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 COMPARATIVE BIOMECHANICS Fritillary butterflies, Nymphalidae Syllabus plan 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 5% Labwork (Bellringer) 1st half 10% Labwork (Drawings etc.) 2nd half 5% Labwork (Bellringer) OVERALL 20% Final Exam 2h 50% 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.) http://go.utlib.ca/cat/7777054 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 forces. Vertebrate eyes vary in parallax 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 ‘interesting’. 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 surprise 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 operation. • 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 limbs? 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 wolf Animal Wildlife • 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 adaptation 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. (Wikkipedia) 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 selected. 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 kgm. • 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 structurally. "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 Gula 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 apply. 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 mandible. 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.