Animal Social Behavior

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Animal Social Behavior
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Animal Social Behavior

• Costs, Disadvantages

• Benefits, Advantages

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Animal Social Behavior

• Costs, Disadvantages
• competition
• diseases, parasites
• degradation of environment
• increased conspicuousness

• Benefits, Advantages
• competition
• efficiency of foraging, predation
• avoidance of predation
• opportunity to modify environment
• interaction with genetic relatives
• recall that family is one of the levels of
  biological organization

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Animal Social BehaviorIs family important?
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Animal Social BehaviorHow is genetic relatedness
determined?
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
diplodiploidy
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible gametes C1 C2 C3 C4
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
What proportion of genes do parents share with
their offspring?
possible offspring C1C3 C2C3 C1C4 C2C4
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4
C2C4 gender doesnt matter
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4
C2C4 what about siblings?
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
C1C3 C2C3 C1C4 C2C4 0.5
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
C1C3 C2C3 C1C4 C2C4 0.5 1.0

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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
C1C3 C2C3 C1C4 C2C4 0.5 1.0
0.0
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
C1C3 C2C3 C1C4 C2C4 0.5 1.0
0.0 0.5
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Animal Social BehaviorHow is genetic relatedness
determined?
female parent C1C2
male parent C3C4
possible offspring C1C3 C2C3 C1C4 C2C4
Take any particular offspring C2C3
What proportion of genes are shared with its
siblings?
C1C3 C2C3 C1C4 C2C4 0.5 1.0
0.0 0.5
What is the average proportion of genes shared by
common descent by siblings?
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Animal Social BehaviorHow is genetic relatedness
determined?
The average proportion of genes shared by common
descent between any two individuals is the
coefficient of genetic relatedness and is
symbolized r
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Animal Social BehaviorHow is genetic relatedness
determined?
The average proportion of genes shared by common
descent between any two individuals is the
coefficient of genetic relatedness and is
symbolized r In diplodiploid species parents
- offspring, r 0.5 siblings, r
0.5 grandparents and grandchildren, r 0.25
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Animal Social BehaviorHow is genetic relatedness
determined?
The average proportion of genes shared by common
descent between any two individuals is the
coefficient of genetic relatedness and is
symbolized r In diplodiploid species parents
- offspring, r 0.5 siblings, r
0.5 grandparents and grandchildren, r
0.25 Aunts/uncles and nieces/nephews? Cousins?
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Animal Social BehaviorHow is genetic relatedness
determined?
siblings
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren
0.5
0.5
Aunts/uncles with nieces/nephews, r 0.25 (0.5 x
0.5) first cousins, r 0.125 (0.5 x 0.5 x 0.5)
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
Descendant kin those in direct lines of
descent (parents, offspring, grandparents,
grandoffspring) Collateral kin relatives but
not descendants or ancestors (siblings,
aunts/uncles, nieces/nephews, cousins)
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
How much did my fitness increase when Ella was
born?
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
How much did my fitness increase when Ella was
born? This is direct fitness (r 0.25)
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
How much did my fitness increase when Ella was
born? This is direct fitness (r 0.25) How
much did Jeffs fitness increase when Ella was
born?
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
How much did my fitness increase when Ella was
born? This is direct fitness (r 0.25) How
much did Jeffs fitness increase when Ella was
born? This is indirect fitness (r 0.25)
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
How much did my fitness increase when Ella was
born? This is direct fitness (r 0.25) How
much did Jeffs fitness increase when Ella was
born? This is indirect fitness (r 0.25) How
much did Charles fitness increase when Ella was
born? This is also indirect fitness (r 0.125)
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Animal Social BehaviorHow is genetic relatedness
determined?
0.5
Becky -- Steve Charles -- Deborah Chris
Jeff Rachel Lauren Lorna Elanor
0.5
0.5
0.5
The combination of direct fitness and indirect
fitness for any particular individual is that
individuals inclusive fitness
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Animal Social BehaviorHow is genetic relatedness
determined?
The combination of direct fitness and indirect
fitness for any particular individual is that
individuals inclusive fitness Selection that
acts on individuals so that they behave in ways
that increase their inclusive fitness is called
indirect selection
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Animal Social BehaviorHow is genetic relatedness
determined?
The combination of direct fitness and indirect
fitness for any particular individual is that
individuals inclusive fitness Selection that
acts on individuals so that they behave in ways
that increase their inclusive fitness is called
indirect selection Darwin got it right when he
wrote that selection may be applied to the
family as well as to the individual
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Animal Social BehaviorHow is genetic relatedness
determined?

• Heritable variation (among families, in behaviors
  that promote inclusive fitness)
• combined with differential RS (among families)
• leads to the spread of characteristics (that
  increase inclusive fitness) through populations
• adaptive behaviors may evolve due to the action
  of indirect selection

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Animal Social BehaviorHow is genetic relatedness
determined?

• What kinds of behaviors might evolve through the
  action of indirect selection?
• What kinds of behaviors increase the inclusive
  fitness of an individual and thus the overall
  fitness of the family?
• Behaviors that appear to benefit the fitness of
  recipient individuals at a cost to the fitness
  of the donor individual
• are called altruism
• Most behaviors that appear to be altruistic are
  thought to have evolved through the action of
  indirect selection

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Animal Social BehaviorHow is genetic relatedness
determined?

• What is the alternative to altruism?
• Selfishness is behavior that promote an
  individuals RS, without worrying about the
  effect of that behavior on the RS of other
  individuals
• Is selfishness or altruism more likely to evolve?

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Animal Social Behavior
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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Animal Social BehaviorWhat is the effect of
indirect selection?
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This is why we need a special explanation for
altruistic behavior - Darwin recognized this need
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Animal Social BehaviorWhat is the effect of
indirect selection?
Under what conditions (ecological, genetic) is
altruism most likely to evolve?