Preparing for the AP Environmental Science Unit 1 Exam? You’ve come to the right place! Unit 1 of AP Environmental Science dives into the fundamental principles of ecology, exploring the intricate web of life on Earth and the systems that sustain it. This study guide and practice test will help you solidify your understanding of key concepts, from symbiotic relationships to biogeochemical cycles, ensuring you’re well-prepared for your exam. Let’s delve into the essential topics you need to master.
Question 1
A symbiotic relationship between two living organisms in which one organism benefits and the other is neither harmed nor helped is known as:
| A | Commensalism |
|---|---|
| B | Predation |
| C | Parasitism |
| D | Mutualism |
Answer: A) Commensalism
Explanation: Symbiotic relationships are close interactions between different species. Commensalism is a specific type where one organism gains an advantage, while the other is unaffected. Think of birds nesting in a tree – the bird benefits by having a home, but the tree is generally neither helped nor harmed. Let’s briefly look at why the other options are incorrect:
- Predation: One organism (the predator) hunts and kills another (the prey) for food. This is a harmful relationship for the prey.
- Parasitism: One organism (the parasite) lives on or inside another organism (the host) and benefits by harming the host. Think of a tick feeding on a deer.
- Mutualism: Both organisms involved in the relationship benefit. A classic example is bees pollinating flowers – bees get food, and flowers get pollinated.
Question 2
Earthworms are a type of:
| A | Scavenger |
|---|---|
| B | Parasite |
| C | Detritivore |
| D | Omnivore |
Answer: C) Detritivore
Explanation: Detritivores play a crucial role in ecosystems by consuming detritus, which is dead organic matter like decaying leaves, animal carcasses, and feces. Earthworms ingest soil and leaf litter, breaking down organic material and enriching the soil. Here’s why the other options don’t fit:
- Scavenger: Scavengers, like vultures, primarily consume carrion (dead animal flesh). They don’t typically consume decaying plant matter to the same extent as detritivores, and they lack the specialized digestive systems for detritus.
- Parasite: Parasites live off living hosts, not dead organic matter.
- Omnivore: Omnivores eat both plants and animals, but earthworms primarily feed on decaying organic matter, placing them more specifically in the detritivore category.
Question 3
At which trophic level are cheetahs located?
| A | Producers |
|---|---|
| B | Primary consumers |
| C | Secondary consumers |
| D | Detritivores |
Answer: C) Secondary consumers
Explanation: Trophic levels describe the position an organism occupies in a food chain or food web, based on its feeding habits.
- Producers: These are autotrophs, like plants, that produce their own food through photosynthesis. They form the base of the food chain.
- Primary consumers: These are herbivores that eat producers. Examples include gazelles, rabbits, and cows.
- Secondary consumers: These are carnivores that eat primary consumers. Cheetahs, lions, and snakes fall into this category as they prey on herbivores.
- Detritivores: As discussed earlier, they consume dead organic matter and are not typically considered a trophic level in the same linear food chain sense as producers and consumers.
Cheetahs hunt and eat gazelles and hares, which are primary consumers, making cheetahs secondary consumers.
Question 4
In which of the following ecosystems is net primary productivity the highest?
| A | Temperate forest |
|---|---|
| B | Savanna |
| C | Swamps and marshes |
| D | Temperate grassland |
Answer: C) Swamps and marshes
Explanation: Net Primary Productivity (NPP) refers to the rate at which producers in an ecosystem convert solar energy into biomass, minus the energy they use for respiration. Ecosystems with high NPP are highly productive in terms of plant growth and biomass accumulation.
Swamps and marshes, also known as freshwater wetlands, typically exhibit the highest NPP due to a combination of factors:
- Abundant Water: Water is essential for photosynthesis, and wetlands are water-saturated environments.
- Warm Temperatures: Many swamps and marshes are located in warmer climates, which promote higher rates of photosynthesis.
- Nutrient Availability: While some wetlands can be nutrient-limited, many are rich in nutrients due to runoff and decomposition.
- Sunlight: Ample sunlight reaches these ecosystems, further driving photosynthesis.
Temperate forests, savannas, and temperate grasslands have lower NPP compared to swamps and marshes due to limitations in water, temperature, or nutrient availability.
Question 5
What percentage of biomass is conserved at each trophic level?
| A | 1% |
|---|---|
| B | 5% |
| C | 10% |
| D | 20% |
Answer: C) 10%
Explanation: The diagram illustrates the 10% rule, a fundamental concept in ecology regarding energy transfer in food chains. On average, only about 10% of the energy or biomass from one trophic level is transferred to the next. The remaining 90% is used by organisms at each level for metabolic processes like respiration, movement, and reproduction, and is eventually lost as heat.
For example, if producers (like plants) capture 10,000 joules of energy, only about 1,000 joules will be available to primary consumers, and subsequently, only about 100 joules will be available to secondary consumers. This energy pyramid explains why food chains are typically limited to 4 or 5 trophic levels – there simply isn’t enough energy left to support more levels.
Alt text: Energy Pyramid illustrating the 10% rule of energy transfer in ecosystems, demonstrating energy loss at each trophic level for AP Environmental Science Unit 1 test preparation.
Question 6
Which biogeochemical cycle depends on bacteria to make the nutrient usable by plants?
| A | Nitrogen cycle |
|---|---|
| B | Carbon cycle |
| C | Phosphorus cycle |
| D | Water cycle |
Answer: A) Nitrogen cycle
Explanation: The nitrogen cycle is heavily reliant on bacteria for several key steps that convert atmospheric nitrogen (N2), which is unusable by plants, into forms they can absorb and utilize.
- Nitrogen fixation: Certain types of bacteria, like Rhizobium in soil and cyanobacteria in aquatic environments, convert atmospheric nitrogen (N2) into ammonia (NH3), a form of nitrogen plants can use.
- Nitrification: Other bacteria convert ammonia (NH3) into nitrites (NO2-) and then nitrates (NO3-), also usable by plants.
- Denitrification: Bacteria also play a role in denitrification, converting nitrates back into atmospheric nitrogen (N2), returning nitrogen to the atmosphere and completing the cycle.
While bacteria are involved in other cycles, their role is most critical and unique in making nitrogen available to plants in the nitrogen cycle.
Question 7
Which of the following terrestrial biomes is mostly made up of coniferous evergreen trees that can tolerate cold winters and short growing seasons, and is located in northern Europe, Russia, and North America?
| A | Tundra |
|---|---|
| B | Boreal forest |
| C | Woodland/shrubland |
| D | Temperate seasonal forest |
Answer: B) Boreal forest
Explanation: Boreal forests, also known as taiga, are characterized by:
- Coniferous evergreen trees: Dominated by trees like spruce, fir, and pine, which are adapted to cold climates with needles that minimize water loss and conical shapes to shed snow.
- Cold winters and short growing seasons: Located in high latitudes (50° to 60° N), these biomes experience long, cold winters and short, cool summers.
- Location: Found across northern regions of North America (Canada and Alaska), Europe (Scandinavia), and Russia (Siberia).
Let’s differentiate it from the other biomes:
- Tundra: Even further north than boreal forests, tundra is characterized by permafrost, low-growing shrubs, mosses, and lichens, but lacks tall trees.
- Woodland/shrubland: Found in warmer, drier climates with shrubs and short trees, like chaparral or Mediterranean biomes.
- Temperate seasonal forest: Experiences distinct seasons with deciduous trees that lose their leaves in the fall, found in more temperate latitudes than boreal forests.
Question 8
Which type of aquatic ecosystem is made up of salt-tolerant trees that are important in stabilizing tropical and subtropical coastlines?
| A | Salt marshes |
|---|---|
| B | Intertidal zone |
| C | Mangrove swamps |
| D | Freshwater wetlands |
Answer: C) Mangrove swamps
Explanation: Mangrove swamps are unique coastal wetlands found in tropical and subtropical regions. They are defined by:
- Salt-tolerant trees (mangroves): Mangrove trees are specially adapted to survive in saline (salty) conditions, filtering out salt through their roots and leaves.
- Coastal stabilization: Mangrove forests have dense root systems that trap sediment and reduce erosion, protecting coastlines from storms and waves.
- Habitat: They provide crucial habitat and nursery grounds for a wide variety of marine organisms, including fish, crustaceans, and birds.
Contrasting with other options:
- Salt marshes: Coastal wetlands dominated by herbaceous plants (grasses and sedges) rather than trees, found in more temperate regions.
- Intertidal zone: The area between high and low tide marks, characterized by fluctuating water levels and diverse organisms adapted to these conditions, but not specifically defined by salt-tolerant trees.
- Freshwater wetlands: Wetlands with non-saline water, such as swamps, marshes, and bogs, that lack the salt-tolerant mangrove trees.
Question 9
At which level of complexity do different species interact with each other?
| A | Ecosystem |
|---|---|
| B | Community |
| C | Population |
| D | Biome |
Answer: B) Community
Explanation: Ecological levels of organization build upon each other:
- Population: A group of individuals of the same species living in a particular area.
- Community: All the different populations of species living and interacting within a specific area. This is the level where interspecies interactions like competition, predation, and symbiosis occur.
- Ecosystem: A community of organisms plus their physical environment (abiotic factors) interacting as a functional unit.
- Biome: A large-scale ecosystem characterized by specific climate conditions and dominant plant communities (e.g., desert, rainforest, tundra).
Therefore, a community is the level of ecological organization where interactions between different species are most directly observed and studied.
Question 10
What percentage of solar energy striking producers is captured by photosynthesis?
| A | 1% |
|---|---|
| B | 5% |
| C | 95% |
| D | 99% |
Answer: A) 1%
Explanation: Despite the abundance of solar energy reaching Earth, plants are surprisingly inefficient at capturing it for photosynthesis. On average, producers capture only about 1% of the incoming solar energy and convert it into chemical energy through photosynthesis.
Several factors contribute to this low efficiency:
- Reflection and Transmission: A significant portion of sunlight is reflected back into the atmosphere or passes through leaves without being absorbed.
- Wavelength Limitations: Chlorophyll, the pigment in plants that captures light energy, primarily absorbs only certain wavelengths of visible light (red and blue), while other wavelengths are not effectively used.
- Energy Loss in Photosynthesis: Photosynthesis itself is not perfectly efficient, and some energy is lost as heat during the process.
This low capture rate highlights the vast amount of solar energy that is not directly utilized by producers and underscores the importance of even small increases in photosynthetic efficiency for overall ecosystem productivity.
Question 11
Which biogeochemical process is most impacted by burning fossil fuels?
| A | Water cycle |
|---|---|
| B | Carbon cycle |
| C | Nitrogen cycle |
| D | Phosphorous cycle |
Answer: B) Carbon cycle
Explanation: Burning fossil fuels (coal, oil, and natural gas) has a profound impact on the carbon cycle. Fossil fuels are formed from the remains of ancient organisms and store vast amounts of carbon that has been sequestered underground for millions of years.
When fossil fuels are burned for energy, this stored carbon is released into the atmosphere in the form of carbon dioxide (CO2), a potent greenhouse gas. This rapid increase in atmospheric CO2 concentration is the primary driver of climate change and global warming.
While burning fossil fuels can indirectly affect other cycles, the most direct and significant impact is on the carbon cycle due to the massive release of stored carbon.
Question 12
Which of the following is released by volcanic eruption and is a necessary nutrient for living things but can also lead to acid rain?
| A | Calcium |
|---|---|
| B | Potassium |
| C | Sulfur |
| D | Nitrogen |
Answer: C) Sulfur
Explanation: Sulfur is an essential nutrient for living organisms, playing a role in protein structure and enzyme function. Volcanic eruptions are a natural source of sulfur dioxide (SO2) gas. Additionally, human activities like burning fossil fuels (especially coal) and industrial processes also release significant amounts of sulfur dioxide into the atmosphere.
Sulfur dioxide in the atmosphere can react with water vapor and other substances to form sulfuric acid (H2SO4) and sulfurous acid (H2SO3), which are major components of acid rain. Acid rain can damage ecosystems, acidify lakes and soils, and corrode buildings and monuments.
While other elements listed are also nutrients or released by volcanoes, sulfur is most directly linked to both volcanic eruptions and acid rain formation.
Question 13
Which of the following biogeochemical processes has no atmospheric component?
| A | Water cycle |
|---|---|
| B | Carbon cycle |
| C | Nitrogen cycle |
| D | Phosphorous cycle |
Answer: D) Phosphorous cycle
Explanation: Biogeochemical cycles describe the movement of nutrients through different spheres of the Earth: atmosphere, hydrosphere (water), lithosphere (rocks/soil), and biosphere (living organisms).
The phosphorus cycle is unique because it lacks a significant atmospheric phase. Phosphorus is primarily found in rocks and soil minerals. It enters ecosystems through the weathering and erosion of rocks, releasing phosphate ions (PO43-) into soil and water. Plants absorb phosphate from the soil, and it moves through the food web. Phosphorus eventually returns to soil and sediments through decomposition and geological processes.
In contrast:
- Water cycle: Has a major atmospheric component (evaporation, condensation, precipitation).
- Carbon cycle: Carbon dioxide (CO2) is a key atmospheric component.
- Nitrogen cycle: Nitrogen gas (N2) is the most abundant gas in the atmosphere.
Question 14
Which biogeochemical cycle requires solar energy to move components from the earth into the atmosphere?
| A | Water cycle |
|---|---|
| B | Phosphorus cycle |
| C | Nitrogen cycle |
| D | Carbon cycle |
Answer: A) Water cycle
Explanation: Solar energy is the driving force behind the water cycle. Evaporation, the process of liquid water turning into water vapor (gas) and entering the atmosphere, is directly powered by solar energy. The sun’s heat provides the energy needed to break the bonds holding water molecules together, allowing them to escape into the air.
While solar energy indirectly influences other cycles, it is most directly and fundamentally required for evaporation in the water cycle.
Question 15
Which nutrient is a limiting nutrient in aquatic ecosystems and, when added to aquatic environments, typically causes algal blooms?
| A | Hydrogen |
|---|---|
| B | Phosphorus |
| C | Potassium |
| D | Calcium |
Answer: B) Phosphorus
Explanation: In many freshwater aquatic ecosystems, phosphorus is often the limiting nutrient, meaning its availability controls the rate of primary productivity (algae and plant growth). Phosphorus is naturally scarce in many aquatic environments because it is not abundant in the atmosphere and is slowly released from rocks through weathering.
When excess phosphorus enters aquatic ecosystems, often from human sources like fertilizers and sewage, it can lead to eutrophication. The added phosphorus stimulates excessive growth of algae, resulting in algal blooms. These blooms can block sunlight, deplete oxygen when algae die and decompose, and harm aquatic life.
While other nutrients are important, phosphorus is frequently the key limiting nutrient in freshwater systems, and its excess is a major cause of water quality problems.
This study guide should provide a solid foundation for your AP Environmental Science Unit 1 test preparation. Review these concepts, practice more questions, and you’ll be well on your way to success! Good luck!
