Primary producers, which are also known as autotrophs, harness energy through the use of either photosynthesis or chemosynthesis. The sun’s light is harnessed by the producers to carry out the process of photosynthesis. In this process, plants convert water and carbon dioxide into glucose and oxygen. On the other hand, since sunlight can’t reach the deepest parts of the ocean, the organisms living in this zone carry out chemosynthesis. Through this process, the bacteria that live near the hydrothermal vents in the ocean floor are able to harness chemical energy.

c. use energy they take in from the environment to convert inorganic molecules into complex organic molecules

A carnivore is a consumer that feeds on meat to obtain energy and nutrients. In this case, A is not the correct answer because it is a primary producer. B is also incorrect because it is a decomposer, whereas C is an omnivore. D is a carnivore; hence, it is the correct answer.

d (carnivore)

Decomposers break down the remains of a decaying organic matter and recycle the vital nutrients into the soil. Later on, these nutrients are absorbed by the plants. Examples of decomposers include fungi and bacteria. These organisms acquire the nutrients using chemical and biological processes instead of ingesting it. On the other hand, detritivores consume or ingest dead plant and animal matter. Examples of detritivores include earthworms and sea cucumbers.

A: An earthworm is a detritivore. Detritivores consume or ingest dead plant and animal matter.
B: A bear is an omnivore. Omnivores eat plants and other animals.
C: A cow is a herbivore. Herbivores are animals that feed on plants.
D: A snail is an omnivore. Aside from plants and other animals, other omnivores can also feed on other food sources, such as algae and fungi.
E: An owl is a carnivore. Carnivores feed on flesh.
F: A human is an omnivore. Omnivores eat plants and other animals.

A: detritivore
B: omnivore
C: herbivore
D: omnivore
E: carnivore
F: omnivore

Primary producers or autotrophs harness energy to perform either photosynthesis or chemosynthesis to make their own food. Both of these processes produce glucose, which serves as the stored energy in cells. However, photosynthesis and chemosynthesis are different from one another in terms of their energy sources. The sun’s light is harnessed by the producers to carry out the process of photosynthesis. In this process, plants convert water and carbon dioxide into glucose and oxygen. On the other hand, since sunlight can’t reach the deepest parts of the ocean, the organisms living in this zone carry out chemosynthesis. Through this process, the bacteria that live near the hydrothermal vents in the ocean floor are able to harness chemical energy instead of light energy. The chemical energy comes in the form of inorganic compounds such as methane, hydrogen gas, or hydrogen sulfide. These compounds combine react oxygen and carbon dioxide to produce glucose.

In an ecosystem, the energy is usually transferred in a linear path or a one-way stream. A food chain shows how energy is transferred using this way. Based on the statement, it follows a one-way path wherein the algae is eaten by a small fish, which in turn was eaten by a large fish. Therefore, it is a food chain.

b. food chain

The pyramid of energy indicates the amount of energy at each trophic level and the actual role of each organism in the process of energy transfer. The pyramid of numbers shows the number of individual organisms that exist at different trophic levels. The pyramid of biomass tells us the amount of living tissue or the total mass of organisms within each trophic level. The biogeochemical cycle involves the circular flow of matter around the biosphere.

Therefore, C is the correct answer.

c. pyramid of biomass

Primary producers or autotrophs are the organisms that lie at the base or at the bottom of a food chain. They harness energy from nonliving sources to perform either photosynthesis or chemosynthesis in order to make their own food.

Any matter that does not get past on to the trophic level above dies, and it is returned to the soil via decomposers and detritivores.

The energy transfer is only ten percent efficient because much of the energy is used up on life processes, such as respiration, growth, movement, and reproduction.

In an ecosystem, the energy is usually transferred by the means of a food chain or a food web. For an instance, the solar energy is used by the primary producers such as plants and algae so they can convert it into chemical energy or glucose. The chemical energy stored in plants are transferred to the primary consumers once they are consumed. Then, a primary consumer is eaten by a secondary consumer. Once these organisms die, decomposers return the nutrients into the soil, which is later absorbed by the plants.

According to the law of conservation of mass and energy, the amount of matter never decreases over time. Both mass and energy are only transformed from one form into another. In an ecosystem, the flow of mass is transferred from one trophic level into the next one during biogeochemical cycles.

c. The total amount of matter decreases over time.

Due to the limitations of the resources entering the Earth’s atmosphere, nutrients are all recycled. The three nutrients that are being circulated and recycled in the Earth’s biosphere include carbon, nitrogen, and phosphorus. These essential nutrients are recycled in biogeochemical cycles.

a. biogeochemical cycles

The phosphorus cycle does not involve the atmosphere because it is usually in a liquid state at a room temperature. This is the reason why it cycles only through water, sediments, or soil.

Water enters the atmosphere through evaporation and transpiration. Evaporation occurs when the heat from the sun evaporates the water from oceans, lakes, rivers, and other large bodies of water. On the other hand, transpiration occurs when plants lose water by the means of their leaves.

Carbon is stored in the biosphere in the following ways:
a. Carbon is present in the atmosphere in the form of carbon dioxide gas.
b. A supply of carbon is present in a decaying matter and waste.
c. There is an amount of carbon in the organic matter in soils.
d. Carbon is present in fossil fuels in the form of coal and oil that are found in rock layers within the Earth’s crust.
e. Carbon is present in the oceans in the form of dissolved carbon dioxide and calcium carbonate in the shells of marine organisms.

There are only certain types of bacteria which can utilize the nitrogen gas. The nitrogen that is released by bacteria is converted into ammonia, nitrates, and nitrites in a process called nitrogen fixation, which is the first step in the nitrogen cycle. In turn, these compounds are used by producers to convert it into chemical energy. Once consumers eat the producers, consumers use nitrogen to make protein and nucleic acids.

Nutrient limitation is a sign which tells us that a certain nutrient is low on supply. This indicates that the ecosystem is a little off balance. When a nutrient is low on supply, the rate of productivity of producers will be restricted. This causes people to use fertilizers on plants to make up for the lack of nutrients in the soil.

Changes in the ocean’s nutrient levels can affect the aquatic food webs in a negative way. If there is a nutrient limitation, the productivity of the marine ecosystem would decrease. On the other hand, if there is a dramatic increase in the nutrient levels of the ocean water, an algal bloom occurs. An excess in the algal growth can block sunlight and decrease the oxygen level in the water. These conditions can kill aquatic organisms. Once an organism is taken out of the food web, it will throw off the balance in the aquatic ecosystem. When organisms in a particular trophic level disappear, it will cause an increase in the population of the previous trophic level and a decrease in the population of the next trophic level.

The table below shows the cycles of matter and the examples of the processes that are involved in each cycle.

The table below shows the cycles of matter and the examples of the processes that are involved in each cycle. (Click to see the table)

One ecological phenomenon which can be studied using a model is the predator-prey relationship. Studying this model would help us know how predators affect prey, and vice versa. It can also help us determine the effect of this relationship in their physical environment. More importantly, it can also help predict the population growth of predator species and their prey.

Here are the questions which can be asked regarding the excess growth of green algae:
a. What condition causes the green algae to grow rapidly?
b. What is the primary source of nitrogen and phosphorus in the water?
c. Is there a farm, factory, or sewage near the pond?
d. How fast can the green algae grow?
e. Is the excessive algae growth dangerous for aquatic animals?
f. How do you get rid of the green algae?

a. According to the food web, the producers are the tree and the grass. b. Insects, such as flies and beetles, slugs, and snails are the decomposers that can be added to the food web. They are the organisms that consume the energy from waste and remains of plants and animals. c. Please see the diagram below. d. If the primary producers on both food chains have 100% chemical energy, second-level consumers would get 1% chemical energy. On the other hand, third-level consumers get 0.1% energy.

a. According to the food web, the producers are the tree and the grass.

b. Insects, such as flies and beetles, slugs, and snails are the decomposers that can be added to the food web. They are the organisms that consume the energy from waste and remains of plants and animals.

c. Please see the diagram below.

d. If the primary producers on both food chains have 100% chemical energy, second-level consumers would get 1% chemical energy. On the other hand, third-level consumers get 0.1% energy.

Just like in the deep ocean, this cave lacks sunlight; hence, these organisms perform chemosynthesis. They are able to harness energy using hydrogen sulfide gas, which is carried by the groundwater into the cave. This gas is an important inorganic compound that is combined with carbon dioxide and oxygen to produce glucose in chemosynthesis.

The flow of energy and nutrients, which are necessary for the survival of living organisms, circulate around the biosphere. The three nutrients that are being circulated and recycled in the Earth’s atmosphere include carbon, nitrogen, and phosphorus. These essential nutrients are recycled in biogeochemical cycles. These cycles are classified into three processes namely, biological processes, which consists of all the activities of living organisms; geological processes that include movements of matter in the Earth’s surface; and chemical and physical processes that occur within the three states of matter. In biological processes, the energy in the biosphere is usually transferred in a one-way stream via food chain or food web. For example, the sun’s energy is used by the primary producers during photosynthesis to make glucose. In turn, the glucose stored in plants are transferred to the consumers. Once these organisms die, decomposers return the nutrients into the soil, which is later absorbed by the plants.

The diagram below shows how microorganisms take part in the nitrogen cycle.


These processes are important when it comes to recycling the nutrients in the environment. Since not all organisms can utilize nitrogen gas directly, these microorganisms convert nitrogen into different nitrogen compounds, such as ammonia, nitrites, and nitrates. In this way, producers can now use these compounds in carrying out their life processes.

The pieces of evidence that would support the scientist’s claim about the nitrogen fertilizer being the main culprit for the death of a large number of trout are as follows:

1. The water sample contains a high concentration of phosphorus and nitrogen.
2. There is an algal bloom in the stream.
3. The level of dissolved oxygen in the water is very low, which resulted in the death of many fishes due to hypoxia.

Here is a sample flowchart that shows a simple marine food chain and the nitrogen that occurs in an aquatic environment.


The phytoplankton, which is one of the photosynthetic organisms in the marine environment, harness solar energy to conduct photosynthesis and produce chemical energy. In turn, the stored chemical energy is transferred to the sardine once they feed on the plankton. In this case, the sardine that feeds on the plankton gets eaten by the salmon, which is later consumed by a killer whale.

The killer whale excretes its waste products in the form of ammonia. Once it dies, the decaying matter is broken down by decomposers, wherein the ammonia is converted into a nitrite by a nitrifying bacteria called Nitrosomonas.

In turn, another kind of bacteria converts the nitrite into nitrate. This bacteria is called a Nitrobacter. Plants absorb nitrogen in the form of ammonia or nitrate. Once the plants are eaten by the fishes or other aquatic organisms, the cycle starts again.

When organisms, such as humans and animals, undergo cellular respiration, they absorb oxygen and release carbon dioxide into the atmosphere. In turn, plants absorb the carbon dioxide in the atmosphere during photosynthesis. In photosynthesis, plants harness sunlight in order to convert carbon dioxide and water into glucose and oxygen. This process is highly important in recycling carbon dioxide in the atmosphere.

Detergents were banned because they contain phosphorus. This is a nutrient that becomes a threat when a high concentration is introduced to the primary producers in the freshwater and marine environment. It causes a rapid growth in the algae population and results in a phenomenon called algal bloom.

The reason why each trophic level receives a reduced amount of stored energy from the previous level is that the energy was already consumed by the individual in order to carry out its life processes or functions. In addition, most of the energy is released into the environment in the form of heat.

Through following the processes in the carbon cycle, we can also determine how the energy flows on earth. Most of the chemical energy that is used by organisms is stored in organic compounds whose molecules contain carbon atoms.

The carbon cycle occurs in the atmosphere and in the hydrosphere. Terrestrial producers use carbon dioxide from the atmosphere and aquatic producers get carbon dioxide from water to generate chemical energy (glucose) and oxygen, which are both needed by consumers to sustain life. In turn, once consumers eat the plants, they get the stored energy and return carbon dioxide in the atmosphere through respiration. Eventually, when plants and animals die, decomposers consume the organic matter and release carbon dioxide during respiration.

Decomposition, pressure, and heat allow the compaction of the dead matter and return carbon as underground deposits or fossil fuels. When fossil fuels are burned to generate energy, carbon dioxide is released in the atmosphere.

The carbon cycle occurs in the atmosphere and in the hydrosphere. Terrestrial producers use carbon dioxide from the atmosphere and aquatic producers get carbon dioxide from water to generate chemical energy (glucose) and oxygen, which are both needed by consumers to sustain life. In turn, once consumers eat the plants, they get the stored energy and return carbon dioxide in the atmosphere through respiration. Eventually, when plants and animals die, decomposers consume the organic matter and release carbon dioxide during respiration.

Decomposition, pressure, and heat allow the compaction of the dead matter and return carbon as underground deposits or fossil fuels. When fossil fuels are burned to generate energy, carbon dioxide is released in the atmosphere.

The cycling of matter and energy flow on Earth involves biological processes, geological processes, chemical and physical processes, as well as human activities. These processes fit in the part that explains how all the earth systems work and how they are all involved in recycling the matter within and between ecosystems.

On the other hand, human activities that affect the cycles involve mining, burning of fossil fuels, burning forests, clearing land for building and farming, and using fertilizers. These activities, which lie in the outermost ring of the model, are the human causes of global change because their interference with the natural processes causes the entire global systems to become unbalanced.

Since the graph shows an uphill pattern, it indicates a positive relationship between the average annual rainfall and the rate of plant tissue production. This means that when the rainfall increases, the productivity of the plants also increases.

If the rainfall is beyond 4000 mm, other factors would begin to limit the productivity in the ecosystem. In this case, the productivity level will begin to level out and decrease once the average annual rainfall reaches 4000 mm and 6000 mm.

If the rainfall is beyond 4000 mm, other factors would begin to limit the productivity in the ecosystem. In this case, the productivity level will begin to level out and decrease once the average annual rainfall reaches 4000 mm and 6000 mm. (Click to see the graph)

Aside from the amount of water, other factors that can influence the primary productivity of an ecosystem includes sunlight exposure, temperature, nutrient level in soil, and clean air.

Question about sustainable agriculture: How does the aquaponics system take advantage of the natural biogeochemical cycles without harming or disrupting them?

Answer: Aquaponic farming is a form of agriculture that integrates and combines the raising of fishes (aquaculture) and the soil-less growing of plants (hydroponics). In this integrated system, the excretion of the fishes is broken down by nitrifying bacteria and utilized by the plants as nutrients. Once the water is filtered by the plants, it goes back to the aquaculture system. This mechanism saves a lot of water since it gets recycled or circulated in the whole system.

This type of farming is not only considered economical and productive, but it is environment-friendly. It does not employ the use of chemical fertilizers, pesticides, and herbicides, which are the chemicals that are known to harm or disrupt the ecosystem. Therefore, it prevents the effects of fertilizer runoff, which occurs from traditional farming.

The diagram below shows how the energy in the food that we eat originated from the primary producers and its consumers.

First, the plankton or the tiny drifting producers, harness the sun’s energy to produce chemical energy through photosynthesis. In turn, the sardine gets this stored energy when they feed on the plankton. Then, when the salmon feeds on the sardine, the energy gets transferred to the second-level consumer. Once the salmon gets caught for human consumption, the stored energy in the salmon is transferred to the humans (third-level consumers).

On the other hand, the lemon tree and the broccoli plant are both primary producers. They harness solar energy during photosynthesis to produce chemical energy. When the lemon and broccoli are consumed by a human, the stored chemical energy is transferred. In turn, the cells in the human body use this energy to carry out their function and other life processes.

The diagram below shows how the energy in the food that we eat originated from the primary producers and its consumers. (Click to see the diagram)

Through the help of energy, biogeochemical cycles provide the organisms with different elements and nutrients that are recycled within and between ecosystems. These nutrients and energy are transferred from one organism into another through their feeding relationships.

For example, the plants that conduct photosynthesis harness sunlight and use carbon dioxide from the atmosphere and water to produce chemical energy. In turn, they release oxygen, which is a gas needed by consumers for respiration. Once the consumers feed on the plants, they get to use the stored chemical energy to perform or carry out their life processes. In turn, they release carbon dioxide in the atmosphere, which is again taken by the plants for photosynthesis.