Comparative Anatomy - Midterm I

focuses on evolution of traits

features of chordates

• notochord

• nerve chord (parallel to notochord & gut, develops into a brain)

• embryonic gill slits (feeding & respiration)

• post-anal tail

examples of invertebrate chordates

lancelets & sea squirts

T or F: change from invertebrates to vertebrates led to key innovations

True; vertebrates have a backbone, while invertebrates do not

What did the development of vertebrae and jaws allow in early vertebrates?

Vertebrae improved maneuverability and forceful contractions (led to fast & agile dominant fishes), while jaws supported complex sensory organs and nervous systems.

fossil record order of chordates/ vertebrates:

1. lancelets (cephalochordates)

2. tunicates (urochordates)

3. jawless fish

4. jawed fish

5. chondrichthyes

6. lobe-finned fish

7. amphibians

8. reptiles

9. birds

10. mammals

order of innovations:

1. vertebrate replaced the notochord

2. cephalization (the evolutionary trend where an animal's nervous system, brain, and main sense organs become concentrated at its front end, forming a distinct head)

3. jaws

4. lobe-finned fishes reinforced ventral fins w/ skeletal parts

5. lobe-fins transform into limbs (first tetrapods are amphibians, live their larval stage on water)

6. amniotes lay eggs on land (reptiles abandon embryonic stage in water

7. skin rich in keratin protect from dry land habitats

8. some develop feathers & become birds, good for flying

9. some develop har & mammary glands, become mammals

what tetrapod innovation helped them survive dry environments?

keratinization: the biological process where living skin cells fill with a tough, protective protein called keratin, lose their nuclei, and turn into hard, dead cells that form the outer layer of the skin, hair, and nails

what is the epidermis layer rich in keratin?

strantum corneum (SC)

are the cells in the SC alive or dead?

dead

what are the 4 epidermal scales?

• placoid

• ganoid

• cycloid

• ctenoid

placoid scales belong to:

sharks & rays

ganoid scales belong to & have the key feature of:

gar; these scales are rich in enamel

cycloid & ctenoid scales belong to & have the key feature of:

bony fish; lamellar bone (noncalcified)

what are the 2 layers of the skin?

dermis & epidermis

what are the main integument features of fish?

rich in glands & no SC

what are the main integument features of amphibians?

no dermal scales & abundant glands

what are the main integument features of reptiles?

few glands, thick SC, epidermal scales, & dermal structures such as armor (alligators), gastralia (alligators), dermal bones (turtles) and scutes (snakes)

what are the main integument features of birds?

few glands, dermal scales absent, few epidermal scales (legs & beak)

T or F: feathers are non-vascular & non-nervous

true

what are the 3 types of feathers?

• contour

• down

• filoplume

what is the function of a contour feather?

flight (ex] eagles, etc)

what is the function of a down feather?

insulation (ex] penguin)

what is the function of a filoplume feather?

display (ex] peacocks)

what are the main integument features of mammals?

SC, developed hair, & glands

what are the 3 divisions of the skeletal system?

cranial (skull), axial (main central skeleton), & appendicular (girdles & appendages)

what are the 3 parts of the cranial skeleton?

chondrocranium, splanchnocranium, & dermatocranium

what is the function of the chondrocranium?

underlines & supports brain

how does the chondrocranium develop?

begins as cartilage that fuses & ossifies during embryonic development

what happens to the chondrocranium in sharks & rays?

stays as cartilage throughout their entire lives

what does the chondrocranium become in most vertebrates?

occipital, sphenoid, & ethmoid centers

where does the splanchnocranium orginiate?

arises from pharyngeal slits

what does the splanchnocranium become?

jaws of sharks, hyoid bone, & inner ear bones in humans

what structures make up the dermatocranium?

roof & lateral walls, jaws & palate bones, & opercular bone in fish

in which vertebrate group is the dermatocranium absent?

chondrichthyes

what are fenestrae?

openings in the outer dermatocranium

how many fenestraes do anapsids have?

none (ex] turtles)

how many fenestraes do diapsids have?

2 fenestrae (ex] tuatara)

how many fenestraes do modified diapsids have?

2 fenetrae, but one is imcomplete (ex] lizard, chameleon, birds)

how many fenestraes do synapsids have?

1 fenestrae (ex] humans)

how many types of vertebrae do fish have?

2: abdominal & caudal

do fish have cervical vertebrae?

no

why can’t fish move their heads sideways?

due to no cervical vertebrae

what vertebrae appeared first in amphibians?

cervical vertebrae

what vertebare do amphibians have?

cervical, dorsal, sacral, & urostyle

what special vertebrae do reptiles have?

atlas & axis

what do the atlas & axis allow reptiles to do?

make more complex head movements as its a combination of cervicals

what vertebrae do reptiles have?

thoracic, sacral, dorsal, caudals, cervical

how many cervical vertebrae do birds have?

13 to 14 cervical vertebrae

what happens to the thoracic vertebrae in birds?

they’re fused

what is the fused structure in birds called?

synsacrum

what happens to the caudals in birds?

they remain free, with a pygostyle

what vertebrae do mammals have?

cervical, thoracic, lumbar, sacrum, caudals

what happens to the caudals in primates?

they have a fused coccyx

do agnathans have ribs?

no

what types of ribs do bony fish have?

ventral & dorsal

what are amphibian ribs like?

flat ribs that do not reach the sternum

what do birds have on their ribs?

unicate processes

what are uncinate processes?

flat processes extending posteriorly off the ribs

what are mammalian ribs called?

true ribs

where do mammalian true ribs connect?

sternum

which vertebrates have no ribs?

agnathans

which vertebrates have ventral & dorsal ribs?

bony fish

which vertebrates have ribs that reach the sternum?

mammals

the sternum is strictly a ________ structure, & is poorly formed in ________

strictly a tetrapod structure, poorly formed in amphibians

what are gastralia?

rib-like structures extending along the belly in alligators

what are the two girdles of the appendicular skeleton?

pectoral & pelvic

what is the appendicular skeleton made of?

girdles & appendages

what are the major forms of appendages?

limbs & fins

what are chonfrichthyan fins supported by?

kerantinized rods

what supports dins in bony fish?

cartilaginous or ossified rods

which fish show pectoral & pelvic girdles adapted for land transition?

lobe-finned fish

what does the pectoral girdle (scapulocoracoid (scapula)) attach to?

humerus in the upper limb

what bones make up the pelvic girdle?

illium, ischium, & pubis

where does the pelvic girdle attach to?

femur in lower limb

what bones make up the manus?

humerus, ulna, radius, carpals, metacarpals, & phalanges

what bones make up the pes?

tibia, fibula, tarsals, metatarsals, & phalanges

what are amniotes?

a group of tetrapod vertebrates—specifically reptiles, birds, and mammals—whose embryos develop inside a protective, fluid-filled membrane called the amnion

what is the difference between cephalochordates & urochordates?

cephalochordates: have the notochord from head to tail

urochordates: has notochord only in tail