Chapter 54 Ecology

can also be thought of as an organism's ecological role. Ecologically similar species can coexist in a community if there are one or more significant differences in their niches. Strong competition can lead to competitive exclusion, local elimination of a competing species. The competitive exclusion principle states that two species competing for the same limiting resources (niche) cannot coexist in the same place.

It is the differentiation of ecological niches, enabling similar species to coexist in a community. Competition for resources has to exist and there is a tendency for animals to specialize. Two things can happen when there is competition 1. Species exclusion 2. Resource portioning. Resource portioning happens when species compete for food and one is better than the other at eating the one thing and therefore the other one must adapt to eating something else

Character displacement is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species. This is how you can prove that resource portioning has happened due to competition. Species A was in one island it had all resources available and same thing for species B on the other island. When you bring them together it could be that species A is better at eating seeds and therefore species B cannot compete. Species B is then better at eating bugs.

Prey behavioral defenses include hiding, fleeing, forming herds or schools, self-defense, and alarm calls. Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison. Animals also have morphological and physiological defense adaptations

camouflage

two or more untasty resemble each other

a tasty or harmless species mimics an untasty or harmful mode

Animals with effective chemical defense often exhibit bright warning coloration

pattern makes them disappear from the background

1st trophic level (autotrophs-create organic matter, they are the base of the pyramid and they decide how far up the pyramid will move)

Primary consumers- 2nd trophic level (herbivores that eat the primary producers)

Secondary consumers- 3rd trophic level (carnivores)

4th trophic level (Carnivores that eat other carnivores)

break down any organic matter

suggests that length is limited by inefficient energy transfer.

proposes that long food chains are less stable than short ones

Energetic Hypothesis

they exert powerful control over the occurrence and distribution of other species. All of these species are keystone species because there is no way that animals that are found in large numbers would not have an affect on the ecosystem

these species exert strong control on a community by their ecological roles, or niches. Not all these species are dominant species

these species are species that provide habitat for a lot other species (like trees). Some species act as facilitators that have positive effects on survival and reproduction of some other species in the community (they may affect some species negatively as well). Some species are dominant species and some are not. They are all keystone species

proposes a unidirectional influence from lower to higher trophic levels. In this case, presence or absence of mineral nutrients determines community structure, including abundance of primary producers.

also called the trophic cascade model, proposes that control comes from the trophic level above. In this case, predators control herbivores, which in turn control primary producers

The top-down model proposes that control comes from the trophic level above. In this case, predators control herbivores, which in turn control primary producers

suggests that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance. High levels of disturbance exclude many slow growing species and low levels of disturbance allow dominant species to exclude less competitive species

the sequence of community and ecosystem changes after a disturbance. Early-arriving species and later-arriving species may be linked in one of three processes: Early arrivals may facilitate appearance of later species by making the environment favorable. They may inhibit establishment of later species (later succession can happen despite of it). They may tolerate later species but have no impact on their establishment.

occurs where no soil exists when succession begins

begins in an area where soil remains after a disturbance

Humans have the greatest impact on biological communities worldwide. Human disturbance to communities usually reduces species diversity. Humans also prevent some naturally occurring disturbances, which can be important to community structure.

Latitude and area are two key factors that affect a community's species diversity.

These pathogens have been transferred from other animals to humans. The transfer of them can be direct or through an intermediate species called a vector. The pathogen of zoonotic diseases has a complete life cycle in non-human animals but can sometimes infect humans. An example is Avian flu which is a highly contagious virus of birds.

They can have dramatic effects on communities. For example, coral reef communities are being decimated by white-band disease, also sudden oak death.

Disease-causing organisms, including: protozoans, bacteria, viruses, viroid, prions, etc. They can alter community structure quickly and extensively.

Species richness generally declines along an equatorial-polar gradient and is especially great in the tropics. Two key factors in equatorial-polar gradients of species richness are probably evolutionary history and climate.

species richness increases with island size.

Species richness on islands depends on island size, distance from the mainland, immigration, and extinction. The equilibrium model of island biogeography maintains that species richness on an ecological island levels off at a dynamic equilibrium point.

Ecologists are studying the potential spread of the virus from Asia to North America through migrating birds.