Bio120 term test 2 lec 14: Climate and other niche axes

environmental gradients

any continuous environmental variable (temperature, ph, precipitation, etc)

Ranges of tolerance

distance between the highest and lowest environmental value they can tolerate

Lethal zones

• environmental values that are outside of the range of tolerance

• performance of the species is zero

• species can only survive within the range of tolerance

Median range

• where the species is most likely to grow in size

  • performance is high

• where the species can reproduce is even more specific to the median

  • performance is the highest

Ecological niche

• All environmental conditions a species can tolerate physically as well as the resources it needs 

• determines where a species lives in the world (what climate it prefers, what it eats, etc)

• Combination of physiological tolerances and resource requirements of a species

• Each species has a “niche” or a specific way of living that no other species replicates

The Hutchinsonian niche

• Formalized the ecological niche in mathmatical terms 

• Defines an ecological niche as an n-dimensional hypervolume (multiple environmental variables)

• In this model, every "dimension" or axis represents a specific biotic or abiotic environmental factor (such as temperature, pH, humidity, or food size) required for a species to survive and reproduce 

n-Dimensional Hypervolume

An abstract multidimensional space where each point corresponds to a set of environmental conditions that allows a species to maintain a viable population indefinitely

ex. scarlet macaw, ara macao

Global gradients

• temperature

• rainfall

• seasonality

these factors determine biomes

temperature

function of latitude

higher latitude = colder

lower latitude = warmer

seasonality

function of temperature

• warm temperature = summer

• cold temperature = winter

function of rainfall

• dry season

• wet season

rainfall

depends on atmospheric circulation (movement of air around earth), offshore ocean currents, rain shadows (mountains block the moisture that winds would otherwise deliver)

Why is the equator hotter than the poles

the sun shines perpendicularly on the equator and is concentrated over a small area. at the poles, low angle rays spread the same energy over a larger area.

what happens to sunlight as it strikes the surface at lower angles

sunlight spreads over a larger area so each patch gets less energy

how does low sun angle reduce heating

• spreads energy

• rays travel through more atmosphere and absorbs more energy

What causes the seaons

• the earths axial tilt

• the tilt makes each hemisphere lean toward or away from the sun

  • hemispheres take turns leaning toward the sun

  • For part of the orbit the Northern Hemisphere leans toward the sun; six months later, on the opposite side of the orbit, it leans away.

• leaning toward the sun increases the sun angle making days longer and concentrates more energy on a smaller area

• leaning away from the sun decreases the sun angle making the days shorter and concentrates energy over a larger area, passing through more atmosphere.

Hadley cells

• global - scale tropical atmospheric circulation patterns

• strongest circulation cells because equatorial heating is intense and the air is very humid

Atmospheric circulation

large - scale movement of air around he earth that redistributes thermal energy from the sun across the planet

What drives atmospheric circulation

uneven solar heating between the equator and the poles

• warm, humid air rises at the equator

• air cools as it rises, water vapour condenses and falls as rain near the equator

• the air spreads north and south then sinks around 30 degrees latitude

• air warms again as it falls

subtropical high-pressure belts

• dry, high-pressure areas

• located 30 degrees latitude north or south of the equator

• where most deserts lie

What is the ITCZ

• intertropical convergence zone

• low pressure band

• produces heavy rainfall

• line of rain clouds across the pacific

• shifts seasonally

adiabatic cooling

Rising air expands and move towards the atmosphere as pressure falls, and cools without losing heat to its surroundings

dry adiabatic lapse rate

why does sinking air create dry conditions

Compression warms it, lowering relative humidity so clouds evaporate

where do most of the world’s subtropical deserts lie and why?

30 degrees north and south where dry air from the hHadley cell descends. descending dry air under subtropical high pressure creates deserts.

Ferrel cell

• driven by the neighbouring cells

• acts like a middle gear

• churn in the opposite directions of Hadley cells

• sinking air 30 degrees latitude (dry)

• rising air at 60 degrees latitude (wet)

• produces westerlies at the surface

what are polar cells and why are the poles dry

• cell from 60 - 90 degrees in latitude

• cold dense air sinks

• creates high pressure

• cold air holds little moisture therefore very little precipitation making conditions dry

• polar regions are cold deserts

which latitudes are wet and which are dry

wet: 0 and 60 degrees

dry: 30 degrees and the poles

How does the ITCZ’s seasonal movement affect rainfall

• wherever the ITCZ sits air rises and heavy rain falls

• wherever it is moved away, sinking air brings dry weather

• 
  

tropics of cancer and tropics of capricorn

the lines at about 23.5 degrees north and south, marking the farthest points where the sun can be directly overhead

What are the tropics

• the region between the tropic of cancer and the tropic of Capricorn where the sun is overhead at least once a year

• get the most direct sunlight

• highest average temperatures

• least temperature seasonality

What is thermal inertia

how strong a material resists changes in temperature (water has much more than land)

• water resists changes in temperature well

• land does not resist changes in temperature well

Why does the ITCZ move further over asia than over the americas

asia has large landmasses that heat and cool quickly, creating strong low pressure that pulls the ITCZ towards the pole

how does the ITCZ control seasons in the tropics

when the ITCZ’s are overhead there is a wet season and when it moves away, sinking air brings a dry season

monsoon

a seasonal reversal of wind direction that brings a distinct wet season and dry season

Where do the highest recorded air temperatures occur and why?

• in subtropical deserts (30 degrees latitude) where clear, dry sinking air lets in more sunlight

• tropics have the highest average temperatures but peak records occur in the subtropic deserts

Coriolis effect

• deflection o wind due to the earths rotation

• moving air or water curves to the right in the northern hemisphere

• moving air or water moves left in the southern hemisphere

why does the coriolis effect happen

different latitudes spin at different speeds

• fast at the equator (largest distance to travel to complete one full rotation in 24 hours)

• slow near the poles: circular path shrinks meaning the surface speed slows down

Circulation cells + coriolis effect = ____

prevailing wind patterns

which way do the 3 cells move air at the surface?

Hadley: towards the equator

Ferrel: toward the poles

Polar: toward lower latitudes

which wind belt is Toronto in

westerlies: coriolis deflects poleward-moving air eastward, so system moving west to east

Roaring 40s

• strong westerlies at 40 - 50 degrees

• unobstructed winds

whittiker

• biome diagram plot

• x-axis: Mean annual temperature

• y-axis: mean annual precipitation

what climate conditions produce grasslands

moderate temperatures and low rainfall: enough rain to avoid desert, too little to support forests

orographic percipitation

air forced up a mountain, cools and rains on the windward side then descends dry on the leeward side, warming and drying

why does temperature vary more in the north than in the south?

The Northern Hemisphere has more land, which heats and cools faster than water

Where do coastal deserts occur, and why?

Along coasts with cold ocean currents, because cool stable air does not absorb water, producing no rain.

How do niche limits differ from geographic range limits?

The niche is the set of conditions a species can tolerate and use; the geographic range is where it is actually found on the map