How populations grow Chapter 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 (units 2 )

How populations grow Population density – number of individuals living in a defined space # of individuals area (units 2 ) 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 limiting factor 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 Wolf 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 Wolf 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 Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship This decline is soon followed by decrease in the wolf population moose wolf Wolf 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 Wolf 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 Wolf and Moose population on Isle Royale

Density-dependent factors Predation – predator-prey relationship This cycle continues indefinitely moose wolf Wolf 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