Outline 4-2: What Shapes an Ecosystem? Photo Credit: ©Michael Fogden/DRK PHOTO Copyright Pearson Prentice Hall

Biotic and Abiotic Factors Ecosystems are influenced by a combination of biological and physical factors. The biological influences on organisms within an ecosystem are called biotic factors. Biotic factors include all the living things with which an organism might interact. Copyright Pearson Prentice Hall

Biotic and Abiotic Factors Physical, or nonliving, factors that shape ecosystems are called abiotic factors. Abiotic factors include: temperature precipitation humidity wind nutrient availability soil type sunlight Copyright Pearson Prentice Hall

Biotic and Abiotic Factors How do biotic and abiotic factors influence an ecosystem? Biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives. Biotic and Abiotic Factors Copyright Pearson Prentice Hall

Biotic and Abiotic Factors The physical area where an organism lives is called its habitat. A habitat includes both biotic and abiotic factors. It might include different areas (forest, prairie, lakes, etc.) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche The Niche A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. Includes: How it uses space Feeding habits (herbivore, carnivore, etc.) Reproductive behavior Moisture requirements Temperature requirements Competition with other organisms Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Crested auklet occupies the same niche in the Arctic that penguins do in the Antarctic. The aye-aye occupies the same niche as typical woodpeckers. They chew into tree stems and then use long middle finger to get insects out of wood Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Aspects of Niches The entire range of conditions an organism is potentially able to occupy within an ecosystem is called its fundamental niche. The part of its fundamental niche that a species actually occupies is called its realized niche. This might be only a small portion of its fundamental niche. Different species can coexist in the same habitat if they occupy very similar, but slightly different, niches. Copyright Pearson Prentice Hall

Community Interactions When organisms live together in ecological communities, they interact constantly. Various types of such interactions are: competition predation various forms of symbiosis. Copyright Pearson Prentice Hall

Community Interactions 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. Two types of competition: Intraspecific competition Between members of the same species 2. Interspecific competition Between members of different species Copyright Pearson Prentice Hall

Community Interactions Direct competition in nature often results in a winner and a loser—with the losing organism failing to survive. The competitive exclusion principle states that no two species can occupy the exact same niche in the same habitat at the same time. If you force two very similar species to live in the same exact habitat one of them might go extinct. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Experiment on Paramecium Competition When P. aurelia and P. caudatum had to live in the same lab environment and eat the same food, one species always went extinct: P. aurelia always won the competition P. caudatum always went extinct. Copyright Pearson Prentice Hall

Community Interactions Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche How is a small realized niche helpful to species? Robert MacArthur (1950s) suggested that this can reduce competition between species: The organisms essentially “carve up” the available resources. This is called resource partitioning. Examples: Warblers in forest Barnacles on rocky coastlines Copyright Pearson Prentice Hall

Community Interactions The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree. 18 12 Feeding height (m) Cape May Warbler Each of these warbler species has a different niche in its spruce tree habitat. By feeding in different areas of the tree, the birds avoid competing with one another for food. Bay-Breasted Warbler 6 Yellow-Rumped Warbler Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Barnacle Competition Two species of barnacles live on rocks off the coast of Scotland: 1. Chthamalus stellatus Live in shallow water; exposed to air when the tide goes out 2. Semibalanus balanoides Live in deeper waters; usually covered with water & rarely exposed to air Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Chthamalus Semibalanus Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Joseph Connell’s Experiment on Barnacles He removed Semibalanus from deeper water Chthamalus then was able to move down to deeper water and live covered by water He later reintroduced Semibalanus to deep water The Chthamalus then got crowded back up When he placed Semibalanus in shallow water they could NOT survive Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Niche Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Predation Predation An interaction in which one organism captures and feeds on another organism is called predation. The organism that does the killing and eating is called the predator, and the food organism is the prey. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Predation Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Predation Predators can lessen competition Robert Paine studied sea star & its prey species (clams, mussels) Originally there were 15 prey species If he kept the starfish out of experimental plots he found only 8 prey species 7 clam species crowded out by the mussels Thus, predators can help to promote biodiversity, variety of species present in a community Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Plants & Herbivores Plants protect themselves with: Thorns, spines Defensive chemicals called secondary compounds (mustard oil) Many herbivores can feed on plants that are protected by chemicals: Larvae of cabbage butterfly eat mustard Larvae of Monarch butterflies eat milkweed & become poisonous Copyright Pearson Prentice Hall

Milkweed plant & Monarch butterflies

Community Interactions Symbiosis Any relationship in which two species live closely together is called symbiosis. Symbiotic relationships include: mutualism commensalism parasitism Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mutualism A symbiotic relationship in which both organisms benefit Examples: Aphids and ants Lichens (fungus & green algae) Bacteria in digestive tract of cattle Cleaner fish Copyright Pearson Prentice Hall

Ants taking care of aphids

Lichens

Cleaner Fish in mouth of Moray Eel

Copyright Pearson Prentice Hall Commensalism A symbiotic relationship in which one organism benefits & the other is neither harmed or helped Examples: Barnacles living on skin of whales Epiphytes = plants that grow on other plants (orchids) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Barnacles on Whales Copyright Pearson Prentice Hall

Epiphytes & Orchids

Copyright Pearson Prentice Hall Parasitism A close, long-term symbiosis in which one organism obtains its nutrition from another living organism (lives on or in it) Parasite = organism that is receiving the benefit Host = organism that is being harmed Parasites don’t usually kill their host Examples: tapeworms, mistletoe, ticks Copyright Pearson Prentice Hall

Tick Mistletoe Tapeworm

Copyright Pearson Prentice Hall Coevolution Reciprocal evolutionary adjustments between interacting members of an ecosystem. Example: Flowering plants depend on animals to disperse their pollen The pollinating animals have adaptations that allow them to obtain food or other resources from the flower Long beaks of hummingbirds Copyright Pearson Prentice Hall

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Ecological Succession 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. Copyright Pearson Prentice Hall

Ecological Succession This series of predictable changes that occurs in a community over time is called ecological succession. Sometimes, an ecosystem changes in response to an abrupt disturbance. At other times, change occurs as a more gradual response to natural fluctuations in the environment. Copyright Pearson Prentice Hall

Ecological Succession Primary Succession On land, succession that occurs on surfaces where no soil exists is called primary succession. For example, primary succession occurs on rock surfaces formed after volcanoes erupt. The first species to populate the area are called pioneer species. Copyright Pearson Prentice Hall

Ecological Succession In this example, a volcanic eruption has destroyed the previous ecosystem. Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Copyright Pearson Prentice Hall

Ecological Succession The first organisms to appear are lichens. Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Copyright Pearson Prentice Hall

Ecological Succession Mosses soon appear, and grasses take root in the thin layer of soil. Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Copyright Pearson Prentice Hall

Ecological Succession Eventually, tree seedlings and shrubs sprout among the plant community. Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. Copyright Pearson Prentice Hall

Ecological Succession Secondary Succession Components of an ecosystem can be changed by natural events, such as fires. When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession.  Copyright Pearson Prentice Hall

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Ecological Succession Healthy ecosystems usually recover from natural disturbances, but may not recover from long-term, human-caused disturbances. Copyright Pearson Prentice Hall

Ecological Succession 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. Copyright Pearson Prentice Hall

Ecological Succession Succession begins when a whale dies and sinks to the ocean floor. Ecosystems are constantly changing in response to disturbances. In natural environments, succession occurs in stages. A dead whale that falls to the ocean floor is soon covered with scavengers. Copyright Pearson Prentice Hall

Ecological Succession Within a year, most of the whale’s tissues have been eaten by scavengers and decomposers. Copyright Pearson Prentice Hall

Ecological Succession 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. Copyright Pearson Prentice Hall