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Vilka [71]
3 years ago
7

Why is the SA node called the pacemaker of the heart?

Biology
1 answer:
defon3 years ago
6 0
It sends electrical impulses that cause the muscles of the heart to contract. It literally sets the rate of contractions, or in other words it controls the pace
You might be interested in
Ferns often have small bumps called sori arranged in rows on their undersides. What are these structures?A) Spore capsules.
leva [86]

Answer:

A) Spore capsules

Explanation:

Ferns produce spore capsules contained in the sporangium (plural: sporangia), a structure localized on the undersides of the leaves. Moreover, the sporangia are borne in clusters known as sori (singular sorus). The spores are single reproductive cells that, when mature, are released from the sporangium to germinate on soil and produce new ferns. In a fern sporangium, the maximum number of spores is 64, although this number depends on the species.

6 0
3 years ago
Blood from the lungs is carried back to the heart by the _____.
leonid [27]
<span>Pulmonary vein

Pulmonary circulation is the movement of blood starting from the heart, where deoxygenated, or carbon dioxide-filled, blood leaves from the right ventricle and through the pulmonary valve, then into the left and right pulmonary arteries and arrives at the lungs. During the process of respiration, the carbon dioxide is released and oxygen is added to the blood. </span>
3 0
3 years ago
Consider two different traits in mice affecting tail length and fur color. A two-factor cross was made involving true-breeding m
Stells [14]

Answer:

See the answer below

Explanation:

Null hypothesis: The two genes are independently assorting and therefore, are not linked to each other.

Let A represents the allele for tail length and B for fur color. Long-tail A is dominant over short tail a while brown fur B is dominant over white fur b.

For the first cross involving true-breeding mice:

    AABB   x   aabb

F1         AaBb (long tails and brown fur)

For the second cross:

      AaBb   x   aabb

4 AaBb - Long-tail, brown fur

4 Aabb - Long tail, white fur

4 aaBb - short tail, brown fur

4 aabb - short tail, white fur

Since the phenotypic ratio from the cross is 1:1:1:1, if the null hypothesis was to be true, it means that the expected phenotype ratio should be 1:1:1:1.

In order to test this hypothesis, we use Chi-square:

phenotype                           O            E                 X^2  

Long-tail, brown fur           118          97.5        \frac{(118-97.5)^2}{97.5} = 4.31

Long tail, white fur              77           97.5             4.31

short tail, brown fur             81           97.5              2.79

short tail, white fur              114           97.5              2.79

Total                                                                          14.2

Degree of freedom = 4 - 1 = 3

Critical Chi-square value = 7.815

The calculated Chi-square value is more than the critical value, hence, the null hypothesis is rejected.

8 0
3 years ago
In 2010, an area in the Gulf of Mexico was the site of the worst oil spill in United States history. The Deepwater Horizon oil r
iren2701 [21]
Answer: c) biologists would track the number of species and their relative abundance in the gulf coast region in 2009, 2010, and 2011
3 0
3 years ago
Which stamens correctly describe the rock cycle
lions [1.4K]

B, C, and D are the answers I think

3 0
3 years ago
Read 2 more answers
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