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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 environment Competition for resources, predations, disease and other environmental pressures
Population Growth J-shaped curve 1. Exponential growth– growth rate under ideal conditions 2. 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.
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 availability 2) Disease 3) Predators 4) Space
Reproductive Patterns A. Rapid life history (example: mosquitoes) a. Rapid reproduction b. High number of offspring
Reproductive Patterns c. Small body size d. Organisms mature rapidly e. Reproduce early f. Organisms have a short life span
B. Slow life history (example: elephant) a. Slow reproduction b. Low number of offspring c. Large body size
d. Organisms mature slowly e. Reproduce late in life f. 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. Competition C. Predators D. Parasites E.Food F.Water G.Territory
Density -INDEPENDENT factor: Usually a weather related event. It affects ALL populations regardless of size.
A. Temperature B. Storms C. Floods D. Drought E. Volcanic eruption
Predator-prey relationship A.Predators affect prey populations B. Prey affect predator populations
Intraspecies competition A. Space B. Food C. Water D. 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
YearPopulation 1200 million 1000275 million 1500450 million 1650500 million 1750700 million 18041 billion 18501.2 billion 19001.6 billion 19272 billion 19502.55 billion 19552.8 billion 19603 billion 19653.3 billion 19703.7 billion 19754 billion 19804.5 billion 19854.85 billion 19905.3 billion 19955.7 billion 19996 billion 20066.5 billion 20096.8 billion 20117 billion 20258 billion 20509.4 billion
Humans can alter their environment thus affect the POPULATION GROWTH RATE.
1. Famine 2. Eradicate Disease 3. War 4. 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 morality World 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. Mexico 2. Turkey 3. Thailand (most S. American nations) Developing Countries
Less developed countries Examples: 1. Bangledesh 2. Niger 3.Ethiopia 4.Laos 5.Cambodia
These countries have ………… High birth and mortality rates than developed countries Short 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 number age malesfemales Age structure is the number and proportion at each age in a population. The number of males and females 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
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