LSM3261_Lecture 9 --- Animal Symmetry and ion

8/3/2019 LSM3261_Lecture 9 --- Animal Symmetry and ion

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LSM3261 Life Form and FunctionAnimal structure and function

LSM3261 Lectures 08 - 13= Zoology Lectures 1 - 6

LSM3261 Practicals 4 - 6

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Practicals and CA

Practical 4

Body plans and Protection

Arthropod morphology (dissection)

Dissection assessment (2.5%)

Practical 5

Form and function in vertebrates

Setting thinking questions (2.5%)

Practical 6

Support

Practical test based on practicals (15%)

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Not possible to cover the entire range of animal formand function.

Certain aspects are highlighted to initiate a thinkingprocess.

An emphasis on structure and function - i.e.we will focus on structural adaptations and less onbehavioural or physiological ones.

Thematic approach will focus on specific topics.

Course approach

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Plants & Animalsface similar challenges to survival

Gas exchange: Stomata/lenticels in plants Respiratory systems in animals

Internal transport: Vascular system (phloem, xylem, leaf

veins) in plants

Circulatory system in animals

Osmoregulation

Active transport (cellular level) inboth plants and animals

Salt secretion in both plants andanimals

Protection: Epidermis, cuticle, hairs, spines in

plants

Epidermis, exoskeleton, scales, spinesin animals

Common physical and environmental challenges result in similarities inform and function.

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Lecture Number - Topic

08 - Animal diversity and basic designs 09 - Animal symmetry, arthropod morphology

Animal form and function in relation to: 10 - Protection 11 - Support & Locomotion

12 - Locomotion (Flight)

13 - Sensing the environment, Feeding 13 - Other adaptations

Topics for the animal component

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Biology education

Expand your initial introduction to biodiversity (LSM 1103). Explorezoology!

Appreciate a holistic approach to understanding life.

To understand the structure of animals and how they are designed forspecific tasks.

To understand how adaptation facilitates survival.

To appreciate the diversity of structural adaptations displayed bydifferent groups of animals in response to a common problem.

Whats the point of it all?

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General education

Appreciate structure, detect patterns and deducefunction.

Application, analysis, synthesis and judgment.

Other skills and tools, e.g. illustrating ideas,communicating science (especially during thepracticals and the CA).

Life lessons and food for thought.

Dealing with a less structured system.

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Questions from

an active mind Why dont elephants choke when they suck water upthrough their nose (trunk).

Why cant a flying fish fly for long distances?

Why has a sea cucumber become bilaterally symmetricalwhen it started out with radial symmetry?

Isnt it dangerous for cuttlefish to be swimmingbackwards?

Why doesnt the long proboscis of the butterflyinterfere with its flight?

Please ask stupid questions!

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Questions from a lazy mind

What is bilateral symmetry?

How many toes are there in a leg of a horse? What is the mouth part of a butterfly called?

During practicals, we will consult booksand the internet together

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How to do well in this moduleand gain from it

Be curious, inquisitive and observant. Be an active learner - do not ask questions that can be

obtained directly from a text book. Read widely, watch nature documentaries. Dont waste tim on the details.

Essential to understand general concepts so that youcan apply them. Explore with Google and NUS Digital Library.

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http://delicious.com/sivasothi/lsm3261

This is listed under weblinks inIVLE.

It allows you see the additionalreferences I look at whilepreparing lectures.

Check the tags (lsm3261,

locomotion, etc)

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http://del.icio.us/sivasothi/lsm3261http://del.icio.us/sivasothi/lsm3261http://del.icio.us/sivasothi/lsm3261


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This year we will use a a

Facebook page - easier for

most of you to follow than amodule blog.

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Predicting form

Form and function are closely related. E.g. long extended proboscis of hawk moth (form) for feeding on

nectar in deep tube-shaped flowers (function)

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

Obtaining oxygen

Obtaining food Excreting waste

Movement

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Hummingbird hawk moth

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Illustration by John Day; Orchids of the Worldhttp://www.orchids.mu/Species/Angraecum/Angraecum_sesquipedale.htm

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http://www.orchids.mu/Species/Angraecum/Angraecum_sesquipedale.htmhttp://www.orchids.mu/Species/Angraecum/Angraecum_sesquipedale.htm


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The moth ofA. sesquipetale predicted:

Charles Darwin: "[A. sesquipetale has] nectaries11 and a half inches long, with only the lower inchand a half filled with very sweet nectar [...]

it is, however, surprising, that any insect should beable to reach the nectar: our English sphinxes haveprobosces as long as their bodies;

but in Madagascar there must be moths withprobosces capable of extension to a length ofbetween 10 and 12 inches!"

Darwin, 1862. Fertilisation of Orchids, pp. 197-198)

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Th h f A ip l di d


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The moth ofA. sesquipetale predicted:

Alfred Russel Wallacepublished a drawing of what thisbutterfly might look like, concurring with his colleague and added:

"[The proboscis of a hawkmoth] from tropical Africa ([Xanthopan]morganii) is seven inches and a half.

A species having a proboscis two or three inches longer couldreach the nectar in the largest flowers ofAngrcum sesquipedale,whose nectaries vary in length from ten to fourteen inches.

That such a moth exists in Madagascar may be safely predicted,and naturalists who visit that island should search for it with as

much confidence as astronomers searched for the planetNeptune, and they will be equally successful!"

Wallace, 1867. Creation by Law.

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The moth ofA. sesquipetale

predicted:

Nature, 12 June 1873

W. A. Forbes challengedreaders, Can any of your

readers tell me whether mothsof such a size are known toinhabit Madagascar?"

Rotschild & Jordan, 1903

Moth described.

Image Source: KQED QUESTSome rights reserved.

Xanthopan morganii praedicta

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http://www.flickr.com/photos/kqedquest/http://www.flickr.com/photos/kqedquest/


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LSM3261 Life Form and Function

Zoology Lecture 2Animal symmetry,internal transmission

and arthropod structure

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LSM 3261 Lif F S & F i


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LSM 3261 Life Form Structure & Function

1st zoology lecture - Animal diversity and basic designs

2nd zoology Lecture Animal symmetry; Transmission of messages/materials within the

animal body

Arthropod structure (practical) Animal form and function in relation to:

No. 3 - Protection

No. 4 - Support & Locomotion No. 5 - Locomotion (Flight) No. 6 - Sensing the environment, Feeding and

other adaptations

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1. Types of animal

symmetry1. Bilateral

2. Radial

3. Pentaradial

4. Metamerism (segmentation)

4.1 Tagmatisation

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BILATERAL SYMMETRY RADIAL SYMMETRY

Can be cut into

two equal lateral halvesalong one (saggital) plane only

Can be cut longitudinally into two

equal halves along more than oneplane through axis of body

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1.1 RADIAL SYMMETRY


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Advantages of radiating configuration

Distance between centre andoutlying points reduced(faster transportation of materials,signals)

Increased surface area

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Is there a solutionto this problem?

Disadvantage

Too many points converging at the

centre causing over-crowding

Solution: Branching

- Maintain radial configuration andsurface area

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Are there radially symmetrical animals thatwhich are branched this reducing

congestion at the centre?

Is there branching in humans?

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1.2 PENTARADIALSYMMETRY

(Echinoderms)Radial symmetry basedon 5 parts or planes

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2 3

4

5

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Why pentaradial symmetry?


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Pentaradialsymmetry: five

ossicles

Suture planes

Hexaradialsymmetry: six

ossicles

One theory:

Skeleton in primitive echinoderms(radially symmetrical sessile,suspension feeders)

Suture planes: structural weakpoints

Advantageous to NOT have twosuture planes directly opposite

Odd number of surrounding ossicles

But why 5 parts?

Why not 7 or 9 parts?

Why not 3 parts?

Why pentaradial symmetry?

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Bilaterally Symmetrical Animals

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B l l d h


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Fast-moving animals:

Are they radially or bilaterally symmetrical?

Bilateral symmetry associated with: General lengthening of body.

Cephalisation increasing specialisation of anterior endof animal with concentration of sensory structures (i.e.development of a well-defined head!).

Bilateral symmetry and cephalisation

Adaptations for locomotion; associated with increasedeffectiveness of reacting to environment (e.g. find food,detect enemies).

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Radial symmetry

ADV: Defend in all directions!

Slow, nerve net not centrallycontrolled.

Bilateral symmetry

Move faster (advantage foirdirected locomotion),

predation, cephalisation, etc.

Advantages?

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Radial symmetry Bilateral symmetry


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y y

Vast majority sessile - anchored to thesubstrate.

All lateral surfaces equally likely to

interacting with the environmentmeaningfully; oral/aboral

Top and bottom of the organismhave very different functions.

Lower surfaces often modified for astable, concrete point of attachmentto some solid surface.

Upper surfaces modified for thegathering of resources (usually food).

Lateral organization is relativelyunimportantVertical organization is meaningful, Symmetry around the central vertical

axis becomes the most useful body

plan.

y y

An adaptation to a moving, directionalexistence.

Up and down, left and right, top and

bottom, front and back.

Anterior portion encounters theenvironment first.

Differentiation of sense organs(cephalization) in the anterioreventually becomes significant

Locomotion by providing a propulsiveforce against air or water or thesurface of the earth

Can wegeneralise?

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Barnacles


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Not all sessileanimals

are radially symmetrical

Sea squirt or Tunicate

Giant clams

Sea pen

Barnacles

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Not all radiallysymmetrical animals

are sessile

Feather star

Brittle star Jellyfish

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BILATERAL


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BILATERALSYMMETRY?

PENTARADIAL OR BILATERAL SYMMETRY?

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Asymmetry in the Pleuronectiformes


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Asymmetry in the Pleuronectiformes

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This process involves extensive remodeling of the skull.

Bones soften and degenerate,epithelial and connective tissue thickens

and pushes the eye socket around,and just in general many bones,

including those of the jaw,end up oddly skewed.

Larval metamorphosis

Later stages:calcification

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BILATERAL OR RADIAL SYMMETRY?

White-spotted puffer,Arothron hispidus

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Unequal bilateral symmetry

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The Ups and Downs of a Sea Anemone


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The Ups and Downs of a Sea Anemone

Most animals are in theBilateria.

Sea anemones - radialsymmetry.

The starlet sea anemone,Nematostella vectensis.

Burrows through mud! John Finnerty

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the starlet sea anemone


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the starlet sea anemone,Nematostella vectensis

A cross section of the adult shows not radialsymmetry, as dogma would predict, but a plane

of bilateral symmetry (known as the "directiveaxis") that traverses the pharynx at right anglesto the primary oral-aboral (mouth-foot) bodyaxis.

"Enhanced: The Ups and Downs of a Sea Anemone,"by Peter Holland. Science, 304 (5675): 1255 - 1256.

Commenting on Finnerty et al., 2004.Origins of Bilateral Symmetry: Hox and Dpp

Expression in a Sea Anemone. Science, 304(5675): 1335.

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Anthozoan bilaterals

The bilateral symmetry of anthozoans (andnot other cnidarians) was noted by Hyman(1940).

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Origins of bilateral


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If sea anemones possess bilateral symmetry,is it homologous to our own bilateral

symmetry or did it arise by convergentevolution?

I. e. ... did bilateral symmetry originate earlierin our ancestry than is commonly believed or

did anthozoans evolve from a radial ancestorand develop bilaterality independently?

Origins of bilateral

symmetry

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Comparison of gene expression patterns

data suggests that

the main oral-aboral body axis

of a sea anemone, running frommouth to foot, is homologousto the anterior-posterior axisof bilaterians,

whereas a precursor of thedorsoventral axis runs throughthe directive axis.

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Nematostella has perfectly good Hox genes that are expressed in astaggered anterior-posterior pattern. It's not quite as tidy as the

vertebrate or athropod patternthere's a lot of overlap, as you canseebut it's good enough to see the canonical Hox arrangement.

PZ Myers commenting on the paper (2006); this and previous slides.

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Boloceroides mcmurrichioff Changi


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Boloceroides swims up, down, or horizontallyapparently equally well. Often it swims in anearly straight line, but sometimes theswimming course is rather erratic.

The tentacles apparently beat in planeswhich are slightly inclined to the oral-aboralaxis, for the anemone usually rotates aboutits longitudinal axis as it swims, making acomplete revolution every 6-20 strokes.

This rotation probably stabilizes swimmingto some extent. ...

See Video and additional text here:

http://tinyurl.com/2cq46n

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Boloceroides mcmurrichioff Changi
http://tinyurl.com/2cq46nhttp://tinyurl.com/2cq46n


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During swimming the tentacles arefunctionally organized as a series ofconcentric rings on the oral disk.

During the downstroke portion of the cycle,the most lateral tentacles, the smallest of thecrown, are the first to beat.

The inner tiers follow in a regular fashionwith a brief delay before the onset of lashingin each. The tentacles near the mouth are thelast to respond."

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During swimming the tentacles are


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g gfunctionally organized as a series ofconcentric rings on the oral disk.

During the downstroke portion of the cycle,the most lateral tentacles, the smallest of thecrown, are the first to beat.

The inner tiers follow in a regular fashionwith a brief delay before the onset of lashing

in each. The tentacles near the mouth are thelast to respond."- Josephson, R. K. & S. C. March, 1966. The

Swimming Performance of the Sea-Anemone Boloceroides. Journal of

Experimental Biology, 44: 493-506.

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1 4 Metamerism (Segmentation)


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Repetition of similar body segments along longitudinal axis of body

Allows for specialisation.

External and internal segmentation

Each segment referred to as ametamere or somite

Clearly represented insegmented worms (annelids) segments separated by internal

walls (septa).

Organs repeat themselves (e.g.excretion). Some are notrepeated (e.g. digestive).

1.4. Metamerism (Segmentation)

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Ad f i


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Advantage of metamerism

Hydrostatic skeleton improves - efficiency ofmovement/burrowing efficiency improves.

Elongate different parts of body at differenttimes - better control of movements.

Safety factor of built in redundancy.

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C t th i h lf


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Cut an earthworm in half

What happens? Why?

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Metamerism,segmentation and tagma

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Segment - clearly differentiatedsubdivision of an animals body

Metamere - homologous segment inlongtitudinal series; copies

Tagma? (pl. - tagamata) -arthropodan divisions,e.g. spider cephalothorax and opsithosoma;crab: cephalothorax and abdomen.

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By the way....


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2005 - New species Glyphidrilus singaporensis

Four new records - Glyphidrilus horstiStephenson, 1930,

Amynthas gracilis (Kinberg, 1866),

Amynthas minimus (Horst, 1893), and

Polypheretima taprobanae (Beddard, 1892)

Three unidentifiable Drawida species

Total of 19 species of terrestrial earthworms that arenow known from the island.

Most dominant species - the exotic Pontoscolexcorethrurus (Mller, 1856)

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1.4.1 Tagmatisation


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Tagmatisation -- grouping/fusion of segments of similarstructure, function and appendages to allow

specialisation

Most obvious e.g.: cephalisation Other examples:

head, thorax, abdomen (insects) cephalothorax, abdomen (chelicerates, some

crustaceans)

clitellum (some annelids)

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Evolved three times?


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Annelida

external segmentation marked; muscles segmented;

segmentally arranged ganglia.

Arthropoda

segments more specialised for a variety ofpurposes, forming functional groups (tagmata).

head/trunk; head, thorax, abdomen; cephalothorax,abdomen

Chordata if present, restricted to outer body wall.

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2 T i i f d


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2. Transmission of messages and

materials within the animal body

Nervous system

Internal transport

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2.1 Nervous system


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Transmission of information throughout animalsbody vital for survival maintenance of internalenvironment (homeostasis)

Animal must respond rapidly to external andinternal changes (stimuli that trigger response) All animals except sponges have at least a network

of nerve cells (neurons) that respond to stimuli

Neurons transmit electrical and chemical signals

y

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cerebral

Crustacean


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Flatworm

cerebral

ganglia

(simple

brain)

longitudinal

nerve cords

with

transverse

nerves

Hydra nerve net,suitable for radially

symmetrical animals

Bilaterallysymmetricalanimals have

more complexnervoussystems

AnnelidInsect

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Messages received have to be transmitted, analysed, and a


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g , y ,suitable response elicited:

RECEPTION detecting a stimulus (by neurons and

specialised sense organs)

TRANSMISSION sending messages along a neuron, to

other neurons and/or to muscle or gland

INTEGRATION messages sorted and interpreted,

appropriate response determined

RESPONSE appropriate response effected

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Neurons highly specialised cells designed to receive


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stimuli, and produce and transmit electrical signals (nerveimpulses or action potentials)

nucleus

axon

dendrite

myelin sheath

terminal branches(gap betweenbranch and next

neuron = synapse)E.g., motor neuron

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Synapse betweensensory and interneuron

Reception

Transmission


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Receptor

Sensory neuron

Nerve cell body

of sensory neuron

sensory and interneuron

Interneuron

Nerve cell bodyof motor neuron

Muscle

Reflex action coordinated, involuntaryresponse to stimulus

Integration

Response

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Trends in evolution of


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Increased number of nerve cells

Concentration of nerve cells into ganglia, brain,nerve cord, nerves

Specialisation of function (afferent, efferent)

Cephalisation (formation of head)

Increased complexity

the nervous system

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Trends in evolution of


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To survive, animals have to respond to changes in theirinternal and external environment.

Simple nervous system - general responses only (can onlyprocess information in a limited way_, e.g. the commonfreshwater Hydra.

Hydra has a nerve net of neurons between the outerand inner layers of a sac-like body.

The nerve net transmits impulses in all directions withno means of processing the information to make aspecific response.

the nervous system

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Flatworms (e g planaria) i l t li d


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Flatworms (e.g. planaria) - simple centralizednervous system.

Neurons organized into ganglia which receive stimulifrom the sensory structures and transmit them by wayof a ladder-like arrangement of nerves to muscle cells.

This makes specific responses to stimuli possible, e.g.turning away from light, or curling up when touched.

Higher invertebrates (e.g. annelids, arthropods, andmolluscs) - more complex nervous system, more highlydeveloped sensory structures.

This allows the animals to receive, process, andrespond to stimuli in a greater variety of ways.

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E d f i t d i f ti


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E.g. compound eyes of insects: send sensory informationthrough nerve fibers to the ganglia in the head that serve

as the brain.

Information relayed to the other parts of the bodythrough the ventral nerve cord.

E.g. rapid escape response of flies when you try toswat.

E.g. Octopus,

Well developed eyes and a central concentration ofnerve cells.

Responses are highly specific, and it has the ability tolearn how to perform complex tasks.

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2.2 Internal transport


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A cell requires:

a continuous supply of nutrients, oxygen

removal of waste products Mainly through diffusion across cell

membrane

Cells bathed in interstitial fluid (aqueousmedium between cells for diffusion ofoxygen, nutrients, waste materials)

p

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Circulatory System


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Diffusion effective across short distances feasible for internal transport in small, simple invertebrates

(e.g., sponges, cnidarians, flatworms)

Larger animals require specialised circulatory systems

Transport oxygen, nutrients, hormones, metabolic wastes toand from interstitial fluid

A circulatory system reduces diffusion distance of materials

interacts with all organ systems (and constituent tissues andcells) in the body

Circulatory System

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CIRCULATORY SYSTEM


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Blood - connective tissue containing cells &cell fragments in fluid (plasma)

Pumping organ (usually a heart) System of tubes (blood vessels) or spaces

through which blood flows

C CU O S S

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INVERTEBRATES


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INVERTEBRATES

No circulatory system

Open circulatory system

Closed circulatory system

VERTEBRATES

Closed circulatory system

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NO CIRCULATORY SYSTEM

Small aquatic invertebrates:

Flatworms


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Small, aquatic invertebrates:

Flattened, not more thanfew layers of cells thick

Branched intestine circulates nutrients/oxygento all cells

SpongesCnidarians73


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OPEN CIRCULATORY SYSTEM- Pumping mechanism presentBlood vessels not continuous throughout body blood flowsinto large spaces or sinuses (haemocoel)

- Blood bathes tissues directly- Blood and interstitial fluid not distinguishable (haemolymph)

Haemolymph returns directly to heart:- through openings in heart (arthropopds)

- through open-ended vessels leading to gills (molluscs)

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Stomach

Ventricle

Atrium


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Gills

Artery Ostia Tubular heart

OPEN CIRCULATORY SYSTEM

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CLOSED CIRCULATORY SYSTEM

- Continuous circuit of blood vessels- Smallest blood vessels (capillaries): sufficiently thin walls toallow diffusion of materials

-Tissues not directly bathed by blood

-Blood pumped through system by muscular heart or bodymuscles

- Annelids, cephalopods, echinoderms, vertebrates-

Network based on a main blood vessel taking bloodto the entire body and another taking blood back to the heart

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CLOSED CIRCULATORY SYSTEM


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Dorsalvessel

Contractileblood vessels

Ventralvessel

Lateralvessels

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AtriumVeins from thebody


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SINGLE CIRCULATIONSYSTEM IN FISH

gills

heart

Ventricle

Aorta

Heart to gills to rest of body, back to

heart (2 chambered heart: oneventricle, one atrium)

Rest

ofbody

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AMPHIBIAN d bl i l


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AMPHIBIAN double circulatory system

Heart to lungs to heartHeart to body to heart

(3-chambered heart: two atria, one ventricle partialmixing of oxygenated and deoxygenated blood)

REPTILE double circulatory system

(3-chambered heart: two atria, one ventricle, partiallyseparated, minimal mixing of oxygenated and

deoxygenated blood cf. amphibian)

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DOUBLE CIRCULATIONSYSTEM IN AMPHIBIA Incomplete

partitionof theentricle

Reptile heart


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lungs

Veins fromthe body

Ventricle

Pulmonary vein Pulmonaryartery

Aorta

Partitionseparating atria

Atria

ventricle

Amphibian heart

Rest ofbody

3-chambered heart: twoatria, one ventricle, mixingof oxygenated and

deoxygenated blood

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DOUBLE CIRCULATION SYSTEM INBIRDS AND MAMMALS


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lungs

Veins fromthe body

Right atrium

Ventricles

Leftatrium

Pulmonaryartery

Aorta

4-chambered heart: two atria, twoventricles, no mixing of oxygenated and

deoxygenated blood

Rest ofbody

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Aorta

Left pulmonary arteries

Superior vena cava


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Right pulmonaryarteries

Pulmonary valve

Right atrium

Pulmonary veins

Right ventricle

Inferior vena cava

Pulmonary artery

Pulmonary veins

Left atrium

Left ventricle

Interventricular septum

Aorta

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LSM3261_Lecture 9 --- Animal Symmetry and ion

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