Bio Unit 2 Review

When your running a marathon, you tend to have a steady pace for most of the run. Towards the end, many runner sprint to the finish. What type of respiration is your body using for the longer steady pace? What type is your body using for the power sprint?

Aerobic during steady pace, anaerobic during sprint.

Explain the role of producers, consumers, and decomposers in an environment

Carbon is continually moving between living and nonliving things on Earth through the processes of photosynthesis, cellular respiration, digestion of plant matter, decomposition, and combustion. These processes move and exchange carbon between the biosphere, atmosphere, hydrosphere, and geosphere and these movements make up the carbon cycle. Producers, consumers and decomposers are the instigators of the transitions.

Using the diagram, explain how the light-dependent and light-independent reactions help with glucose production

In light-dependent reactions, light photons (units of light energy) are absorbed and converted to ATP. This takes place in thylakoids, a series of flat, stacked disks located in chloroplasts. Thylakoids are bound inside a thylakoid membrane, along with the green pigment, chlorophyll. Chlorophyll gives green plants their characteristic color. When light energy hits the thylakoid membrane, it is used to excite electrons in the photosystems and to split water. When the water molecules are split, the oxygen diffuses into the atmosphere. The electrons enter the electron transport chain, and the hydrogen ions exit the thylakoid membrane, where they are picked up and transported to the Calvin cycle on NADPH, a carrier protein molecule. Cellular Energy 3 Cellular Energy In the light-independent reactions, carbon dioxide and the products of the light-dependent reaction (ATP and NADPH) undergo a series of reactions known as the Calvin cycle . The Calvin cycle produces glucose as its end product. The combination of the light-dependent and light-independent reaction results in the overall equation for photosynthesis. Now, glucose is available to be converted into the energy needed for cellular processes in the autotroph. Glucose contains chemical energy found in the bonds of the molecule. This energy can be released when these bonds are broken and new molecules are produced. Glucose must now go through an additional process to release that stored energy into a usable form for the organism. This brings us to cellular respiration. It is important to remember that both autotrophs and heterotrophs use cellular respiration to create the necessary energy from glucose.

What are similarities and differences between different biomolecules? What atoms make up each?

Lipids Carbohydrates Protein Nucleic Acids

Explain why matter is recycled through a food chain/web.

Living things need nonliving matter as well as energy. What do you think matter is used for? It's used to build bodies. It's also needed to carry out the processes of life. Any nonliving matter that living things need is called a nutrient. Carbon and nitrogen are examples of nutrients. Unlike energy, matter is recycled in ecosystems. In the figure below, you can see how (Figure below). Decomposers release nutrients when they break down dead organisms. The nutrients are taken up by plants through their roots. The nutrients pass to primary consumers when they eat the plants. The nutrients pass to higher level consumers when they eat lower level consumers. When living things die, the cycle repeats.

Why is there less apex predators in a food chain compared to the abundance of producers?

Only a fraction of the energy available at one trophic level is transferred to the next trophic level. The rule of thumb is 10%, but this is very approximate. Typically the numbers and biomass of organisms decrease as one ascends the food chain.

In words, explain how energy is transferred through the food web.

Producers receive chemicals from light rays, 1st-level consumers eat producers, 2nd-level consumers eat 1st-level consumers, and 3rd-level consumers eat 2nd-level consumers. Food webs are several food chains.

Which pathways (aerobic or anaerobic) produces more ATP (energy)? Why?

Recall that cellular respiration can take place in the presence or absence of atmospheric oxygen. When oxygen is present, aerobic respiration takes place. When oxygen is lacking, anaerobic respiration takes place. Most organisms can perform aerobic and anaerobic respiration, however, some can only perform one or the other. Aerobic respiration is more efficient at producing ATP. In fact, aerobic respiration produces 36 ATP with one glucose molecule. So, organisms that can perform both processes will most often use the aerobic pathways. However, when oxygen is lacking and organisms need more ATP, cells can undergo anaerobic respiration.

How does going on a low carbohydrate diet affect your energy? How do you get energy when on a low carbohydrate diet?

So how does your body respond when you have few carbohydrates in your system? Your cells are continually working and need a constant supply of energy, but if there is no sugar available, do your cells shut down? The answer is no. Since the lipids and proteins are composed of elements similar to glucose, the body is able to process these to produce energy. The actual chemical reactions are different, but the overall result is that the cell has the energy needed to perform all required processes.

Explain how the carbon cycle in recycled through Atmosphere

The atmosphere is a layer of gases that surrounds Earth and carbon is found in the form of carbon dioxide or methane (CH 4) . Both of these molecules are contributors to the greenhouse effect (figure 5) because they absorb and keep in the heat that radiates from the sun and in turn, warm Earth. Carbon gases absorb into water molecules and are transferred between the surface of Earth by precipitation and back into the atmosphere by transpiration and evaporation (figure 6). Carbon dioxide is readily used and absorbed by all the autotrophs in the biosphere and hydrosphere that rely on atmospheric carbon dioxide for photosynthesis. Humans contribute to the carbon cycle by burning fossil fuels that have been extracted from the geosphere as well as burning other forms of biomass, such as wood. Biomass also burns through natural processes. For example, a bolt of lightning can spark a forest fire. However, over the past few centuries, humans have released large quantities of carbon into the atmosphere—more than can be absorbed through photosynthesis and other natural processes. Scientists have evidence that this excess of carbon dioxide in the atmosphere is trapping heat at Earth's surface, leading to global climate change.

Explain how the carbon cycle in recycled through Biosphere

The biosphere is the sphere of Earth where life exists and it ranges from the air the birds fly in above your head, to the soil under your feet, and even deep into the ocean where organisms can be found near geothermal vents! Carbon can be found in many forms throughout the biosphere. As you have learned, carbon can be found in the form of carbon dioxide (CO 2) , which is the molecule that is exchanged between the processes of photosynthesis and cellular respiration. During photosynthesis, autotrophs convert carbon dioxide from the atmosphere into the carbohydrate glucose (C 6H 12O 6) . Plants can use the glucose directly to produce energy, or ATP, for the cell. This process gives CO 2 back into the atmosphere. However, all living organisms need energy and carbon in their cells. Organisms that must consume other organisms because they cannot produce their own food are called heterotrophs . Carbon and other vital nutrients and matter are transferred when a heterotroph consumes another organism. Now these heterotrophs are able to produce energy in their cells using the glucose they have consumed. This process also produces CO 2 as a byproduct which is released back into the atmosphere. Carbon Flow in Ecosystems Forests and places with an abundance of autotrophs can be areas where there is an accumulation of carbon. Areas that are able to take out more carbon from the atmosphere than is released are known as carbon sinks such as that seen in figure 7. Dense forests are an example of a carbon sink because of the large amount of photosynthesis taking place. These carbon sinks help to regulate the amount of carbon dioxide in the atmosphere. Deforestation has cut down many of these forests that were once carbon sinks, which has possibly led to an increase in atmospheric CO 2. Another way carbon is cycled through Earth's spheres is through decomposition. When organisms produce waste or die, bacteria start to decompose the decaying matter. This decomposition returns CO 2 back into the atmosphere as well as to the surrounding soil.

In the diagram, where is carbon stored? Where is it cycled? How can removing one thing affect the rest of the cycle?

The carbon is stored in the longterm int he geosphere and hydrosphere. As previously mentioned, ecosystems thrive when conditions are balanced. The carbon cycle is crucial to maintaining this balance. Disruptions to this cycle can have devastating effects on an ecosystem. Unfortunately, disruptions occur too often due to human activities. The total amount of carbon actively moving through the carbon cycle decreases when people bury organic materials in landfills rather than allow them to decompose naturally outdoors. Ideally, fallen leaves and discarded food should be used for compost, which allows nutrients in the decomposing biomass to return to the ecosystem. Carbon Flow in Ecosystems A much larger problem, however, is excessive carbon in the atmosphere. Recall that burning fossil fuels releases carbon dioxide gas into the air. In the last 150 years, there has been a dramatic increase in the burning of coal, oil, and natural gas for factories, cars, airplanes, and other technologies invented by humans. Not only does this excessive consumption of fossil fuels deplete Earth of its natural resources, but it also pollutes the air and creates imbalance in the carbon cycle. During the last few decades, governments and individuals in the United States and other countries have worked to reduce the amount of CO 2 emissions from refineries, factories, and automobiles. Additionally, efforts are being made to make homes and office buildings more energy-efficient with "green" technology.

Be able to explain how the carbon cycle in recycled through Geosphere

The geosphere is composed of the crust and core of Earth. Most of Earth's carbon is stored in the geosphere in rocks, fossil fuels, and magma. The carbon found in the geosphere comes from the sedimentation and burial of once-living organisms as well as from the shells of marine organisms. Over time, heat and pressure cause the sedimentation to form the rocks and magma found in the geosphere. During a volcanic eruption, magma makes its way to Earth's surface and releases carbon back into the atmosphere as seen in figure 9. Fossil fuels, such as coal, oil, and natural gas, are found and stored deep within the geosphere. The type of fossil fuel depends on the source of carbon. For instance, coal is formed from dead plants and trees that have sunk to the bottom of swamps and over a long period of time have transformed into peat, and then eventually coal. Oil and natural gas reserves were formed from buried microscopic animals that lived millions of years ago. Over time, the pressure from rocks turned this organic matter into oil and natural gas. It is important to note that fossil fuels have taken millions of years to form and continue to form naturally at a very slow rate. Humans extract these fossil fuels from the geosphere for energy to power their cars and homes. As stated before, the burning of these fossil fuels returns carbon back into the atmosphere.

Explain how the carbon cycle in recycled through Hydrosphere

The hydrosphere includes all the water on Earth's surface. This can range from oceans to lakes and rivers. Carbon dioxide is continually being exchanged between the surface of these water sources and the atmosphere through photosynthesis and cellular respiration from the organisms closest to the surface. Since CO 2 is easily dissolved in water, it does so freely, and oceans are also considered large carbon sinks because of all the carbon dioxide that is absorbed and held in them (figure 8). A lot of the carbon dioxide that is absorbed from the atmosphere may be converted into calcium carbonate (CaCO 3) or bicarbonate (HCO 3- ) that many ocean animals rely on. Carbon from these molecules is used to create the coral reefs and to produce the shells in the ocean. When these organisms die, they sink and form large carbon deposits on the ocean floor. Over time, the pressure at the bottom of the ocean causes these carbon deposits to form sedimentary rock and become part of the geosphere. Carbon Flow in Ecosystems Does life only exist at the surface of oceans where light penetrates through the water? The answer is no. There is a vast amount of biodiversity at the bottom of the ocean floor, especially around hydrothermal vents. These vents are openings in the bottom of the ocean floor where superheated, mineral-rich water flows out. This water is heated by the magma in the geosphere and is located in areas where there is a large amount of volcanic activity. Organisms in this environment have adapted the means to convert the chemicals from the hydrothermal vents into carbohydrates needed for life. This process is known as chemosynthesis and normally uses hydrogen sulfide (H 2S ) from the hydrothermal vents to produce glucose.

What happens to stored lipids when you diet to lose weight? Use the figure provided.

There is a breakdown of the cells in storage to combine with sugar to use as energy.

How does glucose affect carbon dioxide (CO2) production during anaerobic respiration (fermentation)?

When there is a lack of oxygen, humans and animals will undergo lactic acid fermentation. Without oxygen, glycolysis can still take place, producing pyruvic acid. Recall that glycolysis is the first step to cellular respiration and oxygen is not a required reactant. In a low-oxygen environment, pyruvic acid can be turned into lactic acid as an alternate pathway for making small amounts of ATP. For example, when a person exercises strenuously (figure 4) and the muscles' demand for oxygen exceeds the body's ability to deliver the oxygen, lactic acid is produced in the muscles as the body tries to keep up with ATP requirements. The burning sensation that is often felt in muscles that are exerted is caused by the presence of lactic acid. This process breaks down glucose into two three-carbon molecules and two ATP molecules. Some organisms, such as certain kinds of bacteria and fungi, live without oxygen under normal circumstances. They produce energy through fermentation, converting a carbohydrate, such as a sugar or a starch, into alcohol or acid. The specific products of fermentation depend on the organism. For example, bacteria convert carbohydrates into lactic acid, and yeasts convert sugar into alcohol. Fermentation is used in the food industry to produce yeast breads and fermented alcohols, such as wine and beer .

Why is anaerobic respiration still important for an organism to be able to do?

anaerobic respiration produces only two ATP molecules. This process will allow organisms to produce the needed energy, however, cells will have to work much harder and longer to produce the needed amount of energy for cellular processes. Certain kinds of organisms only produce anaerobic repiration. Some organisms, such as certain kinds of bacteria and fungi, live without oxygen under normal circumstances. They produce energy through fermentation, converting a carbohydrate, such as a sugar or a starch, into alcohol or acid. The specific products of fermentation depend on the organism. For example, bacteria convert carbohydrates into lactic acid, and yeasts convert sugar into alcohol. Fermentation is used in the food industry to produce yeast breads and fermented alcohols, such as wine and beer . Fermentation is used for more than just food. Scientists grow bacteria and yeast in large tanks called fermenters . The bacteria and yeast cells are genetically engineered to produce human therapeutic proteins. The proteins are then purified away from the cells. For example, bacteria are used to produce insulin, which is a treatment for diabetes. Yeasts are used to produce erythropoietin, which can stimulate red blood cell production for treating anemia. This approach allows scientists to produce large batches of therapeutic drugs to treat human diseases.