Ecology Exam 3

Introduced, exotic, nonnative species

Species that are introduced to a region of the world where they have not historically existed.

Naturalized

When introduced species become a part of the native community

Invasive species

Introduced species that spread rapidly and negatively affect other species

Mesopredators

Relatively small carnivores that consume herbivores (coyotes, weasels, feral cats)

Top predators

Predators that typically consume both herbivores and predators (mountain lions, wolves, sharks)

How have humans impacted the range expansion of mesopredators?

We have reduced top predators, which has allowed for more mesopredators to expand their ranges

Two species will coexist if

Intra-specific competition is stronger than inter-specific competition

Lotka-Volterra equation

Functional response

The relationship between the density of prey and an individual predator’s rate of food consumption

Type I functional response

As prey density increases, predators consume a constant proportion of prey until satiated

Type II functional response

Any increase in prey density is associated with a slowing rate of prey consumption. Often due to prey handling times

Type III functional response

Predator exhibits varying prey consumption depending on prey densities, often associated with prey refuges, search image, and prey switching

Active hunting strategy

Predators spend most of their time moving looking around for prey

Ambush (sit-and-wait) strategy

Predators lie in wait for a prey to pass by

Behavioral defenses of predation:

• Alarm calling

• Spatial avoidance

• Reduction of activity

Crypsis

Camouflage that either allows an individual to match its environment or breaks up the outline of an individual (katydids)

Structural defenses

Reduce a predator’s ability to capture, attack, or handle prey (porcupine)

Chemical defenses

Using chemicals to produce a corrosive liquid or bad smell (bombardier beetle or skunk)

Warning coloration

Aposematism (away from danger)

Batesian mimicry

When palatable species evolve warning coloration that resembles unpalatable species

Müllerian mimicry

When several unpalatable species evolve a similar pattern of warning coloration

Behavioral defenses are often costly because the result in

Reduced feeding activity

Mechanical defenses are often

Energetically expensive to produce

Defense costs can reduce

Growth, development, and reproduction

Coevolution

When two or more species affect each other’s evolution; selection for prey defenses should favor the selection for counter-adaptation in predators

What is a model?

An abstraction of reality

What is the competitive exclusion principle?

Two species with identical niches cannot coexist indefinitely

Natural selection

A change in the frequency of genes in a population through differential survival and reproduction of individuals that possess certain phenotypes

Niche differentiation

When different species use different parts of the environment

Environmental diseases

Toxins, cancers, environmental shortages

Infectious diseases

Directly transmissible, two population systems

Zoonoses

The pathogen primarily resides in a second species (reservoir) and is transmitted to humans without an intermediary species (rabies, schistosomiasis)

Vector-borne/zoonoses

Infectious agents transmitted to organisms of one species through action of another species

Prion

An abnormal, transmissible agent that can induce folding of normal cellular prion proteins in the brain (rapidly progressive and always lethal)

Deemography

The study of populations

Growth rate

In a population, the number of new individuals that are produced per unit of time minus the number of individuals that die

Intrinsic growth rate r

The highest possible per capita growth rate for a population

Exponential growth model

A model of growth in which the population increases continuously at an exponential rate

J-shaped curve

The shape of exponential growth when graphed

Geometric growth model

A model of population that compares population sizes at regular time intervals

Doubling time

The time required for the population to double in size

Density independent limitations

Factors that limit population size regardless of the population’s density

Density dependent

Factors that affect population size in relation to the population’s density

Negative density dependence

When the rate of population growth decreases as population density increases

Self-thinning curve

A graphical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population, often has a slope of -3/2

Positive density dependence

When the rate of population growth increases as population density increases

Carrying capacity (K)

The maximum population size that can be supported by the environment

Logistic growth model

A growth model that describes slowing growth of populations at high densities

S-shaped curve

The shape of the curve when a population is graphed over time using the logistic growth model

Inflection point

The point on a sigmoidal growth curve at which the population has its highest growth rate, the largest derivative, or steepest slope

Life tables

Tables that contain class specific survival and fecundity data

Cohort life table

A life table that follows a group of individuals born at the same time from birth to the death of the last individual

Static life table

A life table that quantifies the survival and fecundity of all individuals in a population during a single time interval

Stable age distribution

When the age structure of a population does not change over time; occurs when survival and fecundity of each age class stays constant over time

Survivorship

The probability of surviving from birth to any later age class (lx)

Net reproductive rate (R0)

The total number of female offspring that we expect an average female to produce over the course of her life

Generation time T

The average time between the birth of an individual and the birth of its offspring

Overshoot

When a population grows beyond its carrying capacity; often occurs when the carrying capacity of a habitat decreases from one year to next

Die-off

A substantial decline in density that typically goes well below the carrying capacity

Deterministic model

A model that is designed to predict a result without accounting for random variation in population growth rate

Stochastic model

A model that incorporates random variation in birth and death rates due to random chance

Demographic stochasticity

Variation in birth rates and death rates due to random differences among individuals

Environmental stochasticity

Variation in birth rates and death rates due to random changes in the environmental conditions

Liebig’s law of the minimum

Law stating that a population increases until the supply of the most limiting resource prevents it from increaseing further

Competitive exclusion principle

Two species cannot coexist indefinitely when they are both limited by the same resource

Competition coefficients

Variables that convert between the number of individuals of one species and the number of individuals of the other species

Zero population growth isocline

Population sizes at which a population experiences zero

Ecotone

A boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a sharp change in species

Rank abundance curves

A curve that plots the relative abundance of each species in a community in rank order from the most abundant species to the least abundant species

Species evenness

A comparison of the relative abundance of each species in a community

Trophic pyramid

A chart composed of stacked rectangles representing the amount of energy or biomass in each trophic group

Ecological stoichiometry

The study of the balance of nutrients in ecological interactions, such as between an herbivore and a plant