Distribution of Species and Communities

Question 1

Why are particular species present in some places and absent in others?

Answer 1

If a species occupies a particular area:

• it either evolved there
• or evolved somewhere else and dispersed to that area

If a species is not found in a particular area:

• either it evolved elsewhere and never dispersed there
• or it was once present but no longer is there

Question 2

Biogeographical regions

Answer 2

• Based on the taxonomic similarities of the organisms living there
• Boundaries are set where species composition changes dramatically over short distances

Question 3

Weather

Answer 3

The short-term state of atmospheric conditions at a particular place and time

Question 4

Climate

Answer 4

The long-term average atmospheric conditions found over time

Temperature, precipitation, wind velocity

Question 5

Why does climate vary?

Answer 5

Because of differences in the amount of solar energy

Drives global atmospheric and oceanic circulation

Question 6

Temperature (Types of Cycles)

Answer 6

Daily and Seasonal Cycles

Question 7

Daily cycle

Answer 7

Rotation of Earth on its axis (24 hour cycle)

Question 8

Seasonal Cycle

Answer 8

Annual (fixed axial tilt at 23.5)
Variation in sunlight intensity and day length give rise to seasonal variation in temperature in north & south hemispheres

Question 9

Why are tropic regions hotter than temperate regions?

Answer 9

1. solar radiation stikes at almost right angles near equator but at acute angles near the poles
2. same amount of radiant heat is concentrated over smaller area at tropics
3. at poles solar radiation passes through deep layer of atmosphere (reflection, absorption, scattering)

Question 10

Tropic Rainforests (Equator)

Answer 10

Radiant heat above the equator warms the air (low pressure) at the equator and moist, hot air rises to cooler altitudes and rains

Question 11

Deserts (30 N and 30 S)

Answer 11

Cool air descends at latitudes or about 30 N and S and heats