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Alex73 [517]
3 years ago
6

I need help from 20-23

Biology
1 answer:
Mashcka [7]3 years ago
3 0
20. The answer is 1 (Precambrian)
21. The answer is 4 (Pennsylvanian)
22. The answer is 2 (Bony Fishes, Dinosaurs, and Mammals)
23. The answer is 2 (Reptiles)
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this is just evolution like the birds on the Galapagos islands also I don't see the question

4 0
2 years ago
A gel electrophoresis is performed, but when the gel imager is used, no bands appear. the researcher might have forgotten to: (c
Sladkaya [172]
The answer is;

a. add electric current.
b. add buffer solution

The process of gel electrophoresis taps on the property of net charges of molecules to ensure that they travel up the gel. Additionally, the buffer acts as the mobile phase for the molecules and also give molecules net charge as they travel through the gel. It is until the molecules reaches an isoelectric point,where the molecule has zero net charge, that they stops moving through the gel. This is how bands are formed.
7 0
3 years ago
About half of all babies are able to walk independently by __________ months of age.
Liono4ka [1.6K]
I think that about half of all babies are able to walk independently by 12 month of age. It said that babies tend to take their first steps from the age of 9. Babies usually start to crawl before they can walk. This is because their arm are usually more effective. After crawling they learn to stand up with their feet first and later learn to walk while holding things. The next step after that is walking. 
Not all babies walk at the same time. There those that learn before the other so there is no need to worry if your child does not walk by 12 months.
7 0
2 years ago
The functional and structural unit of the kidneys is the:_______.
serg [7]

Answer: c. nephron

Explanation: The nephron is the functional unit of the kidney, which actively filters blood and generates urine. The nephron is made of the renal corpuscle and renal tubule. Cortical nephrons are located within the renal cortex, whilst juxtamedullary nephrons are observed inside the renal cortex near the renal medulla.

3 0
3 years ago
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