AP ENV - Chapter 3

r-strategists

have high reproductive rates and thrive in unstable environments

k-strategists

have lower reproductive rates and thrive in stable environments

R strategies

• not endangered

• have many offspring and tend to overproduce

• low parental care

• mature rapidly

• short lived

• tend to be prey

• tend to be small

• examples: insects, bacteria, rodents

K strategies

• most endangered

• have few offpsring

• high parental care

• mature slowly

• tend to be large

• examples: humans, elephants, sharks

survivorship curves

shows age distribution characteristics of species, reproductive strategies and life history

Type 1: Late loss

characterized by high survival rates during early and middle life, with a significant drop in survival in older age groups. (ex. humans and large mammals)

Type 2: Constant loss

death rate is constant from birth to death and predation is the primary cause of death (ex. rodents and perennial plants)

Type 3: Early loss

have great numbers of offspring and reproduce for most of their life (ex. sea turtles, trees, fish)

carrying capacity (K)

refers to the number of individuals that can be supported sustainably in a given area without degrading the environment or depleting resources.

regulating factors

• amount of sunlight available

• food availability

• nutrient leveles in soil profiles

• oxygen content in aquatic ecosystems

• space

population dispersal pattern

how individuals or species become distributed in different spaces over certain periods of time

clumped pattern

a population dispersal pattern dense with organisms, while other areas contain few members

clumped pattern examples

• Animals living in social families.

• Animals that feel safer living in groups

• Animals that serve as prey

• Animals that work together to trap or corner prey.

• Animals with inability of their offspring to independently move from their habitat.

random pattern

occurs in habitats where environmental conditions and resources are consistent, with little interaction among members

uniform pattern

space is maximized between individuals to minimize competition

biotic potential

the maximum reproductive capacity of an organism under optimum conditions

factors that increase biotic potential

• able to adapt and migrate

• resistance to disease

• favorable env conditions

• high birth rate

• few competitors

factors that decrease biotic potential

• unable to adapt or migrate

• little defense against diseases

• too many competitors

• inadequate food supply

j-curve

represents rapid population growth in a new environment, increasing exponentially until environmental resistance abruptly curbs it

s-curve

occurs when the population density of an organism initially increases but then stabilizes due to the finite amount of resources available

positive feedback loops

stimulate change and are responsible for sudden or rapid changes within ecosystems

negative feedback loops

provide stability in ecosystems by preventing populations from exceeding carrying capacity, regulated by predator-prey dynamics

feedback loops

limiting factors

environmental conditions that restrict population growth and distribution

rule of 70

helps to explain the time periods involved in exponential population growth

doubling time

the amount of time it takes for a population to double in size

doubling time formula

dt = 70/r

important population formulas

• Birth Rate (%) = [(total births/total population)] × 100

• Crude Birth Rate (CBR) = [(b ÷ p) × 1,000]

• Death Rate (%) = [(total deaths/total population)]× 100

• Crude Death Rate (CDR) = [(d ÷ p) × 1,000]

• Doubling Time = 70/% growth rate

• Emigration = number leaving a population

• Global Population Growth Rate (%) = [(CBR – CDR)]/10

• Immigration = number entering a population

• National Population Growth Rate (%) = [(CBR + immigration) – (CDR + emigration)]/10

• Percent Rate of Change = [(new # - old #)/old #] × 100

• Population Density = total population size/total area

impacts of population growth

biodiversity declines, oceans are overexploited, forests are lost, freshwater decreases, etc.

age-structure diagrams

determined by birth rate, generation time, death rate and sex ratios

pyramid shaped age structure diagram

high birth rates and the majority of the population is in the reproductive age group

bell shape age-structure diagram

pre=reproductive and reproductive age groups are more nearly equal

urn shaped age structure diagram

post reproductive group is largest and the pre reproductive group is smallest, a result of the birth rate’s falling below the death rate

total fertility rate

the average number of children that each woman will have during her lifetime

pre earth wisdom

natural cycles that can serve as a model for human behavior

frontier worldview

viewed undeveloped land as a hostile wilderness to be cleared and planted

planetary management

beliefs that as the planet’s most important species, we are in charge of the earth

current earth wisdom

beliefs that nature exists for all earth’s species and we are not in charge of earth, resources are limited and should not be wasted

demographic transition

a model that describes the stages a country goes through as it transitions from high birth and death rates to low birth and death rates.

stage 1: pre industrial

high birth and death rates, little population growth, often due to subsistence agriculture and limited medical care

stage 2: transitional

occurs after the start of industrialization, population rises rapidly

stage 3: industrial

birth rates begin to decline, death rates stabilize, leading to slower population growth as families have fewer children.

stage 4: post industrial

low birth and death rates, leading to a stable or declining population

stage 5: sub replacement fertility

death rates exceed birth rates, resulting in a declining population over time.