AP Environmental Chapter 6


Terms in this set (...)

All the individuals that belong to the same species and live in a given area at a particular time, boundaries are hard to define
Levels of Complexity
Individual < Population < Community < Ecosystem < Biosphere
All of the populations of organisms within an area, boundaries hard to define
All the biotic and abiotic components of a region, contains communities
Incorporates all of the ecosystems, on a global scale
Population Size
Immigration + births - deaths - emmigration = ___________
- Also known as n
- The total number of individuals within a defined area at a specific time.
Population Ecology
The study of factors that cause populations to increase or decrease
Population Density
The number of individuals per unit of area (or volume of water) at a given time
Population Distribution
A description of how individuals are distributed with respect to one another
- Three Types:
--Random, like trees
--Uniform, like farms
--Clumped, like schooling fish
Sex Ratio
Ratio in a population between males and females, usually close to 50:50 in sexually reproducing populations
Age Structure
A description of how many individuals fit into a particular age category
- Large proportion of reproducing age -> rapidly growing population
Density-Dependent Factors
Factors that influence an individual's probability of survival and reproduction in a manner that depends on the population size
Limiting Resource
A resource that a population cannot live without and which occurs in quantities lower than a population would require to increase in size
Carrying Capacity
Limit of how many individuals the food supply can sustain (k)
Density-Independent Factors
Factors that have the same amount of effect on an individual's probability of survival and reproduction at any population size (like tornadoes, hurricanes and volcanoes)
Growth Rate
The number of offspring an individual can produce in a given time period minus the deaths of the individual or offspring in that same time period
Intrinsic Growth Rate
Maximum potential for growth specific to the population (r)
Exponential Growth Model
N(t): Population size after t time
No: N sub 0 or the current population
r: intrinsic growth rate
t: time
When population growth is very rapid and exponential it is modelled by a ____________
Logistic Growth Model
A population whose growth is originally exponential but then slows as it reaches the carrying capacity of the environment, looks like an s-curve
When food does not match population size and it is larger than the carrying capacity
A population crash, commonly after an overshoot
k-Selected Species
A species with a low intrinsic growth rate and the population size increases slowly to carrying capacity. Population fluctuations are small.
- Typically large organisms that are reproductively mature later and life
- Have few, large offsprings and the parents provide a substantial amount of care
r- Selected Species
A species with a high intrinsic growth rate that reproduces frequently with many offsprings.
- Typically have population shoot ups and die offs
- Usually small, reproductively mature quickly
Survivorship Curves
Distinct patterns of survival over time
Type 1: approach old age and then die of in large numbers (k- Selected species)
Type 2: Constantly decline over time
Type 3: Population starts high but many die off in their early life and few reach adulthood (r- Selected)
Strips of habitat that connect separate populations
A group of spatially distinct populations that are connected by occasional movements of individuals
Community Ecology
The study of interactions (competition, predation, mutualism and commensalism), which determine the survival of a species in a habitat
The struggle of individuals to obtain a limiting resource (bad for both sides)
Competitive Exclusion Principle
Two species competing for the same limiting resource cannot coexist
Resource Partitioning
Two species divide a resource based on differences in the species behavior or morphology
- When competition reduces the ability of a species to survive and reproduce, natural selection will favor individuals that overlap less with the other species in the resources they use

-- Temporal: Reducing competition by using the same resource but at different times
-- Spatial: Reducing competition by using different habitats
--Morphological: reducing competition by the evolution of different body shapes and sizes
The use of one species as a resource for another species
Four Types:
- True Predators: typically kill their prey and eat most of it (lions)
- Herbivores: consume plants as prey (deer)
- Parasites: live on or in the animal they consume (tapeworms), or pathogens (parasites that cause disease in the host)
- Parasitoids: organisms that lay eggs inside other organisms, larvae then consume the host inside out, eventual death of the host
Benefits two interacting species by increasing both species chances of survival and reproduction (plants and pollinators)
A relationship in which one species benefits but the other is neither harmed nor helped ( birds using trees as a perch)
Symbiotic Relationship
The relationship of two species that live in close association with each other
Keystone Species
Species that play much more important roles in communities that the relative abundance suggests
Predator- Mediated Competition
When a key predator prevents another species from taking over and allows for other species
Ecosystem Engineers
Keystone species that create or maintain habitat for others
Ecological Succession
The predictable replacement of one group of species by another over time
Primary Succession
Succession that occurs on surfaces originally without soil like abandoned parking lots or cooled lava
Bare rock > lichens and mosses > annual weeds > perennial weeds and grasses > shrubs > aspens, cherry and young pine forests > beech and maple broadleaf forest
Secondary Succession
Succession that occurs in areas that have been disturbed but have not lost their soil, like places after hurricanes, forest fires, abandoned farms etc.
Annual weeds > perennial weeds and grasses > shrubs > aspen, cherry and pine forests > beech and maple broadleaf forests
Pioneer Species
Species with the ability to colonize new areas rapidly and grow well in full sun.
Aquatic Succession
This term covers the kinds of the the following two types:
- Ocean: algae on rock > barnacles > barnacles and mussels
- Lakes: open water lake > accumulating sediments > filled in and terrestrial
Theory of Island Biogeography
Dual importance of habitat size and distance for richness.
- Large habitats: more species, less prone to extinction, wide range of habitats
- Closer, more species
As you get further from the equator, are there more or fewer species?

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