53 terms

# Chapter 6 - Friedland and Relyea

#### Terms in this set (...)

Population
Composed of all individuals that belong to the same species and live in a given area at a particular time
Community
Incorporates all of the populations of organisms within a given area
Population ecology
The study of factors that cause populations to increase or decrease
Population size
The total number of individuals within a defined area at a given time
Population density
The number of individuals per unit area (or volume for aquatic organisms) at a given time
Population distribution
A description of how individuals are distributed with respect to one another
Sex ratio
The ratio of males to females
age structure
a description of how many individuals fit into particular age categories
Limiting resource
A resource that a population cannot live without and which occurs in quantities lower than the population would require to increase in size
Density-dependent factors
Influences an individual's probability of survival and reproduction in a manner that depends on the size of the population
Carrying capacity; k
Population growth slowed as population size increased because there was a limit to how many individuals the food supply could sustain
Density-independent factors
Have the same effect on an individual's probability of survival and amount of reproduction at any population size
Population growth rate
The number of offspring an individual can produce in a given time period, minus the deaths of the individual or offspring during the same period
Population growth model
Mathematical equations that can be used to predict population size at any moment in time
Intrinsic growth rate; r
Under ideal conditions, with unlimited resources available, every population has a particular maximum potential for growth
Exponential growth model
Tells us that, under ideal conditions, the future size of the population depends on the current size of the population, the intrinsic rate of the population, and the amount of time over which the population grows
J-shaped curve
When populations are not limited by resources they exhibit a J shaped curve, an exponential growth model
Logistic growth model
Describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment
S-shaped curve
The shape of the logistic growth model when graphed
Overshoot
When the population becomes larger than the spring carrying capacity
Die-off
Population crash usually experienced after the overshoot of the carrying capacity
k-selected species
Species that have a low intrinsic growth rate, which causes their populations to increase slowly until they reach the carrying capacity of the environment
r-selected species
Species that have a high intrinsic growth rate because they reproduce often and produce large numbers of offspring
Survivorship curves
Graphs of distinct patterns of survival over time
Type I Survivorship Curve
Shows a population where most individuals live to an advanced age
Type II Survivorship Curve
Shows a population where all ages have a similar death rate
Type III Survivorship Curve
Most individuals die early in life (e.g., fishes, invertebrates, and plants).
Corridors
Strips of habitat that connect separated populations that the animal travels across
Metapopulations
A group of spatially distinct populations that are connected by occasional movements of individuals between them
Inbreeding depression
Related individuals breed to produce an offspring that have trouble surviving and reproducing
Community ecology
The study of species interactions, which determine the survival of a species in a habitat
Symbiotic relationship
The relationship between two species that live in close association with each other.
Competition
The struggle of individuals to obtain a limiting resource
Competitive exclusion principle
States that two species competing for the same limiting resource cannot coexist
Resource partitioning
Where two species divide a resource based on differences in the species' behavior or morphology
Predation
Refers to the use of one species as a resource by another species
Parasitism
A relation between organisms in which one lives as a parasite on another
Pathogen
A microorganism that is capable of causing disease in a susceptible host
Herbivory
Interaction in which one animal (the herbivore) feeds on producers (such as plants)
True predators
Typically kill their prey and consume most of what they kill
Mutualism
Benefits two interacting species by increasing both species' chances of survival or reproduction
Herbivores
Consumes plants as prey
Commensalism
A type of relationship in which one species benefits but the other is neither harmed nor helped
Keystone species
A species that plays a role in its community
Ecosystem engineers
Species that create or maintain habitat for other species
Ecological succession
The predictable replacement of one group of species by another group of species over time
Primary succession
Occurs on surfaces that are initially devoid of soil
Secondary succession
Occurs in areas that have been disturbed but have not lost their soil
Parasites
Live on or in the organisms they consume
Parasitoids
Organisms that lay eggs inside other organisms
Predator-mediated competition
Competition in which a predator is instrumental in reducing the abundance of a superior competitor, allowing inferior competitors to persist
Pioneer species
Organisms that have the ability to colonize new areas rapidly and grow well in full sunshine
Theory of island biogeography
Demonstrates the dual importance of habitat size and distance in determining species richness