lsm3261_lecture 8 --- animal diversity and basic designs

8/3/2019 LSM3261_Lecture 8 --- Animal Diversity and Basic Designs

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LSM3261 - Lecture 08

Animal diversity andbasic designs

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To appreciate the diversity of animal life formsby examining representative members in animal

diversity and prominent body plans.

To be introduced to life form and function inanimals.

To learn about some basic designs in the animalworld throughmorpho-anatomical designs andfunctional adaptations.

Objectives

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Scope! 1. The Animal Kingdom

! 2. A basic plan.! 2.1 Echinoderms

! 2.2 Arthropods

! 2.3 Tetrapods

! 2.4 More than onesolution

! 3. Physical laws constraintson animal forms

! 3.1 Hydrodynamics

! 3.2 Aerodynamics andgravity

! 3.3 Exchange ofmaterials withenvironment

! 3.4 Small, simpleorganisms high surfacearea:volume ratio

!

3.5 Larger animals lowsurface area:volume ratio

! 4. Basic Designs

! 4.1 Sphere

! 4.2 Cylinder! 4.3 Spirals

! 4.4 Angles

! 4.5 Radials

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1. Animal Diversity 1.5-1.8 million species described. Estimated

total of 4 to >30 million

Found virtually everywhere Aquatic (freshwaters to deep sea), terrestrial

(subterranean to montane), aerialenvironments

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1b The Animal Kingdom

For a refresher(not details) of the animal

kingdom, see: Solomon et al., 2011; Hickman et al., 2011 Google/NUS Digital Library

This module will mostly refer to broadgroupings such as phyla.

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E meta oa


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Eumetazoa

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Tremendous diversity of form and function ultimatelyaddresses a set of common general challenges faced by most

animals:

Obtaining oxygen

Obtaining food

Excreting waste Movement

More than one solution to

a problem

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2. A basic plan and

deviations.Much of the diversity of forms in animals consists ofmodifications and specialisations of a few basic bodyplans and shapes.

Examples:

2.1 Echinoderms

2.2 Arthropods

2.3 Tetrapods

Each living group shares acommon basic structuralplan, but contains many

members that deviate fromthe basic design in response

to selection pressure.

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2.1 Echinoderms

Basic body plan: pentaradial symmetry endoskeleton of spine-bearing ossicles water-vascular system

Five or six classes with very diverse forms.Which are these?

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2.2 Arthropods

Basic body plan:

Chitinous exoskeleton Segmented body Jointed appendages (1 pair per segment)

Four major extant subgroups (subphyla) withvery diverse forms between and among them.

Which are these?

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1. Subphylum Chelicerata(spiders, scorpions, ticks, mites, horseshoe crabs)

2. Subphylum Crustacea(crabs, krill, barnacles, wood lice, brine shrimp)

3. Subphylum Myriapoda(centipedes, millipedes)

4. Subphylum Hexapoda(insects)

Phylum Arthropoda

Arthropod refresher and dissection practical13


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2.3 Tetrapods

Colonisation of land(aquatic environment! terrestrial

environment)

Aquatic environment Dense watery medium

Terrestrial environment Less dense medium than water

Greater need to support bodyweight

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Amphibians -- first vertebrate group to becometerrestrial

Key modifications -- two pairs of strong, jointed limbsknown as pentadactyl (5 digits) limbs for support onland

Known as tetrapods (4 limbs)

Amphibians are the first tetrapods

Others: reptiles, birds, mammals

2.3 Tetrapods (contd)

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The earliesttetrapods radiated

from the

Sarcopterygii(lobe-finned fishes),into air-breathingamphibians in the

Devonian period.

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Devonian Period?Geologic Time Scale

Eon - Era - Period - Epoch

Eon: Phanerozoic Era: Palaeozoic Period: Devonian (354-417 MYA)

Epoch Upper/Middle/Lower (rocks) Late/Middle/Early (time)

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Geology.com

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The earliesttetrapods radiated

from the

Sarcopterygii(lobe-finned fishes),into air-breathingamphibians in the

Devonian period.

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Did fish crawl on to land(e.g. mudskippers),i.e. fish excursions

or did tetrapods evolvefrom shallow water habitats

(e.g. swamps),

i.e. shallow waterexploitation

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2004

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http://en.wikipedia.org/wiki/Image:Fishapods.jpg

muddy shallows

could goonto land

in weed-filledswamps; feetwith eight digits

with limbs

pelagic lobe-finned fish

pelagic lobe-finned fish

(extant)

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http://en.wikipedia.org/wiki/Image:Fishapods.jpghttp://en.wikipedia.org/wiki/Image:Fishapods.jpg


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How did fins evolve into feet?

Jennifer Clack

Who did the first push ups?Boris?

http://www.msnbc.msn.com/id/4638587/

discovery of theworlds oldest

known arm bone

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http://www.msnbc.msn.com/id/4638587/http://www.msnbc.msn.com/id/4638587/


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Clack said the fossils bizarreshape does not fit thepatterns of other early

tetrapods. She believes thatthere were a variety of limbshapes, sizes and strengths

among early tetrapodsexperimenting with

adaptations for life on land.- Apr 2004

Acanthostega gunnari

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http://tolweb.org/tree?group=Acanthostega&contgroup=Terrestrial_Vertebrates

Its structure supports the idea that limbs with digits evolvedfor use in water, only later to be used on land, rather than the

more conventional view that it was among sarcopterygian

fishes that excursions over land first began -Jennifer A. Clack26
http://tolweb.org/tree?group=Acanthostega&contgroup=Terrestrial_Vertebrateshttp://tolweb.org/tree?group=Acanthostega&contgroup=Terrestrial_Vertebrates


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Plants with stems, roots and leaves colonized

shallow rivers and changed the nature of manyaquatic environments and nearby shores.

Plants grew thick in streams and rivers, their roots

stabilized ecosystems, and their decomposingbiomass generated organic muck.

Plant-clogged waterways made weight-bearing fins,

and eventually limbs, useful for getting around.

What gases do plants produce?

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Grays anatomy

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Basic plan of

Pentadactyl Limb29


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Courtesy of Jerry Crimson Mann, http://en.wikipedia.org/wiki/Image:Evolution_pl.png

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http://en.wikipedia.org/wiki/Image:Evolution_pl.pnghttp://en.wikipedia.org/wiki/Image:Evolution_pl.png


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Pentadactyl

limb -Homology

Based on a drawing by Wilhelm Lechehttp://wiki.cotch.net/index.php/

Image:ForelimbHomology_unlabelled.png

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http://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.pnghttp://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.pnghttp://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.pnghttp://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.pnghttp://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.pnghttp://wiki.cotch.net/index.php/Image:ForelimbHomology_unlabelled.png


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Forelimbs of mammalshttp://en.wikipedia.org/wiki/Image:Handskelett_MK1888.png

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Why five?

Eight (or Fewer) Little Piggies Why do we and most other tetrapods have five

digits on each limb?

By Stephen Jay Gould, 1991.

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3 Constraints on size


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3. Constraints on size

and shape of animals Various forms and body plans of animals are the

result of evolutionary adaptations over longperiods of time (geological time scale)

Possibilities are finite

Constraints on size/shape by physical laws andenvironmental factors

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3 Constraints on size


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! 3.1 Hydrodynamics

! 3.2 Aerodynamics and gravity! 3.3 Exchange of materials with environment

! 3.4 Small, simple organisms high surfacearea:volume ratio

! 3.5 Larger animals low surface area:volume ratio

3. Constraints on size

and shape of animals

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3.1 Hydrodynamics

Streamlined shape of fast-swimming animals:fusiform shape.

Convergence across different groups: fishes, birds,mammals, and reptiles. E.g. tuna and dolphin.

Convergence: Diverse organisms face sameenvironmental challenge: water resistance;buoyancy.

Biomimetics.

3. Physical laws constraints on animal forms

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Example: swimming - cuttlefish fish


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Example: swimming cuttlefish , fish

Cuttlefish -jet propulsion. Rigid

internal shell (cuttlebone)prevents bending of body.

Fish - muscular contractions of body.Permitted by flexible internal skeleton

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Thunniforml i


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Two groups of dominant

open-ocean predators, thelamnid sharks and thetunas, even when looked

at superficially, displayremarkably similar

morphologicalspecializations related tolocomotion.

Donley et. al., 2004. Convergentevolution in mechanical design of

lamnid sharks and tunas. Nature,429: 61-65; 06 May 2004).

locomotion

All the lateral movement is inthe tail and peduncle.

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3 Physical laws constraints on animal forms


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3.2 Aerodynamics andgravity

Development of wings inflying animals

Convergence acrossdifferent groups: insects,fishes, birds, mammals, andreptiles

Certain degree ofuniformity within groups aswell

Same environmentalchallenges: air resistance;gravity


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3 Physical laws constraints on animal forms


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3.3 Exchange of materials with environment

Influenced by animal size and shape - constraints on animal form

Involves diffusion/transport of dissolved substancesacross plasma membrane of cells (e.g. gaseousexchange; metabolic waste removal)


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3.4 Small, simple organisms

high surface area: volume ratio

Protozoans (e.g., amoeba) plasma membrane withsufficient surface area

Cnidarians (hydra, jellyfish,coral) two cell layers Platyhelminthes (flatworms)

flat, thin body

All cells have direct access toenvironment

Limited complexity andorganisation

y

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C b if


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Carboniferous

300 MYA -Meganeura! Dragonflies: wingspan > 75cm

How did prehistoric insects overcome thelimitation of a tracheal system?

Polar gigantism -maximum potential size

is probably limited by

oxygen availability

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Oxygen limits on size


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Oxygen limits on size As an insect gets bigger, the proportion of its body

dedicated to breathing increases rapidly.

Trachea in larger beetles took up about 20% moreroom than smaller beetles.

Current oxygen limits the size of beetles to about 6inches.

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3.5 Larger animals low surface area: volume ratio

All cells must still have direct access to aqueous medium/environment

Extensive folding/branching increase surface area internally. E.g.,

Intestinal villi (finger-like projections); lungs or gills

Circulatory system

Young, 1981

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E.g. scaling relationships:

Limb length : Body mass= 0.33 Resting Metabolic Rate : Body mass =

0.66 - 0.80

[Lifespan : body mass= > 0.15] (heartbeats: 1-2bn) or quarter powerscaling, 1.e. 100 times body mass; lives 100^1/4= 3.2x longer

Scaling is the structural and functional consequences of a change in sizeand scale among similarly organized animals.

Various animal functions are not proportional to animal size; there areconsequences to increased size - e.g. the ability of a leg (cylinder) to

support increasing weight, diffuse oxygen, this also affects even ecologyand behaviour.

Limits placed on structural support, amount of gut surface arearequired to process the required energy per day, and cost of

locomotion become limiting factors for large animals

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4 Basic Designs


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4. Basic Designs

Some basic shapes and configurationsexist in nature:4.1 Sphere

4.2 Cylinder4.3 Spirals

4.4 Angles

4.5 Radials

These are manifested in the forms andstructures of animals.

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4.1 Sphere


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pLeast possible surface area for a

given volumee.g. eggs, small aquatic animals

Most spherical forms occur inwater since forces are equal

all round the animal

Fish eggs

Sea urchin

Frog eggs

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4.1 Sphere (contd)


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Hedgehog

Pill millipede

Compactness - easier tobe carried (e.g., eggs)

Least opportunity forpredator to break and

enter (many animals rollthemselves into a ball fordefence)

! ! no edge difficult to bitesmall portions

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4.1 Sphere (contd)


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4 2 Cylinder (tube)


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4.2 Cylinder (tube)

E.g., sea anemone. E.g., elephant trunk; butterfly proboscis.

flexibility improves versatility.

Rigid or flexible

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Movement throughCredit: Ken Lucas/Visuals Unlimited

Round worm4.2 Cylinder (tube)

Credit: Ken Lucas/Visuals UnlimitedRound worm


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Damselfly

Tube worms

Tube worm

blood vessels

Movement throughsmall spaces(burrowing)(worms, caecilians,millipedes)

Ideal for transport(blood vessels, bivalvesiphons, proboscis)

Greater strengthcompared to solidcylinders of equallength and weight(birds bones)

Credit: Tom Adams/Visuals UnlimitedCaecilian

Bivalve siphons

Damselfly

Tube worms

Tube worm

blood vessels

Credit: Tom Adams/Visuals UnlimitedCaecilian

Bivalve siphons

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http://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpg

cylindrical bodies covered in fur
http://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpghttp://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpghttp://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpghttp://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpghttp://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpghttp://en.wikipedia.org/wiki/Image:Close-up_of_mole.jpg


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4 3 S i l


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Economy of space -- able to pack large surface areainto least volume

Strong, flexible, extendable Different types of spirals:

Archimedes spiral

Helix Equiangular spiral

4.3 Spirals

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4.3 Spirals (contd)


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Archimedes spiral -extends

outwards from a central point incoils of equal width

Butterfly proboscistucked in a neat spiral

when not feeding.

Distal arms of octopus curlup in a simple spiral at rest.

Spider webs demonstratesimple spiral design.

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4.3 Spirals (contd)


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Skeleton of theVenus flower basket

sponge

Helix - 3D spiral with constant

diameter of curve and constant distance

between coils, i.e., each loop is identical

DNA molecule isarranged as adouble helix

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4.3 Spirals (contd)


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Nautilus

Many animals overall shape and body proportionschange as they grow

Equiangular spiral allows retention of same shape, i.e.,size of the shell increases but the shape is unaltered(e.g. sea shells)

Equiangular spiral - radius of each curve increases

at a constant rate in proportion to the last one

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4.3 Spirals (contd)


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! Does the body/tissue of a snail coil round the shellcolumn and extend all the way to the apex or doesit extend just part of the way?

! Vacuum at the apex of most gastropods (snails) withspirally coiled shells

! Exception: in some snails with more depressed shells,e.g., nerites, the body extends all the way to the apex! Different in nautiluses, which are cephalopods, not

gastropods

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Spirals in use


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Spirals in usecompact fluorescent light

A way to pack a long tube (with a lot of surface area) into thespace of a regular bulb: visible light is produced by the

phosphor coating on the inner surface of the tube

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4 4 Angles


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4.4 Angles

In nature, economy is crucial Using least amount of materials = energy

saving

Therefore, curves are preferred to right-angled forms

Spheres, for example, represent least surfacearea to a given volume

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Honeycombe Conjecture


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Honeycombe Conjecture

Honeycomb design - beauty or efficiency?

Pappus, 4th century Greek mathematiciancommented on the sagacity of bees

Darwin - " the comb of the hive-bee, as far aswe can see, is absolutely perfect ineconomizing labor and wax."

Least amount of wax? Thomas Hales (mathematician), U. Michigan

proved the honeycomb conjecture in 1999

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Pinhead silver ofwarm wax excreted.

Photo byP.O.

Gustafson


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warm wax excreted.

Vertical six-sidedcylindrical chambers.

Partitions < 0.1mm+/- 0.02mm

120 degrees, perfecthexagon

Why not square,triangle or circle?

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The closed ends of the honeycomb cellsare an example of geometric efficiency:

the ends are trihedral pyramidal in shape,with the dihedral angles of all adjacent

surfaces measuring 120.

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Least perimeter

Hexagonal tiling represents the best possible way to


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g g p p ydivide a surface into regions of equal area with theleast

perimeter: each wall serves two tube(avoids wasteful duplication)

Maximum strength

Wax cell walls 0.05mm thick can support25 times its own weight.

Less wax

Triangular and square tubes can also share all walls,but hexagonal tubes use less wax:18% less than triangular tubes, and

7% less than square tubes.

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Hexagons fill space more economically than circles

120 angle (3-way junction) is the most economicalangle for joining things together. Occurs throughoutthe animal world.

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5. Summary


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" Economy of space is important in the animal

world.

" This is seen in their form and structure.

"Wastage of materialshas to be minimised inorder to avoidunnecessary loss of

valuable energy.

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! A shape is most efficient when it reduces work orwastage of resources by the animal to a minimum.


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! Form and structure are perfectly matched to a specific

task.! Evolutionary pressures constantly at work to select

animal species with adaptations that suit them best forsurvival in a particular environment.

! Adaptations consistently improve a speciessurvivability.

! An animals structure imposes certain designconstraints.

! Different animal groups adopt different methods ofsolving the same problem.

! There is a logic in design.

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Biomemetics


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Biomemetics

The application of biological methods andsystems found in nature to the study anddesign of engineering systems and moderntechnology.

Biomimicry- examining nature, itsmodels, systems, processes and elements to

emulate and take inspiration to solve humanproblems

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Examples?


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p

Velcro

Cat-eye

Resilin

Morphing aircraft wing

Nano-hair medicaladhesives

Computer viruses?

Cool termite mounds

Batcane (now Ultracane)

Mussel glue

etc

Natures 100 Best(webpage)

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*Vaccines that survive without refrigeration based on Africas

From Natures 100 best


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Vaccines that survive without refrigeration based on Africa sresurrection plant.

* Friction-free surfaces suitable for modern electrical devices gleanedfrom the slippery skin of the Arabian Peninsulas sandfish lizard;

* New anti-bacterial substances inspired by marine algae found offAustralias coast that promise a new way of defeating healthhazardous bugs without contributing to the threat of increasing

bacterial resistance;

* Toxic-free fire retardants, based on waste citrus and grape cropsinspired by the way animal cells turn food into energy withoutproducing flamesthe so-called citric acid or Krebs cycle;

* A pioneering water-harvesting system to recycle steam from cooling

towers and allowing buildings to collect their own water suppliesfrom the air inspired by the way the Namib Desert beetle of Namibiaharvests water from desert fogs; and

* Biodegradable, water-tight packaging and water-repellant linings forpipes to tents that mimic the Australian water-holding frog.

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lsm3261_lecture 8 --- animal diversity and basic designs

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