Download The process of Speciation

THE PROCESS OF
SPECIATION
What is a Species?
•Species - a group of
organisms capable of
interbreeding and
producing fertile
offspring.
Speciation
•Speciation is the
formation of a new
species.
Isolating Mechanisms
• Reproductive isolation occurs when a population splits into two
groups and the two populations no longer interbreed.
• When populations become reproductively isolated, they can
evolve into two separate species.
Behavioral Isolation
• Behavioral isolation occurs when two populations that
are capable of interbreeding develop differences in
courtship rituals or other behaviors
• http://www.youtube.com/watch?v=nS1tEnfkk6M&safety_mode=true&persist_safety_mode=1&safe=active
Geographic Isolation
• Geographic isolation occurs when two populations are
separated by geographic barriers such as rivers,
mountains, or bodies of water.
Temporal Isolation
• Temporal isolation
happens when two or
more species reproduce
at different times.
What separates one specie from
another?
A) Ability to live in the same habitat
A) Ability to interbreed and produce fertile offspring
B) Ability to be fertile at different times of the year
C) Ability to mate and interbreed
What type of isolation is caused by a river cutting
through a valley and separating two groups of a
specie?
A) Behavioral
B) Geographic
C) Temporal
What type of isolation is caused by three
different flowers blooming at different
times of the year?
A) Behavioral
B) Geographic
C) Temporal
Speciation in Darwin’s Finches
• Speciation in Galápagos
finches occurred by:
• founding of a new population
• geographic isolation
• changes in the new
population’s gene pool
• behavioral isolation
• ecological competition.
Founders Arrive
• Many years ago, a few finches
from South America—species
M—arrived on one of the
Galápagos islands, as shown
in the figure.
Geographic Isolation
• Because of the Founder Effect
the traits of these birds
differed from the original
population.
• Allele frequencies – how
often different traits show
up in the population.
Changes in Gene Pool
• Over time, populations on
each island adapted to local
environments.
• Natural selection could have
caused two distinct
populations to evolve (A and
B), each characterized by a
new phenotype (observable
trait).
Behavioral Isolation
• Depending on local
environments, different birds
behaved differently further
isolating them.
Competition and Continued Evolution
• Birds that are most different from
each other have the highest fitness.
• More specialized birds have less
competition for food.
• Over time, species evolve in a way
that increases the differences
between them, and new species
may evolve (C, D, and E).
Research
• What species were similar to the species you chose last week?
• Research and try to find their most recent common ancestor.
• What could possibly have caused them to become two species.
• Write an “informed” story about one species becoming two
including:
• The habitat of the original species
• The isolation mechanism that caused the split in species
• The selective pressure each organism faced causing it to select specific
traits that differed from the other population.
• These traits must help increase the organisms fitness.