A structure or way of behaving that help an organism
to survive in a particular environment. Adaptive =
A form of divergent evolution – generally associated
with a relatively rapid divergence into new species or
groups and associated with unoccupied ecological
The proportion of each allele of a particular gene in
the gene pool.
Allopoloploidy Where an individual has more than two chromosome
sets that have arisen from combining two different
genomes (species) Form infertile hybrids.
Amphiploidy The doubling of sterile hybrid chromosome sets in
plants to create a fertile plant.
Pattern of speciation that occurs when organisms or
populations are living in separate geographical
areas (ie have become geographically isolated.)
Organs that are similar in function and often in
superficial structure but of very different evolutionary
Autopolyploidy Where an individual has more than two chromosome
sets, that have arisen from non-disjunction within the
Cline Pattern of variation within a species. A continuous
increase or decrease in some characteristics
between adjacent populations as you move eg North
Co evolution The genetic change (and evolution) in a species, in
response to genetic change in another. Each organism
exerts selective pressures on the other and over time the
species become mutually dependent.
The evolution of similar adaptive features in species
from different origins because they have adapted to
the same environment.
Deme A local unit of population of any one species. They
usually have some genetic or other character that
sets them apart from other nearby populations.
Natural selection that favours the phenotype of one
extreme over the average or over the other extreme
so there is a shift of the average.
Natural selection that favours both extremes at the
expense of the average.
Evolution where organisms become more diverse as
they evolve from a common ancestor.
Founder Effect Where only a few organisms move into a new area
and may carry only a few of the available alleles from
the species gene pool.
Gene flow The movement of genes from one part of a
population to another, or from one population to
another, via gametes.
Gene pool The total of genes in a population at any one time.
When the allele frequencies of a gene pool remain
unchanged from generation to generation.
Genetic drift Random changes in gene pools(rather than
directional ones brought about by natural selection)
Can be highly significant in altering allele frequency
in small gene pools.
Genotype The genetic makeup of an organism – what alleles it
The proportion of each genotype in the gene pool.
When physical barriers separate one species
population from another.
Gradualism A theory that states species evolve steadily and
gradually change into different forms.
Organs that have descended by inheritance from a
common ancestor, but may have different functions.
When an organism is genetically isolated from its
original species in one generation by polyploidy.
A variety of barriers eg geographical, ecological,
temporal, that may ultimately lead to genetic isolation
Macroevolution Large scale changes in groups of species or genera
as viewed in the fossil record. Evolution above the
level of genera.
Microevolution The generation to generation changes in the
frequency of alleles or genotypes in a population.
Mutation A change in a gene that leads to a new allele. Rare
and random, but is the ultimate source of variation
Process whereby some combinations of alleles are
more likely to help survival and reproduction than
others. These are selected in specific environments,
and their frequency will increase in the gene pool.
How species avoid direct competition with other
species by eg exploiting slightly different food
An example of a homologous organ in vertebrates.
Phenotype The physical expression of the genotype in an
Phylogeny The evolutionary history of a species or taxonomic
Polyploidy Having more than two sets of chromosomes. May
bring about the abrupt formation of a new species.
Population A group of individuals of the same species in an
Where a population is reduced to a few survivors
whose gene pool is not necessarily representative of
the original gene pool.
Postzygotic After fertilization. Refers to isolating factors that
prevent successful reproduction after fertilization.
Prezygotic Before fertilization. Refers to isolation factors that
prevent successful reproduction before fertilization.
A theory that states that species remain stable for
long periods of time and then undergo relatively rapid
speciation and change.
When a species or group can no longer breed
successfully with any other organism but the
members of its own species or group.
Ring species Where two apparently different species in one area
are joined by a series of geographical and structural
intermediates. Adjacent groups are still able to
interbreed but not the extremes.
When a species accumulates genetic change over
time which result in a different species (replacing the
original rather than branching out from it)
The shuffling of genes by independent assortment of
chromosomes and random joining of gametes at
Species A group of actually or potentially interbreeding
natural populations that is reproductively isolated
from other such groups.
Natural selection that favours the average phenotype
at the expense of the extremes.
Speciation that occurs in species that remain living in
the same area and are never geographically isolated,
but become genetically isolated.
Vestigal organs Organs that have been important in some ancestral
form but that have become redundant in later