in tropical forest ______
light and nutrients are in high demand
The thick canopy in rain forests blocks +++++
light to bottom strata, in response many trees are covered by epiphytes, or, can survive with low light
rain forest fun facts
species richeness is extremely hih
- tree species > 100/km^2
- large mammals are less common though birds and ectotherms abound
taiga
borreal forest, is one of the largest terrestrial biomes on earth
moderate moisture and long cold winteres
- species richess is realatively low but varies season to season
ectotherm diversity such as amphibians and reptiles are low
grasslands
occur where the moisture is too low to support forests
inter-continental climate (cold winters, hot summers)
Marked by seasonal drought and fires, and grazing by large animals
species richness: plants (fairly high), animals (relatively low)
Soil very rich in nutrients
Considered the most endangered biome worldwide (1% of North American prairie left
Tundra or permafrost (Permanent frozen ground)
are bitterly cold, have high winds, low moisture, no trees, short growing season
- Covers 20% of land surface on earth
- Low species richness (animals and plants)
Fauna much richer in summer (migratory birds)
Deserts
defined by lack of moisture
- plants and animals have adapted for water storage and conservation
very hot or very cold
- moderate to very low species richness
Aquatic biome fun facts
cover 75% of the earth’s surface and contain the majority of living space (>90%)
freshwater in northern climates go through
annual cycles
- in early spring water is 4˚C from top to bottom
- Density of water is uniform from top to bottom as is the oxygen distribution
thermocline
Zone between warm and cold water
as atmospheric temperatures warm
thermal stratification sets in form heating of the surface waters
temperature differences in water column create ____
create different water densities
as fall sets in
heat delcines, surface waters cool, density gradients are lost
- water column mixes top to bottom again as in spring
barriers are eroded and deeper waters become re-oxygenated
- water column reaches a uniform temp of 4˚C again
- Ice forms at surface as water cools to 0˚C
In winter a unique property of water emerges
which is to become very dense at 4˚C, an inverted temperature profile is established
- Less dense ice forms at the surface as water continues to cool
- ice insulates and further cooling and ice formation stops
- water column again becomes thermally stratified
Freshwater lakes can be divided in two type
Oligotrophic lakes and eutrophic lakes
Oligotrophic lakes
are nutrient poor, water is clear, cool and oxygen rich; little productivity by algae, often have high diversity of fish
Eutrophic lakes:
are nutrient rich, lots of algal productivity, oxygen poor at times, high algal diversity, but low diversity of fish (winter/summer kill likely)
Rivers
heavily affected by human activites; most large rivers are now dammed at multiple points along their length
- Benthic (bottom dwelling) algae and aquatic insects are a highly diverse group in rivers but senstivie to changes in turbidity, temp and nutrient loading
- currently the WWF is conducitng a health assessment of all of canadian rivers to determine threats and neutralize as many as possible in the coming decade
wetlands
includes marshes bogs, swamps and seasonal ponds
- these are habitats of high biodiversity and productivity
- Many wetlands ahve been lost (>70% on Plains)
- the result of lost wetlands is incraesed flooding; wetlands act a natural reservoir capturing heavy rains and snow melt
- in their absence flooding as beomce a significant issue across the praireis
estuary
where freshwater stream or river merges with the ocean
- highly productive biome; with many euryhaline species
- Given their proximity to the coast (and our own dependence on the coast) the sensitive chemical balance of estuaries is at risk
- They depend on a dynamic but predictable salt cycle which is easily disrupted by human activites
near shore baitats at risk from
human activity
pelagic zone
at risk from overfishing and pollution
near pristine regions
abyssal zones which are currently out of our reach
oceans ______
offer the most stable conditions for life, unfortunately this has resulted in life forms that have minimal abiliteis to adapt and even small changes in temperature can change distributions and disrupt communities
