Latest Version: 6.0

Question: 1

How did the Earth's early atmosphere become more oxygenated?

A. Respirating animals

B. Respirating detritus feeders

C. Volcanoes

D. Comets that contained a lot of ice

E. Photosynthetic organisms

Explanation:

Answer: E

Cyanobacteria were the earliest photosynthesizing organisms on Earth, filling the atmosphere with enough oxygen that aerobic organisms could evolve and eventually dominate anaerobes with their more efficient mechanisms.

Question: 2

What is the definition of a greenhouse gas?

A. Any gas that contributes to the warming of the Earth

B. Any gas that reflects radiation from the Earth's surface back toward the Earth

C. Carbon dioxide

D. Chlorofluorocarbons

E. Methane

Explanation:

Answer: B

Based on this definition, water vapor is the most abundant greenhouse gas because it provides an insulating layer that keeps heat trapped close to the Earth's surface. However, most conversations around this topic relate to chemicals that are increasingly contributing to the greenhouse gas effect: carbon dioxide, methane, fluorocarbons, and others. The concern is that these pollutants are increasing the effect of greenhouse gasses so significantly that the Earth is becoming permanently warmer.

Question: 3

The atomic number is:

I. The number of protons in the nucleus

II. The number of protons and neutrons in the nucleus

III. The net charge of the atom

IV. The characteristic by which elements are ordered on the periodic table

A. III and IV

B. II and IV

C. III only

D. I only

E. I and IV

Explanation:

Answer: E

The atomic number is defined as the number of protons in the nucleus. Since every element has a different number of protons, this is a logical way to organize elements on the periodic table. Although neutrons count in the atomic mass, they are not included in atomic number. Net charge is determined by the difference between the number of protons and electrons, can vary for any given element, and is unrelated to atomic number.

Question: 4

In the Hardy-Weinberg Law, p + q = 1, what do p and q represent?

A. Frequencies of dominant and recessive phenotypes

B. The likelihood of offspring being homozygous or heterozygous for a particular gene

C. Frequencies of the two alleles of a particular gene

D. Frequencies of homozygous and heterozygous phenotypes

E. Frequencies of homozygous dominant and homozygous recessive genotypes

Answer: C

Explanation:

We know this must sum to 1 because if there are only two alleles, their frequencies must sum to 100%. Though the equation is traditionally written with two variables (p and q), it is important to remember that a gene may have more than two possible alleles, in which case the equation would need to be expanded to encompass each allele option.

Question: 5

What key component(s) must be present for a species to change traits (evolve) over time?

A. Stable environmental conditions

B. Variation of traits within a species and competition/selective pressure

C. Competition and stable environmental conditions

D. Variation of traits within a species

E. Variation of traits within a species and differential reproduction

Answer: E

Explanation:

Without variation, there is nothing for natural selection to select. In other words, a species must have a few options for traits that might be helpful in the environment. Furthermore, those different trait options must lead to a difference in the success/frequency of reproduction. When the individuals with the "better" traits reproduce more often, the "better" alleles increase in frequency in the gene pool. This is how evolution occurs.

Note: It is true that competition must be present for natural selection to occur, but "competition" is implied in "differential reproduction" without competition, there would be no pressure to prevent certain individuals from producing less often than others. Also, evolution can and does occur in a changing environment.

Question: 6

Triglyceride is produced when which of the following molecules combine?

A. Three molecules of glycerol and one fatty acid

B. Two molecules of glycerol and two fatty acids

C. One glycerol, one fatty acid, and one water molecule

D. One glycerol, one fatty acid, and two water molecules

E. One glycerol and three fatty acids

Explanation:

Answer: E

This reaction involves dehydration or the release of three molecules. The product is a triglyceride, or fat, molecule that is high energy and can be stored densely.

Question: 7

Which of the following best defines a population?

A. The total number of all species that live within the given ecosystem

B. The total number of all species that interact with each other directly within the given ecosystem

C. The total number of one species that live within all ecosystems combined

D. Whatever meaning is specified in a given context the word does not have a rigorous definition

E. The total number of one species that live within the given ecosystem

Answer: E

Explanation:

Importantly, a population may not include all organisms of a species if that species is geographically spread out between different ecosystems.

Question: 8

Imagine that many molecules of a gas are placed into a box. That box is then connected with another box by a small tube so that a molecule can flow from one box to the other. Will the gas molecules stay in their box of origin or spread out to be equally distributed between the two boxes?

A. It depends on the type of gas and how attracted the molecules are to each other

B. Stay in the box of origin, according to the First Law of Thermodynamics

C. Spread out between the two boxes, according to the First Law of Thermodynamics

D. Stay in the box of origin, according to the Second Law of Thermodynamics

E. Spread out between the two boxes, according to the Second Law of Thermodynamics

Answer: E

Explanation:

The Second Law states that entropy, which can be thought of as "disorder," tends to increase in any system. The gas molecules will flow from clustered and organized in one box to more spread out and disorganized between the two boxes. It may also be helpful to think about entropy as the number of ways molecules or energy in a system can be arranged. There are more ways for molecules to be arranged if they are filling two boxes instead of just one.

Question: 9

In conifers, how does pollen travel?

A. Consumed by birds and excreted in a new location

B. Sticks to the legs of pollinators such as bees

C. Attaches to air sacs and borne by the wind

D. Pollen does not travel because conifers self-pollinate

E. Drifts freely in the wind

Explanation:

Answer: C

Remember that conifers, such as pines, are gymnosperms, so they do not produce flowers that can be aided by pollinators. Instead, pollen is attached to air sacs/bladders that easily drift in the wind. When the pollen's sperm unites with an egg cell, a zygote is formed that eventually matures into a seed.

Question: 10

When was the Cambrian period?

A. At the end of the Mesozoic Era, about 65 million years ago

B. At the beginning of the Paleozoic Era, about 570 million years ago

C. At the beginning of the Mesozoic Era, about 250 million years ago

D. At the end of the Paleozoic Era, about 250 million years ago

E. During the Proterozoic Era, about 2 billion years ago

Answer: B

Explanation:

The Cambrian period is remembered for the Cambrian explosion, in which there was an enormous radiation of differentiated animals. Few of these species exist today, thanks to the mass extinction events at the end of the Paleozoic Era.