Transcript Unit 3 Ecosystems

Topic 10
The 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:
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–
–
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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 5-2
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