Module 10 - Predation

Predation

An interaction where one organism benefits and the other is harmed. This includes carnivory

True predators

Predators that consume many prey items throughout their lives and usually kill their prey.

Grazers

Herbivores that consume parts of many prey items but usually do not kill them.

Parasites

Organisms that consume parts of one or a few hosts and usually do not kill the host immediately.

Parasitoids

Organisms that live in or on a host and eventually kill the host.

Active predators

Predators that search throughout their habitat for prey.

Sit-and-wait predators

Predators that remain in one place and attack prey that come close.

Polyphagous

Generalists that feed on many prey species. Most true predators are polyphagous.

Oligophagous

Specialists that feed on only a few plant species. Most herbivores are oligophagous.

Predator-prey cycle

A pattern where predator and prey populations rise and fall over time

Physical defenses

Prey defenses such as large size

Chemical defenses

Prey defenses involving toxins or bad-tasting chemicals.

Aposematism

Warning coloration that advertises toxicity or danger to predators.

Crypsis

Camouflage that helps prey blend into the environment.

Mimicry

When one species resembles another species for protection.

Functional response

The relationship between prey density and the rate at which predators consume prey.

Numerical response

A change in predator population size in response to prey abundance.

Masting

A plant defense strategy where plants produce very large numbers of seeds in some years and very few in others to overwhelm herbivores or reduce their populations.

Compensation

A plant response to herbivory where new tissue is produced to replace tissue that was eaten.

Lotka-Volterra Predator-Prey Model

A mathematical model that describes cyclical fluctuations in predator and prey populations based on interaction rates.

Parasitism

A close interaction where the parasite benefits and the host is harmed

Parasite

An organism that lives in close association with a host and depends on it for nutrition

Host

The organism that provides resources to a parasite.

Pathogen

A parasite that causes disease.

Microparasite

A small parasite such as bacteria

Macroparasite

A larger parasite such as worms

Endoparasite

A parasite that lives inside the host.

Ectoparasite

A parasite that lives on the outside surface of the host.

Obligate parasite

A parasite that cannot survive without its host.

Facultative parasite

A parasite that can survive even if the host dies.

Definitive host

The host where sexual reproduction of the parasite occurs.

Intermediate host

The host where asexual reproduction or development occurs.

Vector

An organism that transmits a parasite from one host to another.

Virulence

The degree of harm a parasite causes to its host.

Coevolution

Reciprocal evolutionary change between host and parasite

Symbiosis

A close and long-term biological interaction where one species lives on or in another and both are physiologically connected.

Plasmodium

A protozoan parasite that causes malaria.

Malaria life cycle

Mosquito injects Plasmodium into humans

Brood parasitism

An interaction where one species lays its eggs in the nest of another species

Threshold density

The minimum density of susceptible individuals required for a disease to spread within a population.

Competition

A negative interaction where both species are harmed because they use the same limited resource.

Intraspecific competition

Competition between individuals of the same species.

Interspecific competition

Competition between individuals of different species.

Exploitation competition

Indirect competition where one species uses resources and reduces availability for another species.

Interference competition

Direct competition where species physically fight

Allelopathy

A form of interference competition where plants release chemicals that harm competing plants.

Competitive exclusion principle

Two species cannot coexist if they use the exact same resources in the exact same way.

Asymmetrical competition

Competition where one species is much more negatively affected than the other.

Ecological niche

The role of a species in its environment

Fundamental niche

The full range of conditions and resources a species could use without competition.

Realized niche

The actual range of conditions and resources a species uses because competition limits it.

Resource partitioning

When similar species coexist by using resources in different ways.

Character displacement

Evolutionary change where competing species become more different over time to reduce competition.

Gause’s experiment

A lab experiment with Paramecium showing that species with identical niches cannot coexist.

Barnacle experiment

A field experiment showing that competition affects species distribution.

Lotka-Volterra competition model

A model showing how interspecific competition affects population growth.

Guild

A group of species that use the same type of resources in a similar way

Amensalism

An interaction where one species is harmed and the other is unaffected.

Mutualism

An interaction where both species benefit.

Commensalism

An interaction where one species benefits and the other is unaffected.

Positive interaction

An interaction where no species is harmed and at least one species benefits.

Trophic mutualism

A mutualism where organisms exchange food

Habitat mutualism

A mutualism where one organism provides shelter or habitat.

Service mutualism

A mutualism where one organism provides a service such as pollination

Symbiotic mutualism

A close physical association between species where both benefit.

Non-symbiotic mutualism

A beneficial interaction where species do not live in close physical association.

Mycorrhizae

A mutualism between fungi and plant roots. Fungi provide inorganic nutrients

Nitrogen-fixing bacteria

Bacteria that convert nitrogen into usable forms for plants while receiving sugars and shelter from the plant.

Gut microbiota

Bacteria or protozoans in animal guts that help digest food while receiving nutrients and shelter.

Lichens

A mutualism between fungi and algae or cyanobacteria. Algae provide sugars

Coral and zooxanthellae

A mutualism where algae provide sugars to coral

Pollination

A mutualism where animals receive nectar and plants receive pollen transfer.

Seed dispersal

A mutualism where animals eat fruit and disperse seeds.

Facultative mutualism

A mutualism where both species benefit but can survive without each other.

Obligate mutualism

A mutualism where one or both species cannot survive without the interaction.

Ecosystem engineers

Species that modify the environment in ways that create or maintain habitats for other species.

Community

A group of interacting species that occur together in the same place and time.

Biodiversity

The number of species in a community and the relative abundance of each species.

Richness

The number of species in a community.

Evenness

How evenly individuals are distributed among species.

Species accumulation curve

A graph that shows the number of species observed as sampling effort increases.

Asymptote

The point where a species accumulation curve levels off

Species-area relationship

The relationship showing that larger areas usually contain more species.

Rank abundance curve

A graph showing species abundance ranked from most abundant to least abundant.

Broken stick model

A rank abundance pattern with high richness and high evenness

Lognormal distribution

A rank abundance pattern with high richness but lower evenness

Geometric series

A rank abundance pattern with low richness and low evenness

Latitude gradient

The pattern that biodiversity is highest near the equator and decreases toward the poles.

Habitat heterogeneity

The idea that more complex habitats support more species.

Intermediate disturbance hypothesis

The idea that moderate disturbance can produce the highest diversity.

Island biogeography

Theory explaining species richness on islands based on immigration and extinction.

Immigration rate

The rate at which new species arrive on an island.

Extinction rate

The rate at which species disappear from an island.

Island size effect

Larger islands usually have more species because they have more habitat and lower extinction rates.

Island distance effect

Islands closer to the mainland usually have more species because immigration is easier.

Functional group

A set of species that perform similar roles or functions within an ecosystem.

Lottery models

Models that explain species coexistence based on chance events

DIVERSITY INDEX TERMS AND FORMULAS

Proportional abundance

The proportion of individuals belonging to a species. Formula: pᵢ = nᵢ / N.