Environmental Science Basics

What is environmental science?

An interdisciplinary field using multiple fields to understand environmental systems, human-environment interactions, and sustainability.

What is ecology?

The branch of biology that studies interactions among organisms and between organisms and their environment.

What is the environment?

All living and nonliving things with which organisms interact.

What is the Anthropocene?

A proposed era in which humans have become major agents of change in Earth's life-support systems. The formal geological epoch is still generally identified as the Holocene in the course notes.

When did the Holocene begin?

About 11,700 years ago.

What is sustainability?

The capacity of Earth's natural life-support systems and human economic systems to survive or adapt indefinitely to changing conditions.

What is sustainable development?

Meeting present needs without compromising future generations' ability to meet their needs.

What are the three scientific components of sustainability?

Solar energy, biodiversity, and chemical/nutrient cycling.

What are the three pillars of sustainable development?

People, Planet, and Profits.

What are major human environmental problems?

Climate change, habitat/species loss, deforestation/land-use change, ocean acidification, rising CO₂, freshwater limitations, resource waste, and hazardous pollutants.

What are major root causes of environmental problems in the notes?

Population growth; unsustainable resource use; failure to include environmental costs in market prices; isolation from nature; and competing environmental worldviews.

What are the major human cultural revolutions in order?

Agricultural Revolution → Industrial-Medical Revolution → Information-Globalization Revolution; the notes call for a sustainability revolution.

How did the Agricultural Revolution change the environment?

It expanded human populations and transformed forests and grasslands through agriculture and land conversion.

What does I = PAT mean?

Environmental Impact = Population × Affluence × Technology. Technology may raise or lower impact depending on its use.

What is an ecological footprint?

The biologically productive land and water needed to supply a population's resources and absorb its waste, including carbon emissions.

What is biocapacity?

An area's ecosystem's ability/productivity to regenerate renewable resources and absorb certain wastes.

When is there an ecological deficit?

When the ecological footprint is greater than biocapacity.

What is a carbon footprint?

The direct and indirect greenhouse-gas emissions associated with an activity, product, person, or population.

What is natural capital?

The stock of natural resources and assets that provide benefits to humans.

What is the course formula for natural capital?

Natural Capital = Natural Resources + Ecosystem Services.

What is a renewable resource?

A resource that can regenerate on human time scales if use does not exceed regeneration; examples include trees, fish, and water in a replenished system.

What is a nonrenewable/exhaustible resource?

A finite resource that does not regenerate on human time scales; examples include oil, coal, natural gas, and copper.

What is an inexhaustible resource?

A resource treated as continually available, such as solar, wind, or geothermal energy.

What is maximum sustainable yield?

The largest amount of a renewable resource that can be harvested indefinitely without reducing its available supply.

What are ecosystem services?

Benefits humans receive from ecosystems, such as water purification, pollination, climate regulation, nutrient cycling, and UV protection provided by the ozone layer.

How can natural capital be degraded?

Through pollution, climate change, soil erosion, deforestation, habitat degradation, extinction, aquifer depletion, declining fisheries, and overuse.

How can natural capital be sustained?

Use renewable resources no faster than regeneration, reduce waste/pollution, protect habitats and biodiversity, and maintain ecosystem processes.

What is a trade-off in environmental decision-making?

A choice where advancing one goal may create costs or constraints for another.

Which decade saw many major U.S. environmental laws enacted?

The 1970s.

What did Rachel Carson's 1962 book Silent Spring help expose?

Environmental harm associated with pesticides.

What major U.S. environmental events occurred in 1970 according to the notes?

First Earth Day, establishment of the EPA, NEPA, and the Clean Air Act.

Match these laws/years: Clean Water Act; Endangered Species Act; Safe Drinking Water Act.

Clean Water Act—1972; Endangered Species Act—1973; Safe Drinking Water Act—1974.

What are RCRA and CERCLA/Superfund associated with?

RCRA—1976; CERCLA/Superfund—1980.

What is Aldo Leopold known for in the course timeline?

A Sand County Almanac (1949).

What are the Kyoto and Paris agreements associated with?

International climate agreements.

What are the basic steps of the scientific method?

Ask a question; research what is known; propose a hypothesis; test it with data; use results to evaluate/reject it and revise as needed.

What does it mean that science is iterative?

Scientists repeat and revise steps, hypotheses, and experiments as new results or questions arise.

What is a hypothesis?

A testable statement predicting a relationship between variables.

What is the working hypothesis (H₁)?

The proposed effect or relationship being tested.

What is the null hypothesis (H₀)?

The prediction that the proposed effect or relationship does not occur.

What is a p-value?

The probability of results at least as extreme as those observed if the null hypothesis were true.

In the course's convention, what do you conclude if p ≤ 0.05?

Reject the null hypothesis.

In the course's convention, what do you conclude if p > 0.05?

Do not reject/retain the null hypothesis; evidence is not sufficient to reject it.

What is a scientific theory?

A repeatedly tested explanation supported by multiple lines of evidence.

What is a scientific law?

A well-tested description of a repeated pattern in nature; it describes what happens rather than explaining how it happens.

Theory vs. law?

A theory explains; a law describes.

What is an observational study?

A study that measures/observes without manipulating a treatment; it can show patterns but usually cannot establish causation by itself.

What is an experimental study?

A study that manipulates a treatment and measures a response while controlling other conditions.

What is an experimental unit?

The individual unit on which data are collected, such as a plant, animal, bacterial plate, or plot.

What is a treatment?

The condition deliberately changed by a researcher.

What is a control group?

A baseline group that does not receive the altered treatment.

What is the response variable?

The outcome/characteristic measured to determine the treatment's effect.

What is replication?

Using multiple experimental units in treatment and control groups.

What should be held constant in a controlled experiment?

All relevant conditions other than the treatment being tested.

What is peer review?

Expert evaluation of a study's methods, evidence, and reasoning before publication.

Why is peer-reviewed research generally more reliable than popular press?

It is evaluated by experts and typically reports scientific methods and evidence, though peer review does not guarantee that a study is flawless.

Can science provide absolute certainty?

No. Science evaluates evidence and uncertainty; peer review and repeated testing help identify errors and bias.

Are opinions a scientific tool in the same way as observations, measurements, and experiments?

No. Scientific conclusions should be grounded in observations, measurements, and testable evidence.

What is matter?

Anything that has mass and occupies space; it can occur as a solid, liquid, or gas.

What is an atom?

The smallest unit of an element that retains its chemical properties.

What is an element?

A substance that cannot be chemically broken down into simpler substances.

What is a molecule?

Two or more atoms held together by chemical bonds.

What is a compound?

A substance formed when two or more different elements are chemically bonded.

What is an ion?

An atom or group of atoms with a net charge due to gaining or losing electrons.

What is an organic compound in the course notes?

A carbon-based compound; the notes describe these as generally containing at least two carbons, with methane as an exception.

What are examples of inorganic compounds important in ecosystems?

Water and many mineral/nutrient substances.

What is a physical change?

A change that does not alter chemical composition.

What is a chemical change?

A change that alters chemical composition.

What is the law of conservation of matter?

Atoms are rearranged, not created or destroyed in ordinary physical/chemical changes; decomposition does not make matter disappear.

What are carbohydrates used for?

They are an energy source and include simple sugars and complex chains of glucose.

What are proteins made from and what do they do?

Amino acids; they are major biological building materials and perform many functions.

What are fats/lipids important for?

Energy storage and other biological functions.

What is the basic structural and functional unit of life?

The cell.

What is a population?

Individuals of the same species living in a particular place.

What is a community?

Populations of different species living and interacting in a place.

What is an ecosystem?

A community interacting with its nonliving environment through matter and energy.

What is the biosphere?

The global zone of life.

Put the levels of organization in order.

Atom → molecule → cell → organism → population → community → ecosystem → biosphere.

Match levels to examples: atom, molecule, cell, organism, ecosystem.

Carbon atom; glucose molecule; plant cell; oak tree; forest ecosystem.

What are biotic factors?

Living components of an ecosystem.

What are abiotic factors?

Nonliving physical and chemical factors such as water, light, temperature, pH, soil, moisture, and nutrients.

What is an autotroph/producer?

An organism that makes its own food; phototrophs use light, while chemoautotrophs use chemical energy.

What is a heterotroph/consumer?

An organism that obtains energy and nutrients from organic material.

What is a herbivore?

A consumer that feeds on producers/plants; generally a primary consumer.

What is a carnivore?

A consumer that eats animals.

What is a decomposer?

An organism, such as fungi or bacteria, that chemically breaks down dead organic matter and returns nutrients to the environment.

What is a detritivore?

An organism that physically consumes dead material or waste, such as an earthworm or some insects.

Decomposer vs. detritivore?

Decomposers chemically break down organic material; detritivores ingest/physically break down detritus.

What is photosynthesis?

Producers use light to convert CO₂ and water into energy-rich sugars and oxygen: CO₂ + H₂O + light → glucose + O₂ (simplified equation).

What is cellular respiration?

Cells release usable energy from organic molecules; aerobic respiration uses organic nutrients and oxygen.

What is a trophic level?

An organism's feeding position relative to the energy source and other organisms.

What occupies the first through fourth trophic levels?

1st: producers; 2nd: primary consumers; 3rd: secondary consumers; 4th: tertiary consumers/top predators.

What is a food chain?

A linear pathway of feeding relationships/energy transfer.

What is a food web?

Interconnected food chains that represent multiple feeding relationships.

What does a trophic/energy pyramid show?

Usable energy, productivity, and often biomass generally decrease at higher trophic levels.

What is the approximate 10% rule?

About 10% of energy at one trophic level becomes available to the next; roughly 90% is used or dissipated, much as heat.

If producers contain 10,000 kcal, about how much is available to primary, secondary, and tertiary consumers?

About 1,000 kcal → 100 kcal → 10 kcal.

If grass has 1,000 energy units and grass → cow → human, with 10% transfer efficiency, how much reaches humans?

About 10 units: 1,000 → 100 → 10.

What is the First Law of Thermodynamics?

Energy cannot be created or destroyed, only transformed.

What is the Second Law of Thermodynamics?

Energy transformations increase entropy/energy dispersal; usable energy is degraded and some is dissipated as heat.