BIO 220 — Ecology and Environmental Science

Question 1: What term describes all the members of one species living in a given area?

•          Community

•          Population

•          Ecosystem

•          Biome

Explanation: A population refers to all individuals of a single species occupying a specific geographic area at a given time, capable of interbreeding and sharing a common gene pool.

Question 2: Which trophic level do primary producers occupy?

•          First

•          Second

•          Third

•          Fourth

Explanation: Primary producers, such as plants and algae, occupy the first trophic level because they convert sunlight or inorganic compounds into usable energy through photosynthesis or chemosynthesis, forming the base of the food chain.

Question 3: Energy transfer between trophic levels is approximately 100% efficient.

•          True

•          False

Explanation: On average only about 10% of energy is transferred from one trophic level to the next, as the rest is lost as heat through metabolic processes, which is why food chains rarely extend beyond four or five levels.

Question 4: Which type of species interaction benefits one organism while harming the other?

•          Mutualism

•          Commensalism

•          Parasitism

•          Competition

Explanation: In parasitism, one organism, the parasite, benefits by extracting resources from a host organism, which is harmed in the process, as seen with tapeworms living inside a host's digestive tract.

Question 5: What is the term for the physical space and set of environmental conditions in which an organism lives?

•          Niche

•          Habitat

•          Biome

•          Range

Explanation: A habitat is the specific physical environment, including its climate, resources, and physical features, in which a particular species naturally lives and finds the conditions needed to survive.

Question 6: Which biogeochemical cycle involves the conversion of atmospheric N2 into forms usable by plants?

•          Carbon cycle

•          Nitrogen cycle

•          Phosphorus cycle

•          Water cycle

Explanation: The nitrogen cycle includes nitrogen fixation, in which bacteria convert inert atmospheric nitrogen gas into ammonia or related compounds that plants can absorb and use to build proteins and nucleic acids.

Question 7: A keystone species has a disproportionately large effect on its ecosystem relative to its abundance.

•          True

•          False

Explanation: Keystone species, such as sea otters or wolves, exert outsized influence on community structure; their removal can trigger dramatic changes in species composition even though they may be relatively few in number.

Question 8: What describes the maximum population size an environment can sustainably support?

•          Biotic potential

•          Carrying capacity

•          Population density

•          Limiting factor

Explanation: Carrying capacity is the largest population size that an environment's resources, such as food, water, and space, can sustain indefinitely without degrading the habitat.

Question 9: Which succession type occurs on land previously stripped of soil and organisms, such as after a volcanic eruption?

•          Secondary succession

•          Primary succession

•          Cyclic succession

•          Tertiary succession

Explanation: Primary succession begins in lifeless areas where soil has not yet formed, such as bare rock after a volcanic eruption or glacial retreat, starting with pioneer species like lichens that help build initial soil.

Question 10: Biomagnification refers to the increasing concentration of a substance at higher trophic levels.

•          True

•          False

Explanation: Biomagnification occurs when persistent toxins, such as mercury or certain pesticides, become more concentrated as they move up the food chain because predators accumulate the toxin loads of many prey organisms.

Question 11: Which factor is considered density-dependent in limiting population growth?

•          Natural disasters

•          Disease transmission

•          Extreme weather

•          Volcanic eruption

Explanation: Density-dependent factors, like disease transmission, competition for resources, and predation, intensify as population density increases because closer proximity between individuals increases contact and resource pressure.

Question 12: What is the primary greenhouse gas responsible for anthropogenic climate change?

•          Oxygen

•          Carbon dioxide

•          Nitrogen

•          Argon

Explanation: Carbon dioxide, released largely through fossil fuel combustion and deforestation, is the primary greenhouse gas driving human-caused climate change because it traps outgoing infrared radiation in the atmosphere.

Question 13: Mutualism describes a relationship in which both species involved benefit.

•          True

•          False

Explanation: Mutualism is a symbiotic relationship in which both participating species gain some advantage, such as pollinators receiving nectar while plants receive pollination services in return.

Question 14: What term describes species that are the first to colonize a disturbed or newly formed habitat?

•          Climax species

•          Pioneer species

•          Keystone species

•          Indicator species

Explanation: Pioneer species, such as lichens and certain mosses, are hardy organisms capable of colonizing barren or disturbed environments first, gradually altering conditions to allow other species to establish.

Question 15: Which of the following best defines a biome?

•          A single population of organisms

•          A large geographic region with a distinct climate and characteristic plant and animal communities

•          A single ecosystem within a forest

•          The interaction between two species

Explanation: A biome is a broad regional classification of ecosystems, such as tropical rainforest, tundra, or desert, defined largely by climate patterns and the characteristic vegetation and animal life they support.

Question 16: Eutrophication is generally beneficial for maintaining aquatic biodiversity.

•          True

•          False

Explanation: Eutrophication, often caused by excess nutrient runoff, leads to algal blooms that deplete dissolved oxygen as they decompose, frequently resulting in fish kills and reduced biodiversity rather than benefiting aquatic ecosystems.

Question 17: What is the term for organisms that obtain energy by breaking down dead organic matter?

•          Producers

•          Decomposers

•          Primary consumers

•          Autotrophs

Explanation: Decomposers, including fungi and bacteria, break down dead organisms and organic waste, releasing nutrients back into the soil or water for reuse by producers, thereby completing nutrient cycles.

Question 18: Which of the following is an example of an abiotic factor in an ecosystem?

•          Predation

•          Soil pH

•          Competition

•          Symbiosis

Explanation: Abiotic factors are non-living components of an ecosystem, such as soil pH, temperature, sunlight, and water availability, that influence which organisms can survive and thrive in a given environment.

Question 19: Invasive species often thrive in new environments because they lack natural predators.

•          True

•          False

Explanation: Invasive species frequently outcompete native organisms because the predators, parasites, or diseases that normally regulate their populations in their native range are absent in the newly introduced environment.

Question 20: Which ecological pyramid typically shows energy decreasing at each successive trophic level?

•          Pyramid of numbers

•          Pyramid of biomass

•          Pyramid of energy

•          Pyramid of species

Explanation: A pyramid of energy always narrows toward the top because energy is progressively lost as heat at each trophic transfer, reflecting the second law of thermodynamics and limiting the length of food chains.