Unit 7: Chordates Flashcards
5 Characteristics of Chordates: Notochord
Between the digestive tube and nerve cord
* Replaced by vertebral column in craniates
5 Characteristics of Chordates: Dorsal hallow nerve cord
Derived from endoderm
5 Characteristics of Chordates: pharyngeal slits
openings in pharynx
– allow H2O out of mouth after feeding
5 Characteristics of Chordates: Endostyle/thyroid gland
ciliated mucous producing tissue on
floor of the pharynx – produces similar substance to thyroid hormone
5 Characteristics of Chordates: Post-anal tail
locomotion for fish, balance in some terrestrial species
* Vestigial coccyx aids in balance while sitting in humans
Non-vertebrate Chordate Groups: Invert Clade #1: Cephalochordata
– Lancets – retain 5 characteristics into adulthood
* Fossil representatives from Cambrian (500 MYA)
* Few cm blade-like shaped body, live in sand of warm/tropical seas
*H2O in mouth, exits pharyngeal slits that filter food particles, trapped food particles
caught by endostyle, carried to the gut.
* Dioecious
Non-vertebrate Chordate Groups: Invert Clade #2: Urochordata
– Tunicates – 1,600 sp. –
* only Pharyngeal slits and endostyle as adults
* Hermaphrodites (serial in some cases)
* Single or colonial filter feeders
Cranium
Bony, cartilaginous, or fibrous structure surrounding brain, jaw and facial bones
Craniata
includes all vertebrates, presence of cranium
Craniata: Contain a vertebrae
series of separate, irregularly shaped bones joined to form a backbone
* Initially form in segments around notochord – but replace it in adults
* Notochord becomes nucleus pulposus – discs between vertebrae
how many craniata
62,000 species described
Craniata: Agnatha vs Gnathostomes
jawless vertebrates vs jawed vertebrates
Superclass Agnatha
Monophyletic group
- Myxini and Petromyzontidae
- Once thought to be individual lineages
Myxini
- 70 sp. – Hagfishes – all marine
- Almost blind, sensory barbules near mouth locate prey
- Unique slime glands on the skin
- Cartilaginous skull, fibrous & cartilaginous skeleton
- Notochord length of body – major structural support
- Not replaced by spinal column = sister clade to vertebrates
Petromyzontidae
- 40 sp – Lamprey – Marine and Freshwater
- All spawn in freshwater
- Eye muscles, true cerebellum, vertebral elements
- One of earliest divergences from vertebrate*
- Suspension-feeding juveniles
- Adults may be parasitic - Rasping tongue
Gnathostomes
- True jaws & paired fins
- From 1st set of gill arches ** ON TEST
- Chondrichthyes – cartilaginous skeletons
- Osteichthyes – Bony skeleton
Actinopterygii – ray-finned fishes
Sarcopterygii – Lobe-finned fishes
Chondrichthyes
- 370 MYA – today 1,000 sp – sharks, skates, rays, sawfishes
- Paired fins, cartilage skeleton
- Sensitive to vibrations and electrical currents:
Ampullae of Lorenzini – Sharks – electromagnetic fields produced by all living things
Lateral line – detect movement and vibration analogous to hearing in terrestrial vertebrates
Chondrichthyes - Sexual reproduction – sharks
- internal fertilization (sharks – can be oviviviparous (hatch from egg while in uterus))
- Mermaid’s purse – oviparous (egg-laying)
- Hammerheads & Tiger sharks - viviparous (live-bearing)
Rays and Skates
- 500 sp
- Flattened bodies, pectoral fins fused to the head
- Gill slits on the ventral surface
Amphibian Characteristics
- 4 limbs (Caecilians – evolutionary reversal)
- Moist, permeable skin
- Respiration through the skin, buccal cavity, lungs
- All carnivores and have teeth
- Vomerine teeth in roof of mouth
- Image-forming eyes and colour vision
- Ears with extra bone (operculum) in the ear
Osteichthyes
- 30,000 sp. Most numerous vertebrates
- Ossified skeleton
- Gills, swim bladder, lateral line
- Actinopterygii (Ray-finned fishes) – the most numerous group of fish
- Tuna, Bass, Trout…slender bones that support fins
- Sarcopterygii (lobe-finned fishes)
- Precursor to tetrapod limbs
-Coelacanths alive today
Amphibian Evolution: First tetrapods
– 400 MYA
* Evolved from lobe-finned fishes
* Transition to breathing air and moving on land = 50 MY
Amphibian Evolution: Devonian
Early aquatic tetrapods in Devonian
* Aquatic – body not supported out of water
Amphibian Evolution: Carboniferous
moved to land with few predators/competitors
Modern Amphibians
6,770 sp in three clades of subclass Lissamphibia
* Urodela, Anura, Apoda
Urodela
– Salamanders (620 sp)
* Movement through lateral undulation
* No lungs or primitive lungs, some gills and lungs
* Reproduction - courtship, spermatophore, oviparous, eggs in water (sperm packets)
* Metamorphosis before hatching
Anura
Frogs & Toads – 5,965 sp. “no tail”
* Limbs adapted for jumping
* Some skin glands modified for toxin release
* Reproduction – external fertilization (female egg, male fertilizes)
* Parental care varied – none to carrying tadpoles/eggs on back
* Metamorphosis after hatching
Apoda
Caecilians – 185 sp.
No limbs, evolved from limbed ancestor
* Resemble earthworm – with teeth and jaws
* Internal fertilization, oviparous or viviparous
Reptiles: Characteristics of Amniotes
- Terrestrially adapted egg – Amniotic Egg *breathes!!
AMNIOTIC EGG: Blood vessels in the yolk sac – transport nutrients to the embryo - Chorion – O2 & CO2 exchange – embryo and eggs external environment
- Allantois – Stores N – wastes, also facilitates respiration
- Amnion – protects the embryo from mechanical shock – supports hydration
The extra-embryonic membranes have various functions
Evolution of Amniotes
- Early tetrapod ancestor 340 MYA – 2 main lineages
Synapsids: - Therapsids (mammals evolved from)
Sauropsids: - Anapsids. -Diapsids (gave rise to reptiles) - Temporal fenestrae – post-orbital openings in the skull:
Anapsids – no fenestrae
Synapsids – 1 fenestrae
Diapsids – 2 fenestrae
Diapsids
Diverged into Archosauromorpha & Lepidosauromorpha
- Archosaurs (ancient lizard form) – crocodilians, ichthyosaurs, pterosaurs, dinosaurs, birds “WHICH GROUP DOES BIRD/CROC BELONG TO”**
- Lepidosaurs (scaly lizard form) – lizards, snakes, tuataras
Characteristics of Reptiles
- Tetrapods, amniotic eggs (some oviviviparous, some viviparous)
- Scaly skin – rich in Keratin & Waxy lipids
- Ventilation of lungs with muscles
- Ectothermic:
Crocodilians – regional endotherms (thoracic temps, pretty constant)
Can survive on about 10% energy of comparable endotherm** - Burmation – metabolism slowed in cold temps
Evolution of Reptiles
- Archosaurs give rise to Dinosaurs:
Saurischia (lizard-hipped)
Ornithischia (bird-hipped) - Archosaurs give rise to Pterosaurs:
More than 200 sp described – aerial
100 sp terrestrial - Age of dinosaurs ended 65 MYA
Modern Reptiles: Crocodilia
Middle Triassic – alligators, crocodiles, gharials, caimans
*Fresh and saltwater of Africa, Australia, Asia, South America, southern North America
Modern Reptiles: Sphenodontia
Early mesozoic - Two species today – tautara
Modern Reptiles: Squamata
Late Permian – Lizards (6,000 sp) and Snakes (3,600 sp)
* Snakes– specialized jaw in snakes– 8 rotational joints
* Snakes–single lung (long slender body)
* Venom glands
* No eyelids–but transparent scale
Modern Reptiles: Testudines
– 200mya
* Carapace (dorsal shell) includes backbone & ribs
* Plastron (ventral shell)
* Scutes – scales covering both shells
Characteristics of Birds
- 10,000 described species – most of any land animal group
- Homeotherms – maintain elevated and constant body temp
- Produce feathers – modified scales
–> Contour feathers – barbs maintain tight configuration - interlock
–> Down feathers – barbs do not interlock
–>Flight feathers:
- Primary feathers: at wing tips–provide thrust
- Closer to body– provide lift
- Contour feathers– reduce drag– shingle like action
birds: bones
- Hallow bones = pneumatic bones
- Specialized furcula (fused clavicles) = wishbone
- Fused T – vertebrae
- Keel
birds: cloaca
– common opening
- concentrates urine to urate salts
birds respiration
- Non-inflatable lungs
- Air sacs
- Unidirectional flow TEST!!!
Evolution of Birds
Diapsid: Archosaurs (Crocodilians, Pterosaurs, Dinosaurs)
* Birds from Saurischians (theropods)
- Clade Neornithes
- Neornithes gave rise to Archeopteryx
Evolution of Flight
- Arboreal hypothesis – gliding from branch to branch
- Terrestrial hypothesis- pursuit of prey with wings out
Characteristics of Mammals
Hair: composed of keratin
- Functions – maintaining heat, sensory, communication
Skin glands:
- Sebaceous glands – lipids for hair and skin
- Eccrine – Sweat (perspiration) – mostly water and metabolic wastes
- Apocrine glands – scent glands
- Mammary glands – produce milk
- Single lower jaw
- Inner ear bones – modified jaw bones
Evolution of Mammals
Synapsids: single, ancestrally fused, postorbital opening in the skull
- Evolved from therapsids in late Triassic
- Earliest mammal fossils from the early Jurassic
- Morganucodonts: both mammalian and reptilian jaws – nocturnal insectivores
Living Mammals
- Monotremes (egg-laying mammals):
Ornithorhynchidae (Bird beak), Tachyglossidae (sticky tongue) - Marsupials: 2/3 in Australia, Incomplete fetal development (in many)
- Eutherians (Placentals) : Chorioallantoic placenta
Eutherians (Placentals)
Atlantogeneta:
* Afrotheria (Elephants, hyraxes, manatees)
* Xenarthra (anteaters, armadillos, and sloths)
Boreoeutheria:
* Euarchontoglires (tree shrews, rodents, lagomorphs, primates)
* Laurasiatherian:
- Perissodactyla– rhinos and horses
- Cetartiodactyla– cows, giraffes, pigs, hippos, whales
- Carnivora– dogs, cats, bears
- Chiroptera– bats and flying foxes
Characteristics of Primates
Hands and feet adapted for brachiation (swinging through trees):
* Rotating shoulder joint
* Big toe separated from others, opposable thumbs
* Stereoscopic vision
* Larger brains
* Claws flattened into nails
* Typically 1 offspring per pregnancy
* Trend toward upright body position
Primate Orders
Strepsirrhini: turned nosed
–> Prosimians – bush babies and lemurs
Haplorhini: simple nosed
–> Tarsiers
–> Simians – New world moneys, old world monkeys, new world monkeys, apes, humans
Primate Evolution
1) Proto-primates – North Africa – squirrel sized – 65-85MYA
2) True primates – 55 MYA – N.A., Europe, Asia, Africa - Resembled present-day prosimians such as lemurs
3) Anthropoid – 40 MYA
* S.A. (New World) – all arboreal
* Africa & Asia (Old World) – arboreal and ground-dwelling
4) Apes – 25MYA Africa
* Lesser apes – Halobatidae – gibbons, siamangs
* Great Apes - Pan (chimps), Gorilla (gorillas), Pongo (orangutans), Homo (humans)
Great Apes
Gorillas: strong sexual dimorphism
Chimps/Humans: Lineages Separated 6MYA
–> Chimps / bonobo – 2 MYA – Congo River
Humans: our species only surviving member from original split
–> Non-linear related species – H. neanderthalensis, H. rhodesienses, H.
heidelbergensis
–> Paranthropus
–> Australopithecus
