve.

5. How can this happen? Genetic Drift
#1: Small Populations
How can this happen? Genetic Drift
Genetic drift: changes in the gene pool of a SMALL population due to chance (reduces genetic variability)
2nd to last video

6. Genetic Drift Example #1
Bottleneck Effect
Caused by a natural disaster
Leaves surviving population with less genetic variation than original population

7. Ex: NORTHERN ELEPHANT SEAL

8. Genetic Drift Example #2
Founder Effect:
a result of colonization by a few individuals from a parent population finding a new place to live

9. Cause #2: Migration of Alleles
Gene Flow:
alleles/genes migrate (move) between populations (reduces differences between populations)

10. Cause #3: Mutations a change in an organism’s DNA
original source of genetic variation (raw material for natural selection)
Mutations can immediately lead to NEW variation in a population

11. Cause #4: “Picky” Mating
Nonrandom mating
“picky” mating
Unequal chances of each egg getting fertilized
Assortative mating - choosing individuals more like self

12. Sexual Selection results in sexual dimorphism
differences between the sexes in secondary sexual characteristics

13. Cause #5: Natural Selection
Different survival and reproductive success due to variation

14. LIGHT/DARK ROCK HABITAT MEDIUM COLOR ROCK HABITAT