Ecological Niches, Species Interactions, and Island Biogeography

Phylogenetic Niche Conservatism (PNC)

Closely related species tend to have similar ecological niches due to shared ancestry.

Community

A group of interacting populations of different species living in the same area.

Antagonistic Interaction

An interaction where one species benefits and the other is harmed (e.g., predation, parasitism, competition).

Fundamental Niche

The full range of environmental conditions and resources a species can occupy without competition or predators.

Competitive Exclusion Principle

Two species cannot occupy the same niche in the same place at the same time; one will outcompete the other.

Resource Partitioning

Process by which species with overlapping niches evolve to use different resources or habitats, reducing competition.

Ecological Niche

The sum of habitat requirements a species needs for survival and reproduction and the role it plays in its community.

Realized Niche

The actual portion of the fundamental niche a species occupies when limited by interactions such as competition or predation.

Convergent Evolution

Unrelated species evolve similar traits because they live in similar niches under similar selection pressures.

Predation

One species (predator) kills and eats another (prey).

Parasitism

One species lives on or in another, gaining nutrients at the host's expense without usually killing it.

Herbivory

An animal feeds on plants or algae.

Competition

Two organisms vie for the same limited resource; both are negatively affected.

Intraspecific Competition

Competition between members of the same species.

Interspecific Competition

Competition between members of different species.

Mutualism

Both species benefit from the interaction.

Obligate Mutualism

One or both partners cannot survive or reproduce without the other.

Facultative Mutualism

Both partners benefit but can survive independently.

Commensalism

One species benefits while the other is unaffected (e.g., egrets and cattle).

Facilitation

One species indirectly benefits another by altering the environment to make it more suitable.

Coevolution

Two species influence each other's evolution through reciprocal adaptations (e.g., aphids and Buchnera bacteria).

Keystone Species

A species that has a disproportionately large effect on its community relative to its abundance or biomass.

Ecosystem Engineer

A keystone species that physically alters the environment, creating new habitats for others.

Disturbance

A density-independent event (like fire or storm) that alters populations and community structure.

Succession

Predictable order of species colonization and replacement after a disturbance.

Biodiversity

Variety of life across all levels of biological organization—from genes to ecosystems.

Island Biogeography

Study of how island size and distance from mainland affect species colonization and extinction.

Species-Area Relationship

Larger islands support more species because they offer more resources and lower extinction risk.

Distance Effect on Islands

Islands closer to the mainland have higher colonization rates and thus greater species diversity.

Equilibrium Number of Species (on Islands)

Point where colonization rate equals extinction rate.

Facilitation Example

Trees shading forest floor, allowing shade-tolerant plants to thrive.

Huffaker Predator-Prey Experiment

Showed that predator-prey populations can persist longer when prey have refuges.

Species Interactions and Climate Change Example

Arctic warming allows red foxes to expand north and outcompete arctic foxes.

Resource Partitioning Example

Red-winged and yellow-headed blackbirds nesting in different marsh zones to reduce overlap.

Spanish Moss Example

Lives on trees without harming them—an example of commensalism.

Leaf Cutter Ant Example

Mutualism between ants, cultivated fungus, and antibiotic-producing bacteria that protect the fungus.

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