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Sati [7]
3 years ago
14

Which form of natural selection on polygenic traits results in the creation of two distinct phenotypes?

Biology
2 answers:
kupik [55]3 years ago
7 0
A. Directional selection.
vovikov84 [41]3 years ago
3 0
Directional selection is a natural selection on polygenic traits results in the creation of two distinct phenotypes.

- - Final answer: A
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Scientists once thought the most fundamental building block of matter was a particle called the atom. Now we know that the atom is made of many smaller pieces, known as subatomic particles. Every atom contains a central core called the nucleus, made of particles called protons and neutrons.

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One of your lab partners has followed the recommended procedure of running Gram-positive and Gram-negative control organisms on
andreyandreev [35.5K]

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Reduced in holding time of decolrization step and also used less Alcohol because decolrization step is important in Gram's staining.The decolorization step must be performed carefully. Otherwise over-decolorization may occur. This step is critical and must be timed correctly otherwise the CV stain will be removed from the Gram-positive cells. If the decolorizing agent is applied on the cell for too long time, the Gram-positive organisms to appear Gram-negative..

Explanation:

Gram' staining is a technique used in microbiology labs to differentiate between Gram's positive and negative

<u>Gram-positive bacteria :</u>Stain dark purple due to retaining the primary dye called CV in the cell wall.

<u>:Gram-negative bacteria </u>Stain red or pink due to retaining the counter staining dye called Safranin or neutral red.

There are four basic step in Gram" staining

1) Application of the Primary Stain to a Heat-Fixed Smear of Bacterial Culture

2)Addition of Gram's Iodine

3)<u>Decolorization with 95% Ethyl Alcohol:</u>Alcohol or acetone dissolves the lipid outer membrane of Gram-negative bacteria, thus leaving the peptidoglycan layer exposed and increases the porosity of the cell wall. The CV-I complex is then washed away from the thin peptidoglycan layer, leaving Gram-negative bacteria colorless.

On the other hand, alcohol has a dehydrating effect on the cell walls of Gram-positive bacteria that causes the pores of the cell wall to shrink. The CV-I complex gets tightly bound into the multi-layered, highly cross-linked Gram-positive cell wall thus staining the cells purple.

The decolorization step must be performed carefully. Otherwise over-decolorization may occur. This step is critical and must be timed correctly otherwise the CV stain will be removed from the Gram-positive cells. If the decolorizing agent is applied on the cell for too long time, the Gram-positive organisms to appear Gram-negative. Under-decolorization occurs when the alcohol is not left on long enough to wash out the CV-I complex from the Gram-negative cells, resulting in Gram-negative bacteria to appear Gram-positive.

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3 years ago
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Though mass extinctions are deadly events, they open up the planet for new forms of life to emerge. The most studied mass extinction, which marked the boundary between the Cretaceous and Paleogene periods about 66 million years ago, killed off the nonavian dinosaurs and made room for mammals and birds to rapidly diversify

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it took 17,000 years for CO2 to go from 200 to 300 ppm.

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