USC BISC 120 Final Exam Trond Sigurdsen What is the largest group of deuterostomes? - Answer- chordates Chordates are mostly vertebraes or invertebrates? Primitive chordates have this structure - Answer- They are mostly vertebrates but there are some primitive forms with a notochord What are the three types of chordates? - Answer- vertebrates, lancelets, tunicates What is the amphioxus? - Answer- a lancelet These two are the simplest chordates - Answer- lancelets and tunicates What do lancelets and tunicates lack? What do they have instead? - Answer- They lack a vertebral column but have a notochord as juveniles. Adult lancelets also have a notochord What are the five notable features of chordates? - Answer- dorsal hollow nerve cord, dorsal supportive notochord, pharyangeal slits/pouches, post-anal tail, myotomes Where is the nerve cord located in comparison to the notochord? - Answer- The nerve cord is dorsal to the notochord What are the pharyngeal slits in lancelets and fish? - Answer- Gill slits Are adult tunicates motile or sessile? - Answer- sessile What two openings do tunicates have? - Answer- incurrent and excurrent siphone What do large apparatus do tunicates use to filter water? - Answer- the pharynx Describe the larva of tunicates - Answer- free-swimming with typical chordate characteristics What does the dorsal hollow nerve cord develop into? - Answer- It develops into the
central nervous system,: spinal cord and brain
How does the dorsal hollow nerve cord originate? What is a byproduct of this process? - Answer- Originates embryonically as a folding of ectoderm dorsal to the notochord. Also, neural crest cells are "pinched off" in this process.What three tissues do neural crest cells give rise to? - Answer- Many bones in the skull, sensory neurons, and pigment cells in skin (melanocytes) 1 / 3
In vertebrates, the vertebrae form around these two structures - Answer- the notochord and spinal cord Vertebrae start as this material and then form this material - Answer- cartilage turns to bone In many species of vertebrates, the notochord persists through this structure - Answer- the vertebral column In humans, a small piece of notochord called the nucleus pulposus is found in this structure? - Answer- intervertebral disk This bone protects the brain and sensory system in the head - Answer- the cranium What are the most primitive/basal vertebrates? What are they considered to be?Why? - Answer- the hagfish and lamprey. they are cyclostomes because they have no jaw This is another term for fish - Answer- pisces What is the term "fish" traditionally defined as? - Answer- Traditionally very vague; meaning almost any animal in the seas/fresh water The term "fish" is now thought of as - Answer- Vertebrata minus Tetrapoda In cyclostomes, what supports the mouth? What are the teeth made of? - Answer- Mouth supported by musculature (not skeleton) and teeth made of horny material Describe the location of fins on cyclostomes - Answer- Fins along the body, but not paired Describe the skeleton of cyclostomes? What is the important part? What is the rest
made of? - Answer- Skeleton: notochord is an important part, rest is made from
cartilage (and relatively simple), This group of cyclostomes are considered to be the most primitive surviving vertebrates - Answer- hagfish (rudimentary vertebrate) The term for a jawless fish that also includes extinct species like connodonts is - Answer- agnathan What do hagfish eat? - Answer- They are scavengers who eat rotting fish, dead whales etc., sometimes carnivorous What is a defense mechanism of hagfish? - Answer- Glands along body produce copious amounts of slime to deter potential predators Unlike hagfish, lampreys have this structure - Answer- a true vertebral column composed of cartilaginous vertebrae 2 / 3
Despite having a true vertebral column made of cartilage, the main skeletal support structure of lampreys is still this - Answer- notochord Lampreys are this type of parasite, what do they eat? - Answer- ectoparasites who eat tissue and drink blood What are jawed vertebrates called - Answer- gnathostomes What are the three common components of a gnathostome? - Answer- jaws (skeletal support of mouth), paired fins (pectoral and pelvic fins), lateral line system (sensory system along the body) How are jaws believed to have evolved? - Answer- Jaws may have evolved by modifications of skeletal support (gill arches) of the anterior pharyngeal slits (gill slits). They might have originally been part of a system for filter feeding and respiration The development of these two structures allowed for fish to become more active and to bite off chunks of food. - Answer- jaw and paired fins What structures compose the lateral line system? What does this system do? - Answer- Fish have canals in the skin with pores. They also have cupula with sensory hairs (neuromast sensory organs) that can sense water displacement What are the four lineages of gnathostomes? - Answer- chondrichthyans, ray-finned fish, lobe-finned fish, tetrapods These two gnathostome lineages are considered to be "bony fish" (osteichthyans) - Answer- ray-finned and lobe-finned fish Chondrichthyans include - Answer- Sharks, rays, ratfish (chimaera) What are chondrichthyan skeletons made of? - Answer- cartilage Describe the gill slits of chondrichthyans - Answer- Most have separate gill slits (except chimaera, with operculum) Are sharks predators? - Answer- yes Which species of shark has the best electroreceptors? - Answer- hammerhead shark Why do sharks not sink? - Answer- They are heavier than water but their oily liver keeps them buoyant In addition to sight, hearing, smell, and sensitive lateral lines, sharks also have this sensing structure - Answer- electroreceptors on the head What is another name for bony fish (ray/lobe fins) - Answer- osteichthyans
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