Transcript Costs and benefits of behavior

Month Day
Topic
Nov.
3
Behavior
6
Costs and benefits of behavior
8
Populations
10
Holiday!
13
Communities I
15
Communities II
17
Ecosystems
Ecological studies of
behavior focus on:
How organisms make
“decisions” that influence their
survival and reproductive
success.
Outline
• Important behaviors for survival and
reproduction
• Social acts
The economics of behavior
• Time and energy-limited
• Organisms must balance tradeoffs among:
– Energetic costs—food
– Risk costs—mortality
– Opportunity costs—missing out
• Balance yields survival and reproduction
How do organisms choose
where to live?
• Habitat cues
• Good predictors of conditions suitable
for future survival and reproduction
How do organisms choose
what to eat?
Optimizing foraging choices...
• Natural selection has molded behavior
so that organisms make the “best
possible choices”
Optimizing foraging choices...
• Natural selection has molded behavior
so that organisms make the “best
possible choices”
• An organism may choose to optimize
– Carbon gain
– Nutrients or vitamins
– Safety
– Other things?
How do organisms choose
mates?
How do organisms choose
mates?
• The right species
How do organisms choose
mates?
• The right species
• A high quality mate
How do organisms choose
mates?
• The right species
• A high quality mate
• A mate with resources
How do organisms choose
mates?
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The right species
A high quality mate
A mate with resources
The male/female thing…
Mating tactics
• Abundant sperm and scarce eggs make
a female’s mate choice very important
– Females—get the best sperm
– Males—mate as many times as possible
Mating tactics
• Abundant sperm and scarce eggs make
a female’s mate choice very important
– Females—get the best sperm
– Males—mate as many times as possible
• Female choice can lead to sexual
selection for exaggerated traits
Mating tactics
• Abundant sperm and scarce eggs make
female mate choice very important
• Female choice can lead to sexual
selection for exaggerated traits
• Social and genetic partners may differ
Why live in groups?
Benefits of social behavior
• Protection
• Foraging
Subordinate member of a wolfpack
Cooperative defensive behavior among musk oxen (Ovibos moschatus)
Costs of social behavior
• Disease
• Interspecific competition for food and
other resources
Categories of social acts
Why would an animal perform
a behavior that inflicts a cost
on its self?
Altruistic Behavior
• Nonbreeding helpers are found in
mammals, birds, and insects
• Altruists apparently sacrifice their
reproductive success to help others
• How are genes for altruism perpetuated?
Altruism among genetically
related individuals
Kin selection:
the benefits of increasing a relative’s
reproductive success are greater than
the cost of decreasing the altruist’s own
reproductive success
Theory of Indirect Selection
• Genes associated with caring for
relatives may be favored by selection
• Altruists pass on genes indirectly by
helping relatives who have copies of
those genes to survive and reproduce
Extreme altruism:
Eusocial animals
Naked Mole-Rats
• Only mammals known to have a sterile
worker caste
• Single queen reproduces with one to
three males
• DNA evidence shows clan members are
all closely related
Altruism among unrelated
individuals
Reciprocity
Considering Human Behavior
• Some human behavior may be adaptive
or may have been adaptive in the past
• Testing hypotheses about human
behavior can help us understand how
they arose
Redirected Behavior
• Certain behaviors that are normally
directed toward relatives may
sometimes be directed toward
nonrelatives
• In this case, the redirected behavior is
nonadaptive
Human Adoption
• Evolutionary theorists predict that
people would be more likely to adopt
related children than nonrelatives
• Studies have shown that in traditional
societies this is true
• Adoption of nonrelatives may be an
example of redirected behavior
Moral Questions
• A behavior that is adaptive may or may
not be desirable or moral
• Some behaviors that were adaptive in
small groups, such as adoption, may no
longer be adaptive in large societies
• A nonadaptive behavior may be socially
desirable