Ch. 4 Sec. 2

1. Ch. 4 Sec. 2 What Shapes an Ecosystem?

2. A. Biotic (living things)1. The biological influences on organisms I. Biotic and Abiotic Factors

3. B. Abiotic factors 1. Physical, or nonliving, factors that shape ecosystems 2. Abiotic factors include: • temperature • precipitation • humidity • wind • nutrient availability • soil type • sunlight

4. C. Biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.

5. D. Habitat – WHERE an organism lives 1. Includes both biotic and abiotic factors

6. II. Niche – the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions

7. The range of temperatures that an organism needs to survive • Place in the food web are part of its niche • Where it lives • How it reproduces • Food • How it obtains food • What it eats

8. The combination of biotic and abiotic factors in an ecosystem often determines the number of different niches in that ecosystem. • No two species can share the same niche in the same habitat. • Different species can occupy niches that are very similar.

9. III. Community Interactions When organisms live together in ecological communities, they interact constantly. Predation, and various forms of symbiosis, can affect an ecosystem.

10. Competition - often results in a winner and a loser—with the losing organismfailing to survive. • Competitive exclusion principle: no two species can occupy the same niche in the same habitat at the same time.

11. The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree. 18 12 Cape May Warbler Feeding height (m) Bay-Breasted Warbler 6 Yellow-Rumped Warbler 0 Fig. 4 – 5 Page 92

12. A. Competition • Competition occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time. • A resource is any necessity of life, such as water, nutrients, light, food, or space.

13. B. Predation - An interaction in which one organism captures and feeds on another organism • The organism that does the killing and eating is called the predator • The food organism is the prey

14. C. Symbiosis • Any relationship in which two species live closely together is called symbiosis. • Symbiotic relationships include: a. mutualism b. commensalism c. parasitism

15. Mutualism a. Both benefit

16. 2. Commensalism • One benefits • Other is unaffected

17. 3. Parasitism • Parasite benefits • Host is harmed

18. III . Ecological Succession - series of predictable changes that occurs in a community over time Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community.

19. Ecological succession – the gradual development of a community over time • Primary succession A. No life forms (bare rock)

20. B. Lichens • Pioneer species – 1st organisms to inhabit area • Breakdown rock a. Acid b. Dead lichens form soil

21. C. Mosses & other tiny organisms 1. Remains add to soil

22. D. Soil thickens • Ferns replace moss • Grass & wildflowers • Shrubs & small trees

23. E. Forest 1. 100’s - 1000’s years

24. II. Secondary succession • Existing community destroyed (Soil remains) 1. Fire 2. Flood 3. Clear-cutting

25. B. Weeds & crabgrass

26. C. Larger weeds

27. D. 10 – 15 years small trees

28. E. Large forest (hardwood trees)

29. C. Succession in a Marine Ecosystem • Succession can occur in any ecosystem, even in the permanently dark, deep ocean. • In 1987, scientists documented an unusual community of organisms living on the remains of a dead whale. • The community illustrates the stages in the succession of a whale-fall community.

30. Succession begins when a whale dies and sinks to the ocean floor. Fig. 4 – 9 page 96

31. Within a year, most of the whale’s tissues have been eaten by scavengers and decomposers.

32. The decomposition of the whale’s body enriches the surrounding sediments with nutrients. • When only the skeleton remains, heterotrophic bacteria decompose oils in the whale bones. • This releases compounds that serve as energy sources for chemosynthetic autotrophs. • The chemosynthetic bacteria support a diverse community of organisms.

33. Organisms in ecosystems are affected by both biotic and abiotic factors. Biotic factors are all of the living things with which organisms interact. Abiotic factors are nonliving, physical things. They include temperature and soil type. Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which an organism lives. 4–2 What Shapes an Ecosystem?

34. A habitat is the area where an organism lives. A habitat has both biotic and abiotic factors. A niche includes all of the abiotic and biotic things in an organism’s habitat and the way the organism uses those things. For example, a niche includes what an organism eats and how it gets its food.

35. Community interactions, such as competition, predation, and symbiosis, can powerfully affect an ecosystem.• Competition occurs when living things try to use the same resources. Competition often results in one organism dying out.• Predation occurs when one organism (the predator) captures and eats another (the prey).• Symbiosis occurs when two species live close together in one of three ways.1. Mutualism: Both species benefit from the relationship.2. Commensalism: One species benefits. The other is neither helped nor harmed.3. Parasitism: One species benefits by living in or on the other. The other species is harmed.

36. Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. Ecological succession is the series of predictable changes that occur in a community over time.• Primary succession takes place on bare rock surfaces where no soil exists. Pioneer species are the first species to live in these areas.• Secondary succession occurs when a disturbance changes a community without removing the soil.