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Community Ecology Community Ecology. Community: a group of populations living and inter- acting with each other in the same area Everglades community.

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Presentation on theme: "Community Ecology Community Ecology. Community: a group of populations living and inter- acting with each other in the same area Everglades community."— Presentation transcript:

1 Community Ecology Community Ecology

2 Community: a group of populations living and inter- acting with each other in the same area Everglades community Coral Reef community

3 The ecological niche is …  the sum total of an organism's use of abiotic & biotic resources in the environment:  its habitat (the place where it is found);  its interaction with organisms within the community;  its position in the movement of energy in a particular ecosystem. Lion: heterotroph, carnivore, consumer of large herbivores, at the top of the food chain on the savannah in C. Africa.

4 The ecological niche is …  an organism’s address and occupation. Bamboo: autotroph, primary producer, food for the Giant Pandas in the Wolong Nature Reserve of southwestern China.

5 The competitive exclusion principle says that two species cannot coexist in a community if their niches are identical.  Competition forces one species to move or die.  Domestic cattle and sheep out-compete native herbivores, such as deer, for food.  Introduced weeds out- compete native plants.  Ex: melaluca trees from Australia in S. Florida take space needed by other organisms.

6 When species interact one usually benefits while the other suffers, but not always. There are several types of interactions:  competition,  herbivory,  predation,  parasitism,  mutualism,  commensalism. Remora on a shark

7 Competition - an attempt to use the same scarce resources.  The interaction is detrimental to both species.  Competitors must adapt, or one loses its niche.  Usually one surrenders a part of the habitat.  Ex. barnacles on rocks at the seashore.  Rarely, one species drives the other away:  Ex: humans compete for space.  Video (populations)

8 Herbivory - animals eating plants.  Animal benefits; plant does not.  Animals often develop specialized teeth for grinding  Plant defenses against herbivores include spines and chemical compounds that are toxic.  Ex: oleander & Digitalis are deadly, but humans develop medicines from these plants.

9 Herbivory - animals eating plants.  Sheep and horses graze on plants; they are herbivores.  Many insects, such as aphids and caterpillars, eat plants.

10 Predation – one species (the predator) eats another species (the prey).  The interaction is beneficial to one species.  Predator adaptations: claws, teeth, fangs, poison, heat-sensing organs, speed, and agility.  Prey adaptations: claws, horns, camouflage, speed, agility, group behaviors (herding), etc. Lions hunting zebras

11 Predation – one species (the predator) eats another species (the prey).  Owls are predators of small animals.  A preying mantis eats other insects.

12 Adaptations of teeth to a particular niche  Note differences:

13 Symbiosis - two different species living together intimately. Does not include eating relationships.  Includes parasitism, mutualism, & commensalism.

14 Parasitism – One organism (the parasite) lives on or in a host & depends on the host for nutrition.  Don’t usually kill the host, unlike a predator; also usually much smaller. (If parasites killed the host quickly they wouldn’t reproduce.)  Malarial blood parasite and intestinal worms weaken humans.

15 Parasitism - predators live on or in a host.  Pathogens are disease-causing organisms that can be considered predators. Bacteria  Streptococcus pyogenes  Staphylococcus aureus  Neisseria gonorrhea Viruses weaken plants & animals  Influenza virus  Polio virus  Tobacco mosaic virus

16 Mutualism – both species benefit from their interaction.  Humans protect their domesticated animals, which provide food and clothing. Dogs return protection and comfort. Humans on horses herding sheep with the help of dogs.

17 Mutualism – both species benefit from their interaction.  Plants provide food for pollinators, which help plants reproduce. Animals disseminate fruits.

18 Mutualism – both species benefit from their interaction.  Lichen: an association of a fungus & cyanobacteria or a fungus & green algae. The fungus absorbs nutrients (like N & P), and algae or bacteria photosynthesize making food.

19 Mutualism – both species benefit from their interaction.  Escherichia coli bacteria in human intestines help us digest food and produce Vitamin K that we can’t make.  Protists in the gut of termites help them digest wood.

20 Commensalism – one species benefits; the other is neither helped or hurt.  Boxing crab pushes stinging sea anemones at predators. Anemone is unaffected; crab benefits. Anemone may get bits of left-over food.

21 Commensalism – one species benefits; the other is neither helped or hurt.  Barnacles ride on whale’s body to new food sources. Whale is unaffected.

22 Amensalism – one species suffers; the other is neither helped or hurt.  Humans dump garbage or waste materials into the river, which hurts the fish, but people are not affected. Antibiosis – one species makes a chemical that inhibits another species living nearby.  Soil bacteria produce toxins that inhibit the growth of other bacteria or fungi – the source of antibiotics.

23 Ecological Succession Succession

24 Definition: A sequence of community changes after a disturbance - a transition in species compo- sition over ecological time.  Primary succession begins in a lifeless area with no soil.  Ex: after a glacier retreats, mosses and lichens colonize first and produce soil by breaking down rock.

25 Primary succession begins in a lifeless area - no soil.  Ex: glacial retreats 1)Lichens and mosses produce soil. 2)First colonists are small, fast-growing plants, like “weeds”. They improve soil, but compete poorly. 3)Next trees and shrubs move in carried by wind and animals.

26 Primary succession begins in a lifeless area - no soil.  Ex: glacial retreats 4) Eventually a climax community is reached that resists invasion from new plants and is stable over long periods of time. These are the biomes: the coniferous forest, savannah, etc.

27 Primary succession begins in a lifeless area - no soil.  Ex: volcanic eruption  The island of Surtsey off southern Iceland rose from the sea in

28 Living organisms change the abiotic environment during succession, making it friendlier.  Soil concentrations of nutrients change over time.  Nitrogen rises from biological fixation by bacteria.  Organic compounds increase as dead plants decay.  Transpiration raises humidity.  Levels of CO 2 and O 2 change slightly.  Reflectance of the ground changes, affecting local temperatures.  The land becomes more hospitable to life.

29 In the case of Mt. St. Helens in Washington, USA, the eruption produced ash, not lava, so there was a type of soil afterward. Plants & animals arrived quickly.

30 Secondary succession occurs after an existing community has been cleared but soil remains.  Ex: after a forest fire, or when pasture or farmland is abandoned and returns to forest. Fire in Yellowstone National Park, 1988

31 Secondary succession – disaster leaves soil intact.  Ex: after a forest fire, or when pasture or farmland is abandoned and returns to forest.  Grasses grow first, then trees and other organisms. Seeds are often in place already – some conifer trees need fire to open cones and release the seeds. Yellowstone Park, 2005

32 Biodiversity declines after a catastrophe, whether natural or man-made. We always assume Earth can recover.

33 Gaia’s breath – the planet lives


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