Community Ecology Amy Brown Science Stuff May 2012

Community Interactions Community: A community is all of the living organisms found in a particular area. When organisms live in communities, they _______ interact constantly and have a powerful effect on the ecosystem _____.

Different types of community interactions include: 1. 2. 3. 4. 5. 6. Competition Predation Symbiosis Mutualism Commensalism Parasitism

Competition occurs when organisms of the same or different species: attempt to use the same ecological resource in the same place at the same time.

What is a resource? A resource refers to anything that is required for life. Resources might include: food, water, light, nesting sites, or room to grow.

When organisms are competing for the same resource, there is often a winner and a loser ________. The winner thrives and the loser fails to survive. This is called the: “competitive exclusion principle. ” This invasive kudzu smothers and strangles any other plant in its path.

Competitive Exclusion Principle: No two species can occupy the same niche in the same habitat at the same time. In competitive exclusion one species is _____ eliminated from a community because of _____ competition for the same limited resource ________. Usually one species uses the resource eliminated more _____, efficiently and the other species is _____.

Occasionally, when two species are intense competitors _________, one or both species may evolve: niche differences or anatomical differences that lessen the intensity of the competition. This phenomenon is called character displacement.

Example of character displacement: Finches have different size _____ depending on the type of beaks seed they eat. _____ Two species of finches that are very similar to one another live in the various islands making up the Galapagos Islands. When these two species live on _______ separate islands and have no competition with each other, they have the same _____. beak size _____ But on an island where both birds are found, their beak sizes are ____. different They have evolved a __________ character displacement that enables them to feed on _________. different-sized seeds Competition is reduced between the two species.

Competition is most intense between: closely related species that require the same resources. When similar species coexist, each species uses: only part of the available resources. This pattern of resource use is called resource partitioning.

Example of resource partitioning: There are five different species of warblers that live in spruce and fir trees. They all feed on: the same type of insects. Each kind of warbler hunts for insects only in: a particular section of the tree. As a result, competition among the three species is reduced.

When can two similar species coexist successfully in the same community? Answer: Only when there is enough difference in their niches.

What are two possible outcomes of competition between species having identical niches? Answer: Either the less competitive species will be driven to local extinction, or one of the species may evolve enough through natural selection to use a different set of resources.

Predation is an interaction in which one organism captures and feeds on another organism. The predator is: the organism that does the killing and eating. The prey is: the food organism. Predation is a powerful force in the community. Predation determines relationships in _____ food webs and population size is a very effective regulator of _______.

Natural selection favors adaptations that make organisms…. …. better suited for their environment. Predators have become more efficient tools over time by developing _____ (through natural selection) that make better predators them _______. Examples: Snakes have heat sensitive pits to help them locate prey. Predators may have acute senses, fangs, claws, poison, stingers, and sharp teeth. Spiders have webs to catch their prey.

Just as the predator must be highly adapted to catch the food, the prey must have: adaptations that help them avoid being captured and eaten. a) The prey may have the ability to run very fast to escape the predator. b) The prey may be camouflaged to avoid detection. c) The prey may have poisons that are advertised by bright warning colors.

Mimicry is a form of deception used by the prey as a means of defense against being eaten. In mimicry, a harmless species resembles a poisonous or distasteful species. The king snake is a mimic of the very poisonous coral snake. Coral snake King snake

Monarch The viceroy butterfly mimics the monarch butterfly. Birds avoid eating the Viceroy monarchs due to their very bitter taste. The viceroy does not have a bad taste, but since it resembles the monarch, birds are reluctant to eat it.

Herbivores are: animals that eat plants. This makes the herbivore a: predator on plants. Through natural selection, plants have developed adaptations that: protect them from being eaten by animals. Plants and Herbivores Plants may have: sharp spines, thorns, sticky hairs, and tough leaves Plants may also produce: chemical compounds that are poisonous, or bad tasting.

Can you give an example of each of the predator-prey combinations listed in the table below? A lion kills and eats a zebra. The zebra grazes on grasses. Athlete’s foot or ringworm. A strep infection. Blights and mildews.

Symbiotic Relationships between Organisms Symbiosis is a close and permanent relationship between organisms of different species. There are three types of symbiotic relationships: • Mutualism • Commensalism • Parasitism

In mutualism: both species benefit from the relationship. This bird eats the ticks on the back of the antelope. Flowers and insects have a mutualistic relationship. The flower provides the insect nectar and the insect with ______, helps the flower to reproduce by spreading pollen ______.

Termites have a particular bacterium that lives in their gut. The bacteria help to digest the wood eaten by the termite, and the termite provides the bacteria with: shelter, warmth, water, and food.

Some mutualistic relationships are so close: that neither species can survive without the other. One such example is the ants that live in the acacia shrubs. The ants nest inside the acacia’s large thorns and receive ____ food from the plant. The ants protect the acacia from: predation by herbivores.

Commensalism is the relationship between two different species in which: one species benefits from the relationship. The other species is neither harmed nor helped. The large fish seen here is called a triggerfish. The triggerfish is able to move large rocks that create feeding opportunities for the smaller fish. There is no benefit to the triggerfish.

Barnacles are mollusks that attach to the skin of whales. The barnacle does not ____ hurt the whale nor help the whale. does it ____ The barnacle is a filter feeder and benefits from ____ the constant flow of water.

Parasitism is the relationship between: two different species in which one species is helped and the other species is harmed. Parasitism tapeworm nutrition The parasite obtains its _____ host from the other organism, the ____. flea

Ectoparasites are…. . external parasites. They live on their host but ______ do not enter the host’s body. Examples include: ticks, fleas, and lice.

Endoparasites are…. . internal parasites. These live ______ inside the host’s body. Examples include: Some bacteria, some protists, and intestinal worms such as tapeworms.

Species Richness: This is the number of different species found in the community.

Species Diversity: Community 1 has greater species diversity. This is the relationship between the number of species in the community to the relative abundance of each species.

Species richness varies latitude with _______. Species richness is greatest in the tropical rain forests. As a general rule, the closer a equator the community is to the _______, more species it will contain. ______

The Species-Area Effect A pattern of species richness is that: larger areas usually contain more species than smaller areas do. This relationship is called the species-area effect.

Why does species richness increase with increasing area? Larger areas usually contain a greater diversity of habitats and thus can support more species.

There is a very important consequence of the species-area effect. Reducing the: size of a habitat reduces the number of species it can support. Habitat destruction __________ by an ever-growing human population is occurring at a faster and faster rate each day. Currently, about ____ 2% of the tropical rain forests are destroyed each year.

The extinction of species!! What is the result of habitat destruction?

Disturbances A disturbance is: an event, such as a storm, fire, flood, drought, overgrazing, or human activity that changes a community by removing organisms from it or altering resource availability.

Human activities that cause the greatest disturbance to communities include: Agricultural development Logging and clearing Mining and farming

Succession is: the gradual, sequential regrowth of an area following a disturbance. There are two types of succession: ü Primary succession ü Secondary succession

Primary succession is: the development of a community in an area that has not previously supported life. Primary Succession

Examples might include: a bare rock, a sand dune, or an island formed by volcanic eruption.

Primary succession often occurs very ______ slowly because: the minerals necessary for plant growth are unavailable. Over time, rocks will begin to break down due to _____. weathering

Lichens are usually the first to colonize these barren areas. (A lichen is the mutualistic relationship between an algae and a fungus. )

The combination of ____ minerals from rocks, and the _________ dead organic matter from the lichens will begin to form a thin layer of ____ soil grass-like in which a few_____ organisms can grow. As these plants die, they add more decayed organic matter to the soil and soon a few shrubs will appear. The shrubs are then followed by trees.

This is: the replacement of species that follows a disturbance in an already existing community. Secondary Succession

The disruption may occur from: a natural disaster such as a forest fire or a strong storm, or from human activities such as clear-cutting, mining or farming. The disturbance has left: the existing soil intact.

Pioneer Species These are the organisms that are generally the first to colonize the area. They appear: early in succession. These organisms tend to be: small, fast growing, and very fast at reproduction.

These organisms have: adaptations that make them well suited to invading and occupying a new area. For example, they may be very good at seed dispersal, or have adaptations that allow them to withstand harsh conditions.

Climax Communities In succession, the community proceeds through a series of stages until it reaches: a stable end point called the climax community.

The organisms in each stage of succession physical environment in ways that alter the _________ make it ____ less favorable for themselves but more ____ favorable for the organisms that follow. The climax community: remains constant for a long period of time.

Succession in a Marine Ecosystem (Whale-Fall Community) The deep dark ocean floor is a: barren, inhospitable environment. Succession can take place even in this environment when a _____ disturbance occurs. The disturbance begins when: a large whale dies and sinks to the barren ocean floor.

The whale carcass attracts: many scavengers and decomposers that begin to feast on the decaying carcass.

Within a year, most of the whale’s tissues will have The decomposition ______ of the carcass ______ has enriched the surrounding been _____ eaten and sediments, attracting: only a much smaller a new population of sediment community of dwellers such as marine worms. organisms: can be supported.

When only the skeleton remains…. . a third community moves in. Heterotrophic bacteria begin to: decompose oils inside the whale bones. This releases chemical compounds that can be used by: chemosynthetic bacteria.

The chemosynthetic bacteria can support a diverse community of: mussels, snails, worms, crabs, and clams.