VI. Levels of Selection

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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive

• - Stalk-eyed flies, Cyrtodiopsis dalmanni and C.
  whitei (Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
  causes female-biased sex ratios
• spermatid degeneration of Y-bearing sperm in
  male carriers of X(d).
• balanced by Y-linked and autosomal factors that
  decrease the intensity of meiotic drive.
• Even a Y-linked polymorphism for resistance to
  drive which reduces the intensity and reverses
  the direction of meiotic drive.
• When paired with X(d), modifying Y chromosomes
  (Y(m)) cause the transmission of predominantly
  Y-bearing sperm, and on average, production of
  63 male progeny.

2
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements
3
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements these
genes replicate themselves independently of cell
division... they are gene parasites that make
nothing for the cell. yet they increase in
frequency relative to other genes in the genome.
4
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements 3.
'Selfish' Genes (Richard Dawkins)
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements 3.
'Selfish' Genes (Richard Dawkins) - genes are
the fundamental replicators
6
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements 3.
'Selfish' Genes (Richard Dawkins) - genes are
the fundamental replicators - genes which
confer an advantage, when averaged across other
genetic backgrounds, will be selected for.
(Analogy of 'crews')
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection 1.
Meiotic Drive 2. Transposable Elements 3.
'Selfish' Genes (Richard Dawkins) - genes are
the fundamental replicators - genes which
confer an advantage, when averaged across other
genetic backgrounds, will be selected for.
Analogy of 'crews') - co-adaptive assemblages
and non-additive effects are not explained
8
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection - some mitochondria in
yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They
reproduce fast in a cell.
10
VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection - some mitochondria in
yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They
reproduce fast in a cell. - In small populations
of yeast, where selection at the organismal level
is weak, there is no cost to the cell to
reproducing slowly and the parasitic mitochondria
dominate within cells.
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection - some mitochondria in
yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They
reproduce fast in a cell. - In small populations
of yeast, where selection at the organismal level
is weak, there is no cost to the cell to
reproducing slowly and the parasitic mitochondria
dominate within cells. - In large populations,
where aerobic respiration is advantageous at a
cellular level, cells with parasites are selected
against and the frequency of parasitic
mitochondria is reduced.
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection - some mitochondria in
yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They
reproduce fast in a cell. - In small populations
of yeast, where selection at the organismal level
is weak, there is no cost to the cell to
reproducing slowly and the parasitic mitochondria
dominate within cells. - In large populations,
where aerobic respiration is advantageous at a
cellular level, cells with parasites are selected
against and the frequency of parasitic
mitochondria is reduced. - There is a balance of
selection at different levels that must be
understood to explain the different frequency of
parasitic mitochondria.
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection -
Cancerous Tumour - cell division increases, and
the effects may be balanced at a higher level
(organism).
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection D.
Organism Selection (Darwinian)
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection D.
Organism Selection (Darwinian) E. Kin
Selection
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1. Darwins Dilemma
bees make me sad
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2. W. D. Hamilton - 1964 - related individuals
that help one another increase their OWN fitness,
because their alleles occur within THOSE
relatives.
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2. W. D. Hamilton - 1964 - related individuals
that help one another increase their OWN fitness,
because their alleles occur within THOSE
relatives. a. Inclusive Fitness
several relatives have more of YOUR genes,
cumulatively, than YOU do! ½ ½ ½ gt 1
1/2
1/2
1/2
1
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a. Inclusive Fitness
1/2
1/2
1/2
1
21
If I save myself
AAAAAAAAA !!!!!
X
X
X
X
X
I save one set of my genes
X
1/2
1/2
1
1/2
1
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If I save my relatives I save 1.5 sets of my
genes. If this has a genetic basis, selection
will favor altruism among relatives.
What a guy!
ow
1/2
1/2
1/2
1/2
1/2
1/2
1
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3. Examples 1. Helping among relatives a
function of kin selection
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3. Examples 1. Helping among relatives a
function of kin selection
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3. Examples 1. Helping among relatives a
function of kin selection
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3. Examples 2. Haplodiploidy and Social
Insects
W. D. Hamilton 1964
bees make me sad
rb gt c
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection D.
Organism Selection (Darwinian) E. Kin
Selection F. Group Selection (Wynne-Edwards)
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F. Group Selection (Wynne-Edwards) - Can groups
replace one another simply by reproductive
success??
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F. Group Selection (Wynne-Edwards) - Can groups
replace one another simply by reproductive
success?? - First, it would have to be
recognized by it's contradiction with organismal
selection.
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F. Group Selection (Wynne-Edwards) - Can groups
replace one another simply by reproductive
success?? - First, it would have to be
recognized by it's contradiction with organismal
selection. - (Sacrifice of fitness at the
organismal level with increase at the level of
the group).
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F. Group Selection (Wynne-Edwards) - Can groups
replace one another simply by reproductive
success?? - First, it would have to be
recognized by it's contradiction with organismal
selection. - (Sacrifice of fitness at the
organismal level with increase at the level of
the group). - Altruism is a possible example -
sacrifice reproduction for benefit of the
group... but it usually doesn't work because
f(altruism) declines within the pop if organisms
are unrelated!
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F. Group Selection (Wynne-Edwards) - But
there are caveats with kin selection, too

• Naked mole-rats
• Live for 31 years
• Dont get cancer division inhibited by cell-cell
  contact, and have an odd hyaluronan protein5x
  larger than humans and cancer-prone species in
  which the normal form increases rate of
  metastasis.
• MUCH lower mutation rate
• Only mammals that are thermoconformers
• Eusocial one queen, 2-3 males, the rest
  sterile workers in two size castes.
• Vertebrate of the Year in 2013

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Problem To show group selection, distinct from
individual selection, it must be shown that a net
cost to the individual is outweighed by a net
benefit to the group, without invoking
relatedness and kin selection. This is different
than an individual benefiting MORE by helping the
group than by acting selfishly. THIS is still
maximizing individual fitness. PRO GROUP
Wilson ANTI GROUP Pinker
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VI. Levels of Selection Selection can occur
wherever there is differential reproduction among
variable entities. A. Gene Selection B.
Organelle Selection C. Cell Selection D.
Organism Selection (Darwinian) E. Kin
Selection F. Group Selection (Wynne-Edwards)
G. Species Selection
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G. Species Selection
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G. Species Selection - Selection for sexually
reproducing species Parthenogenesis arises
spontaneously, but extinctions are rapid due to
lack of variation and Muller's rachet.
Muller's ratchet is the continuous
accumulation of mutations in a lineage. In
sexual reproduction, since only 1/2 of the genes
are passed from each parent, there is a 50
chance that a deleterious new mutation will be
purged from the genome just by chance. And also,
even if it is expressed, there will be other
organisms in the pop that did NOT receive it and
have higher fitness. So, selection can purify
this sexual population of the deleterious
alleles. But in an asexual lineage, all offspring
get the whole genome - even a new deleterious
allele. So, there is no way to purge it from the
genome. In fact, in Daphnia pulex, asexual
lineages accumulate deleterious amino acid
substitutions at 4x the rate of sexual lineages
(Paland and Lynch 2006, Science 311990-992).
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G. Species Selection - Selection for sexually
reproducing species - Parthenogenesis arises
spontaneously, but extinctions are rapid due to
lack of variation and Muller's rachet. So,
extinction rates in parthenogenetic lineages are
high... and so most lineages that radiate and
produce lots of descendant species are sexual.
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G. Species Selection - Selection for sexually
reproducing species - Certain lineage are more
likely to speciate (beetles - small, tough, and
easily isolated...)
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G. Species Selection - Selection for sexually
reproducing species - Certain lineage are more
likely to speciate (beetles - small, tough, and
easily isolated...) SO, as a consequence of
survival and speciation rate (reproduction),
sexual lineages and also more rapidly speciating
lineages will leave more species and replace
other lineages that die out over time.