GED Science Quiz: Analyze Ecosystems

What this quiz covers

This quiz focuses on Analyze Ecosystems, giving you a quick way to practice the rules, question types, and explanations that matter most for GED Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. The sea otter population would increase due to a sudden lack of predators.
2. The entire food web would be negatively impacted due to the loss of the primary producer. (correct answer)
3. Sea urchins would quickly adapt to a new food source and their population would remain stable.
4. The water would become clearer, greatly benefiting all organisms that do not rely on kelp.

Explanation: When you encounter questions about ecosystem disruption, focus on understanding how energy and nutrients flow through food webs. In any ecosystem, the loss of a primary producer—organisms that convert sunlight into usable energy—creates ripple effects throughout the entire system. Kelp forests serve as the foundation of this coastal ecosystem. As primary producers, they capture solar energy through photosynthesis and convert it into biomass that feeds the entire food web. When you remove this foundation, every organism that depends on kelp either directly (as food) or indirectly (as habitat) faces serious consequences. This makes option B correct—the entire food web would collapse without its primary energy source. Option A incorrectly suggests sea otter populations would increase due to lack of predators. However, the passage doesn't mention sea otter predators, and otters would actually struggle without the fish and other prey that depend on kelp habitat. Option C assumes sea urchins would easily adapt to new food sources, but rapid adaptation to completely different diets is unlikely, especially when their primary food source disappears entirely. Option D focuses on water clarity benefits, but clearer water cannot compensate for the massive loss of food and shelter that kelp provides to the ecosystem's inhabitants. For GED Science ecosystem questions, always trace the flow of energy from producers to consumers. When primary producers are eliminated, don't focus on single species or minor environmental changes—look for answers that address the fundamental disruption to the entire system's energy foundation.

Question 2

1. Competition always involves one organism hunting another, which is not a feature of symbiosis.
2. Competition is an interaction where both organisms are negatively affected by striving for the same limited resource. (correct answer)
3. Symbiosis occurs only between two animal species, while competition can occur between plants and animals.
4. Competition always leads to a beneficial long-term association between the two competing species.

Explanation: When you encounter questions about ecological interactions, focus on understanding how organisms affect each other - whether positively, negatively, or neutrally. Competition occurs when two or more organisms vie for the same limited resource, such as food, water, territory, or mates. In this interaction, both organisms experience negative effects because they must expend energy competing and may not obtain enough of the resource they need. This is fundamentally different from symbiotic relationships, where organisms live in close association with varying effects on each participant. Choice B correctly identifies that competition negatively affects both organisms as they struggle for limited resources. Neither competitor benefits from the other's presence - they would both be better off without the competition. Choice A is wrong because competition doesn't involve hunting or predation - it's about accessing shared resources. Predation is actually a separate ecological interaction entirely. Choice C incorrectly limits symbiosis to animals only. Symbiotic relationships occur across all kingdoms of life, including plants, fungi, and microorganisms. Think of lichens (fungi and algae) or nitrogen-fixing bacteria in plant roots. Choice D contradicts the nature of competition. While competition can drive evolutionary adaptations over long periods, the immediate interaction is harmful to both parties - there's no beneficial association between competitors. Remember this key distinction for the GED: competition always has negative effects on participants (both lose), while symbiotic relationships involve at least one organism living closely with another, with effects ranging from beneficial to harmful depending on the type of symbiosis.

Question 3

1. Parasitism, where the wrasse slowly harms the larger fish by its feeding.
2. Commensalism, where only the wrasse benefits from the food it obtains.
3. Mutualism, where both the wrasse and the larger fish gain a significant benefit. (correct answer)
4. Predation, where the wrasse is a small predator hunting on the larger fish.

Explanation: When you encounter questions about species interactions, focus on who benefits and who is harmed. Symbiotic relationships are classified based on the costs and benefits each organism experiences. In this scenario, both species gain significant advantages. The cleaner wrasse obtains food (dead skin, scales, and parasites), which provides essential nutrition for survival. Meanwhile, the larger fish receive a valuable health service—removal of harmful parasites and dead tissue that could cause infection or disease. The fact that larger fish actively "seek out" cleaning stations demonstrates they derive real benefit from this interaction. This mutual benefit pattern defines mutualism, making C correct. Both organisms are better off because of the relationship. Option A incorrectly suggests parasitism. While the wrasse does feed on the larger fish, it's removing harmful material, not damaging healthy tissue. True parasites harm their hosts. Option B misidentifies this as commensalism, where only one species benefits while the other is unaffected. However, the larger fish clearly benefit from parasite removal—they're not just neutral bystanders. Option D calls this predation, but predators kill and consume their prey. The wrasse doesn't harm the larger fish; it actually improves their health by removing parasites and dead material. Study tip: For symbiosis questions, create a simple chart: (+) for benefit, (-) for harm, (0) for no effect. Mutualism is (+/+), commensalism is (+/0), parasitism is (+/-), and predation involves one organism consuming another. This framework will help you quickly categorize any species interaction.

Question 4

1. competition.
2. parasitism.
3. commensalism.
4. mutualism. (correct answer)

Explanation: When you encounter questions about relationships between different organisms, you're being tested on symbiosis - the various ways species interact with each other. The key is identifying who benefits and who is harmed (or neither) in each relationship. Looking at this passage, both humans and gut bacteria clearly benefit from their relationship. Humans gain access to nutrients from food they couldn't digest alone, while bacteria receive a stable, nutrient-rich home. When both organisms benefit from their interaction, this defines mutualism, making D the correct answer. Let's examine why the other options don't fit. A) Competition occurs when organisms fight over the same limited resources, like two plants competing for sunlight. Here, humans and bacteria aren't competing - they're cooperating. B) Parasitism describes a relationship where one organism benefits while harming the other, like tapeworms stealing nutrients and damaging their host's intestines. The gut bacteria aren't harming humans; they're helping. C) Commensalism exists when one organism benefits while the other is neither helped nor harmed, like birds nesting in trees without affecting the tree. Since humans clearly benefit from improved digestion, this isn't commensalism. For GED Science questions about symbiosis, always ask yourself two questions: "Who benefits?" and "Who is harmed?" This will help you distinguish between mutualism (both benefit), parasitism (one benefits, one is harmed), commensalism (one benefits, one unaffected), and competition (both organisms struggle for the same resource). The gut bacteria example is a classic case of mutualism you should remember.

Question 5

1. Energy flows from the grass to the zebra and then to the lion. (correct answer)
2. Energy flows from the lion to the zebra and then to the grass.
3. The zebra acts as the main producer in this particular ecosystem.
4. The lion provides the primary source of energy for the zebra.

Explanation: When you encounter food chain questions, focus on tracing energy from its original source through each level of consumption. Energy in ecosystems always originates from producers (plants) and flows upward through consumers. In this savanna food chain, grass serves as the producer, capturing solar energy through photosynthesis. When zebras graze on grass, they obtain this stored energy for their own biological processes. Lions then hunt zebras, acquiring the energy that was originally captured by the grass and transferred through the zebra. This creates a clear path: grass → zebra → lion. Choice A correctly identifies this unidirectional flow of energy from grass to zebra to lion, following the fundamental principle that energy moves from producers to primary consumers to secondary consumers. Choice B reverses the energy flow entirely, suggesting energy moves from lion to zebra to grass. This violates basic ecological principles since predators cannot provide energy to their prey. Choice C incorrectly identifies zebras as producers. Zebras are herbivorous consumers that depend on plants for energy—they cannot produce their own energy through photosynthesis like grass can. Choice D suggests lions provide energy to zebras, which contradicts the predator-prey relationship. Lions consume zebras to obtain energy; they don't supply it. Study tip: Remember that energy flow in food chains is always unidirectional, starting with producers (plants) and moving up through consumer levels. On the GED, look for the organism that can make its own food (the producer) as your starting point for tracing energy flow.

Question 6

1. The grasshopper population, as their primary predator has been removed. (correct answer)
2. The hawk population, as their main competitor for food is gone.
3. The grass population, as fewer organisms are present to consume it.
4. The decomposer population, as they will have more resources available.

Explanation: When you encounter questions about food chains and population changes, focus on the direct predator-prey relationships and immediate effects before considering indirect impacts. In this grassland food chain (grass → grasshoppers → shrews → hawks), shrews serve as the primary predator of grasshoppers. When the shrew population is eliminated by disease, grasshoppers suddenly lose their main predator. Without shrews hunting them, the grasshopper population will experience rapid growth since their primary limiting factor has been removed. This represents a direct, immediate effect in the food web. Let's examine why the other options are incorrect. Option B suggests hawks would increase because competitors are gone, but shrews aren't competitors with hawks—they're prey. Hawks would actually struggle without their food source. Option C proposes grass population increase, but this effect would be indirect and delayed. Even if it occurred, grasshoppers (now without predators) would likely consume more grass, not less. Option D about decomposers increasing assumes more dead shrews provide resources, but the question states shrews were eliminated by disease, and decomposer population changes wouldn't be the most immediate or significant effect. The correct answer is A because it identifies the most direct relationship: removing a predator immediately benefits its prey population. Remember this pattern for GED Science: when analyzing ecosystem disruptions, always trace the direct predator-prey relationships first. The most immediate population changes occur between organisms that directly eat each other, not through longer food chain connections.

Question 7

1. 20 kcal
2. 200 kcal (correct answer)
3. 2,000 kcal
4. 20,000 kcal

Explanation: When you encounter energy transfer questions in ecology, remember that energy flows through ecosystems in a predictable pattern. As energy moves up each trophic level in a food chain, only about 10% transfers to the next level—the rest is lost as heat, waste, or used for metabolic processes. To solve this problem, you need to trace the energy through each step. Starting with phytoplankton at 20,000 kcal, the krill (second trophic level) receive 10% of that energy: $20,000 \times 0.10 = 2,000 \text{ kcal}$. Then the penguins (third trophic level) receive 10% of the krill's energy: $2,000 \times 0.10 = 200 \text{ kcal}$. This confirms answer B is correct. Looking at the wrong answers: A (20 kcal) represents taking 10% three times instead of twice—a common error when students miscount trophic levels. C (2,000 kcal) is the energy available to krill, not penguins; this happens when you stop calculating one level too early. D (20,000 kcal) assumes 100% energy transfer, ignoring the fundamental principle that energy decreases dramatically at each level. For GED Science success, always count trophic levels carefully and remember the "10% rule." When you see energy transfer questions, sketch out the food chain, label each level, and multiply by 0.10 for each step up from your starting point. This systematic approach prevents calculation errors and ensures you don't stop too early in multi-step transfers.

Question 8

1. Producer
2. Decomposer
3. Secondary consumer
4. Primary consumer (correct answer)

Explanation: When you encounter questions about trophic levels, think about the flow of energy through an ecosystem and each organism's role in the food chain. Trophic levels are essentially "feeding levels" that show who eats whom. Let's trace this food chain: phytoplankton (perform photosynthesis) → zooplankton (eat phytoplankton) → small fish (eat zooplankton). Since zooplankton feed directly on producers (the phytoplankton), they occupy the primary consumer level. Primary consumers are always the first organisms to eat the producers in any food chain. Looking at why the other answers don't work: (A) Producer is incorrect because zooplankton don't make their own food through photosynthesis—only the phytoplankton do that. (B) Decomposer is wrong because zooplankton don't break down dead organic matter; they're actively hunting and eating living phytoplankton. (C) Secondary consumer would describe the small fish, since they eat the primary consumers (zooplankton). The key pattern to remember is that trophic levels follow a strict sequence: producers always come first, then primary consumers eat the producers, then secondary consumers eat the primary consumers, and so on. Count the steps from the producers to identify any organism's trophic level. For GED Science questions about ecosystems, always identify the producers first (they make their own food), then trace who eats whom to determine each organism's position in the energy flow.

Question 9

1. The aquatic insects at the bottom of the food chain.
2. The large fish at the top of the food chain. (correct answer)
3. The algae and producers in the lake water.
4. The concentration would be equal in all organisms.

Explanation: When you encounter questions about toxins moving through food chains, you're dealing with the concept of bioaccumulation and biomagnification. Toxins don't just disappear—they accumulate in organisms' tissues and become more concentrated as they move up each level of the food chain. Here's how it works: Small aquatic insects absorb toxins from the contaminated water. When small fish eat many of these insects, they're consuming all the toxins that were stored in each insect's body. Those toxins don't break down easily, so they build up in the small fish's tissues. When large fish eat many small fish, they're getting an even more concentrated dose—all the toxins that had already accumulated in each small fish they consume. Answer B is correct because large fish at the top of the food chain experience the highest concentration through this biomagnification process. Each step up the food chain multiplies the toxin concentration. Answer A is wrong because aquatic insects, while they do absorb toxins, haven't had the opportunity to accumulate toxins from multiple prey organisms like the fish above them. Answer C is incorrect because algae and producers may have some toxin exposure from the water, but they're not consuming other contaminated organisms. Answer D misses the entire concept—biomagnification means concentrations are definitely not equal across all levels. Remember this pattern: toxins and heavy metals typically become more concentrated as you move up trophic levels. Top predators almost always have the highest concentrations of persistent pollutants.

Question 10

1. A rabbit eating clover in a field. (correct answer)
2. Photosynthetic algae in a pond.
3. A giant redwood tree in a forest.
4. Chemosynthetic bacteria at a deep-sea vent.

Explanation: When approaching ecosystem energy flow questions, focus on the fundamental difference between producers and consumers. Autotrophs make their own food through processes like photosynthesis or chemosynthesis, while heterotrophs must obtain energy by consuming other organisms. A rabbit eating clover (choice A) is clearly a heterotroph because it cannot produce its own food and must consume plants to survive. The rabbit depends entirely on external food sources for energy, making it a primary consumer in the food chain. Let's examine why the other options are autotrophs: Choice B, photosynthetic algae, produces its own food using sunlight, water, and carbon dioxide through photosynthesis. Choice C, the giant redwood tree, is also photosynthetic, converting solar energy into chemical energy stored in glucose. Choice D might seem tricky, but chemosynthetic bacteria are autotrophs that create their own food by converting chemicals like hydrogen sulfide into energy, rather than relying on sunlight. The key distinction is the source of energy: autotrophs harness energy from their environment (light or chemicals) to build organic molecules, while heterotrophs break down existing organic matter from other organisms. Study tip: Remember that "auto" means self and "hetero" means other. Autotrophs feed themselves through synthesis, while heterotrophs feed on others. On the GED, look for action words like "eating," "consuming," or "hunting" to identify heterotrophs, and processes like "photosynthesis" or "chemosynthesis" to identify autotrophs.

Question 11

1. both the ants and the acacia tree receive a significant benefit from the relationship. (correct answer)
2. the tree is completely unaffected by the continuous presence of the ants.
3. the ants harm the tree by consuming its valuable nectar resource.
4. the ants and the herbivorous insects are competing for the same limited resource.

Explanation: When you encounter questions about species interactions, focus on identifying who benefits and who is harmed in the relationship. This determines which type of symbiotic relationship you're looking at. In this passage, you can see a clear exchange of benefits: the ants provide protection services (defending against herbivores and removing competing plants), while the acacia trees provide resources (shelter in hollow thorns and nectar for food). Both species gain significant advantages from this partnership, making it a classic example of mutualism. Choice A correctly identifies that both organisms receive substantial benefits from their interaction. The ants get food and housing, while the trees get protection and reduced competition - this mutual benefit defines mutualism. Choice B describes commensalism, where one species benefits while the other is unaffected. Since the tree clearly benefits from the ants' protective services, this doesn't apply here. Choice C suggests parasitism, where one organism harms another. However, the tree willingly produces nectar as "payment" for protection services - this isn't harmful consumption but rather a beneficial trade. Choice D focuses on competition between ants and herbivorous insects, which misses the point entirely. The question asks about the ant-tree relationship, not the ant-herbivore interaction. Study tip: Remember the three main symbiotic relationships by their benefit patterns: mutualism (+/+), commensalism (+/0), and parasitism (+/-). When analyzing any species interaction, first identify what each organism gains or loses, then match the pattern to determine the relationship type.

Question 12

1. competition, because both are plants fighting for sunlight.
2. mutualism, because both organisms are plants living together.
3. parasitism, because the mistletoe benefits by harming the tree. (correct answer)
4. commensalism, because the mistletoe receives support from the tree.

Explanation: When you encounter questions about organisms living together, you're dealing with symbiotic relationships. The key is identifying who benefits and who is harmed in the interaction. Looking at the mistletoe scenario, you need to analyze what happens to each organism. The mistletoe clearly benefits by absorbing water and nutrients from the host tree through its roots. Meanwhile, the host tree is weakened and becomes more susceptible to disease - it's being harmed. This one-sided relationship where one organism benefits at the expense of another defines parasitism, making C correct. Let's examine why the other options don't fit. Choice A suggests competition, but competition occurs when organisms fight for the same limited resources in their environment. Here, the mistletoe isn't competing with the tree for external resources - it's directly taking resources from the tree itself. Choice B identifies mutualism, which requires both organisms to benefit from the relationship. Since only the mistletoe benefits while the tree is harmed, this isn't mutualism. Choice D suggests commensalism, where one organism benefits while the other is neither helped nor harmed. However, the passage clearly states the tree is weakened and more susceptible to disease, showing definite harm. For GED science questions about symbiotic relationships, focus on the outcomes for each organism: parasitism means one benefits while harming the other, mutualism means both benefit, and commensalism means one benefits while the other is unaffected. Always look for evidence of benefit or harm in the passage.

Question 13

1. parasitism, where the tapeworm benefits at the expense of the mammal. (correct answer)
2. commensalism, where the tapeworm benefits and the mammal is unaffected.
3. competition, as both organisms require the same nutrients for their survival.
4. mutualism, as the tapeworm may help the mammal to digest its food.

Explanation: When you encounter questions about organisms living together, you need to identify the type of symbiotic relationship by examining who benefits and who is harmed or helped. Let's analyze what's happening here: the tapeworm absorbs nutrients from the mammal's digested food, while the mammal suffers malnutrition and weakness. This is a classic one-sided relationship where one organism thrives while directly harming the other. Answer A correctly identifies this as parasitism. In parasitic relationships, the parasite (tapeworm) benefits by obtaining resources, while the host (mammal) is harmed. The passage clearly states the mammal suffers negative effects, making this textbook parasitism. Answer B describes commensalism, but this is wrong because the mammal isn't "unaffected" — it's explicitly harmed through malnutrition and weakness. In true commensalism, the host experiences no positive or negative effects. Answer C suggests competition, but these organisms aren't competing for the same resource in the same environment. Instead, the tapeworm is directly taking nutrients that the mammal has already processed, which is exploitation, not competition. Answer D proposes mutualism, where both organisms benefit. However, there's no evidence the tapeworm helps with digestion, and the passage clearly states the mammal is harmed, not helped. Study tip: Remember the three main symbiotic relationships by their effects: parasitism (one benefits, one harmed), commensalism (one benefits, one unaffected), and mutualism (both benefit). Always look for keywords indicating harm or benefit to each organism involved.

Question 14

1. A producer, because it helps create energy for other animals.
2. A primary consumer, because it eats other organisms.
3. A parasite, because it lives off of other animals for its food.
4. A scavenger, transferring energy from dead organic matter. (correct answer)

Explanation: When you encounter questions about ecological roles, focus on how organisms obtain energy and their function in the ecosystem's energy flow. Each organism has a specific role in transferring energy from one level to another. Vultures are scavengers that feed exclusively on dead animals they didn't kill themselves. This makes answer D correct because scavengers play the crucial role of transferring energy from dead organic matter back into the living ecosystem. They break down decomposing carcasses and convert that stored energy into forms other organisms can use, essentially recycling nutrients and energy that would otherwise be lost. Answer A is incorrect because producers create their own energy through photosynthesis or chemosynthesis - vultures cannot do this. Answer B misidentifies vultures as primary consumers, which are organisms that eat producers (plants). Vultures eat dead animals, not plants, and they're actually secondary or tertiary consumers depending on what the dead animal originally ate. Answer C incorrectly labels vultures as parasites. Parasites live on or in living host organisms and typically don't kill their hosts. Vultures feed on animals that are already dead, so there's no parasitic relationship. For GED Science questions about ecological roles, remember that an organism's classification depends on its energy source and feeding behavior. Look for key words: producers make their own food, primary consumers eat plants, secondary/tertiary consumers eat other animals, parasites live off living hosts, and scavengers feed on dead organic matter. The feeding behavior described in the passage will always give you the answer.

Question 15

1. Competition
2. Parasitism
3. Commensalism
4. Mutualism (correct answer)

Explanation: When you encounter questions about species interactions, you need to identify who benefits and who is harmed in the relationship. Symbiotic relationships fall into distinct categories based on these costs and benefits. In this bee-flower relationship, both species clearly benefit. The bees obtain nectar, which provides them with essential food energy. Meanwhile, the flowers receive pollination services when bees transfer pollen between flowers, enabling sexual reproduction. Since both organisms gain advantages with no apparent harm to either, this is mutualism - a "win-win" relationship. Let's examine why the other options don't fit. Choice A, competition, occurs when organisms fight over the same limited resources, like two plant species competing for sunlight. Here, bees and flowers aren't competing - they're cooperating. Choice B, parasitism, describes a relationship where one organism benefits while harming the other, like a tick feeding on a dog's blood. The flowers aren't being harmed by the bees' nectar collection. Choice C, commensalism, means one organism benefits while the other is unaffected - neither helped nor harmed. This doesn't apply because flowers clearly benefit from pollination. For GED science questions about symbiosis, always ask yourself: "Who benefits and who suffers?" If both benefit, it's mutualism. If one benefits and one is harmed, it's parasitism. If one benefits and the other is unaffected, it's commensalism. This simple framework will help you quickly identify the relationship type in any ecological scenario.

Question 16

1. parasitism, because the barnacles live on the whale's body.
2. mutualism, because both organisms live in the same environment.
3. commensalism, because one organism benefits while the other is unaffected. (correct answer)
4. competition, because they both consume plankton from the water.

Explanation: When you encounter questions about organisms living together, you're being tested on symbiotic relationships. The key is identifying who benefits and who is harmed or helped in the interaction. Let's analyze what's happening here: barnacles attach to whales, gain transportation and access to food-rich waters (they benefit), while whales experience no positive or negative effects (they're unaffected). This perfectly describes commensalism - a relationship where one organism benefits and the other is neither helped nor harmed. Choice A is wrong because parasitism requires the host (whale) to be harmed. Since the passage explicitly states the whale is "neither helped nor harmed," this can't be parasitism, even though barnacles do live on the whale's body. Choice B misunderstands mutualism, which requires both organisms to benefit. While barnacles and whales do share the same environment, simply living in the same place doesn't create mutualism - both parties must gain something from the relationship. Choice D incorrectly assumes competition exists. Competition occurs when organisms compete for the same limited resources. The passage doesn't indicate that barnacles and whales are competing for plankton or that this creates any conflict between them. The correct answer is C because it accurately identifies the one-sided benefit with no harm to the other party. Study tip: For symbiosis questions on the GED, create a quick mental checklist: Does organism 1 benefit/get harmed/stay neutral? Does organism 2 benefit/get harmed/stay neutral? Match the pattern to parasitism (one benefits, one harmed), mutualism (both benefit), or commensalism (one benefits, one neutral).

Question 17

1. A food web accounts for the complex, interconnected feeding relationships where organisms have multiple food sources. (correct answer)
2. A food web shows that energy flows in a single, unbranched line from producer to top consumer.
3. A food web primarily includes the role of decomposers, while a food chain focuses only on consumers.
4. A food web illustrates exactly how much energy is lost as heat, which a food chain model cannot do.

Explanation: When you encounter questions about food webs versus food chains, focus on the key difference: complexity versus simplicity in feeding relationships. A food web provides a more accurate representation because it captures the reality that most organisms don't rely on just one food source. In nature, animals typically eat multiple types of prey, and many species can serve as food for various predators. For example, a rabbit might eat grass, clover, and berries, while also being prey for hawks, foxes, and snakes. This creates an interconnected network of feeding relationships that a simple linear food chain cannot represent. Answer A is correct because it identifies this crucial aspect—food webs show the complex, interconnected feeding relationships where organisms have multiple food sources, reflecting how energy actually flows through ecosystems. Answer B is backwards—it describes a food chain, not a food web. Food chains show single, unbranched lines, while food webs show multiple branching pathways. Answer C misrepresents both models. Both food webs and food chains can include decomposers, and food chains don't focus solely on consumers—they include producers too. Answer D confuses structural representation with quantitative measurement. Neither food webs nor food chains typically show specific amounts of energy lost as heat—that's what ecological pyramids demonstrate. Remember: Food chains are simplified educational tools showing one possible pathway, while food webs represent the messy reality of overlapping feeding relationships in actual ecosystems. When you see ecosystem questions, think about whether they're asking for simplified concepts or realistic complexity.

Question 18

1. The remora benefits from the relationship, while the shark is neither helped nor harmed. (correct answer)
2. The shark is a host in a parasitic relationship, losing food to the remora.
3. Both the remora and the shark benefit, creating a mutualistic relationship.
4. The remora and the shark are engaged in a typical predator-prey relationship.

Explanation: When you encounter questions about species interactions, focus on identifying who benefits, who is harmed, and who remains unaffected. This determines the type of symbiotic relationship. The passage clearly states that the remora gains food and protection while "the shark is not affected by the remora's presence." This describes commensalism - one organism benefits while the other experiences no effect. The remora receives nutritional and safety advantages without impacting the shark's well-being, making answer A correct. Let's examine why the other options are incorrect. Answer B suggests parasitism, but parasites harm their hosts by taking resources that would otherwise benefit the host organism. Here, the remora only eats food scraps that the shark leaves behind, not food the shark would consume. Answer C describes mutualism, where both species benefit from the interaction. However, the passage explicitly states the shark gains nothing from this relationship. Answer D proposes a predator-prey relationship, but neither animal is hunting or consuming the other - they're simply coexisting with the remora taking advantage of the shark's feeding habits. For symbiosis questions on the GED, memorize these key relationships: mutualism (both benefit), commensalism (one benefits, other unaffected), and parasitism (one benefits, other harmed). Always look for specific language about whether each organism is helped, harmed, or unaffected - the passage will usually state this directly, as it does here with "not affected."

Question 19

1. 1%
2. 10% (correct answer)
3. 50%
4. 90%

Explanation: When you encounter questions about energy flow in ecosystems, you're dealing with one of ecology's most fundamental principles: energy transfer efficiency between trophic levels. In ecological energy pyramids, energy flows from producers (plants) to primary consumers (herbivores) to secondary consumers (carnivores) and beyond. However, this transfer is remarkably inefficient. Organisms use most of their energy for basic life processes like metabolism, movement, and maintaining body temperature. Only about 10% of the energy stored in one trophic level becomes available to the next level through consumption. This is known as the "10% rule" or ecological efficiency. Looking at the incorrect options: Choice A (1%) severely underestimates the transfer rate - while energy loss is substantial, it's not quite this extreme. Choice C (50%) represents a major misconception, suggesting that half the energy transfers upward, which would make ecosystems far more energy-efficient than they actually are. Choice D (90%) gets the concept completely backwards - this represents roughly how much energy is lost at each level, not how much transfers up. The correct answer is B (10%), reflecting this well-established ecological principle that explains why food chains rarely exceed four or five levels - there simply isn't enough energy to support higher trophic levels. For GED Science success, remember that ecosystem energy questions often test the 10% rule. When you see energy pyramids or food webs, think "90% lost, 10% transferred" - this will help you quickly identify realistic energy transfer values.

Question 20

1. Geothermal heat that radiates from the Earth's core.
2. The Sun, captured through the process of photosynthesis. (correct answer)
3. Chemical energy stored in inorganic molecules in the soil.
4. The breakdown of dead material by decomposers.

Explanation: When you encounter questions about energy flow in ecosystems, think about tracing energy back to its original source. Nearly all life on Earth's surface depends on a continuous input of energy, and understanding this flow is fundamental to ecology. The Sun provides the ultimate energy source for almost all surface ecosystems through photosynthesis. During this process, plants and other photosynthetic organisms capture solar energy and convert it into chemical energy (glucose), which then flows through food chains. Primary consumers eat plants, secondary consumers eat primary consumers, and so on. Even when organisms die, the energy they contain originally came from the Sun via photosynthesis. Let's examine why the other options fall short. Choice A, geothermal heat from Earth's core, does power some specialized ecosystems around deep-sea vents or hot springs, but these represent a tiny fraction of Earth's ecosystems. Choice C, chemical energy in soil molecules, is actually derived from decomposed organic matter that ultimately traces back to photosynthesis. Choice D, decomposer breakdown of dead material, represents energy recycling rather than an energy source - decomposers are processing organic matter that originally got its energy from the Sun. For GED Science questions about ecosystems, remember that energy flows in one direction (from Sun through organisms), while matter cycles. When you see questions about energy sources, trace the flow back to its beginning - you'll almost always end up at solar energy captured by photosynthesis.