This document provides an overview of Chapter 9 from an introductory biology textbook on evolution and behavior. It covers several key topics: - Behaviors are traits that can evolve through natural selection, just like physical traits. Behaviors exist on a spectrum from innate to learned. - Apparent altruism can be explained by kin selection and reciprocal altruism. Kin selection describes helping genetic relatives to increase indirect fitness. Reciprocal altruism involves helping non-relatives with the expectation of future repayment. - Males and females often invest differently in reproduction. For species where fertilization is internal, males cannot be certain of paternity. This leads to behavioral differences like males competing for access to

1. Evolution andEvolution and
BehaviorBehavior
BIOLBIOL 108108
Intro to BioIntro to Bio SciSci
Chapter 9Chapter 9
RobRob SwatskiSwatski
Assoc Prof BiologyAssoc Prof Biology
HACCHACC--YorkYork1

2. Learning GoalsLearning GoalsLearning GoalsLearning Goals
Behaviors are
traits that can
evolve.
Cooperation,
selfishness, and
altruism can be
better
understood
with an
evolutionary
approach.
Sexual conflict
can result from
disparities in
reproductive
investment by
males and
females
Communication
and the design
of signals
evolve
2

3. 9.1–9.4
Behaviors are
traits that can
evolve.

4. 9.1 Behavior has adaptive value, just like9.1 Behavior has adaptive value, just like
other traits.other traits.
What is the
problem with
“mudcakes”
from an
evolutionary
perspective?

5. Animals should maximize energyAnimals should maximize energy
consumed and minimize energy used.consumed and minimize energy used.
5

6. Humans like to eat foods high in fat andHumans like to eat foods high in fat and
sugar.sugar.
6

7. 7

8. Why do species have tasteWhy do species have taste
preferences?preferences?
Why do species have tasteWhy do species have taste
preferences?preferences?
Feeding
choices
directly
influence
fitness.
Living and
reproducing
require
energy.
Maximal
extraction
of energy
and
acquisition
of essential
nutrients.
Natural
selection
can shape
feeding
behavior.
8

9. 9
Behavior encompasses any
and all of the actions
performed by an organism,
often in response to its
environment or to the
actions of another
organism.

10. Scope of Animal BehaviorScope of Animal Behavior
 Conflict, aggression, and territoriality
 Cooperation, alliance building, and sociality
 Competing for food and avoiding predation
 Migration and navigation
 Behavioral control of body temperature
 Courtship and mate choice
 Pair bonding and fidelity
 Breeding and parental behavior

11. Behaviors can be influencedBehaviors can be influenced
by natural selection.by natural selection.
Feeding
behavior
Humans;
starlings; shore
crabs
Maternal
care
Mice
Singing
behavior
Songbirds
11

12. Effects of evolutionEffects of evolution
by natural selectionby natural selection
are all around.are all around.
Peacock feathers
Cryptic
coloration
Behavior is part
of an organism’s
phenotype
12

13. Take-Home Message 9.1
Behavior is any and all
actions performed by an
organism.
Behavior is any and all
actions performed by an
organism.
When a heritable trait
increases an individual’s
reproductive success relative
to that of other individuals,
that trait tends to increase in
frequency in the population.
When a heritable trait
increases an individual’s
reproductive success relative
to that of other individuals,
that trait tends to increase in
frequency in the population.
Behavior is as much a part of
an organism’s phenotype as
is an anatomical structure,
and as such it can be
produced and shaped by
natural selection.
Behavior is as much a part of
an organism’s phenotype as
is an anatomical structure,
and as such it can be
produced and shaped by
natural selection.
13

14. 9.2 Some behaviors are innate.9.2 Some behaviors are innate.
14

15.  The degree to which a
behavior depends
upon the environment
varies a great deal.
 Instincts or innate
behaviors
 Fixed action pattern
Role of the EnvironmentRole of the Environment
15

16.  Triggered under
certain conditions
 Requires no learning
 Does not vary
 Once started, runs to
completion
Fixed Action PatternFixed Action Pattern
16

17. Take-Home Message 9.2
The degree to which a
behavior depends on the
environment varies a great
deal.
The degree to which a
behavior depends on the
environment varies a great
deal.
At one extreme are instincts,
innate behaviors present in
all individuals in a population
that do not vary much one
individual to another or over
an individual’s life span.
At one extreme are instincts,
innate behaviors present in
all individuals in a population
that do not vary much one
individual to another or over
an individual’s life span.
Innate behaviors don’t
require environmental input
to develop.
Innate behaviors don’t
require environmental input
to develop.
17

18. 9.3 Some behaviors must be9.3 Some behaviors must be
learned (and some are learnedlearned (and some are learned
more easily than others).more easily than others).
18

19. LearningLearning
 Involves behaviors that are altered and
modified over time in response to past
experiences
 Tremendous variation among behaviors that
require learning
• Some are easy to learn
• Others are not
19

20. Production of BehaviorsProduction of Behaviors
and the Role of the Environmentand the Role of the Environment
 Primates—fear of snakes
 Appears not innate, but learned
20

21. 21

22. Prepared LearningPrepared Learning
Behaviors that are learned easily and by all (or
nearly all) individuals
 Snake-fearing behavior of monkeys
 Acquisition of language in humans
22

23. 23

24. Why is it so much easier for an
infant to learn a complex language
than for a college student to learn
biology?
What is the evolutionary basis for the
acquisition of certain behaviors?
24

25. Take-Home Message 9.3
In contrast to innate
behaviors are behaviors that
are influenced more by the
environment.
In contrast to innate
behaviors are behaviors that
are influenced more by the
environment.
These behaviors require
some learning and are often
altered and modified over
time in response to past
experiences.
These behaviors require
some learning and are often
altered and modified over
time in response to past
experiences.
Organisms are well-
prepared to learn behaviors
that have been important to
the reproductive success of
their ancestors.
Organisms are well-
prepared to learn behaviors
that have been important to
the reproductive success of
their ancestors.
Organisms are less prepared
to learn behaviors irrelevant
to their evolutionary
success.
Organisms are less prepared
to learn behaviors irrelevant
to their evolutionary
success.
25

26. 9.4 Complex9.4 Complex--appearing behaviorsappearing behaviors
don’t require complex thought indon’t require complex thought in
order to evolve.order to evolve.
26

27. “I must maximize my
reproductive success!”
 Why do animals have sex?
 Why do people have sex?
27

28. Animals don’t consciously try to
maximize their reproductive success,
yet they behave as if they do?
How does this happen?
28

29. How do we
know?
Tricking
animals
29

30. Take-Home Message 9.4
If an animal’s behavior in
natural situations usually
increases its relative
reproductive success, the
behavior will be favored by
natural selection.
If an animal’s behavior in
natural situations usually
increases its relative
reproductive success, the
behavior will be favored by
natural selection.
The natural selection of
behaviors does not require
an organism to consciously
try to maximize its
reproductive success.
The natural selection of
behaviors does not require
an organism to consciously
try to maximize its
reproductive success.
30

31. 9.5–9.9
Cooperation,
selfishness, and
altruism can be
better understood
with an evolutionary
approach.

32. 9.5 A general theory of “kindness”
helps explain the evolution of apparent
acts of altruism.
 Does unconditional love exist in the animal
kingdom?
 Altruistic behaviors—behaviors that come at a
cost to the individual doing the behavior while
benefiting the recipient.
32

33. 33

34. Apparent Acts of AltruismApparent Acts of Altruism
 Kindness toward close relatives: kin selection
 Kindness toward unrelated individuals:
reciprocal altruism
34

35. Take-Home Message 9.5
Many behaviors in the
animal world appear
altruistic.
Many behaviors in the
animal world appear
altruistic.
In almost all cases, these
are not really acts of
altruism and have evolved
as a consequence of either
kin selection or reciprocal
altruism.
In almost all cases, these
are not really acts of
altruism and have evolved
as a consequence of either
kin selection or reciprocal
altruism.
These behaviors are
beneficial to the individual
engaging in the behavior.
These behaviors are
beneficial to the individual
engaging in the behavior.
35

36. 9.6 Apparent altruism toward9.6 Apparent altruism toward
relatives can evolve through kinrelatives can evolve through kin
selection.selection.
36

37. 37

38. Hamilton’s RuleHamilton’s Rule
 Altruistic-appearing behavior will occur when
the benefits to close relatives are greater than
the cost to the individual performing the
behavior.
 They are really acting in their own genes’ best
interests.
38

39. 39

40. Who are people most likely toWho are people most likely to
bequeath money to upon theirbequeath money to upon their
death?death?
40

41. 41

42. Redefining an Individual’s FitnessRedefining an Individual’s Fitness
 Direct fitness
• An individual’s total reproductive output
 Indirect fitness
• The reproductive output brought about by altruistic
behaviors toward close kin
 Inclusive fitness
• The sum of an individual’s indirect and direct fitness
42

43. Conflicts
 Because different individuals do not share all
of the same alleles, we should always expect
some conflict.
 Example: gestational diabetes
43

44. Take-Home Message 9.6
Kin selection describes apparently
altruistic behavior in which an
individual that assists a genetic
relative compensates for its own
decrease in direct fitness by helping
increase the relative’s fitness and,
consequently, its own inclusive
fitness.
Kin selection describes apparently
altruistic behavior in which an
individual that assists a genetic
relative compensates for its own
decrease in direct fitness by helping
increase the relative’s fitness and,
consequently, its own inclusive
fitness.
44

45. 9.7 Apparent altruism toward9.7 Apparent altruism toward
unrelated individuals can evolveunrelated individuals can evolve
through reciprocal altruism.through reciprocal altruism.
45

46. 46

47. Vampire BatsVampire Bats
 In many cases, individuals give blood to
unrelated individuals.
 How might this behavior have arisen?
47

48. Are they repaid the favor?
Reciprocal Altruism
Storing goodwill
48

49. 49

50. Certain Conditions Must Be MetCertain Conditions Must Be Met
1) Repeated interactions among individuals
2) The benefits to the recipient must be
significantly greater than the costs to the
donor.
3) The ability to recognize and punish cheaters
50

51. Why are humans among theWhy are humans among the
few speciesfew species to haveto have
friendships?friendships?
51

52. Why is it easier to rememberWhy is it easier to remember
gossip than physics equations?gossip than physics equations?
52

53. Take-Home Message 9.7
In reciprocal altruism, an
individual engages in an
altruistic-appearing act
toward another
individual.
In reciprocal altruism, an
individual engages in an
altruistic-appearing act
toward another
individual.
The actor only gives up
something of value when
likely to get something of
value later.
The actor only gives up
something of value when
likely to get something of
value later.
Reciprocal altruism occurs
only if: 1) individuals have
repeated interactions & 2)
individuals can recognize
and punish cheaters
Reciprocal altruism occurs
only if: 1) individuals have
repeated interactions & 2)
individuals can recognize
and punish cheaters
These conditions are
satisfied in humans but in
few other species.
These conditions are
satisfied in humans but in
few other species.
53

54. 9.8 In an “alien” environment,9.8 In an “alien” environment,
behaviors produced by naturalbehaviors produced by natural
selection may no longer beselection may no longer be
adaptive.adaptive.
54

55. Behaviors favored by natural selection
over evolutionary time can cause
individuals to behave in a way that
reduces their fitness.
 Belding’s ground squirrels
 Craving high-fat foods
 Donations to refugees
55

56. 56

57. Take-Home Message 9.8
When organisms are in
environments that differ from
the environment to which they
are adapted, the behaviors
they exhibit are not necessarily
evolutionarily adaptive.
When organisms are in
environments that differ from
the environment to which they
are adapted, the behaviors
they exhibit are not necessarily
evolutionarily adaptive.
57

58. 9.9 Selfish genes win out over9.9 Selfish genes win out over
group selection.group selection.
Does evolution ever lead to behaviors that are for
the good of the species or population, while
being detrimental to the individual?
58

59. 59

60. Take-Home Message 9.9
Behaviors that are good for
the species or population
but detrimental to the
individual are not generally
produced in a population
under natural conditions.
Behaviors that are good for
the species or population
but detrimental to the
individual are not generally
produced in a population
under natural conditions.
60

61. 9.10–9.15
Sexual conflict
can result from
disparities
in reproductive
investment by
males and
females.

62. 9.10 There are big differences in how9.10 There are big differences in how
much males and females invest inmuch males and females invest in
reproduction.reproduction.
62

63. Definition of “Male” and “Female”Definition of “Male” and “Female”
 A female produces the larger gamete.
 A male produces the smaller gamete.
 The mother’s material contribution to the
offspring exceeds the father’s.
63

64. Evolution of Differences inEvolution of Differences in
Male/Female BehaviorsMale/Female Behaviors
1) Extent of energetic differences in the
reproductive investment.
64

65. Why do males
usually compete
for females
rather than the
opposite?
65

66. Differences in ReproductiveDifferences in Reproductive
InvestmentsInvestments
 Fertilization within the female (internal
gestation)
 Lactation in female mammals
66

67. 67

68. Offsets and ReversalsOffsets and Reversals
in Reproductive Investmentin Reproductive Investment
Examples:
 Birds
• Gestation external
• No lactation
68

69. Examples:
 Fish and amphibians
• External fertilization
Offsets and ReversalsOffsets and Reversals
in Reproductive Investmentin Reproductive Investment
69

70. Evolution of Differences inEvolution of Differences in
Male/Female BehaviorsMale/Female Behaviors
1) Extent of energetic differences in the
reproductive investment
2) Paternity uncertainty
• also has profound influence on reproductive behavior
70

71. Take-Home Message 9.10
In mammals and many
other types of animals,
there are important
differences between males
and females relating to
reproduction.
In mammals and many
other types of animals,
there are important
differences between males
and females relating to
reproduction.
Fertilization usually takes
place in the female.
Fertilization usually takes
place in the female.
Lactation occurs only in the
female.
Lactation occurs only in the
female.
In species where
fertilization occurs inside
the female, males cannot be
certain that offspring are
their progeny.
In species where
fertilization occurs inside
the female, males cannot be
certain that offspring are
their progeny.
These physical differences
have led to the evolution of
differences in male and
female reproductive
behavior.
These physical differences
have led to the evolution of
differences in male and
female reproductive
behavior.
71

72. 9.11 Males and females are9.11 Males and females are
vulnerable at different stages ofvulnerable at different stages of
the reproductive exchange.the reproductive exchange.
72

73. Predictions About SexPredictions About Sex--Related BehaviorRelated Behavior
1) The sex that invests more will be more
discriminating.
2) The sex that invests less will compete
amongst themselves for access to the higher-
investing sex.
73

74. 74

75. Potential Exploitation at Different
Stages of the Reproductive Process
 At the point of mating
 At the point of parental care to offspring
75

76. Take-Home Message 9.11
Differing patterns of
investment in reproduction
make males and females
vulnerable to exploitation
at different stages.
Differing patterns of
investment in reproduction
make males and females
vulnerable to exploitation
at different stages.
This has contributed to the
evolution of differences in
sexual behavior.
This has contributed to the
evolution of differences in
sexual behavior.
The sex with the greater
investment is more
discriminating about
mates.
The sex with the greater
investment is more
discriminating about
mates.
The sex with less
investment competes for
access to the higher-
investing sex.
The sex with less
investment competes for
access to the higher-
investing sex.
76

77. 9.12 Tactics for getting a mate:9.12 Tactics for getting a mate:
competition and courtshipcompetition and courtship
77

78. 78

79. 79

80. 80

81. 81

82. Take-Home Message 9.12
Males tend to increase their
reproductive success by
mating with many females
and have evolved to
compete for the opportunity
to mate.
Males tend to increase their
reproductive success by
mating with many females
and have evolved to
compete for the opportunity
to mate.
Females increase their
reproductive success not
through extra matings but
rather by being choosy
about selecting a mate and
by caring for their offspring.
Females increase their
reproductive success not
through extra matings but
rather by being choosy
about selecting a mate and
by caring for their offspring.
82

83. 9.13 Tactics for keeping a mate:9.13 Tactics for keeping a mate:
mate guarding can protect a male’smate guarding can protect a male’s
reproductive investmentreproductive investment
 When offspring survival can be enhanced with
greater parental investment…
 there is an incentive for males to provide some
parental care…
 …even though such behavior makes him
vulnerable to paternity uncertainty.
83

84. Why do so few females guard their
mates as aggressively as males do?
 Mate guarding in order to reduce vulnerability
 Attempt to reduce paternity uncertainty
 “Danger zone” for males
84

85. Mate Guarding:Mate Guarding:
From Simple to MacabreFrom Simple to Macabre
85

86. CopulatoryCopulatory PlugsPlugs
 Reptiles, insects, and many mammalian
species
 Males block the passage of sperm into the
female
 Coagulated sperm and mucus
86

87. 87

88. Take-Home Message 9.13
Mate guarding can, in general,
increase reproductive success
by reducing additional mating
opportunities for a partner…
Mate guarding can, in general,
increase reproductive success
by reducing additional mating
opportunities for a partner…
…and can improve a male’s
reproductive success by
increasing his paternity
certainty and thus reducing his
vulnerability when he makes
investment in offspring.
…and can improve a male’s
reproductive success by
increasing his paternity
certainty and thus reducing his
vulnerability when he makes
investment in offspring.
88

89. 9.14 Monogamy versus polygamy:9.14 Monogamy versus polygamy:
mating patterns can vary acrossmating patterns can vary across
human and animal cultures.human and animal cultures.
89

90. 90

91. Mating SystemsMating Systems
 Polygamy
• When some individuals attract multiple mates
while other individuals attract none
 Monogamy
• Most individuals mate and remain with just one
other individual
91

92. Mating SystemsMating Systems
Polygamy subdivided into:
 Polygyny
• individual males mate with multiple females
 Polyandry
• individual females mate with multiple males
92

93. Mating Systems Are Not Easy to DefineMating Systems Are Not Easy to Define
Three issues complicate the task:
1) Differences between animals’ mating
behavior and bonding behavior
Pair bond—appears monogamous
93

94. Three issues complicate the task:
2) Mating system variation within the
species
94
Mating Systems Are Not Easy to DefineMating Systems Are Not Easy to Define

95. Three issues complicate the task:
3) Males and females vary in their mating
behavior
95
Mating Systems Are Not Easy to DefineMating Systems Are Not Easy to Define

96. Examination of Birds and Mammals
Reveals One Sharp Split
96

97. Are humans
monogamous
or
polygamous?
97

98. Take-Home Message 9.14
Mating systems—
monogamy, polygyny,
polyandry—describe the
variance in mate number
of males and females.
Mating systems—
monogamy, polygyny,
polyandry—describe the
variance in mate number
of males and females.
They are influenced by
the relative amounts of
parental investment by
males and females.
They are influenced by
the relative amounts of
parental investment by
males and females.
98

99. 9.15 Sexual dimorphism is an9.15 Sexual dimorphism is an
indicator of population matingindicator of population mating
behavior.behavior.
99

100. 100

101. 101

102. Body Size Is an Important ClueBody Size Is an Important Clue
to Behaviorto Behavior
 Level of competition among the individuals of
each sex
 Selection for larger and larger body size when
competition is high
102

103. It’s almost impossible to
distinguish males from females
among most bird species.
Why does that mean they are
monogamous?
103

104. Men are bigger than women.Men are bigger than women.
What does that tell us about our evolutionary
history of monogamy versus polygamy?
104

105. Take-Home Message 9.15
Differences in the level of
competition among individuals
for mating opportunities can
lead to male-female
differences in body size and
other aspects of appearance.
Differences in the level of
competition among individuals
for mating opportunities can
lead to male-female
differences in body size and
other aspects of appearance.
In polygynous species, this
results in larger males that are
easily distinguished from
females visually.
In polygynous species, this
results in larger males that are
easily distinguished from
females visually.
In monogamous species, there
are few such differences
between males and females.
In monogamous species, there
are few such differences
between males and females.
105

106. 9.16–9.17
Communication
and the design
of signals
evolve.

107. Chemical Communication in AnimalsChemical Communication in Animals
107

108. CommunicationCommunication
 An action or signal on the part of one
organism that alters the behavior of another
organism.
 What types of animal behavior require
communication?
 What types of communication do animals use?
108

109. Types of Animal CommunicationTypes of Animal Communication
109

110. Complex Forms of CommunicationComplex Forms of Communication
Honeybee waggle
dance
What is language?
110

111. How is language identified?How is language identified?
 Vervet monkeys
 American Sign
Language taught to
chimpanzees and
gorillas
 Human language
111

112. 112

113. Take-Home Message 9.16
Methods of
communication have
evolved among animal
species, enabling them
to convey information.
Methods of
communication have
evolved among animal
species, enabling them
to convey information.
These abilities influence
fitness and the
evolution of virtually all
other behaviors.
These abilities influence
fitness and the
evolution of virtually all
other behaviors.
113

114. 9.17 Honest signals reduce9.17 Honest signals reduce
deception.deception.
Conveying accurate information
114

115. 115

116. Honest SignalHonest Signal
 Cannot be faked
 Given when both the individual making the
signal and the individual responding to it have
the same interests
 Carries the most accurate information about an
individual or situation
116

117. Deception Evolves!Deception Evolves!
 “Begging” allele
 Evolutionary “arms race”
• Unambiguous signals
• Sophisticated patterns of deception
 An organism’s phenotype includes its
behaviors
117

118. Take-Home Message 9.17
Animals have evolved to
rely primarily on signals that
cannot easily be faked in
order to gain the maximum
amount of information from
them.
Animals have evolved to
rely primarily on signals that
cannot easily be faked in
order to gain the maximum
amount of information from
them.
118