Fundamentals of Ecosystems and Food Webs

Biology Unit 1 Study Guide ANSWER KEY Choose and answer 10 questions from each Learning Set. Like always, please type your answers in another visible color. You do not have to answer all of the questions, but you will be extra ready for the test if you do! I gave you MANY questions so you have MANY to choose from. Learning Set 1: Ecosystems and Food Webs 1. What is ecology? Ecology is the study of how organisms interact with one and the environment. 2. A community of various organisms interacting with each other within a particular physical environment is known as an _ecosystem________. 3. What makes an ecosystem sustainable? An ecosystem is sustainable if it can support its diversity and ecological processes through time. 4. Give an example of one species that is impacted by ecological change and how. The coral reefs are impacted by climate change because they are being bleached. This is a process caused by an increase in the temperature of the surrounding water. 5. Name at least 3 biomes and describe their characteristics within the ecosystem. Deserts have low precipitation of 15–300 mm (about 0.5–12 inches) per year. The low humidity allows temperatures to become cold at night. Hot deserts experience temperature variations from an average of about 10°C (50°F) in winter to 35°C (95°F) or more in the summer. The soil is often poor in nutrients but rich in minerals. To survive in the desert, plants and animals must be able to conserve water. Desert plants generally provide very little shade, and there are very few trees. Temperate grassland experiences a wide range of temperature and precipitation through the year. Precipitation is moderate with a yearly average of 500–900 mm (about 20–35 inches). Most rain falls in late spring and in summer. The winter is cold, with average temperatures well below freezing, while summer temperatures average around 25°C (77°F). Five to six months of the year are frost free. The soil is often fertile and dominated by tall grasses that have adapted to the cold winter temperatures, occasional summer droughts, and periodic fires. The roots of these grasses help to hold the soil together. Many large mammals graze in these grasslands. Very cold temperatures and low precipitation, with yearly totals between 120 and 250 mm (about 5–10 inches), are characteristic of tundra. Winters are long with average temperatures of –30°C (–22°F) or lower. The soil is thin and covers a permanently frozen layer of subsoil called permafrost. The permafrost makes it difficult for plants to extend roots deep into the ground. The permafrost also prevents water from seeping deep into the ground during the short summer when the soil at the surface thaws. Animals usually have fat and fur to help cope with the cold temperatures. Some animals hibernate to survive the harsh winters, and some migrate. Average summer temperatures can reach 10°C (50°F). The growing season for plants is very short with only about two months of the year being frostfree. Plants that do well in tundra tend to grow close to the ground. 6. What is the difference between abiotic and biotic factors in an environment? Abiotic factors are nonliving things like light, temperature, precipitation, soil, rocks, and minerals. Biotic factors are living things like organisms, their interactions and their waste. 7. What are the three types of desert biomes? Are their climates all the same? If not, describe the climate that is not like the others. The three types of biomes are semi arid, coastal and cold deserts. Their climates are not all the same. In the semiarid desert, the summers are warm to hot, quite long, and dry, but the winters bring some precipitation. In the coastal desert, the summers are warm and the winters cool. Precipitation is low but not as low as in the semiarid desert. In the cold desert, the temperatures are very cold in winter and summers are short, warm, and moist. Winter precipitation includes snow. 8. .Do the traits that an organism has guarantee their survival in a new environment? Why or why not? No, because they have to still be able to easily acclimate to the new environment. If they are unable to adapt well to the new environment they will die off and not succeed in becoming invasive. 9. What are the criteria in order for a nonnative species to be considered invasive? The species must have been brought into an environment in which it does not naturally occur and cause harm to the native species or the environment. 10. What is a native species? A nonnative species is considered native if it causes harm to the environment, the economy, or human health or it displaces a native species from its habitat. 11. How are invasive species introduced into a new environment? Give an example for both ways. Invasive species are either introduced accidentally or intentionally. An accidental way they could be introduced is by a boat crash that was importing a species to another country. An intentional way they could be introduced is by scientists bringing a new predator into an ecosystem in order to control another invasive or overpopulated prey species. 12. Do all nonnative species become invasive? Why or why not? No, because to be classified as invasive there must be harm done to displace native organisms, disrupt the balance of the ecosystem, or possibly reduce the biodiversity and sustainability of the area. 13. Give an example of a trade off that scientists may encounter when performing damage control within an ecosystem. In order to control an invasive prey population, scientists must introduce a new predator to the ecosystem. This predator also eats native prey organisms in the ecosystem that are close to endangerment. The trade off they face is that if they do not bring in the predator into the ecosystem, the invasive prey will continue to populated and destroy the ecosystem, but if they do bring the predator into the ecosystem, the native prey population will suffer and they could possibly go extinct. 14. Explain the Tragedy of the Commons and how the theory negatively impacts our ecosystems? The Tragedy of the Commons Theory states that the more people there are who have unrestricted access to a common resource, the more they will exploit it. Oftentimes, individuals will do this without considering the consequences for others who may need or have access to the resources or without thinking of the long term implications. Therefore, there are limits on common resources created by societies, usually laws with fines, in order to prevent them from diminishing. 15. What do food web diagrams show about the relationships between organisms in an ecosystem? Food webs are maps of what each organism eats and how the energy flows through an ecosystem. 16. What do energy pyramids show about the relationships between organisms in an ecosystem? Energy pyramids are shaped to represent the energy present at each trophic level in the food web. They show the amount of energy that passes from one organism to another, and from one consumer level to another. 17. Reflect back to the kelp forest ecosystem, give one reason why the giant kelp population is necessary for the sustainability of the ecosystem. The kelp are tall, with long leaf-like structures that create a canopy that blocks the light at lower ocean depths, providing habitat and nourishment for the organisms that thrive in limited light conditions. The kelp grows in clusters with each plant shooting upward to the surface, then spreading out and sheltering thousands of organisms in a complex ecosystem. 18. Name the three trophic levels and who they eat within the food web. The trophic levels, representing the positions that the organisms play in a food web, are called primary consumers, secondary consumers, and tertiary consumers. The primary consumers eat the producers directly, the secondary consumers eat the primary consumers, and the tertiary consumers eat the secondary consumers. Some organisms can fill more than one trophic level. 19. Name the three trophic roles within an ecosystem. The producers transform light energy or other energy sources into chemical energy that is stored in carbon containing molecules, such as simple sugars or starch. The consumers feed on other organisms to obtain energy. The decomposers feed on other organisms and dead and decaying biological material and wastes to obtain energy. 20. What does CER stand for? CER stands for Claim, Evidence, and Reasoning. Learning Set 2: Cycling of Matter in a Ecosystem 1. What is carbon? Where is it found? Carbon is the chemical backbone of life on Earth. It is found in all living (organic matter) things on Earth. It can be found in rocks, oceans, and the atmosphere. Carbon compounds regulate the Earth’s temperature, make up the food that sustains us, and provide energy that fuels our global economy. 2. List and describe each of the steps in the carbon cycle. Explain its importance within an ecosystem. Carbon begins in the atmosphere and is used by plants to create food where the carbon enters the food chain. It is then eaten by humans and animals and released back into the atmosphere by respiration and the burning of fossil fuels. 3. How are plants involved in the carbon cycle? Explain their role. Plants pull carbon dioxide from the atmosphere into the biosphere, using it to make food through the process of photosynthesis. When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies. 4. How are animals involved in the carbon cycle? Explain their role. All Animals that eat plants digest the sugar molecules to get energy for their bodies. Respiration, excretion, and decomposition release the carbon back into the atmosphere or soil, continuing the cycle. When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere. 5. How are humans involved in the carbon cycle? Explain our role. The burning of fossil fuels since the start of the industrial revolution has dramatically increased the levels of carbon in the atmosphere, like cars using gasoline. When humans consume plants and animals we add to the cycling of matter. 6. List and describe each stage of the nitrogen cycle. Explain its importance within an ecosystem. In stage 1, fixation, nitrogen is too unreactive to be used directly by plants to make protein. It must be converted into soluble ions, such as nitrates. Nitrogen-fixing bacteria in root nodules help convert nitrogen in the air into Nitrates. Lightning can also convert nitrogen gas into nitrates. The Haber process converts nitrogen gas into ammonia for use in fertilizers. Nitrifying bacteria in the soil can also convert ammonium ions into nitrates. In stage 2, nitrification, the absorption of nitrates into roots and incorporation into plants occurs. In stage 3, assimilation, nitrates are moving along food chains and excretion. When an animal eats a plant, nitrogen from the plant’s proteins becomes proteins in the animal. In stage 4, ammonification, the death of animals occurs. Decomposers break down urea, digested material (feces) and dead bodies. This results in nitrogen being returned to the soil as ammonium ions, which nitrifying bacteria can convert into nitrates for plants to absorb. In stage 5, denitrification, the release of Nitrogen back into the atmosphere occurs.. Denitrifying bacteria in the soil break down nitrates and return nitrogen gas to the air. 7. How are plants involved in the nitrogen cycle? Explain their role. Plants absorb nitrates from the soil and use these to make proteins. When an animal eats a plant, nitrogen from the plant’s proteins becomes proteins in the animal. Plant production and biomass (living material) are limited by the availability of nitrogen. If we understand how the plant-soil nitrogen cycle works, we can make decisions about what crops to grow and where, improving our supply of food. 8. How are animals involved in the nitrogen cycle? Explain their role. Nitrogen is passed from one animal to another by feeding. Excess nitrogen can poison plants and even livestock. 9. How are humans involved in the nitrogen cycle? Knowledge of the nitrogen cycle can also help us reduce pollution caused by adding too much fertilizer to soils. 10. What is the process of cellular respiration and what organisms use it? Cellular respiration is the process by which cells release stored energy from sugars. Plants and animals used cellular respiration. 11. What is the process of photosynthesis and what organisms use it? Photosynthesis is the process in which producer cells use carbon dioxide, water, and nutrients to produce glucose and oxygen. Plants use photosynthesis to make food for the plant (food in the form of glucose, a type of sugar). 12. Name the 3 raw materials used and the 3 waste products created in cellular respiration. Glucose and oxygen are raw materials used in cellular respiration; carbon dioxide and water are the waste products created. 13. Name the 2 raw materials used in photosynthesis. Carbon dioxide, water, and sunlight are raw materials used in photosynthesis; oxygen and glucose are the waste products created. 14. What are the 2 by products created from cellular respiration and the molecule they make together? The two byproducts are carbon dioxide and water; the molecule they make is ATP. 15. The photosynthesis and cellular respiration process form a combined cycle called _carbon dioxide oxygen cycle_____. 16. Why is the sugar and yeast experiment a good model of eutrophication in our ecosystems? It represents how nutrient rich waters can create toxic gasses when mixed with nutrients and an organism that converts these gasses. Yeast is a live organism that when mixed with the sugar and warm water, causes the balloon to fill up with gas, just as it does in our oceans. 17. How are dead zones created? Give an example of an organism that contributes to this process. When a large amount of nutrient rich water flows into an area, causing an increase in plant growth eutrophication occurs. The conditions are prime for a deadzone to develop. 18. Name 2 human related impacts of eutrophication. Human related impacts of eutrophication include fertilizer runoff from agricultural areas or farm, 19. sewage spills, vehicle exhaust, the storm water runoff that picks up sources of nitrogen, phosphorus and other nutrients. 20. What happens to the concentration of nutrient loving organisms when the water temperature is colder? Warmer? In colder conditions, there is a lower concentration of nutrient loving organisms and in warmer conditions, there is a high concentration of nutrient loving organisms. This is because high temperatures give the organisms more energy and there will be a high concentration of nitrogen created in these areas as well. 21. Why is it easier for scientists to prevent eutrophication than it is to control it? Once the process has already started, it is extremely difficult to control because of its vast coverage of damage in a short period of time, so therefore further prevention is used, as well as, working to curb overfishing and pollution. Learning Set 3: Species Interactions and Human Impact 1. Name the three types of symbiotic relationships and describe their interaction. Amensalism is a symbiotic relationship in which one species is harmed, while other species neither benefit nor are harmed. It appears to be rare, but it is common among organisms that excrete toxic chemicals. Commensalism is a symbiotic relationship in which one species benefits, while other species does not benefit nor is harmed. Parasitism is a symbiotic relationship in which one species benefits, while other species are harmed, but not killed. 2. Give an example of two organisms in a symbiotic relationship and how they interact with each other. With the clownfish and anemone, the anemone protects the clownfish from predators, while the anemone is unaffected by its habitation there. 3. The size of a particular population that an ecosystem can support is called _carrying capacity______. 4. What is the difference between exponential growth and logistical growth? Exponential growth is when the individuals in a population reproduce at a constant rate. While logistical growth has a carrying capacity. As resources become less available, the growth of a population slows or stops. 5. What are the 3 characteristics of a population? Three characteristics of a population are geographic distribution, density, growth rate. 6. How do graphs help scientists record, track, and study population growth within an ecosystem? The table conveys additional information about births and deaths and their contribution to the overall population numbers. Using the table, the graph displays the final population at intervals of time and is easier to interpret. 7. What is a limiting factor? Give 2 examples. A limiting factor is a factor that causes population growth to decrease. Examples include competition, predators, parasitism, weather, and human activity. 8. What happens to the death rate when the birth rate is higher? The population can grow. 9. What happens to the birth rate when the death rate is higher? The population is likely to shrink. 10. What happens in an ecosystem when the birth rate is equal to the death rate? The population may stay the same. 11. What is the Average Growth Rate when a population is at its carrying capacity? The average growth rate is zero at carrying capacity. This is determined by the resources available and other species present in the ecosystem.