Chapter 1 An Introduction to Life on Earth
a trait that increases the ability of an individual to survive and reproduce
compared to individuals without the trait.
self-feeder; normally, a photosynthetic organism; a producer.
the total number of species within an ecosystem and the resulting
complexity of interactions among them.
that part of Earth inhabited by living organisms; includes both living and
the smallest unit of life, consisting, at a minimum, of an outer membrane that
encloses a watery medium containing organic molecules, including genetic material
composed of DNA.
the final operation in the scientific method; a decision made about the
validity of a hypothesis on the basis of experimental evidence.
that portion of an experiment in which all possible variables are held constant;
in contrast to the experimental portion, in which a particular variable is altered.
referring to cells of organisms of the domain Eukarya (plants, animals,
fungi, and protists). Eukaryotic cells have genetic material enclosed within a membrane-
bound nucleus and contain other membrane-bound organelles.
the descent of modern organisms with modification from preexisting life-
forms; strictly speaking, any change in the proportions of different genotypes in a
population from one generation to the next.
the third operation in the scientific method; the testing of a hypothesis by
further observations, leading to a conclusion.
literally, other-feeder; an organism that eats other organisms; a consumer.
the maintenance of a relatively constant environment required for the
optimal functioning of cells, maintained by the coordinated activity of numerous
regulatory mechanisms, including the respiratory, endocrine, circulatory, and excretory
the second operation in the scientific method; a supposition based on
previous observations that is offered as an explanation for the observed phenomenon and
is used as the basis for further observations, or experiments.
the sum of all chemical reactions that occur within a single cell or within
all the cells of a multicellular organism.
many-celled; most members of the kingdoms Fungi, Plantae, and
Animalia are multicellular, with intimate cooperation among cells.
the unequal survival and reproduction of organisms due to
environmental forces, resulting in the preservation of favorable adaptations. Usually,
natural selection refers specifically to differential survival and reproduction on the basis
of genetic differences among individuals.