Ecology 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 dN dt  1.0N Exponential growth Logistic growth dN dt  1.0N 1,500  N 1,500 K  1, ,000 1,500 2,000 Number of generations Population size (N)

Limiting factors Examples of abiotic include: –Oxygen in a pond, –amount of sunlight –Temperature Examples of biotic factors include: –Predators –Competition

Figure Examples of terrestrial and marine food chains

Figure 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 An idealized pyramid of net production

Materials are recycled but energy is NOT Ecosystems need a constant source of energy from the sun.

Figure 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 CO 2 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 CO 2 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.