1. Evolution of Biodiversity Readings Evolution
Chapter 5
Evolution of Biodiversity
Readings
Evolution

3. Species Diversity
Ecosystem  species (# species in an area)  genetic diversity (within a population)
We have classified 2 million species, but there is an estimated 10 million
Species richness is the number of species in a given area (pond, tree canopy)
Species evenness looks at individual proportions of species to see which are numerically dominant
High species evenness if all species are represented equally
Human development often disturb both of these

6. Creating Genetic Diversity
Biodiversity results from evolution, the change in genetic composition of a population over time
Genes from a cell determine all possible traits of an organism (physical or behavioral)
Complete set of genes is called the genotype. Phenotype is actual set of traits in an individual (what individual actually looks like)
Two processes that create genetic diversity
Mutations – DNA copies it self millions of times as cells divide. Occasionally there is a mistake.
Mutations can hurt organisms (often die before born) or they can help organisms (mutation that makes an insect less vulnerable to insecticides)
Recombination – Chromosomes are duplicated during reproductive cell division and a piece can break off and attach to another chromosome
Does not create new genes, but creates new combinations of traits
Might combine to give humans new immune system
Mutations can be caused by UV light or certain chemicals

8. Evolution by Artificial Selection
Three main way evolution occurs: artificial selection, natural selection, and random process
Artificial selection is when humans determine which individuals will breed
All dogs came from the gray wolf
Most crops artificially selected
Can lead to resistance (bacteria, pesticides)
Natural selection is survival of the fittest
Recombination and mutations give members of the same species different traits, some which may help them survive
Traits get passed on and determine ability to survive and reproduce
Adaptations are behavior changes

11. Evolution by Random Process
Evolution by random process occurs in 4-ways:
Mutation – mutation can arise in a population and increase over time as it mates
Genetic drift – when genotypes are lost by chance (mouse population of 5 has 4 black mice and 1 white mouse. If that white mouse finds no one to mate with, the white mouse population will disappear)
Bottleneck effect – when a population is reduced, some genotypes are lost. Harder to survive because less helpful mutations available
Founder effect – when a small number of individuals determine characteristics of future generations (two birds get blown off course and end up on a new island. The future generations depend 100% on their traits)

13. Allopatric vs Sympatric Speciation
Geographic isolation can lead to evolution
If two habitats have different conditions, different phenotypes will be favored among the same species (new island, lake split, volcano)
Eventually they become so different, they can’t breed. Called reproductive isolation
The whole process of geographic isolation leading to reproductive isolation is called allopatric speciation (Darwin’s finches)
New islands, continents moving, rivers forming
Each population gets its own set of mutations
Sympatric speciation is when one species evolves into two without geographic isolation
Feed in different areas, mate in different seasons

15. The Pace of Evolution
Evolution can take from hundreds to millions years
Factors that affect rate of change
Rate of environmental change (faster change = less evolution)
Genetic variation - more phenotypes which means quicker evolution (more genetic variation = more evolution)
Population size – large populations means more genetic diversity, but a mutation in a small population can spread more quickly (smaller population equals more diversity)
Generation time – quicker species becomes reproductively mature, the quicker they evolve (more generations over short period of time)
We can genetically engineer to get the traits we desire

18. HUMAN IMPACTS ON TERRESTRIAL BIODIVERSITY
We have depleted and degraded some of the earth’s biodiversity and these threats are expected to increase.

19. Niches
Range of tolerance is the limit of abiotic factors an organism can tolerate (temp, salinity, pH)
The further away from ideal conditions, the less of an organism you may find
Beyond the range of tolerance, organisms will die
The fundamental niche is the combination of ideal abiotic conditions
Biotic conditions can further limit a niche (competitors, predators, diseases)
Realized niche is based on the combination of biotic and abiotic factors
Generalists have broad niche
Specialists have a narrow niche

22. Environmental Change and Species Distribution and Extinction
Environmental changes change species distribution (last ice age to present)
Try to predict distribution of future species as climate changes
Most species can’t adapt to significant changes for three major reasons
No favorable environment to move to (polar bear)
May be too much competition in new env
Environmental changes may happen to quickly
Avg lifespan for a species is 1-10 million
99% of the species ever on this planet are extinct

24. Mass Extinctions 5 mass extinctions have occurred
Last one (dinosaurs) occurred because meteor
We are currently experiencing the sixth major extinction. Because of human activity
Habitat destruction, overharvesting, invasive species, climate change, and emerging disease

26. Causes and consequences of biodiversity loss