Vocabulary & Ecosystem Roles
What type of organism captures energy from sunlight to manufacture its own food?
A producer (or autotroph)
As energy moves up through the trophic levels in an energy pyramid, what happens to the amount of available energy?
The available energy decreases at each higher level
In a food web diagram, what do the directional arrows represent?
The flow of energy (from the organism being eaten to the organism consuming it)
True or False: Higher-level consumers generate their own energy when food is scarce.
False (Energy cannot be created by organisms; it is transferred or transformed)
A prolonged drought significantly reduces the amount of grass in a prairie. What will immediately happen to the primary consumer populations (rabbits and mice)?
Their populations will decrease due to reduced available food and energy
How do consumers obtain the energy and matter they need to survive?
By eating other living (or once-living) organisms
What main form of unusable energy is given off by organisms during their life processes?
Heat energy
In a marine ecosystem containing algae, baby fish, large tuna, and killer whales, which organism belongs at Trophic Level 4?
Killer whales
True or False: Lower-level consumers pass all of their food energy directly to the organisms that eat them.
False (Most energy is used for body processes or given off as heat)
If a disease wipes out the frog population in a pond, how might this affect the insect population and the snake population?
Insect populations may increase (fewer predators), while snake populations may decrease or seek alternative prey
What chemical process do producers use to convert light energy into stored sugar molecules?
Photosynthesis
Approximately what percentage of energy is transferred from one trophic level up to the next? What happens to the rest of the energy?
About 10% (the remaining ~90% is used for life processes or lost as heat)
In the marine food chain (Algae → Sardines → Tuna → Killer Whales), which organism is the primary consumer?
Sardines
True or False: Grass extracts energy and matter directly from the nonliving environment (sunlight, air, soil, water).
True
A large volcanic eruption spews ash that blocks sunlight across a region for months. Explain why this affects carnivores even though they do not eat plants.
Without sunlight, producers cannot perform photosynthesis, stopping energy flow to herbivores, which leaves carnivores with no food/energy source
An organism that eats only plants (such as a rabbit or grasshopper) is categorized as what level of consumer?
A primary consumer (or first-level consumer)
MATH! If the primary consumers in a rainforest ecosystem contain 700 Joules of available energy, how much energy is available to the tertiary consumers?
7 Joules
In a desert ecosystem with prickly pear cactus, brittlebush, kangaroo rats, harvester ants, moth larva, spiny lizards, rattlesnakes, and coyotes, which organisms are the first-level (primary) consumers?
The kangaroo rat, harvester ant, and moth larva
True or False: Energy lost as heat can be recaptured by plants to perform photosynthesis.
False (Heat is an unusable form of energy for photosynthesis; plants require light energy from the sun)
An environmental scientist measures an energy pyramid and finds 10,000 kJ of energy in producers. Calculate the energy available at Trophic Level 3 (Secondary Consumers).
100 kJ (10,000 kJ → 1,000 kJ at Level 2 → 100 kJ at Level 3)
True or False: Producers and consumers don't need to break down any glucose molecules to release energy for life processes.
False
Why are there far fewer top predators (tertiary consumers) in an ecosystem compared to producers?
Because so much energy is lost as heat at each level, there is not enough energy available at the top of the pyramid to support a large population of top predators.
Identify the inputs and outputs of photosynthesis, and explain what would ultimately happen to an entire ecosystem if plants lost the ability to carry out photosynthesis.
True or False: High-level consumers often rely on multiple organisms in a food web to get enough total energy to live.
True
Why is a food web a more accurate representation of an ecosystem than a single linear food chain?
Because most organisms eat and are eaten by multiple species, making energy pathways interconnected rather than a single line