Transcript SPECIATION

SPECIATION/MACROEVOLUTION
The Creation of species
Hi, Donald Duck here.
I was just telling my uncle, Professor Ludwig von Drake from
Vienna Austria that I had to give a talk about evolution to a
bunch of teenagers. When he noticed how much trouble I was
having preparing for the talk, he volunteered to give the talk
instead. Hope you can understand him, he’s got an accent, but
he’s also really smart. Bye, I’m off for a date with Daisy.
Hello, I am
Professor
Ludwig von
Drake, und I
um here to
describe zee
speciation
concept.
I must warn
you that we will
be discussing
the key
process in
macroevolution
called
SPECIATION.
Hopefully you
have an
understanding
of the evolution
concept.
Now in my first discussion of species I
show you zee mating and reproduction of
zee species. Your job is to match zee
correct mates together. If correct, you
vill have identified zee species und you
vill get new little vuns.
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Good, you have correctly
classified zee species using
how zey look =
MORPHOLOGY
MORPHOLOGICAL SPECIES CONCEPT
Classify species mainly on visible anatomical
characters to define species.
Morpho mean shape, form, appearance Logo mean word. So appearance
word.
Organisms are classified in the same species if
they appear identical by morphological
(anatomical) criteria. Thus it is a population or
group of populations that differs
morphologically from other populations. For
example, we can distinguish between a chicken
and a goose because they have different
shaped bills and the duck has webbed feet.
Carl Linnaeus vas
svedish ya!
He was also know as Carl
von Linne. The von
denoted after he was
ennobled, in 1761 and he
shortened the Linnaeus
to Linne.
You now know zee method used by Carl Linnaeus to
classify species. He developed a zystem of taxonomy
to classify every living thing . Zis vas done vay back
in 1735 It was based on MORPHOLOGY. Now shall ve
continue vith my little game?
Vait a minute. Zay all look different. Zee difference is
between zee sexes called Sexual Dimorphism. We now
have to rely of whether zey reproduce!
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No Offspring
DIFFERENCE ---SEXUAL DIMORPHISM
Notice from the previous slide, there where inappropriate mates
chosen. In nature this would not happen.
MATE RECOGNITION SPECIES CONCEPT
A group of organisms that are known to
recognize one another as potential mates.
Like the isolation species concept above, it
applies only to organisms that reproduce
sexually.
Now we have arrived at the final definition for zee species.
A species must reproduce und produce offspring
Vait, Vait, Vhat are you doing. Those don’ t go
together! Zey are different -----species?
Yes zey are different species because the mules cannot
reproduce. Now on to my final, final definition of species
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Female
Horse
=
Male
donkey
+
Male
mule
= NO OFFSPRING
Female
mule
BIOLOGICAL SPECIES CONCEPT
Two populations that can and do interbreed in
nature and produce fully fertile offspring.
In the population, there is an absence of gene flow
between members of different species. It, however, is
insufficient for asexually reproducing organisms.
Also, it does not distinguish between the theoretical
possibility of interbreeding and the actual likelihood.
It also does not apply to species that hybridize to
produce polyploid individuals.
Even in World War II, 14,000 mules were used as
they were able to travel through thick jungle and
rugged mountains that were impossible for vehicles,
and even horses, to cross.
Some say they are stubborn, but this
is due to their intelligence and
knowledge of self preservation.
My new final definition of species is ...What the heck are
you doing now? Stop doing zat, zey are different --species?
Lets see, zey can reproduce, produce offspring who are
fertile.....But zis is not happening in zee wild! It is not
natural. It is zee result of human intervention!
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Female tiger
Male lion
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Male liger
=
Female liger
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Male tiger
Male liger
Liger cubs
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Female lion
Tigon cub
Female liger
Did you know that Ligers are the
world’s largest cats?
It's pretty much my
favorite animal. It's like a
lion and a tiger mixed...
bred for its skills in magic
Now vut has just happened? You are mating tigers and
lions and lions and tigers and ligers and liger and tigons and
tigons. I am going crazy!
Is a tiger a lion? Is a lion a tiger? Zey look different.
You mean Charles
Darwin?
Ya, ya, ya, Charles
Darvin.
Darwin says –species variations
Are tigers and lions the same species? They must be,
zey produce fertile offspring. But I know zey are not
the same species. I need to talk to that Darvin Guy!
How about Haldane?
Who is zis Haldane fella?
J.B.S. Haldane was a genetics and population genetics pioneer from 1892-1964
Vhat did he do? He developed Haldane’s Rule. According to Haldane, males are the
heterogametic sex, in that they have XY sex chromosomes, whereas
females are homogametic, with XX chromosomes
When in the F1 offspring of two different animal races one sex is absent, rare,
or sterile, that sex is the heterozygous [heterogametic] sex.
Ex. From genetics, more males are colour blind or hemophiliacs –thus heterogametic -still rare
As species differentiation further progresses, parental genetic differentiations generate
anatomical, physiological or psychological differences that result in mating
incompatibilities. The "postzygotic barriers" (hybrid sterility and hybrid inviability), are
replaced by "prezygotic barriers" (e.g. mating incompatibilities).
"I look at the term species, as one
arbitrarily given for the sake of
convenience to a set of individuals
closely resembling each other ... It
does not essentially differ from the
word variety, which is given to less
distinct and more fluctuating forms.
The term variety, again, in
comparison with mere individual
differences, is also applied
arbitrarily, and for convenience
sake."
Post = after
Zygotic = first cell
barrier
After zygote fertilization, offspring are
produced, but are sterile.
Pre=before
Vait a minute, enough of zis
hocus pokus mumbo jumbo! I
am giving a talk to high school
students, not brain surgeons.
Vhat does all zis mean?
Zygotic= first cell
barrier
Barrier to prevent fertilization in the first
place—even though offspring can be produced
STEP 1 Postzygotic
barrier = sterile offspring
like the mule
They mate to produce offspring but the offspring are infertile.
STEP 2 Prezygotic barrier = lack of contact
in the wild (ex live in different areas)
A prezygotic isolating mechanism would prevent fertilization of the egg.
Prezygotic Barriers
The species are separated by:
ECOLOGICAL SEPARATION – Different locations or niches
TEMPORAL SEPARATION- Different breeding season
BEHAVIOURAL SEPARATION – specific mating rituals
required
MECHANICAL SEPARATION – size of reproductive
organs incompatibilities
MORPHOLOGICAL SEPARATION – body size and shape
incompatibilities
GAMETIC SEPARATION – sperm incompatible to egg
Boy, am I glad I don’t have to take your
exam. Oh, excuse me, where was I now.
Oh yes, I need my final, final, final
definition of a species.
A species can be defined as all members of
groups or populations zat interbreed or have the
ability to interbreed vith each other under
natural conditions. Zeir offspring must also be
fertile. Zee liger is not a species because,
notice, it says NATURAL conditions, und lions and
tigers are kept separate by ECOLOGICAL barriers
as mentioned in zee previous slide.
CAUTION – IMPORTANT POINT
The mule cannot mate with either the
horse or the donkey. There is no gene
flow, and this is a new more accurate
way of defining a species. In addition
the liger cannot mate with either the
lion nor the tiger, so it is the same
effectively as the mule example.
This hybrid has REDUCED HYBRID FERTILITY . They cannot produce
offspring when then mate with either parental species- genes cannot flow.
CAUTION – IMPORTANT POINT
REDUCED HYBRID VIABILITY
The genes of different parent species may interact to
produce offspring. The hybridization, however, impairs
the offspring’s development. Hybrids do not complete
development or are weak or frail. (postzygotic barrier)
HYBRID BREAKDOWN
The first generation hybrids are viable and fertile, but
when they mate with each other or either parent
species, offspring of the next generation are feeble or
sterile. (postzygotic barrier)
See you in part two.
SPECIATION PART 1
END