Study Questions--Week 1--Answers

1. 1. Draw a diagram of the earth indicating the position of convection

cells for both the north and the south hemispheres, also indicate all

high and low pressure systems, areas of high and low precipitation, and

explain why these occur where they are found.

Diagram of earth showing three convection cells for each hemisphere. For

the northern hemisphere air rises at the equator, moves north and drops 30

degree latitude and returns south on the earth's surface. The cell between 30

and 60 degrees latitude rotates in the opposite direction as the first cell

described and the cell between 60 and the north pole rotates in the same

direction as the first cell. Low pressure systems found at equator and the 60

degree latitude, high pressure systems found at 30 degree latitude and at the

poles. Conversely, high precipitation areas are found near the equator and

the 60 degree latitude, whereas low precipitation areas are found around the

30 degree latitude and at the poles.

2. Give a concise definition of ecology.

Ecology is the scientific study of interactions between organisms and both

other organisms and their environment, as well as the study of interactions

affecting the distribution and abundance of organisms.

3. Explain how the fields of ecology and evolution are two interacting

fields.

Ecology and evolution are both sciences which study the interactions between

organisms and their environment; however, ecology is concerned with shorter

time scales ( ~a few generations), and evolution is concerned with long-term

processes that involve genetic change (i.e. adaptations).

4. Explain why some biomes are distributed longitudinally while

others are distributed latitudinally.

Convection cells form large, global bands of wind driven climate patterns,

which lead to the latitudinal distribution of biomes. However, the topography

of land masses, especially mountain ranges, disturb this global pattern and

lead to the distribution of longitudinal biomes. For example, north-south

mountain ranges, such as the Sierra Nevada, cause the air passing over them

(usually in the form of wind) to spread both north and south, rise, and then

to cool. This leads to precipitation, and more moist environments, on the

western side of these mountain ranges, and drier biomes on the eastern side,

forming longitudinal bands of biomes.

5. Compare and contrast Aristotle's Classic view of nature to

Darwin's modern view.

Aristotle had four main points in his theory: 1) species are eternal and

non-changing, 2) "essentialism"- every species has a fixed and perfect

essence, 3) the Scala Naturae, the hierarchy of species, and 4) the Balance of

Nature. Darwin, on the other hand, believed that species were constantly

changing, adapting to new environments, and leading to the formation of new

species over time due to the process of natural selection.

6. Draw a diagram of the global wind patterns on the earth's surface

and explain their directionality.

See example from your lecture notes. Wind directionality is formed by two

processes: convection cells (giving the northerly or southerly momentum) and

the Coriolis Effect (causing winds to be deflected slightly east or west due

to the rotation of the earth and the different speeds with which the earth

rotates between the equator and the poles).

7. Why are models, although simple and based on numerous assumptions,

a useful tool in science.

Models are useful to help us better understand systems and their dynamics. By

breaking systems down into simpler parts according to models, we can control

for other factors and manipulate only the factors that we are interested in.

This can decrease the confusion (or noise) caused by so many different

environmental factors.

8. What five environmental conditions are required for the origin of

life.

1). Moderate temperature range (between 0-100 degrees Celsius)

2). Free Water

3). Solar or chemical energy

4). Small organic molecules (carbon in the form of carbon dioxide, Ammonia,

sulfates, carboxyls)

5). Minerals

9. What is the current estimate for the origin of life and what

evidence is this based on.

4.1 Billions years ago, based on a discovery of fossilized bacteria dating

from this period.

10. Why do the inner planets contain heavier elements while the outer

planets are primarily made up of lighter elements?

As the solar system was formed, the sun's gravity attracted heavier elements

and molecules inwards until balanced by increasing angular momentum. Once the

sun "ignited", radiation or "solar winds" pushed lighter particles further

away from the sun, while the strong gravitational pull between the heavier

planets and the sun minimized the effects of solar winds on these planets.

This leads to the pattern of our solar system that we see today, with the

heavier, denser planets found mostly within the inner portion of the solar

system, and the lighter, gaseous planets found further away from the sun.

11. Explain the transition of the earth's atmosphere from the origin

of the earth through the development of first photosynthetic organisms.

(Hint there are three!)

1). Asteroid bombardment: caused the earth to heat up and thus carbon was

released into atmosphere as carbon dioixde or carbon monoxide (also included

the addition of H2 and N2 to the atmosphere)

2). Comet bombardment: brought H20 and organic molecules into the earth's

atmosphere (also CH2, H20, NH3, HCN, CH3, CN, N2, ...)

3). Biological modification: oxygen dominated; as life was formed, organisms

consumed CO2 and released O2 (due to photosynthesis)

Note: the first two atmospheric environments were Reducing atmospheres, the

third was an Oxidizing atmosphere. Study Questions--Week 1--Answers