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3 years ago

What major event most likely spurred mammal diversification?

1 answer:

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The answer is a mass extinction of the dinosaurs.

65 million years ago the mass extinction of the dinosaurs spurred mammal diversification. Before that, dinosaurs were big reptiles living on the Earth. They occupied many ecological niches. But, after the extinction, they made room for other animals, such as mammals, to evolve and rapidly diversify.

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Which of these correctly distinguishes mitosis from meiosis?

Dafna11 [192]

Meiosis is the cell division needed to reproduce sexually, it produces the egg and sperm cells, which need to have half the amount of chromosomes, so that when they combine, they have the usual 46 chromosomes. All the other division, which produces identical cells of 46 chromosomes is called mitosis.

So the correct answer is:

<span>D)The number of chromosomes remains the same in mitosis and is reduced by half in meiosis.</span>

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2 years ago

Read 2 more answers

Which of the following statements about manual Sanger sequencing is true? View Available Hint(s) Which of the following statemen

Fed [463]

Answer:

One sequencing reaction is performed

Explanation:

The manual Sanger sequencing technique is based on the termination of DNA synthesis by the addition of a ddNTP, which impairs the full elongation of the molecule. Originally, you would perform four parallel reaction, one for each type of ddNTP (A, G, T, C). So in each reaction you would get sequences of different lengths, all finished with the ddNTP you added in that tube.

By running an electrophoresis for nucleotides, using a gel with enough resolution to separate the sequences by on base pair (bp). If you run each of the reaction mixture in a different rail, you should get fragments of the lengths corresponding to all the positions the nucleotide you added as a ddNTP occupy in the sequence.

Also, as the fragments are separated based on their molecular weight, so smaller ones migrate further in the gel. That means the gel should be read from bottom to top (note that the smaller fragments were terminated earlier than the larger ones).

For example, if in the rail of ddATP, you get a fragment of four bp, that means the fourth nucleotide of the sequence it's an A.

Per each reaction, only one sequence can be sequenced, otherwise it would be impossible to know which fragments correspond to the different sequences.

This method doesn't need any kind of dye to be used on the different ddNTPs as long as they are added in separate reactions.

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3 years ago

Research how the body uses feedback mechanism to decrease the heart rate after exercise. what specifically happens in the body t

maw [93]

<span>A negative feedback loop works by adjusting an output, such as heart rate, in response to a change in input, such as blood pressure. A basic loop consists of a receptor, a control center and an effector. If you are at rest and your blood pressure increases, pressure receptors in your carotid arteries detect this change in input and send nerve impulses to the medulla of your brain, or control center. This signals the brain to reduce nerve impulses that stimulate your heart muscle, an effector, to contract. Your heart contracts more slowly and your output, or heart rate decreases, causing your blood pressure to decrease to within target levels.</span>

6 0

3 years ago

Why doesn't Wyoming doesn't experience midnight sun?

Leokris [45]

Midnight Sun, a name given the sun when it can be seen at midnight during the Arctic or Antarctic summer.The midnight sun occurs because the earth's axis tilts toward the sun in summer and away from the sun in winter. Thus the poles are exposed to the sun's rays for six months each. As our planet makes its annual circuit around the sun, parts of the globe experience dramatic seasonal swings thanks to the tilt of Earth’s axis. Between April and September, the northern hemisphere is tipped toward the sun, resulting in longer days and warmer weather. Destinations near and north of the Arctic Circle experience the astronomical phenomenon.

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3 years ago

In a particular environment there is plenty of food, water, cover, and space to support a large population of pheasants, but a l

FromTheMoon [43]

Answer:

c. limiting factor.

Explanation:

The limiting factors are environmental or ecological factors that act directly on the living beings of a population, limiting their size, since these factors determine their birth, mortality, migrations, etc. They are the ones that regulate the growth and expansion of a species.

If environmental factors are optimal for the development of a living being, they favor the growth of that organism in that biotope. But if any of these factors prevents the growth of a species, there is talk of a limiting factor.

Among these physical and chemical factors that determine the biotope include:

- Abiotic factors (do not depend on population density):

Climate:

Light. Only the most superficial organisms access it in water. On land, there is also competition in leafy areas to access it.

Temperature. Some living beings cannot live at the temperature that others live.

Water: It is necessary that it rains or that living beings can access water in order to live. If there is no water, they die.

Atmospheric pressure.

Non-climatic:

Soil factors: The chemical composition of the soil, its pH, salinity, etc. It makes some plant species may or may not survive in it.

Factors of the aquatic environment: The concentration of O2, dissolved CO2, the degree of salinity, the existence of currents, etc., limits the development of some organisms.

- Biotic factors (depend on population density):

Food. If they do not have enough food, the population will have to be smaller.

Interspecific relationships. The number of predators limits the number of prey, and vice versa.

Intraspecific relationships. The relationships established between individuals of the same species can also limit their existence.

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3 years ago