Species Interactions & Community Ecology

Flashcards covering ecological terms, species interactions, competition principles, community hypotheses, and the process of succession as described in the lecture notes.

Primary Producers

Photosynthetic autotrophs, such as plants and cyanobacteria, that serve as the main source of energy and oxygen in most communities.

Primary Consumers

Organisms in a food chain that eat primary producers to obtain energy.

Secondary Consumers

Organisms in a food chain that eat primary consumers.

Detritus Feeders and Decomposers

The main components in food chains that process dead organic matter.

Predation

An interaction where the predator gains nutrients and energy ($+$) and the prey is killed ($-$).

Parasitism

A relationship between two organisms where the parasite thrives at the cost of the host ($+/-$), who is injured or killed.

Herbivory

An interaction where herbivores gain nutrients and energy ($+$) and plants are killed or injured ($-$).

Competition

An interaction where both populations lose access to some resources ($-/-$).

Commensalism

An interaction where one population benefits ($+$) and the other population is unaffected ($0$).

Mutualism

An interaction where both populations benefit ($+/+$).

Symbiosis

A physically close ecological association between one species and another; the term is derived from "sym" (together), "bio" (life), and "sis" (process).

Endoparasites

Parasites that live within the host.

Ectoparasites

Parasites that live on the exterior of the host.

Parasitoids

Insects whose lifestyle falls between true parasitism and predation.

Carnivory

A type of predation involving the devouring of meat (from "caro" = meat and "vorare" = to devour).

Intraspecific Competition

Competition for limiting resources such as food and shelter among individuals of the same species.

Interspecific Competition

Competition for the same limiting resources between individuals of different species.

Interference Competition

Directly harmful interaction where one species displaces another, such as lions chasing off smaller predators from kills.

Exploitative Competition

An interaction where two or more populations use the same limiting resource, thereby reducing resource availability for others.

Competitive Exclusion Principle

The principle that two or more species cannot co-exist indefinitely if they rely on the same limiting resources and exploit them in the same way.

Ecological Niche

The resources a species uses and the environmental conditions it requires for survival.

Fundamental Niche

The entire set of conditions under which an animal population can survive and reproduce itself.

Realized Niche

The actual niche that a species occupies in the presence of limiting factors such as competition.

Resource Partitioning

The use of different resources or the same resources in different ways to allow species to coexist.

Character Displacement

An evolutionary change where two similar species inhabit the same environment and natural selection favors a divergence in characters.

Keystone Species

A species that has a much greater effect on community structure than its numbers suggest, such as the sea star $Pisaster$.

Ecotone

The border or transition zone between two ecological communities.

Interactive Hypothesis

A hypothesis predicting that species within communities exhibit similar distributions along environmental gradients and have sharp boundaries.

Individualistic Hypothesis

A hypothesis predicting that species distributions along a gradient are independent and lack sharp boundaries between communities.

Species Diversity

A measure reflecting both species richness (the number of species) and the relative abundances of those species.

Shannon Index ($H'$)

A metric used to calculate species diversity within a community.

Evenness ($E_H$)

A measure of the relative abundance of different species making up the richness of an area.

Detritivores

Animals and scavengers that feed on dead or dying organic matter.

Primary Succession

The change in an ecosystem over time that occurs when organisms first colonize habitats without soil, such as after volcanic activity or glacial retreat.

Secondary Succession

The sequence of changes that occurs after existing vegetation is destroyed or disrupted by an environmental disturbance like fire.

Pioneer Species

The first species to establish themselves on nutrient-poor soil during succession, such as mountain avens (genus $Dryas$).