NR 220 Study Guide: Core Concepts &
Principles OA Final Exam Questions with
Correct Solutions|| Updated 2025/2026 A+
Graded||100% Guaranteed Pass!!!
1. Define Environmental Science.
ANSWER ✓ Environmental science is an interdisciplinary field that integrates physical,
biological, and information sciences to study the environment and solve environmental
problems. It includes ecology, biology, geology, chemistry, atmospheric science, and
geography.
2. What is the difference between a hypothesis and a theory?
ANSWER ✓ A hypothesis is a testable, proposed explanation for a phenomenon. A
theory is a well-substantiated, comprehensive explanation of some aspect of nature that
is supported by a vast body of evidence.
3. What are the steps of the scientific method?
ANSWER ✓ Observation, Question, Hypothesis, Prediction, Experiment/Testing, Analysis,
Conclusion.
4. Define sustainability.
ANSWER ✓ Meeting the needs of the present without compromising the ability of future
generations to meet their own needs. It rests on three pillars: environmental, social, and
economic.
5. What is an ecological footprint?
ANSWER ✓ A measure of human demand on Earth's ecosystems, representing the
amount of biologically productive land and water area required to supply the resources
a human population consumes and to absorb its wastes.
,6. What is the difference between renewable and nonrenewable resources?
ANSWER ✓ Renewable resources can be replenished naturally at a rate comparable to
their consumption (e.g., solar energy, timber). Nonrenewable resources exist in a fixed
quantity or are replenished extremely slowly (e.g., fossil fuels, minerals).
Ecology & Ecosystems
7. What is ecology?
ANSWER ✓ The scientific study of the interactions between organisms and their
environment.
8. Define an ecosystem.
ANSWER ✓ A biological community of interacting organisms (biotic) and their physical
environment (abiotic components).
9. What is a producer/autotroph?
ANSWER ✓ An organism that can synthesize its own food from inorganic substances
using light (photosynthesis) or chemical energy (chemosynthesis). E.g., plants, algae.
10. What is a consumer/heterotroph?
ANSWER ✓ An organism that obtains its energy by consuming other organisms. E.g.,
animals, fungi.
11. Differentiate between a food chain and a food web.
ANSWER ✓ A food chain is a linear sequence of energy transfer from producer to
primary, secondary, and tertiary consumers. A food web is a complex, interconnected
network of many food chains in an ecosystem.
12. What is the 10% rule in energy flow?
ANSWER ✓ Only about 10% of the energy stored as biomass in one trophic level is
stored as biomass in the next trophic level. The rest is lost as metabolic heat.
, 13. What is biogeochemical cycling?
ANSWER ✓ The movement of essential chemical elements (like water, carbon, nitrogen,
phosphorus) through living (biotic) and non-living (abiotic) components of the Earth
system.
14. Describe the water cycle.
ANSWER ✓ The continuous movement of water on, above, and below the surface of the
Earth. Key processes: evaporation, transpiration, condensation, precipitation, infiltration,
runoff.
15. Describe the carbon cycle.
ANSWER ✓ The cycle by which carbon is exchanged among the biosphere, geosphere,
hydrosphere, and atmosphere. Key processes: photosynthesis, respiration,
decomposition, combustion, and ocean exchange.
16. Describe the nitrogen cycle.
ANSWER ✓ The process by which nitrogen is converted between its various chemical
forms. Key processes: nitrogen fixation (by bacteria), nitrification, assimilation,
ammonification, and denitrification.
17. What is nitrogen fixation and why is it important?
ANSWER ✓ The process where certain bacteria convert atmospheric nitrogen (N₂) into
ammonia (NH₃), making it usable for plants. It is crucial because plants and animals
cannot use atmospheric nitrogen directly.
18. What is biodiversity?
ANSWER ✓ The variety of life in the world or in a particular habitat or ecosystem. It
includes genetic, species, and ecosystem diversity.
19. What is a keystone species?
ANSWER ✓ A species on which other species in an ecosystem largely depend. If it were
removed, the ecosystem would change drastically. E.g., sea otters, beavers.
Principles OA Final Exam Questions with
Correct Solutions|| Updated 2025/2026 A+
Graded||100% Guaranteed Pass!!!
1. Define Environmental Science.
ANSWER ✓ Environmental science is an interdisciplinary field that integrates physical,
biological, and information sciences to study the environment and solve environmental
problems. It includes ecology, biology, geology, chemistry, atmospheric science, and
geography.
2. What is the difference between a hypothesis and a theory?
ANSWER ✓ A hypothesis is a testable, proposed explanation for a phenomenon. A
theory is a well-substantiated, comprehensive explanation of some aspect of nature that
is supported by a vast body of evidence.
3. What are the steps of the scientific method?
ANSWER ✓ Observation, Question, Hypothesis, Prediction, Experiment/Testing, Analysis,
Conclusion.
4. Define sustainability.
ANSWER ✓ Meeting the needs of the present without compromising the ability of future
generations to meet their own needs. It rests on three pillars: environmental, social, and
economic.
5. What is an ecological footprint?
ANSWER ✓ A measure of human demand on Earth's ecosystems, representing the
amount of biologically productive land and water area required to supply the resources
a human population consumes and to absorb its wastes.
,6. What is the difference between renewable and nonrenewable resources?
ANSWER ✓ Renewable resources can be replenished naturally at a rate comparable to
their consumption (e.g., solar energy, timber). Nonrenewable resources exist in a fixed
quantity or are replenished extremely slowly (e.g., fossil fuels, minerals).
Ecology & Ecosystems
7. What is ecology?
ANSWER ✓ The scientific study of the interactions between organisms and their
environment.
8. Define an ecosystem.
ANSWER ✓ A biological community of interacting organisms (biotic) and their physical
environment (abiotic components).
9. What is a producer/autotroph?
ANSWER ✓ An organism that can synthesize its own food from inorganic substances
using light (photosynthesis) or chemical energy (chemosynthesis). E.g., plants, algae.
10. What is a consumer/heterotroph?
ANSWER ✓ An organism that obtains its energy by consuming other organisms. E.g.,
animals, fungi.
11. Differentiate between a food chain and a food web.
ANSWER ✓ A food chain is a linear sequence of energy transfer from producer to
primary, secondary, and tertiary consumers. A food web is a complex, interconnected
network of many food chains in an ecosystem.
12. What is the 10% rule in energy flow?
ANSWER ✓ Only about 10% of the energy stored as biomass in one trophic level is
stored as biomass in the next trophic level. The rest is lost as metabolic heat.
, 13. What is biogeochemical cycling?
ANSWER ✓ The movement of essential chemical elements (like water, carbon, nitrogen,
phosphorus) through living (biotic) and non-living (abiotic) components of the Earth
system.
14. Describe the water cycle.
ANSWER ✓ The continuous movement of water on, above, and below the surface of the
Earth. Key processes: evaporation, transpiration, condensation, precipitation, infiltration,
runoff.
15. Describe the carbon cycle.
ANSWER ✓ The cycle by which carbon is exchanged among the biosphere, geosphere,
hydrosphere, and atmosphere. Key processes: photosynthesis, respiration,
decomposition, combustion, and ocean exchange.
16. Describe the nitrogen cycle.
ANSWER ✓ The process by which nitrogen is converted between its various chemical
forms. Key processes: nitrogen fixation (by bacteria), nitrification, assimilation,
ammonification, and denitrification.
17. What is nitrogen fixation and why is it important?
ANSWER ✓ The process where certain bacteria convert atmospheric nitrogen (N₂) into
ammonia (NH₃), making it usable for plants. It is crucial because plants and animals
cannot use atmospheric nitrogen directly.
18. What is biodiversity?
ANSWER ✓ The variety of life in the world or in a particular habitat or ecosystem. It
includes genetic, species, and ecosystem diversity.
19. What is a keystone species?
ANSWER ✓ A species on which other species in an ecosystem largely depend. If it were
removed, the ecosystem would change drastically. E.g., sea otters, beavers.
