Day 1 HW: Read chapter 53

1. Day 1 • HW: Read chapter 53

2. Fig. 52-2f The Final Unit: Ecology (chapters 52, 53, 54, 55 and 56)

3. Four major topics • Population biology • Abiotic and biotic factors that affect population size, growth and decline • Classification of the environment • Different levels of environmental systems • Nutrient cycling and energy exchange • Human impact on the global environment NOTE: learn the vocab in this unit. You need to recognize these words, use them in essays and give examples that demonstrate your understanding of the words.

4. Ecology…defined • Ecology is the scientific study of the interactions between organisms and the environment • These interactions determine distribution of organisms and their abundance • Ecology reveals the richness of the biosphere • NOTE:ecology is not synonymous with environmental groups that advocate protections of the Earth….it does provide information or scientific knowledge to these groups

5. Several hypotheses about or discussions on how organisms survive as they interact with their environment and each other • Some believe there is cooperative learning and exchange between species • Some believe it is about self - you survive and propagate your DNA • AP board doesn’t really seem to care – they test on basic concepts (errr, so that is what we will try to focus on during this unit)

6. A population is a group of individuals of the same species living in an area • Population ecology focuses on factors affecting how many individuals of a species live in an area • Deals with size, distribution, density of populations • How populations change over time

7. Connection to evolution  • Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges

8. A community is a group of populations of different species in an area • Community ecology deals with the whole array of interacting species in a community

9. An ecosystem is the community of organisms in an area and the physical factors with which they interact • Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components

10. Fig. 52-2d

11. The biosphere is the global ecosystem, the sum of all the planet’s ecosystems • Global ecology examines the influence of energy and materials on organisms across the biosphere

12. Population Ecology

13. Demographics of populations • Defined: statistical study of populations • Includes: • Density • Distribution • Rate of growth • Based on mortality patterns • Age distribution

14. Population Density • Density is the number of individuals per unit area or volume • Eg. there are 73 people per square mile in the US • Problem is that individuals are not uniformly distributed • Eg. More people in cities vs country, more people in certain neighborhoods within a city, etc.

15. Population Dispersion/distribution • The pattern of spacing among individuals within the boundaries of the population • Resources affect where populations live • Abiotic limiting factors: environmental factors that affect where organisms live • Eg. Tout live in cool mountain streams – require constant oxygen levels and cool temperatures • Eg. Catfish live in rivers, by the coastline because they can tolerate lower oxygen levels and warmer water • Eg. timberline – limit of where trees can grow in mountainous regions…cannot grow above this line due to low temperatures (water is frozen) • Biotic factors • Red kangaroos only live in air inland areas because they are adapted to feeding on the grass that grows there

16. 3 main types of Distribution • Clumped • Random • Uniform NOTE: distribution patterns do not necessarily remain constant eg. desert shrubs can be clumped, random or uniform depending on their age

17. Clumped • Individuals live in packs that are spaced out from each other • Can indicate heterogeneous environment or social interaction amongst organisms • Eg. herd of cattle, school of fish

18. Uniform • individuals are evenly distributed • Can be due to competition for resources and interactions • Territoriality – defense of physical space • Eg. Birds on a wire over the highway (I think this is cool)

19. Random • Species are randomly distributed • Absence of strong interactions, or a consistent habitat • Eg. trees in a forest

20. Factors that affect distribution patterns • Resource availability • Breeding behaviors • Eg. eagles exhibit territorial behaviors • Seed dispersion • Eg. cedar trees are clumped by parents because seeds don’t disperse easily

21. Population growth • Rate of natural increase (r) • For our purpose will be = growth rate • Depend on number of individuals born each year and the number that die each year • Biotic potential • Highest possible rate of natural increase or a population when resources are unlimited • unlimited space • lack of competition or predators • Varies from species to species

22. Day 2

23. Demographics of population • Demographics: study the theory and statistics behind population growth and decline. • Statistics are taken on the following (and you need to know what is meant by each =)

24. Population ecology must know definitions • Birth rate: offspring produced per time period • Highest among those in the middle of the age spectrum • Death rate: number of death per time period • Highest among those at two extremes of the age spectrum • Sex ratio: proportion of males and females in a population • Generation time: time needed for individulas to reach reproductive maturity • Age structure: statist that compares the relative number of individuals in the population from each age group • Immigration rate: rate at which individuals relocate into a given population • Emigration rate: rate at which individuals relocate out of a given population

25. Quick look at these stats • High birth rate and low death rate → faster rate of population growth • High female sex ratio → could cause an increase in number of births in a population • Short generation time → allows offspring to be produced at a faster rate • Age structure with more individuals in the middle of reproductive years → grow at a faster rate than one weighted toward older people • Etc.

26. Biotic potential (aka life history traits) Whether high or low will depend on • Usual number of offspring per reproductive event • Chance of survival until age of reproduction • How often each individual reproduces • Age at which reproduction begins

27. Mortality patterns • Cohort: all the members of a population born at the same time • Investigators study cohorts and construct life tables • look at mortality rates • Look at survivorship: probability of a newborn individual of a cohort surviving to particular ages

28. Three types of survivorship curves • Survivorship curves can be classified into three general types: • Type I: low death rates during early and middle life, then an increase among older age groups • Type II: the death rate is constant over the organism’s life span • Type III: high death rates for the young, then a slower death rate for survivors

29. Survivorship curves Death unrelated to age Death occurs after midpoint Death comes early on NOTE: some may be a combination of curves

30. Age distribution • Age structure diagrams can predict a population’s growth trends • They can illuminate social conditions and help us plan for the future

31. Fig. 53-25 Possible Age structure diagrams Rapid growth Slow growth No growth Afghanistan United States Italy Male Female Age Male Female Age Male Female 85+ 85+ 80–84 80–84 75–79 75–79 70–74 70–74 65–69 65–69 60–64 60–64 55–59 55–59 50–54 50–54 45–49 45–49 40–44 40–44 35–39 35–39 30–34 30–34 25–29 25–29 20–24 20–24 15–19 15–19 10–14 10–14 5–9 5–9 0–4 0–4 10  8 6 4 2 0 2 4 6 8 10  8 6 4 2 0 2 4 6 8 8 6 4 2 0 2 4 6 8 Percent of population Percent of population Percent of population Note: make sure you can read and understand these

32. Other info on population growth • All populations show some sort of fluctuations in numbers • There are two main types of growth • Exponential growth • Logistic growth

33. Exponential growth • Population grows at a rate that creates a J-shaped curve • Population grows as as if there are not limitations to its size (biotic potential)

34. Logistic growth • Population grows at a rate that creates an S-shaped curve • Limiting factors are the culprits responsible for the s-shape…put a cap on the size to which the population can grow

35. Combined graph – shows exponential and logistic growth curves

36. Life History Strategies • K-selected populations • Population of a roughly constant size • Members have a low reproductive rate • Offspring require extensive postnatal care until they are mature • Eg. humans • R-selected populations (aka opportunistic populations) • Rapid growth of the J-curve variety • Offspring are numerous, grow quickly, mature rapidly, require little postnatal care, die quickly • Tend to show up when space in region opens up as a result of environmental change • Eg. bacteria

37. Carrying capacity (K) • Maximum number of individuals that a population can sustain in a give environment • Limiting factors - Control population size • Categories • Density - dependent factors • Density – independent factors

38. Estimates of Carrying Capacity • The carrying capacity of Earth for humans is uncertain • The average estimate is 10–15 billion

39. There are two general questions about regulation of population growth: • What environmental factors stop a population from growing indefinitely? • Why do some populations show radical fluctuations in size over time, while others remain stable?

40. In density-dependent populations, birth rates fall and death rates rise with population density • In density-independent populations, birth rate and death rate do not change with population density

41. Density-Dependent Population Regulation • Density-dependent birth and death rates are an example of negative feedback that regulates population growth • They are affected by many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors

42. Competition for Resources • In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate

43. Fig. 53-16 100 80 60 Percentage of juveniles producing lambs 40 20 0 200 300 400 500 600 Population size

44. Territoriality • In many vertebrates and some invertebrates, competition for territory may limit density • Cheetahs are highly territorial, using chemical communication to warn other cheetahs of their boundaries

45. Fig. 53-17 (a) Cheetah marking its territory (b) Gannets

46. Overview: Density - dependent factors • Referred to as K-selection, selects for life history traits that are sensitive to population density • Generally biotic factors • Death rate rises and birth rate falls as population density increases • (fyi: equilibrium can exist if birth rate and/or death rate, or both are affected by density dependent factors) • Factors have a greater affect as population increases or as “density increases” • Eg. Food supply (predation or emigration), waste build up, disease caused by overpopulation (eg. bubonic plague)

47. Density – independent factors (r-selection) • Generally catastrophic abiotic factors • Eg. floods, droughts, weather conditions, and other natural disasters Have nothing to do with population size – floods will affect large and small populations • It is possible for a greater number of a species to be affected • r-selection, or density-independent selection, selects for life history traits that maximize reproduction • Death rate and birth rate do not change as density changes • Affect populations in the same way regardless of how many there are at a given time

48. Fig. 53-14

49. Limits on Human Population Size • The ecological footprint concept summarizes the aggregate land and water area needed to sustain the people of a nation • It is one measure of how close we are to the carrying capacity of Earth • Countries vary greatly in footprint size and available ecological capacity

50. Done