Population of Ecology

Ecology

Study of the interactions of organisms in their biotic and abiotic environments

Organism population community Ecosystem biophsere

Demographics of populations

Demography – statistical study of a population (density, distribution, growth rate)

Population density - # of individuals per unit area (can be misleading)

Population distribution – pattern of dispersal across an area (controlled by resources and limiting factors) clumped, random, uniform

Population growth

Rate of natural growth (r) based on birth and death rate.

Biotic potential – highest possible growth rate with unlimited resources.

Survivorship curves

Probability that newborn will survive to certain ages.

Curve I – characteristic of a population in which most individuals survive well past midpoint of lifespan. Ex. Large mammals, humans

Curve II – survivorship decreases at a constant rate throughout the life span. Ex. Songbird, small mammals (death is usually unrelated to age)

Curve III – most individuals die young. Ex. Insects, fish, humans in less developing countries.

Age distribution

Age structure diagrams Increasing population

Prereproductive ages is largest, birth rate is higher than death rate.

Stable population (bell shape) Reproductive ages equal prereproductive ages

Decreasing population (urn shape) reproductive ages is larger than prereproductive ages,

postreproductive age is largest

Population Growth Models

2 patterns of population growth:Discrete breeding – single reproductive eventContinuous breeding – many reproductive

eventsResearch: not always have to be one or the

other.

Exponential Growth

Number of individuals added each generation increases as the total # of females increases.

Lag phase – growth is slow to start Exponential growth phase – accelerated

growth J shaped curve

Logistic growth

S-shaped curve Lag phase, exponential growth phase Deceleration phase – growth slows Stable equilibrium phase – little to no

growth, BR = DR

Carrying capacity

Maximum # of individuals of a species an environment can support.

Exponential growth can not continue due to carrying capacity Resources become scarce Competition and predation

Exponential growth occurs when population size is much lower than carrying capacity.

Population stabilizes when carrying capacity is reached.

Regulation of population size Density independent factors – those that

are not dependent on numbersWeather, natural disasters

Density dependent factors – occur because of population of speciesCompetition, predation, parasitism

Intrinsic factors? – anatomy, behavior have an affect on population?

Life History Patterns - Opportunistic

r – strategists Small individuals, short life span, fast to

mature, many offspring, little/no care for offspring, early reproductive age

Bacteria, fungi, insects, rodents, annuals

Life History Pattern - Equilibrium

K-strategists Large individuals, long life span, slow to

mature, few and large offspring, care for offspring, most live to reproductive age

Large mammals, birds of prey, long-lived plants

Human population growth

MDC’s – North America, Europe, Japan, Australia, growth is slow

LDC’s – Latin America, Africa, Asia, population rising rapidly

Ways to reduce projected population increase: Strengthen family planning Education, raising status of women, reduce child

mortality Delay onset of childbearing, wider spacing of births

Population Growth and Environmental Impact

LCD = population growth in numbers MCD = consume larger proportion of Eart

h’s resources Average family in North America

consumes the amount of resources and produces wastes of 30 people from India.