Ecosystems and Sustainability

1. Ecosystems and Sustainability Unit 1 Communication, Homeostasis and Energy

2. Populations and sustainability Module 3: Ecosystems and Sustainability

3. Learning outcomes • Explain the significance of limiting factors in determining the final size of a population. • Explain the meaning of the term carrying capacity.

4. Population • A group of organisms of the same species, which live in the same place, at the same time and can interbreed with one another.

5. Population Growth • Sigmoid growth curves • Populations tend to increase until reaching the maximum number that can live in that habitat. • Limiting factor • Factor which stops a population from increasing in size. • In wild populations, different factors may effect population growth at different times and in different ways

6. Population Growth Curve

7. Suggest the limiting factors for a population of song thrushes in the gardens of a small town. Limited supply of slugs, snails and invertebrates (food) Nesting sites Predators parasites Limiting factors also include the abiotic factors Water Light Oxygen Shelter temperature Limiting Factors

8. Abiotic - Non living factors Temperature Light intensity Soil pH Availability of water Availability of minerals Biotic – living factors Competition Predation disease Biotic and Abiotic Interactions

9. Density dependent factors Effect increases as population density increases Population level off, then decrease Example - availability of food Density independent factors Effect independent of the size of the population Example – forest fire Density dependent and density independent factors

10. Carrying Capacity (K) • The maximum population size that can be maintained by an area over a period of time.

11. In the wild it is unlikely that a population will enter a decline or death phase A population will fluctuate up and down about the carrying capacity Carrying Capacity

12. Learning outcomes • Describe predator–prey relationships and their possible effects on the population sizes of both the predator and the prey.

13. predation • Patterns of predator prey interaction • Stable coexistence • Cyclical variations • Erratic swings • Extinction of prey species • Important factors to consider • Carrying capacity of the habitat • Reproduction rate of prey • Reproduction rate of predator • Degree of flexibility of predator to switch prey

14. Cyclical Variations

15. Predator – prey graphs • Evidence suggests that • The size of the predator population is influenced by the size of the prey population • And vice versa

16. Predator – prey in a lab • Predatory mite and its prey were introduced to a controlled environment • The populations of both mites oscillate • The population of the prey rises followed by the population of the predator

17. Predatory mite vs prey mite • Rise in population of predator follows that of the prey • Prey population limited by the rise in predators • Reduction in food supply limits the predator population • Prey population begins to increase again

18. Predator-prey in the wild • In the wild, it is more likely that the predator will have more than one food source. • Although predatory-prey interactions are thought to be one of the main factors affecting the populations of lynxes and snowshoe hares in Northern Canada.

19. Exercise • Convert the information in the table into a graph to illustrate any patterns that may exist. • Label and number the axes clearly • Decide how to represent the populations of hare and lynx on the same graph.

20. Population numbers in the lynx and snowshoe hare

21. Snowshoe hare and lynx Describe and explain the patterns shown by the graph

22. Role of Predators in maintaining diversity • By removing prey who are strong competitors, weaker competitors can survive • Reduce effect of competitive exclusion • The ecosystem benefits from • Increasing species diversity • Increasing stability • The ability to adapt to environmental change • Examples where removing predators has collapsed an ecosystem • Otters and the sea kelp forests

23. Lynx vs. Snowshoe Hare

24. Pupil Activity • Predator-prey populations • Look at the two graphs on the worksheet • Answer the accompanying questions

25. Answers • Predatory mite vs Prey • Predator is the secondary consumer, prey mite is the primary consumer • Energy lost as transferred through trophic levels • Less energy to support 2o consumers • As biomass of each individual is the same, the number of secondary consumers will be smaller than the number of primary consumers

26. Answers • Lynx vs. Snowshoe hare • Lynx furs oscillated in 7-8 year cycles, never rising above 6000 furs trapped, but in some years almost none were trapped • Lynx and hare populations oscillate on the same time scale • Which fits the predator prey theory as lynx data shadows that of the snow shoe hare after about 2 years. • Other factors • Parasites • Inconsistent trapping • No records of other possible factors

27. Learning outcomes • Explain, with examples, the terms interspecific and intraspecific competition.

28. Competition • Interspecific interactions • Between individuals of different species • Intraspecific interactions • Between individuals of the same species • Which type of interaction is more intense, interspecific or intraspecific? Why?

29. Intraspecific competition • Individuals that are best adapted will survive to reproduce • Slows down population growth and population enters stationary phase • Keeps population stable • Decrease in population size, competition reduces, population size increase • Vice versa • intense

30. Interspecific competition • Occurs when two niches overlap • Affects population size and distribution of a species in an ecosystem

31. Niche • The sum of • An organism’s adaptations • The resources it needs • The lifestyle to which it is fitted

32. Paramecium aurelia and P. caudatum Experiments Gause’s competitive exclusion

33. Principle of Competitive Exclusion • When cultured together Paramecium aureliahas a competitive advantage over P. caudatumfor gaining food.

34. Gause’s conclusions • The more overlap between two species’ niches would result in more intense competition • Competitive exclusion principle • When grown together, there was competition for food with P. aurelia obtaining food more effectively than P. caudatum, which died out.

35. Changes in population size of two species of flour beetle, Tribolium confusum and Tribolium castaneum, competing for food and space in a container of wholemeal flour. Competitive Exclusion

36. Several factors work together to influence population size and distribution Example – distribution of two species of barnacle. Interacting Factors

37. Fundamental and Realised Niches

38. Chthamalus stellatus Dessication at the top of its range Better at coping with temperature fluctuations and exposure to dry air. Competition with Balanus at the bottom of its range. Balanus balanoides Dessication and competition with Chthamalus at the top of its range Faster growing, so wins the competition for limited space on the rocks in the middle of its range Predation by Nucellus at the bottom of its range and competition with seaweed for space. Factors affecting distribution

39. Pupil Activity • Competition • How much can you remember? • Complete the worksheet, commenting on interspecific competition and interacting factors

40. Competition answers

41. Competition answers

42. Competition answers

43. Pupil Activity • Past paper exam questions • Competition • 2804 Jan 05 question 4 • Populations and competition • 2804 Jun 06 question 4

44. Answers 2804 Jan 05 qu 4

45. Answer 2804 Jun 06 qu 4 (a)

46. Answer 2804 Jun 06 qu 4 (b)

47. Answer 2804 Jun 06 qu 4 (c)

48. Learning outcomes • Distinguish between the terms conservation and preservation. • Discuss the economic, social and ethical reasons for conservation of biological resources.

49. Definitions • Biodiversity • The range of habitats, communities and species that are present in an area, and the genetic variation that exists within each species. • Conservation • Active management of habitats in order to maintain or increase biodiversity • Preservation • Protects species or habitats e.g. by creating a nature reserve

50. Definition of conservation • Management of human use of the biosphere so that it may yield the greatest sustainable benefit to present generations while maintaining it’s potential to meet the needs and aspirations of future generations. • World conservation strategy