Physical Geography

Spring 2004

Fourth Test: Review

Biotic versus Abiotic agents

Earth’s’ human population= 6 billion. The earth’s population will double in 50 years.

There have been 6 major extinctions in the history of earth- this one is biotic in cause

More than ½ of earth’s original forests are gone (gone by 2050.)

Species extinction = 1,000-30,000 annually

Why? Pollution, loss of habitat, grazing, poaching and collecting

60% of extinction from rain forest clear-cut

Review: community, ecosystem, habitat, ecological succession, Gaia Hypothesis,

autotroph, biomass and niche

Dominant vegetation identifies each biome (forest, savanna, grassland, shrubland, desert and tundra)

Plants are the critical biotic link between solar energy and the biosphere- 270,000 plant species

Chlorophyll absorbs the orange-red and violet-blue wavelengths and reflects green.

Basic photosynthesis equation:

Carbon dioxide + water + sunlight --> glucose, carbohydrate and oxygen

Only 20 species of plants provide 90% of the world’s food supply

Humans eliminate biodiversity through agriculture.

Greater biodiversity means greater stability, greater productivity and a greater chance of survival.

The most abundant elements in living matter are hydrogen, oxygen and carbon

Oxygen and carbon cycles

Key chemical cycles include the gaseous (atmosphere) and sedimentary (mineral and solid phases- nitrogen, phosphorus, etc.) cycles. Photosynthesis and respiration tie oxygen and carbon cycles. Atmosphere is the link between the 2 cycles. Lots of oxygen in the earth’s crust- unavailable to us for use. Same with carbon, except lots of it in ocean (comes from phytoplankton photosynthesis.) In atmosphere plant and animal respiration, volcanoes and fossil fuel consumption produce carbon dioxide. Humans have increased 25% more carbon dioxide to the atmosphere between 1880 and 1970.

Nitrogen Cycle

Nitrogen in atmosphere is not available to us. It is part of make up of organic molecules (essential to living processes.) It is made available to us through nitrogen-fixing bacteria, which are symbiotic with certain plants. These are called legumes, such as clover, alfalfa, soybeans, peas, beans and peanuts. Plants use this nitrogen to make organic matter. Nitrogen in waste is freed back into the atmosphere by bacteria. Humans fix more nitrogen than any other organism (fertilizer for agriculture.) Too much nitrogen has accumulated into the environment. Excessive nitrogen encourages over-growth of algae resulting in diminished oxygen reserves (hypoxic- oxygen depleted.)

Limiting Factors:

1. Elevation limits growth

2. Lack of water

3. Too much water

4. Change in salinity

5. Lack of iron in oceans

6. Low phosphorus

7. Lack of chlorophyll (above 20,000 feet)

PRECIPITATION IS THE NUMBER ONE LIMITING FACTOR

Planetary Impact = Population x Affluence x Technology

Describe the main characteristics of the following:

1. Equatorial and Tropical Rainforest (most diversity, ½ of remaining forests, vertical niches, canopy biomass, 1% of sunlight reaches forest floor, poor soils, recycling system for atmospheric carbon dioxide)

2. Tropical Seasonal Forest and Scrub

3. Topical Savanna

4. Midlatitude Broadleaf and Mixed Forest

5. Needleleaf Forest and Montane Forest

6. Temperate Rain Forest

7. Mediterranean Shrubland

8. Midlatitude Grasslands

9. Deserts

10. Arctic and Alpine Tundra

The study of food webs is a study of what and where things eat and are eaten.

Patch Dynamics- ecosystems as mosaic of communities- striving for optimal range and low environmental stress

Name the generalized plant species broad-biomes (a hint is shrubland)

Discuss the 5 themes of geography using the earth’s major terrestrial biomes to illustrate each theme. (Hint: location, region, movement, human-earth interaction and place)

Alexander von Humboldt developed the concept of “life zones” (altitudinal zonation) while studying in the Andes of Peru. Describe what a life zone is and draw the same conclusions (as Humboldt) concerning the similarities between life zones and global climates systems.

Based upon the planetary impact equation, (below) what factors would keep human population between 12 billion (double the current) and 20 billion (the “carrying capacity of planet”?