Chordates, pt 2, p. 1
CHORDATES
CLASS PETROMYZONTIDA
lampreys (pp. 320-322)
Jawless, 7 gill slits, no paired appendages, cartilage
In adult: notochord persistent, no vertebrae present
but in Vertebrata due to cranium
There are both marine and freshwater species
LIFE CYCLE
Juvenile forms burrow in mud & sand, feed on detritus
most are freshwater at this stage
this stage lasts 3-17 years
About 1/2 of species are parasites as adults
rest do not feed as adults - spawn and die
migrate to ocean & attach onto various other fish
attach onto host and rasp on skin, eventually drop off
Adults finally return to freshwater to spawn (lay eggs)
NOTE: One species, sea lamprey has become "landlocked" in Great Lakes
has had great negative effect on trout
CLASS CHONDRICHTHYES
cartilagenous fish, including sharks, rays, & chimeras (pp.322-325)
Jaws, cartilage, vertebrae, paired fins, placoid scales
Most species are sharks or rays
predaceous fish with 5-7 pair gill slits
spine associated with the dorsal fins
the mouth is located ventrally (rather than terminal)
teeth are modified placoid scales produced in a series on inside mouth
slowly grow forward and shed
new set grow from inside jaw area
Chordates, pt 2, p. 2
SHARKS elongate tubular body
asymmetrical heterocercal tail (upper half larger)
active swimmers, many must be moving to breath, swim by waving body side-to-side
catch prey using olfactory gland rather than eyesight
RAYS flattened body with vary enlarged pectoral fins = front paired appendage fins
tail very long (as much as rest of body)
swim through waves of pectoral fins
typically bury in sand & wait for prey, eat molluscs, crustaceans, small fish
NOTES
major concern to walk in shallow water at ocean
can step on stingray as the dorsal spine will puncture into foot, should walk by shuffling
feet
Electric ray also of concern
dorsal muscles modified into electric organs to produce a shock
CLASS OSTEICHTHYES
bony fish (pp. 325-330)
Bony skeleton, gills slits with operculum cover, overlapping scales
The caudal (tail) fin is symmetrical
Many have a swim bladder for buoyancy (gas filled chamber)
fish are same density as surrounding water
Operculum allows for breathing w/o moving
water in mouth, past gills & out operculum
Two groups developed based on fin anatomy:
Ray-finned fishes (16.15, p. 327)
largest group and greatest diversity of forms
homocercal tail (no finger-like projection, symmetrical)
fins supported by bony spikes (w/o finger projections)
scales thin
Chordates, pt 2, p. 3
Lobe-finned fishes (fig 16.19, p. 329)
few species, including the lungfish & coelacanth
diphycercal tail (pointed thickened tail)
muscular lobes on fins (like fingers)
heavy enameled scales
The above two groups have recently been split into their own Classes
Ray-finned fish = Class Actinopterygii
Lobe-finned fish = Class Sarcopterygii
SCALES (fig 16.13, p. 327)
a) ganoid: thin diamond-shaped plates
b) cycloid: uniform circular development from a point
close to circular shape
c) ctenoid: uneven radial development
comb-like projections to side (reduce drag in swimming)
d) many catfish lack scales
REPRODUCTION (p. 330)
Wide variation in reproductive methods, but all have separate sexes
Most have external fertilization & development = oviparous (fig 16.29)
a) release eggs & sperm into open water (couples unknown)
b) lay eggs on bottom (known couples)
Some have internal fertilization & development = ovoviviparous (fig 16.30)
have "live" young born
Sea horses are unusual form of ovoviviparous - the male cares for eggs & gives birth
CLASS AMPHIBIA
amphibians, including frogs, toads, salamanders (pp. 346-354)
Tetrapods (4 legs), gelatinous egg covering, 3-chambered heart
Amphibian development is well known (figs 17.7 and 17.16):
egg laid in water
hatch into larval forms or tadpoles with gills
Chordates, pt 2, p. 4
lungs and leg develop, tail stops growing with time
adults come out of water
Variations in developmental pattern seen:
some remain in water w/ gills: mud puppy, & few salamanders
Heart is 3-chambered: interesting circulation
atrium is separated into two distinct chambers
blood circulation: body  right atrium & ventricle  lungs  left atrium & ventricle
the two atria contract at the same time
blood moves to & through ventricle – doesn't mix much
oxygen rich blood goes out to body, oxygen-poor blood goes to lungs
Variation in respiration mechanisms:
gills for aquatic forms
lungs on terrestrial forms
through skin (diffusion) on all forms
Breathing in frogs unusual: have lung and mouth pouch
1) suck air into mouth through nostrils
2) close nostrils and force air into lungs
3) pull air into & out of mouth several times (an alternate mechanism to get oxygen)
4) contracting of body wall to expel air from lungs (this is method to obtain most oxygen)
most carbon dioxide lost through diffusion out skin
Three distinct groups of amphibians:
Caecilians - snake-like with no visible appendages (p. 346)
most species lack eyes
food of small animals
most are tropical; are either aquatic or live in burrows
Salamanders - have similar front & back legs, a tail (pp. 347-349)
are carnivorous: eat worms, small arthropods
greatest diversity is in North America
Frogs and toads - have much longer back legs, no tail (pp. 349-354)
tadpoles are herbivorous, adults carnivorous, largest can eat rats!
Chordates, pt 2, p. 5
found throughout world
frogs & toads are not easily separated - typical: frog in water, toad terrestrial
CLASS REPTILIA
reptiles, including: snakes, lizards, turtles, crocodiles (pp. 352-354)
Tetrapods (4 legs), leathery egg covering, 3-chambered heart
Characteristics to separate from amphibians (pp. 344-346):
1) lungs more efficient as only mechanism for breathing
reptile suck air into lungs, not force as in amphibians, do so by enlarging pleural cavity or
expanding rib cage
(no diaphragm present)
no larval stages with gills
2) tough, dry, scaly skin
offers protection against desiccation & physical injury
thin epidermis which is shed regularly
well developed dermis with pigmented cells (chromatophores)
scales are of keratin (derived from epidermis)
3) egg shell with food and protective membrane
allows for protective development on land
4) jaw better able to grip and/or crush
designed for quick closure -- larger and longer
amphibian only good to grab
5) reptiles have a more efficient circulatory system and higher blood pressure
left & right atrium completely separated
left & right ventricles incompletely separated, but mixing minimal
6) reptiles have efficient strategies for water conservation
a) presence of metanephric kidney (w/ own drainage - ureter)
b) nitrogenous wastes are uric acid (highly concentrated)
c) salt glands near nose or eyes
7) nervous system more complex
even with small brain, cerebrum is relatively large
Chordates, pt 2, p. 6
Three major groups of reptiles:
Turtles
bony case of dorsal carapace + ventral plastron (shell)
beak rather than teeth
tongue not extensible
Snakes & lizards
skin of scales or plates
teeth present, jaw with diapsid anatomy (allows to open wide)
tongue extensible
Separation of lizards & snakes:
snakes generally lack pectoral and pelvic girdles
snake vertebrae shorter & wider (allow for undulations)
snakes lack a movable eyelid (but have a permanent transparent eyelids)
Crocodiles (and others)
skin of scales or plates
teeth present, jaw without diapsid anatomy
tongue not extensible
also: 4-chambered heart
CLASS AVES
birds (pp. 376-397)
2 legs + 2 wings, calcareous egg covering, 4-chambered heart
Other important characteristics (p. 377):
body covering: body of feathers; legs of scales
forelimbs modified to wings (or fins?), most species can fly
beak with no teeth
endothermic (body temperature by metabolism) - previous others exothermic
females with only left ovary developing
eggs with much yolk and hard calcareous shell
Flight made possible by:
wings present - flattened structures to catch air movement
Chordates, pt 2, p. 7
sternum with keel for attachment of flight muscles
bones pneumatized (full of air cavities)
presence of air sacs - extensions of lung into abdomen
up to 75% of air bypasses the lungs as breathing in
flows through lungs on way out (more efficient)
Migration common among many species
summer nesting grounds, take advantage of abundant food in summer
winter feeding migrate to other suitable site
(summer grounds with very little food during winter)
Arctic tern with pole to pole migration!
Types of annual migration patterns
* permanent resident - here year round
* summer resident - migrate here to breed during warm months
* winter resident - summer breeding somewhere else, typically further north
* summer or winter visitor - present during only part of year, eg. ocean birds
* spring and/or fall transient - moving through during migration
* accidental - strange presence on a very erratic basis
Small species use songs for two reasons
1) warns other males away
2) attracts prospective females
Once female attracted male will display additionally to keep female, including: songs, plumage
displays, dances, acrobatic flights
Classification and Identification:
Superorders:
* flightless birds with vestigial wings & stiff palate (ostrich, emu, kiwi)
* birds with well developed wings (including penguins) and flexible palate
Orders:
Large number of orders - at least 20 in eastern North America
Orders are separated by bill shape (feeding), foot shape, size & other characteristics
Chordates, pt 2, p. 8
CLASS MAMMALIA
mammals (pp. 400-421)
Dermal covering of hair on most, internal fertilization & development, 4-chambered heart
Additional characteristics (p. 406):
integument with sweat, scent & mammary glands
diphyodont teeth (milk & permanent)
movable eyelids & fleshy ears
endothermic (heat from own metabolism)
homeothermic (maintain body temperature = warm blooded)
Dermal coverings (all have a hair or it's derivative):
Pelage (fur)
a) dense & short hair - for insulation (can be shed)
b) coarse longer hair - for protection & coloration
Vibrissae (whiskers) - sensory hairs
Nails, claws & hooves - very dense on appendage tips
Variation of appendages:
tetrapods terrestrial - 4 legs
aquatic with modified to fins
bats with webbings on front appendages - wings
2 legs & 2 arms - can walk erect
Reproductive patterns (pp. 411-412):
also the three major subdivisions of mammals, recognized at level of infraclass
Monotremes (duck-billed platypus & spiny echidna)
egg-laying, hatch early & feed off mothers milk
Placentals (cat, dog, human)
long development in uterus, birth, short lactation
Marsupials (kangaroo, opossum)
short development in uterus, birth, long lactation
have a pouch in which development occurs
Chordates, pt 2, p. 9
Infraclass Ornithodelphia – monotremes
Egg laying mammals
Include: duck-billed platypus, echidnas (spiny anteater)
Development:
embryos develop for 10-12 day in uterus
leathery shell is secretes around embryo
eggs hatch in 10-14 days
young obtain milk from mother, but no nipples are present
Infraclass Metatheria – marsupials
Numerous animals in this group, including four orders:
opossums (80+ species) – Americas
marsupial mice – Australia & Tasmania
bandicoots – Australia & Tasmania
koalas, wallabies, kangaroos – Australia & Tasmania
The pouched mammals:
the developing embryos do not implant in the uterus
cause development of shallow depressions in uterine wall
absorb nutrients through a vascularized yolk sac
gestation (time in uterus) is short
followed by a prolonged development in a sac where they lactate for a long time
Chordates, pt 2, p. 10
Infraclass Eutheria – placentals
Viviparous mammals:
embryos do implant in uterus for a prolonged period
a placenta develops for embryo attachment in the uterus
time varies (21 days in rabbits to 22 months in elephants)
The Placentals have been divided into a number of Orders (pp. 418-420):
Shrews and moles – small body, elongate snout, limbs pentadactyl, teeth primitive
Bats – wings, limb bones greatly elongated, claws on only first two digits of front limbs,
hind legs pentadactyl, use of echolocation
Primates (lemurs, monkeys & humans) – enlarged cerebral hemispheres, limbs with ball
& socket articulation, pentadactyl digits (opposable thumb)
Edentates (anteaters, armadillos & sloths) – At least some front claws enlarged (for
digging or hanging), teeth reduced (peg-like) or absent
Rabbits & hares – tail short or vestigial, ears medium to large, 4 upper incisors (front
teeth for biting)
Rodents (mice, rats, beavers, squirrels) – 2 upper incisors which permanently grow,
canine teeth missing
Carnivores (dogs, wolves, fox, bears, raccoons) – at least four clawed toes on each foot,
incisors small, canines large
Elephants – long trunk (proboscis), ears very large, long incisors (tusks)
Perissodactyls (horses, zebras, rhinoceros) – foot ending on third digit (hooves), odd-toed
mammals, head elongate, ears moderate & tubular
Artiodacytls (cows, deer, goats, hippos) – hooves, even-toed mammals, upper incisors
reduced
Dolphins, porpoises & whales – aquatic with fins (hind appendages lacking), skin
essentially lacking hair, external ears lacking, blowhole