5-4 reading quiz

Demography

study of a population (density, distribution, growth rate)

Population density

number of individuals per unit area (ex: 73 persons per square mile in US) individuals aren't always uniformly distributed

Population distribution

pattern of dispersal of individuals across an area

Resources

biotic and abiotic components of an environment supporting living organisms

Limiting factors

environmental aspects that determine where an organism lives (ex: trout live in cool mountain streams where oxygen levels are high, but carp and catfish live in rivers near the coast bc the can live in warm waters with low oxygen levels)

Timberline

limit of tree growth. Can't grow above high timberline bc of low temps and the water being frozen most of the year

Biotic factors distribution example

red kangaroos in australia live in arid inland areas bc it's adapted to feeding on grasses that grow there

Distribution patterns

3 distribution patterns: clumped, random, and uniform (full range of the species)

Range

portion of the globe where the species can be found

Things that influence distribution patterns

resource availability, territoriality, seed disbursement

Rate of natural increase

growth rate. It is dependent on: number of individuals born each year and die each year (if 30 ppl are born and 10 die each year, per 1,000 individuals the growth rate would be 2%)

Biotic potential

highest possible rate of natural increase for a population when resources are unlimited

High or low biotic potential

is determined by: usual number of offspring per reproductive event, chances of survival till age of reproduction, how often individuals reproduce, and age at which reproduction occurs

Cohort

all members of a population born at the same time (bluegrass cohort has 843 but after 0-3 months 121 die)

Survivorship

probability of newborn individuals of a cohort surviving to particular ages

Survivorship curve type 1

individuals survive well past midpoint of life span (large mammals and humans in well developed places)

Survivorship curve type 3

individuals die very young (invertebrates, fish, humans in less developed places)

Survivorship curve type 2

survivorship decreases at a constant rate throughout life span (songbirds and small mammals)

Jeffery Kassner

studies the distribution of hard clam in great south bay (used a crane with a clamshell bucket to take bottom grabs of the hard clams and then they used a hose to separate the clams from sediment and counted them)

Hard clam abundance

is associated with sediment oyster shell content

Distribution of hard clams

was found that hard clams were not distributed evenly but had high and low abundance areas (abundant areas=beds)

Importance of hard clam distribution

Knowing the distribution and abundance of hard clams is important to brookhaven bc ownership carries with it an obligation to manage a hard clam fishing industry that has a yearly value of $10 million and employs 300 fisherman (economic benefits)

Major age groups in a population

3 major age groups in a population: prereproductive, reproductive, postreproductive

Pyramid shaped diagram

prereproductive group is largest

Bell-shaped diagram

reproductive group is equal to size of prereproductive group

Urn-shaped diagram

postreproductive group is the largest

Patterns of population growth

2 patterns of population growth: discrete breeding and continuous breeding

Discrete breeding

members of a population have only 1 reproductive event in life (ex: many insects like mayflies and annual plants like zinnias)

Continuous breeding

members of a population reproduce many times in their life (ex: most vertebrates, shrubs, and trees)

Exponential growth

number of individuals added each generation increases as the total number if females increase

Exponential growth curve

makes a J-shaped curve. Because growth accelerates over time, the size of a population can increase dramatically.

Exponential growth

A type of growth that accelerates over time, characterized by a lag phase (slow growth) and an exponential growth phase (accelerating growth).

Population size year to year equation

Nt+1=RNt, where Nt is the population size at time t.

Sigmoidal curve

A type of curve that represents the growth of yeast cells in a lab culture, showing a slow start followed by rapid growth.

Logistic growth

A growth model that includes a lag phase, exponential growth phase, deceleration phase, and stable equilibrium phase.

Logistic growth equation

dN/dt=rN(K-N)/K, where dN/dt is the change in population size over time.

Function of change in time

triangleN/triangleT=rN, representing the rate of change in population size.

Instantaneous population growth

dN/dt=rN, indicating the growth rate at a specific moment.

Carrying capacity

The maximum number of individuals of a given species that the environment can support.

Population crash

A decline in population size that can occur when the population exceeds the carrying capacity.

Density-independent factors

Abiotic factors like weather or natural disasters that affect population size regardless of density.

Density-dependent factors

Biotic factors such as predation and competition that increase in effect as population density increases.

Competition

Occurs when members of the same species compete for limited resources, leading to unequal access.

Predation

The act of one organism eating another, with higher density increasing the likelihood of predation.

Intrinsic factors

Factors based on the anatomy, physiology, or behavior of an organism.

Human population growth

Approximately 216,000 people are added to the world every day.

Doubling time

The length of time it takes for the population size to double, estimated to be about 53 years.

More developed countries (MDCs)

Countries with low population growth and higher standards of living, such as North America and Europe.

Less developed countries (LDCs)

Countries with rapid population growth and high poverty levels, such as Latin America and Africa.

Demographic transition

The process of decreasing death rates followed by decreasing birth rates.

MDC's yearly growth rate

Approximately 0.1%.

US yearly growth rate

Approximately 0.6%, influenced by immigration.

LDC's birth rate

Decreased from 2.5% in 1960-1965 to 1.6% now.

Zero population growth

A condition where there is no increase in population size.

Replacement reproduction

Occurs when more women enter reproductive age than women leave.

Nigeria's population prediction

Projected to grow from 130 million to 300 million by 2050, with 44% under 15 and an average of 5.8 children per woman.

African population projection

Expected to increase from 840 million to 1.8 billion by 2050.