Ecology

Organisms Organisms

Niche

• It is an organisms role in the community. It includes: – what it eats– What eats it– What and how much resources it uses

• Can you think of an example?

Limits on population size

• The maximum number of individuals of a species that an area can support is called carrying capacity

• Limiting factors are factors that limit a populations size– Factors can be abiotic or biotic

Population growth

dNdt

1.0N Exponential growth

Logistic growth

dNdt

1.0N1,500 N

1,500

K 1,500

0 5 10 150

500

1,000

1,500

2,000

Number of generations

Pop

ulat

ion

size

(N

)

Limiting factors

• Examples of abiotic include:– Oxygen in a pond,– amount of sunlight – Temperature

• Examples of biotic factors include:– Predators– Competition

Figure 53.10 Examples of terrestrial and marine food chains

Figure 53.11 An antarctic marine food web

Other feeding relationships

• Decomposers break down dead plants and animals.– This recycles the materials

• Scavengers are consumers that eat dead organisms

• Parasites attack living organisms

Figure 54.2 Fungi decomposing a log

Figure 54.11 An idealized pyramid of net production

• Materials are recycled but energy is NOT

• Ecosystems need a constant source of energy from the sun.

Figure 54.17 The carbon cycle

Biodiversity• Is the measure of how many different

species there are in an area

• Ecosystems that have a high biodiversity are more stable

• It is valuable to humans because it can be a source of medicine.

• What other benefits are there?

• Name a human activity that can lead to the loss of biodiversity

Loss of Biodiversity

• Direct Harvesting

• Habitat destruction– Deforestation

• Imported Species

Water Pollution

• Sewage and animal wastes add nutrients to the water

• This causes algae to grow more and die more

• Decomposers suck oxygen out of the water

• If too much oxygen is removed, the fish begin to die

Toxic Wastes

• Chemicals that are added to lakes and rivers can kill off many kinds of organisms

• An example is DDT

• Biological control

Burning fossil fuels

• Burning oil and coal releases CO2 and sulfur into the air

• Sulfur in the air will lead to acid rain that can damage or kill plants and animals– Can cause some lakes to be so acidic that nothing

can live there

• CO2 is a greenhouse gas and can lead to global warming– Ice caps can melt causing a rise in sea level and loss

of coastline

Ozone Depletion

• Ozone is found in the upper atmosphere

• It absorbs much of the harmful radiation from the sun

• Depletion of the ozone will allow more harmful radiation to hit the Earth

• This can lead to higher mutation and cancer rates.