Comparative Anatomy- Exam #1

Why study vertebrate anatomy?

• morphological adaptations

• evolutionary insight

• economics

  • agriculture

• medicine

What is the phylum and subphylum of vertebrates?

• phylum: chordata

• subphylum: vertebrata

What are the current and past characteristics of phylum chordata?

• endostyle

• update: pharyngeal slits

  • now an ancestral trait

  • genes for gill slits much earlier than previously thought

  • not a chordate feature anymore

What is the endostyle and the function in chordates?

• groove in the pharynx

• functions:

  • secretes mucus for trapping food

  • becomes thyroid in later vertebrates

What are the characteristics of the subphylum vertebrata?

1. vertebrae

2. cranium

Are hagfish craniates or vertebrates?

they are now considered true vertebrates

What is systematics? What method is used?

• study of the evolutionary relationship among organisms

• method = cladistics

  • determines groups of organisms based on evolutionary history regardless of their overall similarity

What is cladistics?

• method of systematics

• objective: to create monophyletic groups

• creates groups based on shared derived characters, not ancestral characters

What is a monophyletic group?

an ancestor and all of its descendants

What is a derived character?

newly evolved from previous state

Where is the outgroup located on an evolutionary tree?

always on the bottom

What is an example of an ancestral trait and an example of a derived trait among frogs, mammals, and fishes?

• ancestral: 1 frog, 2 mammals, and 1 fish all have vertebrae

• derived: only mammals have hair

Can the absence of a character determine a group?

NO!

Describe cladistic grouping.

1. no taxonomic groupings

   • ex: no classes or families

2. old groups not recognized because of monophyletic groups

What is a paraphyletic group?

group with a common ancestor but some descendants are excluded

Is the bottom or top of an evolutionary tree the oldest?

the base (bottom)

What are sister groups? Give an example.

• a group of organisms most closely related to another group

  • share same branch of tree

• ex: hagfish and lamprey

What are the 4 groups that fall under Chordata?

1. cephalochordata = lancelets

2. olfactores

3. urochordata

4. vertebrata

Describe the general features of cephalochordates.

• lancelets

• ~25 species

• marine filter feeders

• dioecious

• defined by 4 chordate derived characters

• general traits:

  • myomeres

  • simple brain

  • caudal fin

• cyrtopodocytes

• lack gill tissue

Define dioecious.

sexes separate

Define myomeres.

muscle blocks separated by connective tissue

What are cyrtopodocytes? In what group can they be found and where in the body?

• found in cephalochordates

• excretory cells (remove metabolic waste from blood)

• found in pharynx- attached to capillaries

  • glomerulus: network of capillaries

    • flushed out with water

• transfer wastes to atrium

• ventral to dorsal blood flow through pharyngeal bars

  • blood connect @ sinus venus

    • sinus = cavity

If cephalochordates lack gill tissue then how do they undergo gas exchange?

diffusion

Describe the circulatory system of cephalochordates.

• no heart

• ventral aorta and bulbilli do most pumping

Describe the digestive system of cephalochordates.

• food → pharyngeal bars → endostyle → gut

  • gut: general word for intestine

• move digestion in cecum → intracellular and extracellular

• water → pharyngeal slits → atrium → atriopore

• egestion

What is egestion?

release of undigested food waste

What are the derived characters of the olfactores?

• molecular similarities

• neural crest cells

  • originate from developing nerve cord

  • move to form other structures

Describe the general urochordata.

• sea squirts

• ~3,000 species

• marine filter feeders

• derived character

  • tunic: protective covering

What is the tunic of urochordates made of?

cellulose or tunicin

Describe the general traits of tunicate adults.

• urochordates

• sessile: attached to substrate and immobile

• lack some chordate features

• monoecious

• circulatory system

  • heart pumps blood in 2 directions

What does monoecious mean?

one individual has both testes and ovaries

Describe tunicate larvae and the importance of the larval stage.

• urochordates

• free swimming

• all chordate features

• short lived and then they settle to the substrate and metamorphase into adult

  • importance of this stage is for dispersal away from sessile parents

Describe the 5 derived characters of subphylum vertebrata.

• ~70,000 species

• derived characters

  1. cranium

  2. vertebrae

  3. 3-part brain

     • better processing and motor control

  4. neurogenic placodes

     • cell clusters- give rise to sensory organs

  5. muscular pharynx and gut

     • gill arches support

     • gill filaments

What is the importance of the muscular gut and pharynx in vertebrata?

1. muscular pharynx → pump water through pharynx to increase gas exchange efficiency

2. muscular gut → move food efficiently through different parts of digestive tract

   • peristalsis: contractions and movement of food

What are the general traits of vertebrata?

1. duplication of Hox genes

   • regulate genes that control embryonic development

2. inner ear- made of semicircular canals

   • function: balance and equilibrium

Draw the evolutionary tree of phylum Chordata as well as list the derived characters.

Describe the “Agnathans”

• shared ancestral characters

• agnatha: without jaws

• jawless fishes

• ancestral traits:

  • lack jaws

  • lack 2 paired fins

• gametes released into coelom

What are the groups that fall under “agnathans”

• cyclostomes = lampreys and hagfish

  • myxiniformes = hagfish

  • petromyzontiformes = lampreys

• ostracoderms

  • extinct

What does the quotations around “agnathans” mean?

not a true monophyletic group

Describe the general traits of cyclostomes and the subgroups.

• agnathans

• lampreys and hagfish

• derived characters:

  • single nostril and nasal sac

  • linguinal cartilage supports “tongue”

    • tongue isn’t homologous to tongue of other vertebrates

  • velum: pumps water or food into pharynx

• includes the groups:

  • myxiniformes

  • petromyzontiformes

Describe the myxiniformes (i.e. number of species, location, derived characters, general traits)

• agnathans under the cyclostome group

• hagfish

• ~75 species

• all marine

• benthic, deep water

• burrow into sediment

• derived character

  • slime glands

    • ~200 along body

    • secrete massive amounts of mucus

    • deters predators

• general traits

  • vertebrae = arcualia

    • ventral elements

  • gill pouches- many

    • 1-15 pairs gill openings

    • most common species only have 1 pair external gill slits

    • all pouches drain through internal ducts that combine and exit out opening

  • 1 pair semicircular canals

Describe the petromyzontiformes ((i.e. number of species, location, derived characters, general traits, diet and feeding)

• agnathans under the cyclostome group

• lampreys

• ~40 species

• marine and freshwater

• anadromous

• larvae are filter feeders

• derived characters:

  • round mouth with buccal funnel

  • 7 pairs of gill pouches

    • each opens to outside

  • tidal ventilation: water in and out gill openings

    • inefficient

    • use because they are parasites and use buccal funnel to attach to hosts so this lets them feed and respire at the same time.

• general traits

  • vertebrae = arcualia

    • dorsal elements

  • well developed eyes

  • 2 dorsal fins

  • 2 pairs semicircular canals

• diet and feeding

  • adults- parasite on fish

  • buccal funnel and tongue- keratinized teeth

Describe the “ostracoderms”† (i.e. number of species, derived characters, basic traits)

• agnathans

• extinct (hence the †)

• small freshwater and marine fish

• derived characters

  • dermal bones- plates

  • paired fins

    • pectoral and dorsal

  • paired nostrils

Draw the “agnathan” evolutionary tree and include derived characters.

What does Gnathostomata mean?

• jaws opening

• jawed fishes

What are the subgroups within Gnathostomata?

• placoderms (extinct)

• Chondrichthyes- cartilaginous fish

• Osteichthyes- bony fish

Describe the placoderms.

• extinct

• members of gnathostomata

• jaws

  • important for:

    • catching prey

    • breaking down food and manipulating prey

    • defense

    • build nests

  • paired pelvic fins

  • 3 pairs semicircular canals

What is the difference between ostracoderms and placoderms?

• ostracoderms- older, no jaws

• placoderms- newer, jaws

Describe the Chondrichthyes (i.e. group they are a part of, general traits, derived characters, subgroups).

• part of gnathostomata

• cartilaginous fish

• derived characters:

  • scales = placoid

  • pelvic claspers in males

    • function: internal fertilization

  • specialized calcification of cartilage

• general traits:

  • cartilaginous skeleton

    • mineralization secondarily lost

  • increased buoyancy

  • jaws and vertebrae = calcified

  • series of replacement teeth

    • tooth only attached in skin so fall out easily

• subgroups

  • holocephali- ratfishes

  • elasmobranchii- sharks, skates, reys

Describe the holocephali (i.e. number of species, derived traits, part of what groups)

• gnathostomata → chondrichthyes → holocephali

• ratfishes

• ~50 marine species

• derived traits:

  • 1 pair gill openings

    • covered by fleshy operculum

  • palatoquadrate fused to cranium

    • palatoquadrate = upper jaw

      • holostylic jaw suspension

Describe the elasmobranchii (i.e. number of species, derived traits, part of what groups, what is special about them)

• gnathostomata → chondrichthyes → elasmobranchii

• sharks, skates, reys

• derived traits:

  • separate, uncovered gill openings

  • hyostylic jaw suspension

    • only anterior palatoquadrate attached to cranium

    • will allow some upper jaw flexibility

• ~1250 species

  • mostly marine

• predators- vertebrates and invertebrates

• largest filter feeders

Describe the Osteichthyes.

• in gnathostomata

• bony fish

• derived characters:

  • swim bladder: adjusts buoyancy

  • dermal rays in fins

• subgroups:

  • actinopterygii: ray-finned fishes

  • sarcopterygii: lobe-finned fishes

Describe actinopterygii.

• Gnathostomata → Osteichthyes → Actinopterygii

• >34,000 species

• all aquatic niches

• derived characters:

  • multiple radial bones support fin

  • forebrain develops by folding outward

Describe sarcopterygii.

• Gnathostomata → Osteichthyes → Sarcopterygii

• ~8 species

• lobe-finned fishes

• mostly freshwater

• lungfishes - air breathers

• coelocanth- marine

• derived characters:

  • muscular lobes at fin base

  • single series of bones support fin

Draw the Gnathostomata evolutionary tree and include derived characters.

What is the derived character of tetrapoda?

4 limbs with digits

Describe Amphibia.

• ~8300 species

• aquatic or semi-aquatic

  • respiration and reproduction

    • need water for reproduction because it prevents the eggs from desiccation

• amphibia = double life

  • have adult and larval stages

• groups:

  • caecilians

  • salamanders

  • frogs and toads

• derived characters:

  • pedicellate teeth

    • 2 parts- base and crown

    • tooth joint

    • flexible

    • aids in handling prey

  • thin skin

  • mucuous glands

    • moist skin for respiration

      • moist because gasses diffuse in/out water into blood

Describe the amniotes.

• tetrapoda

• derived character: amniotic egg

• amniotic systematics- skulls and temporal fenestrae

• groups:

  • synapsida- mammalia

  • sauropsida- “reptiles” and birds

  • testudina- turtles

  • archosauria

  • crocodilia

  • aves

Describe the amniotic egg.

• = yolk sac + 3 new extraembryonic membranes

  • yolk sac stores nutrients

  • amnion and chorion = fluid filled sacs that absorbs shock and prevents desiccation

  • allantois: stores nitrogenous waste

  • allantois and chorion will fuse and become highly vascularized (lots of capillaries)

    • together they function in gas exchange

• importance of amniotic egg:

  • can reproduce on land

  • embryo can grow larger with better oxygen supply

Describe the different skull types in amniotes.

• anapsid = no fenestrae

• 1 fenestra = synapsid

• diapsid = 2 fenestrae

• function:

  • increased surface area for jaw muscle attachment and more space for larger jaw muscles

  • allow different orientation of jaw muscles to improve jaw muscularies

Describe the synapsida.

• tetrapoda → amniota → synapsida

• mammalia

• derived characters:

  • synapsid skull

  • hair

  • mammary glands

• ~5500 species

• new physiology trait: endothermy

  • endothermy: regulate body temp through production of metabolic heat

Describe sauropsida and the subgroups.

• tetrapoda → amniota → sauropsida

• “reptiles” and birds

• derived traits:

  • beta keratin in skin

  • uric acid waste product

  • diapsida

    • lizards → birds

    • diapsid skull (derived)

    • ophiodiophobia: fear of snakes

  • lepidosauria

    • derived characters:

      • overlapping scales of keratin

      • transverse cloaca

      • squamata

        • derived traits:

          • hemipenes

          • paired male copulatory organs

          • sperm groove

        • lizards and snakes

          • ~11,000 species

          • swalloq prey bigger than their mouth

          • some secondarily lost limbs

Draw the early tetrapoda evolutionary tree and include derived characters.

Describe the testudina.

• tetrapoda → amniota → testudina

• turtles

• derived characters:

  • loss of diapsid skull

    • anapsid

  • shell: keratin and bone

• ~350 species

• terrestrial → marine

Describe the archosauria.

• tetrapoda → archosauria

• derived characters:

  • antorbital fenestra

  • triangular shaped orbit

Describe crocodilia.

• tratrapoda → crocodilia

• 24 species

• fresh and saltwater

• complete secondary palate = derived character

  • an oval structure separating the oral and nasal cavities

  • allows them to breathe with food in mouth

    • often drown their prey

Describe aves.

• tetrapoda → aves

• birds

• ~10,000 species

• endothermic

• derived characters:

  • feathers

  • hollow bones

  • air sacs

What group of tetrapods has the most species?

squamata

Draw the sauropsida evolutionary tree.

What is integument? Describe the basic structure.

• interface

• all surfaces, including:

  • ears

  • eyes = conjunctiva

    • conjunctivitis = pink eye

• basic structure:

  1. epidermis

     • multilayered and contains glands

     • continuous cell division

       • why? repair damaged cells and replace dead cells

  2. dermis

     • connective tissue

     • blood vessels and nerves

     • makes leather

Describe the non-living coverings of the epidermis.

1. mucus cuticle

   • thin coat continually secreted

   • aquatic species

   • function:

     • moisture

     • anti-bacterial properties

     • defense

       • ex: hagfish

2. stratum corneum

   • layer of dead cornified cells (infused with keratin and hardens)

     • why? prevents drying out / desiccation

   • waterproof

   • terrestrial vertebrates

Describe epidermis of aquatic vertebrates.

• glands

  • mucus

  • granular

    • mucus

    • chemicals to repel predators

• keratin

  • cyclostomes and tadpoles

  • cornified spines = “teeth”

  • keratin “beaks”

Describe tetrapod glands.

• mucus gland is absent from most (except amphibia)

• amphibia has granular glands

• secrete toxins

  • pheromones: chemicals that affect the behavior and physiology of other animals (ex: courtship and mating)

• bright colors that advertise an animal’s toxicity or distastefulness = aposematism

Describe avian glands.

• uropygial gland

  • secretes oil for feather conditioning

  • prominent in waterfowl

  • for waterproofing mostly

Describe mammalian glands.

1. sebaceous

   • opens into hair follicle

   • produces sebum

     • oily conditioner

2. ceruminous

   • produce cerumen (ear wax)

   • outer ear canal

   • works with hairs in ear canal to capture insects and debris from getting to ear drum

3. sudoriferous (“sweat glands”)

   • watery secretion

   • function: thermoregulation via evaporative cooling

   • distribution varies among mammals

4. scent

   • sebaceous and sudoriferous

   • pheromones

   • ex: cats rubbing on you

   • defense chemicals

     • ex: skunks

   • castoreum: beaver anal sac oil used for rasberry flavoring

5. mammary

   • compound alveolar

   • # related to # offspring

   • produce milk that is high in lipids

Describe tetrapod epidermal scales and how they works specifically in squamates, turtles, birds, and mammals.

• stratum corneum derivative

• thickening of s. corneum

• function: protection against wear

• squamates

  • overlapping with joints

  • 2 layers of s. corneum

• turtles

  • scutes

  • non-overlapping

  • either shed or continually grow

  • shell

    • dorsal side = carapace

    • ventral side = plastron

• birds

  • localized in most

    • mostly on feet

• mammals = rare

  • armadillos

  • beavers (tails)

  • most heavily scaled mammal: pangolin

Describe claws, nails, and hooves.

• s. corneum derivatives

• 'claws- first in amniotes

  • shed and replace in some groups

• nails and hooves- continuously grow and wear down

  • mammals with hooves = ungulate

Describe feathers.

• s. corneum derivative

• structure

  • basic contour feather

    • calamus = “quill”

    • rachi = shaft

    • vane: flat surface composed of barbs

      • plumulaceous barbs: loose and not connected

      • pennaceous barbs: tightly connected into a vane

• feather types:

  1. contour feather

     A. Body- streamlined shape

     B. Flight- stiff, flat surface for lift and thrust

  2. bristle- tactile receptor

  3. filoplume- air receptor

  4. down- insulation

     • no central shaft

  5. semiplumes- insulation, streamlining, mate attraction

• pterylae: feather tracts

  • bare spots between feather tracts = apteria

Describe hair.

• s. corneum derivative

• pelage: dense covering of hair

  • guard hair: protection and create color patterns

  • underhair: tightly packed for insulation

• arrector pili: smooth muscles attached to hair follicles

  • adjust hair position

  • increase ability to trap hair

  • cause goosebumps in humans

What are the differences between horns and antlers?

• horns

  • ex: bison

  • made of keratin (derived from epidermal)

• antlers

  • ex: moose

  • made of dermal bone (from dermis)

What are the different horn types?

1. bovine

   • sheath of keratin covering dermal bone

   • hollow

   • never shed

2. pronghorn

   • branched and sheath sheds

3. hair

   • mass of keratin fibers

   • sits on nasal bone

   • never shed

Describe antlers.

• epidermis

• from dermal bone’

• grow underneath “velvet” integument

  • velvet is from epidermis and dermis

• shed and replace annually

Describe ossicones.

• epidermis

• giraffes have these

• bony core develops separate from skull

• dermal bone core

• covered with skin

• never shed

• function

  • competition?

  • thermoregulation?

  • can’t know for sure

Describe the dermis.

• chromatophores: pigment cells

  • aposematism

• matrix of collagen fibers

  • thick

  • support and protection

  • mineral deposition

  • assist in bone production

Describe the dermis of “ostracoderms” and placoderms

• plates made of dermal bone

  • primitive dermal bone

    • thick and has 4 layers

• composed of:

  1. compact bone

  2. spongy bone

  3. dentin

  4. enamel

     • denticle: projection of dentin and enamel

Describe the types of scales present in the Chondrichthyes.

1. placoid scales

   • bony plate and spine

   • spine = denticle

   • give rise to teeth in gnathostomes

2. cosmoid and ganoid scales

   • both made of spongy (vascular) and compact (lamellar) bone

   • coismoid

     • cosmine (type of dentin) layer under enamel

     • extinct sarcopterygii

   • ganoid

     • lacks dentin

     • different enamel - ganoin

     • primitive actinopterygii

       • ex: Gar

3. elasmois

   • thin layers of compact bone

   • very flexible

   • cycloid

     • smooth all around

   • ctenoid

     • comb-like border

     • sarcopterygii and actinopterygii

Describe the dermal bone of tetrapods (osteoderms, turtle, birds, and mammals).

• compact bone

• osteoderms: small bony scales

  • within dermis- not visible

    • ex: caecilians

  • amphibs

  • crocodiles

• turtle shell

  • dermal plates under scutes

    • fused and immobile

    • fused to ribs and vertebrae

  • lacking in few

    • ex: leatherback, some freshwater turtles

• birds- mostly absent

• mammals- rare

  • dermal armor in armadillos

    • osteoderms in skin

What is the skeleton composed of?

1. mineralized tissue

   • cartilage and bone

2. bundles of collagen fibers

   • tendons: attaches muscle to bone

   • ligaments: attaches bone to bone

     • ex: ACL (anterior cruciate ligament)

What are the two categories of bone?

1. membrane

2. endochondral

Describe membrane bone.

• forms from membranous sheets of mesenchyme

  • mesenchyme: undifferentiated tissue

  • = dermal bone when made in dermis

Describe endochondral bone.

• produced only with cartilage precursor

• also called replacement bone

• growth- ex. long bones

  • 3 growth areas

    • middle of shaft (short lived)

    • epiphyseal plates = 1 at each end

      • cartilaginous

    • process

      • cartilage produced then ossifies

      • bone growth continuous throughout life (=indeterminate)

      • birds and mammals- plates ossify at maturity (= determinate)

What 3 parts make up the axial skeleton?

1. vertebral column

2. ribs and sterna

3. skull

Describe the general properties of vertebrae

• composed of:

  • centrum

  • neural arch

  • apophyses= processes

  • hem arch- tail (fishes)

    • contains caudal artery and vein

• other apophyses

  • chevron bone in amniotes

    • caudal vertebrae

    • homologous to hemal arch

  • zygapophyses

    • articulating facets

    • limit dorsoventral flexion

  • when processes are reduced = increased flexibility

Describe the “agnathan” vertebral column.

• hagfishes and lampreys

• simple rudimentary vertebrae = arculia

Describe the jawed fish vertebral column.

• little specialization

• 2 types of vertebrae:

  • dorsals = trunk

  • caudals = tail

• design allows lateral flexibility only (swim side to side)

Describe the elasmobranch vertebral column (what is present, what kind of centra, arches)

• notochord present

• amphicelous centra = concave at ends

• limited flexibility

• bone never forms

• arches

  • paired cartilaginous plates

    • dorsal plates = neural arch

    • ventral plates = hemal arch

  • elastic ligament

    • connects neural arches

    • limits dorsoventral movement

    • present in all jawed fish

What are the two types of vertebrae present in jawed fishes?

dorsal and caudal

Describe the actinopterygii vertebral column.

• ossified

• amphicelous centra

• supraneural bones

  • may fuse to vertebrae

  • support dorsal fin muscle

Describe the tetrapod vertebrae- centra

1. amphicelous

   • some amphibs and squamates

   • concave at ends

2. opisthocelous

   • concave at posterior

   • salamanders

   • improved flexibility

3. procelous

   • concave at anterior

   • frogs/toads and most sauropsids

   • increased flexibility

4. acelous

   • not concave

   • w/ intervertebral disks in between

   • mammals

   • helps to distribute weight evenly

5. heterocoelous

Describe the regionalization of the tetrapod vertebral column.

• new challenges on land:

  • support large body mass without dense water

  • increased flexibility for locomotion

  • other trends:

    • ribs on thoracic vertebrae only

    • sacral vertebrae support pelvic girdle and hindlimbs

• exceptions:

  • snakes and caecilians

    • most vertebrae have ribs

    • little specialization

    • snakes have the most vertebrae of all vertebrates

      • function in snakes:

        • increased flexibility

        • increased ribs support trunk (axial) muscles