Unit 3 Populations

Numbers

Numbers

number of individuals in a population

Sex Ratio

ratio of males to females in a population

Distribution

how individuals are distributed with respect to one another

Age Structure

how many individuals fit into a particular age category

Density

number of individuals per unit area at a given tiem

Random Distribution

Uniform Distribution

organisms that are territorial competing for resources (biotic & abiotic)

Clumped Distribution

herd animals with more resources in an area (biotic & abiotic)

Population Size

total number of individuals within a defined area at a given time

Inputs that increase population are immigrants & births

Outputs that decrease population size are emigration & deaths

New-Old/Old = annual growth rate

Biotic Potential

under ideal conditions/unlimited resources populations grow at max potential

Intrinsic Growth Rate - r

maximum potential for growth

Environmental/Limiting Factors

slows growth rate (less food, more predators, disease)

Density Dependent Limiting Factors

greater impact as density increases, biotic, determines the carrying capacity (k) of population (ex. disease, predation, competition)

Density Independent Limiting Factors

not relevant to density, abiotic, does not determine the k (ex. weather, natural disasters, fires, etc.)

Logistic Growth

when a population whose growth is initially exponential, but slows as the population reaches the carrying capacity

Carrying Capacity

amount of organisms an ecosystem can hold; point where population growth levels off/stops in density dependent growth

Change as limiting factors change + what limiting factor is can change = change in carrying capacity

Exponential Growth

(j-curve) growth of population with no limiting factors

Overshooting K

when population does not respond to carrying capacity & grows out of control

Resource depletion, environmental damage, disease, famine, conflict (above carrying capacity)

Dieback

a rapid decrease in numbers experienced by a population of organism that has temporarily exceeded or overshot its carrying capacity

Niche Specialist Species

Species that require specific habitats, have a limited diet, narrow range of tolerance but have advantage in a constant habitat

Niche Generalist Species

species that live in a variety of habitats, feed on a variety of food, have a broad ecological tolerance, and advantage in environmental change

K Species

usually mammals that live a long time, have a long time till reproductive maturity, have few offspring with parental care, large offspring

Population growth is slow, limited by density dependent factors, stable near carrying capacity

R species

have short life spans, quick to mature with many reproductive events, a lot of offspring with no parental care, offspring is small in size

Population growth rate is fast (highly variable), limited by density independent factors, no carrying capacity = exponential growth

Survivorship Curves

describes how the likelihood of surviving changes over a life span

Type 1 Survivorship Curve

most organisms that are born & survive to mid life because survivorship declines after reproduction (old age) ex. most mammals - k species

Type 2 Survivorship Curve

no matter what age chance of surviving = chance of dying (ex. birds, smaller mammals, squirrels)

Type 3 Survivorship Curve

high mortality rate at young age - very few make it to old age but have better survival once older (ex. plants, insects, fish)

Demography

the study of human populations and population trends

Changes in population size, fertility, life expectancy, age structure, migration

Immigration

movement into a country

Emigration

movement out of a country

Net Migration Rate

difference between immigration and emigration in a given year per 1,000 people in a country changes in population size

Crude Birth Rate

(CBR) the number of births per 1,000 individuals per year

Births/Population x 1,000 = CBR %

Crude Death Rate

(CDR) the number of deaths per 1,000 individuals per year

Death/Population x 1,000 = CDR %

Global Population Growth Rate

(CBR-CDR)/10 = %

National Population Growth Rate

(CBR+immigration) - (CDR+emigration)/population

Doubling Time

70/growth rate = years

Total Fertility Rate

(TFR) average estimate of number of children each women in a population will bear

Replacement Fertility Rate

(RLF) total fertility rate required to offset the average number of deaths in a population and to ensure current population size stays stable

Developed Countries (high levels of industrialization/income) RLF: 2.1

Developing Countries (low industrialization/income less $3 person) RLF: >2.1

Higher RLF if lower chance of making it reproductive age

Lower Fertility Rate is correlated with

Education opportunities for women

Gender Equality

Employment opportunities for women

Equality = lower fertility because women have s say

Life Expectancy

average number of years that an infant born in a particular year in a country is expect to live, given current average lifespan and death rate of that country

Low life expectancy corresponds with HIGH infant mortality rate

Indicates quality of life

Infant Mortality Rate

the number of deaths of children under 1 year of age per 1,000 live births

Indicates quality of life

Child Mortality Rate

the number of deaths of children under age 5 per 1,000 live births