Ecology Final

Communities

Groups of interacting species that occur together at the same place and time. Physical characteristics e.g., all species in a sand dune, mountain stream, or desert. Biological characteristics e.g., all the species associated with a kelp forest or a coral reef; implies importance of abundant species.

Taxonomic affinity

Organisms that are closely related to each other. Lineage. Diverge from a common ancestor. (E.g. all bird species in a community)

Guild

a group of species that use the same resources. Bat, humming bird and honey bee are all pollinators and feeding on nectar.

Function group

species that function in similar ways. Ex. symbiotic relations with nitrogen-producing bacteria that live in their root nodules.

Food webs

organize species based on trophic or energetic interactions

Trophic levels

Primary producers (autotrophs)
Primary consumers (herbivores)
Secondary consumers (carnivores)
Tertiary consumers (carnivores)

Interaction webs

more accurately describe both trophic (vertical) and non-trophic (horizontal) interactions.

Community structure

set characteristics that shape communities. Provides basis for generating hypotheses and experiments to understand how communities work. Species diversity is the most common measure of community structure.

Species diversity

mean the number of species in a community.
Species richness (number of species)
Species evenness (relative abundance)

Biodiversity

describes diversity at multiple spatial scales, from genes to species to communities. Implicit is the interconnectedness of all the components.

Rank abundance curves

plot the proportional abundance of each species (pi) relative to the others, in rank order. Suggests possible species interactions. Experiments that add or remove species are used to explore these relationships.

Species accumulation curves

species richness plotted as a function of total number of individuals counted. Help determine when most or all of the species in a community have been observed. The threshold where no new species are counted never occurs in natural systems because new species are constantly being found.

Species composition

identity of species in a community. Two communities could have identical species diversity values but completely different species. The identity of species is critical to understanding community structure.

Interspecific Competition

An interaction in which individuals of different species are harmed by their shared use of a resource that limits their ability to grow, reproduce, or survive. (Between members of different species)

Intraspecific competition

An interaction in which individuals of the same species are harmed by their shared use of a resource that limits their ability to grow, reproduce, or survive. (Between individuals of a single species)

Fundamental niche

The full set of resources, plus other biotic and abiotic requirements of a species, that are suitable for a species excluding the negative interactions with other species.

Realized niche

The part of a fundamental niche that species occupies as a result of species interactions.

Exploitation competition

An interaction in which species compete indirectly through their mutual effects on the availability of a shared resource. (Individuals reduce the supply of a resource as they use it, i.e., Pitcher plants)

Interference competition

An interaction in which species compete directly by performing antagonistic actions that interfere with the ability of their competitors to use a resource that both require, such as food or space.

Allelopathy

A mechanism of competition in which individuals of one species release chemicals that harm individuals of other species. (Plants of one species release toxins that harm other species.)

Amensalism

A species interaction in which individuals of one species are harmed while individuals of the other species do not benefit and are not harmed (-/0 relationship).

Competitive exclusion

Dominant species prevents another species from using essential resources; the inferior species may become locally extinct.

Competitive coexistence

The ability of two or more species to coexist with one another despite competing ofr the same limiting resources.

Competitive exclusion principle

Two species that use a limiting resource in the same way cannot coexist indefinitely.

Resource partitioning

The use of limiting resources by different species in a community in different ways. (Species using a limited resource in different ways can coexist.)

Character displacement

A process in which competition causes the phenotypes of competing species to evolve to become more different over time, thereby easing competition. (When two species compete for resources natural selection may favor phenotypes that allow them to partition resources, decreasing competition intensity.)

Direct interactions

An interaction that occurs between two species, such as predation, competition, or a positive interactions. (Occur between two species (e.g., competition, predation, facilitation))

Indirect interactions

Relationship between two species is mediated by a third (or more) species; often discovered when species are removed to study direct interactions.

Trophic cascade

A change in the rate of consumption at one trophic level that results in series of changes in species abundance or composition at lower trophic levels. (Rate of consumption at one trophic level results in change in species abundance or composition at lower trophic levels.)

Trophic facilitation

An interaction in which a consumer is indirectly facilitated by a positive interaction between its prey or food plant and another species.

Foundation species

A species that has a large, community-wide effects on the habitat or food of other species by virtue of size or abundance. (Large or abundant species, such as trees, that provide food or habitat for other species.)

Trophic efficiency

Amount of energy at one trophic level divided by amount of energy at the next lowest trophic level

Allochthonous inputs

Inputs produced outside the ecosystem.

Autochthinous energy

Energy produced within the ecosystem.

Trophic pyramids

portray the relative amounts of energy ir biomass in each trophic level

Consumption efficiency

proportion of available energy ingested - higher in aquatic ecosystems than in terrestrial ecosystems.

Assimilation efficiency

proportion of ingested food that is assimilated. Depends on food quality and consumer physiology.

Production efficiency

Proportion of assimilated food that goes into new consumer biomass. Related to thermal physiology and size of consumer.

Niche Partitioning

using different aspects of the resource. Change in the phenotypes in the organisms due to how they are displaced excreting selection pressure on each other - evolutionary changes for character displacement. 

Define the difference between exploitation and interference compeitition

Analyze how and why competition can vary in its intensity

Describe the importance of competition within communities

Define the competitive exclusion principle and explain how it differs from competitive

Define and give examples of resource partitioning (or niche partitioning)

Describe how competition can lead to character displacement and resource partitioning

Describe how herbivores or predators can change or reverse the outcome of competition

Explain how the physical environment can affect the outcome of competition and distribution of species

Explain how disturbances can allow coexistence in highly asymmetrical competitive interactions

Define and quantify species diversity and compare biodiversity

Define and quantify species diversity and compare biodiversity

Define and graph rank abundance and species accumulation relationships.

Define species composition and explain why it is an important characteristic of communities

Compare direct versus indirect species interactions and describe the effects they have on communities.

Explain how species interactions can vary in strength and direction, and how these attributes can be measured experimentally.

Strength:

Compare foundation species, keystone species, and ecosystem engineers and the effects they have on communities under different environmental contexts

Keystone species: have strong effects because of their role in a community (ex. otters)
Foundation species: Large, abundant species that provide food or habitat for other species. Species that “are the environment” (ex. trees)
Ecosystem engineers: Actively change the environment, physically (ex. Beaver)

Describe how energy flow among trophic levels in an ecosystem is related to the food selection consumers

Explain how both primary production and detritus can be at the base of food chains

They can only be eaten.

Evaluate how terrestrial detrital energy inputs from outside an ecosystem (allochthonous) would change in a river from its source to where it reaches the ocean

Allocating energy in different areas.

Describe how the relationship between biomass and energy is influenced by the life span of primary producers

Shorter life span, abundant, more energy.

Summatize the factors that may influence why a greater proportion of net primary production is consumed in aquatic ecosystems relative to terrestrial ecosystems

Evaluate how consumer thermal physiology, body size, diet preference, and digestive specialization can determine trophic efficiency

Based on diet.

Compare the factors that influence energy flow in an ecosystem between bottom-up and top-down perspectives

Consumption, fitness, birth rates,

Describe how changes in the abundance of organisms at the fourth trophic level may impact rates of primary production through a trophic cascade

Explain how the size of an ecosystem, the rates of disturbance, and the amount of primary production can influence the number of trophic levels

Explain how food webs are helpful for envisioning ecosystem energy flow, and outline the factors that compromise their accuracy in portraying the full extent of interactions among organisms

Describe how the use of interaction strengths can aid in the construction of more accurate food web models

general strength of individual interactions those are the primary ones. Impact strengths shows how much of an important certain organisms have in each other. In cooperate it into an equation, understanding which one has a greater strength.

Summarize how ecologists have viewed the relationship between the complexity of food webs and the stability of associated communities and ecosystem processes

More complex food webs = stable community