Topic 10The Distribution of Organisms

Ecosystem• Recall that an ecosystem is defined as a

community of living organisms interacting with each other and the physical environment.

• The major categories of components are:– Biota– Atmosphere– Soil– Water

Important abiotic factors• Terrestrial ecosystems:

– Atmospheric—Light intensity, humidity, precipitation, air temperature

– Soil—nutrient availability, moisture, pH, texture and porosity, temperature

– Water—precipitation levels, pH• Aquatic ecosystems:

– Atmospheric—wind speed and direction, air temperature, light intensity

– Water—dissolved nutrients, run-off, precipitation, turbidity, oxygen saturation (DO), water temperature

• Marine ecosystems:– Nutrient availability, salinity, air and water

temperature, wind speed and direction (influences currents), turbidity, dissolved gases

Earth’s Climate Zones

Figure 5-2Figure 5-2

Terrestrial biome distribution

Climate constraints

Range of tolerance

• Tolerance ranges exist for multiple factors: temperature, pH, light intensity, oxygen or carbon dioxide availability, salinity, etc.• This is closely related to the concept of limiting factors.• The distribution of species is determined by the ranges of abiotic factors present in an area.

Gradients• Abiotic factors are not evenly distributed within

ecosystems.– Stratification

• This leads to micro-habitats within ecosystems

Gradients

What keeps a species in a place?

• Evolutionary constraints• On what level does evolution take

place?– Individuals– Populations– Species

• What is the mechanism of evolution?

Evolution and adaptations

Evolution and adaptations

Evolution and adaptations