how populations grow and limits to growth. three important characteristics of a population are 1....

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SECTION 5-1 AND 5-2 NOTES How populations grow and Limits to growth

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Page 1: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

SECTION 5-1 AND 5-2 NOTES

How populations grow and Limits to growth

Page 2: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Three important characteristics of a population are

1. Geographic distribution2. Density3. Growth rate

Characteristics of Populations

Page 3: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

A term that describes the area inhabited by a population.

Vary in size.

Geographic distribution (range)

Page 4: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Number of individuals per unit area.

PD = number of individuals / unit area ORPD = number of individuals divided by unit area

Population Density

Page 5: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Three factors affect population size:1. Number of births2. Number of deaths3. Number of individuals that enter

or leave the population.

Immigration – movement of individuals into an area.Emigration – movement of individuals out of an area.

Population Growth Rate

Page 6: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Animals emigrate.Decline

Animals immigrate.Growth

More births than deaths.Growth

More deaths than births. Decline

Same number of deaths to births. Stays the same

Population growth or decline?

Page 7: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Two types of population growth graphs1. Exponential growth2. Logistic growth

Population growth graphs

Page 8: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Exponential growthA population with Abundant space Abundant food Protected from

predators and disease

Under ideal conditions with unlimited resources, a population will grow exponentially.

Page 9: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Logistic Growth As resources become less available, the growth of a population slows or stops.

Occurs when a population’s growth slows or stops following a period of exponential growth.

Page 10: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Logistic Growth

Carrying capacity – the largest number of individuals that a given environment can support

Consider your own house’s carrying capacity.

Page 11: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Review Break!Suppose that the total penguin population was 1200 at the beginning of the year and 1600 at the end of the year. What was the population’s growth?

Answer: increase of 400 penguinsSuppose 250 penguin chicks died during the year. What was the population’s growth?

Answer: Net increase of 150 penguinsSuppose that 200 adult penguins also died during the year. What was the population’s growth?

Answer: A net decrease of 50 penguins

Page 12: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Review Break!List three characteristics that are used to describe a population.

Answer: Geographic distribution, density, growth rate What is the equation for population density?

PD = number of individuals/unit areaWhat is carrying capacity?

Answer: largest number of individuals that a given environment can support.

Page 13: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

What is a specific limiting factor we have discussed before?

Limiting nutrient

Limiting factor – a factor that causes population growth to decrease

Examples: Competition, predation, parasitism/disease, drought and other climate extremes, human disturbances

Limiting factors

Page 14: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

A limiting factor that depends on population size

Examples: Competition, predation, parasitism, and disease.

Density-dependent limiting factor

Page 15: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

When populations become crowded, organisms compete with one another for food, water, space, sunlight, and other essentials.

Competition occurs between members of the same species and different species.

Density-dependent limiting factorCompetition

Page 16: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Regulation of a population by predation takes place within a predator-prey relationship – population control

Density-dependent limiting factorPredation

Page 17: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

First, why is this density-dependent?

Parasites are like predators – take nourishment at expense of hosts, often weakening and causing disease or death.

Density-dependent limiting factorParasitism and Disease

Page 18: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Affect all populations in similar ways, regardless of the population size.

Examples: Unusual weather, natural disasters, seasonal cycles, and certain human activities – such as damming rivers and clear-cutting forests

Density-independent factors

Page 19: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Contrasting density-dependent/density-independent1. Competition2. Human activities 3. Predation4. Parasitism5. Unusual weather6. Disease7. Natural disasters

Review Break!

Page 20: How populations grow and Limits to growth. Three important characteristics of a population are 1. Geographic distribution 2. Density 3. Growth rate Characteristics

Are density-dependent limiting factors abiotic or biotic factors?

Answer: Biotic factors

Are density-dependent limiting factors abiotic or biotic factors?

Answer: Abiotic factors

Review Break!