BIOL 111 – Part 2 (lect 10-21) C. Aikins

LECTURE 10: CNIDARIANS & PLATYHELMINTHES Lecture Outline • Embryonic development • Symmetry • Parasitism

Animal Characteristics 1. Eukaryotic 2. Heterotrophic 3. Multicellular 4. No cell walls 5. Motile at some life stage 6. Diplontic life cycle **most animals also have tissues **most undergo unique embryonic development pattern

Embryonic development • Zygote – diploid cell resulting from union of two haploid gametes (1st cell of 2nd generation) • Embryo – young animal or plant while it is still contained within a protective structure (e.g. seed coat, egg shell or uterus) • Two major processes occur during embryonic development o Cleavage – cell division . Process forming many cells from one cell o Gastrulation – in-folding . Process forming embryonic tissue layers (2-3) from one layer of cells • Zygote  (cleavage and more cleavage)  morula (solid ball)  blastula (hollow ball)  (gastrulation begins, making a blastopore) Gastrula Gastrula • An embryo at the stage following a blastula, when it is a hollow cup-shaped structure having 2-3 embryonic cell layers • These are called germ layers : o Ectoderm . outermost layer . develops into epidermis, nervous system o Endoderm . Inner lining of blastopore . Develops into the lining of the digestive and respiratory system o *** Organisms with 2 germ layers are diploblastic o Mesoderm . Inner lining . Develops into most internal organs: muscles, skeletal system, heart, o *** Organisms with 3 germ layers are triploblastic • Archenteron o Hollow space past blastopore o Develops into digestive space (gut cavity) • Blastopore o Develops into mouth or anus

Importance of more sophisticated embryonic development = ? • Make tissues o Enable body organization o Allows for more complex movement and activties • Makes Gut o Enables extracellular . Larger particles can now be digested

Types of Symmetry • Asymmetrical o No axis divides body into equal halves o Ex some • Radially symmetrical o Symmetry along a central axis o Ex cnidarians • Bilateral symmetry o Single axis divides body into equal halves . Typically means there is a head o Called the midsagittal plane (between eyes) o Ex platyhelminthes

PHYLUM • Jellyfish, sea anemones, corals, hydrozoans • ~11,000 species o mostle marine o microscopic to many meters o carnivorous (though they can have mutualistic relationship with algae) • diploblastic • nervous and muscular tissue simple body plan: • mouth/anus (from blastopore) • gastrovascular cavity (“blind gut” from archenteron) • gastrodermis (cell layer lining gut, from endodermis) • mesoglea (inner jelly) • epidermis (outer cell layer, from ectoderm) two body forms • poyp o sessile o ex (can awkwardly move base if necessary) • medusa o motile o oral side down o ex jellyfish • most lifecycles include both body plans How do Cnidarians obtain energy? • Carnivorous, using cnidocysts to capture prey, inject prey with venom & stick to prey o Cnidocyst fires our nematocysts • Extracellular digestion in gastrovascular cavity • Corals can obtain a large portion of their energy from symbiotic algae (which are photosynthetic) Nervous system • Very simple • Nerve net • Little to no integration or processing of signals • Provide direct lines of communication between sensors and effectors (muscles) Reproduction • Asexual reproduction o Budding • Sexual reproduction o Medusa release sperm and egg  planula larva  poyp Cnidarian Diversity • Class Hydrozoa o Polyp dominant phase, most species alternate between polyp and medusa o Eg Hydra • Class Scyphozoa o Medusa is dominant, polyp is reduced o Eg jellyfish • Class Anthozoa o “flower animal” o Polyp is dominant, no medusa o Eg corals and anenomes

CLASS Hydrozoa • Hydra o Freshwater o No medusa stage o Move by gliding, somersaulting or floating o 2-5mm • Portuguese man-of-war o Colonial polyps and medusas . Specialized cells for different functions . Gas-filled float . Tropical, subtropical oceans CLASS Scyphozoa • Jellyfish o Large amounts of mesoglea o Some nematocyts strong enough to be felt by humans o Prey on fish larvae and zooplankton o Important food for leatherback turtles o Eg Cassiopeia . “upside down jelly” . symbiotic algae in tentacles (need light)

. tolerates low O2 conditions, and gets O2 and nutrients from symbionts CLASS Anthozoa • Sea anemones o Retracts tentacles in defence o Mutualistic (+/+) relationships with fish and shrimp . Exude mucus that prevents nematocysts from firing, and are protected. Prevent other fish from eating anemones • Corals o Mutualistic relationship with zooxanthellae (a )

o Secrete CaCO3 exoskeleton = reefs o Coral bleaching . Serious recent ecological problem . zooxanthellae expelled (eventually coral will die) . due to a variety of factors  increasing water temperature  increasing UV radiation  pollution  disease (bacteria)

PHYLUM Platyhelminthes • “” • ~25,000 species • terrestrial (moist) or aquatic habitats • “free-living” (scavengers) or parasitic • 1mm to 10m • Tripoblastic • Move by cilia (at some stage in life) Body plan • Head o Eyespots with photoreceptors (know general direction of light) o Auricles – chemoreceptors “smell” • Highly branched digestive tract • Mouth on the back? • Bilateral symmetry Cephalization • The presenence of a head brings about cephalization • Concentration of neurons and sensory structures at the anterior end o Enables directed locomotion and behaviour o Senses encounter new environment first • Sensory structures o Mechanorecepors (touch) o Chemoreceptors (taste/smell) o Photoreceptors (light) Simple nervous system • Longitudinal nerve cords • Cerebral ganglion o Connection of nerves o “primitive brian” How do Platyhelminthes eat and breath? • Very high surface area/volume ratio • No respiratory system • No • Have and highly branched digestive cavity o Brings nutrients across body • Some have no digestive cavity or mouth! (eg parasite) Platyhelminthes diversity • Free living o Class Turbellaria • Parasitic (+/-) o Class Monogenea . mostly ectoparasitic, on the outside o Class Trematoda . Mostly endoparasitic, live within o Class Cestoda . Endoparasitic CLASS Turbellaria • Free-living, planarians • Tubular pharynx, halfway down body • Amazing ability to regenerate o Anterior end will always develop into a head • Reproduce asexually by fission and sexually (mostly hermaphroditic)

CLASS Monogenea • Ectoparasites • Flukes = flat body with suckers

CLASS Trematoda • Endoparasites • Flukes • Schistosomiasis o Disease rarely causes death but can damage internal organs and impair growth in children o Common in Asia, Africa and S. America o Life cycle 1. Mature flukes in blood vessels of human intestine 2. Blood flukes reproduce sexually in human host. Fertilized eggs exit host in feces 3. Eggs develop in water into ciliated larvae. Larvae infect snails – intermediate host (shorter transitional stage) 4. Asexual reproduction within snail results in another type of motile larvae 5. Larvae penetrate skin and blood vessels of humans – primary host (organism reaches maturity and sexual reproduction) cycle repeats

CLASS Cestoda • Endoparasites • Tapeworm • Habitat: intestines of • Host-specific (different species have different hosts) • Adaptation o Scolex – suckers, hooks o Proglottids – reproductive sections • No mouth, no digestive system • Protective cuticle forms around embryos & terminal proglottid breaks off, passed via feces

LECTURE 11: & Lecture outline • Embryonic development (Part 2) o Formation of digestive tract • body cavities • Body segmentation • Nematodes • Annelids

DIGESTIVE TRACT • Development of a digestive tract enables o Specialization of gut regions o Sequential food processing o Continuous operation . Continuous processing of food • Development o Protostomes . “first is mouth” . Blastopore  mouth . New opening  anus o Deutrostomes . “second is mouth” . blastopore  anus . new opening  mouth

PROTOSTOME ANIMALS • Lophotrochozoans o Have one of the following characteristics (some may have lost it secondarily, or it only developed in some of the groups) o Lophophore – ciliated feeding/gas exchange structure o Trocophore - a ciliated free-living larval form o We’ll be looking at Flatworms, Annelids and Mollusks • Ecdysozoans o Have an external covering secreted by epidermis that must be shed in order to grow o We’ll be looking at nematodes, and

BODY CAVITIES • Another major difference among protostomes is the presence and type of body cavity • There are three different body plans with regard to body cavities • Coelom = cavity (greek root) • Acoelomate o No coelom o Solid except digestive space o Have ectoderm  muscle layer (mesoderm)  Mesenchyme (unspecialized cells derived from mesoderm)  gut (endoderm) • Pseudocoelomate o “false coelom” o mesoderm lines the outside of the coelom . does not completely line cavity, doesn’t wrap gut o have ectoderm  muscle layer (mesoderm)  pseudocoel (cavity)  internal organs/gut • Coelomate o Mesoderm lines the entire cavity as a “peritoneum” . Lining derived from mesoderm o Ectoderm  muscle (mesoderm)  peritoneum (mesoderm) completely wrapping  internal organs/gut o Many advantages . Isolates gut from body movement . Provides a hydrostatic skeleton that can assist in support and movement . Acts as a storage reservoir for gametes, wastes, etc… . Provides a space for organ development WAYS TO MAKE A COELOM • Schizocoely o Splitting within the mesoderm o Protosomes • Enterocoely o Mesoderm forms pockets from gut – out pockets until closes over itself o Deutrosomes

PHYLUM Nematoda • “roundworms” • “ecdysozoan” – molting animal • thick flexible cuticle o must be shed to grow o allows diffusion of gases o must live in moist habitat • psuedocoelomates • longitudinal muscles o move by thrashing • bilaterally symmetric • triploblastic • fluid-filled body cavity – hydrostatic skeleton • complete digestive tract • No respiratory or circulatory system • Important part of the food web of soil o Feed on many things, and are preyed on by many insects

Nematode diversity • ~25,000 species (ext 1,000,000) • terrestrial (moist soil) or aquatic • free-living (scavengers, predatory) or parasitic • extremely abundant • C. elegans o “white rate” of geneticists and developmental biology o At McGill, Dr. Heikimi identified 4 genes, that when mutated, resulted in nematodes to live ~6x their normal life span o Worms used energy more efficiently and fed & swam at a slower pace • Most are scavengers & predators but some are parasitic o Infect protists, plants and animals o 50 species parasitize humans o larges : 9m long (parasite in placenta of sperm whales) o eg hookworm . common in tropics and subtropics . poorly sanitized drinking water with feces or when humans do not wear boots or shoes PHYLUM Annelida • “segmented worms” • ~16,500 Species • terrestrial (moist), aquatic • Lophotrochozoans • Coelomates Why is segmentation so advantageous? • Multiple copies of organs, structures o Ex: nephridia (functional equivalent of kidney), parapodia • Efficient nervous control o Ganglion in each segment o Faster responses • Increases body size by unit repetition • Note that there is regional differentiation o Segments are similar but each can be modified o Ex differentiation of the gut LOCOMOTION • Each segment has o Longitudinal muscles . Compresses segment o Circular muscles . Squishes segment and elongates o Coelomic space (hydrostatic skeleton) • Use penetration anchors • Steps 1. Circular muscles contract • Coelomic fluid trapped in each segment  anterior end elongates • Posterior setae anchor 2. Longitudinal muscles contract • Posterior end brought forward (posterior setae release) SYSTEMS • Respiratory system o Skin (epidermis) • Nervous system o Anterior “brain” o Ganglia o Ventrala nerve cord • Circulatory system o “closed” o dorsal and ventral blood vessels o aortic arches = hearts ADVANTAGES OF A CIRCULATORY SYSTEM • Improved exchange between

o Deeper tissues and surface (O2, CO2) o Gut and muscles (nutrient delivery) • Permits development of a thicker body o Free of diffusion limit ANNELID DIVERSITY • Class Polychaeta o “many hairs” o marine worms o largest group • Class Citellata o Subclass Oligochaeta – “few hairs” . Earthworms o Subclass Hurydinea . leeches CLASS polychaeta • Mainly marine o Often in tidal zones o Along deep sea vents • Detricores, filter-feeder (live in tubes) • Many have eyes, tentacles • Many setae • Parapodia o Leg like structures used in motion and respiration • Searate sexes with external fertilization • Trochophore larvae CLASS Citellata • SUBCLASS Oligochaeta o Mainly terrestrial o Detritovores . Aerate soil o Hermaphroditic . Clitellum  Secretes a mucus cucoon for embryo development . No larvae o Fertilization and copulation do not necessarily occur at the same time • SUBCLASS Hurydinea o Eg leeches o Mainly freshwater o Parasitic and carnivorous o No setae . Anterior and posterior suckers o Hermaphroditic . Clitellum . No larvae (have young that look like little adults) o Medicinal uses . Hirudin – anticoagulant

LECTURE 12: MOLLUSKS Lecture outline • Mollusks • How the nervous system works

PHYLUM • > 100,000 species • 2nd largest animal phylum • terrestrial or aquatic • highly diverse: o morphology o modes of nutrition o reproduction o response to environment MOLUSK BODY PLAN • Foot o Muscular tissue o Locomotion • Mantle o covers internal organs o secretes CaCO3 shell • visceral mass o organs – heart, stomach etc • mantle cavity o area where gills are found in aquatic o acts as lung (highly vascularized) in terrestrial (high SA) • radula o in mouth, tearing/scraping “teeth”

CLASS Polyplacophora • “many plates” • segmented shell (8 overlapping plates) • multiple gills • omnivorous o radula scrapes algae & bryozoans • large muscular foot • ability to roll into a ball (like armadillo) • gills located in mantle grooves • eg , common to intertidal zones

CLASS Bivalvia • Reduction of head • Hinged shell • Enlargement of foot o Used for anchor and for digging • Mantle cavity modified by siphons o Extensions of posterior mantle o Water flows in mantle cavity and then across gills that act as filters for food • Enlargment of gill • Relatively sessile o Mussels use byssal threads to hold on • Filter feeders • Broadcast spawners • Eg Scallop o Large adductor muscles to close shell . Can move by jet propulsion o Mantle lined eyespots

CLASS Gastropodia • “stomach foot” • Most diverse class (70, 000 species) • Terrestrial or aquatic • Shelled (snails) or shell-less (slugs, nudibranchs) • Herbivores, predators, scavengers • More complex head and eyes • Dioecious or hermaphrodites (but can produce only sperm or eggs at one time) o Internal or external fertilization • Undergo torsion (twisting) of body o 180° rotation of visceral mass o mantle cavity, anus moved over head o elongate up, then coil o means they can grow continuously and be relatively compact • coiling of visceral mass

CLASS Cephalopoda • “head foot” • subdivided foot  arms, tentacles • enlarged head, reduced shell o beak, radula, siphon • one extant shelled o Nautilus o 80 - 90 arms o regulate buoyancy with gasses in chambered shell o ammonite, dominant predator 300 mya as predators • predators with excellent vision (lens) • complex behavior o visual communication with colour and texture (chromatophores, controlled pigment cells) • ink sac – defence • closed circulatory system o more nutrients and oxygen to muscles • arms with suckers and/or hooks o some have two elongated tentacles Reproduction • Separate sexes with elaborate courtship • Internal fertilization, where males transfer sperm via specialized arm – hectocotylus • Females die after laying eggs or after eggs hatch • No trocophore larva

MOLLUSKS CONCLUSION • Economically & culturally important o Food (Shellfish) o Jewelry (pearls, abalone) o Vectors for parasites (snail: blood fluke) o Exotic invasions (zebra mussel) • Neurological research o Squid neurons o Giant squid neurons can be 1mm in diameter – specialized for fast movement

NERVOUS SYSTEM • Function: receive process and relay information • Anemone has nerve net, earthworm and squid ganglia nerves, humans have central nervous system (CNS) and peripheral nervous system (PNS) •

GENERALIZED NEURON STRUCTURE • Dendrites – end “branches” receive info from other neurons • Cell body – contains nucleus and most cell organelles • Axon hillock – meeting point of cell body and axon, integrates info collected by dendrites and initiates action potentials • Axon – “telephone line of nerve cell” that synapse at terminal to target cell (other neuron, gland or muscle cell) • Neurons may vary in size and shape depending on function

HOW DO NEURONS WORK? • Electrochemically • Electro – difference in charge across the cell (neuron) membrane • Chemical – charge due to ions (Na+, K+, Cl-) and negatively charged proteins • Lipid bilayer prevents free movement on ions, but rather ions must diffuse or be transported across and ion channel or transporter

Measuring membrane potentials • Electrodes inserted into axon • Can chart electrical potential across membrane • Resting potential = approximately -60mV • Typical electrochemical gradient of mammalian neuron at resting potential o Ion (Outside/Inside) o K+ (5.5 / 150) o Na+ (150 / 15) o Cl- (125 / 9) o Negatively charged particles (none / 106.5)

Pathways • Ion transporters o Na/K pump o Actively expels Na+ & exchanges them for K+ o Requires ATP • Ion channels o May be gated . Leak channels (no gate) . Voltage-gated . Chemically-gated . Mechanically-gated o No energy used

EQULIBRIUM • Some K+ channel always open, but K+ reaches equilibrium across membrane in absence of a stimulus • Two opposing forces operate to bring about equilibrium o Diffusion force – K+ moves from low to high concentration o Electrical force – movement of K+ out of the makes intracellular invironment more negative, pulling some K+ back into the cell

ACTION POTENTIAL • Nerve impulse = action potential • Rapid voltage change across membrane o 1 to 2 milliseconds in duration • 3 Major processes o depolarization, repolarization, Na+/ K+ pump o involve Na+ and K+ concentration differences ACTION POTENTIAL (SPIKE) PROCESS Step 1 – resting potential, some K+ channels open o More Na+ outside neuron, more K+ inside neuron Step 2 – A few Na+ channels now open Step 3 – all Na+ channels open – depolarization “spike” Step 4 – Na+ channels close. All K+ channels open. Membrane hyperpolarizes Step 5 – all gated channels close. Na-K pump returns membrane to resting potential

SUMMARY: • Depolarization: Na+ gates open o Na+  in o If threshold level of depolarization reached at -50mV, then “action potential” (spike) • Repolarization: all Na+ gates close while K+ gates remain open o K+  out o membrane hyperpolarized and Na+ still on inside • Sodium potassium pump: o returns the membrane to resting state o Na+ out, K+ in and out

WHAT DETERMINES WHETHER AN ACTION POTENTIAL IS FIRED? • Summation of signals occurs in axon hillock • May integrate signal across a few synapses or from a single synapse when signals are transmitted at fast frequency o Spacial summation – occurs when several excitary postsynaptic potentials (EPSPs) arrive at the axon hillock simultaneously o Temporal summation – means that postsynaptic potentials created at the same synapse in rapid succession can be summed

TRANSMISSION OF ACTION POTENTIAL ALONG AXON

SPEED OF TRANSMISSION • Depends on axon diameter • Cephalopods require a good nervous system o Signal travels along squid axon at 25 m/sec • But speed up nerve transmission with a different method because there are too many axons (can’t just increase in size) SALATORY CONDUCTION • Schwann (gilal) cells produce and outgrowth membrane = myelin that wraps around axon • Gaps in between are “nodes or Ranvier” o Nerve impulse will “jump” from node to node • Salatory conduction 1. Na+ channels open (depolarizing), gathering action potential at Point A 2. Current brings channels at next node to threshold (Point B) 3. Na+ channels close (at Point A), membrane is refractory and repolarizes 4. Action potential jumps to next node (Point B) 5. And so it continues .. Point A: Na/K pump. B: repolarizing. C: depolarizing • Signal is transferred in one direction because Na+ channels have a refractory period after they close where they cannot open again immediately TRANSMISSION AT AXON END • Axon terminals end at a synapse • Neurotransmitters are released into the synaptic cleft o Ex: acethylcholine • Neurotransmitters bind to receptors o On the next neuron o Or a muscle cell or gland • Synapses may be chemical or electrical o Electrical synapses less common in vertebrates . Action potential being directly transmitted to neighboring gland/cell/neuron . Distances between membranes in electrical synapses only a few nanometers and connected by membrane proteins  Proteins connect the two – channels can open continuously CHEMICAL SYNAPSES • Neurotransmitters (secondary chemicals produced in pre-synaptic neuron) are released into the synaptic cleft – ex: acetylcholine) o Synaptic cleft – space between neuron and target cell • Neurotransmitters bind to receptors on post-synaptic neuron or a muscle cell or gland, causing ion channels to open (thus, action potential continues) • Neurotransmitter broken down (or it would constantly feed target cell) and components are taken back up into presynaptic cell

LECTURE 13: ARTHROPODS Lecture outline • Arthropods o Characteristic features o Exoskeleton and molting • Muscles o Neuromuscular junctions and action potential review o Muscle contractions o Muscle tissue types

PHYLUM Arthropods • “jointed foot” o eg insects, crustaceans, arachnids • Protostome group: ecdysozoans • Coelomates • Most diverse eukaryotic group o Eg Dytiscus – predaceous diving beetle, adults collect air under wings and use this to breath underwater o Honey bee (Apis) has among most complex social life – eg worker bees dance to communicate location of new food source . Angle of waggle relative to sun communicates position of food source . Duration of waggle communicates distance of food source . HOWEVER, new data shows that up to 93% of the time other bees ignored the dance . Early experiments were conducted with artificial feeders and few food sources . Other cues such as odor are likely important • Largest eukaryotic phylum • Very abundant (108 individuals alive at any one time) • Reduced segmentation o Body regirons : head, thorax and abdomen or cehalothorax (head + thorax) and abdomen • Jointed appendages o Specialized functions (eg some legs for swimming, some for walking, some for sperm) • Rigid exoskeleton o Ecdysozoan – molting animal EXOSKELETON • Arthropods have a rigid exoskeleton • Non-living • Secreted by epidermis • Covers all external surfaces, digestive tract & tracheae (terrestrial, network of tubes & airsacs for gas exchange) • Composed of layers

• Chitin (“nature’s plastic”), protein + CaCO3 (in crustaceans) • Advantages of rigid exoskeleton o Physical support o Place for muscle attachment o Physical protection . From abrasion, predation, parasite entry . From dessication o Location of pigments (, warning coloration, mating) o Jointed appendages & exoskeleton allow faster locomotion o Opportunity to change morphology between larval and adult stages • Disadvantages o Inflexible and heavy (if thick and protective) o Continuous growth in size is not possible . Must be periodically shed (molted) o Requires energy to from and shed o Prevents use of cilia as effectors o Direct respiration through skin is not possible . Spiracles (pores) and tracheae (tubes) • Discontinuous growth o Mass grows continuously, but size changes in a stepwise fashion . Instars (regions where size constant with time) . Molting (ecdysis) (regions of sudden increase of size)

MUSCULO-SKELETAL SYSTEMS IN ARTHROPODS • Skeletal muscles o Need a resistor to act against (ie a skeleton) o Are often found in antagonistic pairs . Act in opposite directions . “muscles can only pull not push” . note the opposite arrangement in exo and endoskeletons

MUSCLE STRUCTURE • Muscle  bundle of muscle fibers  single muscle fiber (multinucleated cell)  Myofibril bundles (composed of protein bundles)  repetitive units of sarcomeres (contractile unit) in protein bundles  overlapping Actin (“thin”) and Myosin (“thick”) filaments

• To contract, actin moves inwards, sliding along the myosin filaments • The H zone becomes smaller, the lengths of actin and myosin does not change, their amount of overlap does • “Siding filament theory”

• Actin filaments are composed of o Actin monomers (balls) o Tropomyosin (strings) o Troponin (3 subunits) • Myosin filament composed only of myosin o Two polypeptide chains wound together with a globular head

MUSCLE CONTRACTION • Initiation of muscle cell stimulation o Motor neuron and acetylcholine depolarize muscle cell . Acetylcholine released by motor neuron into neuromuscular junction . taken up by muscle cell (initiates action potential) . action potential transmitted through T tubules through sarcoplasmic reticulum (SR, equivalent of endoplasmic reticulum) o Ca2+ stored in SR released into sarcomere o Ca2+ binds to troponin (induces important conformational change) o ** Ca2+ is the main activator of contraction! • Process 1. Initiation o Ca2+ is released, binds to troponin  binding sites on actins monomer (on the actin filament) to be revealed 2. Binding

o globular head (with ADP + Pi) of myosin binds to actin binding site 3. Power stroke

o Pi leaves  Initiation of power stroke, myosin and actin slide o ADP leaves 4. Release o ATP binds to myosin head, releasing it from the actin filament o (note this is why rigor mortis happens, actin and myosin can’t separate without ATP) 5. Reset

o ATP is hydrolyzed to ADP + Pi (which remains attached to myosin head) o Actin and myosin filaments slide back to resting position, ready for round two! • Whole muscle stimulation o How does a whole muscle contract, not just a sacromere? o Single action potential generates a single twitch o Force generated by entire muscle depends on . Number of motor units (aka motor neuron + associated muscle fibers) activated . Frequency at which motor units are firing

SKELETAL MUSCLE TYPES • Fast-twitch fibers o Greater proportion of these seen in weight lifters and sprinters (chicken breast) o Develop maximum tension rapidly but fatigue quickly o Cannot replenish ATP fast enough to sustain contraction for a long time • Slow-twitch fibers o Greater proportion seen in marathoners (dark chicken legs)

o Aka red muscles because contain O2-binding protein myoglobin, many mitochondria and rich in blood vessels o Substantial reserves of glycogen and fat so can maintain steady production of ATP as long as

O2 available • Training can modify the proportion of intermediate fibers to fast or slow twitch but more important are genetic determinants • Skeletal muscle structure o Striated o Cylindrical o Multinucleated o Most are under voluntary control

OTHER MUSCLES • Cardiac muscles o Are striated o Branched in shape, which allow them to withstand high pressures o Smaller than skeletal cells and have one nucleus o Contain pacemaker cells that create their own action potentials (independent of nervous cells) • Smooth muscles o Actin and myosin not as regularly arranged therefore don’t appear striated o Long, spindle shaped with single nucleus o Line internal organs, blood vessels, etc, usually involuntary

LECTURE 14: ARTHROPODS II 12

Hormones • Chemical messenger substance produced by endocrine system • In termites (different morphology) differentiation of castes is induced by hormones that are released in response to environmental and pheromone cues

ARTHROPOD DIVERSITY • 4 major groups (subphylums) with phylogeny currently in revision o Myriapods . eg millipedes, centipedes o Chelicerates . eg spiders, mites & scorpions o Crustaceans . Dominant in marine environment o Hexapods . Includes insects . Dominant in terrestrial environment

SUBPHYLUM Myriapods • “countless feet” • 2 regions o head o trunk • Centipedes (Chilopoda) o 1 pair of appendages per segment o carnivores o ~300 species • Millipedes (Diplopoda) o 2 pairs of appendages per segment o detritivores, herbivores o ~11000 species

SUBPHYLUM Chelicerates • Horseshoe crabs • Prcnogonids (sea spiders) • Arachnids o Spiders, mites, scorpions • No jaws (manibles) • 2 body regions o cephalothorax – appendages o abdomen – no appendages • pairs of appendages o #1 (chelicerae) – fangs o #2 (pedipalps) – copulatory organs, pincers (scorpions) o #3, 4, 5, 6 – walking legs (4 pairs of walking legs)

SUBPHYLUM Crustaceans • Crabs, daphnia, barnacles, shrimp, crayfish, isopods… • Dominant marine , but also in freshwater & terrestrial environments • Head + thorax (cephalothorax) + abdomen • Appendages off each segment • Compose “zooplankton” o Organisms that are unable to swim against currents

SUBPHYLUM Hexapods • = insects + other groups • abundant in freshwater and terrestrial environment, but few marine • 3 body regions o head . antennae, mouthparts (eg mandibles) o thorax . 3 pairs of walking legs . may have wings o abdomen . no appendages

• INSECTS o An abundant and diverse group that includes fleas, bees, termites, aphids, grasshopper, butterflies o Unique to insects: external mouthparts . These are highly adapted for different functions . Herbivores, detritivores, fluid-drinkers, predators, scavengers, parasites o Wings evolved ~320 mya . They may have been secondarily lost by some insect species . A multibranched appendage may have ended up specializing  The gill of a crayfish and the wing of an insect developed from the same structure – they are homologous (structures exist when there is a common ancestor root) • Recall analogous – structures that have to same function and often appearance but different ancestry

RESPIRATORY SYSTEM • Insects and most Myriapods o Holes (spiracles) open into tubular tracheae which branch into finer tubes

o Carry O2 to body cells • Geustaceans o Gills • Chelicerates o Some have spiracles and tracheae o Book gills . Eg horseshoe crabs . Pages of a book, exposed o Book lungs . Spiders, scorpions . Similar but inside the body CIRCULATORY SYSTEM • Open system • Dorsal tubular heart (1 chamber) with pores (ostia; drives blood into hemocoel spaces • One-way valves MAYFLIES • Mayflies go to surface and molt • Live for 30 mins – 24 hours just to mate • Huge may fly emergence, saturates predators • Cue that trigger mayfly emergency o Noticed early emergence from low stream flow and hot years o Late emergence on high flow, cool years o Did an experiment and tetermined that it is the temperature that is the important variable ARTHROPOD SEXUAL REPRODUCTION • Most species are dioecous • Most species lay eggs o Except scorpions which keep eggs inside (and carry on back until first molt) o On land . Internal fertilization . Some use spermatophores when fertilization is not completely internal  spermatophores – waterproof packets of sperm  eg spiders put sperm on web and use this to insert into female o In water . Internal (crabs) or external (barnacles) DAPHNIA LIFECYCLE • Mostly parthenogenic o Diploid female produces diploid daughter without fertilization o This occurs most of summer, when conditions are good • Under stress, partenogenic males and haploid eggs are produced o Stress= decreased food, light decreases, crowding, or temperature decreases • Sexual reproduction results in diapause eggs – ephippia, which hatches under favourable environmental conditions o Can last 30 years or longer before hatching METAMORPHOSIS • Molting enables changes in morphology = metamorphosis o Each instar (larva) produces a new exoskeleton o At each molt, modification is possible • Insects cease molting as adults o Metamorphose to adult form . Incomplete metamorphosis or complete metamorphosis • Crustaceans continue molting as adults • Complete metamorphosis o Eg caterpillar – butterfly o Abrupt changes in form . Have resting stage between large changes in morphology (pupa) o Often major habitat changes . Juveniles do not compete for the same resources as the adults o Egg  larvae  larvae  pupa  adult • Incomplete metamorphosis o Eg grasshopper o Gradual changes in form . No resting stage o Often no habitat change . Egg nymph (smaller form)  nymph  bigger nymph  adult MOLTING • What regulates molting? • Wiggleworth’s experiments using Rhodinus prolixus o A blood-sucking insect, molts after blood meal (the cue!) o It can live a long time after it is decapitated • Molting experiment #1 o Hypothesis: The substance that controls molting in R. prolixus is produced through the head segment and diffuses slowly through the body o Method: Decapitate bugs 1 hour and 1 week after blood meal o Observation: first does not molt (remains as a juvenile) while latter molts into an adult • Molting experiment #2 o What is the nature of this chemical? o Method 1. Decapitate third instar juveniles at different times after blood meal (1 hour, 1 week) 2. Join bugs with glass tube o Results: both bugs molt into adults o Conclusion: a blood meal stimulates production of some substance within the insect’s head that then diffuses slowly through the body, triggering a mold

HORMONES & SYSTEMS HORMONES • Hormones – chemical messengers o Eg steroid, , amine • Secreted by endocrine cells • Hormones are distributed by blood, bind to target • Some chemical signals act locally without entering the blood stream o Paracrines . Only target neighboring cells . Either hormones are released in very small quantities, break them down much quicker, or they are so efficiently taken up that they never make it to the blood stream o Autocrines . Target themselves ARTHROPOD MOLTING HORMONES • PTTH (brain hormone) o Stored and produced in the brain (neurohormone) o Production influenced by environmental cues o Controls activity of prothoracic gland • Ecdysone o Produced by prothoracic gland o Secreted into blood o Target cells = epidermis o Response = ecdysis (molting) o Brain responds by shutting off PTTH hormone (negative feedback) • Juvenile hormone o Released from brain o Declining releases influences developmental stages of metamorphosis aka tells body what stage of development it is at o None at last stage from pupa  adult . This fact can be used to keep silk worms at the 5th instar • Molting process o PTTH triggers the periodic release of ecdysone, which triggers molt o From 1st instar to 5th, there are declining amounts of juvenile hormone released o None relased at last instar and the arthropod becomes an adult

BODY CONTROL SYSTEMS • Endocrine System o Hormones o Diffuse via blood o Slower, longer term o Many glands: thyroid, parathyroid, adrenal glands, anterior and posterior pituitary, hypothalamus (in brain) • Nervous system o Action potentials o Voltage change along neurons o Quicker, short term • Both systems work together o Neurons trigger hormone release o Neurons in hypothalamus make hormones released by the posterior pituitary gland • SNAKE! (response of nervous and endocrine system to stimuli 1. Brain detects danger and signal the leg to jump back 2. Brain signals adrenal gland to release epinephrine 3. Epinephrine causes A. Liver converts glycogen to (energy) B. Heart beats faster C. Blood vessels to gut and skin constrict, shunting more blood to muscles D. Fat cells release fatty acids (fuel) into blood

HYPOTHALAMUS / P&A PITUITARY GLAND • Hypothalamus interacts with the PG, releases a hormone with stimulates a reaction • Hormones may have different actions on different cells • Neurohormones of PPG (Posterior pituitary gland) o ADH (anti-diuretic hormone) . Trigger : increase salt concentration in blood . Function: water is conserved and urine is more concentrated . Targets: kidney . Action: increased reabsorption of water o Oxytocin . Target 1: smooth muscle of uterus . Action1 : contractions . Target 2: mammary glands . Action 2: milk release • Neurohormones of APG (Anterior pituitary gland) o Hormone from hypothalamus tropic hormone released  endocrine gland releases another hormone o “short loop” negative feedback, where tropic hormone inhibits hypo o “long look” negative feedback, where end hormone inhibits both APG and Hypo

HOW DO HORMONES WORK? • Hormones act by 1. Affecting the expression of a gene 2. Altering the activity of an existing 3. Changing permeability of a • Insulin is a good example of hormone reception and cellular response o Insulin – helps the uptake of glucose into cell o Produced by pancreas o Lowers blood glucose level o Insulin receptors  signal transduction trigger . Creation of new glucose importers through gene expression and growth regulation . Activation of glucose importers (by bringing them to membrane) . Up glucose utilization and glycogen/lipid/protein synthesis

REGULATION OF GLUCOSE LEVELS IN BLOOD • Glucose levels high o Pancreas (beta cells) create insulin o Cell – uptake glucose (excess converted into fat) o Liver – store as glycogen • Glucose levels low o Pancreas (alpha cells) create glucagon o Cells – convert fats to glucose o Liver – break down glycogen Diabetes mellitus – disease of high blood sugar “copious amounts of glucose-rich urine” • Type I (juvenile onset diabetes) o pancreatic cells don’t make insulin o treatment = insulin • Type II o target cells not responsive to insulin o treatment = diet, exercise or drugs to reduce blood glucose & restore sensitivity to insulin

REGULATION OF CALCIUM LEVELS IN BLOOD • Ca2+ concentration high o >11mg/100 ml blood o thyroid secretes calcitonin . promotes Ca2+ uptake by osteoblasts and storage in bones . inhibits osteoclasts • Ca2+ concentration low o <9 mg/100ml blood o Parathyroid secretes PTH . Shifts Ca2+ from bone to blood and Ca2+ retention in kidneys . PTC converts vitamin D to Cacitriol (causes digestive system to absorb more Ca2+)

LECTURE 15: ECHINODERMS, CHORDATES INTRODUCING THE DEUREROSOMES Lecture outline 1. Protostome vs Deuterosome review 2. Echinoderm i. Diversity ii. Water Vascular system 3. i. Characteristics ii. Urochordates iii. Cephalochordates

EVOLUTIONARY INNOVATIONS ACROSS ANIMAL GROUPS So far • Multicellularity • Tissues • Gut • Mesoderm • Head • Segmentation These differ between protostomes and deutrostomes • Nervous system • Anus • Circulatory system • Hard skeleton • Coelom Map these developments!

PROTOSTOMES VS DEUTEROSTOMES • The two major evolutionary lineages of Bilateria • Split around the Cambian period (~500 mya) • Deutrostomes - mouth second (blastopore develops into anus) • Circulatory system has a ventral heart • Central nerbous system is dorsal • Hard skeleton is internal

WHO ARE THE DEUTEROSTOMES?

• SUPERPHYLUM Deutrostome • Echinoderms • (Hemichordates, which we won’t look at) • Chordates o Cephalochordates o Urochordates o Vertebrates

PHYLUM Echinoderms • ~7000 extant species • strictly marine • benthic (bottom dwellers) • diverse modes of nutrition • ex: sea stars, sea urchins, sand dollars • hard endoskeleton

o composed of CaCO3 plates (“test”) o continuous growth . plates enlarge and new ones are added o covered by thin layers of skin and muscle • Asexual reproduction o Regeneration . Arm may be dropped and regenerated to  Escape predation  Decrease change of infection o Parthenogenesis . Development of an unfertilized egg . Can be induced artificially in sea urchin by exposing eggs to appropriate salt solution • Diversity o Echinoids (sea urchin) o Holothuroids (Holothuroids) o Ophiuroids (brittle star) o Crinoids o Asteroids (sea stars)

SUBPHYLUM Chrinoids • Sea lilies and feather stars • Filter feeders • ~700 species • much more prevalent 300-500 mya SUBPHYLUM Ophiuroidea • Brittle stars o Many arm spines o Filter-feeders, predators o Detritivores • Basket stars o Branched arms o Filder-feeders SUBPHYLUM Echinoids • Sea urchins o Have many spines – locomotion, defence o Pincers (pedicellariae) – defense, cleaning (Echinoids and asteroids) o Have Aristotle’s lantern for scraping algae off of rocks • sand dollars SEA CUCUMBERS • detritivores, scavengers, filter-feeders • reduced endoskeleton (ossicle) • five rows of tube feet • respire by drawing water into anus • commensal relationship (+/o) with pearlfish • specialized sticky tissues expelled from anus for defence SEA STARS • Predatory • Fairly mobile • Evert stomach, secrete enzymes to digest prey and then engulf partially-digested prey • Crown of Thorns o Feeds on coral polyps o Responsible for periodic coral destruction on Great Barrier Reef o Preyed on by Giant Triton (snail)

PHYLUM CHORDATES • ~65, 000 species • includes the vertebrates • deuterostomes • coelomates • bilateral symmetry • pharyngeal slits are an ancestral trait of deuterostomes (since lost? But in hemichordates) • Have traits unique to chordates 1. Dorsal hollow nerve chord 2. Notochord (rod of cells that provide rigidity but flexibility) 3. Post-anal tail • Traits common to chordates o Ventral heart o Reduced segmentation o Segmented musculature . “myomeres” • Include subphylum Cephalochrodates, Urochordates, Vertebrates NEURULATION • -formation of nervous system • the dorsal side of the ectoderm thickens (forms the neural plate)  the sides ridge and come together  pinch off  form a separate neural tube with crest cells

SUBPHYLUM Cephalochordates • lancelets (fishlike) • ~30 species • fish-like bodies • live in sediments (stick head out) o tropical, shallow marine water • 1-5 cm • filter-feeders • adults retain all 3 chordate characteristics

SUBPHYLUM Urochordates • ~3000 species, 90% are tunicates (sea squirts) • marine • as adults o 1mm-60cm o solitary or colonial o benthic (bottom), sessile (attached) o body structure . a body surrounded by a “tunic” for structure (flexible and rigid outer structure) . loses notochord . filter-feeders . incurrent and excurrent pores . pharynx lined with cilia and mucus . mouth and anus (separate? Both upwards) • as larvae o planktonic o resemble tadpoles o have all 3 chordate characteristics (and pharyngeal slits) • *** early developmental stages can reveal similarities among organisms – these similarities may not be as evident in later development • Life history o Planktonic larva o Larva settles on its head o Pharynx enlarges o Head and tail degenerate o Becomes sessile adult • Threatening Canada’s mussel industry o 77% of Canada’s production of blue mussel comes from PEI, where tunicates such as the vase tunicate have invaded o the vase tunicate can completely cover mussels and make it economically unfeasible to grow and harvest

LECTURE 16: FISHES WHAT IS A ? EVOLUTION OF THE JAW, CIRCULATION PHARYNGEAL SLITS (pouches) • Located on lateral surface of head • Appear to be an ancestral trait in deuterstomes • Lost in echinoderms • Derived from ecto, meso and endoderm • In vertebrates, tissues supported by arches (cartilage, bony tissue) • Function o Filter feeding (cephalochordate, urochordate) o Gas exchange . Water passes through slits

. O2 and CO2 can be exchanged across a respiratory surface = gills . Gills located between slits, supported by arches

GILL SLITS AND GILL ARCHES • Pharyngeal slits = gill slits • Cars between slits – gill arches o Bone or cartilage o Gill filaments are on the gill arches • Ray finned fish o Have 4 pairs of gill arches o Each arch has a pair of gill filaments o have cover (operculum), also assists in ventilation of gills o use mouth and buccal cavity (floor of mouth) to bring water in, lower buccal cavity like diaphragm, close mouth and force water through gills • gill filament structure o thin, vascularized, high surface area o blood vessels flow through gill arches o capillary beds in gill filaments o filament in one cell thick o ***Water and blood flow in opposing directions . called countercurrent exchange

. achieves maximum exchanges of gasses (O2 & CO2) . as saturation of O2 in blood rises, it encounters newer water, with increasingly higher

O2 concentration

CIRCULATORY SYSTEM IN VERTEBRATES • Heart o Strong muscular pump o Ventrally located o Maintains blood flow o 2+ chambers (auricle/atrium and ventricle) o one-way valves inside • closed circulation o arteries  arterioles carry blood away from heart to capillary beds o venules  veins carry blood to the heart o Afferent (going to organs they supply) vs efferent (coming from)

FISH CIRCULATORY SYSTEM • In fish, heart pumps only deoxygenated blood o Heart(afferent) ventral aorta  gills  dorsal aorta  arterial blood distributed to body  venous blood collected from the body heart • Fish heart o 2 chambers and folded o enlarged sinus venosus and (bulbus) conus arteriosus o  S.V.  aorta  ventricle  S.V. towards anterior

SUBPHYLUM Vertebrate • Circulatory system o In fish and larval amphibians . Blood oxygenated in the gills . Single circuit  Heartgillsbodyheart o In adult amphibians, reptiles, birds, mammals . Blood oxygenated in lungs . Double circuit (pulmonary --| -- systemic -- -- |)  Heart  lungs  heart  body  heart . In non-fish vertebrates, blood is under much higher pressure • Characteristics o Axial skeleton . Cranium (skull) . Vertebral column (spine) . Ribs o (Appendicular skeleton) . Pectoral girdle . Pelvic girdle o Closed circulatory system . Ventral heart o Organs suspended in coelom • Phylogeny (Gnathostomes = “jawed mouth”)

HAGFISH/LAMPREY DILEMMA • Hagfish differ from other vertebrates based on o Don’t have a vertebral column (retain notochord instead) o Have a partial cranium and brain o Have 3 accessory hearts instead of one large heart • But, they are genetically similar to Lamprey, thus some consider both as a related Cyclostome (“circle- mouth”) group/ It is possible that some features were lost/secondarily evolved

HAGFISH • 58 known species • live in marine and benthic habitats • virtually blind, but rely on smell and tentacles around mouth • tongue equipped with tooth-like rasps • diet= dead organisms and polychaeates • for defense secrete slime (then tie themselves in a knot to wipe off0

LAMPREYS • freshwater and marine, but marine taxa return to fw to spawn • complete braincase and true vertebrate (cartilaginous) • invaded Great Lakes when canals constructed and have had damaging consequences on fisheries o horrible toothy mouths, hook onto trout and release anticoagulants

JAWS • Not present in early fishes and present-day “cyclostomes” • Formed by fusion of gill arches • Teeth evolved from scales around mouth • Greatly improved ability to feed and diversify

EARLY JAWED FISH • Placoderms – earliest branch of jawed fishes • Heavy bony armour on the head and neck • No teeth but bony plates that acted like teeth • Present during Silurian and Devonian in freshwater and saltwater, but went extinct at end of Devonian • ~15 m

CHRONDRICHTHYANS • “cartilaginous fishes” • sharks o eg cookie cutter shark . eats chunks out of other animals, live and dead • skates, rays o feed on mollusks and other animals in sediment o undulate enlarged pectoral fins for movement o skates have two lobes on pelvic fin • ~1000 extant species • mostly marine • jaws • paired fins o on pectoral and pelvic limb girdles o fins primarily used for steering, stabilizing and lift o skates and rays have modified pectoral fins for swimming • locomotion in fish o segmented muscles (myomeres) enable swimming via lateral undulation . alternate contraction of myomeres . antagonized by stiff, yet flexible, segmented axial skeleton . major swimming mode of most fish • 5-7 gill slit pairs • placoid scales • no swim bladder but have oily liver • predators, scavengers and filter-feeders (whale shark)

REPRODUCTION • internal fertilization • claspers (hook things, only on males) • oviparous, ovoviviparous, viviparous • Oviparous fish o Female lay eggs before or soon after fertilization o Young feed off yolk sac outside of mother’s body o Embryo may stay in egg casing for up to 2 years o Eg horn shark and skate • Ovoviviparous fish o Female retain embryos in uterus but young feed off of yolk sac inside mother • Viviparous fish o Female retain embryos and young are fed from nutrients that are delivered from mother via placenta or secretions from uterus o Eg whale shark

RAY FINNED FISH • Freshwater and marine • ~30,000 extant species o eg Mola mola (1000 kg) o eg deep sea anglerfish . 700-1000 m below sea level . bioluminescent lures . use pheromones to find mates in scarce environment . parasitic males – latch onto females for life • morphologically diverse: span large range in sizes (few grams = 2300kg) • operculum • paired fins • scales • swim bladder o enables neural buoyancy o gas regulated by gland in bladder • planktivores, predators, herbivores, insectivores, frugivores • Fins no longer needed for stabilizing or for lift o Can be used for fine steering, stopping, etc . Pectoral fins located higher on sides . Pelvic fins moved anteriorly under pectoral fins o Can be modified for other functions . Eg cichlid has egg decoys to release sperm into mouth of female (where she keeps the eggs – mouth brooder) . Flying fish (glide) . Pacific spiny lumpersucks – fins have developed into suckers

SARCOPTERYGIANS • Include Coelacanths, Lungfishes, Amphibians, Amniotes (that evolved from them?) • Arose from an ancestor with jointed fins

COELACANTHS • Skeleton mostly cartilage (but bony ancestor) • Until recently thought to be extinct • 1938 – found at African fish market • 1998 – 2nd species found off coast of an Indonesian island • eg Latimeria o predator o up to 1.8 m in length o weighs up to 82 kg

LUNGFISH • Fleshy appendages • Live in swampy, muddy waters • Endure dry spells by burrowing into mud entering and inactive state but breath air • Have a primitive lung (modified swim bladder) + gills

LECTURE 17: AMPHIBIANS THE RISE TO LAND, RESPIRATION Why move to land? • Devonian droughts ~400 mya o Shallow inland seas, swamps, ponds

o High temps = low dissolved O2 • High competition in water o Crowding in shallow pools • Insects and plants on land • No vertebrate predators

Problems on land 1. Water needed to prevent desiccation o Need to stay moist o Most require water for fertilization and larval development 2. Air is less dense than water o Require stronger skeletal support, muscles

o Require more energy, more O2 brought in and distributed 3. Air temperature more variable o Body temperature will fluctuate more o Need to modify behavior or physiology 4. UV radiation more intense on land o Need physical protection or change behavior

Advantages of terrestrial respiration • Air has a higher concentration of oxygen than water • Gasses diffuse faster in air than water • “Lungs” evolved early in fish groups • gas bladder used as supplementary respiratory organ, then later modified for buoyancy

GAS BLADDER • Early gas bladders o Present in early fish – placoderms (now extinct) o Used as a supplementary respiratory organ . Gulp air at surface o Reappeared in . Ray-finned fishes . Lobe-finned fishes • Gas bladder in modern Ray-finned fishes o Formed from a single dorsal pocket off o Evolved into a swim bladder or supplementary respiratory device o Most fish have lost connection to tract • Lobe-finned fishes o Formed from paired ventral pockets off esophagus o Evolved into a supplemental respiratory device o (also the most direct ancestor to tetrapods) . common during Devonian . declined after Permian extinction (~290 – 245 mya) . only 8 extant species

LUNGFISH • = sister group to tetrapods • walk on lobe-fins o tetrapod motion o breathe through gills and primitive lung

EARLY TETRAPODS • Stronger limps and girdles, vertebral column, ribs • Tail used for balance, not swimming • Lungs were primary respiratory organ • External and internal nostrils • First evidence in Eusthenopteron  transitional form Tiktaalik  1st early tetrapod: Ichthyostega o Tiktaalik discovered on Ellesmere Island, Nunavut 2004 o “fishapod” . fish – scales, gills, fins, . tetrapod – mobile neck, lungs, ribs, strong wrist bones

TETRAPOD SOLUTIONS 1. Desiccation o Scales o Amniotic egg (in placental organs, simply a membrane in uterus) 2. Air less dense o Stronger limbs, ventral column, ribs o More efficient circulatory system . 3+ chambered heart . double circuit of blood flow 3. More variable air temperature o Feathers, fur o Endothermy (metabolically regulate body T) o Behavioral adaptions 4. More intense UV radiation o Scales, feathers, fur

CIRCULATORY SYSTEM • In fish and larval amphibians o Blood oxygenated in the gills o Single circuit . Heart  gills  body  heart • In adult amphibians, reptiles, birds, mammals o Blood oxygenated in lungs o Double circuit (pulmonary, systemic) . Heart  lungs  heart  body  heart

ADULT AMPHIBIAN HEART • 3 chambered • auricle/atrium is divided by a septum o body  vena cava  RA  Ventricle  pulmonary artery (lungs) o lungs  pulmonary vein  ventricle  aorta (body) • mixing of blood in ventricle •

RESPIRATORY SYSTEM • Function o Exchange gases of cellular respiration

o C6H12O6 (glucose) + O2  CO2 + H2O + ATP • Types o Diffusion across all body cells o Capillaries carry gases to/from resp surface o Specialized organs for exchange • Respiratory surface must be moist! • Examples of respiratory surfaces o Epidermis () o Mantle cavity (terrestrial mollusks) o External gills o Internal gills (aquatic arthropod) o Lungs (mammal) o Tracheae and spiracles (insects)

MAMMALIAN RESPIRATORY SYSTEM • Upper respiratory tract o Nasal passage/oral cavity  pharynx  larynx  trachea • Lower respiratory tract o Lungs found in thoracic cavity with pleural membrane surrounding lungs o (lung) bronchi  bronchioles  alveoli • trachea and bronchi are lined with cilia (for dust etc) • Alveoli o Microscopic air sacs o High SA o One-cell thick o Release surfactants (keeps walls apart) o Exchange gasses with capillaries • Gas exchange

o O2 diffuses into capillaries o O2 carried on hemoglobin of RBC

o CO2 diffuses into alveoli

o CO2 dissolved into blood plasma • Respiratory diseases o Emphysema – alveoli are destroyed by inflammation (smoking, tar destroys cilia) o Cystic Fibrosis – too much mucus produced (genetic) o Asthma – smooth muscles constrict tracheae and bronchi

MECHANISMS OF BREATHING • Negative pressure breathing o Diaphragm contract and relax, change volume/air pressure o Intercostal muscles assist in breathing o Eg Humans • Positive pressure breathing o Amphibians o Inhalation is a 2 stroke process o 1 – air is drawn into mouth cavity while glottis remains closed o moth cavity is then closed, glottis opens and air forced into lungs o amphibians have 3 respiratory organs – lungs, epidermis, inside of mouth

AMPHIBIANS • ~6000 species • first tetrapod • freshwater and terrestrial o dependent on water for external fertilization, aquatic larvae, cutaneous (skin) respiration, excretion of ammonia as waste • smooth moist skin o No scales o Glands • Teeth’ • Carnivores o Tongue attached anteriorly Body structure • Larvae o Gills o 2-chambered heart o herbivores o undergo metamorphosis • adults o lungs o 3-chambered heart o carnivores metamorphosis • hormonally controlled • in frogs, toads and salamanders o shift in respiration, circulation, dieat o tail reabsorbed (frogs and toads) o skin thickens and forms glands o develop . 2 pairs of limbs . jaws . tongue . internal nares . ears . eyelids • some do not undergo metamorphosis o Neoteny (paedomorphosis) o Many salamanders fail to transform . Remain in larval form . Can reach sexual maturity o TYPE A: obligate neotene . Never metamorphose . Eg Sirens and Mudpuppies o TYPE B: Facultative neotone . Metamorphosis depends on conditions . Eg tiger salamander • Some bypass metamorphosis o Direct development o Some frogs & salamanders undergo complete development within the egg o Some amphibians are viviparous (held within the mother) . Eg New Guinea froglets reproduction • oviparous • separate sexes • mostly external fertilization o mate from behind – amplexus • little parental care • oddities o pouch brooder . marsupial frog- keeps them on her back . Surinam toad – sink into thickened skin on back, come out fully formed o Vocal sac brooder . Darwin’s frog o Gastric brooding frog . Female swallows eggs after fertilization . Offspring metamorphose in stomach . Chemicals from eggs and larvae stop HCl production and muscle contractions of stomach . Mother does not feed while brooding young, which can last up to 7 weeks . 2 species in Australia, believed to be extinct amphibian diversity • 3 major groups • Salamanders o Most have internal fertilization • Frogs and toads o Most species rich group o Males typically have loud courtship calls to females • Caecillans o Have lost appendages o Look like worms but have dorsal nerve cord o Tropical, burrow in soil or aquatic o Reduced eyes – see light o Viviparous

AMPHIBIAN DECLINE • The major causes are habitat loss and disease (citrid infection, ) • Amphibians are abundant. On an individual basis, they outnumber all other tetrapod animals • Amphibian populations fluctuate greatly in size, making them highly unpredictable • 41% of species at risk – most threatened category of animal

LECTURE 18: REPTILES BEING TERRESTRIAL: AMNIOTIC EGG, EXCRETORY SYSTEM HEARTS • Birds and mammals have completely separate pulmonary and systemic systems • Reptilian hearts are more separated than amphibians

• Some turtles, snakes and lizards still go to aquatic habitat – no need to send blood to lungs

REPTILE ADAPTAIONS TO LAND • Now truly terrestrial • More efficient heart (compared to amphibians) • Breathe via lung only • Must conserve water o Skin is waterproofed by keratin o Produce a special nitrogenous waste • Reproduce and develop on land o Internal fertilization o Amniotic egg

NON-AVIAN REPTILES • ~ 6,000 species • mostly terrestrial • carnivores, herbivores, omnivores • dry skin, scales • first amniotes o arose during Carboniferous ~300 mya

AMNIOTIC EGG • Amniotic egg = egg surrounded by extra-embryonic membranes • External shell (May have)

o Leathery (eg komoto dragon) or brittle (CaCO3 chicken)

o Permeable to gases (O2 and CO2 ) o Fairly impermeable to water o Not present in therian mammals • Structure o Amnion . Layer around embryo for protection o Yolk sac . Attached to embryo, encloses nutrients o Allantois . Sac, gas exchange and stores wastes o Chorion . Surrounds these four – gas exchange and prevents water loss o Albumen . “Egg white” • consequences of terrestrial egg o internal fertilization . sperm cannot penetrate egg shell . shell and albumen are added to the fertilized egg in the female’s oviduct o non-toxic nitrogen waste product is required . uric acid

WASTE • Excretory organs o control volume, concentration and composition of extracellular fluids and excrete wastes • Excretory products o Salt, ions . Released by skin, gills, kidneys or specialized glands o Water o Fecal matter . Released by digestive system o Nitrogenous wastes . Product of protein and DNA metabolism . Released by excretory organs (kidneys) as well as skin and gils NITROGENOUS WASTES

• Ammonia (NH3) o Very soluble in water (polar) o Very toxic o Needs to be diluted and disposed of quickly or converted to a less toxic form (urea or uric acid) o Ray finned fish, aquatic inverts (marine fresh), larval amphibians • Urea o Soluble in water (polar) o Not very toxic o Less water needed for disposal o Cartilaginous, mostly adult amphibians, mammals • Uric acid o Insoluble in water o Non toxic o Little water needed for disposal o Insects, reptiles, birds (perfect for amniotic egg) • Animals can produce more than one type of waste than their main one (which is in great abundance) o humans produce uric acid metabolizing nucleic acids and caffeine o also produce ammonia to regulate pH

SALT AND WATER BALANCE • Salt and water balance may match environment • Osoconformers o Organisms whose extracellular fluid is equilibrated with the environment o Track level of salt concentration in environment o Many marine vertebrates o BUT there are limits the ability of an organism to osmoconform . Too salty denatures proteins . Too dilute can’t retain min. amount of nutrients and salts • Osmoregulators o Organisms whose extracellular fluid is held at a concentration different from the environment o In low solute concentration (freshwater) . Water rushes into body (as the body has a relative high solute conc) . Eg tadpole and fish in freshwater are always urinating to regulate salt content . really dilute urine . eg sharks and rays retain urine in their extracellular fluid to increase their body’s salt concentration o High solute (marine) . Many marine fish are always drinking water and producing very little urine . Water rushes out (as the body has a relative low solute conc) . Very concentrated urine

EXCRETORY STRUCTURES OF INVERTEBRATES • Flatworms o Flame cells + tubule = protonephridia o Beating of cilia causes fluid to enter tubule o Once fluid inside tubule, is modified then excreted via excretory pore • Segmented worms o (meta)nephridia o fluid enters ciliated opening into tubule (nephrostome?), solutes actively reabsorbed by capillaries o dilute urine excreted via nephridiopore • Insects o Malpighian tubules – filamentous structures that branch off of mudgut 1. Uric acid, Na, K actively transported into tubules and water follows 2. Transport to hindgut and rectum 3. Na, K actively transported out and water follows 4. Uric acid excreted

KIDNEY • Aka vertebrate excretory structure • Huge amount of redundancy • Function o To regulate levels of water and dissolved solutes in blood (“filter the blood”) and to form urine • Nephron o functional unit o millions of them, line outside • filtering blood bedins with the unselective transmission of ions, water and small molecules from (capillaries in) Glomerulus to Bowman’s capsule • Many ions, nutrients and water are reabsorbed o Following filtration, filtrate then enters the renal tubule where specific ions are reabsorbed and returned to blood o Some additional substances are secreted into filtrate for excretion o Final filtrate is excreted • Renal failure results in retention of o Salt and water (high blood pressure) o Urea (uremic poisoning) o Metabolic acids (acidosis) o Treatment . Dialysis – where dialysis solution has lower concentration of materials being filtered from the blood • Urine concentration controlled by ADH – regulates anti diuretic hormone o Rise in blood osmolarity  hypothalamus stimulates PPG and releases ADH

LOOP OF HENLE (KIDNEY II) • Birds and mammal kidneys produce urine more concentrated than their extracellular fluids • A more concentrated urine is produced by setting up a strong concentration gradient within medulla which is mediated by the Loop of Henle in kidney o Obviously this allows for greater reabsorbtion of water • Process o Thin descending limb – only permeable to water . diffusion o Thick ascending limb – only permeable to soutes . More mitochondria . Diffusion and active transport • Human kidneys process 2000L (of total 5L) blood per day

AMNTIOTES Phylogeny • Turtle = Order Testudines or non-monphyletic group with Testudine • thus all turtles Cannot be considered tortoises

ORDER Testutines (Turtles and Tortoises) • Both have shell • Have changed very little in the past 250 million years • The dorsal and ventral bony plates form a shell. Dorsal shell is an expansion of the ribs. • Most are aquatic, some terrestrial. Sea turtles come ashore to lay eggs. • Human exploitation has resulted in declining populations— all are now endangered

LEPIDOSAURS • Squamates: incl. lizards and snakes • Tuataras – resemble lizards have several different characters; only two species survive. o Third eye on head • All have skin covered with horny scales. • Gas exchange is only through the lungs.

ARCHOSAURS – CROCODILES • Crocodilians = crocodiles, caimans, gharials, and alligators o Alligators have wide U-shaped snout while crocodiles have a longer, pointed V-shaped snout • spend much of their time in water. • They build their nest on land or floating piles of vegetation. • All are carnivorous.

ARCHOSAURS – DINOSAURS • Term Dinosaur coined in 1842 to mean “fearfullygreat reptiles” • In terms of phylogenetic taxonomy Dinosaurs = o Ornithischians - beaked, herbivorous dinos o Sauropods – includes the largest animals to have ever lived on land o Theropods (incl birds) – bipedals and primarily carnivorous (t rex!) • Dinosaurs dominant large land animal from Triassic to Cretaceous • Almost complete extinction at end of Cretaceous (65 mya)

LECTURE 19: BIRDS (AKA REPTILES PART II) ENDOTHERMY, FLIGHT AMNIOTES • Organisms with extra embryonic membrane o Yolk sac, chorion, allantois amnion o (Albumen and shell don’t count – they come from the mother)

BIRDS • The ancestor to birds was probably a theropod dino, which share these characteristics: o bipedal, 3 hind toes o carnivorous o 4-chambered heart o similar lungs o feathered o hollow bones o parental care of eggs and juveniles • found a Archaeopteryx “ancient wing” o 11 fossil species o feathers wings o teeth, bony tail • ~9,600 species • amniotes • endothermic • 4-chambered heart • feathers • most fly • diverse beaks o diverse diets (carnivores, herbivores, nectivores) o can see this with Galapagos finches (which all arose from a common ancestor) • parental care o Egg incubation is necessary . eggs cannot thermoregulate . parents must maintain egg temperature o Most build nests o Juveniles require high calorie diets . fast growth rates . high surface area to volume ratio . must be fed on a continuous basis

THERMOREGULATION • Body temperature control • Ectotherms o Absorb external heat o Metabolic process vary with temperature – slower when colder o Can ses behavioral thermoregulation • Endotherms o Generate their own internal heat through metabolic processes o They are less efficient at transforming energy o Maintain a relatively constant body temperature by exerting more energy in colder environments • Some might be called “heterothermic” o Hybernation (eg bears)  metabolic process drop, heat drops o Bees will shiver to keep hives warm • Dinos were probably endothermic – evidence: o Mei long, duck-sized dinosaur preserved in sleeping pose o Bird tuck their head into their feathers to keep warm – critical for endothermic organisms o Dinosaur features incl. sharp teeth and clawed hands o Bird features incl. a large eye socket and a long and thin forearm (radius) o Discovered in 2004

THERMOREGULATION Mechanisms to maintain optimal body temperature • Behavioral o orientation relative to heat source, basking, huddling & varying contact with heat surface o moving locations throughout day o eg a lizard maintains its body temperature between upper and lower limits by moving between hot and cold microhabitats. o Eg huddling penguins • physiological o too hot: increase blood flow to periphery, sweating (evaporative cooling), panting o too cold: decrease blood flow to periphery, shiver o eg counter-current heat exchanger . fast, pelagic fish (sharks, tuna) . heat generated by swim muscles . heat retained in muscles (better for swimming) o eg human thermostat . in hypothalamus . negative feedback system . shiver/sweat • physical o insulation (fur, feathers, fat) o surface area: volume . think ears on artic/desert bunnies o colour

COSTS OF ENDOTHERMY • Insulation o external: feathers, fur o internal: fat layers • cooling systems o heat and water must be liberated for evaporation of sweat, panting… • fuel o lots of food required o ~90% converted to heat, not growth

o lots of O2 needed for cellular respiration . Efficient respiratory & circulatory system . 4 chambered heart in birds and mammals:

RESPIRATION IN BIRDS • Birds have a very efficient respiratory system. o Flying & endothermy demand high amount of oxygen. o Some birds able to fly at high altitudes (30,000’+) o System is much more complex & efficient than mammals . **more efficient use of available oxygen enables flight! • Respiratory system o Unidirectional flow of air through lungs (not tidally like mammals) . No dead air spaces as in alveoli  Moves through parabronchi and air capillaries . Continuous flow of fresh air  Even during expiration

. Can achieve higher maximum O2 concentrations than in other animals o Numerous air sacs (8-9) . Anterior and posterior • Ventilation o Breath 1 . Air is drawn into the (posterior) air sacs . Air is propelled through the lung o Breath 2 . Same air is drawn into the anterior air sacs (still moving though lung) . Same air is propelled out through nares o * it takes 2 cycles for any breath of air to go in and come out

ADAPTATIONS FOR FLIGHT • Better respiratory system • Hollow bones • Sternum enlarged and keeled o Increases SA for attachment of large flight muscles • Feathers o Functions . Insulation . Flight . Sensory structures . Lining nests o Composed of keratin . Derived from scales o Most birds have reptile-like, scaled skin on their legs, rather than feathers • Loss of an ovary • Fusion of forlimb bones • Centralization of body mass

FLIGHT • Evolution of flight o Flight has evolved four times: . Insects . Pterosaurs . Birds . Bats . NOTE: flying is NOTthe same as gliding o . similarities due to common environment not a common ancestor • Two theories on evolution o Ground up – bipedal runner leaping and gliding  flying . Support: Chukars . Poor fliers, use wings to run up trees/inclines o Tree down – aboreal dino  gliding between trees  flying . Support: Microraptor fossil . Shows feather on wings and legs (would impede running) • How do wings enable flight? o object changes air flow pattern and create lift o particles must move faster to get over bump (top) . accelerated flow around an airfoil . create high pressure under wing (lower speed) • amount of lift also influenced by attack angle o but at a really sharp angle, turbulence is created (back eddies) • use Alula o feathers on 1st digit o maintain laminar flow over the leading edge of the wing o as in airplane wing, spoilers decrease turbulent flow

TYPES OF GLIDING/FLIGHT • Soaring o Uses air movements to generate lift and to stay aloft without flapping the wings (wings provide lift and forward motion comes from falling through air) . static soaring  uses updrafts, thermals  jump off high place, use thermals heating ground  circle around updraft . dynamic soaring  uses differences in wind speed  glide downward (away from wind) then wheel into wind and use momentum to gain elevation  high wind speed at higher elevation also creates lift  used by sea birts • Flapping flight o wing movements generate thrust . downstroke:  power to generate thrust  wing moves forward & down . upstroke:  recovery, lift with minimal loss of momentum  wing folds in towards body to reduce drag • Hovering flight o use wing movements to stay at particular altitude (stationary in air) o eg hummingbirds twist their wings –after recovery rotate shoulder joint so dorsal surface pushes backward and downward upon air

LECTURE 20: MAMMALS I REPRODUCTION LECTURE OUTLINE 1. Mammals i. Characteristics ii. Evolution iii. Diversity 2. Reproduction i. Asexual vs. sexual reproduction ii. Hermaphroditism iii. Sexual dimorphism 3. Mammalian reproduction i. Placenta

CLASS Mammalia • ~ 5,000 species o Fewer species than other vertebrate groups • Evolved before birds, 225 mya • 4 defining characteristics of mammals 1. hair o Insulation o Camouflage o Sensory & defense 2. 4 - chambered heart 3. Sweat glands 4. Mammary glands o Milk production • Endothermic • Advanced nervous system • Internal fertilization • Most are herbivores • Differentiation in teeth among mammals reflect varied diets o Unlike reptiles and fish, mammals show heterodonty, different teeth (in same mouth?) specialized for different tasks

AMNIOTE SKULL MORPHOLOGY • Skull morphology is a key characteristic to identify relatedness among amniotes • Key difference between skills is the presence, size and number of temporal fenestrae = holes that provide more SA for muscle attachment • Skull types: o Anapsids . Turtles . Just eye hole and nostril o Synapsids . incl. Therapsids &Mammals . additional lower TF o Euryapsids . extinct marine reptiles . additional upper TF o Diapsids . incl.dinosaurs & birds . two additional TF • Therapsid = early synapsid that gave rise to mammals o Exernal appearance like reptile o Powerful jaws o Teeth are differentiated into frontal incisors for nipping, canines for puncturing and tearing, and molars for shearing and chopping food. o Their legs are positioned more vertically beneath their bodies than are the sprawling legs of reptiles.

MAMMALIAN EVOLUTION • true mammals evolved ~225 mya (Triassic) • Early mammals were small, arboreal, shrew-like insectivores, nocturnal • improvement to middle ear • Middle ear evolution o All mammals have 3 bones in middle ear o Fossils of transitional forms from mammal ancestor show how these bones were derived from elements of jaw joint o Analyses of embryos also shows how two of the three ear bones develop from jaw elements • Mammals did not radiate until extinction of the “dinosaurs” o coexisted with “saurs” o became dominant group upon their extinction(~65 mya) o diversified o filled empty terrestrial & marine niches (large herbivores& carnivores) o return to oceans • Ambulocetus o Ancestor to whales o ~50 mya o ~3 m o ear similar to whales, can hear well underwater o similar teeth to cetaceans • Smilodon o Sabre toothed cat o 1.5 mya  11,000 ya o Contemporary with humans, mammoths and giant ground sloths • Megatherium o Giant ground sloth o Herbivorous o ~2 mya  8,000 ya o elephant sized

REPRODUCTION TYPES • Asexual reproduction o Offspring are genetically similar to the parent o Genetic variation comes from mutation and recombination o Less risky o Less energetically costly o Used when environmental conditions are stable, unchanging • Sexual reproduction o Offspring are genetically different than the parents o Involved the union of egg and sperm o Produces variation necessary for evolution!! used when environmental conditions are variable • Hermaphroditism o Simultaneous hermaphroditism . Capable of producing an egg and sperm at the same point in life cycle . Eg earthworms o Sequential hermaphroditism . Only capable of producing egg & sperm at different points in life cycle . ie: organism changes sex . Clown fish (male  female) and blue-headed wrasse (biggest female  male)

MAMMALIAN GROUPS • Prototherians (Monotremes) o egg laying o egg incubation until hatching • Marsupials o Pouched o early birth, fetus completes development in pouch • Eutherians o Placental o embryo retained in female reproductive tract

PROTOTHERIANS • lay shelled eggs (oviparous) o females lack placenta o incubated by parents • have mammary glands o no nipples, young suck milk from fur • Platypus o Eastern Australia o Use bill to dig for crustaceans and worms o Build nests in river banks o lay 2-4 eggs o hatch ~8 days o nurse 5 months • Echidna (spiny anteater) o New Guinea o short & long nose spiny anteaters o insectivores o sticky tongue o temporary pouch for egg o hatch ~8 days o in pouch, spines form (~3 weeks) o live ~50 years

MARSUPIALS • do not lay eggs o Viviparous, placenta • short gestation, long nursing period • birth after short internal development • newborns crawl over mother’s body to pouch o attach to nipple in pouch o Complete development • ~350 species o kangaroos, koalas, opossums • N & S America, Australia o Most of NA marsupials extinct o Only one opposum • Tasmanian Devil o Largest marsupial carnivore o Scavengers o Found only on Tasmania • Evolution o Diverged from early placentals ~100mya o Sister group to Eutherians

EUTHERIANS • 94% of species • Viviparous o no pouch or shelled egg • Amniotic egg retained in female reproductive tract o embryo nourished by mother via placenta • Eutherians often referred to as placental animals, but some marsupials have placentas

PLACENTA • Organ formed by the embryo & mother after implantation o formed by extra embryonic membranes & uterus lining of mother o site of gas, nutrient, & waste exchange between mother and embryo o produces hormones necessary to maintain pregnancy • Consequences of a placenta o yolk not needed . nutrients come from mother o waste is not accumulated . urea & other wastes are transferred to & disposed of by mother . no uric acid; it’s insoluble o only one pregnancy is possible at a time . estrogen & progesterone produced by placenta have negative feedback on hypothalamus preventing ovulation

REPRODUCTION AND DEVELOPMENT • ovulation = release of egg(s) from ovaries o Day 14 after first day of menstruation (humans) • small egg o no yolk supply, but empty yolk sac retained • fertilization occurs in oviduct o zygote travels to uterus • A species-specific protein in the zona pellucida binds a sperm and triggers the acrosomal reaction o Enzymes at sperm head digest ZP and enter ovum o Fusion of egg and sperm cause egg plasma membrane to harden, preventing additional sperm to penetrate • Mammalian cleavage o Cleavage occurs in oviduct and produces a blastocyst . Inner cell mass (Hypoblast & Epiblast)  embryo . Trophoblast (chorion – aka outermost membrane surrounding an embryo) contributes to the formation of a placenta • Implantation o blastocyst implants in endometrium (lining of uterus) . at ~6th days after fertilization (humans) o embryonic chorion secretes hormones . indirectly inhibits ovulation & maintains endometrium . ex: human chorionic gonadotropin (hCG)  presence detected in pregnancy tests o if no implantation, no hormones… . menstruation will occur • Placenta Formation o Both mother’s uterine lining & extraembryonic membranes contribute to placenta o chorion proliferates . chorionic villi invade uterine wall . Together with maternal tissue forms placenta . site for “chorionic villus sampling” o allantois develops and forms blood vessels . form umbilical arteries and vein . . ~Day 40

• Placental Blood supply o 3 fetal blood vessels in umbilical cord

. 2 arteries carry deO2 blood to mother (AWAY from fetus)

. 1 vein carries O2 blood towards fetus . NOTE: in adults, arteries carry oxygenated blood AWAY from heart o Substances pass between mother and fetus by diffusion . Two separate blood systems . No mixing of blood cells or plasma! • Molecular movement across the Placenta o Small molecules move via diffusion

. O2 and CO2  fetal hemoglobin has a higher oxygen affinity than adult hemoglobin  thus oxygen moves to the fetus . Urea . Nutrients (sugars, vitamins, minerals…) . Hormones . also: alcohol & drugs (caffeine, cocaine, etc.) • HUMAN Development o Gestation = 9 months o 1st trimester (months 1-3) . rapid growth & development . large hormonal changes  “morning sickness” . sex differentiation . week 4 – heart beats . ~ 3 inches o 2nd trimester (months 4-6) . now considered a “fetus” . limbs elongate & first movements felt by mother . ~ 1 foot long o 3rd trimester (months 7-9) . Internal organs mature  Eg brian undergoes sleep/wake cycles  Kidneys produce urine • LABOUR and birth o oxytocin triggers uterine contractions . causes cervix to dilate o fetus emerges from amniotic sac . “water breaks” . emerges through the vagina (birth canal) o just when you thought you were done… . placenta detaches from uterine wall . shed as “afterbirth”

LECTURE 21: MAMMALS II PRIMATES, HOMINID EVOLUTION, CENTRAL NERVOUS SYSTEM Humans have a very large brain/body size ratio – also have a high degree of convolution in the cerebral cortex, further increasing potential for intelligence

LECTURE OUTLINE • Primates o Characteristics o Diversity o Hominid Evolution • Mammalian Nervous System o Central nervous system o Periferal nervous system

PRIMATES • Two main groups o Prosimians o Anthropoids

PROSIMIANS • -Mostly arboreal & nocturnal • Once found on all continents, but now just Madagascar & SE Asia • Lemurs in Madagascar have radiated, not all found in trees and some are diurnal • many species are threatened or endangered • The Loris species was thought to be extinct since1939, but recently seen

ARTHROPOIDS • Tarsier o Among smallest primates o Only entirely carnivorous primates o Only found in S.E. Asia, but fossils found in Asia, Europe, and North America • New World vs. Old World Monkeys o Prehensile tail . = tail used to grasp/hold objects . not present in Old world monkeys . Present in most New world monkeys o New World monkeys also have flat noses & tend to be arboreal • Gibbons, Orangutans and African Apes o Lack tails o Gibbons (aka lesser apes): smaller than other apes, mostly arboreal o Orangutans: too large to cross from one tree to another by the branches and must go down to the ground and walk between them o African Apes (incl. gorillas, chimpanzees, and hominids) o The biggest difference between a monkey and an ape is apes have larger brain/body ratio

HOMINIDS

• Bipetal advantages o A bipedal habit is energetically more efficient than a quadrupedal habit o Forelimbs free to carry things while walking o Head elevated and thus can use eye to spot predators and prey at a distance

HOMO FLORESIENSIS • Homo sapiens thought to be the sole hominids to in habit earth in the last 30,000 years o But on Flores, Indonesia found fossil, survived until 17,000 YA • In 2009, fossils of Ardipithicine ancestor uncovered dating back 4.4 mya • Fossils suggest that organism walked upright and didn't use her arms for walking, as chimps do, yet retains a primitive big toe that could grasp a tree like an ape

AUSTRALOPITHECUS • All extinct • Brains ~35% size of modern human brain • Australopithecus afarensis o “Lucy” 3.5 MYA from Ethiopia, most complete skeleton. o provided evidence that bipedalism evolved before brains fully evolved

EARLY HOMO SPECIES • Homo habilis o “handy/skillful” o in Africa, 2.5-1.5 MYA o first tool use 2 MYA. o Shorter jaw, bigger brain • Homo erectus o “standing” o Believe to be first hominid to leave Africa (spread to Eurasia) o 1.6 MYA – 250,000 YA o first fire use

LATER HOMO SPECIES • Homo neanderthalensis o discovered in Neander valley, Germany o coexisted w/ H. sapiens o disappeared ~30,000 YA, possibly due to extermination by H. sapiens o short, stalky but powerful build o brains larger than H. sapiens • Homo sapiens o ~0.2 MYA also arose in Africa o also spread out of Africa across Eurasia and to rest of world o Larger brains than earlier Homo species, favoring increasingly complex social life

CENTRAL NERVOUS SYSTEM • Central Nervous System (CNS) o dorsal, hollow tube of nervous tissue o large cephalic ganglion (brain) o long tube inferior to it (spinal cord) o Both brain and spinal cord protected by bone • Peripheral Nervous System (PNS) o system of lateral nerves o cranial nerves from the brain spinal nerves from the spinal cord