Populations Understanding Populations Measuring Populations Human Population Growth.
POPULATIONS
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Transcript of POPULATIONS
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POPULATIONS
Leyda
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I. DESCRIBING A POPULATION1. Geographic distribution: the area
inhabited by a population.
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I. DESCRIBING A POPULATION
2. Population density: the number of individuals per unit area.
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I. DESCRIBING A POPULATION
2. Population density: the number of individuals per unit area.
a. high density: lots of individuals per unit area
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I. DESCRIBING A POPULATION
2. Population density: the number of individuals per unit area.
a. high density: lots of individuals per unit areab. low density: few individuals per unit area
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I. DESCRIBING A POPULATION3. Growth Rate: how quickly a
population changes in size.
Fast Growth Rate: Slow Growth Rate:
55 Minutes!
55 Years!
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II. FACTORS AFFECTING POPULATION GROWTH
1. ________ rate2. ________ rate
a. birth rate = death rate population size
_________________b. birth rate > death rate population size
_________________c. birth rate < death rate population size
_________________
BirthDeath
stays the sameincreasesdecreases
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II. FACTORS AFFECTING POPULATION GROWTH
3. immigration: _________________________________a. example: ___________________________________________
movement of individuals into an areabison immigrates to a meadow full of grass
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II. FACTORS AFFECTING POPULATION GROWTH
4. emigration: _________________________________a. example: ___________________________________________
movement of individuals out of an areabison emigrates out of a meadow without grass
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III. Types of Growth
1. ______________ growth: _________________________________Exponential
Individuals reproduce at a constant rate
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III. Types of Growth
1. ____________ growth: ________________________________
a. Conditions necessary for exponential growth1. Unlimited resources2. Absence of disease and predators
b. Example: Bacteria will double their population in 20 mins
Exponential
Individuals reproduce at a constant rate
Staphylococcus aureus
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III. Types of Growth
c. Shape of graph: J-shapedd. Graph example:
Notice: as time goes on, population increases exponentially.
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III. Types of Growth
2. ________ growth: ______________________________________
_____________a. When does population growth slow or stop?
1. Birthrate – Down2. Immigration – Down3. Death rate – Up4. Emigration – Up
b. Example: Any animal population in nature.
Logistic Population grows rapidly until some factor limits growth
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III. Types of Growth
c. Shape of graph: S-shapedd. Graph example:
Notice: as time goes on, population increases then hits a limit and levels off. This limit is the carrying capacity for that
population.
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III. Types of Growth
e. Carrying capacity: Maximum number of individuals that an area can support.
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IV. Limits to Growth
Limiting factor: something that causes population growth to decrease.
VS
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IV. Limits to Growth
A. Density-dependent limiting factors: When population is high these take effect.1. Competition: Organisms compete for food, water, space, sunlight, and other essentials.
Example: Birds and mice both eat seeds. Effect on Evolution: Both species are put under pressure to change in ways that decrease competition.
Remember Competitive Exclusion Principle!
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IV. Limits to Growth2. Predation: One organism eats
another. Example: Lynx eats rabbit. Predator: Lynx Prey: Rabbit Effect on Evolution: Prey species
(rabbit) evolves defenses (speed, camouflage), predators evolve counter-defenses (eyesight).
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IV. Limits to Growth
Parasitism/disease: Organisms live in and on a host organism.
Examples: Ticks, fleas, leeches, tapeworms, bacteria
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IV. Limits to Growth
B. Density-independent limiting factors: Not related to population size.
1. random events: Unusual weather, natural disasters: volcanoes, hurricanes, floods, ice age
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Density-independent limiting factors: Not related to population size. 2. human disturbances – such as
damming rivers and clear-cutting forests.
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Density dependent or Independent? Lava Flow Number of predators Spread of disease Especially cold winter Toxic chemical spill into a stream Another species competing for same
resource Diverting river for irrigation Beetles that attack trees