Population & Community Ecology

1. Population & Community Ecology Chapter 35

2. 35.1 A population is a local group of organisms of onespecies I. Defining Populations A. A populations size is determined by the availability of food and space, weather conditions, and breeding patterns B. When scientists study populations they must determine its boundaries, such a lake, a state or the whole country

3. What is a species? • Distinct form of life • Population of organisms which can breed and produce offspring

4. Peacock + Peahen = Peachicks Horse + Donkey = Mule What about these?

5. Regional Local Boundaries

6. II. Population Density A. Population Density is the number of individuals of a particular species per unit of area or volume B.Population density is useful when comparing two populations in different areas Class Example.

7. III. Sampling Techniques A. Since it is impossible to count every member of a population scientists use sampling techniques to estimate the size of a population • Quadrats- scientists mark off a square boundary at several locations and take an average (plants) • Indirect Counting- counting nests, burrows or tracks instead of the organisms themselves (insects) 3. Mark-Recapture- scientists trap and mark individuals (birds) B. Most sampling techniques involve making assumptions about the populations being studied

8. Which sampling technique? Bats: mark-recapture Black bear: indirect Cactus: quadrat

9. Population Distribution

10. Termite Mound Rattlesnake Which distribution pattern? Random Clumped

11. 35.2 Limits to population growth I. Exponential Growth of Populations A. A population’s ability to grow partly depends on the rate at which its organisms can reproduce B. Exponential Growthis when the population multiplies at a constant factor at constant time intervals i.e. bacteria doubling every 20 minutes

12. II. Carrying Capacity • A population may start to grow exponentially, but eventually one or more environmental factors will limit its growth B. A limiting factor is a condition that can restrict a population’s growth C.The carrying capacityis the number of organisms in a population that the environment can maintain or “carry”

13. Transparency 35A-1

14. Transparency 35A-2

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16. Transparency 35A-4

17. Transparency 35A-5 1. Compare and contrast the two growth curves. Both curves show a period of rapid population growth, but the fur seal population eventually levels off. The bacterial population appears to continue growing exponentially.

18. Transparency 35A-6 2. Which curve do you think more closely resembles the growth of most populations in nature? Explain. Limited growth curve; populations in nature are subject to limiting factors that prevent long-term exponential growth.

19. III. Factors Affecting Population Growth • Density Dependent Factors is a factor that limits a population more as a population density increases B. Density-Independent Factors are factors that limit population but are unrelated to population density

20. Food availability Temperature and humidity Population Growth Density- Independent Density-dependent

21. IV. Population Cycling • A “boom” and “bust” growth cycle is one that increases rapidly followed by a sharp decline B. Other growth cycles are influenced by those of other populations in their environments

22. Population Cycling

23. 35.3 Predicting the impact of human population growth

24. 10 Largest Countries - 2006

25. 10 Largest Countries - 2006

26. 10 Largest Countries - 2050

27. 10 Largest Countries - 2006

28. History of Human Population

29. History of Human Population

30. Human Pop Graph

31. I. History of Global Population Growth • For most of human history, the human population has grown very slowly or not at all B. Human population growth depends on birth rates and death rates C. The introduction of farming has provided a stable food supply so birth rates have gone up D. Advances in modern medicine, nutrition and sanitation have caused death rates to go down E. These factors have caused the human population to increase dramatically

32. Transparency 35B-1

33. Transparency 35B-2 1. Which age group forms the largest bulge in the age-structure graph of the United States? Of Kenya? 40–44; under 5

34. Transparency 35B-3 2. Which country is likely to undergo the greatest increase in population in the next 20 years? Explain. Kenya; the majority of the population is under 25 years old, which is the portion likely to have children in the next 20 years.

35. II. Predicting Future Population Growth • The Age Structure of a population is the proportion of people in different age groups B. Prediction of future growth varies because of the difficulty predicting future birth and death rates of various countries C. The question remains whether or not Earth will have the capacity for the human population

36. 35.4 Species interact in biological communities

37. I. Competition Between Species • Members of a population may compete for the same limited resource B. Within a community, interspecific competition takes place when two or more species rely on the same limited resource C. If two species are so similar in their requirements that the same resource limits both species’ growth it is called competitive exclusion D. A niche includes an organisms living place, its food source, the time of day it is most active and many other factors that are specific to that organism’s way of life

38. Competitive Exclusion

39. II. Predation • Predation is when one organism eats another B. Eating and avoiding being eaten are important to survival and predators and prey have developed many adaptations • Predator adaptations include: being fast and agile, coloring that camouflages, hunting in groups, acute sense to find prey and having claws, teeth, fangs and stingers to help catch prey 2. Prey adaptations include: retreating or fleeing from predators, camouflage, defensive coloring, mimicry, secreting poisonous chemicals, having spines and thorns

40. Predator-Prey Relations

41. III. Symbiotic relationships • A symbiotic relationshipis when two species live in or on one another B. There are three main types of symbiotic relationships • Parasitism- A parasite gets it’s food at the expense of another organism, i.e. mosquitos and humans 2. Mutualsim- Both organism benefit from the relationship, i.e. E.Coli and humans 3. Commensalism- One organism benefits and the other is neither hurt nor helped, i.e. sharks and remoras

42. Symbiosis

43. Symbiosis - Which is it? Predator-Prey Parasitism Mongoose & Cobra Liver Fluke

44. Symbiosis - Which is it? Commensalism Mutualism Clownfish & Anemone Air Plant

45. 35.5 Disturbances in communities I. Disturbances to Communities A. Natural Disturbances are events such as fires, volcanic eruptions, floods, storms, and droughts all destroy resources such as shelter and water B. Disturbances can be either positive or negative C. Humans also have an impact on communities which can be either positive or negative

46. Surviving Environmental Change

47. II. Ecological Succession • The series of changes in the species in a community, often following a disturbance is known as ecological succession • There are two types of succession: • Primary succession which is when new community arises from a previously lifeless area i.e. plants growing on a volcanic island 2. Secondary succession is when a new community arises from a previous community i.e. a forested are which has been cleared and abandoned

48. Primary Succession

49. Secondary Succession

50. III. Human activities and species diversity • 60% of the Earth’s land is used by humans, mainly for cropland or rangeland • Humans usually have a negative effect on species in two ways • Clearing the Land- Humans clear vast amounts of land to make way for farming and building 2. Introduced Species are species that are moved from one location to another either accidentally or on purpose. These new species may take over an area and prey on native species or drive them from their niches