Environmental Science A. Interactions The Environment

Which term describes a species that has many alternate food sources and that is likely to survive in a changing environment?

A generalized species is one that has a wide niche. Mice and cockroaches are generalized species that survive under many varied environmental conditions because they can change their behavior to fit into new habitats.

Predator

An animal that hunts other animals for food

prey

An organism that is killed and eaten by another organism

Example of Niche similarity

Anolis lizards in the tropics vary only in the size of the insects they eat. Lizards with large jaws eat large insects, and those with small jaws eat small insects. The different species can live side by side because they occupy different niches.

How is competitive exclusion related to the concept of a niche?

Competitive exclusion is the driving out of one species from a niche that two species are trying to occupy

Evolution and Adaptation

Ecosystems change over time. Mountains rise and erode, rivers change course, and climate factors such as temperature and rainfall may vary dramatically. A change in the environment will affect the niches of the organisms in that environment.

Niches

Every organism is adapted to life in its habitat. For example, each organism has special ways of gathering food, reproducing, and avoiding predators. The actions of an organism define its role in the ecosystem. The role of an organism in the ecosystem is called its niche. A niche is more than an organism's habitat; it is also what the organism does within its habitat. A niche includes both biotic and abiotic factors. Some biotic factors that help define a niche are food sources and predators. All members of a species are adapted to the same niche. No two species can share the same niche in the same habitat. Two species can, however, occupy niches that are very similar.

Evolving in a Niche

Evolution causes populations of organisms to be adapted to specific niches in the environment. This reduces competition with other species. For example, there are five species of birds called warblers that live in forests of the northeastern United States. All five species feed on insects in the branches of spruce trees. Although the five species seem to compete with each other for food, each species looks for food in a slightly different part of the tree.

Interactions in Ecosystem

In many ecosystems, the activity of one species can help define a species' niche. Two species of barnacles living on the coast of Scotland have very similar niches. Both species live on rocks in the surf zone of the ocean shore. One barnacle species is Chthamalus stellatus (species A). The other species is Balanus balanoides (species B). Species B lives on lower rocks usually covered by water, except during low tide. Species A occurs on higher rocks that are usually exposed to the air. Species B survives only in lower zones because it is vulnerable to drying out. Species A is more resistant to drying out, so it can survive higher up on the rocks.

Niche Diversity

Niche diversity, the number of different niches in an ecosystem, is often determined by abiotic factors in the environment. In a marsh, for example, there are many organisms. However, there are few different niches because the physical environment in a marsh is fairly constant. By contrast, in a desert ecosystem, there are fewer organisms but many different niches.

Interactions In The Environment 2

Predators play an important role in increasing niche diversity by decreasing the population size of their prey species. If a predator reduces the population of one species, more resources will become available for another species. The action of the predator, therefore, can create another niche.

Why do species such as warblers evolve to avoid competition with other species?

Species evolve to occupy different niches to avoid competing for resources. Competition may lead to competitive exclusion.

What would happen to the ant colony living on an acacia tree if that tree was chopped down?

The ant colony would die if the acacia it lived on was destroyed. In general, a species cannot survive if its habitat is destroyed because the niche it occupies disappears.

realized niche

The niche species actually occupies.

fundamental niche

The niche species could potentially occupy.

How is an organism's niche different from its habitat?

The place where an organism lives is its habitat. The organism's role within its habitat defines its niche.

Evolution

a change in the characteristics of a population of organisms over time. happens when some individuals have genetic variations that allow them to produce more offspring than other members of the population. Over time, these changes, or adaptations, will be passed from generation to generation

keystone predator

a predator species that reduces the density of the strongest competitors in a community, thereby helping maintain species diversity

generalized species

a species with a wide niche has several alternate food sources and is more likely to survive in a changing environment. Generalized species such as mice and cockroaches survive well in areas altered by human activity because they can easily change their behaviors to fit new environmental conditions.

specialized species

an organism with a small niche The koala is another example of a specialized species. It feeds only on the leaves of eucalyptus trees. Specialized species are often vulnerable to extinction; a single environmental change can eliminate their niche. Koalas would quickly become extinct if eucalyptus were no longer able to grow in their habitat.

How are generalized species different from specialized species?

generalized species can adapt and rely on different food sources, while specialized species only survive on one kind of food sources with a potential to adapt and change.

Robert Paine

performed an experiment that showed how predators help to form niches. Paine removed the dominant predator, the sea star, from several tidepools on the coast of Washington state. The number of mussels then increased until the mussels had "outcompeted" many of the other species in the tidepools. Without the sea stars, the number of species living in the tidepools dropped from 15 to 8.

J.H Connell

performed an experiment to study how one barnacle species affects the niche of another. He removed all of species B from a small area of the shore, and then observed the effect of the removal. He found that species A began to grow on the lower rocks. Connell hypothesized that species A could live on all parts of the rocky shore, but that species B drove out A wherever B could survive. Connell realized that the niche of one species could affect the niche of another. For example, the presence of one species might limit the niche of another, as in the case of the barnacles.

Competitive Exclusion

refers to the extinction of one population in one place, not to the extinction of the whole species

convergent evolution

the independent development of similar adaptations in two species with similar niches

coevloution

the process by which species interact so closely with one another that they adapt to one another. an occur as a result of feeding relationships. Plants and caterpillars are an example of such co-evolution. Many plants have poisonous chemicals that prevent insects from eating them. Some caterpillars have the ability to resist these poisons. They can feed on plants that other insects cannot eat. These caterpillars often become specialized and feed only on the poisonous plants.

Niche

the role of an organism in an ecosystem

Which adaptation is the likely result of convergent evolution?

the webbed feet of ducks and frogs