Answer:
Oxygen makes up about one-fifth the volume of Earth's atmosphere today, and is a central element of life as we know it.
But that wasn't always the case. Oxygen, although always present in compounds in Earth's interior, atmosphere, and oceans, did not begin to accumulate in the atmosphere as oxygen gas (O2) until well into the planet's history. What the atmosphere was like prior to oxygen's rise is a puzzle that Earth scientists have only begun to piece together.
Earth coalesced a little more than 4.5 billion years ago from bits of cosmic debris. Liquid oceans existed on the planet almost from the beginning, although in all likelihood they were repeatedly vaporized by the massive meteorites that regularly clobbered the planet during its first 700 million years of existence. Things had settled down by 3.8 billion years ago, when the first rocks that formed under water appear in the geologic record. (They exist in what is now southwest Greenland.)
If Earth had water, it must have had an atmosphere, and if it had an atmosphere, it must have had a climate. What was Earth's early atmosphere made of? Nitrogen (N2), certainly. Nitrogen makes up the bulk of today's atmosphere and likely has been around since the beginning. Water vapor (H2O), probably from volcanic emissions. Carbon dioxide (CO2), also emitted by volcanic eruptions, which were plentiful at that time. And methane (CH4), generated inside the Earth and possibly also by methane-producing microbes that thrived on and in the seafloor, as they do today.
Carbon dioxide, water vapor, and methane played an important role in Earth's subsequent development. Four billion years ago, the Sun was 30 percent dimmer, and therefore colder, than it is today. Under such conditions, Earth's water should have been frozen, yet clearly it wasn't. The water vapor, carbon dioxide, and methane acted as greenhouse gases, trapping heat and insulating the early Earth during a critical period in its development.
Of oxygen, meanwhile, the early atmosphere held barely a trace. What did exist likely formed when solar radiation split airborne molecules of water (H2O) into hydrogen (H2) and oxygen (O2). Hydrogen, a lightweight gas, would have risen above the atmosphere and slowly been lost to space. The heavier oxygen gas, left behind, would have quickly reacted with atmospheric gases such as methane or with minerals on Earth's surface and been drawn out of the atmosphere and back into the crust and mantle. Oxygen could only begin to accumulate in the atmosphere if it was being produced faster than it was being removed'—in other words, if something else was also producing it.
That something was life. Although the fossil evidence is sketchy, methane-producing microbes may have inhabited Earth as long ago as 3.8 billion years. By 2.7 billion years ago, a new kind of life had established itself: photosynthetic microbes called cyanobacteria, which were capable of using the Sun's energy to convert carbon dioxide and water into food with oxygen gas as a waste product. They lived in shallow seas, protected from full exposure to the Sun's harmful radiation. (To learn more about these organisms and the fossil evidence for them, watch the accompanying video "Early Fossil Life.")
The time it takes for an animal to metabolize a drug to a non-detectable levels could be ____ than that of the withdrawal period 
A:Longer
B:Shorter
C:Same time
The time it takes for an animal to metabolize a drug to a non-detectable levels could belongerthan that of the withdrawal period. Hence the correct option is A.
The metabolism of a drug refers to the process by which the body breaks down and eliminates the drug from the system. The withdrawal period is the time required after administering a drug during which the animal must not be slaughtered for human consumption to ensure that no residues of the drug are present in the edible tissues.
There are several factors that can influence the metabolism of a drug in animals, such as the drug's chemical properties, the animal's species, age, health status, and metabolic rate. Some drugs may be metabolized relatively quickly, while others may take longer to be completely eliminated from the system.
Hence the correct option is A.
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Which of these are MOST involved in exchanging gases?
1 point
heart
bladder
lungs
pituitary gland
lymph nodes
the diagram below represents a portion of a cell membrane. The arrow indicates that the cell membrane is carrying out the process of...
Answer:
In the portion of the cell membrane shown in the diagram, the arrow indicates the process of active transport.
Explanation:
Active transport is one of the mechanisms of transmembrane transport, which involves the use of energy. The diagram (see image) shows the hydrogen (H⁺) output from the cytoplasm to the extracellular space, through an H⁺ pump —consuming ATP— which represents an active transport process.
The hydrophobic nature of the cell membrane prevents the free passage of hydrosoluble elements or ions, as H⁺, so they require the use of active transport to pass through it.
The other options presented are not correct, because
Respiration is a process that occurs in the mitochondria.Diffusion is a passive transport process that does not require energy.Cellular recognition depends on membrane proteins that act as specific receptors.
Which of the following happens as part of both the lytic cycle and the
lysogenic cycle?
new viruses are made
O the host cell dies
O the entire virus infects the cell
O the virus injects its nucleic acid into the host cell
Answer:
vnmvm
Explanation:
how to do this question
i)iodine
ii)A,B,D= no colour change and c is turned black
B and D will have no colour changes they don't have starch
What is a habitat?
A) an area of land
B) a community
C) a niche
D) a population
Answer:
the answer is a niche
Explanation:
Please help me
Important Ions move from low to high concentration while using a membrane protein. Which of the following is true? Question 5 options:
A. It's moving down the concentration gradient.
B. Energy is needed to make this happen
C. It's facilitated diffusion.
D. It's osmosis.
Answer:
A) it is moving down the concentration gradient
Explanation:
Brownian motion will cause the molecules (or ions) to spread/diffuse from where they are more concentrated to where they are less concentrated until they are equally distributed in that space (Figure). When molecules move in this way, they are said to move down their concentration gradient.
Write a paragraph about C4 photosynthesis
Answer:
Photosynthesis in plants. This main method is found mainly on herbaceous plants that generally live in hot regions and are called K4 plants.
in C4 photosynthesis, where a four-carbon compound is produced, unique leaf anatomy allows carbon dioxide to concentrate in 'bundle sheath' cells around Rubisco. This structure delivers carbon dioxide straight to Rubisco, effectively removing its contact with oxygen and the need for photorespiration
Explanation:
Iran has a president, however, government decisions are made by a group of religious leaders and are based on Islamic law. What type of government is in place in Iran?
Answer: It is a theocracy
Explanation: it's beacause they have a president and a supreme leader
Theocracy is type of government is in place in Iran. A theocracy is a form of government in which a supreme deity serves as the ultimate ruler.
What is theocracy?
The supreme deity may reign directly as a god in human form or indirectly through mortal slaves, usually members of the religious clergy, who carry out the deity's orders.
The governments of theocracies serve their divine leader or leaders rather than the populace because their laws are founded on religious pronouncements and rules.
Theocracies frequently operate in an oppressive manner, with severe penalties for breaking the rules. They serve their heavenly leader or leaders rather than the people. Democracy has no place in a theocracy, and the head's choices are final.
Therefore, Theocracy is type of government is in place in Iran. A theocracy is a form of government in which a supreme deity serves as the ultimate ruler.
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what is the function of endoplasm
Answer:
Endoplasmic reticulum (ER), in biology, a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions, being important particularly in the synthesis, folding, modification, and transport of proteins
Explanation:
what is photosynthesis
Why should the farming industry adopt sustainable agriculture practices?
Answer:
Agriculture often places significant pressure on natural resources and the environment.
Explanation:
Sustainable agricultural practices are intended to protect the environment, expand the Earth's natural resource base, and maintain and improve soil fertility.
50 POINTS AND BRAINLIEST PLEASE HELP ASAP
As a plant grows, its mass increases. The matter that makes up this new mass comes mostly from air and water that the plant changes into organic compounds such as cellulose using the energy from sunlight.
As an animal grows, its mass increases. The matter that makes up this new mass comes mostly from
A.
food that the animal has eaten and changed into other organic compounds.
B.
organic compounds that the animal breaks down into water and carbon dioxide.
C.
substances that the animal has eaten but cannot digest.
D.
air and water that the animal changes into organic compounds using the energy from sunlight.
Answer:
D.just like humans were going to need food for growth...The food that animals eat can be transformed into usable energy for cells or can be used to build new cells, which form tissues like skin and muscle. ... The process of growth involves eating food, breaking down food through digestion, absorbing nutrients from food, and building tissue.hope this helps
Explanation:
how does carbon dioxide pass through the stomata of a leaf?
Answer:
Plants get the carbon dioxide they need from the air through their leaves. It moves by diffusion through small holes in the underside of the leaf called stomata. These let carbon dioxide reach the other cells in the leaf, and also let the oxygen produced in photosynthesis leave the leaf easily.
Answer:
small holes on underside
please help please help please help please help please help
The root word “lun” or lune refers to the ____________
Answer:
Lun or Lunar are references for the moon.
Water molecules on a car windshield stay together in droplets. What
property of water is this? *
adhesion
high specific heat
cohesion
universal solvent
Answer:
cohesion
Explanation:
how do trans girls put on a bra? im trans mtf and i don't know how to put on a bra.pls help.
Answer:
Is this a troll
Explanation:
Just put it on like a shirt or ask someone for help
Moonlight is really ____________ being reflected
Answer:
Sunlight being reflected
Energy you get from eating an apple
A chemical
B sound
C. electrical
D. light
Answer:
a
Explanation:
cause apple not get sound electrical or light energy
Answer:
A chemical
Explanation:
when you eat an apple: The carbohydrate breaks down into a sugar called glucose and enters your bloodstream (where it's termed “blood sugar”). That sugar travels to your cells, where it's turned into energy for your body.
An apple doesn't produce sound, electrical or light energy therefore the answer is chemical energy
Which is one place that glaciers are found?
A.in the ocean
B.in the tropics
C.at low altitudes
D.at high latitudes
Answer:
D.High latitudes
Explanation:
I say this because many glaciers are found in Greenland and Antarctica which are both located in higher latitudes
what is the difference between an animal that has symmetry and one that is asymmetrical
Answer:
"Most animals are bilaterally symmetrical with a line of symmetry dividing their body into left and right sides along with a “head” and “tail” in addition to a top and bottom. Only sponges (phylum Porifera) have asymmetrical body plans."
Easy question for easy points
Answer:
A dominant trait is opposed to a recessive trait which is expressed only when two copies if the gene are shown
Answer:Teh first box
Explanation:
In genetics, dominance is the phenomenon of one variant of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive.
Wha
t is compound microscope
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects
Answer:
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects
2.Does reforestation have the same impact on the environment
as the original forest had? Why or why not?
Answer:
The answer is no, reforestation is just replanting trees/forests so it dosen't affect the environment
The process of meiosis does all of the following except:
Goes through two rounds of division.
Forms sex cells or spores.
Results in four unique haploid cells.
Produces two genetically identical cells.
Answer:
The last one does not happen meiosis create four genetically different haploid cells
Meiosis, on the other hand, creates four distinct daughter cells, each of which has half as many chromosomes as the parent cell. Thus, option D is correct.
What are the advantages of meiosis?Meiosis is crucial for three reasons: it promotes genetic diversity, sexual reproduction of diploid species, and the correction of genetic flaws.
A parent cell undergoes mitosis, which creates two identical daughter cells with the same number of chromosomes.
Genotypic diversity is produced, and appropriate homologous chromosomal segregation is ensured via meiotic crossing over.
Despite these functions, very little is known about the genetic and population genetic mechanisms that resulted in the evolution of species-specific variations in recombination rates.
Therefore, process of meiosis produces two genetically identical cells.
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what are products of the krebs cycle
Answer:
GTP.
3 NADH.
FADH2, which is converted to UQH2 in the presence of coenzyme Q (ubiquinone)
2 CO2 (carbon dioxide)
I’m confused on what’s the secret code
Answer:
the code is 98201408
Explanation:
Answer:
the code is 099955766580
These organisms are so important for an ecosystem that their removal would cause the entire ecosystem to change.
Answer:
keystone species
Explanation:
A. the water at the top of a wave moves blank
while the water at the bottom of a wave moves
B. The energy of the wave gets transferred to the blank blank
as it reaches shore.
C. blank pulls the top of the wave down when it reaches the shore. First to answer gets brainliest.
