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1

Environmental Heterogeneity

• Climate is the part of the physical (abiotic) environment that has the greatest impact on an organism

2

– Weather

combination of temperature, humidity, precipitation, wind, cloudiness at a specific place and time

3

Climate

long-term average pattern of weather

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Earth’s atmosphere intercepts solar radiation

– Earth’s rotation and movement generate prevailing winds and ocean currents • Together these generate global weather patterns
– Results in environmental heterogeneity (=variability in abiotic factors across space)

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• Weather patterns differ at different spatial scales:

– Global → Regional → Local → Micro

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Global and regional climate patterns determine the l

the large-scale distribution of plants and animals

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Microclimate

– Local climatic conditions do not match the general climate profiles of the larger region
• Because local patterns of microclimate are the actual environmental conditions experienced by organisms → our focus

8

Aquatic Environment

Dominant environment on Earth
~ 75 % of the planet’s surface is water
• •

Low degree of microclimate variability in time and space
Divided by salinity: saltwater and freshwater
Divided by depth
– Solar radiation is:
• Reflected back into atmosphere
• Absorbed or reflected by suspended particles (alive & dead)
• Absorbed by water
Solar radiation declines exponentially with depth
→ Distinct vertical profiles of light, temperature, oxygen, pressure, etc.

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Aquatic Environment - Light

• •
Direct impact: plants
– Plants require sunlight for photosynthesis
– Plants are restricted to top 100 m
Indirect impact: animals
– Herbivores are restricted to depths where plants reside
– Animals inhabiting deep water (> 200 m) have adaptations:
• Lack pigment
• Large eyes (maximum light-gathering ability)
• Organs that produce light (bioluminescence)

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– Thermocline

region with most rapid decline in temperature
• After temperature continues to decline with depth but at a slower rate

11

Aquatic Environment - Temperature


Exponential decline in solar radiation with depth → decline in temperature with
depth
– Thermocline
– Some form of thermal stratification occurs in all open bodies of water
– Mixing of the water column can break down this gradient (e.g. winds, currents,
seasonal)
– as water cools, it becomes more dense until 4oC (max density) → 4- 0 oC is less
dense

12

Aquatic Environment - Oxygen

• Oxygen diffuses from the atmosphere into aquatic environments • Oxygen produced by plants during photosynthesis
– Restricts high concentrations of oxygen to surface waters
– Limits respiration and metabolic activity of animals
– Mixing of the water column can break down this gradient

13

Terrestrial Environment

• Higher degree of microclimate variability in time and space
• Greatest constraint is desiccation (drying out) ~ living cells contain 75 - 95 % water
• Soil is the foundation upon which all terrestrial life depends
• Medium for plant growth
→ provides vertical structure for animal life
• Controls the fate of water in terrestrial environments
• Provides habitat for decomposers (Nature’s recycling system)

14

Terrestrial Environment
• Moisture-holding capacity of the soil is critical for availability of:

– water
– chemical elements dissolved in soil water

15

What causes variation in the moisture-holding capacity?

1. Climate
2. Type of parent material
3. Topography
4. Aspect
5. Presence/absence & type of vegetatio n

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Vegetation
- habitat for animals

Eg. Different bird species depend on vegetation of different heights

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1. Climate

directly influences the physical & chemical reactions in the soil & water availability

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2. Type of parent material

- material from which soil develops
• Physical and chemical characteristics determine properties of soil

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3. Topography

eg. Slope, level ground

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4. Aspect

north vs south-facing sites
• Differ in their exposure to solar radiation

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5. Presence/absence & type of vegetatio n

– Vegetation alters microclimates:
• Light (via shading)
• Temperature (via shading)
• Moisture (via use)
• Wind movement
• Structure – habitat for animals

22

vegetation

provides high diversity of microclimates for terrestrial environments