Biology II Key Terms: Chapter 1 – Introduction to Life on Earth
1. adaptation – a trait that increases the ability of an individual to survive and
reproduce compared to individuals without the trait
2. biodiversity – the total number of species within an ecosystem and the resulting
complexity of interactions among them
3. biosphere – the part of Earth inhabited by living organisms; includes both living
and nonliving components
4. community – all the interacting populations within an ecosystem
5. conclusion – the final operation in the scientific method; a decision made about
the validity of a hypothesis on the basis of experimental evidence
6. control – 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
7. deductive reasoning – the process of generating hypotheses about how a specific
experiment or observation will turn out
8. ecosystem – all the organisms and their nonliving environment within a defined
area
9. evolution – 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
10.experiment – the third operation in the scientific method; the testing of a
hypothesis by further observations, leading to a conclusion
11.homeostasis – the maintenance of a relatively constant environment required for
the optimal functioning of cells
12.hypothesis – 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
13.inductive reasoning – the process of creating a generalization based on many
specific observations that support the generalization, coupled with an absence of
observations that contradict it
14.metabolism – the sum of all chemical reactions that occur within a single cell or
within all the cells of a multicellular organism
15.mutation – a change in the base sequence of DNA in a gene; normally refers to a
genetic change significant enough to alter the appearance or function of the
organism
16.natural causality – the scientific principle that natural events occur as a result of
preceding natural causes
17.natural selection – the unequal survival and reproduction of organisms due to
environmental forces, resulting in the preservation of favorable adaptations
18.observation – the first operation in the scientific method; the noting of a specific
phenomenon, leading to the formulation of a hypothesis.
19.population – all the members of a particular species within an ecosystem, found in
the same time and place and actually or potentially interbreeding
20.scientific method – a rigorous procedure for making observations of specific
phenomena and searching for the order underlying those phenomena; consists of
four operations: observation, hypothesis, experiment, and conclusion
21.scientific theory – a general explanation of natural phenomena developed through
extensive and reproducible observations; more general and reliable than a
hypothesis
22.species – the basic unit of taxonomic classification, consisting of a population or
series of populations of closely related and similar organisms
23.variable – a condition, particularly in a scientific experiment, that is subject to
change