IB Biology - Ecology Test Review

Sunlight is the initial source of energy in an ecosystem because it is the primary driver of photosynthesis. Plants and other photosynthetic organisms use sunlight to convert carbon dioxide and water into glucose and oxygen. This glucose serves as a source of energy for these organisms, and it is also passed on to other organisms in the food chain. Therefore, sunlight is crucial for the functioning and survival of all organisms in an ecosystem.

This statement is true because the food chain typically starts with producers, such as plants, that convert sunlight into energy through photosynthesis. Primary consumers, such as herbivores, feed on the producers, while secondary consumers, such as carnivores, feed on the primary consumers. Tertiary consumers, and so on, continue the chain by feeding on the previous consumers. This hierarchical structure of energy transfer through different trophic levels is a fundamental concept in ecology.

Water vapor is created through the process of evaporation. Evaporation occurs when water molecules gain enough energy to break free from the liquid phase and become a gas. This process can happen from various sources of water, such as oceans, lakes, rivers, and even moist soil. When the sun's heat energy is absorbed by water bodies or surfaces, it causes the water molecules to move faster and eventually escape into the air as water vapor. Therefore, evaporation is the correct answer as it accurately describes the creation of water vapor.

The 3rd and 4th most significant greenhouse gases are methane and nitrous oxide. These gases contribute to the greenhouse effect and global warming. Methane is released during the production and transport of coal, oil, and natural gas. It is also emitted by livestock and other agricultural practices. Nitrous oxide is mainly produced by agricultural and industrial activities, including the use of synthetic fertilizers and the burning of fossil fuels. Both methane and nitrous oxide have a much higher warming potential than carbon dioxide, although carbon dioxide remains the most abundant greenhouse gas.

All of the above causes ozone depletion. Burning of fossil fuels releases pollutants such as chlorofluorocarbons (CFCs) which rise to the stratosphere and break down ozone molecules. Forest and grassland fires release large amounts of carbon monoxide and nitrogen oxides, which also contribute to ozone depletion. Combustion processes in industries and transportation release pollutants that can react with ozone and deplete it. Therefore, all three factors - burning of fossil fuels, forest/grassland fires, and combustion - contribute to ozone depletion.

Peat is indeed partially decomposed plant material and can be used as a fossil fuel. Peat forms when organic matter, such as dead plants, accumulates in waterlogged environments, preventing complete decomposition. Over time, the accumulated organic matter undergoes partial decomposition and forms peat. Peat can be used as a fossil fuel because it contains energy-rich carbon compounds that can be burned to release heat and energy. However, it is important to note that peat is considered a non-renewable resource and its extraction and combustion contribute to carbon dioxide emissions and environmental degradation.

Only 10% of energy will be passed to the next trophic level on the food chain. This is because energy is lost as heat during metabolic processes and is also used for the organism's own growth and maintenance. As a result, only a small fraction of the energy obtained from the previous trophic level is available for consumption by the next level. This phenomenon, known as the 10% rule, explains why there are typically fewer organisms at higher trophic levels and why energy becomes more scarce as it moves up the food chain.

Biomass is the total mass of a group of organisms. In this case, the answer is "biomass" because it is the correct term that refers to the total mass of a group of organisms. The repetition of "biomass" in the question emphasizes its importance and reinforces the correct answer.

Chlorofluorocarbons (CFCs) are a type of chemical compound that contain chlorine (Cl) atoms. These chlorine atoms can react with ozone (O3) molecules in the stratosphere, leading to the destruction of ozone and the formation of holes in the ozone layer. Therefore, the correct answer is CFC, Cl, ozone.

Water vapor is removed from the atmosphere through a process called precipitation. Precipitation occurs when water vapor in the atmosphere condenses into liquid or solid form and falls to the Earth's surface as rain, snow, sleet, or hail. This process helps to balance the water cycle by removing excess moisture from the atmosphere and replenishing the Earth's water sources.

The given answer is the correct equation for photosynthesis. During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen, using energy from sunlight. This equation represents the overall process of photosynthesis, where glucose is produced as a source of energy for the plant, and oxygen is released as a byproduct.

The statement that "chemical energy flows through the food chain by the means of killing" is incorrect. Chemical energy actually flows through the food chain by the means of consumption and transfer of nutrients from one organism to another. Organisms obtain energy by consuming other organisms or plant matter, not necessarily by killing them. This energy transfer occurs through processes like photosynthesis and cellular respiration, which are essential for sustaining life in an ecosystem.

Water vapor and carbon dioxide are the two most significant greenhouse gases because they have the highest concentration in the Earth's atmosphere and contribute the most to the greenhouse effect. Water vapor is the most abundant greenhouse gas, and although it has a short lifespan in the atmosphere, it plays a crucial role in regulating the Earth's temperature. Carbon dioxide, on the other hand, has a longer lifespan and is primarily released through human activities such as burning fossil fuels and deforestation. Both gases trap heat in the atmosphere, leading to global warming and climate change.

Molluscs and Coral Reefs have exoskeletons made out of Calcium Carbonate. Molluscs, such as snails and clams, have a hard outer shell composed of Calcium Carbonate that provides protection and support. Coral reefs, on the other hand, are formed by tiny marine animals called polyps that secrete Calcium Carbonate to build their exoskeletons, which form the structure of the reef.

Living organisms cannot perform the conversion of chemical energy to cool energy. While living organisms can convert chemical energy to other forms of energy such as mechanical energy (muscle contractions), electrical energy (chemical to electrical energy), and electrochemical energy (nerve impulses), they do not have the ability to directly convert chemical energy into cool energy. Cool energy is typically achieved through processes such as evaporation or heat transfer, which are not within the capabilities of living organisms.

Cellular respiration is a fundamental process in living organisms where glucose (a type of sugar) is oxidized in the presence of oxygen. This reaction releases energy that cells can use for various functions. The byproducts of this process are carbon dioxide (CO2) and water (H2O). This question requires students to have a good understanding of the chemical equation for cellular respiration and the role of oxygen in the process.

Organic matter does not explode and turn into gas when heated to its ignition temperature in the presence of oxygen. Instead, it undergoes a process called combustion, where it reacts with oxygen to produce carbon dioxide, water, and other byproducts. The combustion process releases energy in the form of heat and light, but it does not cause an explosion. Therefore, the given statement is false.

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll. This process converts light energy into chemical energy in the form of glucose (a sugar) using carbon dioxide and water. Oxygen is released as a byproduct of this process.  

Cold-blooded organisms can become more active because they rely on external sources of heat to regulate their body temperature. When the environment is warmer, their metabolic rate increases, allowing them to perform activities such as hunting, feeding, and mating more efficiently. In contrast, when the environment is colder, their metabolic rate decreases, leading to reduced activity levels. Therefore, the heat generated from cellular respiration can have a direct impact on the activity levels of cold-blooded organisms, making them more active.

Carbonic acid is formed when carbon dioxide (CO2) dissolves in water (H2O). The carbon dioxide reacts with water to form carbonic acid (H2CO3). Therefore, the correct answer is carbon dioxide and water. Oxygen and carbon are not components of carbonic acid.

All definitions can be found on the first handout of notes.

Methanogenesis, the process of producing methane, occurs in various anaerobic environments. These include the mud along shores in the bed of lakes, swamps, and the guts of termites and ruminant animals. In these environments, the absence of oxygen allows for the growth and activity of methanogenic microorganisms, which convert organic matter into methane gas. These environments provide the necessary conditions, such as the presence of organic material and the absence of oxygen, for the methanogenesis process to take place.

Partially decomposed peat can be transformed into coal when it is subjected to weight, pressure, and heat from above sediments. These three factors work together to compress and heat the peat over time, causing it to undergo chemical changes and transform into coal. The repetition of the words "weight, pressure, heat" in the answer is likely a typographical error or duplication.

In living organisms, energy is released from carbon compounds through the process of respiration, specifically cellular respiration. This energy is then converted into heat energy.

Methane can be oxidized by both carbon dioxide (CO2) and water (H2O). When methane reacts with oxygen (O2) in the presence of a catalyst, it produces carbon dioxide and water as byproducts. This process is known as complete combustion. Therefore, both CO2 and H2O are correct answers as they are the products of methane oxidation.