Populations Key Concepts Factors affecting population size Species reproductive patterns Species survivorship patterns Conservation biology and human impacts on ecosystems
Dec 25, 2015
Populations Key ConceptsPopulations Key Concepts
Factors affecting population size Factors affecting population size
Species reproductive patterns Species reproductive patterns
Species survivorship patterns Species survivorship patterns
Conservation biology and human impacts on ecosystems
Conservation biology and human impacts on ecosystems
Population Dynamics and Carrying CapacityPopulation Dynamics and Carrying Capacity
Population dynamics Population dynamics
Biotic potential (intrinsic rate of increase [r]) Biotic potential (intrinsic rate of increase [r])
Environmental resistance Environmental resistance
Carrying capacity Carrying capacity
Exponential and Logistic Growth Exponential and Logistic Growth
Population Density Population Density
The biotic potential rmax is the population's capacity for growth.The intrinsic rate of increase (r) is the rate of population growth with unlimited resources.
No population can grow indefinitely due to limited resources such as light, water, and nutrients andalso due to competitors and/or predators.
Population DynamicsPopulation Dynamics
Populations change in size, density, dispersion and age structure.
Population density —the number of individuals of a population that inhabit a certain unit of land or water area.
Population dispersion —refers to how individuals of a population are spaced within a region.
Age structure of a population is usually described as the pre-reproductive stage, the reproductive stage and the post-reproductive stage. A population with a large reproductive stage is likely to increase, while a population with a large post-reproductive stage is likely to decrease.
Population dispersionPopulation dispersion
uniform dispersion a type of population dispersion in which the members of the population are uniformly spaced throughout their geographic region.
random dispersion —a type of population dispersion in which the position of each individual is not determined or influenced by the other members of the population.
clumping dispersion the most common dispersion pattern for populations. In this type of dispersion, individuals "flock together.“
Population DynamicsPopulation Dynamics
Four variables influence/govern population size: (1) births, (2) deaths, (3) immigration, and (4) emigration.
1) Increase in population occurs by birth and immigration.
2) Decrease in population occurs by death and emigration.
Factors Affecting Population SizeFactors Affecting Population Size
Fig. 9-3 p. 166
Biotic Potential v. Environmental Resistance
Po
pu
lati
on
siz
e (N
)
Time (t)Figure 9-4Page 166Figure 9-4Page 166
Carrying capacity (K)
Environmentalresistance
Bioticpotential
Exponentialgrowth
Carrying capacity (K) is determined by biotic potential and environmental resistance.
This is the number of a species' individuals that can be sustained indefinitely in a specific space.
Four variables influence/govern population size: (1) births, (2) deaths, (3) immigration, and (4) emigration.
Increase in population occurs by birth and immigration.
Decrease in population occurs by death and emigration.
Biotic Potential v. Environmental Resistance (Logistic Population Growth)
Density and Limiting FactorsDensity and Limiting Factors The density of a population may or may not affect how rapidly it can
grow.
1. Density-independent population controls affect a population's size regardless of its density. These are abiotic factors in the community.
2. Density-dependent factors or population controls have a greater affect on the population as its density increases. Infectious disease is an example of density-dependent population control.
The Role of Predation in Controlling Population SizeThe Role of Predation in Controlling Population Size
Predator-prey cycles (Boom and Bust) Predator-prey cycles (Boom and Bust) Top-down control Top-down control
Bottom-up control Bottom-up control
Fig. 9-8 p. 168
Reproductive Patterns and SurvivalReproductive Patterns and Survival
Asexual reproduction Asexual reproduction Sexual reproduction Sexual reproduction
r-selected species r-selected species K-selected species K-selected species
Fig. 9-10 p. 170
Reproductive Patterns and SurvivalReproductive Patterns and Survival
Reproductive patterns can be classified into two fundamental reproductive patterns: r-selected and K-selected species.
r-Selected species are opportunists and reproduce when conditions are favorable or when disturbance opens a niche for invasion. Most species of this type go through irregular and unstable boom-and-bust cycles in population size.
K-selected species generally follow a logistic growth curve. Many of the larger species with long generation times and a low reproductive rate are prone to extinction.
Availability of a suitable habitat for individuals of a population ultimately determines the population size.
A survivorship curve is one way to represent age structure of a population.
Three generalized types of survivorship curves are: (1) late loss, (2) early loss, and (3) constant loss.
A life table shows the numbers of individuals at each age on a survivorship curve. Insurance companies use life tables to determine the cost of
insurance policies.
Populations of different species vary in how long individual members typically live.
Effects of Genetic Variations on Population SizeEffects of Genetic Variations on Population Size
Variations in genetic diversity can affect the survival of small, isolated populations.
Several factors can play a role in loss of genetic diversity and survival of a small population.
Founder effect is when a few individuals move to a new location that is isolated from the original population. There is limited genetic diversity in such a population.
Demographic bottleneck occurs when only a few individuals survive a catastrophe.
Genetic drift is a third factor and involves random changes in gene frequencies in a population. This may help or hurt the survival of the population.
Inbreeding occurs when members of a small population mate one another; this may increase the numbers of defective genes in a population.
Human Impacts on EcosystemsHuman Impacts on Ecosystems
Habitat degradation and fragmentation Habitat degradation and fragmentation
Ecosystem simplification Ecosystem simplification
Genetic resistance Genetic resistance
Predator elimination Predator elimination
Introduction of non-native species Introduction of non-native species
Overharvesting renewable resources Overharvesting renewable resources
Interference with ecological systems Interference with ecological systems
Human Populations Key ConceptsHuman Populations Key Concepts
Factors affecting human population size Factors affecting human population size
Managing population growth Managing population growth
Human population problems Human population problems
Factors Affecting Human Population SizeFactors Affecting Human Population Size
Population change equationPopulation change equation
Crude birth rate (BR) The crude birth rate is the number of live births per 1,000 people in a population in a specific year.|
Crude birth rate (BR) The crude birth rate is the number of live births per 1,000 people in a population in a specific year.|
Crude death rate (DR) The crude death rate is the number of deaths per 1,000 people in a population in a specific year
Crude death rate (DR) The crude death rate is the number of deaths per 1,000 people in a population in a specific year
PopulationChange
PopulationChange == (Births + Immigration) – (Deaths + Emigration)(Births + Immigration) – (Deaths + Emigration)
Demography is the study of the size, composition, and distribution of human populations and the causes and consequences of changes in these characteristics.
Describing Population ChangesDescribing Population Changes
Doubling Times “Rule of 70”: Doubling time is one measure of population growth.
Fertility-is the number of births that occur to an individual woman in a population.
Replacement-level Fertility —the number of children a couple must have in order to replace themselves in a population.
Total Fertility Rate (TFR) —the number of children a woman will bear during her lifetime; this information is based on an analysis of data from preceding years in the population in question.
Factors Affecting Human Population SizeFactors Affecting Human Population Size
There are currently more births than deaths throughout the world.
1. The annual rate of natural population change (%) equals birth rate minus death rate divided by
1,000 persons multiplied by 100.
2. The rate of the world's population growth has decreased.
3. The annual population growth dropped by almost half between 1963 and 2004, from 2.2% to
1.2%. But during this same period, the population base doubled from 3.2 to 6.4 billion.
Factors Affecting Human Population SizeFactors Affecting Human Population Size
There is a big difference in the exponential population growth rates of developed and developing countries, with developed countries growing at 0.25% and developing countries growing at 1.46%— almost six times faster.
The six fastest growing countries in terms of population are: India, China, Pakistan, Nigeria,Bangladesh, and Indonesia.
The populations of China and India comprise 38% of the world's population. The next most populated country is the United Stated with 4.6% of the world's population.
Factors Affecting Birth Rates and Total Fertility RatesFactors Affecting Birth Rates and Total Fertility Rates
Children in Labor Force Cost of raising and educating children Availability of pension systems Urbanization Education and employment for women Infant mortality rate Average marrying age Abortion Availability of birth control
Children in Labor Force Cost of raising and educating children Availability of pension systems Urbanization Education and employment for women Infant mortality rate Average marrying age Abortion Availability of birth control
Factors Affecting Birth Rates and Total Fertility RatesFactors Affecting Birth Rates and Total Fertility Rates
Many factors influence birth and fertility rates.1. More children work in developing countries; they are important to the
labor force.2. The economic cost of raising and educating children determines their
numbers. the more children cost, the less children people tend to have.3. If there are available private/public pension systems, adults have fewer
children because they don't need children to take care of them in old age.
4. People in urban areas usually have better access to family planning, so they have fewer children.
5. If women have educational and economic choices, they tend to have fewer children.
6. When the infant mortality rate is low, people have fewer children because children are not being lost to death.
7. The older the age at which women marry, the fewer children they bear.8. If abortions are available and legal, women have fewer children.9. The availability of reliable birth control allows women to space children
and determine the number of children they bear.
Ages 0-14Ages 0-14 Ages 15-44Ages 15-44 Ages 45-85+Ages 45-85+
Rapid GrowthGuatemala
NigeriaSaudi Arabia
Rapid GrowthGuatemala
NigeriaSaudi Arabia
Slow GrowthUnited States
AustraliaCanada
Slow GrowthUnited States
AustraliaCanada
MaleMale FemaleFemale
Zero GrowthSpainAustriaGreece
Zero GrowthSpainAustriaGreece
Negative GrowthGermanyBulgariaSweden
Negative GrowthGermanyBulgariaSweden
Population Age StructurePopulation Age Structure
Fig. 10-14 p. 184Fig. 10-14 p. 184
The Demographic TransitionThe Demographic Transition
LowLow
HighHigh
Rel
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Rel
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Bir
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7070
6060
5050
4040
3030
2020
1010
00
Stage 1Preindustrial
Stage 1Preindustrial
Stage 2Transindustrial
Stage 2Transindustrial
Stage 3IndustrialStage 3
IndustrialStage 4
PostindustrialStage 4
Postindustrial
Lowgrowth rate
Lowgrowth rate
Increasing Growthgrowth rate
Increasing Growthgrowth rate
Very highgrowth rateVery high
growth rateDecreasinggrowth rateDecreasinggrowth rate
Lowgrowth rate
Lowgrowth rate
Zerogrowth rate
Zerogrowth rate
Negativegrowth rate
Negativegrowth rate
Birth rate
Total population
Death rate
TimeTime
Fig. 10-20 p. 189
Solutions: Influencing Population SizeSolutions: Influencing Population Size
Migration Migration
Environmental refugees Environmental refugees
Reducing births Reducing births
Family planning Family planning
Empowerment of women Empowerment of women
Economic rewards and penalties Economic rewards and penalties