Which of the following valves prevents blood from going back to the left atrium?

The air in the atmosphere is a solution composed of 78.09% nitrogen (N), 20.95% oxygen (O), 0.93% argon (Ar), and 0.04% carbon dioxide (CO2) by volume. Which of these gases is the solvent?

Nitrogen (N2).

Nitrogen (N) is the largest component of the mixture and therefore is considered the solvent.

Which of the following statements is TRUE regarding trophic levels?

Tertiary consumers acquire less energy than primary consumers.

There is always a decrease in the amount of energy transferred from lower trophic levels to higher trophic levels. In general, the higher the trophic level of the consumer, the less overall available energy. Primary consumers have more energy available than both secondary and tertiary consumers.

1212A gene for eye color in humans has 3 alleles: , , for brown, blue, and green eyes, respectively. If an individual is , is she homozygous or heterozygous for eye color?

Heterozygous.

Alleles are pairs of genes on a chromosome that determine hereditary characteristics, such as eye color. You inherit one allele for each gene from each of your parents (this is the same with all organisms that reproduce via sexual reproduction).
In some cases, both parents provide the same allele of a given gene, and the offspring is referred to as homozygous (“homo” meaning “same”) for that allele. In other cases, each parent provides a different allele of a given gene, and the offspring is referred to as heterozygous (“hetero” meaning “different”) for that allele.
Since the individual in the problem has two different alleles, she is heterozygous.

In the chemical equation below, what are the products? 4NH3 + 5O2 -> 4NO + 6H20

NO, H20

In a chemical equation, reactants produce products (reactants -> products). NH3 and O2 are the reactants and NO and H2O are the products.

Which of the following organisms exhibits a high fitness?

A deer that has 90% viability of all offspring.

Fitness in biological terms refers to an organism's ability to produce viable offspring that are also able to reproduce in later generations. Organisms that have a low fitness can either be infertile or produce offspring that die before reaching reproducing age. Those organisms with a high fitness are considered to be better adapted to the environment.[Life Science]

A chemistry student is conducting an experiment in which she tests the relationship between reactant concentration and heat produced by a reaction. In her experiment, she alters the reactant concentration and measures heat produced. Which of the following is the independent variable in this experiment?

Reactant concentration.

The independent variable is deliberately changed in the course of the experiment.

The elements in Group 1 have ________ valence electron and are ________ reactive than the elements in Group 2.

One; more.

Group 1 elements contain one valence electron. They are more reactive than Group 2 elements because they have a full valence shell when they lose their one valence electron, meaning they lose that electron very easily.

Bone is composed primarily of which of the following inorganic materials?

Calcium.

Calcium is the most abundant mineral found in bones, as well as the entire body.

Consider a prokaryotic organism that typically lives in a 10 percent saline concentration environment. Which of the following environments would cause the organism to lose mass at the greatest rate due to osmosis?

Solution of 20 percent saline concentration.

Water will leave the cell through osmosis when the concentration of solute outside the cell is greater than that inside the cell. Water will leave the cell when it’s placed in a 20 percent solute solution, decreasing the mass of the cell.

Which of the following elements has the largest atomic radius?

Barium (Ba).

All elements are in group 2. Atomic radius increases from top to bottom within a specific group; since barium (Ba) is the element farthest down in the group, it will have the largest atomic radius.

Which of the following examples BEST illustrates the concept of carrying capacity?

A population of deer increases exponentially, but then decreases due to starvation, then increases slightly again.

The carrying capacity is the maximum population that can be sustained in a given area with a given amount of resources. When populations approach the carrying capacity, essential resources like water, food, space, and even mates become limited and organisms must compete more for these scarce resources. Often populations will decline below the carrying capacity when the resources become so scarce that individuals must die to decrease competition and increase the use of current resources.

Which of the following chambers of the heart pumps oxygenated blood to the rest of the body?

Left ventricle.

The left ventricle receives oxygenated blood from the left atrium, then pumps the blood to the rest of the body.

A lipid or fat molecule can be broken down into its monomers, one of which is _______.

Glycerol.

Glycerol and fatty acids are the monomers of lipid or fat molecules. Nucleic acid is not a monomer. It is a macromolecule formed of nucleotides. Glucose is a monomer of polysaccharides. Amino acid is a monomer of proteins.

Which of the following is a heterogeneous mixture?

Cereal in milk.

Cereal in milk is a heterogeneous mixture because the elements are not evenly distributed.

What is the oxidation state of the chlorine atom in HCl?

−1

Hydrogen (H) always has an oxidation number of +1. To create a neutral molecule, the chlorine (Cl) must then have an oxidation number of −1.

Which of the following valves prevents blood from going back to the left atrium?

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