Lesson 2: Cycling of Matter and Energy Biology B Unit 2: Energy Flow

Why are producers always the first trophic level in an ecosystem?

Producers are the first level because they have a direct relationship with the primary source of energy. The primary source of energy almost always is radiant energy from the sun. The producers are able to convert light energy into chemical energy through photosynthesis.

If an ecosystem typically contains 5000 kilograms of producers, and the introduction of an invasive species reduces this to 2000 kilograms, what could happen to consumers in the highest trophic level?

The ecosystem originally has enough energy for five kilograms of the top-level consumers or those in the highest trophic levels. Having fewer producers means the ecosystem only has enough energy for two kilograms of the top-level consumers.

132 KCal (actual transfer)1,650 Kcal (total input)×100

The efficiency of energy transfer from the fox to the coyote is 8%.

Create a biomass pyramid with 3 levels (producers, primary consumers, and top consumers) using the following data. Make sure to place all the producers in the same level. Number of maple tree - 150 Number of oak trees - 50 Number of shrubs - 400 Number of ferns - 1600 Number of deer (omnivores) - 500 Number of wolves (carnivores) - 50

Top consumers - 50 Primary consumers - 500 Producers - 2200

Which of the following statements best explains how biodiversity and sustainability are related? Explain your answer. When there is high biodiversity, there is higher sustainability. When biodiversity is lower, there is higher sustainability. There is no correlation between biodiversity and sustainability.

The first statement is correct. There is a correlation between high biodiversity and sustainability.

How does cutting down trees affect the amount of carbon that is released?

Trees are sinks or storage areas that hold carbon and, when the trees are cut down, the carbon is released and there are fewer plants to absorb the carbon dioxide.

trophic level

The first trophic level in every ecosystem is autotrophs that produce their own food. They provide the energy for the rest of the food chain or food web. Each level after that are heterotrophs, also known as consumers, that get their energy from the previous level.

food web

a model that shows many interconnected pathways through which energy and matter flow through an ecosystem

cellular respiration

a process that converts oxygen and sugar into chemical energy and carbon dioxide

food chain

a simplified model that shows a single path in which energy and matter flow through an ecosystem

invasive species

any kind of living organism that is not native to the ecosystem and causes harm

Heterotrophs

are organisms that consume other organisms in order to gain energy. They are also known as . An herbivore is a consumer that only eats plants. Cows and grasshoppers are examples of herbivores.

Food chains

are simple models that show the flow of energy (in the form of food) from one organism to another.

Which level would receive 10 percent of their energy from producers?

primary consumers—in this case, the grasshoppers.

That means that, for every 1 kilogram of a hawk

there has to be 1000 kilograms of producers to support it.

photosynthesis

the process in which the sun's light energy is converted into chemical energy for use by the cell

secondary consumer

An organism that eats primary consumers

To find the net primary productivity of the ecosystem, the following equation is used:

GPP−respiration(carbondioxide)=NPP

What would happen to the ecosystem if there were a greater number of primary consumers compared to producers?

The primary consumers could eat all of the producers, which would increase competition and could eventually decrease the primary consumer populations or cause them to relocate.

Explain what would happen if there was a population crash in sea otters.

The sea urchins feed on the kelp and the kelp population would decrease.

What stored energy is released when wood chips are burned?

The stored energy is released as heat when wood chips are burned.

consumer

an organism that eats other organisms or organic matter

producer

an organism that produces its own food

matter

anything that takes up space and has mass

A scientist is studying the health of an ecosystem by looking at the efficiency of energy transfer between a population of racoons and a population of field mice. They have found the following energy levels for each: Racoon - 63 Kcal Field Mouse - 450 Kcal Using the energy transfer formula, find the efficiency of energy transfer between the field mouse and the racoon in this ecosystem. Energy level transfered to next levelTotal energy input×100

63 Kcal (actual transfer)450 Kcal (total input)×100 The efficiency of energy transfer between the field mouse and the racoon is 14%.

primary productivity

the rate that plants and other photosynthetic organisms produce organic compounds

The 100 kilograms of grasshoppers can

then support 10 kilograms of bull snakes.

If stargrass is the producer in a food chain and has a total biomass storage of 150,000 Kcal of energy, how much energy will each of the following trophic levels have available?

zebra (primary consumer) - 15,000 Kcal of energy cheetah (secondary consumer) - 1,500 Kcal of energy lion (tertiary consumer) - 150 Kcal of energy

Compare and contrast food chains and food webs.

Food chains are simple models that show the flow of energy from one organism to another. A food web also shows the flow of energy in an ecosystem and is made from many food chains. This is more realistic in an ecosystem.

If energy decreases as you move up the energy pyramid, why would the biomass decrease as well?

If energy decreases, there is not enough energy to sustain more organisms. This means there are fewer organisms in higher trophic levels.

Describe how the law of conservation of mass relates to the flow of energy and matter in an ecosystem.

The law of conservation of mass states that matter is not created or destroyed. Matter is cycled through an ecosystem as organisms are consumed or decomposed.

heterotroph

an organism that cannot make its own food and receives its nutrients and energy by feeding on other organisms

Using the equation GPP

respiration(carbondioxide)=NPP, 200J/m2/day−100J/m2/day=100J/m2/day

1000 kilograms of plants can support

100 kilograms of grasshoppers.

Calculate the net primary productivity of an ecosystem that has a gross primary productivity of 50060J/m2/day and the respiration is 36922J/m2/day.

13,138J/m2/day

autotroph

an organism that captures energy to produce its own food and provide the foundation of the food supply for other organisms

Food webs

A complex diagram representing the many energy pathways in an ecosystem

omnivore

an organism that eats both plants and animals

Decomposers break down dead and decaying organisms and return their nutrients back into the ecosystem. What role would decomposers play in cycling matter within an ecosystem?

After an organism dies the matter will decompose into nutrients and mix into the soil. Plants and animals will use the nutrients from the soil to grow and reproduce. When those plants and animals die the cycle will repeat.

What is the approximate percentage of energy that is transferred from one organism to the next when consumed?

About 10 percent of the energy is available for the next organism when an organism is consumed.

secondary consumers

an organism that feeds on primary consumers, or herbivores

For the following situation, think about Ahmed's answer and his reasoning or explanation. Is his answer correct? Is his reasoning strong or could it be improved? Ahmed walked into his local market and said that it was a great representation of a food web. The people in the market going from stand to stand represent primary, secondary, and tertiary consumers.

Ahmed's reasoning is correct that a market could represent a food web, but his reasoning could be improved. Ahmed could explain further an example of the primary consumer buying vegetables in the produce department, and a secondary consumer buying beef in the protein department. He could have also stated that a market is an example of an interconnected set of diverse stands that interact with each other to meet the needs of the people inside. This is similar to a food web in that the food web is an interconnected set of species interacting with each other to meet the energy needs of all organisms inside the ecosystem.

Brayden states that energy flows through an ecosystem. Think about each statement below and decide which statement Brayden should include in his reasoning. Energy flow through an ecosystem is dependent on the types of organisms within the ecosystem. Energy is transferred between trophic levels. One way to follow the flow of energy in an ecosystem is to study the interactions of organisms and how they obtain energy. Energy flows in one direction.

All of these could be correct but the third option is the most comprehensive and correct.

Describe an energy pyramid and why it is used to model the energy in an ecosystem.

An energy pyramid is a model that shows the flow and amount of energy in an ecosystem. There is less energy available as you move up trophic levels and the pyramid becomes smaller as you progress; this may reveal the relationship between energy and trophic levels.

primary consumer

An organism that eats producers

tertiary—consumer

An organism that eats secondary consumers

Antonella wants to diagram a model of the flow of energy in a desert ecosystem. Will Antonella need to use a food chain or food web for the most accurate representation? Support your answer.

Antonella will want to use a food web to diagram the most accurate flow of energy in a desert ecosystem. Using a food web will more accurately show the interconnectedness of the ecosystem and how the same species can take up different roles in different food chains. It will provide a deeper look into the diversity of organisms in the desert and how they interact to meet their needs.

Explain how autotrophs obtain their energy from an ecosystem.

Autotrophs are producers and obtain their energy from the sun. They use this energy along with carbon dioxide and water to produce glucose.

Compare and contrast autotrophs and heterotrophs.

Autotrophs use matter and energy from their environment to make energy for life processes. Heterotrophs depend on other organisms for their matter and energy.

decomposer

an organism that gets energy by breaking down the remains of dead organisms or animal waste

What positive roles do bacteria play in the human body?

Bacteria support digestion, reduce inflammation, and fight infection.

Explain biomass and provide an example.

Biomass is the amount of organisms in an ecosystem; examples include wood chips.

Bob states that there is a decrease in some lemur populations, and these lemurs play an important role in their ecosystems. He explains that lemurs' waste contains seeds from trees, which allows more trees to grow. Bob states that if the lemur experiences a population crash, or decline, this could impact the diversity of the rainforest. Is Bob correct in his reasoning? If so, can his reasoning be made stronger? If he is incorrect, what is the correct reasoning?

Bob is correct in his reasoning. If there is a decrease in lemurs there can be a decrease in the amount of new tree growth. The different types of plants and trees is what gives the rainforest its high biodiversity.

How does critical thinking help students in science?

Critical thinking helps students to build their understanding of science and develop their ability to reason scientifically.

There are some things that scientists must consider when using biomass. Some of the food that may have been used to feed people may be used for fuel instead while transporting biomass is expensive and combustion of ethanol produces black carbon, which is linked to global warming. What are some of the disadvantages of using biomass?

Disadvantages of using biomass include releasing carbon dioxide, cutting down trees, and using food for fuel. Transporting the materials is expensive and using ethanol can add to global warming.

Explain what happens to the energy an organism does not use.

Energy not used for cellular processes is released as heat into the ecosystem. Energy decreases as you move up trophic levels. Only about 10% of the biomass energy is transferred from one trophic level to the next.

How does energy flow through an ecosystem?

Energy producers change light energy from the sun into chemical energy stored in the bonds of glucose. This energy is then transferred to other organisms, such as the animals that eat the plants in the ecosystem.

How can invasive species alter the availability of energy to native organisms in an ecosystem?

Invasive species can wipe out the producers in an ecosystem. This would limit the amount of energy that is left for the other organisms in the food web.

John states that an invasive species directly impacts a single ecosystem. Is his reasoning correct? If so, is there something that can make his reasoning stronger? If he is incorrect, what is the correct reasoning?

John is only partially correct in his reasoning. Invasive species can also indirectly impact ecosystems and alter food webs or change the diversity of any ecosystem.

Joseph states that there would be fewer producers if the sun began to produce less energy. Is Joseph correct? If so, how can his reasoning be stronger? If not, how can you correct his reasoning?

Joseph is correct. He can strengthen his reasoning by adding that consumers would have less producers to eat, which would impact the rest of the organisms that depend on the consumers.

How are energy and matter similar?

Matter and energy flow throughout an ecosystem. Energy is needed for matter to change forms. Energy is essentially a property of matter.

How does matter cycle through an ecosystem?

Matter cycles through an ecosystem as elements are transferred back and forth from organisms and their environments.

Explain why we have only known about the importance of microorganisms for a relatively short period of time.

Microorganisms are so small that they can only be seen by microscopes which were invented just a few hundred years ago.

Explain why only around 10 percent of energy in an energy pyramid is available for the next trophic level.

Only 10 percent of energy is available for the next trophic level because organisms use the remaining 90 percent for metabolic activities and the energy is given off as heat.

autotrophs

Organisms like plants use the energy from light and convert this into chemical energy in a process known as .

What is the process by which autotrophs convert light energy into chemical energy?

Photosynthesis

For the following situation, think about Sally's answer and her reasoning or explanation. Is her answer correct? Is her reasoning strong or could it be improved? Sally is comparing and contrasting food chains and food webs. She describes the strengths of each concept and states that both a food chain and food web follow a single path as energy is transferred.

Sally's reasoning is not accurate. Food chains show a single path of energy and a food web is more holistic with many paths of energy. Sally could also elaborate that food chains are more simplistic and easier to understand but less accurate than a food web.

Sam states that the burning of ethanol as an energy resource is a responsible way to reduce greenhouse gases being released into the atmosphere. Is Sam correct? If so, how could his reasoning be stronger? If not, how can his reasoning be corrected?

Sam's reasoning is not fully correct. While scientists are looking at biomass as a way to lesson the dependence on fossil fuels, the burning of ethanol is not complete and can release black carbon. This is a greenhouse gas that is responsible for global warming.

How do scientists calculate the net primary productivity, or the amount of organic material available to transfer to the next trophic level?

Scientists can use the gross primary productivity, or the total amount of organic material produced through photosynthesis, and subtract the organic material that is used for life processes such as respiration.

How does protecting the biodiversity of an area help sustainability?

Sustainability is the ability to provide humans with resources while maintaining a balance with the biosphere. If there are fewer resources due to a decrease of biodiversity there are fewer plants, animals, and resources for humans to depend upon.

A trophic level indicates which of the following? how much energy an organism produces how many producers grow each day the level where an organism is found in the food chain how much biomass is produced

The best answer is C. This is the definition of a trophic level.

Think about each statement below and decide which statement Arya should include in her reasoning. Humans can carry back invasive plants and animals when they travel. Invasive species can include seeds, eggs, or organisms. Invasive species can directly impact an ecosystem and the economy. There can be an indirect impact on the food webs in an ecosystem due to invasive species.

The best statement that would support Jason's observation is the first one. This supports human's impact on the dispersal of invasive species.

detritivore

a heterotroph that decomposes organic material and returns the nutrients to the soil, air, and water

What is the main reason that scientists are studying biomass energy sources?

The main reason that scientists are studying biomass as an energy source is to lessen the dependence on fossil fuels.

Observe the picture of wood chips. Describe what they look like. What purpose do the wood chips serve? How would the wood chips represent matter and energy in an ecosystem?

The wood chips are an example of biomass in an ecosystem. Biomass is the amount of organisms in a given area or volume in an ecosystem. Many types of biomass can be burned or digested to produce a type of energy. Examples of biomass that you may be familiar with include wood, agricultural products, solid waste, landfill gas, biogas, and alcohol fuels such as ethanol.

Why is a pyramid a great representation of biomass in the different trophic levels in an ecosystem?

There are fewer organisms in higher trophic levels since less energy is available. This is represented in the pyramid since the pyramid decreases in size nearing the top.

Why is there less energy as you move up the biomass pyramid?

There is less energy as you move up the biomass pyramid because only about 10 percent of energy is transferred to the next trophic level.

Suppose a plant is eaten by a mouse, the mouse is consumed by a snake, and the snake is in turn consumed by a hawk. What could be assumed about the level of available organic matter in the mouse versus the plant?

There will be less organic matter available.

How many kilograms of hawk would an ecosystem support that contained 1000 kilograms of producers?

There would be enough energy to support just one kilogram of hawk in an ecosystem with 1000 kilograms worth of producers.

How are herbivores, carnivores, and omnivores the same? How are they different?

They are all consumers; they cannot produce their own energy and need to consume it. Herbivores only eat plants and other autotrophs, carnivores only eat other consumers, and omnivores eat both autotrophs and consumers.

Using the 10 percent rule, how many kilocalories of energy would a hawk receive in the following forest food chain? Grass (220,000 Kcal) Grasshopper Frog Hawk

Using the ten percent rule, the energy at each trophic level is: Grass (220,000 Kcal) Grasshopper (22,000 Kcal) Frog (2,200 Kcal) Hawk (220 Kcal) The hawk would have 220 Kcal of energy.

Using the example of wood chips, describe where energy begins.

When wood chips start off as producers, energy is first absorbed as radiant or light energy for photosynthesis.

Why is there less biomass at the top of the energy pyramid?

Why is there less biomass at the top of the energy pyramid?

Which of the following would cause a decrease in the snake population?

a decrease in the mouse population

An example of calculating for NPP would be

a forest that has a GPP of 200J/m2/day and 100J/m2/day worth of carbon dioxide is used during cellular respiration.

tertiary (third) consumer

a top-level consumer that is a carnivore and feeds on secondary consumers

third (tertiary) consumer

a top-level consumer that is a carnivore and feeds on secondary consumers

law of conservation of mass

matter cannot be created or destroyed

Use the internet to find out how you can encourage the growth of beneficial gut flora (bacteria) in your intestines.

mention the fact that eating certain foods, such as vegetables, legumes, whole grains, and fermented items, can help increase beneficial gut flora. Other options include taking probiotic supplements.

The 10 kilograms of bull snakes is enough to support

one kilogram of a hawk in an ecosystem.

Carnivores

such as lions, are consumers that prey on other animals. Consumers that eat both plants and animals are known as . Most humans are omnivores.

net primary productivity

the adjusted amount of energy in an ecosystem due to energy use by organisms for respiration

gross primary productivity (GPP)

the amount of organic, carbon-based material that is produced by photosynthesis

biomass

the amount of organisms in a given area or volume

biomagnification

the increase of toxic substances that have accumulated in organisms, which increases at each trophic level

net primary productivity (NPP)

the measure of the amount of organic material produced minus the amount of organic material used during life processes such as respiration

biodiversity

the number of organisms that an area has at any given time

Microorganisms

the oldest creatures on Earth—they have existed for over three billion years—and they are very diverse. In fact, there may actually be trillions of different microorganism species on Earth. Microorganisms can live in a huge range of environments, including those that are hostile to other forms of life.

keystone species

the organisms an ecosystem heavily depends on to keep its balance

gross primary productivity

the overall amount of energy captured by plants and other photosynthetic organisms