BIOLOGY HIGH SCHOOL

Which of the following best describes half-life?a. Half the time it takes for all of the nuclei in a sample of a radioactive isotope to decay.
b. The time it takes for the nucleus of one atom of a radioactive isotope to split in half.
c. The time it takes for half of the nuclei in a sample of a radioactive isotope to decay.
d. The time it takes for the nucleus of one atom of a radioactive isotope to decay.

Answers

Answer 1
Answer:

The time it takes for the nucleus of one atom of a radioactive isotope to split in half is half life.

  • The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.

What is radioactive isotope?

  • An unstable form of a chemical element that releases radiation as it breaks down and becomes more stable.
  • Radioisotopes may occur in nature or be made in a laboratory. In medicine, they are used in imaging tests and in treatment.
  • These are also called radionuclide.

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Answer 2
Answer: I think b, because it’s the time that the isotope takes to fall to half of its original value

Related Questions

Adaptive melanism describes selection for
In a magazine advertisement, a manufacturer claims its laundry ball, which contains ceramic pellets, gets clothes clean by changing the pH of the water. The ad claims the product reduces wear on their clothing, contaminants in the environment, and the cost of doing laundry. What should the advertisement include to give a consumer more confidence in this product's claims?
A student conducted an experiment to test the effect of the digestive enzyme pepsin on cooked egg white and potato in the presence of hydrochloric acid at a pH of 1. Which could be a probable inference?Pepsin digests egg white because it mainly contains protein. Pepsin digests potato because it mainly contains starch. Pepsin digests egg white because it mainly contains fat.
A plant with the dominant trait, wrinkled seeds, is crossed with a plant that has non-wrinkled seeds. All of the offspring are all wrinkled-seeded. What is the likelihood that the gametes of the wrinkled-seeded parent plant contain one non-wrinkled allele?
Which would least likely result from a chromosomal change?a.death of the cell or organism b.no effect on the cell or organismc.enhanced ability of the organism to reproduce d.change to the phenotype of the organism

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? a. breaking down ATP, so that ADP and P can be reused; b. transforming the energy in glucose and related molecules in a chemical form that cells can use for work; c. producing complex molecules from chemical building blocks; d. the breakdown of glucose to carbon dioxide and water; e. catabolism of sugars and related compounds

Answers

transforming the energy in glucose and related molecules in a chemical form that cells can use for work best describes the main purpose of the combined processes of glycolysis and cellular respiration .Thus option B is correct.

What is Cellular Respiration?

A metabolic process in which a series of steps occur to convert chemical energy (sugar) into  ATP in the cell.

The first stage is glycolysis, which breaks the glucose molecule into two smaller molecules called pyruvate, and releases small amount of ATP energy and it is oxygen independent.

second stage where reorganization of pyruvate molecules and fused over again in a cycle, carbon dioxide is formed and electrons are removed.

These electrons placed in an electron transport system release ATP for the plant to use for growth and reproduction and this process is oxygen dependent.

Thus option B is correct.

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b. they make ATP from glucose molecules and use when necessary

In natural ecosystems, the presence of predators lessens the effects of _________________ among the prey.. .

Answers

The answer is competition. 

Competition is an interaction between organisms. If resources, such as food, water, sunlight, territory, are limited and several species depend on these resources, then, they must compete with other species to gain the resources. So, if predators are present, this means that they will maintain the size of prey population on some optimal level. With fewer individuals in the population, there will be less competition for resources.
Therefore, In natural ecosystems, the presence of predators lessens the effects of competition among the prey.

Answer: is competition

Explanation:

Because i had this question on USA test prep

Mr. Rojas was looking through a microscope at some similar cells. He noticed that every cell had a different structure. What can he infer about these cells? * They are from different organisms. They have the same organelles. They have the same functions. They have different functions.

Answers

Answer:

They have different functions.

Explanation:

The cells having different structures may come from the same organism and having different structures may result from having different organelles. Due to the structure function correlation in cells, it is thus likely that the different structures arise from different functions, hence cells are specialised structurally to optimise performance in their functions.

The understanding of evolutionary processes has helped scientists in the field of artificial selection. The best example of artificial selection is

Answers

The conservation of bald eagles is not a description of selective breeding, but it could be. For now we can cross that off.
Geographical distribution is a geographical factor of Natural selection, so it can't be B either.
Pesticide-resistant potatoes are altered to be resistant to pesticides (pesticides wouldn't affect plants anyway as they are meant to kill insects)
The answer is D. The collection and reseeding of the largest pumpkins is the best answer.

Answer:

the answer is C: the production of pesticide-resistant potatoes.

Explanation:

just took the test

If yellow,red and orange pigments exist in the leaves of trees,why are leaves green except for in the autumn?A) Chlorophyll is the most abundant off all the pigments.
B) Chlorophyll molecules are the largest of the all pigment molecules.
C) Chlorophyll reproduces faster than the other pigments.
D) Green is the color of the spectrum most easily seen by humans.

Answers

If yellow, red, and orange pigments exist in the leaves of trees. The leaves appear green except for the autumn because the chlorophyll is the most abundant of all the pigments present. Thus, the correct option is A.

What is Chlorophyll?

Chlorophyll is a pigment which is present in all the green plants and in a  few other organisms such as algae. It is required for the process of photosynthesis, by which light energy is converted into chemical energy in the plants. The chlorophyll pigment is responsible for the green coloration in plants.

However in the autumn, because of changes in the length of daylight and temperature, the leaves stop the food-making process. The chlorophyll pigment breaks down, the green color disappears from the leaf, and yellow to orange colors become visible in the leaves and give the leaves part of their fall splendor.

Therefore, the correct option is A.

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The answer is A) chlorophyll is the most abundant off all the pigments.

A scientist is studying the gaseous layer of Earth. The focus of his/her study is on the _____.biosphere
hydrosphere
atmosphere
cryosphere

Answers

Answer: atmosphere

Explanation:

The atmosphere is the gaseous layer of the earth. It consists of mass of gaseous which are collectively called as air. In the air the particles such as dust particles, smoke, soot and chemicals are present. These are attracted by the gravitational pull of the planet. The atmosphere protects the earth from the entry of harmful UV and infrared radiations coming directly from the sun. This way atmosphere protects the living beings from damage caused by these radiations.

On the basis of the above description, atmosphere should be the focus of study.

armospehere he is studing the atmosphere
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