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CHAPTER 36 Communities and Ecosystems

CHAPTER 36 Communities and Ecosystems. Modules 36.5 – 36.10. 36.5 Symbiotic relationships help structure communities. A symbiotic relationship is an interaction between two or more species that live together in direct contact

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CHAPTER 36 Communities and Ecosystems

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  1. CHAPTER 36Communities and Ecosystems Modules 36.5 – 36.10

  2. 36.5 Symbiotic relationships help structure communities • A symbiotic relationship is an interaction between two or more species that live together in direct contact • There are three main types of symbiotic relationships within communities • Parasitism • Commensalism • Mutualism

  3. The parasite benefits and the host is harmed in this symbiotic relationship • A parasite obtains food at the expense of its host • Parasites are typically smaller than their hosts • Parasitism is a kind of predator-prey relationship

  4. The rabbits destroyed huge expanses of Australia • They threatened the sheep and cattle industries • In 1950, a parasite that infects rabbits (myxoma virus) was deliberately introduced to control the rabbit population • In the 1940s, Australia was overrun by hundreds of millions of European rabbits Figure 36.5A

  5. Commensalism is a symbiotic relationship where one partner benefits and the other is unaffected • Examples of commensalism • Algae that grow on the shells of sea turtles • Barnacles that attach to whales • Birds that feed on insects flushed out of the grass by grazing cattle

  6. Mutualism is a symbiotic relationship where both partners benefit • Examples of mutualism • Nitrogen-fixing bacteria and legumes • Acacia trees and the ants of the genus Pseudomyrmex Figure 36.5B

  7. 36.6 Disturbance is a prominent feature of most communities • Disturbances include events such as storms, fires, floods, droughts, overgrazing, and human activities • They damage biological communities • They remove organisms from communities • They alter the availability of resources Figure 36.6

  8. Ecological succession is a transition in the species composition of a community following a disturbance • Primary succession is the gradual colonization of barren rocks by living organisms • Secondary succession occurs after a disturbance has removed the vegetation but left the soil intact

  9. 36.7 Talking About Science: Ecologist Frank Gilliam discusses the role of fire in ecosystems • Ecologist Frank Gilliam is especially interested in the role that fire plays in shaping ecosystems • According to Dr. Gilliam, fire is a key abiotic factor in many ecosystems • Grasslands are so dependent on fire that its absence is considered a disturbance Figure 36.7A

  10. Following a fire in southeastern pine forest, the numbers and variety of nonwoody plants usually increase dramatically • Fire makes more nutrients available to these plants Figure 36.7B

  11. ECOSYSTEM STRUCTURE AND DYNAMICS 36.8 Energy flow and chemical cycling are the two fundamental processes in ecosystems • A community interacts with abiotic factors, forming an ecosystem • Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat • Chemicals are recycled between air, water, soil, and organisms

  12. A terrarium ecosystem Chemical cycling(C, N, etc.) Chemicalenergy Heatenergy Lightenergy Figure 36.8

  13. 36.9 Trophic structure is a key factor in ecosystem dynamics • A food chain is the stepwise flow of energy and nutrients • from plants (producers) • to herbivores (primary consumers) • to carnivores (secondary and higher-level consumers)

  14. TROPHIC LEVEL Quaternaryconsumers Carnivore Carnivore Tertiaryconsumers Carnivore Carnivore Secondaryconsumers Carnivore Carnivore Primaryconsumers Herbivore Zooplankton Producers Plant Phytoplankton Figure 36.9A A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN

  15. Decomposition is essential for the continuation of life on Earth • Detritivores decompose waste matter and recycle nutrients • Examples: animal scavengers, fungi, and prokaryotes • Decomposition is the breakdown of organic compounds into inorganic compounds Figure 36.9B

  16. 36.10 Food chains interconnect, forming food webs • A food web is a network of interconnecting food chains • It is a more realistic view of the trophic structure of an ecosystem than a food chain

  17. Wastes anddead organisms Tertiaryandsecondaryconsumers Secondaryandprimaryconsumers Primaryconsumers Producers Detritivores (Plants, algae,phytoplankton) (Prokaryotes, fungi,certain animals) Figure 36.10

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