Download Lecture #11 Date

Fri. 2/21
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Collect: Ch. 18 guided reading
Today: Quiz Ch 18, Notes Ch 17.
Homework: Ch 17 Guided Reading
Next class: Quiz Ch 17
Test corrections must be done by Wed.
2/26.
Late work will only be accepted up to the
day we take the test over that chapter.
Pg. 132
• Guided Reading-Ch
17
Pg. 133
• EK paragraph Ch 17
1C1 or 1C2
In: Pg 134
Watch the Bozeman video ―Speciation and
Extinction‖ and write 5 facts.
Extinctions
• Extinctions are always occurring at a low
rate (background rate)
• Occasionally, mass extinction events will
happen when many more species will go
extinct than normally
• Example:
– Permian (250 million years ago):
• 90% of marine animals; Pangaea merge
• ***Human Impact on Ecosystems &
Species Extinction Rates***
Mass extinction
• Cretaceous
(65 million years
ago): death of
dinosaurs, 50% of
marine species; low
angle comet
(maybe?)
Pg 135
Chapter 17Speciation and
Macroevolution
Macroevolution: the origin of new taxonomic
groups
• Speciation: the origin
of new species.
• As opposed to
microevolution…alelle
frequency changes in
a population—no new
species.
Yellow Pine Chipmunk
Tamius amoenus
Least Chipmunk
Tamius minimus
Chinese Crested
Canis familiaris
Newfoundland dog
Canis familiaris
What is a species?
Biological species
concept (Mayr): a population
or group of populations whose
members have the potential to
interbreed and produce viable,
fertile offspring (genetic
exchange is possible and that is
genetically isolated from other
populations)
• Limitations
– Asexual organisms
– Fossils
– Don’t know all organisms that
can breed with one another.
Alternative ways of classifying
species
• Morphological- body shape and structures
– Problems: different members of the same
species can look different and members of
different species can look the same.
• Evolutionary- use fossil record to decide
speciation
– Problems: still based on morphology and
incomplete fossil record
• Phylogenetic- based on evolutionary
relationships, a species is a breeding
population that have a common ancestor
and share a common trait.
• Problems: may
be gene flow between species,
very small genetic differences
may divide species.
Reproductive Isolation (isolation of gene pools)
1. Prezygotic barriers: impede mating
between species or hinder the
fertilization of the ova
• Habitat (snakes; water/terrestrial)
• Behavioral (fireflies; mate
signaling)
• Temporal (salmon; seasonal
mating)
• Mechanical (flowers; pollination
anatomy)
• Gametic (frogs; egg coat
receptors)
2. Postzygotic barriers:
fertilization occurs, but the
hybrid zygote does not develop
into a viable, fertile adult
• Reduced hybrid viability
(frogs; zygotes fail to
develop or reach sexual
maturity)
• Reduced hybrid fertility
(mule; horse x donkey;
cannot backbreed)
• Hybrid breakdown (cotton;
2nd generation hybrids are
sterile)
Modes of speciation (based on how gene flow
is interrupted)
• Allopatric: populations
segregated by a
geographical barrier; can
result in adaptive radiation
(island species)
• Sympatric: reproductively
isolated subpopulation in the
midst of its parent population
(change in genome or habitat
separation).
– Polyploidy-when 2 parents with
different # of chromosomes
mate but produce infertile
offspring-common in plants.
EXPERIMENT
Researchers from the University of Leiden placed males and females of Pundamilia pundamilia and
P. nyererei together in two aquarium tanks, one with natural light and one with a monochromatic orange
lamp. Under normal light, the two species are noticeably different in coloration; under monochromatic orange
light, the two species appear identical in color. The researchers then observed the mating choices of the fish
in each tank.
Normal light
Monochromatic
orange light
P. pundamilia
P. nyererei
RESULTS
CONCLUSION
Figure 24.10
Under normal light, females of each species mated only with males of their own species. But
under orange light, females of each species mated indiscriminately with males of both species.
The resulting hybrids were viable and fertile.
The researchers concluded that mate choice by females based on coloration is the main
reproductive barrier that normally keeps the gene pools of these two species separate. Since
the species can still interbreed when this prezygotic behavioral barrier is breached in the
laboratory, the genetic divergence between the species is likely to be small. This suggests
that speciation in nature has occurred relatively recently.
Adaptive Radiation
• Evolution of many
diverse species
from a common
ancestor.
• New
environments/new
―branches‖
• Cambrian Explosion
 600 mya, origin
of most animal
phyla
Convergent
Evolution
• Similar traits evolve in
2 unrelated species
due to similar
environments.
• Cichlids in African Rift
Lakes.
Coevolution
– Species evolve together because of some
relationship
• Predator/Prey or Parasite/Host:
– ―Evolutionary arms race‖
• Symbiotic relationships
– Flowers (Plants ) and pollinators (insects, bats, birds)
Tempo of speciation
• Gradualismchanges are slow
and steady over
time(Darwin).
• Punctuated
equilibrium-changes
occur in bursts
– Helps to explain
gaps in the fossil
record.
Out
Read ―Ghost Stories from the Ice Age‖ and answer the
questions.
1. What was the fate of the large herbivores?
2. What are the 2 ways plants were reliant on the large
herbivores?
3. Of which type of evolution is this an example?
4. Discuss how each of the following was dispersed in the
past and is dispersed today:
a. Devil’s claw
b. Osage orange
c. Gourd-bearing vines