Genus: group of species that share similar traits.
Goldilocks Principle: "Venus is too hot, Mercury is too cold, and Earth is just right" for life to exist.
Greenhouse Gases: Water vapor, carbon dioxide, methane, and nitrous oxide in the atmosphere that trap infrared radiation.
Greenhouse Effect: Heating of Earth's surface by certain atmospheric gases, which helps keep Earth's surface warm enough to sustain life.
Half-life: The time it takes for half of a given quantity of a radioactive isotope to decay into another isotope.
Hypothesis: a guess based on facts.
Mutualism: Relationship in which both organisms benefit.
Observations: Information about the environment or a particular phenomenon.
Parasitism: Relationship in which one organism suffers and another one benefits from it.
Perihelion: the point in Earth's orbit where it is closest to the Sun (in January).
Prediction: Guess of what might happen in a situation based on a hypothesis.
Taxonomy: the scientific field that identifies, names and classifies organisms.
Sink population: a population in which mortality exceeds reproductive success.
Source Population: a population in which reproductive success exceeds mortality.
Species: Specific kind of organism that can with one another.