BI230 Eco/Evo Unit 3: Species Interactions and Communities

Competition

The use or defense of a resource by one individual that limits the availability of that resource to other individuals.

Resource

A substance or factor that is consumed by an organism and that supports increased population growth as its availability in the environment increases.

Limiting resource

A resource that is in short supply and restricts the growth or population of a species, affecting its survival and reproduction.

Conditions

The environmental factors that influence the growth, survival, and reproduction of a species, ranging from abiotic factors like temperature and moisture to biotic factors such as the presence of other organisms.

Law of the Minimum

Populations will increase until the most limiting resource prevents further growth.

Intraspecific competition

Members of the same species compete (density-dependent).

Interspecific competition

Different species compete (giving the upper hand to the more efficient species).

Interference competition

“Hogging” competition where competitors defend resources.

Allelopathy

Interference where organisms use chemicals to harm competitors.

Exploitative competition

Competitors drive down the abundance of resources so others cannot live.

Apparent competition

2 species have negative effects through parasites, predators, or herbivores (Not competition).

Niche

The range of conditions and resource qualities within which an individual or species can survive and reproduce.

Fundamental niche

The total range of resources an organism can use under ideal conditions.

Realized niche

The resources an organism uses within the community.

Competitive Exclusion Principle

2 species cannot coexist indefinitely if limited by the same resource (2 species cannot occupy the same niche). 

Niche partitioning

Natural selection drives two competing species to begin using different niches or types of resources.

Coexistence

The result of niche partitioning.

Space, Time, Food

The three major resources that are partitioned.

Lotka-Volterra Model

The model that shows the relationship between species.

Competition coefficient

A parameter in ecological models that quantifies the effect of one species on another when they compete for the same limited resources (“the effect on species 1 on species 2”).

Stable coexistence

Two species can coexist at the intersection of two isoclines.

Unstable equilibrium

Two populations can coexist at the intersection of the two isoclines, but any deviation from this point will lead to one species winning over the other.

Predator

Consumes other organisms.

Herbivore

Type of predator that eats photosynthesizers.

Population cycle

The predictable, recurring increase and decrease in the size of a population over time.

Boom-bust cycles

Food resources fluctuate in predictable ways (seasonality, depleting food faster than it can regenerate, causing their own population to crash).

Coevolution

Each side shapes the other’s adaptations over time.

Symbiotic

An association between 2 or more species where at least one benefits from the relationship.

Mutualism

An association between 2 or more species where everyone benefits.

Facultative mutualism

Species involved can survive without each other.

Obligate mutualism

Tight relationship where one dies without the other.

Seed dispersal

Plants get offspring to a new location, and animal gets food.

Pollination

Plants get fertilized, animals get a snack (nectar).

Plant defense

A set of strategies plants use to protect themselves from herbivores and pathogens, which includes a range of physical barriers like thorns and a waxy cuticle, chemical compounds that can be toxic or bad-tasting, and even mutualistic relationships with other organisms.

Optimal Defense Hypothesis

Organisms allocate defenses to maximize individual fitness, and the defenses are costly.

Resource Availability Hypothesis

Account for plants ability to replace grazed tissues.

Pest removal

Species pair up where one will remove pests from the other.

Evolutionary arms race

A co-evolutionary process where two interacting species evolve escalating adaptations and counter-adaptations to each other, like a predator and prey becoming faster or a plant and insect developing more potent chemical defenses.

Red Queen Hypothesis

Sexual selection allows the evolution rate to offset the evolution of parasites, viruses, bacteria, predators, etc.

Parasite

An organism that lives on or in another organism, but rarely kills it.

Parasitoid

An organism that lives in one host, eventually killing the host as part of its development.

Pathogen/disease vectors

Microscopic parasites that cause disease, like abnormal conditions that negatively affect organs, not due to an external injury.

Hemiparasite

Photosynthesis but get water from host.

Holoparasite

Relies totally on the host plant.

Kleptoparasitism

Parasitism by theft.

Commensalism

A symbiotic relationship where one organism benefits while the other is neither harmed nor benefits (one harmed, one neutral).

Amensalism

A relationship where one organism is harmed and one organism is neither harmed nor benefits (one harmed, one neutral).

Community

Multiple species interacting directly or indirectly that are connected by time and space.

Clear-cut communities

One boundary separates two clear, distinct environments.

Gradual community transitions

The slow and steady process of change within a community over a long period, rather than an abrupt shift (includes zones).

Ecotone

The location where two communities meet.

Species evenness

Comparison of the relative abundance of species in a community.

Species richness

The number of species in a community.

Diversity Indices

Estimates of species diversity (Ex: Shannon Diversity Index)

Island biogeography

Studies the biodiversity of isolated natural communities.

Resistance

How much a community changes due to a particular disturbance.

Return time

How long it takes a community to return to a stable state after being disturbed.

Resilience

How close the post-recovery community resembles the pre-disturbance community.

Food web

A diagram showing an organism’s feeding relationships with other organisms in the same location.

Food chain

Zoom in on close feeding relationships in the food web.

Green Earth Hypothesis

The Earth is green because predators prevent herbivores from eating everything.

Bottom-up control

Increase or decrease in primary producers, leading to a sequence of similar (+ or - ) effects on the rest of the food chain.

Top-down control

The predator population (+ or - ) affects the lower tropic levels that can be supported.

Trophic cascade

Indirect interactions between community members control the whole ecosystem.

Succession

Change in the community through time initiated by a disturbance.

Primary succession

Development of communities in habitats devoid of plants and organic soil.

Secondary succession

Development of communities in habitats nearly devoid of plants but with organic soil.

Pioneer species

The first species to colonize.

Climax community

The final stage in succession.

Space for time substitution

Uses current spatial patterns to infer how something will change over time.

3+ special cases of succession

Scouring floods, lake succession, and dune succession

Keystone species

Species that disproportionally affect relative abundances.

Dominant species

Species that affect the community through their high abundance.

Ecosystem engineer

An organism that significantly modifies its environment, creating habitats for other species beyond its own lifetime.

Generic names for communities

Quaternary consumer (4th), Tertiary consumer (3rd), Secondary consumer (eats herbivores/primary producers), Primary producer (plants, algae, etc), Apex predator (top predator of the food chain).