Download Speciation and Phylogenetic Trees

Speciation and
Phylogenetic Trees
Mrs. Dignan’s Biology Class
Darwin’s 4 Points
1. Organisms can produce more offspring
than they can support.
2. Any environment has a finite supply of
resources.
3. Individuals have natural variation in their
traits, due to mutations and genetic
recombination.
4. Those individuals most suited to their
environment tend to survive and pass on
their traits.
Macroevolution vs. Microevolution

Microevolution= “small
change”= changes within
a species

Macroevolution= “large
change”= changes that
produce new species

What is a species?
A
group of organisms that can reproduce and
produce viable, fertile offspring



Where do new species come
from?
All new species
come from existing
species
Speciation – when 1
species becomes 2
Speciation happens
in 3 steps:



Isolation between 2
populations
Random Mutation
Natural Selection of
the traits that are
best suited to the
new environment
Step 1: Isolation
In order the evolve into 2 separate
species, there must be no breeding
between 2 populations.
 Isolation can happen in 5 basic ways:

 Geographic
 Behavioral
 Mechanical
 Ecological
 Post-zygotic
A) Geographic Isolation
A physical geographic
barrier (mountains,
continents, bodies
of water, etc.)
separates
populations and
prevents gene flow.
Example- Cichlids in African rift lakes
B) Behavioral Isolation
The two populations do
not mate with each
other because they
exhibit different
mating behaviors.
C) Mechanical Isolation
Two populations
are separated
because their
bodies do not
“fit” together
right,
preventing
gene flow.
D) Ecological Isolation
The populations
become isolated
from one another
because they have
different functions
and habitats
within the
ecosystem.
E) Post-zygotic Isolation
Even if 2 individuals do
mate, they may be too
genetically different to
produce viable offspring.
 The egg may not be
fertilized
 The zygote may die
 The resulting
offspring may be
sterile
Speciation – 1 species becomes 2
The process of making
new species happens
in 3 steps:
 Isolation
 Mutation
 Natural Selection
Phylogenetic Trees

Phylogenetic trees:
tools that biologists
use to show
evolutionary
relationships between
species.
Phylogenetic Trees