Population Population BiologyBiology

ReviewReview

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I. PopulationsA. Niche —

ecological role of a species in a community.

B. Two different species cannot occupy the same niche.

C. Habitat — where an organism lives. Stream habitat

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I. PopulationsD. A population is a group

of organisms that can interbreed (same species).

E. The largest size a population can grow under ideal conditions is called biotic potential.

F. Factors acting to decreased or limit the size of a population are called limiting factors.

Black Sea Nettle Jellyfish @ Monterey Bay Aquarium

Members of a population can interbreed.

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I. PopulationsG. Examples of

limiting factors are:

1) Water (a)

2) Sunlight (a)

3) Temperature (a)

4) Predators (b)

5) Salinity (a)

6) Disease (b)

7) Competition (b)

8) Food (b)Lava Lake, Oregon

Plants compete for water, sunlight, space and deal with predation from fish,

birds, & man. 4

II Population Growth Curves

We measure the size of a population (number of individuals) over time.

When this is graphed it forms a curve called the population growth curve.

China Hat, near Bend, OregonPlants compete for water, nutrients,

sunlight, space and deal with predation from mammals (including man) & birds.5

II. Population Growth Curves

A. Increase of population size over time.

B. Unrestrictive growth results in exponential growth represented by a J-curve.

C. Forms a characteristic curve called an S-curve.

B C

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II. Population Growth Curves

D. The curve is due to a change in the amount of growth over time.

E. The highest point in the curve is the environment's carrying capacity. This is the number of individuals that can live in that space.

E

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II. Population Growth Curves

F. At this point the natality rate (# born) & mortality rate (# dying) are equal.

G. A combination of all limiting factors is called the environmental resistance.

F

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World Population The world population growth rate rose

from about 1.5 percent per year from 1950-51 to a peak of over 2 percent in the early 1960s due to reductions in mortality.

Growth rates thereafter started to decline due to rising age at marriage as well as increasing availability and use of effective contraceptive methods.

Note that changes in population growth have not always been steady.

A dip in the growth rate from1959-1960, for instance, was due to the Great Leap Forward in China.

During that time, both natural disasters and decreased agricultural output in the wake of massive social reorganization caused China's death rate to rise sharply and its fertility rate to fall by almost half.

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Predator / Prey Animals that kill to eat

are called predators.

Those that are killed and eaten are called prey.

As populations of prey go up populations of predators increase.

As populations of prey go down populations of predators decrease.

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Predator / Prey

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Predator / Prey "When wolf populations

are high, they eat a lot of young moose," explains Rolf Peterson, a Michigan Tech University biologist who's been studying predator-prey dynamics on Isle Royale for decades.

"But 10 years later, there aren't as many old moose." Wolf numbers then nose-dive, and moose thrive again.

This in turn affects the island's vegetation: Balsam firs decline when abundant moose eat young trees before they can reproduce, then rebound when lean moose populations allow them to reach maturity.

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Predator / Prey

At Michigan's Isle Royale National Park, wolf and moose populations rise and fall in connected cycles.

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III. Limiting Factors

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

B. Density — Independent factors not effected by the population’s density

A. Space -- the area, geographical range

B. Weather, seasons, climatic changes

C. Sunlight exposure

D. Fire 14

Zumwalt Prairie, near Enterprise & Joseph, OregonThese Juniper Trees sparsely populate the hillside of North America's largest remaining

grassland of its type. They are competing for water and other

resources.

III. Limiting Factors

C. Density — dependent factors effected by the population’s density.

C. Predation (sometimes)

D. Parasitism

E. Disease

F. Interspecific Competition — two (or more) populations competing for the same limiting factor

G. Intraspecific Competition — competition between members of the same species.

H. Principle of limiting similarity — no two species can occupy the same niche at the same time.

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Zumwalt Prairie, near Enterprise & Joseph,

OregonDeer grazing on the

prairie. They are competing with each other.

They are competing for water, food, shelter and

other resources.

Interspecific & Intraspecific Competition

Zumwalt Prairie, near Enterprise & Joseph, Oregon

Top: Deer graze on the prairie. They are competing with each other and the elk (when in wooded area, not often).

Below: Elk move across road a few miles away from the deer in a wooded area. They are competing the deer (when on prairie, not often). 16

Types of Population Pyramids

1. Expanding / Increasing

2. Expanding / Increasing

3. Stationary

4. Contracting / Declining17

Population Pyramids Graphs show how population pyramids

change over time.

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Population Pyramids

Afghanistan shows classic bulging youth of growing population.

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Population Pyramids

Angola classic bulging youth of growing population. 20

Population Pyramids

China had an extreme youth bulge until the 1960s, when it sharply curbed partly as an effect of the one-child policy.

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Population Pyramids

Russia is reducing its population, declining growth.

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Population Pyramids

Japan is reducing its population, declining growth.

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Population Pyramids

United Kingdom is reducing its population, declining growth.

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Population Pyramids

Mexico’s population is increasing and maybe starting to level off.

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Population Pyramids

Sweden has stable growth.

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Population Pyramids

USA’s population is becoming stable.

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Population Pyramids

Canada’s population is decreasing.

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Current Human Population

U.S. 307,866,146World 6,795,124,089

19:33 UTC (EST+5) Nov 05, 2009

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