Interactions Among Living Things
This term describes any living thing in the environment.
Biotic element
Organisms that make their own food using photosynthesis are called this.
Producers
This percentage of energy is typically transferred from one trophic level to the next.
10%
This is the initial source of energy for all food chains and food webs.
The sun
What does it mean that earth is a "closed system"
Matter cannot enter or leave (except for meteorites or other celestial objects).
This is the struggle that happens when organisms try to use the same resources in the same habitat.
Competition
This type of consumer eats only plants, like deer, beavers, and rabbits.
Herbivore (primary consumer)
What percentage of the food that consumers eat becomes gas and waste?
60%
Explain why a food web is a more accurate model of an ecosystem than a single food chain.
Food webs show that producers are usually eaten by many different consumers and most consumers are eaten by more than one predator, showing the complex interconnected feeding relationships in real ecosystems.
Name the 4 main steps of the water cycle.
Evaporation, condensation, precipitation, and collection
In a predator-prey relationship, when the predator population increases, what happens to the prey population.
It decreases (prey population goes down)
What are the three ingredients (raw materials) needed for photosynthesis?
Sun's energy, water, and carbon dioxide
In a pyramid of numbers, what type of organisms should compose the wide base and which should make up the top of the triangle
Producer form the base
Apex/Top predators form the top of the pyramid
A squirrel eats seeds, fruits, and nuts. It can be eaten by foxes, hawks, or raccoons. Explain why this squirrel must be represented in multiple food chains rather than just one.
The squirrel eats multiple types of food (seeds, fruits, nuts) and is eaten by multiple predators (fox, hawk, raccoon), so it appears in several different food chains within the food web. Most organisms in real ecosystems are part of several food chains.
Explain the role of decomposers in converting matter from biotic to abiotic elements.
Decomposers break down dead plants and animals (biotic elements) into simple nutrients and minerals (abiotic elements) that return to the soil.
This type of interaction benefits both species involved, like bees pollinating flowers while collecting nectar.
Mutualism
Explain the difference between detritivores and decomposers.
Detritivores feed on large parts of decaying matter and break it into smaller pieces. Decomposers work at a molecular level to break matter down into the simplest substances.
Explain why food chains rarely exceed 4 levels in an ecosystem.
Only 10% of energy transfers at each level, so there isn't enough energy left to support organisms at higher levels.
In a lake food web, raccoons eat frogs, clams, bird eggs, and corn. Foxes eat mice, grasshoppers, and squirrels. Hawks eat frogs, mice, snakes, and squirrels. If the mouse population suddenly crashed due to disease, explain how this would affect the entire food web, naming at least 3 consequences.
1. Foxes and hawks would have less food and their populations might decrease.
2. They would likely eat more of their other prey (squirrels, grasshoppers, frogs, snakes), putting pressure on those populations. This could cause those prey populations to decrease.
3. The organisms that mice normally eat would increase because fewer mice are eating them.
Energy flow throughout the entire web would be disrupted.
Describe how burning fossil fuels affects the carbon cycle and explain one consequence of this change.
Burning fossil fuels releases carbon into the atmosphere as CO₂.
Since CO₂ is a greenhouse gas, more CO₂ causes Earth to warm, leading to climate change that affects where organisms can live.
Explain why predator and prey populations move in opposite directions on a graph by describing the complete cycle.
When predators increase, they eat more prey so prey decreases. With less prey, predators have less food and starve, so predators decrease. With fewer predators, prey population recovers and increases again.
A scavenger like a coyote finds a dead deer. Describe the complete process of how this matter eventually returns to help plants grow.
Scavengers eat the dead deer, detritivores like earthworms break remaining matter into smaller pieces, decomposers like bacteria and fungi break it down into simple nutrients at a molecular level, these nutrients return to the soil, and plants absorb them.
A grassland ecosystem has 100,000 units of energy stored in grass. Calculate how much energy would be available to a hawk that eats snakes that eat mice. Then explain why a much larger base is needed to support even one top predator.
Grass: 100,000 units
→ Mice: 10,000 units (10%)
→ Snakes: 1,000 units (10%)
→ Hawk: 100 units (10%).
Only 0.1% of the original energy reaches the hawk. This is why top predators need huge territories with thousands of producers and hundreds of prey animals - most energy is lost as heat, waste, and life functions at each level, leaving very little for the top of the pyramid.
A pond ecosystem contains: duckweed, algae, pond lily, Elodea, mayfly larva, mosquito larva, tadpole, freshwater clam, perch, mallard duck, raccoon, osprey, and human. Explain why removing ALL the producers would be more devastating to this ecosystem than removing ALL the top predators (osprey and humans), and predict what would happen in each scenario.
Removing all producers would collapse the entire ecosystem because all energy comes from producers through photosynthesis. Without them, primary consumers would starve and die, then all secondary and tertiary consumers would die - total ecosystem collapse.
Removing top predators would cause prey populations (perch, mallard duck, raccoon) to increase dramatically, which would then overconsume their prey, potentially causing those populations to crash, but the ecosystem's base (producers) would remain intact, allowing eventual rebalancing.
Describe how Carbon is recycled in our atmosphere
Plants take in CO2 and release O2
Animals/Humans take in O2 and release CO2
When animals/humans eat plants, the carbon becomes part of their bodies
When animals/humans die, decomposers break down and release carbon back into the atmosphere
When Humans burn fossil fuels they add additional carbon into the atmosphere