Mechanical weathering may occur by means of _____?

Which planet revolves around the sun in an orbit between that of Venus and Mars. It is known to be covered by oceans and some land, and it has but a single moon.

Tides result from the pull of gravity exerted upon the earth by _____?

Scientists performed an experiment to determine whether there is a connection between learning ability and food. They took two groups of 20 mice each, all from the same purebred strain. The mice were deprived of food for 3 days and then given a standard learning session in running through a maze. They were trained by giving them a mild electric shock whenever they took a wrong turn. Immediately after each learning session, one group of mice was fed, but the other was not, A week later, all of the mice were tested to see whether they could still run the maze correctly. The group that had been fed had retained this ability, but the other group had not.

The probable reason that the scientists used only mice from the same pure-bred strain is so that?

PASSAGE: H2O + CO2 = H2CO3

In the equation above, how many atoms of oxygen are participating in the reaction?

A fluid can exert a buoyant force as well as an internal force because of the weight of the fluid above it. The suit of a deep-sea diver must contain a jacket of compressed, pressurized air that counteracts the external water pressure. The reason for the jacket of compressed air is _____?

Electric current in metals is carried by free electrons, while the positively charged nuclei remain at rest. In aqueous solutions, positive and negative ions moving in opposite directions carry current. Opposite charges moving in the same direction result in no current. Which of the following best describes all the features of electric current?

Solar collectors provide energy for buildings by pumping water through panels mounted on the roof. The water picks up heat from the sun, and the pump is controlled by a sensor so it operates when the collector is several degrees hotter than the water in the storage tank. This type of energy would work best in?

The absorption of optical fiber used to carry data and voice in telecommunications networks. Fibers with less absorption are desired because they can carry signals farther before they need to be amplified. The distance between amplifiers is inversely proportional to the absorption coefficient, which means that if the absorption is doubled, the distance is halved. While lower-absorption fiber is generally more expensive, the higher cost of the fiber is more than compensated for by the lower total cost of amplifiers. What is the significance of absorption for optical communication?

The key to understanding the molecular basis of heredity is understanding how the DNA molecule is passed on to the next generation. This involves meiosis, a special type of cell division that occurs only in the formation of reproductive cells, such as the sperm and egg in humans. All human somatic cells (nonreproductive cells) contain 22 pairs of chromosomes plus a 23rd pair (XY) that determines sex. Reproductive cells called gametes, or sperm and egg, contain one-half the number of chromosomes. In the case of humans, this is 22 individual chromosomes, plus one sex chromosome.

In order to produce sex cells with one-half the normal number of chromosomes, several additional steps in cell division are necessary. Recall that in mitosis, during interphase, DNA replicates itself (makes an exact copy of itself). It does this by unzipping along the hydrogen bonds. Each half of the DNA molecule makes a new strand using free nucleotides in the nucleus. This provides enough DNA for the daughter cells after meiosis. Each chromosome remains attached to its exact copy until Metaphase II, as is illustrated below. Where does meiosis occur?