Lesson 4 Flashcards
speciation
the splitting of one species into two distinct species
species
A group of organisms that can reproduce
and create offspring that can also
reproduce.
Organisms are defined by their
distinct physical characteristics
known as
diagnostic traits
Cryptic species
two different
species that look identical but differ
in some other way (courtship, etc.)
Morphology
study of an organism’s form and
the relationship between their structures
Evolutionary Species Concept
Relies on the identification
of certain morphological
traits to distinguish one
species from another
Track evolution as specific
characteristics change over
time
Phylogenetic Species Concept
A phylogeny (family tree) is used to
identify species based on a common
ancestor
Based on DNA code, not morphology
A branch that contains all the
descendants of a common ancestor
is said to be
monophyletic
Biological Species Concept
Relies on reproductive
isolation to identify species
This can be location, behavior,
anatomical, etc.
Difficult to test in nature
No overlap geographically, but are they
reproductively isolated?
Can’t be applied to asexually reproducing
organisms or fossils
Definition of a Species
For two species to remain separate,
populations must be
reproductively
isolated
Gene flow must not occur between
them
isolating
mechanisms
barriers that prevent successful
reproduction
Allopatric Speciation
geographical barrier
Sympatric Speciation
no geographical barrier
Gradualism
Slowly over time
Punctuated Equilibrium:
Periods of rapid change
Divergent evolution (Adaptive Radiation)
forms from a common ancestor
Convergent evolution
no common ancestor but results in similar traits
Occurs when a biological trait
evolves in two unrelated species
as a result of exposure to similar
environments.
Analogous traits:
similar traits due to
similar lifestyle of habitat
Homologous traits:
similar traits due
to a common ancestor
HOX genes
Specify regions of the
body plan of an embryo
* Create head/tail axis in
animals
* Ensure that the correct
structures occur in the
correct places
Type of homeobox gene
