POPULATIONS

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POPULATIONS Leyda

description

Leyda. POPULATIONS. I. DESCRIBING A POPULATION. Geographic distribution : the area inhabited by a population. I. DESCRIBING A POPULATION. 2. Population density : the number of individuals per unit area . I. DESCRIBING A POPULATION. - PowerPoint PPT Presentation

Transcript of POPULATIONS

Page 1: POPULATIONS

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