10
Biology 3401 - INTRODUCTION
COURSE ADMIN.
A. - who I am
- where I live - Flemington 207
- when I’m there – Office hours – 9:30 MWF, 9 TTh
B Who’s in the course
- read list
C COURSE INFO
- where stuff is on Web site – Go Through Website
- Labs
- Essay +topics
- Plagiarism
Handouts - Syllabus
- Schedule
General Intro to Course
Course roughly divided into two parts
(1) proximate causes of behaviour
- answer the “how” question about behaviour
- emphasis on mechanisms which govern & generate behaviour patterns
- genes
- hormones
- nerves
- this will go until early October
(2) Ultimate causes - identify & build evolutionary history of behaviour
- how has behaviour evolved
- what purpose or function does it have?
- what is the adaptive context
WHEN POSSSIBLE – HOPE TO SHOW HOW THESE ARE INTERRELATED
This entire series of questions will be addressed using scientific method
QuestionÞ observation
Þ hypothesis
Þ prediction
Þ test
Þ conclusion
CLASSIC EXAMPLE OF THIS
NIKKO TINBERGEN
- Expt. on beewolf – wasp -Philanthus triangulum
IMPORTANT OBS.
(1) females nest in sand
(2) - dig burrow - with brood cells
each cell has egg and paralysed bee
(3) female leaves - covers rest with sand and flies to get prey
- 1 Km
(4) returns to nest and opens it
question - how does she find it?
observation - female flies in circle before going to hunt
hypothesis - female is using landmarks
prediction - female will return to landmark to find nest
test - place artificial landmark around nest and move when female is away
result - female orients to moved landmark
conclusion - verify hypothesis
note = never ‘prove’ anything
HISTORY OF STUDY IN ANIM. BEHAVIOR
Humans – been aware of the behaviour of other animals since mankind first appeared
- in context of hunting (being a predator) or not being prey
Greeks – Artistole – introduced concept of a ‘Type” or the perfect form of anything
- notion that variation was an imperfection in the system
This idea persisted until Darwin
- study of beh shared by
Biology *
Psych *
Anthrop.
- historically ethol. & psych are related but have different approaches
Ethol. Psych
- Origins on nat hist origins on physiol & med.
- early focus - - early focus
- understanding - understanding
adaptive function causation and motivation
of beh in wild of human beh.
- using animal models
- field based - lab based
- initially more observational - initially empirical
So ... most early ethologists
- naturalists - & observers of nature
- most clergy in Britain
- amateur naturalists - spend lots of time observing & collecting
- in early 19th century in England
- natural history - v. popular
- out of that tradition
- came a more rigorous - theory-based study
Britain
Darwin
- significant contribs
- behaviour as a means for achieving reprod. success
- trace evol. origins
(I would agree: this separates ethol. from psych to this day)
- 3 books
Origin of Species (1859)
- behaviour patterns - complex reflexes that were subject to natural selection
Descent of Man (1871)
- outlined evol. of sex differences
- colour & courtship behaviour of male
- sexual selection
Expression of Emotions in Man & Animals
- comparative study of evol. of expressions & behaviour in humans - comp. with animals.
- emphasized function of beh. in social communication
- comparative method
Darwin’s Contrib.
(1) theory of nat. sel. - let us consider beh. in evol. terms
(2) views on “instinct”
- modifiable units of beh.
- modifiable by evol.
(3) methodology
- comparative method
-continuity between behaviour of humans with other animals
(2) Douglas Spalding
- studies of instinct (inherited beh.)
- looked esp. at instinct in relation to learning
- imprinting
(3) Lloyd Morgan (late 19th)
- experimental
- need for simple objective descriptions
- operational definitions
- controlled experiments - led to dev. of experimental analysis of beh.
(4) Julian Huxley
- one of the first professional zoologists to work on beh.
- studies of birds - systematic field studies that tested Darwin's theories
(B) In USA
- the dev. of ethology
- short circuited - by rise of school of animal behaviourism
- founded by John B. Watson (1910) (d. 1959)
- stressed that animal behaviour - explained as series of learned responses
-respond to the positive reinf. stimul
- conditioning
- lab oriented
- criticized by European ethologists - too divorced from reality
early dev. of ethol. in USA
- delayed due to popularity of behaviour & influence of B.F. Skinner (d. 1990)
(C) Continental Europe
Karl von Frish
- dance language of bees
- major contributions
- comparative neuroethology
- how animals obtain information from env.
- communication systems
- showed colour discrimination - used conditioning techniques
- introduced notion of “Umwelt”
- animal’s perceptual world
- different from ours
- e.g. UV perception in bees
- 1923 - described dance of bees.
Konrad Lorenz
- father of ethology
- discovered & elucidated most of current concepts in ethology
- concerned with observed animals in undisturbed states
- took ideas about ‘instincts’ (often competing ideas) and work out a theor. system for how instincts could work
- could be used in experimentation
Niko Tinbergen
- viewed as co-founder of ethol. (w Lorenz)
- developed field methods
worked on
(1) stimulus control of beh. - (sign stimuli)
- simple models
(2) relationship between beh. & ecology (infl. of habitat on beh.) - e.g. pred. avoid.
(3) adaptive functions of beh.
(eggshell removal, nest spacing )
in 1973 – Lorenz, Tinbergen, von Frisch – joint Nobel Prize
Behaviour
definition -
- simplest definition
- movement (or motor patterns)
- can include
- movements of any body part
- vocalization
- chemical release
- colour change
more realistic definition
- series of coordinated muscular contractions
How is it described and organized
- most often study
- series of temporal sequences
- “motor patterns” or “units”
- complex beh.
- can be produced by simple motor patterns
- all put together
e.g. spider web building
- it is important in all of this
- recognize patterns unambiguously & be able to describe them
- first lab exercise
- about recognition, naming, desc., freq & duration of beh.
but so far
- what I’ve said can be applied to rats in boxes or mating elephants
what we’re dealing with - biological study of behaviour
- ethology - coined by Tinbergen (1963)
- from Greek ‘ethos’ - habit
How do we go about conducting research on animal beh.
- what we’re interested in
HOW? (1) underlying control mech
WHY? (2) function (adaptive signif)
Again go back to Tinbergen - deal with beh. by asking four questions
(A) Proximate causes BIRD SONG
(1) Causation
- neural mechs ?
- hormonal ?
- environmental (external) stimuli
- precedent events
e.g. long theory testosterone singing
spring photopd.
(2) Development (Ontogeny)
- changes with age
- interaction of genes and envir. in determ. beh.
- innate vs. learned (acquired)
e.g. song pattern - learned by nestling during sensitive early phase - hears
(B) Phylogenetic
- how a particular behaviour pattern is expressed in related species
- what this can tell us about evol. within a
All these questions are independent
i.e. can study one without the other
To summarize all this
Proximate Mechanisms of Behaviour
- behaviour
- can be organized into different time-based events
- molluscs - insect song
- escape
- months - seasonal cycles of behav. (reprod.)
implication here
- beh. - under some kind of variable control mechs
For this part of course - we will look at
(1) responses to external stimuli
(2) role of nervous system
(3) role of endocrine system
(4) role of genome
STIMULI
- when we talk about how to study proximate mechs of behaviour
- looking at how stimuli affect behav.
Stimulus
- (physiologically) any per in the animal’s internal or external environment which results in in membrane physiology of a receptor neuron leading to action potential.
SENSORY & NEURAL MECHANISMS
- an absolutely basic concept to all considerations of processing stimuli
- actions of nerves
any nerve cell
- impulses move by the differential movement of K+
Typical neuron
- in this situation
- have a chemical gradient &
electrical in equilibrium
- if measured this
equilibrium - get equilibrium
potential - 65 mV
- resting potential
- if nothing happened to stimulate a nerve
- this resting potential would stay at
- 65 mV forever
- but that’s not what happens
two terms
(1) depolarize - make inside of neuron more positive
(2) hyperpolarize - make inside more negative
- if use small current
- into neuron
small depolarization
- if increase current
action potential
membrane
current
action potential
- brought about by
movement of Na+ ions
- this action potential moves down neuron
- 120 m/s (432 Km/hr)
but eventually - action potential moves to end of neuron
- must cross to another neuron across a space called a SYNAPSE
Presynaptic cell
SYNAPSE
Postsynaptic cell - action potential
causes release of
neurotransmitter
- amines
- amino acids
- peptides
- neurotransmitter
- causes depolarization of
postsynaptic cell
ALL OF THE STIMULI WE MENTIONED
- detected via receptors
All receptors - transducers
- change signal in some modality into a nerve impulse
- one of five types
Chemo
Mechans
Electro
Thermo
Photo
Chemoreceptors
- characterized as
(1) gustatory - taste
(2) olfactory - smell
Gustatory
- all animals differentiate good vs. bad food
- transduction mech.
- depends on kind of taste being encountered
e.g. - salt/sour
- directly influence ion chemicals on receptor membrante
- sweet
- involves 2nd messenger and of chemical reactions which opens ion channel
Olfactory receptors
- can be very sensitive and detect very low concentrations
- e.g. male moths - pheromones
- have 75,000+ receptors/antennae
- small animals olfactory receptors are protected
- inverts - fluid
- vertebrates - mucous
chemicals
must be dissolved
second messenger
- transduction - complex
MECHANORECEPTORS
- wide range of uses
can respond to - touch
- pressure
- stretching
- sound
- all mecchanoreceptors
- depend on movement of some structure which triggers neuron
e.g.
- found in inner ear - balance
other kinds
- eardrum
- proprioceptors
Electroreceptors
- some fish
- modified hair cells
- can sense either
- weak electrical signals from muscles of prey
OR
- gen in generated electrical field
Thermoreceptor
- snakes - sense infrared
Photoreceptors
- light sensors
- excitable photopigments
- structural in pigments
cascade of reactions
depolarization and action potential
Photo receptors
- can be v. simple
e.g. flatworm - detect dark vs light
- worm avoid bright areas
Insects & Crustaceans
- more complex compound eye
Finally - have vertebrate
- very complex - already know structure
short review - to this point have
(1) method for transmitting nervous signals through body
(2) method and structures for transducing stimuli of all kinds into
one simple e.g. of this illustrates how nerve cells and stimuli are directly related to a behaviour
crayfish/lobsters
- escape response
- tail flip when touched ( mechanoreceptors)
in CNS of crayfish
- large nerve cells - giant interneurons GE’s
- one of these - Lateral Giant inerneuron LGI
- demonstrates a correlation between the behaviour and neuron firing
illustrates that LGI is sufficient for response
- hyperpolarize nerve
- block ability to
One problem with all stimuli is that there are so many of them
and an animal must filter out all kinds of stimuli
- this processing can occur peripherally (at receptor level) or centrally (in brain)
e.g. of this - toads preying on worms
- how does a toad recognize prey?
- if go through sequence of events
- if a prey item moves into i ts visual field
- turns toward prey
fixes on it
leans forward
sticks out tongue
question is
- how does toad recognize prey?
Researchers - Ewert in a series of papers
- used the initial orientation response to answer question
- moved cardboard models past toad
- found that choice is made on 2 characteristics
(1) length of object
(2) relationship of length to movement
- specifically
How is toad doing this?
- first level of processing is at
as ‘prey’ enters visual field
- small object will excite receptive field
+ bipolar cells become depolarized
info to
i non-prey enters visual field
- covers a lot of inhibitory field
- cause hyperpolarization & no signal sent
st: at first level
- have selective response to shape characteristics of prey
(2) AT BRAIN LEVEL
- in optic tectum
- visual area of brain - integration
- class of neurons - T5(2)
- responds to characteristics that identify ‘prey’
Then through optic tectum & thalamus control motor pattern generators
These motor patterns
motor output
Optic tectum can also tell small vs. large moving object
- large moving object - probably
- leads to generation of another motor pattern flee
Some more e.g.’s
Peripheral Filtering
Audition (Mechanoreceptors)
- for e.g. bats can detect > 100 KHz
moths can detect > 100 KHz
humans - < 20 KHz
There is also an evol/ecol component in this
e.g. bats/moths
- Fullard/Fenton
- all peripheral filters
- share feature of eliminating unnecessary information
Central Filtering
- mechanisms for this - largely unknown
- ethological research - can only suggest the capacity for CNS filtering exists
- need to establish it neurophysiological
how - record from sensor
- if sense organ responds & animal doesn’t behaviour
- suggests some central filtering
- in female canaries
- ventral Hyperstriation (HVc region)
- hypothesized to allow song recognition
- female canary
How does this work in nervous system
Central Pattern Generators (Motor Pattern Generators)
- cluster of pre-motor neurons in CNS
- generate pattern of impulses - pattern of muscle contractor
best studied
- those that regulate locomotion
- esp. among invertebrates
e.g. in book - locust flight
- importance - can fly only if wings move in precise pattern
having central pattern generator
- a good thing
an e.g. where this is not involved
- far simpler kind of beh