1. Evolution and Biodiversity
Unit 3
Evolution and Biodiversity

2. What explains how life has changed over time?
According to scientific evidence the major force of adaptation to changes in environmental conditions is biological evolution
Charles Darwin and Alfred Wallace proposed the concept of natural selection as the mechanism for biological evolution

3. Natural Selection and Evolution
Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.
Three conditions are necessary for biological evolution:
Genetic variability
Trait must be heritable
Trait must lead to differential reproduction. (More viable offspring)

5. Gene Pools
Genetic variation may arise through micro-evolution of a population’s gene pool.
The gene pool consists of all the alleles (Copies of genes) in all the individuals making up a population which acts as the reservoir from which the next generation draws its genes

6. Mechanisms of Microevolution
There are four processes that can change the composition of a gene pool
Mutation (change in DNA)
Natural Selection (3 major types)
Gene flow (immigration, emmigration)
Genetic Drift

7. Mutation
Random changes in the genetic structure or number of DNA molecules in a cell is the ultimate source of genetic variability in a population.

8. Natural Selection
When some individuals of a population have genetically based traits that cause them to survive and produce more offspring than other individuals
There are three types of selection that will shift a populations gene frequencies.
Directional
Disruptive
Stabilizing

9. Three Types of Selection
Directional-Changes in the environment cause allele frequencies to shift so that individuals with traits at one end of the normal range become more common

10. Three Types of Selection
Disruptive-Environmental conditions favor the individuals at the extreme ends of genetic spectrum

11. Three Types of Selection
Stabilizing-Conditions favor the average genetic makeup

12. Genetic Drift
Another way gene pools can change is due to genetic drift
Genetic drift is the change of a small population due to chance not specific selection
Two situations can shrink populations down to a size where genetic drift has a greater impact
Bottleneck Effect-Disasters, such as earthquakes, floods, droughts and fires reduce the size of a population
The Founder effect- When a few individuals colonize an isolated island, lake, or some new habitat

14. Limits on Adaptation through Natural Selection
A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.
Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

15. Common Myths about Evolution through Natural Selection
Evolution through natural selection is about the most descendants.
Organisms do not develop certain traits because they need them.
There is no such thing as genetic perfection.

16. Biodiversity
One important renewable resource is biodiversity: The different life forms and life sustaining processes
Biodiversity has four main components
Species Diversity
Genetic Diversity
Ecological Diversity
Functional Diversity

17. Species Diversity
The number and abundance of species present in different communities

18. Genetic Diversity
The variety of genetic material within a species or population

19. Ecological Diversity
The variety of ecosystems found on an area or on earth

20. Functional Diversity
The biological and chemical processes such as energy flow and matter recycling needed for the survival of living things.

21. Why Should We Care About Biodiversity?
Biodiversity provides us with:
Natural Resources (food water, wood, energy, and medicines)
Natural Services (air and water purification, soil fertility, waste disposal, pest control)
Aesthetic pleasure

22. Biodiversity of the Past
Fossil Evidence, chemical analysis, Ice Core samples, and DNA analysis demonstrate that the biodiversity today is different from the biodiversity in the past
Figure 4-4