Transcript Behavior & Learning Review

• Chapter 39 Behavioral Biology
Behavior
• What is Behavior?
• Behavior Ecology – studies how
behavior develops, evolves, and
contributes to survival and reproductive
success
• Causation?
– Proximate
– Ultimate
Figure 51.7 A kinesis and a taxis
Dry open
area
Moist site
under leaf
(a) Kinesis increases the chance that a sow bug will encounter and
stay in a moist environment.
Direction
of river
current
(b) Positive rheotaxis keeps trout facing into the current, the direction
from which most food comes.
Figure 51.9 Minnows responding to the presence
of an alarm substance (pheromone)
(a) Minnows are widely dispersed in an
aquarium before an alarm substance is
introduced.
(b) Within seconds of the alarm substance being
introduced, minnows aggregate near the
bottom of the aquarium and reduce their
movement.
Ethology
•
Ethology – the scientific study of animal
behavior
•
Tinbergen, Konrad Lorenz, Karl
VonFrisch (mid 1900’s)
– Four Questions:
• What is the mechanistic basis of the
behavior? (proximate)
• How does development of the animal
(zygote to mature) influence behavior?
(proximate)
• What is the evolutionary history of the
behavior? (ultimate)
• How does the behavior contribute to
survival and reproduction (fitness)?
(ultimate)
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Fixed action pattern (FAP)- sequence of
acts; unchangeable; carried to completion
Sign stimulus- external sensory stimulus
Ex: 3 spined sticklebacks (Tinbergen ‘73
Nobel)
Sign stimuli in a classic fixed action pattern
(a) A male three-spined stickleback fish shows its red underside.
(b) The realistic model at the top, without a red underside, produces no
aggressive response in a male three-spined stickleback fish. The
other models, with red undersides, produce strong responses.
Proximate and ultimate perspectives on aggressive behavior by
male sticklebacks
BEHAVIOR: A male stickleback fish attacks other male sticklebacks that invade its
nesting territory.
PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus
that releases aggression in a male stickleback.
ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreases
the chance that eggs laid in his nesting territory will be fertilized by another male.
Learning?
•
Maturation is the situation in which a behavior may improve
because of ongoing developmental changes in neuromuscular
systems, for example, flight in birds.
• As a bird continues to develop its muscles and nervous system,
it is able to fly.
• It is not true learning.
•
Habituation- loss of responsiveness to stimuli that convey no
information; simple learning
•
Imprinting- limited learning within a specific time period
•critical period (Lorenz, ‘73 Nobel)
•
Associative learning (learn to associate one stimulus with another):
•classical conditioning- (arbitrary stimulus) Pavlov’s dogs
•operant conditioning (trial and error)- “Skinner’s box”
Proximate and ultimate perspectives
on imprinting in graylag geese
BEHAVIOR: Young geese follow and imprint on their mother.
PROXIMATE CAUSE: During an early, critical developmental stage, the young
geese observe their mother moving away from them and calling.
ULTIMATE CAUSE: On average, geese that follow and imprint on their mother
receive more care and learn necessary skills, and thus have a greater chance of
surviving than those that do not follow their mother.
•Spacial Learning
•Landmarks
•Niko Tinbergen Digger
Wasps 1932
Fig. 51.2
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Does a digger wasp use landmarks to find her nest?
EXPERIMENT A female digger wasp excavates and cares for four or five separate underground nests, flying to each nest daily with food for the
single larva in the nest. To test his hypothesis that the wasp uses visual landmarks to locate the nests, Niko Tinbergen marked one nest with a ring
of pinecones.
Nest
After the mother visited the nest and flew away, Tinbergen
moved the pinecones a few feet to one side of the nest.
RESULTS
When the wasp returned, she flew to the center of the pinecone circle instead of to the nearby nest. Repeating the experiment with
many wasps, Tinbergen obtained the same results.
Nest
CONCLUSION
No Nest
The experiment supported the hypothesis that digger wasps use landmarks to keep track of their nests.
• Songbird
repertoires
provide us with
examples.
– Why has natural
selection
favored
a multi-song
behavior?
Fig. 51.5
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• It may be advantageous for males attracting
females.
Fig. 51.6
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OPTIMAL FORAGING
•
Cost-benefit (ROI) analysis of foraging behavior.
– Foraging is food-obtaining behavior.
• The optimal foraging theory states that natural selection will benefit
animals that maximize their energy intake-to-expenditure ratio.
• Whelk (mollusk)-eating behavior in crows (Reto Zach)
Height of
Drop (m)
Average Number
Of Drops Required
to Break Shell
Total Flight Height
(Number of Drops 
Height per Drop)
2
3
5
7
55
13
6
5
110
39
30
35
15
4
60
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 51.7
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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THE EVOLUTIONARY LOGIC OF BEHAVIORAL ECOLOGY
Fitness is a central concept in animal behavior. Since natural selection works
on genetic variation caused by mutation and recombination, organisms should
have features that maximize fitness over time. Animals are expected to engage
in optimal behaviors:
Optimal behavior = A behavior that maximizes individual fitness.
Optimal behavior is a valid concept if behavior is genetically influenced and
subject to natural selection. An experiment was carried out that demonstrated
that genes influence behavior.
Experiment
Two species of lovebirds were interbred. Female Fischer's lovebirds cut long
strips of nesting material, which are carried individually to the nest. Female
Peach-faced lovebirds cut short strips and carry several at a time by tucking
them into her back feathers.
Results
Hybrid females cut intermediate length strips and tried, but failed, to transport
them by tucking into back feathers. They learned to carry strips in their beaks,
but never gave up all tucking behavior.
Conclusions
Phenotypic differences in the behavior of the two species are based on
different genotypes. Innate behavior can be modified by experience. Learned
behaviors are typically based upon gene created neural systems that are
receptive to learning.
Fig. 51.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Social behavior
• Sociobiology- evolutionary theory applied
to social behavior (Hamilton)
• Agonistic behavior- contest behavior
determining access to resources
• Dominance hierarchy- linear “pecking
order”
• Territoriality- an area an individual
defends excluding others
• Mating systems:
•promiscuous- no strong pair bonds
•monogamous- one male/one female
•polygamous- one with many
•polygyny- one male/many females
•polyandry- one female/many
males
Social Interactions
Animal Signals and Communication
Signal: Behavior that causes a change in behavior of another animal
Communication: Transmission of, reception of, and response to
signals
- Pheromones – chemical signals (communicate by odor)
Honeybees – pheromones produced by a hive’s
queen and her daughters, workers, maintain social
order in the colony.
- Movement – Honeybee Waggle Dance (VonFrisch)
Altruistic behavior
•
Inclusive fitness- total effect an
individual has on proliferating its
genes by its own offspring and aid to
close relatives
•
Kin selection- aiding related
individuals altruistically
•
Hamilton’s Rule
– Coefficient of relatednessproportion of genes that are identical
because of common ancestors
•
Reciprocal altruism- exchange of
aid; humans?
Hamilton’s Rule – Kin Selection
KIN SELECTION & ALTRUISM
Kin Selection: selection of a trait through helping
relatives, either
1.
descendant kin (offspring):
direct selection
- or -
2.
non-descendant relatives:
indirect selection
inclusive fitness = direct + indirect
nepotism = helping relatives other than offspring
(descendant kin)
Fitness Accounting
A female Belding ground squirrel is dying. During her life she
has successfully raised a total of 10 of her own offspring. She
has helped her parents rear 8 offspring, 2 of which would not
have survived without her help. Her altruistic acts (e.g., alarm
calls) have resulted in her having the equivalent of 3 more
offspring. In terms of numbers of offspring, what is her
 Direct fitness? 10
 Indirect fitness? 2 + 3 = 5
 Inclusive fitness? 10 + 5 = 15
Three factors are important in the spread and
maintenance of an altruism gene by kin selection:
1. benefit to recipient, B
2. cost to altruist, C
3. degree of relatedness between altruist and recipient, r
Coefficient of Relatedness “r” =
1. probability that a rare gene is shared by two
individuals,
OR
2. the proportion of genes shared by two individuals
Taken From: Hamilton's Theory, by: B Brembs, 2001 Academic Press
Hamilton’s Rule states the conditions under
which altruism will spread. In its simplest
form it is:
rB > C
“The Story of The Surfing Brothers”
Two brothers (close in age, not fathers yet, reproductively fertile)
decide to go surfing. As they are surfing, one brother (the
beneficiary) is dragged under the current and is in danger of
drowning. The other brother (the altruist) decides to attempt to
save his brother, thus risking his own life. This decision, on its
face, seems very natural and devoid of conscious thought.
However, we need to find out if there are ultimate (evolutionary,
even “selfish”) causes for the altruist’s decision.
Let’s quantify this decision using Hamilton’s Rule!
rB > C
r = .5 (sibling = .5 co-efficient of relatedness
B = 2 (amt. of projected offspring for beneficiary)
C = 2 x .05 (amt. of proj.offspring for altruist x RISK)
(the risk of the altruist dying while trying to save the brother is .05)
Thus: rB = .5 x 2 = 1
C = 2 x .05 = .1
or
rB > C = 1 > .1
Thus, Hamilton’s Rule would dictate that this
action would be profitable in a genetic or
evolutionary sense!
Other Cases
• Uncle saving Nephew: .25 x 2 = .5 > .1
– Profitable!
• 1st Cousin saving 1st Cousin:
.125 x 2 = .25 > .1
– Profitable!
Kin Selection Weakens with Hereditary Distance!
Other Considerations – Haplodiploidy
Relationships
•
Haplodiploidy. The Hymenoptera (bees, ants and wasps) provide the perfect window
into sociobiology as explained by Hamilton's rule. They are haplodiploid; males are
produced from unfertilized eggs, having only half the normal genetic number as the
females. The result of this is that sisters, who usually have the same father and all of his
genes, are related by 3/4. To their mother and to their offspring they are related by only
1/2. Therefore, Hamilton's rule essentially predicts that sisters should be prone to
sacrificing for each other. In a family situation (a hymenopteran colony for example)
this amounts to sisters cooperating in raising more of their own generation and in risking
their lives to defend the colony, which is made up mostly of sisters.
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Problems with the genetic explanation. In most eusocial colonies, the primary
reproductive ("queens") mates more than once, reducing the degree of relatedness
between her daughters. Therefore, the effects of haplodiploidy in kin selection are
reduced. Also, the termites, the only completely eusocial order, are not haplodiploid at
all.
A Final Word
This situation is purely fictitious and not
meant to suggest that a human being would
actually calculate the benefit of saving
another human being. This example deals
with deeply engrained ultimate causes of
behavior, meant to preserve a species,
which have been passed on genetically over
time (evolution) . Hamilton’s Rule
quantifies a rationale for passing on a gene
for altruistic behavior.