BEHAVIOURAL TRAITS UNDER NATURAL SELECTION

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BEHAVIOURAL TRAITS UNDER NATURAL SELECTION
SHWETA PATEL Id no. - 42537
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What is a Trait ?
Behaviour The response of an organism to
signals from the environment.
Behaviorual Ecology is the study of how animals
interact with their environment and the survival
value of behaviours.

• A characteristic of some organism, like how it
  looks or acts. can be passed down from parents to
  offspring (inherited) and also can be learned

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Ecology
Population Biology
Evolutionary Biology
Genetics
Ethology
Sociobiology
Endocrinology
Neurophysiology
Physiology
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Natural selection

• Natural selection organisms with the most
  favourable traits survive in the natural
  environment and reproduce most successfully.
• The concept of selection is central to Darwin's
  theory of evolution. Behaviours that increase
  mating opportunities and survival will enhance
  reproductive success.

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Three types of Natural Selection

• Directional
• Allele frequencies shift to favor individuals at
  one extreme of the normal range
• Only one side of the distribution reproduce
• Population looks different over time
• Stabilizing
• Favors individuals with an average genetic makeup
• Only the middle reproduce
• Population looks more similar over time
• (eliminates extremes)
• Diversifying (Disruptive)
• Environmental conditions favor individuals at
  both ends of the genetic spectrum
• Population split into two groups

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Levels of Analysis in Ethology
Proximate Causes
Ultimate Causes
Genetic/Developmental Mechanisms
Sensory/Motor Mechanisms
Historical Pathways
Selective Processes
-adaptive context ?
-nervous systems for stimulus
detection -hormone systems for adjusting
response levels -muscles for carrying out
responses
-evolutionary development of a trait

• -effects of heredity
• -development of sensory-
• motor systems
• gene-environment
• interactions

Why?
How?
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The Nobel Prize in Physiology or Medicine 1973

• Karl von Frisch, Konrad Lorenz, and Nikolaas
  Tinbergen "for their discoveries concerning
  organization and elicitation of individual and
  social behavior patterns

• Karl von Frisch- Made major contributions to
  the study of honey bees, their ability to
  communicate to hive mates about food sources with
  the waggle dance, use of pheromones, and their
  ability to see in color and in ultraviolet and
  polarized light.

• Konrad Lorenz- Studied instincts and fixed
  action patterns in birds, and later became
  interested in human behaviours.

• Nikolaas Tinbergen- Studied fish, birds and
  insects in nature and the laboratory and later
  autism.

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Behaviour can Evolve through Natural Selection

• There is variation in behaviours (feeding
  behaviours, attack behaviours, Foraging
  behaviours etc).
• This variation depends on environment and
  animals survival.
• Some behavioural components are genetic - passed
  down from parent to offspring.
• Two Categories of Behaviour
• Innate or Unlearned Behaviour
• Learned Behaviour or Conditioning

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Innate Behaviour

• Innate behaviour is genetically
  programmed. Individuals inherit a suite of
  behaviours (often called an Ethogram).
•   innate behaviours will always be 
• Heritable -encoded in DNA and passed from
  generation to generation
• Intrinsic - present in animals raised in
  isolation from others
• Stereotypic - performed in the same way each time
  by each individual
• Inflexible - not modified by development or
  experience
• Consummate - fully developed or expressed at
  first performance

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Innate behaviour Kinesis

• Kinesis-strong change in activity or turning
  rate in response to stimulus.
• Ex-
• Sow bugs become more active in dry areas and less
  active in humid areas.
• Woodlice become more active in dry areas and less
  in humid areas.

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• Fig 51.7a

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• Fixed action pattern (FAP)
• A sequence of behavioral acts that is essentially
  unchangeable and usually carried to completion
  once initiated.
• FAP is triggered by an external sensory stimulus
  known as a sign stimulus
• FAP usually occurs in a series of actions the
  same way every time.

• Releaser is used for stimuli that have evolved to
  facilitate communication between animals of the
  same species
• Sign stimuli are features of an animal's
  environment to which it reacts in a particular
  way

• For example-
• The fly orchid is a plant that looks like an
  insect which helps it attract pollinators.
•  

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Learned Behaviour

• Learning as a persistent change in behaviour that
  occurs as a result of experience.  Since a new
  born nymph or larva has no prior experience, its
  first behaviours will be entirely innate. learned
  behaviours will always be-
• Non heritable -- acquired only through
  observation or experience
• Extrinsic -- absent in animals raised in
  isolation from others
• Per mutable -- pattern or sequence may change
  over time
• Adaptable -- capable of modification to suit
  changing conditions
• Progressive -- subject to improvement through
  practice

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• Habituation - Loss of responsiveness to stimuli
  that do not convey useful information (cry wolf
  effect).
• Ex-
• A puff of air on the cerci of a cockroach will
  cause the animal to scamper away.  But repeating
  the same stimulus over and over will lead to a
  decrease in the response and eventually to no
  response at all. 
• In some insect populations, widespread use of sex
  pheromone will disrupt mating behaviour.  smell
  like a virgin female, males become habituated to
  the odour and stop responding to the signal. 

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• Classical Conditioning - Is learning to associate
  one stimulus with another, unrelated stimulus. 
• for example-
• Honey bees, learn to associate floral colours
  and fragrances with the presence of nectar.  They
  can be "trained" to collect sugar water from
  coloured dishes on a feeding table.  If a blue
  dish with pure water sits next to a yellow dish
  with sugar water, worker bees will quickly learn
  to associate "yellow" with "food.When solutions
  in the two dishes are suddenly swapped , the bees
  will ignore blue and continue to forage at yellow
  until they eventually "learn" (by trial and
  error) to look for the blue dish.

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• Latent Learning involves memory of patterns or
  events when there is no apparent reward or
  punishment associated with the behaviour. 
• for example-
• A sand wasp learns the location of her nest site
  by taking a short reconnaissance flight each time
  she leaves the nest.  She remembers the pattern
  of surrounding landmarks to help her find the
  nest when she returns. 
• worker ants can remember a series of landmarks
  along a trail and follow them (in reverse order)
  back home to the nest site. 
• Honey bees also show latent learning when they
  follow the waggle dance of a forager and then use
  that information to find the reported nectar
  source.

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Operant Conditioning - learning in which an
animal is rewarded or punished for performing a
behaviour. Ex- Cockroaches learning to run
through a simple maize to find food is a simple
example of operant conditioning (also known as
instrumental learning). Rats in Skinner box  
trial by error learning

• Imprinting- Is a special case of programmed
  learning that occurs early in life and only
  within a short time-window known as the "critical
  period". 
• Ex-
• Fruit fly larvae will imprint on the taste and
  smell of their food.  If reared on a diet that
  contains apple extract, adult females will show a
  strong preference for apples when they eventually
  search for a place to lay their own eggs. 

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Proximate and ultimate perspectives on imprinting
in graylag geese
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In a classic experiment, Niko Tinbergen Tinbergen'
s Observations on the Bee Wolf - Philanthus
triangulum
1.Observation - Female flies in a circle before
going to hunt.
3. Prediction - Female will return to a
landmark to find the nest.
2. Hypothesis - Female is using landmarks to find
the nest.
4. Test - Place an artificial landmark around
the nest and move it when the female is away
5. Result - Female orients to new landmark.
6. Confirm hypothesis ?
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Auditory Communication

• Experiments with various insects

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Behavioural traits evolve by natural selection

• Agelenopis aperta a funnel web spider occurs in
  both desert and riparian (riverside) woodland.
• Desert spiders (which occur in food-poor
  habitat) are much more aggressive and attack
  potential prey much more quickly than riverine
  spiders.

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• 51.19

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Optimal foraging
In optimal foraging organisms maximize their food
intake while minimizing their energy expenditure
and risk of mortality.

• Zachs crow work
• Crows feeding on whelks (marine snails) fly up
  and drop the whelks on rocks to break them.
• Height from which a shell is dropped affects its
  probability of breaking.
• Dropping from greater height increases
  probability of breaking shell, but it costs
  energy to fly up.

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• Fig 51.22

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Risk of predation is one of the most significant
potential costs to a forager

• Mule deer are preyed on by mountain lions
  throughout their range. Risk of predation varied
  greatly upon areas.

•   Mountain lions killed most mule deer at forest
  edges.
•   Few were killed in open areas and forest
  interiors.

• Mule deer feed predominantly in open areas,
  avoiding forest edges and forest interiors. When
  deer are at the forest edge, they spend
  significantly more time scanning their
  surroundings.

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Risk of Predation

• Bluegill sunfish feeding on Daphnia of different
  sizes at different prey densities
• At low densities, there was little selectivity

• At high prey densities, there was significant
  selectivity for feeding on larger prey sizes
• This minimizes capture and handling costs and
  maximizes payoff to the fish

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Environment influences the behaviour

• The California mouse (Peromyscus californicus) is
  monogamous and like male prairie voles, male
  California mice are highly aggressive to other
  mice and provide considerable parental care.   
• Researchers placed new born California mice in
  the nests of white-footed mice and vice-versa.
  This cross-fostering changed the behaviour of
  both species.
• Cross-fostered California mice provided less
  parental care and were less aggressive toward
  intruders when they grew up and reared their own
  young.
• Their brains had reduced levels of AVP, compared
  with California mice raised by their own parents

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Mating Behaviour Mate Choice

• Mating behaviour is the result of sexual
  selection.
• As other behaviours, must enhance reproductive
  success (fitness).

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Sperm competition

• Males compete not only to mate with females, but
  frequently engage in sperm competition as well.
  More sperm a male can insert the higher his
  chances of fertilizing eggs (like a lottery).
• Ex-
• Males also commonly remove other males sperm
  (e.g. damselflies have a penis with spines), plug
  up females reproductive tract (many insects) or
  guard females against other males.

Altruistic Behaviour

• behaviour that appears to decrease individual
  fitness but increases the fitness of others.
• For example-
• Many animals give alarm calls that warn others
  of a predator but put the caller at risk.
• In bees, ants and other social insects many
  individuals do not reproduce themselves but
  assist another individual (the queen) to
  reproduce.

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Behavioural traits evolve by natural selection
Drosophila foraging

• In lab studies in low density populations of
  Drosophila for S allele increased in frequency.
  Opposite was true in high density populations.
• In low density populations for S individuals did
  not waste energy traveling long distances for
  food. In high-density populations for R allele
  caused larvae to move beyond areas of food
  depletion.

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Behavioural traits evolve by natural selection-
Drosophila foraging

• Two alleles in a gene for foraging for R and for
  S.
• For R rover larva moves more than average.
• For S sitter larva moves less than average.

Foraging pathways of individual Drosophila larvae
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