APES Unit 3 - Populations

generalist

larger range of tolerance, broader niche makes them less prone to extinction & more likely to be invasive

generalists characteristics

Broad food requirement

High adaptability

Less likely to become extinct

Broad niche

Use a variety of resources

High Range of tolerance

Advantage when change of conditions

specialists

smaller range of tolerance, or narrower ecological niche makes them more prone to extinction

specialists characteristics

Specific food requirements (bamboo)

Less ability to adapt to new conditions

narrow niche

more likely to become extinct

use a specific set of resources

easily affected by changing conditions

have an advantage with constant conditions

why are generalist species advantaged in habitats that change constantly?

they are able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources

why are specialists advantaged in habitats that remain more constant?

they can thrive only in a narrow range of environmental conditions or has a limited diet.

K-selected species characteristics

Few offspring, heavy parental care to protect them

Usually reproduce many times

Long lifespan, long time to sexual maturity = low biotic potential = slow pop. growth rate

More likely to be disrupted by env. change or invasives

K-selected species

most mammals, birds, chimpanzee, humans

R-selected species characteristics

Many offspring, little to no care

May reproduce only once

Shorter lifespan, quick to sexual maturity = high biotic potential = high pop. growth rate

More likely to be invasive

Better suited for rapidly changing env. conditions

R-selected species

insects, fish, plants

biotic potential

The maximum reproductive capacity of an organism under optimum environmental conditions

biotic potential of salmon and whales

whales have low biotic potential because they have fewer offspring salmon have high biotic potential because they have many offspring

Describe whether invasives species are generally k-selected or r-selected

generally r-selected due to their quick pop. growth and faster generation time

why are k-selected species are more negatively impacted by invasive species than r-selected species

Invasives outcompete for resources with high biotic potential & rapid pop. growth, therefore making k selected species less likely to adapt & more likely to go extinct

age cohort

people born at roughly the same time who pass through the life course together

survivorship curve

line that shows survival rate of a cohort (group of same-aged individuals) in a pop. from birth to death

Type 1 Curve

K selected

High survivorship early in life due to high parental care

High survivorship in mid life due to large size & defensive behavior

Rapid decrease in survivorship in late life as old age sets in

Type 2 curve

in between r and k selected

Steadily decreasing survivorship throughout life

Type 3 Curve

r selected

High mortality (low survivorship) early in life due to little to no parental care

Few make it to midlife; slow, steady decline in survivorship in mid life

Even fewer make it to adulthood; slow decline in survivorship in old age

why K-selected species generally follow survivorship curve I

They invest a lot of parental care to their offspring which is why their family sizes are smaller. Because time, energy and resources are invested into child rearing

Why do r-selected species generally follow survivorship curve 3?

most of the offspring die off during their early ages and the few live to their old age.

carrying capacity

the max. Number of individuals in a pop. that an ecosystem can support (based on limiting resources)

what factors determine the carrying capacity for deer in a temperate forest ecosystem

disease, predator/prey relationships, habitat destruction and degradation, food availability, hunting pressure, and weather conditions.

overshoot

when a population briefly exceeds carrying capacity

Ex: deer breed in fall, give birth all at once in spring; sudden spike in pop. = overshoot

die off/back

harp decrease in pop. size when resource depletion (overshoot) leads to many individuals dying

Ex: many deer starve with too many new fawns feeding in spring

limiting resource

a particular natural resource that, when limited, determines the carrying capacity of an ecosystem for a particular species.

examples of a limiting resource for a moose population in a boreal forest ecosystem

Predation, habitat, hunting, and environmental conditions have all been implicated as regulatory mechanisms

mortality

the frequency of death in a population.

fecundity

the potential to for a female to become pregnant and carry that pregnancy to a live birth in demography,

how do decreasing resources impact the carrying capacity for a given population

population growth rate slows and eventually stops = known as logistic growth. The population size at which growth stops = the carrying capacity (K), which is the number of individuals of a particular population that the environment can support.

density independent factor

factors that influence pop. growth independent of their size

Ex: natural disasters (flood, hurricane, tornado, fire)

Density-Dependent Factors

factors that influence pop. growth based on size:

Ex: food, competition for habitat, water, light, even disease

A population that is growing and grow at an even faster rate in the future

A population that is in a steady state of gradual population growth

A population that is experiencing negative growth

the significance of the base (0-14 age cohorts) of an age structure diagram

prereproductive

current & future growth

population momentum

a consequence of the demographic transition. explains why a population will continue to grow even if the fertility rate declines. defined as the ratio of the size of the population at that new equilibrium level to the size of the initial population.

TFR

avg. number of children a woman in a population will bear throughout her lifetime

Higher TFR = higher birth rate, higher pop. growth rate (generally)

Factors affecting TFR

Development (Affluence): more developed, or wealthy nations have a lower TFR than less developed nations

More educational access for women

More econ. opportunity for women

Higher access to family planning education & contraceptives

Later age of first pregnancy

Less need for children to provide income through agricultural labor

Gov. Policy: can play a huge role in fertility by coercive (forceful) or noncoercive (encouraging) policies

Forced or vol. sterilization

China’s 1 (now 2) child policy

Tax incentives to have fewer children

Microcredits or loans to women without children to start businesses

replacement level fertility rate

the TFR required to offset deaths in a population and keep population size stable

why is replacement level fertility rate higher in developing nations than in developed nations

due to higher infant mortality

the base replacement level fertility rate in developed nations

About 2.1 in developed countries (replace mom & dad)

infant mortality rate

number of deaths of children under 1 year per 1,000 people in a pop.

Higher in less developed countries due to lack of access to: health care, clean water, enough food

Higher IMR = higher TFR, due to families having replacement children

2 factors that contribute to a higher infant mortality rate

No access to clean water

no access to healthcare (hospitals, vaccines, vitamins & supplements for moms & babies)

the relationship between education for women and TFR

More education = fewer unplanned pregnancies

More education = more job. opportunities for women

Alternative to marrying young

Crude Birth Rate & Crude Death Rate (CBR & CDR)

Births & deaths per 1,000 people in a pop.

the equation for determining the growth rate of a country using CBR and CDR

[CBR-CDR] / 10

Thomas Malthus’ theory about human population growth

Earth has a human carrying capacity, probably based on food production

Human population growth is happening faster than growth of food production

Humans will reach a carrying capacity limited by food

the rule of 70

The time it takes (in years) for a population to double is equal to 70 divided by the growth rate

theory of demographic transition

the transition from high to lower birth a death rates in a country or region as development occurs and that country moves from a pre-industrial to an industrialized economic system.

Stage 1 - Preindustrial

High IMR & high death rate due to lack of access to clean water, stable food supply, and healthcare

High TFR due to lack of access to:

Ed. for women

Contraceptives/family planning

Need for child agricultural labor

Little to no growth due to high CBR & CDR balancing each other out

Ex: Virtually no country is in this phase

Stage 2 - Industrializing/Developing

Modernizations brings access to clean water, healthcare, stable food supply

IMR & CDR decline

TFR remains high due to

Lack of ed. for women & contraceptives/family planning

Need for child agricultural labor

Generational lag ( takes time for ed. & societal change to spread

Rapid growth, due to high CBR and declining CDR

Low per capita GDP

Shorter life-expectancy

High infant mortality

High TFR

Low literacy rate & school life expectancy for girls

Stage 3 - Developed/Industrialized

Modernized economy and society increase family income, so TFR declines significantly due to

More ed. opportunities for women

Delayed age of marriage & first child to focus on ed./career

Access to family planning & contraceptives

Slowing growth rate as CBR drops closer to CDR

High per capita GDP

Long life-expectancy

Low infant mortality

TFR, near replacement level (2.1)

High literacy rate & school life expectancy for all

Stage 4 - Post-Industrialized/Highly Developed

Highly modernized countries that are very affluent

TFR declines even further as families become more wealthy and spend even more time on educational & career pursuits

Increased wealth & education brings even more prevalent use of family planning & contraception

CBR drops lower that CDR & growth becomes negative(pop. decline)

Very high per capita GDP

Longest life-expectancy

TFR, below replacement level (2.1)

Highest contraceptive use rates