Try Out 1 UTBK 2024 – Literasi Bahasa Inggris

A study of marital relationships in which one partner's sleeping and waking cycles differ from those of the other partner reveals that such couples share fewer activities with each other and have more violent arguments than do couples in a relationship in which both partners follow the same sleeping and waking patterns. Thus, mismatched sleeping and waking cycles can seriously jeopardize a marriage.

In the past most airline companies minimized aircraft weight to minimize fuel costs. The safest airline seats were heavy, and airlines equipped their planes with few of these seats. This year the seat that has sold best to airlines has been the safest one-a clear indication that airlines are assigning a higher priority to safe seating than to minimizing fuel costs.

A company plans to develop a prototype weeding machine that uses cutting blades with optical sensors and microprocessors that distinguish weeds from crop plants by differences in shade of color. The inventor of the machine claims that it will reduce labor costs by virtually eliminating the need for manual weeding.

Physician:
The hormone melatonin has shown promise as a medication for sleep disorders when taken in synthesized form. Because the long-term side effects of synthetic melatonin are unknown, however, I cannot recommend its use at this time.
Patient:
Your position is inconsistent with your usual practice. You prescrive many medications that you know have serious side effects, so concern about side effects cannot be the real reason you will not prescribe melatonin.

Passage 1
In the past century, due to the burning of fossil fuels in energy plants and cars, acid rain has become a cause of harm to the environment. However, rain would still be slightly acidic even if these activities were to stop. Acid rain would continue to fall, but it would not cause the problems we see now. The environment can handle slightly acidic rain, it just cannot keep up with the level of acid rain caused by burning fossil fuels.
A pH of 7 is considered neutral while pH below 7 is acidic and pH above 7 is alkaline, or basic. Pure rainwater can have pH as low as 5,5. Rainwater is acidic because carbon dioxide gas in the air reacts with the water to make carbonic acid. Since it is a weak acid, even a large amount of not lower the pH of water much.
Soil, lakes, and streams can tolerate slightly acidic rain. The water and soil contain alkaline materials that will neutralize acids. These include some types of rocks, plant and animal waste, and ashes from forest fires. Altogether, these materials can easily handle the slightly acidic rain that occurs naturally. The alkaline waste and ashes will slowly be used up, but more will be made to replace it. Anthropomorphic causes of acid rain, such as the burning of fossil fuels, release nitrogen oxide and sulfur oxide gases. These gases react with water to make nitric acid and sulfuric acid. Since these are both strong acids, small amounts can lower the pH of rainwater to 3 or less. Such as low pH requires much more alkaline material to neutralize it. Acid rain with a lower pH uses up alkaline materials faster, and more cannot be made quickly enough to replace what is used up. Soil and water become more acidic and remain that way, as they are unable to neutralize the strong acid.
Passage 2
In humans, keeping a constant balance between acidity and alkalinity in the blood is essential. If blood pH drops below 7,35 or rises above 7,45, all of the functions in the body are impaired and life-threatening conditions can soon develop. Many processes in the body produce acid wastes, which would lower the pH of blood below the safe level unless neutralized. Several systems are in place to keep pH constant within the necessary range. Certain conditions, however, can cause acids to be made faster than these systems can react.
Most of the pH control involves three related substances: carbon dioxide, carbonic acid, and bicarbonate ions. Carbonic acid is formed when carbon dioxide reacts with water. Bicarbonate ions are formed when the carbonic acid releases a hydrogen ion. Excess carbonic acid lowers the pH, while excess bicarbonate ions raise it.
The kidneys store bicarbonate ions and will release or absorb them to help adjust the pH of the blood. Breathing faster removes more carbon dioxide from the blood, which reduces the amount of carbonic acid: in contrast, breathing more slowly has the opposite effect. In the healthy body, these system automatically neutralizes normal amounts of acid wastes and maintain blood pH within the very small range necessary for the body to function normally.
In some cases, these systems can be overwhelmed. This can happen to people with diabetes if their blood sugar drops too low for too long. People with diabetes do not make enough insulin, which the body uses to release stored sugar into the blood to supply the body with energy. If a person's insulin level gets too low for too long, the body breaks down fats to use for energy. The waste produced from breaking down fats is acidic, so the blood pH drops. If the kidneys exhaust their supply of bicarbonate ions, and the lungs cannot remove carbon dioxide fast enough to raise pH, all of the other functions in the body begin to fail as well. The person will need medical treatment to support these functions until the pH balancing system can catch up. The system will then keep the blood pH constant, as long as the production of acid wastes does not exceed the body's capacity to neutralize them.

Passage 1
In the past century, due to the burning of fossil fuels in energy plants and cars, acid rain has become a cause of harm to the environment. However, rain would still be slightly acidic even if these activities were to stop. Acid rain would continue to fall, but it would not cause the problems we see now. The environment can handle slightly acidic rain, it just cannot keep up with the level of acid rain caused by burning fossil fuels.
A pH of 7 is considered neutral while pH below 7 is acidic and pH above 7 is alkaline, or basic. Pure rainwater can have pH as low as 5,5. Rainwater is acidic because carbon dioxide gas in the air reacts with the water to make carbonic acid. Since it is a weak acid, even a large amount of not lower the pH of water much.
Soil, lakes, and streams can tolerate slightly acidic rain. The water and soil contain alkaline materials that will neutralize acids. These include some types of rocks, plant and animal waste, and ashes from forest fires. Altogether, these materials can easily handle the slightly acidic rain that occurs naturally. The alkaline waste and ashes will slowly be used up, but more will be made to replace it. Anthropomorphic causes of acid rain, such as the burning of fossil fuels, release nitrogen oxide and sulfur oxide gases. These gases react with water to make nitric acid and sulfuric acid. Since these are both strong acids, small amounts can lower the pH of rainwater to 3 or less. Such as low pH requires much more alkaline material to neutralize it. Acid rain with a lower pH uses up alkaline materials faster, and more cannot be made quickly enough to replace what is used up. Soil and water become more acidic and remain that way, as they are unable to neutralize the strong acid.
Passage 2
In humans, keeping a constant balance between acidity and alkalinity in the blood is essential. If blood pH drops below 7,35 or rises above 7,45, all of the functions in the body are impaired and life-threatening conditions can soon develop. Many processes in the body produce acid wastes, which would lower the pH of blood below the safe level unless neutralized. Several systems are in place to keep pH constant within the necessary range. Certain conditions, however, can cause acids to be made faster than these systems can react.
Most of the pH control involves three related substances: carbon dioxide, carbonic acid, and bicarbonate ions. Carbonic acid is formed when carbon dioxide reacts with water. Bicarbonate ions are formed when the carbonic acid releases a hydrogen ion. Excess carbonic acid lowers the pH, while excess bicarbonate ions raise it.
The kidneys store bicarbonate ions and will release or absorb them to help adjust the pH of the blood. Breathing faster removes more carbon dioxide from the blood, which reduces the amount of carbonic acid: in contrast, breathing more slowly has the opposite effect. In the healthy body, these system automatically neutralizes normal amounts of acid wastes and maintain blood pH within the very small range necessary for the body to function normally.
In some cases, these systems can be overwhelmed. This can happen to people with diabetes if their blood sugar drops too low for too long. People with diabetes do not make enough insulin, which the body uses to release stored sugar into the blood to supply the body with energy. If a person's insulin level gets too low for too long, the body breaks down fats to use for energy. The waste produced from breaking down fats is acidic, so the blood pH drops. If the kidneys exhaust their supply of bicarbonate ions, and the lungs cannot remove carbon dioxide fast enough to raise pH, all of the other functions in the body begin to fail as well. The person will need medical treatment to support these functions until the pH balancing system can catch up. The system will then keep the blood pH constant, as long as the production of acid wastes does not exceed the body's capacity to neutralize them.

Passage 1
In the past century, due to the burning of fossil fuels in energy plants and cars, acid rain has become a cause of harm to the environment. However, rain would still be slightly acidic even if these activities were to stop. Acid rain would continue to fall, but it would not cause the problems we see now. The environment can handle slightly acidic rain, it just cannot keep up with the level of acid rain caused by burning fossil fuels.
A pH of 7 is considered neutral while pH below 7 is acidic and pH above 7 is alkaline, or basic. Pure rainwater can have pH as low as 5,5. Rainwater is acidic because carbon dioxide gas in the air reacts with the water to make carbonic acid. Since it is a weak acid, even a large amount of not lower the pH of water much.
Soil, lakes, and streams can tolerate slightly acidic rain. The water and soil contain alkaline materials that will neutralize acids. These include some types of rocks, plant and animal waste, and ashes from forest fires. Altogether, these materials can easily handle the slightly acidic rain that occurs naturally. The alkaline waste and ashes will slowly be used up, but more will be made to replace it. Anthropomorphic causes of acid rain, such as the burning of fossil fuels, release nitrogen oxide and sulfur oxide gases. These gases react with water to make nitric acid and sulfuric acid. Since these are both strong acids, small amounts can lower the pH of rainwater to 3 or less. Such as low pH requires much more alkaline material to neutralize it. Acid rain with a lower pH uses up alkaline materials faster, and more cannot be made quickly enough to replace what is used up. Soil and water become more acidic and remain that way, as they are unable to neutralize the strong acid.
Passage 2
In humans, keeping a constant balance between acidity and alkalinity in the blood is essential. If blood pH drops below 7,35 or rises above 7,45, all of the functions in the body are impaired and life-threatening conditions can soon develop. Many processes in the body produce acid wastes, which would lower the pH of blood below the safe level unless neutralized. Several systems are in place to keep pH constant within the necessary range. Certain conditions, however, can cause acids to be made faster than these systems can react.
Most of the pH control involves three related substances: carbon dioxide, carbonic acid, and bicarbonate ions. Carbonic acid is formed when carbon dioxide reacts with water. Bicarbonate ions are formed when the carbonic acid releases a hydrogen ion. Excess carbonic acid lowers the pH, while excess bicarbonate ions raise it.
The kidneys store bicarbonate ions and will release or absorb them to help adjust the pH of the blood. Breathing faster removes more carbon dioxide from the blood, which reduces the amount of carbonic acid: in contrast, breathing more slowly has the opposite effect. In the healthy body, these system automatically neutralizes normal amounts of acid wastes and maintain blood pH within the very small range necessary for the body to function normally.
In some cases, these systems can be overwhelmed. This can happen to people with diabetes if their blood sugar drops too low for too long. People with diabetes do not make enough insulin, which the body uses to release stored sugar into the blood to supply the body with energy. If a person's insulin level gets too low for too long, the body breaks down fats to use for energy. The waste produced from breaking down fats is acidic, so the blood pH drops. If the kidneys exhaust their supply of bicarbonate ions, and the lungs cannot remove carbon dioxide fast enough to raise pH, all of the other functions in the body begin to fail as well. The person will need medical treatment to support these functions until the pH balancing system can catch up. The system will then keep the blood pH constant, as long as the production of acid wastes does not exceed the body's capacity to neutralize them.

Passage 1
In the past century, due to the burning of fossil fuels in energy plants and cars, acid rain has become a cause of harm to the environment. However, rain would still be slightly acidic even if these activities were to stop. Acid rain would continue to fall, but it would not cause the problems we see now. The environment can handle slightly acidic rain, it just cannot keep up with the level of acid rain caused by burning fossil fuels.
A pH of 7 is considered neutral while pH below 7 is acidic and pH above 7 is alkaline, or basic. Pure rainwater can have pH as low as 5,5. Rainwater is acidic because carbon dioxide gas in the air reacts with the water to make carbonic acid. Since it is a weak acid, even a large amount of not lower the pH of water much.
Soil, lakes, and streams can tolerate slightly acidic rain. The water and soil contain alkaline materials that will neutralize acids. These include some types of rocks, plant and animal waste, and ashes from forest fires. Altogether, these materials can easily handle the slightly acidic rain that occurs naturally. The alkaline waste and ashes will slowly be used up, but more will be made to replace it. Anthropomorphic causes of acid rain, such as the burning of fossil fuels, release nitrogen oxide and sulfur oxide gases. These gases react with water to make nitric acid and sulfuric acid. Since these are both strong acids, small amounts can lower the pH of rainwater to 3 or less. Such as low pH requires much more alkaline material to neutralize it. Acid rain with a lower pH uses up alkaline materials faster, and more cannot be made quickly enough to replace what is used up. Soil and water become more acidic and remain that way, as they are unable to neutralize the strong acid.
Passage 2
In humans, keeping a constant balance between acidity and alkalinity in the blood is essential. If blood pH drops below 7,35 or rises above 7,45, all of the functions in the body are impaired and life-threatening conditions can soon develop. Many processes in the body produce acid wastes, which would lower the pH of blood below the safe level unless neutralized. Several systems are in place to keep pH constant within the necessary range. Certain conditions, however, can cause acids to be made faster than these systems can react.
Most of the pH control involves three related substances: carbon dioxide, carbonic acid, and bicarbonate ions. Carbonic acid is formed when carbon dioxide reacts with water. Bicarbonate ions are formed when the carbonic acid releases a hydrogen ion. Excess carbonic acid lowers the pH, while excess bicarbonate ions raise it.
The kidneys store bicarbonate ions and will release or absorb them to help adjust the pH of the blood. Breathing faster removes more carbon dioxide from the blood, which reduces the amount of carbonic acid: in contrast, breathing more slowly has the opposite effect. In the healthy body, these system automatically neutralizes normal amounts of acid wastes and maintain blood pH within the very small range necessary for the body to function normally.
In some cases, these systems can be overwhelmed. This can happen to people with diabetes if their blood sugar drops too low for too long. People with diabetes do not make enough insulin, which the body uses to release stored sugar into the blood to supply the body with energy. If a person's insulin level gets too low for too long, the body breaks down fats to use for energy. The waste produced from breaking down fats is acidic, so the blood pH drops. If the kidneys exhaust their supply of bicarbonate ions, and the lungs cannot remove carbon dioxide fast enough to raise pH, all of the other functions in the body begin to fail as well. The person will need medical treatment to support these functions until the pH balancing system can catch up. The system will then keep the blood pH constant, as long as the production of acid wastes does not exceed the body's capacity to neutralize them.

Passage 1
In the past century, due to the burning of fossil fuels in energy plants and cars, acid rain has become a cause of harm to the environment. However, rain would still be slightly acidic even if these activities were to stop. Acid rain would continue to fall, but it would not cause the problems we see now. The environment can handle slightly acidic rain, it just cannot keep up with the level of acid rain caused by burning fossil fuels.
A pH of 7 is considered neutral while pH below 7 is acidic and pH above 7 is alkaline, or basic. Pure rainwater can have pH as low as 5,5. Rainwater is acidic because carbon dioxide gas in the air reacts with the water to make carbonic acid. Since it is a weak acid, even a large amount of not lower the pH of water much.
Soil, lakes, and streams can tolerate slightly acidic rain. The water and soil contain alkaline materials that will neutralize acids. These include some types of rocks, plant and animal waste, and ashes from forest fires. Altogether, these materials can easily handle the slightly acidic rain that occurs naturally. The alkaline waste and ashes will slowly be used up, but more will be made to replace it. Anthropomorphic causes of acid rain, such as the burning of fossil fuels, release nitrogen oxide and sulfur oxide gases. These gases react with water to make nitric acid and sulfuric acid. Since these are both strong acids, small amounts can lower the pH of rainwater to 3 or less. Such as low pH requires much more alkaline material to neutralize it. Acid rain with a lower pH uses up alkaline materials faster, and more cannot be made quickly enough to replace what is used up. Soil and water become more acidic and remain that way, as they are unable to neutralize the strong acid.
Passage 2
In humans, keeping a constant balance between acidity and alkalinity in the blood is essential. If blood pH drops below 7,35 or rises above 7,45, all of the functions in the body are impaired and life-threatening conditions can soon develop. Many processes in the body produce acid wastes, which would lower the pH of blood below the safe level unless neutralized. Several systems are in place to keep pH constant within the necessary range. Certain conditions, however, can cause acids to be made faster than these systems can react.
Most of the pH control involves three related substances: carbon dioxide, carbonic acid, and bicarbonate ions. Carbonic acid is formed when carbon dioxide reacts with water. Bicarbonate ions are formed when the carbonic acid releases a hydrogen ion. Excess carbonic acid lowers the pH, while excess bicarbonate ions raise it.
The kidneys store bicarbonate ions and will release or absorb them to help adjust the pH of the blood. Breathing faster removes more carbon dioxide from the blood, which reduces the amount of carbonic acid: in contrast, breathing more slowly has the opposite effect. In the healthy body, these system automatically neutralizes normal amounts of acid wastes and maintain blood pH within the very small range necessary for the body to function normally.
In some cases, these systems can be overwhelmed. This can happen to people with diabetes if their blood sugar drops too low for too long. People with diabetes do not make enough insulin, which the body uses to release stored sugar into the blood to supply the body with energy. If a person's insulin level gets too low for too long, the body breaks down fats to use for energy. The waste produced from breaking down fats is acidic, so the blood pH drops. If the kidneys exhaust their supply of bicarbonate ions, and the lungs cannot remove carbon dioxide fast enough to raise pH, all of the other functions in the body begin to fail as well. The person will need medical treatment to support these functions until the pH balancing system can catch up. The system will then keep the blood pH constant, as long as the production of acid wastes does not exceed the body's capacity to neutralize them.

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larer. Because these galaxies' mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars-that is, they evolve much more slowly. These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons - subatomic particles that are generally protons or neutrons-are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larer. Because these galaxies' mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars-that is, they evolve much more slowly. These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons - subatomic particles that are generally protons or neutrons-are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larer. Because these galaxies' mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars-that is, they evolve much more slowly. These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons - subatomic particles that are generally protons or neutrons-are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larer. Because these galaxies' mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars-that is, they evolve much more slowly. These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons - subatomic particles that are generally protons or neutrons-are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.

The variety of fish reproduction techniques provides an example of the adaptive complexity that ecologists have found. Most spawning is synchronized with phases of the moon, and eggs are fertilized in the water column. However, some species lay eggs on the sea bottom or in a protected area. Damselfishes will guard their nests quite aggressively, while jawfish and cardinalfish incubate eggs in the mouth. Seahorse and pipefish carry their eggs in a pouch.
Most hermaphroditic species follow the protogynous pattern of the fairy basselet. If the male disappears, the dominant female in his harem will change sex within days and take over his role within hours. However, a few species are protandrous, where the fish are male first and then become female. Much remains to be learned about fish reproduction, and evolutionary biologists find that the coral environment provides them with many opportunities to observe a variety of species and specialized behaviours.
The reef itself is alive with many billions of coral colonies plus other limestone-depositing organisms, growing among he skeletons of their predecessors. Reefs grow on the continental shelf requirements concerning the amount of available light, and the ocean's clarity, temperature, and movement have restricted the geographic locations of the Earth's reefs, these requirements have not limited the ecological complexity of eef communities.
Species representing more phyla than those found in a tropical rainforest live on coral reefs. Scientists counted 1,441 worms on one coral head alone, and these worms belonged to over a hundred different families. Six of the Earth's seven species of marine turtles fish species, make coral ecosystems their home. Perhaps more notably, representatives from all fish families and most general are reef inhabitants.
Scientists study reef fishes not only because of the diverse sampling of species but also because of the range of behaviours and relationships between species and other animals that is available for analysis. Intense competition and predation have caused fishes to carve out special niches. Mimicry and camouflage offer just two ways for species to blend in with their surroundings. Symbiotic relationships between fish and other organisms also occur with frequency on coral reefs. The anemonefish share their habitat with sea anemones in a symbiotic relationship that scientists have yet to unravel completely. The defensive nematocysts of the anemone are used to stun prey, but the anemonefish are resistant to these stinging cells. Researchers believe that the fish secrets a mucous coating that mimics that of the anemone allowing for chemical signals to prohibit the firing of the cells. One theory holds that the fish obtain these chemicals by rubbing against the sea anemone's tentacles. The benefits, if any, to the anemone for having these fish live with them is not clear.

The variety of fish reproduction techniques provides an example of the adaptive complexity that ecologists have found. Most spawning is synchronized with phases of the moon, and eggs are fertilized in the water column. However, some species lay eggs on the sea bottom or in a protected area. Damselfishes will guard their nests quite aggressively, while jawfish and cardinalfish incubate eggs in the mouth. Seahorse and pipefish carry their eggs in a pouch.
Most hermaphroditic species follow the protogynous pattern of the fairy basselet. If the male disappears, the dominant female in his harem will change sex within days and take over his role within hours. However, a few species are protandrous, where the fish are male first and then become female. Much remains to be learned about fish reproduction, and evolutionary biologists find that the coral environment provides them with many opportunities to observe a variety of species and specialized behaviours.
The reef itself is alive with many billions of coral colonies plus other limestone-depositing organisms, growing among he skeletons of their predecessors. Reefs grow on the continental shelf requirements concerning the amount of available light, and the ocean's clarity, temperature, and movement have restricted the geographic locations of the Earth's reefs, these requirements have not limited the ecological complexity of eef communities.
Species representing more phyla than those found in a tropical rainforest live on coral reefs. Scientists counted 1,441 worms on one coral head alone, and these worms belonged to over a hundred different families. Six of the Earth's seven species of marine turtles fish species, make coral ecosystems their home. Perhaps more notably, representatives from all fish families and most general are reef inhabitants.
Scientists study reef fishes not only because of the diverse sampling of species but also because of the range of behaviours and relationships between species and other animals that is available for analysis. Intense competition and predation have caused fishes to carve out special niches. Mimicry and camouflage offer just two ways for species to blend in with their surroundings. Symbiotic relationships between fish and other organisms also occur with frequency on coral reefs. The anemonefish share their habitat with sea anemones in a symbiotic relationship that scientists have yet to unravel completely. The defensive nematocysts of the anemone are used to stun prey, but the anemonefish are resistant to these stinging cells. Researchers believe that the fish secrets a mucous coating that mimics that of the anemone allowing for chemical signals to prohibit the firing of the cells. One theory holds that the fish obtain these chemicals by rubbing against the sea anemone's tentacles. The benefits, if any, to the anemone for having these fish live with them is not clear.