Lectures 14/15: Vertebrates Flashcards
what do tunicates most resemble?
chordates during their larval stage, which is short
why do tunicate larva use their tail muscle and notochord?
to swim through the water and find a suitable spot to settle.
how does the tunicate larva find a suitable spot to settle?
it is guided by cues from light and gravity sensitive cells
what happens after the tunicate settles?
goes through metamorphosis, becomes sessile and lose most chordate traits.
- loses tail and notochord
- nervous system breaks down
- organs shift 90°
what are tunicates?
they are the earliest branch of chordates
what do lancelets look like?
blade-like
how do lancelets live?
with their posterior end buried in the sand and the anterior end exposed for feeding
how do tunicates and lancelets provide clues in vertebrate evolution?
tunicates show chordate characteristics as larvae while lancelets show characteristics as adults
what was the next major transition after the evolution of the basic chordate body plan?
the appearance of a head
what are craniates?
chordates with head-like structure
what did the origin of a head open up for chordates?
opened up a new way of feeding for chordates: active predation
what differentiates craniates from other chordates?
- on the genetic level: craniates possess 2 clusters of Hox genes, compared to lancelets and chordates only having one cluster
what are the group of embryonic cells in craniates called?
neural crest
where does the neural crest form?
near the dorsal margins
what do hagfish lack?
jaws and vertebrae (BONE)
what is the skull of a hagfish made of?
cartilage
what are some hagfish characteristics?
- swim in snake-like fashion
- small brain, eyes, ears, and nasal opening
- toothlike formations made of keratin
- marine scavengers
how do hagfish move?
use their segmental muscles to exert force against their notochord
are hagfish considered a fish?
no. vertebrate systematists do not consider hagfishes to be fish
what do hagfish feed onto?
worms and sick/dead fish
what is a notochord?
a flexible, rod-like structure made of cells that forms the primary skeletal support in all chordates.
- runs along the the dorsal side of the organism, between the nerve cord and gut
what is the oldest living lineage of vertebrates?
lampreys
most lampreys are ____ that feed by clamping a round, ____ mouth onto a fish
parasites; jawless
how do lampreys kill/eat their prey?
they use their rasping tongues to penetrate the skin of their fish prey and to ingest the preys blood
what are conodonts?
soft-bodied vertebrates. kinda look like long ass worms in water
whats the difference between anterior vs posterior?
(top vs bottom)
- anterior: refers to the front or forward part of the body. ex: chest is anterior to the spine
- posterior: refers to the back or rear part of the body.
ex: spine is posterior to the chest
what is the “back” referred to as technically?
dorsal
what is the “belly” referred to as technically?
the ventral
what type of vertebrates has a true jaw?
Gnathostomes
how did the jaws of Gnathostomes evolve?
by modification of the skeletal rod.
- rod had previously supported the anterior pharyngeal gill slits
- but gill slits not needed for feeding anymore and only respiratory gas exchange
what is the earliest fossil record of gnathostomes called?
placoderms
why are the forebrain enlarged for gnathostome?
enhanced senses of vision and smell
how did the lateral line system evolve?
evolved as a row of microscopic organs sensitive to vibrations in the surrounding water
what were the characteristics of the gnathostomes common ancestor?
- mineralized axial skeleton
- shoulder girdle
- two sets of paired appendages
what were the major evolutionary breakthroughs for gnathostomes?
- jaws (with the help of teeth)
- paired fins
where does the name chondrichthyes come from?
chondric = cartillage
chrondocites = cells that produce cartillage
what is the biggest and most successful vertebrate predators in the oceans
chrondrichthyes and sharks
chrondrichthyes have relatively _____ endoskeletons of ______ rather than _____.
flexible; cartilage; bone
all chondrichthyes have well-developed ____ and ___ _____
jaws; paired fins
the teeth of sharks are…
mineralized
what are vertebrates?
animals with a backbone/spine
where does the name vertebrate come from?
named for vertebrae, which is the series of bones that make up the vertebral column (backbone)
what are the 4 chordate characteristics?
- notochord
- dorsal (hollow nerve cord)
- pharyngeal slits
- muscular, post-anal tail
what is a notochord?
a flexible rod-like structure. provides support and shapes the body
what is found along the pharynx? what are they called?
a series of pouches separated by grooves, called pharyngeal clefts
in most chordates, the grooves along the pharynx (pharyngeal clefts) develop into…
pharyngeal slits
what are pharyngeal slits used for?
- in some invertebrate chordates, these gill slits are used to filter food from water
- in vertebrates, the gill slits are used for gas exchange, supporting jaws, hearing and other functions
what is a dorsal nerve cord?
a tube of nerve tissue running along the back. develops from a plate of ectoderm that rolls into a tube dorsal to the notochord. turns into the brain and spinal cord
what is a post-anal tail? what does it contain/provide?
- a tail extending beyond the anus
- contains skeletal elements and muscles
- provides much of the power to swim in aquatic animals
what is the notochord composed of?
large, fluid-filled cells encased in fairly stiff/fibrous tissue.
what is the notochord in humans?
the gelatinous material of the disks between vertebrae
what is the region posterior (behind) to the mouth called?
pharynx
what does “Osteichthyes” mean?
bony fish
what is the exoskeleton of all bony fish made of?
calcium phosphate
how do bony fish breathe?
by drawing water over 4-5 pairs of gills located in chambers
what are the chambers in bony fish covered by?
a protective flap = operculum
most bony fish have an air-filled sac called a….
swim bladder
how does the air sac in bony fish help them?
helps them float by balancing their body weight, allowing them to stay suspended in water without sinking
what was one of the most significant events in vertebrate history?
when the fins evolved intro tetrapod limbs and feet
what is the most significant character of tetrapods?
their 4 limbs (allows them to support their weight on land)
what do the digits on the feet of tetrapods help with?
they help the animal push against the ground when they walk by using their muscles
what are tetrapods?
animals with four limbs
what happened to the pelvic girdle after the move to land? what did this allow?
the pelvic girdle became fused to the backbone.
- this connection helps their hind legs push against the ground more effectively, and allowed the body to move better when walking/running
the amniote clade consists of…
the mammals and reptiles including birds
what is the major derived character of amniotes?
the amniotic egg
what is inside the shell of the amniotic egg and how does it function?
- several extraembryonic membranes
- functions in gas exchange, waste store, and transfer stored nutrients to the embryo
what is the amniotic egg named after?
it is named after the amnion, a membrane that surrounds the embryo. “private pond” that bathes the embryo and acts as a hydraulic shock absorber
what makes certain scale waterproof and prevent dehydration in dry air?
protein keratin
how do reptiles obtain all their oxygen?
through lungs
many turtles use the moist surfaces of their ______ for gas exchange
cloaca
why are all modern birds considered reptiles?
because they evolved from the dinos
what are mammals?
amniotes (animals) that have hair and produce milk
what is the hair of mammals made of?
keratin
what contributes to endothermy in mammals?
hair and a layer of fat under the skin retain metabolic heat
what are the only living mammals that lay eggs?
platypuses and the echidnas
how do the babies of platypi and echidnas suck on the mothers milk?
suck the mothers fur since they lack nipples
whats the difference between marsupials and montremes?
marsupials have a higher metabolic rate, have nipples, and give birth to live young
what were the earliest primates?
tree dwellers
the grasping hands and feet of primates are adaptations for…
hanging onto tree branches
humans are _____ _____
bipedal hominoids
what does bipedal mean
walk on two legs
what is paleonanthropology?
the study of human origins and evolution
