Changes to Populations

4 factors that effect the size of a population

• Increase Population– 1) Birth– 2) Immigration (entering a

population)

• Decrease Population– 3) Death – 4) Emigration (leaving a population)

Is the population increasing or decreasing?

• When Immigration + Births are greater than Death + Emigration:

• Populations Increase• When Immigration + Births are equal to

Death + Emigration:• Population remains stable• When Immigration + Births are less

than Death + Emigration:• Populations Decrease

Limiting Factor• Something that prevents the

growth of a population

• What would happen without limiting factors?

Reflection

• Think of an example where an organism does not have enough limiting factors.

• What is the organism, how does this affect the habitat around that organism?

Carrying Capacity (k)• the maximum population a species

can maintain in a certain area without damaging the ecosystem

Population can stabilize at K

Populations can crash if #s go above K

• 29 introduced in 1944

• More than 6,000 by 1963

• Down to 42

Seasonal Fluctuations

Limiting Factor #1: Space

• Territorial Animals need a large amount of space

• Loss of Habitat causes the decline of many species

Bluebirds

• Loss of trees/wooden posts caused a huge decline

• Between 1935-1985 numbers declined by 90%

Limiting Factor #2Food and Water

• Leads to death via dehydration, starvation

• Some animals will emigrate• Organisms that rely on one type of

food are severely affected

Darwin’s Finches

• Drought caused a loss in seed numbers

• Finch numbers declined from 1400 to 200

Snowshoe Hare and Lynx

Limiting Factor #3: Climate and Weather

• Temperature changes can affect plants and animals

• Floods and storms can cause death/destruction of habitat

Mosquito Populations

• Mosquitoes breed in standing water

• Rainfall creates puddles of standing water

• Culex tarsalis-WNV

Coffee Habitat

Impact of Temperature Rise on Robusta Coffee in Uganda. Developing countries, whose economies often rely heavily on one or two agricultural products, are especially vulnerable to climate change. This graphic shows that with an increase of only 2 degrees Celsius, there would be a dramatic decrease in the amount of land suitable for growing Robusta coffee in Uganda.

Limiting Factor #4:Cover

• Protection from predators• Protection from weather

Limiting Factor #5:Increase Predation

• An increase in the number of predators to an area

House Cats!

• Predicted that in one year house cats kill 1 billion songbirds!

Limiting Factor #6:Disease

• Spread quickly through high density populations

• Can devastate populations with low genetic diversity

West Nile Virus

• Mosquito born disease

• 5,697 crows reported dead in NYS in 1999

Limiting Factor #7:Light

• Plants that cannot tolerate too much or too little light can be affected

Tree Growth and Shade• Aspen Pine Poplar = intolerant,

will dominate young forests• Beech, fir, hemlock, maple =

tolerant will dominate older forests

Limiting Factor #8:Human Presence

• Close proximity to humans causes some species to emigrate

• Other species thrive

Competition• Limiting factors lead to

competition among organisms for available resources

• A loss in a limiting factor can contribute to a decline in populations

• Increased due to exotic species

Exotic Species-Introduced species not native or endemic to the area in question

(alien species).