Other Concepts of Species
1. Ecological Species Concept
2. Pluralistic Species Concept
3. Morphological Species Concept
4. Genealogical Species Concept
3.Morphological Species Concept: the oldest and
still most practical, defines a species by a unique
set of structural features.
4.Genealogical Species Concept: defines a
species as a set of organisms with a unique
genetic history—one tip of the branching tree of
life.
Speciation: Plants
• Polyploids may cause new species because the
change in chromosome number creates
postzygotic barriers.
• Polyploid Types:
1. Autopolyploid - when a species doubles its
chromosome number from 2N to 4N.
2. Allopolyploid - formed as a polyploid hybrid
between two species.
– Ex: wheat
1.Ecological Species Concept: defines a
species in terms of its ecological niche,
the set of environmental resources that
a species uses and its role in a
biological community
2.Pluralistic Species Concept: concept
may invoke reproductive isolation or
adaptation to an ecological niche, or
use both in maintaining distinctive,
cohesive groups of individuals
Speciation Event: Adaptive
Radiation
• Resources are temporarily infinite.
• Most offspring survive.
• New species form rapidly if isolation
mechanisms work.
• Result - little Natural Selection and the
gene pool can become very diverse.
Autopolyploid
Allopolyploid
Origin of Evolutionary Novelty
• How do macroevolution changes originate?
– Exaptation
– Heterochrony
– Homeosis
Exaptation
• When a structure that was adapted for
one context is co-opted for another
function.
• Ex. – feathers and flying- adaptation for
insulation and a exaptation for flight
Eample: Trap-jaw
ants, manibles
were adaptation
for manipulation
of objects,
adaptation for
defense
Heterochrony
• Changes in the timing or rate of
development.
1. Allometric Growth
2. Paedomorphosis
What is the
difference between
this and
ADAPTATION?
Heterochrony: Allometric Growth
1. Allometric Growth – changes in the
relative rates of growth of various parts of
the body.
• Ex. – skull growth in primates
Heterochrony: Paedomorphosis
2. Paedomorphosis – when an adult retains
features that are present in the juvenile
form.
Ex. – gills in adult salamanders
Homeosis
Changes in the basic body design or
arrangement of body parts.
Ex. – Hox gene clusters that gave rise to
vertebrates from invertebrates.
Refuting Misconceptions
• Evolution is not goal oriented. It does not
produce “perfect” species.
Refuting Misconceptions
• Evolution does not mean that life evolved
by “chance.”
•Evolution is not an explanation
for the origin of life. Only an
explanation of how life
functions after its origin.
•Natural Selection does
not involve organisms
“trying to adapt.”
Refuting Misconceptions
• Natural Selection
does not give
organisms what they
“need”
•Evolution as a “THEORY”