BIOL112 - Ecology (Set 6)

Lectures 26 & 27 - Sepcies Interactions

What are interspecific interactions?

Interactions between individuals of different species.

What are intraspecific interactions?

Interactions between individuals of the same species.

What is mutualism?

An interspecific interaction where both species benefit.

What is amensalism?

An interspecific interaction where one species is harmed, with no cost to the other species.

What is predation?

An interspecific interaction where one species is harmed, and the other is benefitted, this involves the eating of one species by another species for nutrition (there are several subtypes).

(Forms of predation) what is true predation?

Where one species (the predator) kills another (the prey) immediately.

(Forms of predation) what is the effect of parasitism and herbivory?

The effect is usually not lethal or only gradually so, where only part of an individual is removed.

(Forms of predation) what are parasitoids?

A predator which attacks its prey, having its offspring live on and kill the prey, but not immediately.

How do interactions vary in duration and lethality?

Parasites have a long duration and low lethality, parasitoids have a long duration and high lethality, herbivores have a short duration and low lethality, and true predators have a short duration and high lethality.

What are trophic interactions?

The feeding interactions of organisms.

What factors limt population size?

Population density, density-dependent factors, density independent factors.

What are density-dependent factors?

Biological influences that increase with increased population density (e.g. mostly biotic factors such as disease, parasitism, predation, and food shortages).

What are density-independent factors?

Biological influences that are independent of the density of the population (e.g. mostly abiotic factors such as spring freeze, fire, and temperature).

What is competition?

Interactions between individuals who have a shared need for a limited resource.

What is interference competition?

Direct aggressive interaction between individuals.

What is exploitative competition?

Competition to secure resources first.

(Interspecific competition) what is consumption?

Where individuals of one species inhibit indivduals of another by consuming a shared resource.

(Interspecific competition) what is preemption?

Where individuals of one species prevent occupation of an area by individuals of another species.

(Interspecific competition) what is overgrowth?

Individuals of one species grow over individuals of another species, inhibiting access to a resource.

(Interspecific competition) what is chemical interaction?

Individuals of one species release growth inhibitors or toxins that inhibit or kill other species.

(Interspecific competition) what is territoriality?

A behaviour of one species that excludes another species from a specific location that is defended as a territory.

(Interspecific competition) what is an encounter?

Nonterritorial encounters between individuals of different species that affect one or more of the species involved.

What is a niche?

The set of environmental conditions (abiotic and biotic) in which an orgnaism can survive and reproduce.

What is a fundamental niche?

Physical conditions under which a species might live in the absence of interactions with other species.

What is a realised niche?

Physical conditions under which a species might live when restricted by interactions with other species.

What is the exclusion principle?

No two species can occupy the same niche, or they will have niche or resource partitioning.

What dictates a species geographic range?

The variety of optimal conditions for the given species (e.g. temperature, light, depth, salinity, and soil types).

What is a keystone species?

A species that plays a crucial role in maintaining ecosystem structure, preventing other species from taking over an area, and allowing other, less-competitive species to flourish (e.g. sea otters).

What is ecological succession?

The sequence of community and ecosystem changes after a disturbance.

When does primary succession occur?

When no soil exists after the disturbance (e.g. after glaciation or a volcanic eruption).

When does secondary succession occur?

When soil remains after the disturbance (e.g. after fires or landslides).

What is a pioneer species?

The first species to colonise environments damaged by disruptions.

How do disturbances affect species?

The evolution of species and life history traits, along with the ecological responses of species to disturbances.

What kind of species do high levels of disturbance favour?

R-selected species.

What kind of species do low levels of disturbance favour?

K-selected species.

What does the intermediate disturbance hypothesis (IDH) state?

That moderate levels of disturbance allow greater diversity than higher or low levels of disturbance.