Chapter 5

1. Chapter 5 Evolution, Biodiversity, Population Ecology

2. Evolution • Biological evolution consists of genetic change in organisms across generations. • May proceed randomly or be directed by natural selection.

3. Natural Selection • Process by which traits that enhance survival and reproduction are passed on more frequently to future generations, altering the genetic makeup of populations through time.

4. Natural Selection • Charles Darwin • Alfred Russell Wallace • Both naturalists – studied plants/animals • Proposed natural selection as a mechanism for evolution and as a way to explain the great variety of living things.

5. Logic of Natural Selection • a. Individuals of the same species vary in their characteristics. • b. Organisms produce more offspring than can possibly survive. • c. Some offspring may be more likely to survive and reproduce.

6. Logic (continued) • d. Characteristics that give individuals an advantage in surviving and reproducing might be inherited by their offspring. • e. These characteristics would tend to become more prevalent in the population in future generations. *A trait that promotes success is called an adaptation.

7. Natural Selection • Acts on genetic variation: • Accidental changes in DNA are called mutations • Most mutations have little effect; some are deadly; a few are beneficial. • Sexual reproduction generates variation – genes from both parents

8. Natural Selection • 3 ways that genetic variation alters organisms’ characteristics: 1. Directional selection 2. Stabilizing selection 3. Disruptive selection *draw each graph (a, b, c) from page 115 in your notes at this time

9. Artificial Selection • Process of selection conducted under human direction *With a partner, come up with at least 2 examples of artificial selection – you have 3 minutes

10. Book Work • With a partner you have not worked with: • Page 137 • Testing Your Comprehension – 1 &2 • Seeking Solutions – 1 • Keep this paper, you will be adding to it daily during this chapter (answers will be checked periodically)

11. Evolution generates biodiversity • Biological diversity, or biodiversity, is the sum total of all organisms in an area, taking into account the diversity of species, the diversity of populations within a community, and the diversity of communities within an ecosystem.

12. What is a species? • A species is a population whose members share certain characteristics and can freely breed with one another and produce fertile offspring.

13. What is a population? • A group of individuals of a particular species that live in the same area.

14. Speciation • Speciation produces new types of organisms. • 1. When populations of the same species are kept separate, their individuals no longer come in contact, so their genes no longer mix. • Called allopatric speciation

15. Speciation 2. If there is no contact, the mutations that occur in one population cannot spread to the other. • Called sympatric speciation

16. Read through the section “Populations can be separated in many ways” and list the mechanisms that can cause allopatric speciation

17. Vocab Study Time • With a partner, use your flash cards to study your vocabulary words. • We will have a vocab competition at the end of class today!

18. “Mapping” the History of Diversity • Phylogenetic trees • Show relationships among groups of organisms • Used to study how traits have evolved over time • Page 119 – arrows used to indicate when traits orginated

19. Speciation and Extinction Contribute to Biodiversity • Extinction – the disappearance of a species from Earth • Number of species in existence = Number added through speciation – Number removed by extinction • Extinction brought on by humans is biggest environmental problem we are facing

20. Some Species more Vulnerable than Others • Generally, extinction occurs when environmental conditions change rapidly or severely enough that a species cannot genetically adapt to the change. • Some species are vulnerable because they are endemic, occurring in only a single place on the planet.

21. Episodes of Mass Extinction • There have been five mass extinction events at widely spaced intervals in Earth’s history that have wiped out anywhere from 50 to 95% of Earth’s species each time. • Best known – 65 million years ago – end to dinosaurs (“Science Behind the Story 122-123)

22. 6th Mass Extinction – Is it near? • Biologist conclude that Earth is entering its 6 mass extinction • Caused by • Population growth • Development • Resource depletion • Destruction of natural habitats • Harvesting/Hunting • Non-native species introductions

23. Book Work • Add this to your previous assignment and turn in when finished – due Wednesday morning! • Page 137 • Testing Your Comprehension #s 3, 4, and 5

24. Levels of Ecological Organization • Organisms Population  Community Ecosystem  Biosphere • Biosphere is the cumulative total of living things on Earth and the areas they inhabit

25. Levels of Organization • A group of organisms of the same species that live in the same area is a population • Species are often composed of multiple populations • Communities are made up of multiple interacting species that live in the same area. • Ecosystems encompass communities and the abiotic (nonliving) material and forces with which their members interact.

26. Population Ecology • Investigates how individuals within a species interact with one another. • Why do some populations increase? • Who do some populations decrease?

27. Community Ecology • Focuses on interactions among species • From one-to-one interactions to complex relationships involving entire communities • Roane County Park

28. Ecosystem Ecology • Studies living and nonliving components of systems • Reveals patterns, such as energy and nutrient flow

29. Ecology at the Organism Level • Habitat, niche, and degree of specialization are important in organismal ecology • The specific environment in which an organism lives is its habitat. • Each organism has patterns of habitat use. (p.124)

30. Organism Level (continued) • A species’ niche reflects its use of resources and its functional role in a community. • Species with very specific requirements are said to be specialists. • Those with broad tolerances, able to use a wide array of habitats or resources, are generalists. • Pros/Cons page 125

31. Population Ecology:Population Characteristics • Populations exhibit characteristics that help predict their dynamics. • 1. Population size is the number of individual organisms present at a given time. • 2. Population density is the number of individuals in a population per unit area.

32. Characteristics (contd.) • 3. Population distribution is the spatial arrangement of organisms within an area. • 4. Sex ratio -proportion of males to females. • 5. Age structure, describes the relative numbers of organisms of each age within a population. • 6. Birth and death rates measure the number of births and deaths per 1,000 individuals for a given time period.

33. Population Distribution • 3 Types: • Random – individuals are not located in any particular pattern; resources are found throughout an area • Uniform – individuals are evenly spaced; desert need equal space for their roots to gather water • Clumped – (most common) individuals are arranged around resources

34. Age Structure • Population of mostly individuals past reproductive age will decline • Population of mostly individuals pre-productive age will increase • Population with even age distribution will remain stable • Page 128, figure 5.13

35. Survivorship Curves • Based on birth and death rates • Page 128, figure 5.14 • Type I – survival rates for young are high and decrease at an old age (humans) • Type II – survival rates equal among age (birds) • Type III – highest death rate at young ages (amphibians – tadpoles)

36. Populations may grow, shrink, stablilize • Population growth or decline is determined by births, deaths, immigration, and emigration. • Immigration – into • Emigration – away *E for Exit

37. Unregulated Populations • No external limits • Mold growing on bread, bacteria on dead animal, trees in a new area • When a population increases by a fixed percentage each year, it is said to undergo exponential growth. • Relate this type to a savings account, page 129, Table 5.3

38. Book Work • Page 137, Testing Your Comprehension • #s 6-8

39. Limiting Factors Restrain Population Growth • Populations are contained by limiting factors - physical, chemical, and biological characteristics of the environment • The interaction of the limiting factors determines the carrying capacity. • Carrying capacity – max population size of a species that an environment can sustain

40. Logistic Growth Curve • Populations increase sharply at first and then level off due to limiting factors • Known as environmental resistance • Page 130, Fig. 5.16 L.G.C. • Look at page 131, Fig. 5.17 for other types of growth models

41. What are examples of limiting factors? • Water • Space • Food • Predators • Disease • Breeding sites • Temperature • pH • Salinity (salt content) • Pollutants

42. Carrying Capacities Can Change • Some organisms can alter their environment to reduce environmental resistance and increase carrying capacity. • Humans have used immense proportions of the planet’s resources to increase our carrying capacity, but have reduced the carrying capacities for many other organisms

43. Affects on Limiting Factors • Density-dependent factors -based on population density • Increased pop., increased chance for mating • Increased pop., increased competition and disease • Density-independent factors -not affected by population density • Temperature extremes • Catastrophic events (floods, fires, landslides, etc.) • Can eliminate large #s no matter the density

44. Biotic Potential • Ability to produce offspring • Fish – high biotic potential, lay 1000s of eggs in a short time • Whale – low biotic potential, birth to one calf after a long gestation (pregnancy) period • Low biotic potential organisms protect their offspring

45. K-Selected Species • Low biotic potential • Populations stabilize over time at or near carrying capacity • K stands for carrying capacity • Competition is high between organisms

46. R-Selected Species • High biotic potential • Devote energy to produce large amounts of offspring • R stands for rate • Rate at which species increase/decline varies and number at or near carrying capacity can be very high or very low