1. Evolution of Biodiversity
Chapter 5
Evolution of Biodiversity

2. Earth is home to a tremendous diversity of species
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.

4. Species – can interbreed and produce viable offspring

6. CURRENTLY: Scientists have named 2 million species
Biodiversity – most commonly measured by the number of species in any give place
CURRENTLY: Scientists have named 2 million species
Insect group – most diverse!
Insect species – 30 million
Total Estimate – between 5 and 100 million

7. Species richness- the 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.

8. Species richness or eveness often declines after a human disturbance.
Knowing the species richness and eveness of an ecosystem seves as a baseline for change.

9. Pg. 124 Do the Math

10. Phylogenies – branching patterns of evolutionary relationships used to organize species.
Traits used to organize species: morphology; behavior, and genetic similarity.

11. Why is it challenging to determine the number of species on Earth?
Why are estimates of species diversity valuable to environmental scientists?
What is the difference between species richness and species evenness?
Why are they both important?

12. Evolution is the mechanism underlying biodiversity
Evolution- a change in the genetic composition of a population over time.
Microevolution- evolution below the species level. (varieties of apples etc)
Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.
Speciation – evolution of new species

15. Creating Genetic Diversity
Genes- physical locations on chromosomes within each cell of an organism.
Genotype- the complete set of genes in an individual.
Two processes that create genetic diversity:
Mutation- a random change in the genetic code.
Recombination – when chromosomes are duplicated during reproductive cell division and a piece of one chromosome breaks off and attaches to another.

16. Genotypes vs Phenotypes
Phenotype- the actual set of traits expressed in an individual. (color of eyes)
Genotype – blueprint for complete set of traits (genes that code for eye color).

17. Changes in the genotype due to mutation can cause changes in phenotype.
Most phenotypes are determined by both environment and genotype.
Turtle/crocodile eggs…
Water flea shape
By being able to respond to changing conditions, organisms can improve their ability to survive and reproduce.

18. Dusky-headed conure parrots

20. Evolution by artificial and natural selection
Evolution by artificial selection- when humans determine which individuals breed.
Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce.

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24. Darwin’s theory of evolution by 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.
Differences in traits are associated with differences in the ability to survive and reproduce.

26. Evolution by Random Processes
Mutation- occur randomly and can add to the genetic variation of a population. (Fig. 5.12a)
Genetic drift- change in the genetic composition of a population over time as a result of random mating. (Fig. 5.12b)
Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size. (cheetah)
Founder effect- a change in a population descended from a small number of colonizing individuals. (island)

28. Let’s Review…
What is evolution, and what are the 3 main ways in which it occurs?
How are artificial and natural selection similar? How are they different?
How does evolution lead to biodiversity?

29. How do we go from Microevolution to Macroevolution?

30. Speciation and extinction determine biodiversity
Allopatric speciation- when new species are created by geographic or reproductive isolation.

32. 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.
Naturally or through human action (breeders – crops, strawberries, bananas etc)
Polypolid cannot interbreed with diploid ancestors – naturally isoated.

33. The pace of evolution Can take hundreds to millions of years
Average is one new species every 3 million years.
Fig – RAPID - cichlid fishes

34. The pace of evolution FIG 5.17 Four factors for successful adaptation:
Rate of environmental change (acidic lakes)
Genetic variation
(high variation = more chance of new species)
Population size
(smaller = more likely to have new species)
4. Generation time
(shorter generation time = more likely evolve)

35. The pace of evolution

36. Evolution occurs more rapidly in populations of GMOs.
Bacillus thuringiensis – produces insecticide
Bt – corn, Bt-cotton

41. Review How does geographic isolation lead to reproductive isolation?
What factors influence a species chances of adapting successfully to a change in the environment?
Why is the pace of human-driven evolution faster than that of natural evolutionary processes?

42. Evolution shapes ecological niches and determines species distributions
Range of tolerance- 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.

44. Biotic factors can limit a niche as well:
Competition
Predation
Disease

45. Niches
Realized niche- the range of abiotic and biotic conditions under which a species lives. This 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.

46. Generalist Specialist
Spittlebug Leaf Beetle

47. Environmental Change and Species Distribution
Evidence:
Lake sediment/pollen
Fig – red pine vs loblolly pine

50. Environmental Change and Species Extinctions
Avg. lifespan of a species – 1-10mill years.
99% of species that once lived – EXTINCT!

52. Why do species go extinct?
No favorable environment
Polar bears
May be occupied (Fig. 5.21)
Too rapid of a change

53. The Fossil Record
Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record.

54. The Five Global Mass Extinctions
Mass extinction- when large numbers of species went extinct over a relatively short period of time.
251 mya – largest on record
65 mya - dinosaurs

55. The Sixth Mass Extinction
Scientists feel that 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.

56. How do fundamental niches and realized niches differ?
Review
How do fundamental niches and realized niches differ?
How does environmental change determine species distribution?
When does environmental change lead to extinction?
How are human activities affecting extinction rates?
Why is human impact a concern at all? (why should we care?)