Topic 4 - Environmental Heterogeneity (BIOL 2300)

Climate

part of the physical (abiotic) environment having the greatest impact on organisms

• long-term average pattern of weather

weather

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

Earth’s atmosphere

intercepts solar radiation & Earth’s rotation and movement generate prevailing wind & ocean currents

• generates global weather patterns

• results in environmental heterogeneity (=variability in abiotic factors across space)

what do global and regional climate patterns determine

large-scale distribution and abundance of organisms

_______ climate does not match climate patterns in the ______ region (e.g. Winnipeg vs. Manitoba)

local, larger

local - microclimates

patterns are actual environmental conditions experienced by organisms

what is the dominant envr. on Earth

aquatic environment

• ~75% of the planet’s surface is water

mean ocean depth

~3.7 km (max ~ 11km)

75% ~3-6km deep

low degree of microclimate variability and space

~ terrestrial

aquatic envr. - divided by salinity

saltwater and freshwater

aquatic envr. divided by depth

solar radiation that hits water:

1. reflected back into atmosphere

2. absorbed or reflected by suspended particles (alive/dead)

3. absorbed by water

*solar radiation declines exponentially with depth

• distinct vertical profiles of light, temp., oxygen, pressure, etc.

what has had a major influence on evolution of aquatic organisms

decline in solar radiation with depth

• key selection pressure 

aquatic envr. - light

Direct impacts

plants

• plants require sunlight for photosynthesis 

• plants are restricted to top 100m

aquatic envr. - light

Indirect impacts

animals

• herbivores are restricted to depths where plants reside

• animals inhabiting deep water (>200m) have adaptations

3 adaptations of animals inhibiting deep water (>200m)

1. lack pigment

2. large eyes (maximum light-gathering ability)

3. organs that produce light (bioluminescence) 

exponential decline in solar radiation with depth =

temperature declines with depth

thermocline

region of most rapid temperature change

• after thermocline, temp. continues to decline with depth but at a slower rate

some form of _______ _______ occurs in all open bodies of water

thermal stratification

• mixing of the water column can break down this gradient (e.g. winds, currents, seasonal)

as water cools it becomes more _____ until _____ degrees Celsius (maximum density)

• ____ - ____ - less dense

• allows aquatic organisms to survive the winter

dense, 4, 0 - 4

oxygen diffuses form the _______ into ________ environments

atmosphere, aquatic

oxygen is produced by plants during

photosynthesis

what does photosynthesis do

• restricts high concentrations of oxygen to surface waters

• limits respiration and metabolic activity of animals

• mixing of water column (fall) can break down gradient

Shallow Lakes (e.g. Lake Winnipeg)

• ______ blooms → algae die, sink, ______ use up all O2 → “_______ ______” (low O2)

algal, decomposers, dead zones

T/F: higher degree of microclimate variability in time and space (~aquatic)

TRUE

what has had a major influence on evolution of terrestrial organisms

maintaining water balance

• greatest constraint is desiccation (drying out) ~ living cells contain 75-95% water

soil

foundation upon which all terrestrial life depends

• medium for plant growth → provides vertical structure for animals

• controls the fate of water in terrestrial envrs.

• provides habitat for decomposers (~nature’s recycling system)

T/F: moisture-holding capacity of the soil determines availability of water & chemical elements dissolved in soil water

TRUE

what causes variation in the soil moisture-holding capacity

1. climate: directly influences physical and chemical reactions in the soil and water availability

2. type of parent material (from which soil develops): physical & chemical characteristics determine properties of soil (e.g. grain size, acidity, minerals)

3. topography: sloped vs level ground - creates very different micro-climates

4. aspect: north vs south-facing → differ in exposure to solar radiation due to angle of sun (~temp.)

5. presence/absence & type of vegetation: vegetation alters microclimates - light (via shading), temp. (via shading), moisture (via use), wind movement (structure → habitat for animals)