ISC EXAM 2 - BIO

Ecology

The quantitative study of the interactions among organisms and the interactions of organisms with their environment

Competition

Interaction in which species or individuals use the same limited resources

Intraspecific competition

Competition between individuals of the same species; high resource overlap and strong competition; drives natural selection and helps regulate population size

Interspecific competition

Competition between individuals of different species; lower resource overlap and weaker competition; can lead to competitive exclusion or resource partitioning

Competitive exclusion

One species drives away or eliminates an inferior competitor

Resource partitioning

Species evolve to use different resources so they can coexist

Niche

A species’ role defined by its habitat and its interactions

Competitive release

Expansion of a species’ realized niche in the absence of competitors

Niche partitioning

Coexistence of two or more species in the same niche space

Character displacement

Similar species living in the same area develop morphological or behavioral differences to reduce competition

Keystone species

A species with a disproportionate impact on the ecosystem relative to its abundance or biomass

Lotka

Volterra model

Logistic equation

Describes population growth limited by carrying capacity

dN/dt

Rate of population change

r

Maximum population growth rate

N

Population size

K

Carrying capacity (maximum population size the environment can support)

α (alpha)

Per capita effect of species 2 on species 1; a conversion factor (1 individual of sp. 2 = α individuals of sp. 1)

β (beta)

Per capita effect of species 1 on species 2; a conversion factor (1 individual of sp. 1 = β individuals of sp. 2)

Isocline

A line on the graph where a species’ population growth is zero (dN/dt = 0)

Stable equilibrium (competition)

The point where the two species’ isoclines cross, predicting coexistence

Lotka-Volterra

predator prey model

Predation

Individuals of one species kill and consume individuals of another species

Carnivory

Predator and prey are both animals

Herbivory

Predator is an animal; prey are plants or algae

Top-down

predators and consumers regulate the population size, structure, and behavior of lower trophic levels in a food web

Spatial refuge

A place where predators cannot hunt effectively

Parasitism

Relationship in which one species benefits at the expense of another; parasites consume the tissue or body fluids of the host, usually harming but not immediately killing it

Parasite

Organism that lives on or in a host and consumes parts of it without usually killing it

Pathogen

A parasite that causes disease

Host

The organism a parasite lives on or in

Vector

A parasite or carrier that transmits pathogens (e.g., mosquitoes transmitting parasites and viruses to humans)

Zoonosis

Infectious disease caused by a pathogen that has jumped from a non human

Coevolution

Evolution of one species depends in part on the evolution of another species

Evolutionary arms race

Reciprocal selection between parasites and hosts (or predators and prey)

Red Queen hypothesis

Species must constantly adapt and evolve just to maintain their relative fitness against ever

Commensalism

One organism benefits while the other is neither helped nor harmed (+/0)

Mutualism

Both species benefit

Facultative mutualism

Optional, more casual mutualistic relationship

Obligate mutualism

Coevolution has made one or both species dependent on the other; they can’t exist in isolation

Symbiosis

a close, long-term interaction between two different species living together

Biological community

A group of interacting species inhabiting a given area or volume

Species richness (S)

The number of species present (per area or volume); weighs abundant and rare species the same

Species diversity (H’, D)

Accounts for both the number of species and their relative abundances; weights diversity by abundance

Species composition

The actual species present in a community (the species list)

Relative abundance (nᵢ/N)

Proportion of individuals of a given species (nᵢ) out of the total number of individuals of all species in the community (N)

Species evenness

How evenly individuals are distributed among the species in a given area

Effective diversity

Depends on both richness and abundance

Collector’s curve

Graph of cumulative number of species S(n) vs. cumulative number of samples (n); a saturation function that shows whether enough samples have been collected to find most species in an area

Rank abundance curve

Plot of relative abundance vs. species rank from most to least common

N

Total number of individuals in the population or sample

ni

Number of individuals of species i

pᵢ

Relative abundance of species i (nᵢ / N)

Simpson’s diversity index

Chance that two individuals sampled from a community are the same species, calculated as Σ[nᵢ(nᵢ − 1)] / [N(N − 1)]; not sensitive to rare species; doesn’t assume all species were sampled; sensitive to dominance; the index decreases as diversity increases

Shannon diversity index

Calculated as −Σ[pᵢ × ln(pᵢ)]; sensitive to rare species; assumes all species are sampled and sample sizes are large; the index increases as diversity increases

Alpha (α) diversity

Local, within

Gamma (γ) diversity

Regional diversity; usually indicates the species source pool

Beta (β) diversity

Difference in species composition between local and regional diversity; calculated as γ / α to quantify variation in species composition

Drivers of biodiversity patterns

Species interactions (competition, predation, facilitation); environmental conditions (climate, soils, pH, nutrients); geographic and spatial factors (dispersal, biogeography, metacommunity dynamics)

Ecological succession

Gradual, directional change in community structure through time (e.g., old field to forest); replacement of one group of species by another

Climax community

A stable community that succession often progresses toward

Stochastic

Randomly determined; having a random probability pattern that can be analyzed statistically but not predicted precisely

Non-equilibrium models

living systems and ecosystems do not settle into a static, balanced state

Disturbance

Common event that changes community struct