Lecture 14: Climate and other Niche Axes Flashcards
ecological niche
Combination of physiological tolerances and resource requirements of a species (essentially the species’ place in world, in environment, their behaviours and food)
Hutchinsonian niche
Designed by G. Evelyn Hutchinson. Concept that a niche is an n-dimensional hypervolume in which each axis is an ecological factor. Climatic variables are important variables as niche axes.
Hadley cell
Make equatorial regions rainy (up to tropic of cancer and tropic of capricorn). As hot air rises (because it is less dense), it cools by 5°-10°C/km, and water vapour condenses and falls as rain near the equator. The air warms again as it falls. This cell affects the equator and subtropics. Just past Hadley cells (+/- 30° latitude) there are dry, high pressure areas).
Ferrel cell
Not driven by temperature. Move in opposite direction of polar and hadley cells. Mid latitude segment of earth’s wind circulation. Air flows poleward and eastward near the surface and equatorward and westward near higher altitudes. Transport heat from equator towards poles.
Polar cell
Cold, dense air moves from polar regions to about 60°-70° N or S heating up as it moves away from polar regions and rising up and back over. Weakest cell.
Temperature is mostly a function of…
latitude
Higher latitudes
Are colder; seasonality is mostly a function of temperature (summer and winter)
Lower latitudes
are warmer; seasonality is mostly a function of rainfall (dry season and wet season)
Rainfall depends on
mostly atmospheric circulation, offshore ocean currents, and rain shadows.
Biome
A distinct biological community that has formed in response to a shared physical environment. Determined by temperature, seasonality, rainfall.
How does the earth’s tilt produce seasons?
The earth is tilted such that as it loops around the sun the light hits the surface at different angles. At higher altitudes, the lights strikes the earth at a lower angle (thus it is spread over a greater area and is weaker). Near the equator the angle is higher (nearly perpendicular to surface) meaning a more direct area is hit by the light (stronger).
Tropic of Cancer
The northern tropic. 23° N ish of equator. Generally hot and dry with two seasons being an extremely hot summer and warm winter. Some easterly coastal regions have excessive rainfall. Much of the land under tropic of cancer is saharan desert. On the June solstice the northern hemisphere is pointed towards the sun and the sun is directly overhead the tropic of cancer.
Tropic of Capricorn
The southern tropic. 23° S ish of equator. Contains subsolar point (sun directly overhead) on the December solstice.
Where are the tropics found?
Tropic of Capricorn to Tropic of Cancer (23°S - 23°N) including equator.
ITCZ
Intertropical Convergence Zone circles the earth generally near the equator where the trade winds (northeast and southeast) meet. Characterized by low pressure, lack of wind, convective activity which generates thunderstorms, Active over continental land masses and less so over bodies of water.
Where is the ITCZ situated?
Shifts throughout the year, as the area with most direct sunlight shifts. Warm air is less dense thus creates lower air pressure. ITCZ follows heat. Lags behind the sun’s relative position by about 1 to 2 months. In July and August it is about 5° - 15 ° N (after June 21 solstice (tropic of cancer)) of the equator (but further north over land masses because water has a higher heat capacity than land) and in January over the Atlantic (after December 21 solstice where subsolar point is at capricorn), sits no further north than the equator but extends south over Africa, SA, Asia.
Trade Winds
Wind blows from high pressure to low pressure areas. There are areas of high pressure at 30° N and S, and the equator is an area of low pressure so wind is being blown towards equator from north and south. The northeast and southeast trade winds are a result of these winds deflecting from Coriolis effect. Blow to the west from the east.
Coriolis effect
Earth’s surface rotates faster at the equator than the poles. Earth’s rotation causes moving bodies at its surface to be deflected. Trade winds from north and south slant westward.
Where do you find areas of low pressure and high pressure?
Low pressure zones are a result of rising air (a lot of rainfall). These zones are found where polar and ferrel cells meet and also where the north and south hadley cells meet (rainforest and tropical areas). High pressure zones result from descending air (clear skies, little rain). Found where the ferrel and Hadley cells meet and at the poles (deserts and tundra).
How many atmospheric cells are there
Three. Each hemisphere has one of each. Polar cells preside over the poles and hadley cells over the equator. Ferrel cells are found between hadley and act as gear.
What direction do winds blow away from the equator towards the north and south pole? Explain why.
Moving away from equator always results in overshoot as land underneath is moving slower as you travel polewards. As winds blow from equator to poles they blow eastward (westerlies).
What direction do winds blow towards the equator from the north and south pole? Explain why.
Towards equator moving bodies fall behind so winds from the north pole and south pole deflects to the left. These are the trade winds (northeast and southeast) which converge at the equator
Which directions do winds circulate in northern and southern hemisphere?
Low pressure areas suck in air. In the northern hemisphere, the northeast trade winds push west and meet wind flowing from equator that deflects to the right resulting in a circulating cell going counter-clockwise turn. In the southern hemisphere the southeast trade winds also push west and meet the winds coming from equator which deflect to the right resulting in a circular air current spinning clockwise.
Wandering albatross
They circumnavigate the northern hemisphere in counterclockwise motion and southern hemisphere in clockwise motion taking advantage of prevailing winds—polar easterlies and westerlies interacting (once they pass 30°N or S). They expend only slightly more energy flying than resting.
