Chapter 5: Interactions in the Ecosystem

1. Chapter 5: Interactions in the Ecosystem 5.1 Habitats and Niches 5.2 Evolution and Adaptation 5.3 Populations

2. Objectives • Describe the concept of the niche. • Examine how interactions between a species and its environment define the specie’s niche.

3. Chapter 5:Interactions in the Ecosystem • An ecosystem is a network of living and nonliving things. • Organisms are connected by food webs and by their common needs. • All organisms need: • A. Food and Energy • B. Water • C. Living Space • D. Appropriate Climate

4. Interactions in the Ecosystem (cont.) • All species have evolved different ways of gathering resources from their environment. • Evolution ties together biology and the physical world as ecology ties together the interactions between living and nonliving things. • Therefore, the study of ecosystems is also the study of evolution

5. 5.1 Habitats and Niches • Ecosystems can be extremely large; containing many square kilometers and many different organisms. • Environments within an ecosystem vary: the environment by a stream is different than the environment in a forest. • The organisms in these different environments are different from each other. They have adapted to the conditions in their particular habitat.

6. Niches • Niche-the role of an organism in the ecosystem. • The actions of an organism define its role in the ecosystem. • A niche is more than just the habitat an organisms lives in; it is also what that organism does within its habitat

7. Niches (cont.) • A niche includes both the biotic and abiotic factors. • All the biotic and abiotic factors taken together define an organisms niche. • Biotic factors-food source and predators • Abiotic factors-temperature, amount of sunlight and water

8. Niches (cont.) • All members of a species are adapted to the same niche. • No two species can share the same niche in the same habitat. • Two species can occupy niches that are very similar to each other.

9. Niches (cont.) • Example: Anolis lizards • The niches of the different species vary only in the size of the insects they eat. • If two species try to share the same niche in the same habitat, they will compete for resources. • This could cause the one specie to have to move to another area or the populations to die out.

10. Anolis Lizard

11. Niches (cont.) • Competitive exclusion: the extinction of a population due to direct competition with another species for resources. • Competitive exclusion is the extinction of one population in one area not the extinction of a whole species.

12. Niches (cont.) • In many ecosystems the niche of one specie can effect the niche of another specie. • Figure 5.3 p. 74 Barnacles

13. Barnacles Species B (Balanus)was responsible for the niche of species A (Chthamalus) and when removed A began to grow further down.

14. Niches (cont.) • Fundamental niche-the theoretical niche • Realized niche-the actual niche Fundamental Niche Realized Niche

15. Niche Diversity • Niche diversity is determined by the abiotic factors in an ecosystem. • Predator-an organism that actively hunts another organisms • Prey-the hunted organism • Predators help to increase the diversity of niches by keeping the population of its prey in check. This allows resources to be available for other organisms.

16. Niche Diversity (cont.) • Keystone predator- a predator that promotes a great niche diversity in its habitat. • Robert Paine and the Sea Stars • He removed the sea star from a tide pool and as a result the mussel population increased until they began to “out compete” the other species. • The number of species dropped from 15 to 8.

17. Sea Stars and Tide Pools

18. Review • What is a niche? • What effect does a keystone predator have on niche diversity? • What is the difference between a fundamental niche and a realized niche?

19. 5.2 Evolution and Adaptation Objective Explain how a species adapts to its niche. Describe convergent evolution and coevolution, and relate each to the concept of niche.

20. Evolution and Adaptation • Ecosystems change over time. Mountains are created and eroded, rivers change course forest are created and destroyed. • Changes in environment affect the niches of the organisms in that particular environment. • Changes in the environment affect the evolution of populations

21. Natural Selection • http://www.pbs.org/wgbh/evolution/educators/course/session4/explore_a.html

22. Evolution • Evolutions is a change in the characteristics of a population of organisms over time. • This occurs when some individuals have genetic variations that give them an advantage over other organisms. • Evolution: Online Lessons for Students: Activity 4- Flashy Fish

23. Evolving in a Niche • Evolution causes organisms to evolve to a certain niche in the environment. • This reduces competition with other species. • Fig. 5.5 Warblers • Specialized species-Koala • Generalized species-Cockroaches

24. Convergent Evolution • Similar ecosystems often have similar niches. • Environmental pressures may then select for similar adaptations. Resulting in organisms that may even look alike. • Convergent Evolution- the independent development of similar adaptations in two species with similar niches. • Examples: Figure 5.6 and

25. Convergent Evolution

26. Convergent Evolution

27. Coevolution • Other organisms may play an important role in the life of an organism. • Keystone Predators • Species that interact closely may become adapted to one another through a process called Coevolution. • Result from: Feeding relationships and adaptation for mutual benefits. • Examples:

28. Coevolution –Yucca Moth and Yucca Plant

29. Coevolution • http://www.pbs.org/wgbh/evolution/library/01/3/quicktime/l_013_01.html

30. Review • How do species adapt to the environment? • What is the difference between coevolution and convergent evolution?

31. 5.3 Populations Objectives Explain how populations of organisms grow. Describe the factors that limit the growth of a population. Identify the shapes of growth curves that represent populations of different organisms.

32. 5.3 Populations • The abiotic and biotic factors that define a niche also limit the growth of a species. • Size of a population can be limited by: • Lack of food • Predators • Disease

33. Population Growth • Thomas Malthus an English economists studied human population. • He stated: • Human population can quickly grow past the environment’s ability to support it. • He felt that famine and disease occurred when populations became too large. • Bubonic Plague

34. Population Growth • Malthus’s observations influenced a naturalist by the name of Charles Darwin. • “On the Origin of Species” • “There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the Earth would soon be covered by progeny of a single pair.”

35. Population Growth • Important to Darwin’s theories of evolution was the idea that organisms produce more offspring than can survive. • Overproduction of offspring causes: • Selection of the more favorable traits (survival of the fittest)

36. Population Growth • Darwin illustrated overproduction with the example show in Figure 5.8 p. 80.

37. Population Growth • Exponential Growth- population growth in which the rate of growth in each generation is a multiple of the previous generation. • Any population has the potential to increase exponentially if…the perfect conditions exist

38. Population Growth • Although natural population can show exponential growth, it occurs only for a short time. This is due to the availability of resources and restricted geographic areas.

39. Carrying Capacity • As a population grows it takes more from the habitat. • Resources become scarce. • Scarce Resources = Competition • Death rate increases • Birth rate decreases • Growth Slows • Birth rate = Death rate (population growth stops)

40. Carrying Capacity • Carrying Capacity- the number of individuals of a species that can be supported by an ecosystem • Figure 5.9 p. 81

41. Limiting Factors • Forces that slow the growth of a population are called the limiting factors. • Figure 5.10 p. 82 • Examples:

42. Limiting Factors • Two kinds of limiting factors • density dependent limiting factors • density-independent limiting factors

43. Limiting Factors • Density dependent limiting factors: dependent on population size. • Food supply • Predation • Disease • Parasitism • Living Space • Water Availability • Density dependent factors are related to competition and other interactions between organisms • As populations grow these factors have a greater effect.

44. Limiting Factors • Density-independent limiting factors: affects the same percentage of a population regardless of its size. • Climate • Human Disturbances • Deforestation • Natural Disasters • Hurricanes

45. Limiting Factors • Populations controlled by density dependent factors show a S-shaped growth curve. • Populations controlled by density-independent factors show a boom-and-bust curve. This type of curve represents exponential growth. • Many insects follow this type of curve. • Figure 5.11 p. 83

46. S-Shaped Curve

47. Boom Bust Curve Population

48. Human Population • Human population has long been an exponential one. • This continuing exponential has continued due to: • Advances in medicine, technology, agriculture, energy development, transportation • However, no population can continue this way. • Human population growth will level out as: • Use up all the available resources

49. Summary • What is exponential growth? • What is carrying capacity? • What are the two types of limiting factors? • What has allowed human population to keeping growing exponentially?