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TOPIC 10.3 – GENE POOL & SPECIATION
2Recall that a species is a
group of organisms that has
the potential to produce fertile
offspring.
Populations are made of a
multiple members of the same
species in the same area
(reproducing).
------------
*Sometimes members of
different species can breed,
however their offspring are
sterile (i.e. mule)
http://dbou9h1pp5ks6.cloudfront.net/wp-content/uploads/2015/12/08183701/Baby-Macaque.jpg
INTRO
IB BIO – 10.3
IB BIO – 10.3
Understandings
U1: A gene pool consists of all the genes and their different alleles present in an interbreeding population.
Key Terms
Gene Pool
3
https://www.pathwayz.org/Node/Image/url/aHR0cHM6Ly9pLmltZ3VyLmNvbS9pSmRZQXQwLnBuZz8x
The gene pool of a interbreeding population is the whole of all the
genes and their alleles. Members that reproduce contribute to the
pool of the next generation.
4Having a diverse gene pool is important for a species survival.
Since the environment is always changing, which traits result in the
highest fitness can vary over time. Lack of diversity = vulnerability.
http://www.pnas.org/content/105/17/6350/F3.large.jpg
IB BIO – 10.3
Understandings
U1: A gene pool consists of all the genes and their different alleles present in an interbreeding population.
Key Terms
Gene Pool
IB BIO – 10.3
Understandings
U2: Evolution requires that allele frequencies change with time in populations.
Key Terms
5
http://jeb.biologists.org/content/204/18/3151
In order for evolution to occur in a population, the frequency of
alleles must change over time. Recall that evolution is the
cumulative change of a populations heritable characteristics .
IB BIO – 10.3
Skills
S1: Comparison of allele frequencies of geographically isolated populations.
Key Terms
6Online databases can be used to compare allele frequencies in
populations that are geographically separated. For example, you
can use the Allele Frequency Database hosted by Yale.
https://gcbias.files.wordpress.com/2013/09/onesnp.png
IB BIO – 10.3
Applications
A1: Identifying examples of directional, stabilizing and disruptive selection.
Key Terms
7Alleles that increase fitness are
more likely to be passed on to
subsequent generations.
Environmental factors act
selectively on phenotypes, which
results in natural selection.
There are three patterns of
selection:
• Directional
• Stabilizing
• Disruption
https://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Selection.svg
IB BIO – 10.3
Applications
A1: Identifying examples of directional, stabilizing and disruptive selection.
Key Terms
Stabilizing Selection
8
https://i1.wp.com/gregladen.com/wordpress/wp-content/graphics/StabilizingSelection.jpg
Stabilizing Selection
Environmental factors apply
pressure, which removes
extremities of certain traits.
For example,
• High/low birth weight
Promotes health of
offspring and mother
• Number of eggs
Promotes survival of
offspring
IB BIO – 10.3
Applications
A1: Identifying examples of directional, stabilizing and disruptive selection.
Key Terms
Directional Selection
9
https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Directional_Selection_%28Left%29.svg/2000px-Directional_Selection_%28Left%29.svg.png
Directional Selection
For example,
• Color (e.g. peppered moths)
• Beak Type (e.g. finches)
Environmental factors apply pressure, which causes the population
to move towards an extreme.
• Organism size (e.g. horses)
IB BIO – 10.3
Applications
A1: Identifying examples of directional, stabilizing and disruptive selection.
Key Terms
Stabilizing Selection
10
https://i1.wp.com/gregladen.com/wordpress/wp-content/graphics/StabilizingSelection.jpg
Disruptive Selection
Environmental factors apply
pressure, which removes
intermediates of a trait.
This is typically seen in
high-density populations
For example,
• Pea pod color
• Rabbit fur color
11The process of speciation results in a wide diversity of life forms
on Earth. This speciation is often the result of various
forms of isolation.
https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2012/colour-morphs-3-columns-3.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
12Isolation is an important part of natural selection and evolution. In
reproductive isolation, barriers prevent species from producing fertile
offspring. This prevents gene flow between populations
http://embed.wistia.com/deliveries/d89443027b2bf88c1065ea96a9cbbc2173cf30cf.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
13Prezygotic barriers are those
that prevent either members from
mating or that prevent
fertifilization from occurring.
Types of prezygotic barriers
include:
• Geographical
• Temporal
• Behavioral
http://geology.com/articles/east-africa-rift/figure2.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
14Geographic isolation occurs when populations of a species are
separated by a geographic barrier. This can include mountains,
bodies of water, rifts, etc.
While separated the
populations can
evolve separately.
http://www.fullfrontalanatomy.com/Bio3/Standard_docs/Resources/Campbell/Chapter_14/B_Jpeg_Images/14_Labeled_Images/14_08GeographicIsolation-L.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Geographic Isolation
15Geographic isolation was the
reason Darwin observed such
diversity amongst the Galagagos
Islands.
Since species on different islands
were unable to mate, over time
they evolved differently
https://calendar.google.com/calendar/render#main_7%7Cweek
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Geographic Isolation
16Similar variations can be seen on
land as well.
For example, this map shows the
variety of Ensatina species that
emerged California as a result of
being geographically separated.
http://media.springernature.com/full/springer-static/image/art%3A10.1186%2F1471-2148-11-194/MediaObjects/12862_2011_1803_Fig1_HTML.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Geographic Isolation
17Temporal isolation occurs when the reproductive systems species
mature at different times. Although one group is able to reproduce,
the other is not physically prepared. These crickets are an example:
https://s3.amazonaws.com/user-media.venngage.com/801250-72cd70b952d51b60f92c80155e26dc7b.jpeg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Temporal Isolation
18The American toad (left) mates in the early summer while the
Fowler toad (right) mates in late summer. As a result, the two toads
are temporally isolated and do not reproduce.
https://wildlifepreservation.ca/2016/wp-content/uploads/2015/06/Fowler-American.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Temporal Isolation
19Plants can also experience temporal isolation. For example, if two
species bloom at different times then they will not be able to fertilize
each other. This chart shows some blooming times:
http://en.hitachikaihin.jp/wp-content/uploads/2014/01/flower-calendar2.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Temporal Isolation
20Behavioral isolation occurs between populations when groups have
incompatible mating practices. This can include songs, mating
rituals and even a change in pheromones.
http://www.lolwot.com/wp-content/uploads/2016/03/10-surprising-bird-mating-rituals-youve-never-heard-of-3.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Behavioral Isolation
21For example, male fireflies
attract females of the same
species by flashing their light in a
specific pattern.
Females only respond to patterns
of their own species, which
prevents them from mating with
other species.
https://s-media-cache-ak0.pinimg.com/originals/48/a1/be/48a1bee58fbfa7ce1240c50f5a7bec4a.jpg
IB BIO – 10.3
Understandings
U3: Reproductive isolation of populations can be temporal, behavioral or geographic.
Key Terms
Reproductive Isolation
Behavioral Isolation
22Speciation is the formation of
new species that occurs during
the course of evolution.
It is the result of changes in
isolated populations and is the
source of biological diversity on
Earth.
There are two main types:
• Allopatric
• Sympatric
https://upload.wikimedia.org/wikipedia/commons/c/cd/Animal_diversity_October_2007.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Speciation
23Allopatric speciation is the most common form of speciation. It
occurs when populations are geographically isolated. As a result,
genes no longer flow between the populations.
http://ksuweb.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecEvolution/24_Labeled_Images/24_14HybrZoneOverTime_4-L.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Speciation
24Over time, the genetic makeup
of the populations can differ as a
result of natural selection their
respective environments.
Selection and genetic drift can
act differently on the groups
eventually resulting in new
species.
Although once related, the new
species are unable to reproduce
with each other.
http://ksuweb.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecEvolution/24_Labeled_Images/24_14HybrZoneOverTime_4-L.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Speciation
25Sympatric speciation occurs
when populations of species in a
habitat become reproductively
isolated.
Unlike allopatric, in sympatric
speciation the populations still
inhabit the same area.
This most often is the result of
polyploidy.
http://ksuweb.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecEvolution/24_Labeled_Images/24_14HybrZoneOverTime_4-L.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Speciation
26Sympatric speciation is rare, but occurs more often in plants as
they are able to easily self-fertilize. Polyploidy animals must find a
mate with similar ‘ploidy’ which is difficult.
http://www.motherofahubbard.com/wp-content/uploads/2013/06/floweranatomy.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Speciation
27Polyploidy occurs when offspring are produced with an abnormal
number of chromosomes. This is the result of errors occurring in
meiosis.
These individuals are not able to mate with normal diploid members
since the chromosome count doesn’t much. As a result they are
reproductively isolated.
https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Haploid%2C_diploid_%2Ctriploid_and_tetraploid.svg
IB BIO – 10.3
Applications
A2: Speciation in the genus Allium by polyploidy.
Key Terms
Polyploidy
IB BIO – 10.3
Applications
A2: Speciation in the genus Allium by polyploidy.
Key Terms
Polyploidy
28
https://2.bp.blogspot.com/-XzMdctMW7nc/VwgUB8G3fLI/AAAAAAAAIGI/xfiQvXdPBwkn6XPAwyrnDVrclCSzxpa7w/s1600/Allium%2Bekimianum.jpg
For example, polyploidy
is a common event in the
Allium genus, which
includes onions, leeks,
garlic and chives.
This results in many
similary but reproductively
isolated populations.
Many species reproduce
asexually, so polyploidy
may provide some sort of
advantage.
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
29The rate of speciation can vary, especially when the availability of
new habitats allows adaptive radiation to occur.
https://www.nature.com/article-assets/npg/nature/journal/v485/n7400/images/nature11050-f1.2.jpg
IB BIO – 10.3
Understandings
U4: Speciation due to divergence of isolated populations can be gradual.
Key Terms
Gradualism
30In the theory of gradualism,
species descended from a common
and gradually change over time.
Small changes accumulate over
time, which results in the
formation of new species.
However, transition fossils are
rarely found, making it difficult to
support this rate of change.
https://mrkubuske.files.wordpress.com/2014/03/puncgrad.jpg
31In punctuated equilirium, new species change the most when they
diverge from the parent species. After that, few changes in the
species are observed
https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/Punctuated-equilibrium.svg/1200px-Punctuated-equilibrium.svg.png
IB BIO – 10.3
Understandings
U5: Speciation can occur abruptly.
Key Terms
Punctuated Equilibrium
32This model of speciation is
supported by sudden changes
observed in the fossil record.
The record typically consists of
species that suddenly appear and
then remain unchanged until
their extinction
https://www.pathwayz.org/Node/Image/url/aHR0cHM6Ly9pLmltZ3VyLmNvbS9pcDBYc1hiLnBuZw==
IB BIO – 10.3
Understandings
U5: Speciation can occur abruptly.
Key Terms
Punctuated Equilibrium
IB BIO – 10.3
REVIE
W331. Define gene pool.
2. Define directional, disruptive and stabilizing
selection.
3. Outline behavior, temporal and geographical
isolation, providing an example of each.
4. Define speciation.
5. Outline polyploidy and its role in speciation.
6. Differentiate between gradualism and punctuated
equilibrium.
• Speciation: An Illustrated Introductionhttps://www.youtube.com/watch?v=8yvEDqrc3XE
• CrashCourse – Speciation: Of Ligers & Menhttps://www.youtube.com/watch?v=2oKlKmrbLoU
• CrashCourse – Natural Selectionhttps://youtu.be/aTftyFboC_M?t=464
• Gradualism vs Punctuated Equilibriumhttps://www.youtube.com/watch?v=qSjiFxIHknk
• Trilobites and Punctuated Equilibriahttps://www.youtube.com/watch?v=9uqpcKWuhrU
34IB BIO – 10.3
VID
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