How populations growChapter 14 – Notesheet II

14-3 – population density & distribution

14-4 – population growth curves

How populations grow Population density –

How populations grow Population density – number of

individuals living in a defined space

How populations grow Population density – number of

individuals living in a defined space # of individuals

area (units2)

How populations grow Population density – number of

individuals living in a defined space # of individuals

area (units2)• example of low density• example of high density

How populations grow Population dispersion -

How populations grow Population dispersion – way in which

individuals of a population are spread in an area or a volume

How populations grow Population dispersion – way in which

individuals of a population are spread in an area or a volume

How populations grow Survivorship curve -

How populations grow Survivorship curve – generalized

diagram showing the number of surviving members over time from a measured set of births.

How populations grow Survivorship curve

type 1 -- common among large mammals; low level of infant mortality;

high level of parental care for young

How populations grow Survivorship curve

type 2 – birds, small mammals, and some reptiles; survivorship is roughly equal at all points in

organisms life – just as likely to live as to die

How populations grow Survivorship curve

type 3 – invertebrates, fish, amphibians, and plants; very high birth

rate and infant mortality rate; many offspring die

from predation; low level of parental care for young

Population Growth Curves Immigration -

Population Growth Curves Immigration – the movement of

individuals into a population from another population

Population Growth Curves Immigration – the movement of

individuals into a population from another population Example -

Population Growth Curves Immigration – the movement of

individuals into a population from another population Example -animals in search of mates or

food arrive from outside the population

Population Growth Curves Emigration -

Population Growth Curves Emigration – movement of

individuals out of a population and into another population

Population Growth Curves Emigration – movement of

individuals out of a population and into another population Example -

Population Growth Curves Emigration – movement of

individuals out of a population and into another population Example – young animals approach

maturity and leave area to establish new territories

Population Growth Curves Exponential growth -

Population Growth Curves Exponential growth – occurs when a

population size increases dramatically over a period of time

Exponential growth A graph of exponential growth would

be

Exponential growth A graph of exponential growth would

be J-shaped

Exponential growth A graph of exponential growth would

be J-shaped Example -

Exponential growth A graph of exponential growth would

be J-shaped Example – bacteria, rabbits in Australia

Exponential growth A graph of exponential growth would

be J-shaped Example – bacteria, rabbits in Australia

• Usually occurs

Exponential growth A graph of exponential growth would

be J-shaped Example – bacteria, rabbits in Australia

• Usually occurs under ideal conditions with

Exponential growth A graph of exponential growth would

be J-shaped Example – bacteria, rabbits in Australia

• Usually occurs under ideal conditions with unlimited resources

Exponential growth Bacteria - some are able to

reproduce every 20 minutes

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be __

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4• Another 20 minutes there will be ___

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4• Another 20 minutes there will be 8• In another hour there will be ___

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4• Another 20 minutes there will be 8• In another hour there will be 64• In 2 more hours there will be ___

Exponential growth Bacteria - some are able to

reproduce every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4• Another 20 minutes there will be 8• In another hour there will be 64• In 2 more hours there will be 512• In just one day there will be ___

Exponential growth Bacteria - some are able to reproduce

every 20 minutes If you begin with one bacteria

• 20 minutes later there will be 2• Another 20 minutes there will be 4• Another 20 minutes there will be 8• In another hour there will be 64• In 2 more hours there will be 512• In just one day there will be

4,720,000,000,000,000,000,000

How population grow Logistic growth -

How population grow Logistic growth – occurs when a

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

How population grow Logistic growth – occurs when a

population’s growth slows or stops following a period of exponential growth Why might this happen?

How population grow Logistic growth – occurs when a

population’s growth slows or stops following a period of exponential growth Why might this happen?

• Birthrate decreases

How population grow Logistic growth – occurs when a

population’s growth slows or stops following a period of exponential growth Why might this happen?

• Birthrate decreases• Deathrate increases

How population grow Logistic growth – occurs when a

population’s growth slows or stops following a period of exponential growth Why might this happen?

• Birthrate decreases• Deathrate increases• Or both events occur at same time

How population grow Logistic growth – occurs when a

population’s growth slows or stops following a period of exponential growth Why might this happen?

• Birthrate decreases• Deathrate increases• Or both events occur at same time

Logistic growth Graph would be

“S-shaped”

Time (hours)

Number of yeast cells

Logistic growth Graph would be

“S-shaped” Initial growth

would be ___

Time (hours)

Number of yeast cells

Logistic growth Graph would be

“S-shaped” Initial growth

would be slow, followed by a period of ___

Time (hours)

Number of yeast cells

Logistic growth Graph would be

“S-shaped” Initial growth

would be slow, followed by a period of rapid growth

Time (hours)

Number of yeast cells

Logistic growth Graph would be

“S-shaped” Initial growth

would be slow, followed by a period of rapid growth

Growth then___ Time (hours)

Number of yeast cells

Logistic growth Graph would be

“S-shaped” Initial growth

would be slow, followed by a period of rapid growth

Growth then levels off

Time (hours)

Number of yeast cells

Logistic growth Caused by some

sort of __________________ on the

population.

Time (hours)

Number of yeast cells

Logistic growth Caused by some

sort of limitingfactor on the

population.

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

the largest number of individuals that a given environment can support

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

What if conditions

change?

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

What if conditions

change? The carrying

capacity will also change

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

Where is carrying

capacity on “S” shaped curve?

Time (hours)

Number of yeast cells

Logistic growth Carrying capacity -

Where is carrying

capacity on “S” shaped curve?

Time (hours)

Number of yeast cells

Carrying capacity

Limits on growth Population crash -

Limits on growth Population crash – a dramatic

decline in the size of a population over a short period of time

Limits on growth Population crash – a dramatic

decline in the size of a population over a short period of time Example -

Limits on growth Limiting factors -

Limits on growth Limiting factors – a factor that

causes population growth to decrease

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples -

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples –

• competition

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples –

• Competition• predation

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples –

• Competition• Predation• Parasitism and disease

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples –

• Competition• Predation• Parasitism and disease• Drought and other climate extremes

Limits on growth Limiting factors – a factor that

causes population growth to decrease Examples –

• Competition• Predation• Parasitism and disease• Drought and other climate extremes• Human disturbances

Limits on growth Density-dependent factors -

Limits on growth Density-dependent factors – a

limiting factor that depends on population size;

Limits on growth Density-dependent factors – a

limiting factor that depends on population size; limits only when population density reaches a certain level

Limits on growth Density-dependent factors –

Growth rate _________ as density _________

Limits on growth Density-dependent factors –

Growth rate decreases as density increases

Density-dependent factors Competition

Density-dependent factors Competition

Members of population compete with one another for resources such as food and shelter

Density-dependent factors Competition

Members of population compete with one another for resources such as food and shelter

As populations become denser, the resources are used up, limiting how large the population can grow

Density-dependent factors Predation -

Density-dependent factors Predation – predator-prey relationship

As the wolves prey on the moose, the moose population _________

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

As the wolves prey on the moose, the moose population decreases

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

This decline is soon followed by _________in the wolf population

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

This decline is soon followed by decreasein the wolf population

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

This decline (of wolf) means the moose has fewer enemies and will therefore eventually ________

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

This decline (of wolf) means the moose has fewer enemies and will therefore eventually increase

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship

This cycle continues indefinitely

moose wolf

0

60

30

0

1200

2400Wolf and Moose population on Isle Royale

Density-dependent factors Parasitism and disease -

Density-dependent factors Parasitism and disease –

Example-

Density-dependent factors Parasitism and disease –

Example- eggs of parasitic wasp inserted beneath skin of larval moth (caterpillar)

Limits on growth Density-independent factors -

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples -

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Unusual weather

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Unusual weather – periodic drought can affect the entire population of grass – and ultimately the food web

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Natural disasters

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Natural disasters – volcanoes, tsunamis, tornados, and hurricanes can wipe out populations regardless of density

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Human activities

Limits on growth Density-independent factors – affect

all populations in similar ways, regardless of the population size or density Examples –

• Human activities – threaten habitats by clearing forests, filling wetlands, polluting the air, land and water