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