Lecture 1

I will try to post these ‘picture shows’ (projected lecture content)
after each delivery. They are edited after delivery, depending on
what part of the planned syllabus lecture was actually achieved,
and also to clarify content. I do not promise to include everything
said in lecture. Because I ran out of time in this first lecture (too
many asides), I didn’t address levers as I intended. This will be
rectified in the next lecture.
Bio 325
Adaptive morphology of
animals and plants
Fritillary butterflies,
Sept. 8. Theme explained using insect tentorium and insect mouthparts. The 'diagram of forces'
of D'Arcy Thompson; 'imagine it as it isn't'; manifold adaptive systems; organ behaviour;
tentoria of grasshoppers, beetles, gula; mandibles, apodemes, dicondylic joint articulation.
Forces shaped: absorbed, directed, concentrated, distributed. Levers, force advantage, distance
advantage, moments, antagonists.
D. Klimas
Course information: Professor Glenn Morris; >[email protected]<; ‘Office’ lab
Davis 2023B; hours noon to 2 Fridays or arrange by e-mail.
Lab Technician: Susan Dixon; TAs: Samantha Mahabir, Sara Jane Gutierrez, Nikki Sarkar
Website: http://www.erin.utoronto.ca/~w3bio325/,
Lectures: Monday and Wednesday Room 235 Instructional Building
Text: No required text; rather journal articles, lab preambles; website-posted essays,
picture shows that accompany lectures; books on reserve.
Journal of experimental Biology is a particularly good source.
Labs: Mon., Tues, Wed., Thurs., 2-5 pm, Davis 4076
Lab outline: access this each week on website; read preambles ahead of time.
Labs start this week.
Marking scheme
Midterm Test
10% Oct. 6 in lecture
Labwork (Drawings etc.) 1st half
Labwork (Bellringer) 1st half
Labwork (Drawings etc.) 2nd half
Labwork (Bellringer) OVERALL
Final Exam 2h
These course data are also available on the website.
See Sources on website for books on 72-h reserve
Books on 72-h library reserve
Brusca R.C., Brusca G.J. 2002. Invertebrates. Sinauer Associates, Sunderland Mass, 2nd
edition. (For looking up information on invertebrates.) http://go.utlib.ca/cat 4757179
Gordon J.E. 2003. Structures: or Why Things Don't Fall Down. De Capo Press. (A special
book and just a delightful read about stress strain tension compression: an engineer
explains forces entertainingly) http://go.utlib.ca/cat/4074827
Kardong, K.V. 2012. Vertebrates: Comparative Anatomy, Function, Evolution. McGrawHill, N.Y. 6th edition. (For looking up information on vertebrates.)
Ruppert Edward E., Fox Richard S., Barnes Robert D. 2004. Invertebrate Zoology: a
Functional Evolutionary Approach. 7th Edition. Brooks, Cole, Thomson, Belmont CA.
(For looking up information on invertebrates.)
Thompson D'arcy (1974). On Growth and Form. (A classic of biomechanics, to be
sampled) http://go.utlib.ca/cat/4177498
Vogel, S. 2013. Comparative Biomechanics, Life's Physical World, 2nd Edition. Princeton
Univ. Press, Oxford & Princeton. (Bio 325 has no text; but if it had one this would be it.
He emphasizes physical principles not anatomy and he has a gift for clear explanation.)
• Books on reserve. The last book on the list, Vogel 2013, 2nd edition,
is a good source book for all biomechanical aspects of the course;
Vogel just takes a much less anatomical approach than we are in
325. Ruppert et al., Brusca, Kardong are good general sources for
Invertebrate and vertebrate animals. Thompson’s book is a classic
of interpreting structure of historical interest. Gordon on ‘Why
Things Don’t Fall Down’ is an entertaining way of reading about
eyes vary in
Different eye positions on the head give the
owl improved depth perception over the deer.
Andy Newman
Dr. Phil Pointing, UTM original:
entomologist, photographer,
professor, field biologist,
canoeist, fly fisherman,
student of animal and plant
adaptations, especially those
arising from physical factors.
I have dedicated the web page of BIO 325 to Phil Pointing, with whom I
taught the precursor of this course. He was a gifted teacher of many
accomplishments: a fly fisherman who laminated his own fly rods, a
canoeist who built his own canoes; an entomologist (student of insects)
interested in the physical factors affecting insect behaviour, in the leaf
structure of palms, in where trout choose to rest in fast-flowing streams
on Newfoundland’s south coast. He built flight models, ornithopters,
and flew them about the lecture room. He studied predation on pine
shoot moth by bowl and doily spiders. His favourite word was
Course theme: “This course is about the form of organisms and how
organs and body parts behave. It deals with size, symmetry, shape,
texture, colour, topography, materials etc.: with all structural features of
the bodies of plants and animals. The course is part comparative
biomechanics, part physiology, part morphology. We ask especially how
forces are translocated and how body parts work to achieve mobility. The
aim is to examine organisms and hypothesize the history revealed in their
morphology.)” first paragraph from website: re-read the theme periodically
to remind you of what this course aims to do.
Io moth Saturniidae, Automeris io
front row
Defensive display
Bowl and doily spider Frontinella and European pine shoot moth
barrage above doily
enables small
spider predator
to capture larger
moth prey
hanging below and regulating
incoming radiation by position
Suter, R.B. 1981. Behavioral thermoregulation:
solar orientation in Frontinella... Behavioural
Ecology and Sociobiology 8: 77-81.
• A spider hangs below its silk trap waiting for a moth to blunder into
its barrage. Through the day it is exposed to incoming radiation
from the sun. To keep its body temperature within reasonable limits
it positions itself to affect the surface area exposed. The form of its
body and a directed posture (behaviour) combine to regulate
temperature adaptively.
• The structure that one sees is related to behaviour. Insight into
what a structure is adapted to do may depend upon seeing it in
• Suter, R.B. 1981. Behavioral thermoregulation: solar orientation in
Frontinella... Behavioural Ecology and Sociobiology 8: 77-81.
Papua New Guinea katydid in a mist net; Family Tettigoniidae
Form evokes questions; why a
blue posterior to the abdomen?
Why these much larger hind
D. Klimas
Don’t take the morphology of an animal for granted. Question it. Why are
there blue markings on the dorsum of the abdomen of this insect from
Papua New Guinea?
Why is there red colour on the prothoracic femur? Why are the hind legs
so much longer than the others? Don’t just accept form.
To gain insight imagine it as isn’t; then ask why it works better the way
it evolved.
'Why' is an evolutionary or historical question and this course concerns the
history of bodies and organs: why have structures evolved to develop with
certain features of shape, size, stiffness, toughness, elasticity, colour, etc. Why
have these features come to exist in certain taxa, while other features are
lacking? Organism body parts are largely the product of selection in particular
ecological contexts. Inherited structures vary and individuals are selected in
different habitats because their morphology allows them to be more fit.
Manifold adaptive systems: a fairy wren
Dajan Chiou
Illustrating the point that there is more to explaining adaptation than merely
saying a bird’s wings function in flight. There is a dense hierarchy of adaptation
creating a ‘manifold system’ ranging from feather hamuli, to the foramen
triosseum of the skeleton, to the remarkable recurrent bronchi of the rigid lungs
and multiple air sacs of a bird’s respiratory system.
Pinnae comparison
and artificial selection
Ogden Gnash above: standard Schnauzer,
beautiful dog with maladaptive ears
importance of localizing
sounds to a deer or a
• The importance of sound to a deer or wolf is apparent in their pinnae
(the external ear): these animals have relatively large erect dish-like
pinnae, capable of independently swivelling for sound scanning,
naturally selected to collect sound – not blocking flaps like the
Schnauzer (love ‘em, this dog on the truck tailgate is Ogden Gnash).
Ogden’s hearing was deliberately compromised by artificial breeding
for human ideas of ‘cuteness’ – messed up by artificial selection.
Dog breeds give many wonderful examples of maladaptive features.
• Keep in mind that every structural feature is not adaptive.
Sensory capacities differ and morphology puts these differences on the
surface of an animal’s body: a star-nosed mole is infinitely better than us
at smelling dirt but has scarcely visible eyes; this rainforest frog is
nocturnally active and collects light through huge eyes with a huge pupil.
Dita Klimas
Remember that the sensory capacities of animals differ widely.
• Our dogs and cats have different and superior (relative to human)
olfactory systems. Bats hear sounds we cannot hear [the term
‘ultrasonic’ has no relevance re the sound frequencies perceived by
a bat: it is a term defined by human limitations]. Moles smell
chemicals that we cannot smell and frog eyes can collect moonlight
through a huge iris. Sensory organs naturally tend to be on the
outside of the animal’s body where they can carry out their job of
transducing information from the environment. Sensory structures
are thus especially useful in suggesting the lifestyle of an animal.
Functions and effects
not everything is an
some structural features
are effects
Red sponges illustrate how everything is not an adaptation. Some
features have not been selected for and are just an effect of selection
for other features. 100 feet down in a tropical ocean the red
wavelengths reflected by this sponge arise only from the diver’s camera
flash. The red feature of this animal’s morphology is an effect: the
pigmentation of its integument has not been selected because of its
red-wavelength reflecting properties, or to say it differently – the
pigment is perhaps adaptive in some other respect unrelated to its
redness. An alternative explanation is alway pleiotropy.
• Pleiotropy: Pleiotropy occurs when one gene influences multiple,
seemingly unrelated phenotypic traits. The red could be a
pleiotropic effect.
Fall Colours
Anthocyanins: In flowers, bright-reds and purples are adaptive for attracting pollinators.
In fruits, the colorful skins also attract the
attention of animals, which may eat the fruits
and disperse the seeds. In photosynthetic
tissues (such as leaves and sometimes stems),
anthocyanins have been shown to act as a
"sunscreen", protecting cells from high-light
damage by absorbing blue-green and
ultraviolet light, thereby protecting the tissues
from photoinhibition, or high-light stress.
This red colour is not selected for its
information content as a signal. It is an effect
of the loss of the green chlorophyll which
exposes anthocyanins. Anthocyanins are
selected for as … but it is not their red colour
exposure in the fall for which they are
G.K. Morris
Force-related words: stresses etc.
Words associated with force
Law of inertia (Newton’s first law); Law of acceleration (Newton’s
second law); Law of reciprocal action (Newton’s third law); Hooke’s
Law; stress; strain; stiffness, compliance, Young’’s modulus,
breaking strain, shear, tension, compression, pressure, axial stress,
axial strain, shear stress, surface tension, drag, lift, push, pull, load,
buoyancy, gravity, torsional loading, thrust, inertia, couple,
moment ...
Collect force terms and try to use them correctly in describing
organ behaviour and the distribution of forces.
Classic Newtonian approach: to forces, stress and strain
Hooke’s Law
An apple hangs from its stalk. A stress is
in the stalk: a reaction force to the pull
of the force of gravity.
Newton’s 3’rd law: of ‘reciprocal
action’: to every action there is an equal
and opposite reaction. The two forces,
gravity and stalk, balance each other in
this static situation.
Stress is a measure of the load per unit
area, the load of the apple expressed per
unit area of stalk.
The force developed in the stalk may be
further characterized as a tensile force:
an attempt to pull apart.
Though its so modest you can’t see it,
the stalk stretches under tension more
for higher mass apples: that is, the stalk
shows strain, stretching proportionately
farther with larger apples (Hooke’s Law).
• Stress and Strain
• “words stolen by non-scientists to describe the mental condition of
human beings. In this connotation the words have no very precise
meaning and commonly stress and strain are used interchangeably
as if they meant the same thing. All this is a pity because in science
the two words have simple, clear and distinct meanings.” J.E.
Gordon The New Science of Strong Materials
• Stress: load per unit area. Strain: the amount of stretch of a material
under load per unit length
• Hooke’s law: stress and strain are proportional: if a spring stretches
1 cm under a load of 20 kgms it will stretch 2 cm under a load of 40
• It is the forces between the constitutents of the material (between
the atoms etc.) that resist the load.
Cantilevered structures: tension and compression structures
A leaf petiole is cantilevered. One end is built onto the vertical stem, the other
projects sideways and is loaded by the distal weight of the leaf, bending the petiole
downward. The upper portion of the stressed petiole is being subjected to a tensile
stress, the lower portion to a compressive stress. Both kinds of force per unit area
(stress) are greatest on the cantilever surface and diminish toward the middle. For a
structure like this to be hollow is thus not an unacceptable compromise, for the
forces are always greatest toward the periphery and the centre is least important
"The form, then, of any portion of matter, whether it be
living or dead, and the changes of form which are apparent
in its movements and in its growth, may in all cases alike
be described as due to the actions of force. In short, the
form of an object is a 'diagram' of forces..."
D'Arcy Thompson
Body parts, especially skeletons,
evolve to direct forces – stresses (force
intensities expressed as mass per unit
area) are set up within skeletons and
channeled by shape and by material
constitutents; this idea is captured in
this quote from D’Arcy Thompson
which I have enshrined on the website.
Tettigonia head view: the arrows indicate the horizontal level at which the
tentorium is situated within the head, just above the articulations, anterior
and posterior, of the mandibles. During development the tentorial arms
arise as inflections; they meet internally and fuse into the body of the
tentorium. Though these apodemes (tentorial arms) are exoskeleton, the
resulting structure functions just as an internal skeleton
A diagram of forces: the tentorium is what an engineer would
call a truss.
The insect head can be modelled as a six-sided box, one
with no bottom and no rear. Lacking two sides leaves
the two rear corners movable under stress. The
mandibles, mounted beneath the cheeks and rotated
together toward the midline to crush a seed, needs a
firm base. Crushing in the absence of the tentorium
would let the two ‘free’ box corners move apart and
severely reduce the crushing force.
Function of the tentorium: a truss
that keeps the head stable as a
base for mandible rotation.
Locust tentorium from above
When a stress is applied to an insect’s head
Previous slide is of the tentorium of locust viewed from above (dorsal aspect), the
vertex (top) of head removed. The frons (face) is toward the lower right hand
corner of the photo, while the open back of the cranium is in the ‘northwest’. The
anterior arms of the locust are longer and thinner than the posterior, i.e., the body
of the tentorium is not exactly in the centre but shifted posteriorly. There are
dorsal arms [see inset], bracing the face from the rear, but they are weak and not
readily visible in this dissection.
Imagine squeezing the head of an insect with jaws. The direction of an applied
compressive force (an action force) will set up reaction forces in the tentorium,
both tensive and compressive. Some parts will be stressed as a pull and other
parts stressed as a push. With these reaction tensile and compressive forces the
tentorium resists head distortion.
Evolution of the beetle
gular sclerite
Prognathous – forward directed – mouthparts are
typical of Coleoptera and so is the sclerite called a
gula (a sclerite is a region of the cuticular surface,
usually set off by sutures or sulci). A hypognathous
beetle ancestor evolved this prognathous orientation,
accessing food (or prey) in front rather than at its feet.
The region where the posterior arms meetthe cranium
was involved in this head angle change and internally
drew the posterior arms (red) out into a very
lengthened structure.
Moments involve rotation.
“The effectiveness of a force is the product
of the magnitude of the force and the
perpendicular distance from the line of
action of the force to the axis of rotation.”
This is its moment. Making d large increases
the moment of force that the mandible can
Axis of rotation of the mandible is a line
joining the articulation points with the lower
margin of the cranium.
The mandible turning about this axis,
completes an arc of a circle, which can crush
a leaf or seed against the opposing
The mandible, suspended beneath the
insect’s head, is anchored at two
articulations ; joining these articulations
with an imaginary straight line gives an
axis of rotation or fulcrum. The
mandible rotates about this axis,
completing the arc of a circle.
Vogel 2nd edition, See Appendix 2
Motion and Direction, p. 547
Imagine it as it isn’t: imagine the adductor
apodeme insertion at any other locus
around the base of the mandible -- the
moment of force exerted would be smaller.

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