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Populations and Communities
Populations and Communities
Holt Ch. 5.1Glencoe Ch. 4.1
Holt Ch. 5.1Glencoe Ch. 4.1
Population: a group of organisms of the same species that live together in one place at one time and interbreed.
Population growth is important because populations of different species (including humans) interact in communities
Population: a group of organisms of the same species that live together in one place at one time and interbreed.
Population growth is important because populations of different species (including humans) interact in communities
Population growth depends on 4 factors:
Population growth depends on 4 factors:
1. Births
2. Deaths
3. Immigration (movement of individuals into a population)
4. Emigration (movement of individuals out of a population)
1. Births
2. Deaths
3. Immigration (movement of individuals into a population)
4. Emigration (movement of individuals out of a population)
Two kinds of population growth:
Two kinds of population growth:
Exponential
logistic
Exponential
logistic
Exponential growthExponential growth
Numbers increase by a certain factor in each time period
J-shaped graph
Numbers increase by a certain factor in each time period
J-shaped graph
Logistic growthLogistic growth
Begins with a minimum number of individuals and reaches a maximum at the carrying capacity of the habitat
S - shaped graph
Begins with a minimum number of individuals and reaches a maximum at the carrying capacity of the habitat
S - shaped graph
Carrying capacityCarrying capacity
The maximum population an environment can support at any given time
The maximum population an environment can support at any given time
Actual logistic growthActual logistic growth
Logistic growth curveLogistic growth curve
Factors affecting population size
Factors affecting population size
Abiotic factors: Weather, climate
Biotic factors:foodpredators diseaseparasiteshumans
Abiotic factors: Weather, climate
Biotic factors:foodpredators diseaseparasiteshumans
Density-dependent factors limiting growth
Density-dependent factors limiting growth
Variables that are affected by the number of individualsnumber of individuals present
Ex: availability of nest sites, food, water,competition, migration
Variables that are affected by the number of individualsnumber of individuals present
Ex: availability of nest sites, food, water,competition, migration
Density-independent factors affecting growthDensity-independent
factors affecting growth
Variables that affect a population regardless of population sizeregardless of population size
Ex: weather, flood, fire
Variables that affect a population regardless of population sizeregardless of population size
Ex: weather, flood, fire
Human populationHuman population
Demography: the study of human population Size Density Distribution Movement (immigration/emigration) Births and deaths
Demography: the study of human population Size Density Distribution Movement (immigration/emigration) Births and deaths
Human populationHuman population
Slow growth in the past
> 7 billion now Industrial revolution
increased growth Better sanitation,
hygiene, vaccines, nutrition, agricultural technology
Slow growth in the past
> 7 billion now Industrial revolution
increased growth Better sanitation,
hygiene, vaccines, nutrition, agricultural technology
Can the Human Population keep increasing forever?
Can the Human Population keep increasing forever?
Humans can alter the environment and change
the carrying capacity
Humans can alter the environment and change
the carrying capacity
Exponential GrowthDr. Albert A. Bartlett
Exponential GrowthDr. Albert A. Bartlett
The Most Important Video pt. 1
The Most Important Video pt. 2 3:36
The Most Important Video pt. 1
The Most Important Video pt. 2 3:36
Demographic Transition ModelDemographic Transition Model A geographical model used to
explain the change from high birth rates and high death rates to low birth rates and low death rates as part of the economic development of a country from a pre-industrial to an industrialized economy.
A geographical model used to explain the change from high birth rates and high death rates to low birth rates and low death rates as part of the economic development of a country from a pre-industrial to an industrialized economy.
Population pyramidPopulation pyramid
A graph used to show the population distribution over gender and age of a population
A graph used to show the population distribution over gender and age of a population
The Lynx and
the Snowshoe Hare
The Lynx and
the Snowshoe Hare
Canadian lynx only eat meat. Snowshoe hares are a very important food for these cats, and when there are fewer hares to eat, the number of lynx decreases.
In some areas lynx eat only hares, but in other areas they also eat rodents, birds, fish, or sick or weak deer. They also eat carcasses left by human hunters. Fox, D. and T.
Murphy 2002"Lynx canadensis" (On-line), Animal Diversity Web
Canadian lynx only eat meat. Snowshoe hares are a very important food for these cats, and when there are fewer hares to eat, the number of lynx decreases.
In some areas lynx eat only hares, but in other areas they also eat rodents, birds, fish, or sick or weak deer. They also eat carcasses left by human hunters. Fox, D. and T.
Murphy 2002"Lynx canadensis" (On-line), Animal Diversity Web
Snowshoe hares are famous for their seasonal molts.
In the summer, the coat of the hare is reddish brown or gray, but during the winter, the coat is snowy white.
Snowshoe hares are famous for their seasonal molts.
In the summer, the coat of the hare is reddish brown or gray, but during the winter, the coat is snowy white.
snowshoe hares eat green grasses, forbs, brome, wild strawberry, dandelions, clovers, and daisies. During the winter, snowshoe hares forage on buds, twigs, bark, and evergreens. At all times, it is important for hares to re-ingest certain feces. Because much of the digestion of food occurs in their hindguts, in order to extract all of the available nutrients from their food, they must cycle it through their digestive system a second time. (Kurta, 1995; Wilson and Ruff, 1999)
snowshoe hares eat green grasses, forbs, brome, wild strawberry, dandelions, clovers, and daisies. During the winter, snowshoe hares forage on buds, twigs, bark, and evergreens. At all times, it is important for hares to re-ingest certain feces. Because much of the digestion of food occurs in their hindguts, in order to extract all of the available nutrients from their food, they must cycle it through their digestive system a second time. (Kurta, 1995; Wilson and Ruff, 1999)
An adult Hare can travel up to 27 miles per
hour
can cover up to 10 feet in a single bound
change direction and leap vertically
An adult Hare can travel up to 27 miles per
hour
can cover up to 10 feet in a single bound
change direction and leap vertically
