Population Ecology Every second….5 people are born, 2 people die, ….net gain 3 people.

Population Ecology

Every second….5 people are born, 2 people die,

….net gain 3 people.

Population Ecology

Deals with the # of individuals of a particular species that are found in an area and how and why those # change or remain fixed over time.

Population ecologists study…

How populations respond to its environmentCompetition for resources, predations, disease and other environmental pressures

Population GrowthJ-shaped curve1. Exponential growth– growth rate under ideal conditions2. Uncheck growth (carrying capacity not yet met)

J-shaped

Exponential growth!

S-Shaped Curve

1. An S-shaped curve shows that the population grows slowly at first & then increases more and more quickly.

S-Shaped Curve

2. At carrying capacity, growth of the population will remain the same.

3. Carrying capacity is the number of organisms that an environment can support indefinitely.

A. Births will approximately equal DEATHS.

B. When the population overshoots the carrying results in LIMITING factors death to outnumber births.

C. Limiting Factor is a factor that will limit population growth.

1) Food availability2) Disease3) Predators4) Space

Reproductive Patterns

A. Rapid life history (example: mosquitoes)

a. Rapid reproductionb. High number of offspring

Reproductive Patterns

c. Small body sized. Organisms mature rapidly

e. Reproduce earlyf. Organisms have a short life span

B. Slow life history (example: elephant)

a. Slow reproductionb. Low number of offspring

c.Large body size

d. Organisms mature slowly

e. Reproduce late in lifef. Organisms have a long life span

g. Organisms tend to have parental care

Population density & growth

Population density is the number of individuals in a given area.

Density–DEPENDENT factor

Factor that limits population size or density

A. Disease (example: HIV)B. CompetitionC. PredatorsD. ParasitesE.FoodF.WaterG.Territory 

Density -INDEPENDENT factor:

Usually a weather related event.It affects ALL populations regardless of size.

A. TemperatureB. StormsC. FloodsD. DroughtE. Volcanic eruption

Predator-prey relationship

A.Predators affect prey populations

B. Prey affect predator populations

Intraspecies competitionA. SpaceB. FoodC. WaterD. Reproduction

Invasive Species –

uncontrolled competition

Project World Population Growth

Demography Study of HUMAN population size, density, distribution, movement, BIRTH rates & death rates.

World Population Growth

Year Population

1 200 million

1000 275 million

1500 450 million

1650 500 million

1750 700 million

1804 1 billion

1850 1.2 billion

1900 1.6 billion

1927 2 billion

1950 2.55 billion

1955 2.8 billion

1960 3 billion

1965 3.3 billion

1970 3.7 billion

1975 4 billion

1980 4.5 billion

1985 4.85 billion

1990 5.3 billion

1995 5.7 billion

1999 6 billion

2006 6.5 billion

2009 6.8 billion

2011 7 billion

2025 8 billion

2050 9.4 billion

Humans can alter their environment thus affect the POPULATION GROWTH RATE.

1. Famine2. Eradicate Disease3. War4. Better food production

Calculating Growth Rate

Growth rate (r) = birth rate (b)+ I – death rate (d) + E

Immigration – movement of individuals into a population

Emigration – movement of individuals into a population

Doubling time – time needed for population to double in size

Zero population growth – birthrate = death rate

Birthrate – number of live births per 1000 in a given year

Death rate – number of deaths per 1000 in a given year

Demographics of Countries

Demographics – applied science that deals with population statistics.

Developed countries

1. Low birth rates

2.Low infant mortality rates. (the # of infant deaths per 1000 live births)

Developed countries

1996 US 7.5/1000 for infant moralityWorld average 62/1000

Developed countries

3.Usually have longer life expectancy

Developed countries

4.Examples of developed countries:

US, Canada, Sweden, Germany, France, Australia, Japan

Moderately developed countries

Examples:1. Mexico2. Turkey3. Thailand (most S. American nations)

Developing Countries

Less developed countries

Examples:1. Bangledesh 2. Niger3.Ethiopia4.Laos 5.Cambodia

These countries have …………High birth and mortality rates than developed countriesShort life spans

Another factor to examine is the replacement level fertility. This is number of children a couple must have to “replace” themselves. Replacement rate is 2.1 children in developed countries.

The replacement rate in developing countries is 2.7 children.

Age Structure of Countries

In order to predict future population it is important to know the age structure.

Age Structure of Countries

Age structure is the numbernumber and proportion at each ageage in a population. The number of malesmales and femalesfemales at each age.

The overall structure of the age tells whether the population is increasing, stable or shrinking.

Stable growth – approximately the same number of individuals at each age grouping

Rapid growth – a large proportion of the population is 19 years old or younger

Slow growth – a large proportion of population is 55 years old or younger

Declining growth – the largest portion of the population is 20-40 years, smaller groups are younger