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Morgarella [4.7K]
2 years ago
11

Scientists infer that oxygen first began to enter Earth's atmosphere after the appearance of

Biology
1 answer:
GenaCL600 [577]2 years ago
8 0

Oxygen entered the Earth's atmosphere after the appearance of the Great Oxidation Event (Great Oxygenation Event). The Great Oxidation is the first mass extinction on Earth.

The Great Oxidation lasted 2.4 to 2.0 billion years ago.

Oxygen appeared on Earth thanks to cyanobacteria using photosynthesis.

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Which is required for sexual reproduction?
m_a_m_a [10]

Answer:

Meiosis

Explanation:

Haploid number of chromosomes

8 0
3 years ago
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PLEASE HELP ME THIS IS PART 2!!!!!!!!! I WILL MARK BRAINLIEST
steposvetlana [31]

Answer:

D

Explanation:

6 0
3 years ago
1.
Hitman42 [59]

Steps to improve food safety in commercial food preparation units like restaurants .

  1. Wash and sanitize hands to begin food preparation
  2. Clean & sanitize the prep sink or the 3-comparment sink
  3. Remove smallwares & dishes from the preparation area
  4. Set up equipment for food preparation

Explanation:

Food contamination is the major source for foodborne infections and illnesses

Ensuring safe food preparation, cooking and storage practices are prime importance for any commercial food preparation unit like restaurants, hotels, etc

The standardized procedures while cleaning, separating, cooking and storing food should be followed.

Cleaning processes first include personal cleaning as well as cleaning the preparation.

Personal cleaning includes washing and sanitizing the hands periodically before, during and after food preparation and after any other activities like using the toilet, baby dressing, touching garbage etc

Cleaning the preparation area including the 3-compartmental sink for washing, rinsing and the sanitizing

Separating the utensils as per cooking methods and dishes like using separate cutting knives or boards for raw and cooked meat, poultry or fish products

Cooking the food at a right temperature depending upon the type of cooking

Storing or chilling processes appropriately according to the food type under appropriate temperature should be followed.

5 0
3 years ago
Why do you think adult male crabs have such a large claw? What could be the purpose of it? And can you think of any other animal
Romashka [77]

Answer:

cause they use the small one for feeding and the large one to attract a female crab for mating, the large claws are also used as a weapon

3 0
3 years ago
Action potentials (nerve impulses) are changes in the membrane potential that, once started, will affect the entire excitable me
stich3 [128]

Answer:

The order of events would be:

4.Threshold stimulus, Na+ channels open.  This is the first event

5.Na+ influx, Depolarization. Second event

2.Na+ channels close, K+ channels open.  This is the third event

1.K+ efflux, Repolarization.  Fourth event

3.Hyperpolarization, K+ channels close

Explanation:

In resting state, the membrane is negative inside, and  K+ concentration is higher than outside.   Na+ concentration is higher outside instead.  

Sodium influx is responsible for membrane depolarization.  It's the event to produce the action potential.  When sodium channels are closing, potassium channels open and K+ go outside until repolarization occurs. But now we have both ions in different sides of the membrane, and this can't be stimulated again to produce other action potential. The membrane will remain refractory to respond to the adequate stimulus until ions migrate to their original sites.  This is Na+ outside, and K+ inside.  This is responsibility of the Na+/ K+ pump, that uses ATP to pump Na+ out, and  K+ in. Once both ions had been relocated in the membrane, this is ready to receive a correct stimulus to produce a new action potential.

6 0
3 years ago
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