Question

QUESTION 21

1. Oxygen did not become abundant in the atmosphere until approximately __________ million years after the evolution of photosynthesis because __________

		10; of oxidation of abundant hydrogen in the atmosphere
		10; photosynthetic organisms were originally restricted to deep sea vents
		500; of oxidation of abundant hydrogen in the atmosphere
		500; photosynthetic organisms were originally restricted to deep sea vents

0.6 points   

QUESTION 22

1. Regarding plant growth and soil water, if an increase in soil water causes a decrease in plant growth, and if that decrease in plant growth causes an increase in soil water, then the system is _________ (Suggestion: draw a systems diagram of this to help figure out the answer)

		a positive feedback loop
		a negative feedback loop
		state-resolved
		variable-resolved

0.6 points   

QUESTION 23

1. The Earth emits __________ than the Sun.

		more total energy and shorter wavelength radiation
		more total energy and longer wavelength radiation
		less total energy and shorter wavelength radiation
		less total energy and longer wavelength radiation

0.6 points   

QUESTION 24

1. The Keeling Curve shows that the atmospheric concentration of carbon dioxide is currently increasing at a rate of about __________ ppm per year.

		0.02
		0.2
		2
		20

0.6 points   

QUESTION 25

1. The Miller-Urey experiment tested whether or not _________

		DNA could form from simple organic molecules
		The base molecules of DNA can combine in the surface water of oceans
		Meteorites contain organic carbon
		Complex organic molecules can easily form from simple organic and inorganic molecules

Answer 1

21) 500, Photosynthetic organisms restricted to deep sea vents.These photosynthetic organisms released O₂ but the O₂ was largely taken up by banded iron formations in the sea.After these formations became saturated with O₂ no more oxygen was taken and oxygen was now available for life to grow further.

22) The system is a negative feedback loop because in this process the response of one action causes a decrease in other and in this case it is plant growth.Hence, the feedback loop in this case is negative.If there was an increase in the plant growth due to an increase in soil water the feedback loop would have been positive.

3) Less total energy and longer wavelength radiation.The earth emits less energy because some of the incoming energy is absorbed by earth features and because it has less energy it emits longer wavelength radiation as smaller wavelength radiation have more energy in them.

4) The keeling curve shows that the current atmospheric concentration of CO₂ is increasing at 2 ppm.

5) Complex organic molecules can easily form from simple organic and inorganic molecules.Milley and Urey conducted the experiment in 1950s and the experiment proved that many different organic molecules could be formed by the conditions present in earths atmosphere from the early times when life originated.