Discrete trait
Inherited trait
that exhibits
distinct phenotypes
Quantitative traits
A trait that exhibits
continuous phenotypic variation
Asexual reproduction
Reproduction
where offspring inherit DNA from only
one parent
E.g. binary fission, budding and parthenogenesis
Sexual reproduction
Any form of reproduction in which
genes
from
two parents
are combined via
fusion of gametes
, producing offspring that are
genetically distinct
from both parents
Genetic variation
Number and relative
frequency
of
alleles
present in a particular population
Proportion of
phenotypic variation
in a trait due to
genetic
influences in a certain population in a certain environment
Directional selection
Natural selection
that favors one
extreme phenotype
Average phenotype of a population
changes
in
one direction
Reduces
overall
genetic variation
Purifying selection
Selection
that
lowers
the
frequency
or even eliminates
deleterious alleles
Stabilizing selection
Natural selection
that favors
phenotypes
near the
middle
of the
range
of
phenotypic variation
Reduces
overall
genetic variation
in a population
Disruptive selection
Natural selection
that favors
extreme phenotypes
at
both ends
of the variation range
Genetic variation
is
maintained
Balancing selection
Natural selection
where
no single allele
is favored in all populations of a species at all times
Balance
among alleles'
fitness
and
frequency
Heterozygote advantage
Pattern of
natural selection
that favors
heterozygous
individuals compared with homozygotes
Maintains
genetic variation
in a population; a form of
balancing selection
Frequency-dependent selection
Pattern of selection in which certain
alleles
are
favored
only when they are
rare
A form of
balancing selection
Acclimatization
A change in an individual's
phenotype
in response to a change in
natural environmental
conditions
Genetic correlation
Evolutionary constraint in which
selection
on
one
trait causes a
change
in
another
trait as well
May occur when the same gene(s) affects both traits
Sampling error
Selection of a
non-representative
sample from some larger population, due to
chance
Genetic marker
Genetic locus
that can be
identified
and
traced
in populations by lab techniques or a distinctive visible phenotype
Founder effect
Change in
allele frequencies
that often occurs when a
new population
is established from a
small group
of individuals due to
sampling error
Mutation
Any
change
in the
hereditary material
of an organism
Only source of
new alleles
Point mutation
A
mutation
that results in a change in a
single base pair
of
DNA
Lateral gene transfer (horizontal gene transfer)
Transfer of
DNA
between two
different species
Beneficial allele
Allele that
increases
an individual's
fitness
Gene flow
Movement
of
alleles
between
populations
Occurs when individuals leave one population, join another, and breed
Inbreeding
Mating between
closely related
individuals
Increases homozygosity
in a population and often leads to a
decline
in
fitness
via selection
Deleterious allele
Allele that
reduces
an individual's
fitness
Inbreeding depression
In
inbred
offspring,
fitness declines
due to
deleterious recessive alleles
that are
homozygous
, thus exposed to
selection
Sexual selection
Natural selection
that favors individuals with traits that
increase
their ability to
obtain mates
Acts more strongly on
males
than females
Biological species concept
Species as a population(s) that are
reproductively isolated
from other groups
Members have potential to
interbreed
to produce viable, fertile offspring
Cannot
interbreed successfully with members of
other species
Prezygotic isolation
Reproductive
isolation
resulting from mechanisms that
prevent
individuals of two different species from
mating
Postzygotic isolation
Reproductive
isolation
resulting from mechanisms that operate
after mating
of individuals of two different species occur
Morphospecies concept
Definition of a
species
as a population(s) that have a measurably
different anatomical features
from other groups
Polymorphic species
A species that has
two or more
distinct
phenotypes
in the same interbreeding population at the same time
Cryptic species
Species that
cannot
be
distinguished
from similar species by easily identifiable
morphological traits
Phylogenetic species concept
Definition of a species as the
smallest monophyletic group
in a
phylogenetic tree
Monophyletic group (clade/lineage)
Evolutionary unit
that includes an
ancestral
population and all its
descendants
but no others
Subspecies
Population that has
distinctive traits
and some
genetic differences
relative to other populations of the same species but is not distinct enough to be classified as a separate species
Phylogeny
Evolutionary history
of a group of organisms
Phylogenetic tree
Branching diagram that depicts the
evolutionary
relationships among
species
or other
taxa
Tree of life
Phylogenetic tree
that includes all organisms
Branch
Part of a
phylogenetic tree
Represents
populations
through
time
Node
The point where
two branches diverge
, representing the point in time where an
ancestral
group split into two or more
descendant
groups
Tip
End of a
branch
in a
phylogenetic tree
Represents a specific
species
or
larger taxon
that has
not produced descendants
Either a group living
today
or an
extinct
group
Character
Any
genetic
,
morphological
,
physiological
or
behavioral
characteristic of an organism to be studied
Outgroup
A
taxon
that is closely
related
to a particular
monophyletic
group but is not part of it
Ancestral trait
A trait found in the
ancestors
of a particular group
Derived trait
Trait that is clearly
homologous
with a trait found in an
ancestor
of a particular group, but that has a new form
Cladistic approach
Method of constructing a
phylogenetic tree
based on identifying
unique traits
of each
monophyletic group
Synapomorphy
A
shared
,
derived
trait found in
two or more taxa
Present
in their
most recent common ancestor
Missing
in more
distant ancestors
Parsimony
In comparing alternative
phylogenetic trees
, the one requiring the
fewest evolutionary changes
is the most likely to be correct
Homology
Similarity
among organisms of
different species
due to inheritance from a
common ancestor
Homoplasy
Similarity
among organisms of
different species
due to reasons
other than common ancestry
, e.g. convergent evolution
Convergent evolution
Independent
evolution
of
similar traits
in
distantly related
organisms due to adaptation to
similar environments
and
way or life
Fossil
Any physical trace of an organism that existed in the past
Paleontologists
Scientists who study the
fossil record
and the
history of life
Paleozoic era
542M to 251M years ago
Fungi
,
land plants
and
animals
first appeared and
diversified
Began with
Cambrian explosion
Ended with
extinction
of many invertebrates and vertebrates
Mesozoic era
From 251M to 65.5M years ago
Gymnosperms
were dominant
plants
Dinosaurs
were dominant
vertebrates
Ended with
extinction
of
dinosaurs
Cenozoic era
Most recent interval of geologic time
Began 65.5M years ago
Mammals
were dominant
vertebrates
Angiosperms
were dominant
plants
Allopatry
Condition in which two or more populations live in
different geographic areas
Allopatric speciation
Speciation
that occurs when populations of the same species become geographically
isolated
Vicariance
Physical
splitting
of a population into smaller,
isolated
populations by a geographic barrier
Biogeography
Study of how
species
and
populations
are distributed
geographically
Sister species
Closely related
species that occupy
adjacent branches
in a
phylogenetic tree
Sympatric speciation
Divergence
of populations living within the
same geographic area
into
different species
as a result of their
genetic isolation
Polyploidy
State of having
more than two full sets of chromosomes
, either from same species or from different species
Autopolyploidy
Having
more than two
full sets of chromosomes due to a
mutation
that doubled the chromosome number
All chromosomes come from the
same species
Allopolyploidy
Having
more than two
full sets of chromosomes due to
hybridization
between
different species