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52 terms

Chapter 36 Population Ecology

STUDY
PLAY
The introduction of brown tree snakes to Guam results in more than a dozen species going extinct.
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Brown Tree Serpent
BTS would DEVASTATE Hawaiian Ecosystems
Ecology
The study of relationships among organisms and the environment
Population
Group of interbreeding organisms of one species in one location
Community
All of the populations in a given area
Ecosystem
Community plus nonliving environment
Density and Distribution Patterns Are Static Measures of a Population
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Habitat
Physical location where population members live
Population density
Number of individuals of a species per unit area or unit volume
Population Distribution
Describes how individuals are scattered in the habitat
Isolated Subpopulations May Evolve Into New Species
Overall area occupied by a population is not fixed
Range expansion for invasive species
Brown tree snakes, fire ants, zebra mussels, gypsy moths, European starling, and kudzu
Natural selection may shape a genetically distinct subpopulation
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The distribution of humans across the United States is a ___ distribution.
Clumped
Population dynamics
Study of factors that influence changes in population size
Immigration
to come to a country of which one is not a native, usually permanent residence.
emigration
to leave one country or region to settle in another.
Births Add Individuals to a Population
Survivorship Curves Show the Probability of Dying at a Given Age
Birth rate
Number of new individuals produced per individual in a defined time period
Age structure
Distribution of age classes.
Determines whether a population is growing, stable, or declining.
Death rate
Number of deaths per unit time
Scaled by the population size
Species vary tremendously in their patterns of survivorship
Yellow-eyed penguins
3 survivorship patterns-Type I
mortality rate is highest as individuals approach the maximum life span
Type II
equal probability of dying at any age
Type III
mortality rate highest in young
Yellow-eyed penguins have feature of both type I and type II
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Per capita rate of increase, r, is the difference between the birth rate and the death rate
Positive r = growing population
Negative r = population shrinking
Growth Is Exponential When Resources Are Unlimited
G = rN
G = number of individuals added
r = per capita growth rate
N = initial size of population
Exponential growth
J-shaped curve
Exponential growth
Growth pattern in which the individuals in a population reproduce at a constant rate
J-shaped curve
Curve with a shape similar to that of the letter J; can represent prolonged exponential growth.
Population Growth Eventually Slows
Combination of external factors that keep a population from reaching its maximum growth rate. Competition, predation, etc.
Every habitat has a carrying capacity
Maximum number of individuals that the habitat can support indefinitely
Logistic growth model
Early growth of a population may be exponential, but growth slows as the population approaches the habitat's carrying capacity
S-shaped curve
Leveling off of an exponential, J-shaped curve when a rapidly growing population exceeds the carrying capacity of its environment and ceases to grow.
Carrying capacity may or may not be fixed
Rose disease limited by supply of hosts.
Environmental conditions can change.
Some species do not fit neatly into either the exponential or logistic models
Collared lemmings
4-year cycle
Density-dependent conditions
Effects increase as a population grows
Biotic (living)
Density-independent conditions
Effects unrelated to populations size
Abiotic (nonliving)
Life history
Includes all events of an organism's life from conception through death.
Main focus is adaptations that influence reproductive success.
Organisms Balance Reproduction Against Other Requirements
Life history reflects a series of evolutionary trade-offs.
Solutions vary tremendously
Reproduction is extremely costly, Timing also critical
r-selected species
Individuals short-lived
Reproduce at early age
Have many offspring that receive little care
Population's growth rate can be very high
Type III survivorship curve
K-selected species
Individuals long-lived
Late-maturing
Produce few offspring that receive extended parental care
Type I or II survivorship curves
Guppies Illustrate the Importance of Natural Selection
Live in rivers and streams on the South American mainland and on the islands of Trinidad and Tobago.
Face different levels of predation.
Predicted predation would effect life history.
Population Dynamics Reflect the Demographic Transition
By early 2010, the world's human population was approaching 6.8 billion
Average population density of 45 people per square kilometer
Distribution not random
China and India account for 1/3 of all humans
Less-developed countries are growing at much faster rates than are more-developed countries
Each country's economic development influences progress along demographic transition
Birth and death rates shift from high to low
Population's age structure helps predict its future birth rate
India - high potential for growth
United States - stable population
China - population declining
Life expectancy has increased throughout history
Today 75 in most-developed countries.
50 in least-developed countries
Substantial differences in mortality rates
The Ecological Footprint Is an Estimate of Resource Use
Measures the amount of land area needed to support a country's overall lifestyle.
World's wealthiest and most populous countries have the largest ecological footprints.
Energy consumption accounts for about half of the ecological footprint.
Firefly Photinus ignitus
Use flashes to deliver precise mating information between sexes
Spermatophore
Sperm and amino acids for developing young.
Females should choose males with largest ones.
Males flash duration reliably coded the weight of the spermatophore
Created artificial males to test duration of flashes found attractive by females.
Females preferred long flashes up to a limit
Very long flashes resemble predatory fireflies