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KATRIN_1 [288]
1 year ago
8

Which describes oxygen content as Earth evolved over time? Oxygen levels sharply declined about 400 million years ago. Oxygen le

vels stay above 15 percent starting 200 million years ago Oxygen levels remain below 5 percent starting 1000 million years ago. Oxygen levels raise significantly between 1000 and 700 million years ago.
Biology
2 answers:
lora16 [44]1 year ago
5 0

Answer:

b

Explanation:

tankabanditka [31]1 year ago
4 0

the correct answer is b. i just took the quiz

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In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only on
devlian [24]

Answer:

The correct answer is option A, that is, cotransport proteins.

Explanation:

The variable that possesses the tendency to mediate energy based on chemical potential is termed as an electrochemical gradient. The electrochemical gradient is differentiated into two parts, that is, electrical gradient and chemical gradient. Both these forms of gradient take place over the surface of a membrane.  

The movement of the majority of the ions takes place by the phenomenon of electrochemical gradients, of which some are found on the surface of the membrane and function as electrogenic pumps. While the gradients of some of the ions are mostly accounted for by the co-transport proteins, as these proteins take part in the movement of ions or molecules through a plasma membrane that involves concentration gradient based on the kind of molecules and movement.  

5 0
1 year ago
The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed three- chambered hea
Arisa [49]

Answer:

The four- chambered hearts of birds and mammals are best described as <u>homoplasies.</u>

Explanation:

In evolution, homoplasies are the trait shared in different species despite that their ancestors didn't have it at all.  In other words, these are traits that can be gained or lost during evolution in different lineages independently. For example, wings of birds and wings of bats do the same function (help in flying) but they were not there in the ancestors so both animals developed these structures independently.

In the given example, birds and mammals have four-chambered heart but their ancestors have 3 chamber hearts. They evolved independently and developed 4 chamber heart. This might be due to several reasons. However, their ancestors didn't have the feature so it is an example of homoplasy.

5 0
1 year ago
Read 2 more answers
Match each phylum or class to its correct characteristic.
Elis [28]

Answer:

Which quotations from "The Crab That Played with the Sea" convey a comic tone? Select two options.

"O my Best Beloved"

"He took the Elephant—All-the-Elephant-there-was—and said, 'Play at being an Elephant.'"

"All-the-Cow-there-was . . . licked her tongue round a whole forest at a time."

"The great Sea . . . overflowed all the dark forests for miles and miles, and flooded the Man’s house."

"By and by the Eldest Magician met the Man on the banks of the Perak river."

Explanation:

sp yes

5 0
2 years ago
A student half a jar with rice and tightens the jars lid. The student wants to use the jar of rice to model particle motion of a
Sindrei [870]

Answer:

because the jar is see through so it allows you to watch the motion

Explanation:

7 0
1 year ago
Researchers further hypothesized that if predation pressure is reduced, drab coloration would become less beneficial (since fema
s2008m [1.1K]

Answer:

The predation pressure increases mate

Explanation:

Since the observation of the scientist goes in order to increase the coloration in males, because of the predation pressure, and as a consequence the females are attracted by this colored mates.

It will be expected that the increase in pressure, it will increase the colored in skin, and this could end in an increase of the number of mates per male.

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1 year ago
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