How many electrons are needed to complete the valence shell of the halogens?

Which of the following describes the muscular organ that processes food material into increasingly smaller pieces, mixes it with saliva to create a bolus, and creates a barrier to transport food into the esophagus?

Tongue.

The tongue is a muscle that plays a primary role in digestion and, in conjunction with teeth, prepares food for swallowing.

The process of organisms with an advantageous trait surviving more often and producing more offspring than organisms without the advantageous trait describes which of the following basic mechanisms of evolution?

Natural selection.

The mechanism of natural selection is rooted in the idea that there is variation in inherited traits among a population of organisms, and there is differential reproduction as a result.

A polar molecule always has ______.

A covalent bond.

Polar bonds occur when one atom in a covalently bonding molecule has more affinity for electrons than the other molecules.

What type of bones make up the wrist and the foot?

Short.

Short bones are present in the foot and the wrist.

During photosynthesis, which two compounds are combined to create the output of glucose and oxygen?

Carbon dioxide and water.

During photosynthesis, water and carbon dioxide are absorbed by the plant and converted to glucose and oxygen.

The number of protons is the same as?

The atomic number.

The number of protons in the nucleus of an atom is known as the atomic number, which determines the chemical element to which the atom belongs. All atoms of a given element are not necessarily identical. For example, elements may have isotopes, which are atoms of the same element with different numbers of neutrons. The number of possible isotopes is not connected to the number of protons in an atom. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number. The nuclear force is a force that acts between the protons and neutrons of atoms.

The identity of an element is determined by its number of ________.

Protons.

The number of protons determines which element it is.

A scientist designs an experiment to test the hypothesis that exposure to more sunlight will increase the growth rate of elodea, a type of aquatic plant. The scientist has accumulated data from previous experiments that identify the average growth rate of elodea exposed to natural sunlight in the wild.
In the experiment setup, there are three tanks housing ten elodea each. Tank A is positioned in front of a window to receive natural sunlight similar to what elodea are exposed to; tank B is positioned in front of the same window but has an additional sunlight-replicating lamp affixed to it; and tank C is positioned in a dark corner with no exposure to natural sunlight.
When setting up the above experiment, the scientist has the option of using a separate water filter for each of the three tanks or using a single filtration system that attaches to all three and affects them simultaneously. Which of the following filter setups makes a more valid experiment and why?

One filtration system for all three tanks, because this makes filtration a controlled variable.

Using one filtration system for all three tanks keeps the water quality across all three tanks constant and eliminates experimental bias for this variable.

Which of the following BEST explains how inhalation occurs in the human respiratory system?

The diaphragm contracts and lowers, making the air pressure in the lungs decrease.

During exhalation, the air pressure in the lungs must increase greater than atmospheric pressure, to force the air out of the lungs. To increase pleural pressure, the diaphragm relaxes and lifts. The reverse occurs during inhalation, whereby the diaphragm contracts and lowers itself, making the volume increase in the lungs, and pressure decrease in the lungs, therefore forcing air into the lungs.[Human Body Science]

Which of the following prefixes would likely be the most appropriate for measuring the weight of a 2,500 g kitten?

Kilo.

The purpose of scientific notations and prefixes is to avoid writing extremely long numbers. So, the correct answer to this question would be whichever option resulted in the smallest number of zeros. In kilograms, the mass of the kitten is 2.5 kg. If it was written as gigagrams, it would be 0.0000025 gigagrams, and in nanograms, it is 2,500,000,000,000 ng. In picograms, it would be 2,500,000,000,000,000. As you can see, kg results in the fewest digits, so it is the most appropriate prefix to use here.

What substance does a Schwann cell secrete that increases the speed of signals traveling to and from neurons?

Myelin.

Schwann cells secrete myelin, which forms a sheet around the neuron and allows the electrical signal to travel faster.

Within the nucleus, DNA is tightly wound around histones. How does this arrangement regulate gene transcription?

Enzymes are only able to reach regions of DNA where the chromatin has unwound.

Chromatin modification (or remodeling) allows for specific areas of DNA to unwind and become accessible to transcription enzymes. This process allows the cell to control which genes are available for transcription.

What is the term for the region of the body that lies below the ribcage and above the pelvis?

Abdomen.

The region of the body below the ribcage and above the pelvis is called the abdomen. The thorax, also known as the chest, is the part of the body within the ribcage. The peritoneum is a membrane that surrounds the abdominal cavity, but does not describe the entire region. Likewise the umbilicus, or navel, is located in the abdomen but is not descriptive of the whole area.

Which of the following chambers of the heart receives blood returning from the lungs during pulmonary circulation?

Left atrium.

The left atrium receives oxygenated blood, then moves it downward into the left ventricle.

How many electrons are needed to complete the valence shell of the halogens?

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