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:
Community Ecology Community Ecology
Community: a group of populations living and inter- acting with each other in the same area Everglades community Coral Reef community
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.
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.
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.
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
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)
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.
Herbivory - animals eating plants. Sheep and horses graze on plants; they are herbivores. Many insects, such as aphids and caterpillars, eat plants.
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
Predation – one species (the predator) eats another species (the prey). Owls are predators of small animals. A preying mantis eats other insects.
Adaptations of teeth to a particular niche Note differences:
Symbiosis - two different species living together intimately. Does not include eating relationships. Includes parasitism, mutualism, & commensalism.
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.
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
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.
Mutualism – both species benefit from their interaction. Plants provide food for pollinators, which help plants reproduce. Animals disseminate fruits.
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.
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.
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.
Commensalism – one species benefits; the other is neither helped or hurt. Barnacles ride on whale’s body to new food sources. Whale is unaffected.
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.
Ecological Succession Succession
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.
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.
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.
Primary succession begins in a lifeless area - no soil. Ex: volcanic eruption The island of Surtsey off southern Iceland rose from the sea in
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.
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.
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
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
Biodiversity declines after a catastrophe, whether natural or man-made. We always assume Earth can recover.