Download Speciation

Speciation
Ecology Unit
Speciation
 Formation
of a
new species
Species: A group of
similar organisms
that breed together
and produce fertile
offspring.
 Gene pools must
become separated
for them to become
different species.

http://video.pbs.org/video/1300397304/
Speciation
Phenotype

Observable
characteristics
(green eyes,
brown hair, purple
flowers, etc.)
Genotype

Genetic makeup
of an organism
determined by a
pair of alleles.
All in the Genes
 The genetic make-up
of an organism is
known as its genotype.
 An organism’s
genotype and the
environment in which
it lives determines its
total characteristic
traits.
Genotype
Phenotype
commons.wikimedia.org/wiki/Image:DNA_double_helix_vertikal.PNG
 its phenotype.
DNA
Watson and Crick and
their model of DNA
DNA
replication
 The double-helix
structure of DNA
was discovered in
1953.
 This showed how
genetic information
is transferred from
one cell to another
almost without
error.
www.chem.ucsb.edu/~kalju/chem110L/public/tutorial/images/WatsonCrick.jpg
en.wikipedia.org/wiki/DNA
Gene




Unit of hereditary
information
Located on a
chromosome
Contains DNA
Genes are passed
from parent to
offspring.
Gene Pool
 Consists
of all
the genes that
are present in
a population.
Genetic Variation

Mutations




Any change in a
sequence in DNA.
Few mutations lead to
increased fitness.
Most mutations are
harmful.
Mutations lead to
variations in a
population.
Variation
 Variationsof a
particular gene are
known as alleles.
 For example, the
one of the genes
for hair color
comprises
brown/blonde
alleles.
 Species with greater
genetic variability
are more likely to
adapt to changing
environments
majorityrights.com/index.php/weblog/comments/racial_variation_in_so
me_parts_of_the_skull_involved_in_chewing/
Natural Selection
Selection of dark gene
Mutant alleles spread
through a population by
sexual reproduction.
 If an allele exerts a harmful
effect, it will reduce the
ability of the individual to
reproduce and the allele will
probably be removed from
the population.
 In contrast, mutants with
favorable effects are
preferentially passed on
en.wikipedia.org/wiki/Image:Mutation_and_selection_diagram.svg
Natural Selection can affect the distribution
of phenotypes in any of three ways:

Stabilizing Selection


Disruptive Selection


Individuals at the middle
of the curve have the
greatest fitness.
Individuals at either end
of the curve have greater
fitness than those in the
middle.
Directional Selection

Individuals at one end of
the curve have a higher
fitness than those in the
middle or other end.
Causes of
SPECIATION

Prevention of mating between
formerly interbreeding groups.
or

The inability of these groups to
produce fertile offspring
Tigon
Result of male tiger and female lion
mating incaptivity. Offspring are
infertile.
Separated both
geographically and
ecologically.
Liger
Result of male lion and female tiger
mating in captivity. Offspring are
infertile.
CAPABLE OF
BREEDING BUT HAVE DIFFERENCES IN
COURTSHIP RITUALS (EX. MEADOWLARKS)
– SEPARATED
BY GEOGRAPHIC BARRIERS LIKE RIVERS,
MOUNTAINS, OR BODIES OF WATER (EX.
SQUIRREL)
– 2 OR MORE
SPECIES REPRODUCE AT DIFFERENT
TIMES.
Fig. 23.6
Four species of leopard frogs: differ in their
mating calls. Hybrids are inviable.
Geographic Isolation
These squirrels live on opposite sides of the Grand Canyon. This is an
example of allopatric speciation.
Temporal Isolation