Predict Interaction Outcomes - Middle School Life Science

Which interaction outcome is most likely when a new predator is introduced to an ecosystem with abundant prey?

Prey decreases; predator increases at first. Predators thrive with plentiful food while prey are hunted.
Identify the interaction: a bee gets nectar while a flower gets pollinated.

Mutualism. Both organisms receive essential services from each other.
Which option best predicts what happens to predator population after prey sharply decreases?

Predator population decreases after a lag. Predators starve without sufficient prey, causing delayed population decline.
Identify the most likely outcome if an invasive predator is introduced to an island ecosystem.

Native prey populations decline; food web becomes less stable. Invasive species lack natural controls and disrupt balance.
What interaction is it when one species benefits and the other is unaffected?

Commensalism. One organism gains while the other experiences no harm or benefit.
What type of interaction occurs when two organisms need the same limited resource?

Competition. Both organisms are harmed by fighting for the same resource.
What is the role of decomposers in an ecosystem?

Break down dead matter and recycle nutrients. They convert organic waste into simpler compounds, returning essential elements to the ecosystem.
Identify the outcome if a parasite spreads rapidly through a host population.

Host population decreases; parasite may later decline. Parasites weaken hosts; fewer hosts limit parasite spread.
What term describes an organism that makes its own food using sunlight or chemicals?

Producer (autotroph). These organisms convert light or chemical energy into food through photosynthesis or chemosynthesis.
Which outcome is most likely if a drought reduces plant biomass in a grassland?

Herbivore populations decrease; predator populations may also decline. Less plant biomass means less food for herbivores up the food chain.
Which option best predicts the outcome if a keystone predator is removed from a community?

Prey increases and biodiversity often decreases. Without top-down control, prey overpopulate and outcompete other species.
What interaction is described when both species are harmed (−/−)?

Competition. Both organisms lose resources or energy through their interaction.
What is mutualism?

Both species benefit from the interaction. Examples include bees and flowers or cleaner fish and sharks.
What is a decomposer and what does it return to the ecosystem?

A recycler of dead matter that returns nutrients to the soil or water. They break down organic matter, completing nutrient cycles.
What interaction is shown when both species benefit (+/+) ?

Mutualism. Both organisms gain benefits from their interaction.
Which option best predicts the effect of a drought that reduces plant biomass on herbivores?

Herbivore population decreases due to less food. Reduced plant growth limits available food for primary consumers.
What is the role of decomposers in an ecosystem's matter cycle?

They break down dead matter and recycle nutrients. Essential for returning nutrients from dead organisms back to the soil.
What type of interaction occurs when one species benefits and the other is harmed?

Parasitism. The parasite gains nutrients while weakening its host.
Which outcome is most likely when a limiting resource becomes scarcer in a habitat?

Competition increases and some populations decrease. Less resources intensify competition, causing weaker competitors to decline.
What type of interaction is it when both species benefit?

Mutualism. Both organisms gain advantages from their relationship.
What is the most likely change in plant biomass after a large increase in herbivore population?

Plant biomass tends to decrease. More herbivores eat more plants, reducing plant mass.
What interaction is described when both species benefit (+/+)?

Mutualism. Both organisms gain advantages from their interaction.
What is the role of a producer in an ecosystem food web?

Organism that makes its own food, usually by photosynthesis. Forms the base of food chains by converting sunlight to chemical energy.
What is commensalism?

One species benefits and the other is unaffected. The commensal gains without helping or harming its partner.
Which type of interaction is shown when one benefits and the other is unaffected (+/0)?

Commensalism. One organism benefits while the other experiences no effect.
Which outcome is most likely if a new predator is introduced and prey has no defenses?

Prey population decreases rapidly; predator may later decline. Vulnerable prey populations crash when facing novel predators.
Identify the most likely outcome if a disease reduces the top predator population in a food web.

Prey populations increase; lower levels may decrease. Without predation pressure, prey multiply; this may reduce their food sources.
What is the most likely outcome if two species share the exact same niche long term?

One species outcompetes the other (competitive exclusion). Species can't coexist if they need identical resources.
What is the most likely effect of decreased sunlight on producers and then on consumers?

Producers decrease; consumers decrease afterward. Less sunlight reduces photosynthesis, affecting the food chain.
Which option best predicts what happens to fish when an algal bloom later causes low dissolved oxygen?

Fish populations decrease due to hypoxia. Decomposing algae consume oxygen, suffocating fish in hypoxic water.
Which outcome is most likely if a habitat is fragmented, reducing territory size for predators?

Predator populations decrease due to less space and prey. Smaller territories support fewer prey and thus fewer predators.
Identify the outcome if a predator population sharply decreases: what happens to the prey population over time?

Prey population increases. Fewer predators means less predation pressure on prey populations.
What interaction is it when two species use the same limited resource and both are negatively affected?

Competition. Both organisms need the same resource, reducing fitness for both.
Which outcome is most likely if a pollinator population declines sharply?

Reproduction of pollinated plants decreases; seed/fruit production drops. Many plants require pollinators for sexual reproduction.
Identify the interaction: barnacles attach to a whale; barnacles benefit and the whale is unaffected.

Commensalism. Barnacles benefit (+) while whale is unaffected (0).
Which outcome is most likely if a predator population increases in a stable system?

Prey population decreases. More predators consume more prey, reducing prey numbers.
What type of interaction is mutualism?

Both species benefit. Mutualism is a (+/+) interaction where both organisms gain fitness.
What is competition in an ecosystem?

Two organisms use the same limited resource. This can lead to reduced fitness for one or both competitors.
What is the term for an organism role that makes its own food using sunlight or chemicals?

Producer (autotroph). These organisms convert light or chemical energy into food through photosynthesis or chemosynthesis.
Which interaction occurs when both species benefit and neither is harmed?

Mutualism. Both organisms gain advantages from the relationship.
What is the most likely population outcome when a limiting resource increases (for example, more nesting sites)?

Population size tends to increase. More resources support larger populations.
Which outcome is most likely if a top predator is removed from a food chain?

Prey populations increase and lower trophic levels may decline. Without predation pressure, prey populations can explode.
Which outcome is most likely if a parasite spreads rapidly through a host population?

Host population decreases; parasite may later decline too. Parasites weaken hosts; their own decline follows host scarcity.
Which outcome is most likely if a drought reduces plant biomass in a grassland?

Herbivore populations decrease, followed by predator decreases. Less food cascades up the food chain, affecting all levels.
Which outcome is most likely if a top predator is removed from a food web?

Prey populations increase and lower trophic levels may decrease. Without predation pressure, prey multiply unchecked.
Which outcome is most likely if a disease reduces a dominant competitor species in an ecosystem?

Other competing species increase due to reduced competition. Removing a dominant competitor frees resources for others.
What is the term for an organism role that makes its own food using sunlight or chemicals?

Producer (autotroph). These organisms convert light or chemical energy into food energy.
Identify the interaction type: a tick feeds on a dog and harms the dog.

Parasitism. The tick benefits while the dog suffers blood loss and disease risk.
Identify the outcome if a prey population sharply decreases: what happens to the predator population over time?

Predator population decreases. Less prey means less food available for predators to survive and reproduce.
What is the most likely outcome for a parasite population if its host population declines greatly?

Parasite population tends to decrease. Parasites depend on hosts; fewer hosts means fewer parasites.
Identify the likely outcome when two species occupy the same niche and a key resource becomes scarce.

Competition increases and one population may decline. Limited resources intensify competition, often eliminating the weaker competitor.
Which option best describes a limiting factor: a condition that restricts population growth?

A resource or condition that limits population size. Any factor that prevents unlimited population growth in an ecosystem.
What is a predator-prey interaction?

One organism kills and eats another organism. The predator benefits by gaining energy while the prey dies.
What type of interaction is it when one benefits and the other is harmed but not killed?

Parasitism. Parasite benefits while weakening but not killing its host.
Which trophic level is most directly affected first if producers decline sharply?

Primary consumers. Herbivores directly depend on producers for food.
Which option best predicts what happens to prey population when predators increase and other factors stay constant?

Prey population decreases. More predators consume prey faster than they can reproduce.
What interaction is shown when both species are harmed (−/−) ?

Competition. Both organisms are harmed by competing for resources.
Which population changes first if a producer population suddenly decreases sharply?

Primary consumers decrease first. Herbivores directly depend on producers for food.
Which type of interaction is shown when one benefits and one is harmed (+/−)?

Predation or parasitism. One organism benefits at the expense of another.
What is the term for an organism that makes its own food using sunlight or chemicals?

Producer (autotroph). These organisms convert light or chemical energy into food through photosynthesis or chemosynthesis.
What type of interaction is competition?

Organisms compete for the same limited resource. Both organisms need the same resource that's in short supply.
Which interaction benefits both species involved?

Mutualism. Both species gain fitness advantages from the relationship.
Identify the most likely outcome if a parasite spreads quickly through a host population.

Host population decreases; parasite may later decline. Parasites weaken hosts; their own numbers may fall if hosts die.
Identify the interaction: a barnacle attaches to a whale and the whale is unaffected.

Commensalism. Barnacles gain transport and feeding opportunities without affecting the whale.
Which outcome is most likely if a drought reduces available water for plants?

Producer population decreases; consumers decline due to less food. Water stress limits photosynthesis, cascading up the food chain.
What is the role of a scavenger in an ecosystem?

Consumer that eats dead organisms but does not chemically decompose them. Feeds on already-dead organisms without breaking them down chemically.
Identify the interaction: barnacles live on a whale and the whale is not harmed or helped.

Commensalism. Barnacles gain transport and feeding opportunities without affecting whale.
Which outcome is most likely when decomposers are reduced in an ecosystem?

Nutrients recycle more slowly and plant growth decreases. Without decomposers, dead matter accumulates and nutrients remain locked.
What type of interaction is parasitism?

Parasite benefits; host is harmed. The parasite depends on but weakens its host organism.
Which outcome is most likely if a keystone species is removed from its ecosystem?

Large community changes; some populations crash and biodiversity decreases. Keystone species have disproportionate ecosystem impact.
Identify the interaction type: clownfish gains shelter in anemone, anemone is unaffected.

Commensalism. The fish gains protection without affecting the anemone.
What is the outcome for predator population when prey population sharply decreases, assuming no alternate prey?

Predator population tends to decrease. Without enough food, predators starve and die off.
What is the ecological role of a producer in an ecosystem?

An organism that makes its own food, usually by photosynthesis. They convert light energy into chemical energy at the base of food chains.
What type of interaction is predation?

Predator kills and eats prey. One organism hunts and consumes another for energy.
Which outcome is most likely when an invasive species uses the same niche as a native species?

Native population decreases due to stronger competition. Invasive species often outcompete natives for same resources.
Which outcome is most likely if primary consumers drop sharply: producer biomass increases or decreases?

Producer biomass increases. Fewer herbivores means less grazing pressure on plants.
Which outcome is most likely if a limiting resource becomes more scarce?

Competition increases and population growth decreases. Scarcity intensifies struggle for resources, limiting growth.
Which outcome is most likely when two species compete for the same limited food source?

Both populations decrease or one is outcompeted. Competition for scarce resources harms both species.
Which outcome is most likely if a pollinator population declines in a flowering plant community?

Plant reproduction decreases and plant population may decline. Many plants depend on pollinators for reproduction.
What is the role of a producer in an ecosystem food web?

Makes its own food; base energy source for other organisms. Producers convert sunlight into chemical energy through photosynthesis.
What is the organism role that makes its own food using sunlight or chemicals?

Producer (autotroph). Uses photosynthesis or chemosynthesis to convert energy into food.
What type of interaction occurs when one species benefits and the other is unaffected?

Commensalism. One organism gains while the other neither benefits nor suffers harm.
What is the ecological role of a producer in a food web?

Makes its own food; base energy source for other organisms. Producers convert sunlight into chemical energy through photosynthesis.
Which population is most likely to increase if a top predator is removed from a food web?

Its prey population increases. Removing predators releases pressure on their prey species.
Which interaction occurs when one species benefits and the other is harmed?

Parasitism. The parasite gains nutrients while weakening its host.
Which outcome is most likely if extra nitrogen fertilizer enters a lake ecosystem?

Algal blooms increase and dissolved oxygen can decrease. Excess nutrients cause eutrophication and oxygen depletion.
Which option best predicts the effect of a cold winter that kills many insects on insect-eating birds?

Bird population decreases due to less prey. Insectivores lose their primary food source when cold kills insects.
Which outcome is most likely if a top predator is removed: what happens to herbivores and then producers?

Herbivores increase; producers decrease. Trophic cascade: removing predators releases herbivore pressure on plants.
Which outcome is most likely if producers increase greatly in a pond ecosystem?

Primary consumer population increases (more food available). Bottom-up effect as more plant biomass supports more herbivores.
Identify the interaction: a tick feeds on a dog and the dog is harmed.

Parasitism. The tick benefits by feeding on blood while the dog suffers health impacts.
Identify the interaction: bees get nectar and flowers get pollinated.

Mutualism. Both species benefit: bees get food, flowers reproduce.
Which outcome is most likely if winter temperatures become milder for a tick population?

Tick survival increases, raising parasite pressure on hosts. Warmer winters reduce tick mortality, increasing populations.
Identify the interaction: a tick feeds on a dog, harming the dog while benefiting the tick.

Parasitism. The tick benefits (+) while the dog is harmed (−).
Which option best predicts what happens to predator numbers when prey becomes more abundant over time?

Predator numbers increase after a time lag. More prey supports larger predator populations over time.
What interaction is defined as both species benefiting?

Mutualism. Both organisms gain advantages from their relationship (+/+ interaction).
What is the ecological role of a decomposer?

Breaks down dead matter and recycles nutrients to the ecosystem. Essential for nutrient cycling and soil enrichment.
Which outcome is most likely if sunlight increases and water is sufficient for plants?

Producer growth increases; higher-level consumer populations may increase. More light energy drives photosynthesis and ecosystem productivity.
What is the term for an organism role that gets energy by eating other organisms?

Consumer (heterotroph). Must consume other organisms because they cannot produce their own food.
Which outcome is most likely if average winter temperature increases for an insect pest?

Pest survival increases; crop damage often increases. Warmer winters allow more pests to survive until spring.
Identify the interaction: two plant species use the same soil nitrogen in a dry season.

Competition. Limited nitrogen forces both species to compete for survival.
Which term names a living environmental factor such as predators or disease?

Biotic factor. Living organisms that influence other organisms in the ecosystem.
Which outcome is most likely if an invasive predator enters an ecosystem with no natural enemies?

Native prey populations decline and biodiversity often decreases. Unchecked predation disrupts established food web balance.
What interaction occurs when one species benefits and the other is unaffected, such as barnacles on a whale?

Commensalism. One organism gains a benefit while the other experiences no effect (+/0 relationship).
Which interaction occurs when one species benefits and the other is unaffected?

Commensalism. One organism gains benefits without affecting the other.
Identify the most likely outcome if a predator population increases while prey stays constant.

Prey population decreases. More predators consume more prey, reducing prey numbers.
Which outcome is most likely if a keystone predator is removed from a community?

One prey species may overpopulate and reduce biodiversity. Keystone species control prey populations and maintain diversity.
What is the term for an organism role that gets energy by eating other organisms?

Consumer (heterotroph). Cannot produce their own food, so must consume other organisms for energy.
Identify the interaction: a tick feeds on a dog's blood and the dog is harmed.

Parasitism. Tick benefits from blood meal while dog loses nutrients and may get diseases.
Which type of interaction is shown when both species benefit (+/+)?

Mutualism. Both organisms gain benefits from their interaction.
Which option best describes predation?

One organism kills and eats another organism. Predators consume prey for energy, resulting in prey death.
What is the ecological role of a producer in an ecosystem?

Organism that makes its own food, usually by photosynthesis. Forms the base of food chains by converting sunlight to chemical energy.
What interaction occurs when both species benefit, such as a bee gaining nectar and a flower being pollinated?

Mutualism. Both organisms gain fitness advantages from their interaction (+/+ relationship).
Choose the most likely outcome if an invasive predator is introduced with no natural enemies.

Native prey populations decline rapidly. Without predators to control them, invasive species devastate prey.
Which outcome is most likely if a keystone species population is greatly reduced?

Large community changes and reduced ecosystem stability. Keystone species have disproportionate effects on ecosystem structure.
Which outcome is most likely if a drought reduces plant biomass in a grassland?

Herbivore populations decrease due to reduced food supply. Less plant biomass means less food for herbivores.
What interaction occurs when one organism kills and eats another organism?

Predation. Predator gains energy while prey loses its life (+/- relationship).
Which interaction is described by a predator killing and eating prey?

Predation. One organism hunts and consumes another for food.
Which outcome is most likely if a new competitor uses the same food as a native species?

Native population decreases due to increased competition. The new species outcompetes natives for limited resources.
Which outcome is most likely if an invasive predator is introduced with no natural enemies?

Native prey populations decline rapidly. Without predator control, invasive species devastate prey.
Which outcome is most likely if more decomposers are added to soil with abundant dead leaves?

Decomposition speeds up and soil nutrients increase. More decomposers process dead matter faster into nutrients.
What is a primary consumer?

An organism that eats producers (an herbivore). They occupy the second trophic level by feeding directly on plants.
Identify the most likely outcome if decomposers decrease in an ecosystem.

Nutrient recycling slows; soil nutrients decline. Fewer decomposers means dead matter accumulates, nutrients stay locked.
Identify the most likely outcome if an invasive predator enters a new habitat with no predators.

Native prey populations decline rapidly. Prey lack defenses against unfamiliar predators.
What is the ecological role of a primary consumer?

Herbivore that eats producers. First-level consumers that transfer energy from plants to higher trophic levels.
What is the term for an organism role that makes its own food using sunlight or chemicals?

Producer (autotroph). They convert light or chemical energy into food through photosynthesis or chemosynthesis.
What interaction is defined as one species benefiting while the other is unaffected?

Commensalism. One organism gains benefits without helping or harming the other (+/0 interaction).
What is the most likely outcome if decomposers decline greatly in an ecosystem?

Nutrient recycling slows; plant growth decreases. Without decomposers, nutrients remain locked in dead matter.
Which outcome is most likely if decomposers are reduced in an ecosystem?

Nutrients recycle more slowly and dead matter accumulates. Without decomposers, dead material isn't broken down efficiently.
What is the ecological role of a scavenger?

Consumes dead animals without breaking them down chemically. Different from decomposers - they don't chemically break down tissue.
Identify the immediate outcome if a limiting resource becomes scarce for two species sharing it.

Competition increases. Limited resources intensify competition between species.
Which outcome is most likely if a new competitor uses the same food source as a native species?

The native species population decreases from increased competition. Sharing resources reduces availability for each species.
Which interaction benefits one species while harming the other without immediate killing?

Parasitism. The host is weakened but kept alive for continued exploitation.
Which outcome is most likely if a predator population increases while prey stays constant?

Prey decreases over time due to higher predation pressure. More predators consume more prey, reducing prey numbers.
What type of interaction is commensalism?

One benefits and the other is unaffected. Commensalism is a (+/0) interaction with no harm or benefit to one partner.
Which option best predicts what happens to algae when fertilizer runoff increases into a pond?

Algae increase rapidly (algal bloom). Excess nutrients fuel rapid algae growth, creating dense blooms.
What type of interaction occurs when one species benefits and the other is harmed, usually not killed?

Parasitism. The parasite feeds on the host, weakening but typically not killing it.
Which outcome is most likely if a prey population crashes due to disease?

Predator population decreases after a time lag. Predators depend on prey for food; less prey means fewer predators.
Which outcome is most likely if a mutualistic partner is removed (for example, a pollinator disappears)?

The other species' reproduction and population decrease. Many mutualists depend on partners for essential services.
Identify the interaction: barnacles live on whales; whales are not affected.

Commensalism. Barnacles gain habitat; whales neither benefit nor suffer.
Which outcome is most likely when two herbivore species share the same food and that food becomes scarce?

Competition increases; at least one population declines. Limited food forces species to compete, reducing survival.
Which outcome is most likely when a new top predator is introduced into an ecosystem?

Prey populations decrease and the food web may shift. New predation pressure disrupts existing population balances.
What is a secondary consumer?

An organism that eats primary consumers. They occupy the third trophic level in food chains.
Choose the outcome if a drought reduces plant biomass: what happens to herbivores first?

Herbivore population decreases due to less food. Herbivores starve when plant food becomes scarce.
Which type of limiting factor includes weather events like drought, floods, and temperature extremes?

Density-independent factor. Affects populations regardless of their density or size.
Which outcome is most likely when a limiting nutrient increases in a lake (fertilizer runoff)?

Algal bloom increases; oxygen can drop as algae decompose. Excess nutrients cause rapid algae growth and later decay.
Which interaction benefits one species and neither helps nor harms the other?

Commensalism. One gains while the other is unaffected (+/0 interaction).
What type of interaction is parasitism?

Parasite benefits; host is harmed. Parasitism is a (+/-) interaction where one organism exploits another.
Identify the interaction: bees get nectar and flowers get pollinated.

Mutualism. Both species gain: bees get food and flowers achieve reproduction.
What is the most likely ecosystem outcome when an invasive species has no predators and uses the same food as natives?

Invasive increases; native competitors decline. Without predators, invasives outcompete native species.
What interaction occurs when one species benefits and the other is harmed, such as a tick feeding on a deer?

Parasitism. Parasite gains nutrients while host loses resources or health (+/- relationship).
What is the role of decomposers in an ecosystem's matter cycle?

They break down dead matter and recycle nutrients. Essential for returning nutrients to soil for producer use.
Which outcome is most likely when a limiting resource becomes more scarce: competition increases or decreases?

Competition increases. Less resource availability intensifies struggle between organisms.
Which outcome is most likely if a mutualistic partner disappears, such as loss of pollinators for a plant species?

The dependent partner's reproduction decreases. Loss of mutualist removes essential service like pollination or seed dispersal.
What is a consumer in an ecosystem?

An organism that obtains energy by eating other organisms. Consumers depend on other organisms for their energy source.
Identify the most likely outcome if a new predator is introduced to an ecosystem with abundant prey.

Prey decreases; predator increases at first. More food allows predator numbers to grow, while prey numbers decline from hunting.
What is the role of a consumer in an ecosystem?

Organism that gets energy by eating other organisms. Cannot produce their own food, so must consume other organisms.
What is a decomposer in an ecosystem?

An organism that breaks down dead matter and recycles nutrients. Decomposers complete the nutrient cycle by returning elements to soil.
Identify the outcome if an invasive predator enters an ecosystem with abundant prey and few natural enemies.

Prey decreases; invasive predator increases. Abundant food and no enemies allow invasive predator populations to explode.
What type of interaction is predation?

Predator kills and eats prey. Predation is a (+/-) interaction involving consumption of prey.
Identify the outcome if a parasite becomes more common in a host population: what happens to host health and survival?

Host health and survival decrease. Parasites weaken hosts by taking nutrients and potentially spreading disease.
Which option best predicts what happens when an invasive species has no natural predators in a new habitat?

Invasive population increases rapidly and reduces native species. No predators allows unchecked growth, outcompeting natives for resources.
Which outcome is most likely if fertilizer runoff causes an algal bloom in a lake?

Oxygen decreases; fish and other aerobic organisms may die. Algae decomposition depletes oxygen through bacterial respiration.
Which outcome is most likely if nutrient levels in a lake rise sharply due to fertilizer runoff?

Algal blooms increase; dissolved oxygen can decrease. Excess nutrients cause algae overgrowth, depleting oxygen.
Which outcome is most likely if a disease reduces a top predator population?

Prey increase; producers may decline due to higher grazing pressure. Fewer predators allow prey to multiply and overgraze plants.
Which outcome is most likely if a disease sharply reduces a prey population?

Predator population decreases after the prey decline. Less prey means less food for predators to survive.
Which population usually decreases first if a disease strongly reduces a prey species: predator or prey?

Predator population decreases after prey declines. Predators depend on prey for food, so they decline after prey drops.
What type of interaction occurs when organisms need the same limited resource?

Competition. Organisms vie for resources like food, water, or space.
Which option best predicts what happens to oxygen in water if many algae die and decomposers increase?

Dissolved oxygen decreases due to decomposer respiration. Bacteria consume dead algae, using up oxygen through cellular respiration.
What interaction is it when both species benefit and neither is harmed?

Mutualism. Both organisms gain advantages from their relationship.
Which outcome is most likely if decomposers are reduced in a forest ecosystem?

Dead matter accumulates and nutrient availability decreases. Without recycling, nutrients remain locked in dead organisms.
What interaction is defined as both species being harmed because they use the same limited resource?

Competition. Both organisms suffer reduced fitness when competing for scarce resources (-/- interaction).
What type of interaction occurs when both species benefit and neither is harmed?

Mutualism. Both organisms gain advantages from their relationship.
What is the ecological role of a decomposer?

Breaks down dead matter and recycles nutrients to the environment. Essential for nutrient cycling and soil fertility.
Which option best defines a niche for an organism?

Its role and resource use in its ecosystem. A niche includes all ways an organism interacts with its environment.
What is the role of a decomposer in an ecosystem?

Breaks down dead matter and recycles nutrients. Essential for nutrient cycling, returning elements to soil.
Which population is most likely to decrease first during a drought: producers or top predators?

Producers. Water stress affects photosynthesis before impacting higher trophic levels.
Identify the interaction outcome when a parasite spreads more easily in crowded host populations.

Parasitism increases; host health and numbers decline. Close proximity facilitates parasite transmission between hosts.
Which outcome is most likely if two species compete for the same food and that food becomes scarce?

Both populations decrease. Limited resources cannot support both populations at previous levels.
What is the outcome for prey population when predator population increases, assuming other factors stay similar?

Prey population tends to decrease. More predators means more prey are hunted and eaten.
What interaction is described when one benefits and one is harmed (+/−)?

Parasitism or predation. One organism benefits at the expense of another's health or life.
What is the term for a nonliving environmental factor (such as temperature, light, or water) that affects organisms?

Abiotic factor. Physical and chemical conditions that influence living things.
Identify the outcome when pollinator populations decline in a flowering plant community.

Plant reproduction decreases; plant population may decline. Without pollinators, plants cannot produce seeds effectively.
What is competition in ecology?

Organisms vie for the same limited resource. Competition is a (-/-) interaction that reduces fitness for both species.
Which term names a nonliving environmental factor such as temperature or rainfall?

Abiotic factor. Physical and chemical conditions that affect organisms.
What is the role of a primary consumer in a food chain?

Eats producers (herbivore). Primary consumers feed directly on plants, the first energy transfer.
What is the most likely population outcome when a key predator is removed from a food web?

Prey population increases (often leading to overuse of its food). Loss of top-down control releases prey from predation pressure.
What is the role of a primary consumer in a food chain?

Herbivore that eats producers. Primary consumers occupy the second trophic level by eating plants.
What interaction is described when one benefits and the other is unaffected (+/0)?

Commensalism. One species gains while the other experiences no impact.
What type of interaction is commensalism?

One benefits; the other is unaffected. One organism gains while causing no harm or help to the other.
What type of interaction is mutualism?

Both species benefit. A win-win relationship where both organisms gain advantages.
Which outcome is most likely if two species compete for the same limited food source?

At least one population decreases due to reduced resource access. Competition reduces available resources for both species.
Identify the outcome if a decomposer population decreases in a forest: what happens to dead organic matter and soil nutrients?

Dead matter increases; soil nutrients decrease. Without decomposers, dead matter accumulates and nutrients remain locked up.
Which outcome best predicts what happens to decomposer activity when temperature becomes much colder?

Decomposer activity decreases; nutrient recycling slows. Cold slows decomposer metabolism and breakdown processes.
What is the most likely effect of a severe drought on plant-eating animals in that ecosystem?

Herbivore populations decrease due to less plant food. Drought reduces plant growth, limiting herbivore food supply.
Which outcome is most likely if an invasive predator enters an ecosystem with no natural predators?

Native prey populations decrease rapidly. Without natural controls, invasive predators overconsume prey.
What interaction is shown when one benefits and the other is unaffected (+/0) ?

Commensalism. One organism benefits without affecting the other.
What term describes an organism that must obtain energy by eating other organisms?

Consumer (heterotroph). Cannot produce their own food, so they consume other organisms for energy.
Which abiotic factor change most directly reduces photosynthesis in producers?

Decreased sunlight. Light is essential for photosynthesis to produce glucose.
What is a limiting factor in an ecosystem?

A condition that restricts population growth, such as food or water. These factors control population size when scarce.
What type of interaction occurs when one species benefits and the other is unaffected?

Commensalism. One organism gains a benefit without affecting the other.
What type of interaction is it when one benefits and the other is unaffected?

Commensalism. One organism gains while causing no harm or benefit to the other.
What interaction is it when one species benefits and the other is harmed without being killed?

Parasitism. The parasite feeds on but doesn't kill its host.
Which outcome is most likely when a limiting resource becomes abundant for a population?

Population increases until a different limiting factor slows growth. Populations grow until another resource becomes limiting.
Which option best predicts the effect of fewer producers on consumers in a food web?

Consumer populations generally decrease. Less food energy flows up the food chain when primary production drops.
What is the role of a decomposer in matter cycling?

Breaks down dead matter and returns nutrients to the ecosystem. Decomposers recycle organic matter into inorganic nutrients for producers.
Which outcome is most likely if decomposers are greatly reduced in an ecosystem?

Nutrient recycling slows; soil fertility and producer growth decrease. Dead matter accumulates without decomposers to process it.
Which outcome is most likely if an invasive plant outcompetes native plants for light?

Native plant populations decrease; dependent herbivores may decline. Invasive species often outcompete natives for limited resources.
What is the organism role that breaks down dead matter and recycles nutrients to the ecosystem?

Decomposer. Essential for nutrient cycling by breaking down organic matter into simpler compounds.
Which outcome is most likely if a drought reduces available water for plants in a grassland?

Producer biomass decreases; herbivores decline afterward. Water stress reduces plant growth, affecting dependent herbivores.
What is competition in ecology, in terms of shared limiting resources?

A struggle between organisms for the same limited resource. Organisms compete when resources are insufficient for all.
Identify the outcome when a key predator is removed from an ecosystem.

Prey increase; producers often decrease (trophic cascade). Without predation control, prey multiply and overgraze plants.
Which option best predicts what happens to herbivores if plant (producer) biomass decreases?

Herbivore population decreases due to less food. Plant-eaters depend on producers; fewer plants means less food available.
Which outcome is most likely if a keystone predator is removed from a food web?

Prey increases; lower trophic levels may decline. Without predation control, prey populations explode.
Which interaction is indicated when both populations increase because each provides a needed resource?

Mutualism. Mutual population growth indicates reciprocal benefits.
Which option best predicts what happens to producers during a long drought with little rainfall?

Producer population decreases due to limited water. Plants need water for photosynthesis; drought reduces their growth and survival.
What is the ecological role of a decomposer in an ecosystem?

An organism that breaks down dead matter and recycles nutrients. They complete nutrient cycles by breaking down organic matter.
Which outcome is most likely if a disease sharply lowers the rabbit population in a meadow?

Rabbit predators decrease; plants eaten by rabbits increase. Loss of prey affects predators; loss of herbivores helps plants.
Which option best defines a habitat for an organism?

The place where an organism lives. A habitat provides the physical environment an organism needs.
Which outcome is most likely if a keystone predator increases in number in its ecosystem?

Prey decreases; community balance and diversity may increase. Keystone predators control prey, maintaining ecosystem balance.
Identify the interaction: bees get nectar while pollinating flowers, benefiting both species.

Mutualism. Both bees (+) and flowers (+) gain from this interaction.
What interaction occurs when two species use the same limited resource, reducing success for both?

Competition. Both organisms are negatively affected when competing for the same resource (-/- relationship).
Which outcome is most likely if a disease greatly reduces a prey population?

Predator population decreases after the prey decline. Loss of food source causes starvation in dependent predators.
What interaction is defined as one species benefiting and the other being harmed?

Parasitism. The parasite gains nutrients while weakening or damaging its host (+/- interaction).
Which outcome is most likely if a disease reduces a keystone predator population?

Prey increase and the food web becomes less stable. Keystone predators control prey that would otherwise dominate.
What interaction is shown when one benefits and one is harmed (+/−) ?

Parasitism. Parasite benefits while host is harmed by the relationship.
What is the ecological role of a primary consumer?

Herbivore that eats producers. First-level consumers feed directly on plants or algae.
What is the organism role that eats producers or other consumers for energy?

Consumer (heterotroph). Must obtain energy by consuming other organisms.
Which interaction is most likely when two species require the same limiting resource?

Competition. Limited resources force organisms to compete for survival.
Which option best predicts what happens to decomposer activity when temperature becomes much colder?

Decomposition rate decreases. Cold slows bacterial and fungal metabolism, reducing breakdown of organic matter.
Identify the most likely outcome if sunlight is reduced in a pond by heavy algae growth.

Submerged plants decrease due to reduced photosynthesis. Algae blocks light needed for underwater photosynthesis.
What is the role of a decomposer in an ecosystem?

Organism that breaks down dead matter and recycles nutrients. Essential for nutrient cycling by breaking down organic matter.
Which outcome is most likely if a prey population sharply decreases?

Predator population decreases after a time lag. Less food causes predator starvation and population decline.
Identify the limiting factor if a plant population stops growing due to low nitrogen.

Soil nutrients (nitrogen) are the limiting factor. Growth stops when essential nutrients become scarce.
Which interaction occurs when organisms compete for the same limited resource?

Competition. Both organisms are harmed by fighting for scarce resources.
Identify the interaction if two bird species use the same nesting sites and food source.

Competition. Sharing limited resources creates competitive pressure.
Which outcome is most likely if pollinator numbers drop in a flowering plant community?

Plant reproduction decreases and plant populations may decline. Many plants depend on pollinators for sexual reproduction.
Which option best predicts what happens to two species that compete for the same limited food source?

Both populations decrease or one outcompetes the other. Competition reduces resources for both, causing population decline or competitive exclusion.
What is parasitism?

One species benefits and the host is harmed. The parasite gains nutrients while weakening its host.
What type of interaction is competition between two species for the same limited resource?

Competition. Both species are harmed by reduced access to the resource.
Which outcome is most likely if a producer population drops sharply: primary consumers increase or decrease?

Primary consumers decrease. Herbivores lose their food source when plants decline.
Which outcome is most likely when a keystone species population decreases significantly?

Community structure changes greatly; biodiversity often drops. Keystone species disproportionately affect ecosystem balance.
Identify the most likely outcome when two species have identical niches in one habitat.

One species will outcompete the other (competitive exclusion). Two species cannot coexist if they compete for identical resources.
What interaction is it when one organism kills and eats another organism?

Predation. One organism (predator) hunts and consumes another (prey).
What is the term for an organism that must eat other organisms for energy?

Consumer (heterotroph). Cannot produce their own food, so they obtain energy by consuming other organisms.
Identify the outcome when a drought reduces plant biomass in a grassland food web.

Herbivores decrease; predators decrease afterward. Less food causes herbivore starvation, then predator starvation.
Which outcome is most likely after a drought reduces plant growth: what happens to herbivores first?

Herbivore population decreases. Primary consumers depend directly on producers for food.
Identify the outcome when decomposers are reduced in soil after pesticide exposure.

Nutrients recycle more slowly; plant growth decreases. Dead matter accumulates without decomposers to break it down.
What is the ecological role of a secondary consumer?

Carnivore or omnivore that eats primary consumers. Second-level consumers that control herbivore populations.
What type of interaction is it when one organism kills and eats another organism?

Predation. One organism (predator) consumes another (prey) for energy.
Identify the outcome if a keystone mutualism is disrupted (for example, cleaner fish removed).

Partner species health declines; community balance can shift. Removing one mutualist harms its dependent partner species.
Identify the most likely outcome if a prey population increases while predator numbers are low.

Predator population increases after a time lag. Abundant prey supports predator reproduction and growth.
What is a producer in an ecosystem?

An organism that makes its own food (usually by photosynthesis). Producers convert light energy into chemical energy through photosynthesis.
What is the ecological role of a secondary consumer?

Carnivore or omnivore that eats primary consumers. Second-level consumers occupy the third trophic level.
Identify the outcome when an invasive predator is introduced and native prey have no defenses.

Native prey declines; predator may increase rapidly. Defenseless prey are easily caught, boosting predator reproduction.
Identify the most likely outcome if the prey population sharply decreases in a predator-prey relationship.

Predator population decreases after a time lag. Less food causes predator starvation, but the effect isn't immediate.
What is the difference between a predator and a prey organism?

Predator hunts and eats; prey is hunted and eaten. Energy flows from prey to predator through consumption.
Which outcome is most likely after a drought reduces water availability for many species in an area?

Competition for water increases; some populations decline. Limited water forces organisms to compete for survival.
What interaction is defined as a predator killing and eating prey?

Predation. One organism kills another for food, benefiting predator while harming prey (+/- interaction).
Identify the most likely outcome if a top predator is removed from a food web.

Prey increases; producers often decrease (trophic cascade). Without predation pressure, prey multiply and overgraze plants.
What is the role of a producer in an ecosystem food web?

Makes its own food, usually by photosynthesis. Producers form the base of food webs by converting sunlight to energy.
Which option best describes parasitism?

A parasite benefits while the host is harmed, usually not killed quickly. Parasites live on/in hosts, taking resources without immediate killing.
Which outcome is most likely if decomposers are reduced in a forest ecosystem?

Nutrients recycle more slowly; plant growth decreases over time. Fewer decomposers means slower nutrient cycling to producers.
Which option best predicts what happens to a predator population if its prey population drops?

Predator population decreases after a time lag. Less prey means less food, causing predator decline.
Which outcome is most likely if an invasive predator enters an ecosystem with abundant prey and few defenses?

Native prey declines; predator increases initially. Easy prey allows predator growth until prey becomes scarce.
What is the role of decomposers in an ecosystem?

Break down dead matter and recycle nutrients. They convert dead organisms into simple nutrients that producers can reuse.
Which type of limiting factor becomes stronger as population density increases, such as disease or competition?

Density-dependent factor. Impact intensifies as population density increases due to crowding effects.
What is the term for an organism role that must eat other organisms for energy?

Consumer (heterotroph). They cannot produce their own food and depend on consuming other organisms.
What type of interaction occurs when both species benefit?

Mutualism. Both organisms gain advantages from their relationship, like cleaner fish and sharks.
Which outcome is most likely if a mutualistic pollinator population declines in a flowering plant community?

Plant reproduction decreases and plant population may drop. Plants need pollinators to reproduce and maintain populations.
What is the ecological role of a consumer in an ecosystem?

An organism that obtains energy by eating other organisms. They transfer energy up the food chain by feeding on other organisms.
Identify the outcome for soil nutrients when decomposers are greatly reduced in an ecosystem.

Nutrient recycling slows and soil nutrients decline. Without decomposers, dead matter accumulates and nutrients remain locked up.
What is the organism role that breaks down dead matter and recycles nutrients?

Decomposer. Returns nutrients to soil by breaking down organic matter.

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