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Agata [3.3K]
3 years ago
14

Why is a key bed used?

Biology
1 answer:
Anna11 [10]3 years ago
6 0
In geology, a key bed (syn marker bed) is a relatively thin layer of sedimentary rock that is readily recognized on the basis of either its distinct physical characteristics or fossil content and can be mapped over a very large geographic area.[1] As a result, a key bed is useful for correlating sequences of sedimentary rocks over a large area. Typically, key beds were created as the result of either instantaneous events or (geologically speaking) very short episodes of the widespread deposition of a specific types of sediment. As the result, key beds often can be used for both mapping and correlating sedimentary rocks and dating them. Volcanic ash beds ( and bentonite beds) and impact spherule beds, and specific megaturbidites are types of key beds created by instantaneous events. The widespread accumulation of distinctive sediments over a geologically short period of time have created key beds in the form of peat beds, coal beds, shell beds, marine bands, black  in cyclothems, and oil shales. A well-known example of a key bed is the global layer of iridium-rich impact ejecta that marks the Cretaceous–Paleogene boundary (K–T boundary). Please let me know if it works.
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A scientist is using a species of green algae to study the electron transport chain in photosynthesis. He uses a laser to inacti
jeka94

Answer:

D) In case 1, both PS I and PS II completely lose function; in case 2, a proton gradient is still produced.

Explanation:

The light dependent reaction of photosynthesis, which produces the ATP and NADPH needed in the light independent stage of the process, includes complexes of proteins and pigments called PHOTOSYSTEMS. These photosystems (I and II) are key to the functionality of the light dependent reactions in the thylakoid.

The major pigment present in both photosystems is CHLOROPHYLL A, which absorbs light energy and transfers electrons to the reaction center. Chlorophyll B is only an accessory pigment meaning it can be done without. Hence, if all of the chlorophyll A is inactivated in the algae but leaves chlorophyll B intact as in case 1, both PS I and PS II will lose their function because Chlorophyll A is the major pigment that absorbs light energy in both photosystems.

In case 2, if PS I is inhibited and PS II is unaffected, a PROTON GRADIENT WILL STILL BE PRODUCED because the splitting of water into protons (H+) and electrons (e-) occurs in PSII. Hence, H+ ions can still be pumped into the inner membrane of the thylakoid in order to build a proton gradient even without the occurrence of PS I.

3 0
3 years ago
What type of mutation has occurred in the dna of people with sickle cell anemia? (look back, if you need to, to see what causes
strojnjashka [21]
People with two copies of the sickle cell gene have the disease. People who carry only one copy of the sickle cell gene do not have the disease, but may pass the gene on to their children. Abnormal hemoglobin, called hemoglobin S, causes sickle cell disease (SCD). The problem in hemoglobin S is caused by a small defect in the gene that directs the production of the beta globin part of hemoglobin. This small defect in the beta globin gene causes a problem in the beta globin part of hemoglobin, changing the way that hemoglobin works.
5 0
3 years ago
Can someone please explain why food that has been kept at room temperature for a few hours is more likely to cause food poisonin
kenny6666 [7]

Answer:

Because food kept at room temperature is somewhat exposed to air, and sometimes, the air can contain dangerous chemicals that were perhaps accidentally released, whereas food in the refrigerator doesn't apply to that problem.

Explanation:

Hope this helps, and please mark as brainlest! :)

5 0
3 years ago
Read 2 more answers
Explain the reactions from
Sergio [31]

Explanation:

Glycolysis is the stage where glucose is broken down into 2 pyruvates (3 carbon compounds). This occurs in the cytoplasm and produces 2 ATP molecules. The pyruvates enters the mitochondria and enters the link reactions where it combines with co enzyme A (CoA). Decarboxylation ( removal of CO2) and dehydrogenation (removal of H) occurs here. Since CO2 is removed from the pyruvate it means a carbon is removed. This produces a 2 carbon compounds called acetyl. The acetyl compound is what combines with the CoA to form a compound called acetylCoA. This compound then enters the Krebs cycle.

The CoA co enzyme leaves and the acetyl reacts with a four carbon compound called oxaloacetate. This then forms a 6 carbon compound compound called citrate. A series of dehydrogenation and decarboxylation reactions occur to convert the 6 carbon compound back to oxalaoactate( the 4 carbon sugar). An ATP molecule is formed during one spin of the Krebs cycle.

The electron transport chain is where the reduced NAD (formed from dehydrogenation in glycolyisis, the link reactions and Krebs cycle) and Reduced FAD ( formed from dehydrogenation in the krebs cycle). molecules pass along a series of electrom carriers where they release energy that will be used to make ATP. Oxygen is the last electron carriers

I tried to sum it up as best as possible. If you want in detail explanations of each then I can explain it also.

6 0
3 years ago
History: When did stem cell research become known? Who discovered stem cells? What experiments or studies have been conducted so
avanturin [10]

Answer:

The stem cells was discovered by Ernest McCulloch and James Till in 1981. Studies conducted for stem cells can be used for bone marrow transplantation and to treat various diseases.

Explanation:

Stem cell are the cells that has the ability to differentiate into different cells of the body. In 1978 human cord blood discovered as stem cell. The stem cell research come to known in 1981.

Ernest McCulloch and James Till discovered the stem cell research while working on the mice bone marrow. He found that the different blood cells were formed by the single class of cells.

Experiments on mice and other animals have been conducted to study the stem cells so far. The study of stem cell is useful to cure the genetic defects, Cancer and other harmful diseases.

3 0
3 years ago
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