Evolution__3rd_Edition

Glossary
Words in italics cross-refer to a separate entry for that word
elsewhere in the glossary.
adaptation A feature of an organism enabling it to survive
and reproduce in its natural environment better than if it lacked
the feature.
adaptive topography A graph of the average fitness of a
population in relation to the frequencies of genotypes in it. Peaks
on the landscape correspond to genotypic frequencies at which
the average fitness is high, valleys correspond to genotypic frequencies
at which the average fitness is low. It is also called an
adaptive landscape, or a fitness surface.
allele A variant of a single gene, inherited at a particular
genetic locus; it is a particular sequence of nucleotides, coding for
messenger RNA.
allometry The relation between the size of an organism and
the size of any of its parts: for example, there is an allometric
relation between brain size and body size, such that (in this case)
animals with bigger bodies have bigger brains. Allometric relations
can be studied during the growth of a single organism,
between different organisms within a species, or between organisms
in different species.
allopatric speciation Speciation via geographically separated
populations.
allopatry Living in separate places. Compare sympatry.
amino acid A unit molecular building block of proteins. A protein
is a chain of amino acids in a certain sequence. There are
20 main amino acids in the proteins of living things, and the
properties of a protein are determined by its particular amino
acid sequence.
amniotes The group comprising reptiles, birds, and mammals.
They all develop through an embryo that is enclosed within
a membrane called an amnion. The amnion surrounds the
embryo with a watery substance, and is probably an adaptation
for breeding on land.
analogy A term mainly not used in this edition of the text, but
close in meaning to homoplasy. That is, a character shared by
a set of species but not present in their common ancestor a a
convergently evolved character. Some biologists distinguish
between homoplasies and analogies. In Chapter 3, the term is
used to contrast with pre-evolutionary homology. An analogy is
then a structure like a bird wing and an insect wing. It is similar
for functional reasons and not deeply similar in structure.
Compare homology.
anatomy (i) The structure itself of an organism, or one of its
parts. (ii) The science that studies those structures.
ancestral homology Homology that evolved before the common
ancestor of a set of species, and is present in other species
outside that set of species. Compare derived homology.
area cladogram A branching diagram (or phylogeny) of a set
of species (or other taxa) showing the geographic areas they
occupy. According to the theory of vicariance biogeography, the
branching diagram represents the history of range splits (probably
driven by geological processes such as continental drift) in
the ancestry of the species.
artificial selection Selective breeding, carried out by humans,
to alter a population. The forms of most domesticated and
agricultural species have been produced by artificial selection;
it is also an important experimental technique for studying
evolution.
asexual reproduction The production of offspring by virgin
birth or by vegetative reproduction; that is, reproduction without
sexual fertilization of eggs.
assortative mating Tendency of like to mate with like. It can
be for a certain genotype (e.g., individuals with genotype AA
tend to mate with other individuals of genotype AA) or phenotype
(e.g., tall individuals mate with other tall individuals).
atomistic (as applied to theory of inheritance) Inheritance in
which the entities controlling heredity are relatively distinct,
permanent, and capable of independent action. Mendelian
inheritance is an atomistic theory because, in it, inheritance is
controlled by distinct genes.
autosome Any chromosome other than a sex chromosome.
base The DNA is a chain of nucleotide units, and each unit consists
of a backbone made of a sugar and a phosphate group, with
a nitrogenous base attached. The base in a unit is one of adenine
(A), guanine (G), cytosine (C), or thymine (T). In RNA, uracil
(U) is used instead of thymine. A and G belong to the chemical
class called purines; C, T, and U are pyrimidines.
Batesian mimicry A kind of mimicry in which one nonpoisonous
species (the Batesian mimic) mimics another poisonous
species.
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