7.29 Community Ecology & Conservation Biology – Lecture Review

A comprehensive set of Q&A flashcards covering species interactions, competition, mimicry, succession, biodiversity metrics, and conservation concepts presented in the lecture.

What is mutualism?

A species interaction in which both participants benefit (+/+) from the relationship.

Define competition in ecological interactions.

An interaction where two organisms attempt to use the same limited resource, resulting in negative effects on both (–/–).

What does the Principle of Competitive Exclusion state?

No two species can occupy the exact same niche indefinitely; the better competitor will drive the other to local extinction or force it to shift niches.

Fundamental niche vs. realized niche

Fundamental niche is the full range of resources a species could use; realized niche is the portion actually occupied after competition.

Example experiment supporting competitive exclusion

Gause’s Paramecium study: P. aurelia out-competed P. caudatum when grown together, driving P. caudatum to extinction in the mixed culture.

What is resource partitioning?

Evolutionary division of resources that allows similar species to coexist by using different parts of a habitat (e.g., warblers feeding at different tree heights).

Intraspecific vs. interspecific competition

Intraspecific = competition within the same species; interspecific = competition between different species.

Exploitation vs. interference competition

Exploitation: organisms indirectly compete by consuming shared resources. Interference: organisms directly interact, inhibiting others' access to resources.

Define predation.

An interaction in which one organism (predator) kills and eats another (prey), benefiting the predator and harming the prey (+/–).

Top-down control model

Predators regulate the abundance of prey and consequently the lower trophic levels in an ecosystem.

Bottom-up control model

Nutrient supply and plant productivity regulate higher trophic levels in an ecosystem.

Müllerian mimicry

Two or more unpalatable or harmful species evolve similar warning colorations to reinforce avoidance by predators.

Batesian mimicry

A harmless or palatable species mimics the warning coloration of a harmful or unpalatable species to avoid predation.

Cryptic coloration

Camouflage that makes prey difficult to detect against its background.

Aposematic coloration

Warning coloration used by animals to signal toxicity or unpalatability to predators.

Panoramic vision vs. binocular vision in predator–prey

Prey often have eyes on the sides of the head (panoramic) for wide field detection; predators have forward-facing eyes (binocular) for depth perception and targeting.

Define parasitism.

A relationship where the parasite benefits (+) while the host is harmed (–).

Ectoparasite vs. endoparasite

Ectoparasite lives on the host’s surface (e.g., tick); endoparasite lives inside the host (e.g., tapeworm).

Altruism (ecology context)

Self-sacrificing behavior that benefits another organism, often observed in reproductive behaviors (e.g., male insects consumed after mating).

Describe the lynx–snowshoe hare cycle.

Populations of hare increase, then lynx increase; as lynx over-predate, hare decline, followed by a lynx decline—an example of coupled predator–prey oscillations.

Primary succession

Community development starting on a site that previously lacked living organisms (e.g., newly exposed glacial rock).

Secondary succession

Community recovery after a disturbance removes an existing community but leaves soil intact (e.g., post-hurricane forest regrowth).

Facilitation in succession

Early species modify the environment (e.g., add nitrogen, deepen soil) making it more suitable for later-successional species.

Climax community

A relatively stable, late-successional community that persists until disrupted.

Shannon–Weaver diversity index (H')

A metric combining species richness and evenness; higher H' indicates greater biodiversity.

Species richness

The number of different species present in a community.

Species evenness

How similar the abundances of different species are within a community.

Diversity-stability hypothesis

Ecosystems with higher species diversity show less year-to-year variation in biomass and are more resilient to disturbance.

Indicator species

Species sensitive to environmental changes whose presence, absence, or abundance reflects ecosystem health (e.g., mayfly larvae in streams).

Umbrella species

Species with large habitat requirements whose conservation confers protection to many co-occurring species (e.g., northern spotted owl).

Flagship species

Charismatic species used to rally public support for conservation (e.g., giant panda, mountain lion).

Keystone species

A species that has a disproportionate effect on community structure; its removal greatly reduces biodiversity (e.g., Pisaster sea star).

Foundation species

Species that create or define a habitat and have major influence through physical dominance (e.g., corals, kelp).

Invasive species

Non-native species that spread rapidly, out-compete natives, and alter ecosystems (e.g., kudzu, zebra mussels, Burmese pythons).

Endemic species

Species restricted to a specific geographic area and found nowhere else.

Biodiversity hotspot

A region with exceptional levels of endemic species and high habitat loss, prioritized for conservation.

Bioremediation

Using living organisms (plants, microbes) to detoxify polluted ecosystems.

Captive breeding

Breeding endangered species in controlled environments to increase population numbers for reintroduction (e.g., California condor, gray wolf).

Example of top-down regulation protecting vegetation

Sea otters control sea urchins; without otters, urchins overgraze kelp forests, reducing biodiversity.

Example of invasive plant in the southeastern U.S.

Kudzu, introduced for erosion control, now blankets and kills native vegetation.

Real-world example of Batesian mimicry in snakes

Non-venomous scarlet kingsnake mimics venomous coral snake ("red-touch-black, friend of Jack; red-touch-yellow, kill a fellow").

Why are plants not completely consumed by herbivores?

Predators, parasites, and diseases keep herbivore populations in check (top-down control), and some plants possess physical or chemical defenses.

Name a plant chemical defense that humans use medicinally.

Nicotine from tobacco—an alkaloid that deters insects and acts as a stimulant in humans.

What is an epiphyte?

A plant that grows on another plant for physical support but does not derive nutrients from it (e.g., Spanish moss).

Define habitat fragmentation.

Breaking continuous habitats into smaller, isolated patches, often reducing species diversity.

Purpose of the American chestnut restoration program

To reintroduce blight-resistant American chestnut trees and restore lost forest biodiversity.