1. 1. What are nitrogen fixers, and why are they important? 2. __________ break dead organisms down into matter. This adds carbon and nitrogen back into the ecosystem. 3. Giant panda bears have a very low birth rate. Before they became a protected species, they were frequently poached, and lost much of their old habitats. Did they have a positive or negative growth rate?

2. What determines our climate?

3.  Climate refers to the average yearly conditions of temperature and precipitation. ◦ Contrast with weather, the day-to-day conditions.  The biggest difference between climate and weather?  Weather changes frequently each day, but climate rarely changes from year to year.

4.  Climate is determined by several factors. 1. How well heat is trapped by the atmosphere. 2. The latitude (north-south position) of each region. 3. The presence of wind and ocean currents. 4. The amount of precipitation present.

5.  Our atmosphere contains trace amounts of important greenhouse gases – gases that are capable of trapping heat energy. ◦ Greenhouse gases include carbon dioxide, methane and water vapor.  Greenhouse gases trap heat energy, which keeps our atmosphere warm. ◦ Without them, Earth would be 30 degrees Celsius cooler. That amounts to 86 degrees Fahrenheit!  However, too many greenhouse gases is not a good thing, either!

6.  Due to Earth’s shape and its tilted axis, the Earth does NOT receive sunlight evenly.  Sunlight is the primary means of heating up the atmosphere. Therefore, certain parts of Earth get a lot of direct sunlight, and are quite warm.  Other parts of Earth get little direct sunlight, and are quite cold.

7.  The polar zones are at the very top and bottom of Earth.  They get very little direct sunlight; the sun’s rays are at very low angles.  These regions are cold year-round.

8.  The tropical zone is located around the equator.  This region gets direct sunlight almost all year round.  As such, this region is quite warm year- round.

9.  The temperate zones are located in between the polar and tropical zones.  The angle of sunlight varies greatly during the year.  As such, climate changes from hot to cold, based on the seasons.

10.  Throughout Earth, warm air and water rises, and cool air and water sinks. This principle is known as convection.  Convection causes air currents, better known as wind.  Convection also causes many ocean currents. Wind also produces ocean currents.  Currents transport heat all over Earth. Warm currents keep climate moderate, and cool currents make climate cold.

11.  Areas close to large bodies of water are likely to see a lot of precipitation. ◦ Why?  Mountain ranges create rain shadows.  Basically, clouds are forced upward due to the mountain range, which cools them down. This makes precipitation much more likely, and the cloud disappears.  As a result, the other side of the mountain is a lot less likely to get precipitation, creating a dry climate behind the mountain range.

12. 1. What is the difference between climate and weather? 2. ___________ gases trap heat in the atmosphere, which keeps Earth warm. 3. The [polar, temperate, tropical] zone(s) have the largest range of possible climates. 4. The [polar, temperate, tropical] zone(s) receive little direct sunlight. 5. True or false: In convection, cool air rises, and warm air sinks.