1. Evolution of Biodiversity
Chapter 5

2. What is biodiversity?
Biodiversity refers to the variety of organisms on Earth
Three different scales:
Ecosystem diversity- the variety of ecosystems within a given region.
Species diversity- the variety of species in a given ecosystem.
Genetic diversity- the variety of genes within a given species.

3. How much biodiversity?
Earth is home to a tremendous diversity of species; current estimates range between million species
1.5 million identified and named so far:
Insects are most diverse group

4. C. Measuring local or regional species biodiversity
Species richness - total number of species in a given area
Species evenness - the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals
Both decline after human disturbance
Knowing values gives environmental scientists baseline to determine change in ecosystems

5. Methods for Estimating Biodiversity
Simpson Index
Shannon-Weiner Index
Sampling
When estimating population size it is important to collect RANDOM SAMPLES.
A sample is a part of a population or part of an area, chosen to illustrate what the whole population or area is like.
In a random sample every individual in a population has an equal chance of being selected
Using quadrats:
Mark out area to be sampled.
Place quadrats ( 1 m2, 10 m2) randomly within the area.
Count how many individuals are inside each of the quadrats.
Calculate the mean number of individuals per quadrat.
Pop. Size = mean X total area area of each quadrat

6. Using Quadrats SYSTEMATIC QUADRATS RANDOM QUADRATS
Quadrat sampling is suitable for plants that do not move around and are easy to find.

7. Knowing population size is important in making environmental decisions that would affect the population.
Making a decision on an estimate that is too high = extinction.
Making a decision on an estimate that is too low = unnecessarily hurt people that depend on the animals for food & income.
Change in the relative abundance of a species over an area or a distance is referred to as an ecological gradient (aka zonation)

8. How Geology and Geography Affect Biologic Diversity
Species are not uniformly distributed over the earth’s surface; diversity varies greatly from place to place
Species and ecosystems on land change with soil type and topography:
Slope, aspect (the direction the slope faces), elevation, and nearness to a drainage basin
These factors influence the number and type of plants, which in turn influences the number and types of animals

9. Biological Evolution
Refers to the change in inherited characteristics of a population from generation to generation
It is the mechanism underlying biodiversity
Microevolution- evolution below the species level (e.g. different varieties of apples or potatoes)
Macroevolution- evolution which gives rise to new species or new genera, family, class or phyla
New species arise as a result of competition for resources and the differences among individuals in their adaptations to environmental conditions

10. Creating Genetic Diversity (two processes)
Mutation
DNA is copied millions of times in an organism’s lifetime as cells divide
Random copying “mistakes” are made = change in genes
“Good” mutations increase the organism’s chance of survival and reproduction, so the mutation is passed on to next generation
Increases population’s genetic diversity
Recombination
Occurs in plant and animal cells during Prophase I (crossing over)
Creates new genetic combinations of genes

11. Evolution by Artificial Selection (two types)
Artificial selection is when humans select which individuals breed to create desired phenotypes
What is genotype and phenotype?

12. Darwin’s Theory of Natural Selection
Individuals produce an excess of offspring.
Not all offspring can survive.
Individuals differ in their traits.
Differences in traits can be passed on from parents to offspring, and are associated with differences in the ability to survive and reproduce.
Natural selection DOES NOT select for specific traits; rather it favors any combo of traits that increases a species fitness
Traits that improve fitness = adaptations

13. Natural Selection

14. Genetic Drift
Change in the genetic composition of a population over time as a result of random mating

15. Bottleneck effect
Reduction in the genetic diversity of a population caused by a reduction in its size.

16. Founder effect
Change in a population descended from a small number of colonizing individuals

17. Random Evolutionary Processes

18. Speciation
Creation of new species
Two types:
Allopatric speciation or when new species are created by geographic reproductive isolation.

19. Sympatric speciation- the evolution of one species into two species in the absence of geographic isolation, usually through the process of polyploidy (an increase in the number of sets of chromosomes)

20. Pace and Patterns of Evolution
Four factors that influence successful adaptation:
Rate of environmental change
Genetic variation
Population size
Generation time
Average global rate of evolution is about one new species every 3 million years

21. B. Evolution shapes ecological niches and determines species distributions
All species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance
Fundamental niche - the ideal conditions for a species.

22. Niche generalist - species that live under a wide range of conditions
Range of abiotic and biotic conditions under which a species lives is its realized niche
Determines the species distribution, or areas of the world where it lives
Niche generalist - species that live under a wide range of conditions
Niche specialist - species that live only in specific habitats.
Some species like insects can live in a very wide range of specialized niches, whereas others can only live in a very narrow range
Meadow spittlebug
2. Skeletonizing leaf beetle

23. C. Environmental Change and Species Distribution
Changes in environmental conditions has an effect on species distribution …How do we know?
Analyze layers of sediment and find different types of pollen at different strata

24. As climate change accelerates, precipitation patterns change, but species niche requirements don’t
Predict species distribution

25. D. Environmental Change and Species Extinction
Average life span of a species is 1-10 million years
About 99% of all species that ever lived on Earth are exticnt
Much of what we know about evolution comes from the fossil record.

26. 4. The Five Global Mass Extinctions
Mass extinction - when large numbers of species went extinct over a relatively short period of time.

27. 5. The Sixth Mass Extinction
Scientists think we are in our sixth mass extinction, occurring in the last two decades
Estimates of extinction rates vary widely, from 2 % to 25% by 2020
In contrast to previous mass extinctions, scientists agree that this one is caused by humans.