Lecture 1: Distributional aspects of biodiversity:
Resources – exhaustible e.g. nutrients and space
Conditions – inexhaustible e.g. temperature, pH, salinity
Aspects of performance: Individual survival individual growth reproduction
Death zone has 1/3 oxygen level as sea level.
Factors imp. For terrestrial plants from biggest to smallest:
1) temp 2) soil moisture 3)nutrients: N is imp,P,K 4)Disturbance like fire 5) Disease,
Herbivores, pollinators, mycorrhizal fungi
For aquatic plants, there is also salinity, but no moisture and fire. Phosphorus is very imp.
For terrestrial animals it’s important to have:
1) Food and water 2) temperature 3) Habitat 4) Predation/disease
For aquatic animals, salinity and osmotic pressure is important.
Animals tend to follow plants
Temperature is different depending on latitude.
High latitudes = cold = seasonality because of temperature. (summer/winter)
Low latitudes = warm = seasonality because of rainfall. (dry/wet seasons)
Rainfall depends on atmospheric circulation, ocean currents and rain shadows.
At high latitudes, light strikes the earth (at low angle) with more surface area than head on
(high angle) at the equator.
This differential heating drives the Earth’s atmospheric heat engine.
Hadley cells make equatorial regions rainy. Heated air rises, air cools as rises. Adiabatic
lapse rate : rate of decrease of atmospheric temperature with increase in altitude. 5-10
degrees celcius per km.
As air cools, water vapor condenses and falls as rain near equator. Then as air falls, it warms
up again (reversal of adiabatic process). This causes dry, high pressure areas at + and – 30
Remember experiment where gas pressure was decreased and so did temperature.
Atmospheric cells lock like gear train: Hadley cell Ferrell cell polar cell
Air goes up at equator and anywhere else is wet.
Air goes down at 30 degrees (Horse Latitudes) and anywhere else where air goes down e.g.
north pole is dry. Same cells in north and south hemispheres. Intertropical convergence zone (ITCZ) shifts seasonally, producing wet and dry seasons in
pts of the tropics. It’s known as the doldrums = area around equator where northeast and
southeast trade winds come together. In the Northern hemisphere, trade winds from NE to