Chapter 5: Evolution, Biodiversity & Population Ecology

1. Chapter 5: Evolution, Biodiversity & Population Ecology www.aw-bc.com/Withgott

2. Evolution • genetic change in populations of organisms across generations. • modifications • appearance: www.aw-bc.com/Withgott

3. Evolution • functioning: beaks in honeycreepers www.aw-bc.com/Withgott

4. Natural Selection • explains the great variety of living organisms. • derives from several premises noticed in nature

5. Natural Selection Premises • constant struggle of organisms to survive and mate • organisms tend to produce more offspring that can survive. • individuals of the same species are not identical • variation

6. Variation • genetical differences • environment within which genes are expressed • interaction between genes and environment • Adaptation: trait that promotes success of a species

7. Effects of Natural Selection on Genetic Variation • Mutations: accidental changes in the nucleotide sequence of the DNA • addition • deletion • substitution

8. Sexual Reproduction also Generates Variation • recombination of genes produces a novel combination generating variation • directional selection • stabilizing selection • disruptive selection

9. Directional selection • selection that drives a feature in one direction www.aw-bc.com/Withgott

10. Stabilizing selection • preserves status quo, no changes www.aw-bc.com/Withgott

11. Disruptive Selection • traits diverge into two or more directions www.aw-bc.com/Withgott

12. Evidence of Natural Selection • Selective breeding • breeding of domesticated animals and plants • dog and cat breeds • variations of Brassica oleracea • artificial selection

13. Biodiversity • Total of all organisms in the area • diversity of species • gene pool • populations • communities • Evolution generates biological diversity • as of 2008 1:3 amphibians, 1:7 birds and 1:5 mammals is considered endangered or threaten (National Geographic) • Species: organism that is able to reproduce and have viable offspring

14. Speciation: Allopatric & Sympatric • Allopatric: species form due to physical separation • mutations can occur independently • members of different populations don't mate • populations continue diverging through time • single species can generate multiple species through time

15. Separation of Populations • glacial ice sheets during ice ages • change of course of major rivers • rise of mountain ranges • evaporation of major lakes into smaller bodies of water • temperature variation causing migration of plant populations creating new patterns of animal/plant distribution • isolation must remain for thousands of generations • reunion of populations may occur, but if they are not able to interbreed, two or more new species have emerged.

16. Sympatric • reproductively isolated due to behavioral causes • feeding at different times of the day • feed at different sites • mating on different times of the year • hybridization in some plants • mutations causing change in number of chromosomes

17. Diversification • as a result of numerous speciation events • phylogenetic trees explain differences and similarities between species • Speciation and extinction • natural process that takes 1-10 million years

18. Diversification www.aw-bc.com/Withgott

19. Species Vulnerable to Extinction • some species may be more vulnerable than others due to change in environmental conditions • climate change • rise and fall of sea level • arrival of harmful species • extreme weather events (drought, flood, etc.) • Endemic: single small population present only in a particular type of environment: Attwater chicken

20. Attwater Chicken • 1 million individuals in 1900 • 50 or so individuals today • habitat disruption • oil industry, housing, cattle, rice fields • predators (snake, rat, skunk) • diseases • weather • collision (fence, cars) • fire ants (kill chicks)

21. Levels of Ecological Organization • Species • Population • Communities • Ecosystems • Biosphere

22. www.aw-bc.com/Withgott • Ecological Organization

23. Habitat, Niche and Specialization • Habitat: living and non-living elements around a species • thriving of a species depends on patterns of habitat use • each species' habitat is scale dependent • habitat selection is possible if the species is mobile • the survival of the species depends if the habitat is suitable or not

24. Niche • a species' niche reflects its use of resources and functional role in the ecosystem • "job" • specialists and generalists • Prairie dog • eats grasses and keeps grass low for predator control • more grass grown around burrow because • airiates soil by digging • soil becomes richer near burrows because of dung • burrow houses other animals when empty (snakes, rabbits, owls)

25. Population Ecology • Population size: number of individuals present at a given time • Attwater chicken- 1 million to 50 individuals • Population density: number of individuals per population per unit area • golden toad- large population in a small area • Population distribution: spatial arrangement of organisms within an area. There are 3 types.

26. Population Distribution: Random www.aw-bc.com/Withgott

27. Uniform www.aw-bc.com/Withgott

28. Clumped www.aw-bc.com/Withgott

29. Population Ecology • sex ratio: depends on the behavior (monogamous or polygamous) of the species, type of reproduction (autofecundates or different sexes) • age structure: age structure diagrams www.aw-bc.com/Withgott

30. Population Ecology • birth and death rates: survivorship curves • type I: higher mortality at older age • type II: equal rate of death at any age • type III: higher rate of death at younger age www.aw-bc.com/Withgott k-selected r-selected

31. Population Ecology • Immigration • emigration • growth rate • Unregulated population increase: shows exponential growth=J curve • carrying capacity causes logistic growth curve (S curve) to show • caused by an environmental resistance (water, food, shelter, predators, disease)

32. Density-dependent factors • its influence is affected by the population density • competition • food • shelter • mate • water • s-shaped curve

33. Density-independent factors • influence is not affected by population density; can eliminate large numbers of individuals without regard to its density • extreme temperatures • catastrophic climate events • fires • volcano eruptions

34. Biotic Potential vs Reproductive Strategy • k-selected (k stands for Carrying capacity) • low biotic potential • long gestation period • protects offspring as an investment for species survivor • relative few offspring during lifetime • type 1 curve • eg: humans, whale, rhino, elephant

35. r-selected (r stands for rate) • focus on quantity not quality • high biotic potential • large number of offspring • survivor of offspring depends on chance • type 3 curve • eg. fish, frogs, snails

36. Conservation of Biodiversity • social and economic factors • human behavior towards environment • economy vs environmental protection • protection of environment • began without much government support • even today governments may not have the funds • ecotourism is the key THE END