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.