SI worksheet 13 Answers
Which of the following groups represents the most basal lineage of vertebrates?
a. Hagfish
 What is the hagfishes claim to fame? FIRST CRANIATES but not verts!
b. Conodonts
c. Lampreys
d. Sharks
 Vertebrate but not basal.
 Whats their Subphyla? Chondricthyes - Cartilagenous
e. None of the above
The first vertebrates to live on land were _____.
a. Mammals
b. Conodonts
c. Reptiles
d. Chondrichthyans
e. Amphibians
Which of the following sets of animals contains only gnathostomes? (Jaws)
a. Lampreys, Conodonts, and hagfish
b. Conodonts, placoderms, and acanthodians
c. Sharks, hagfish, and whales
d. Rays, turtles, pigeons, and tuna
e. Hagfish, bass, sharks and frogs
The gill flap, or operculum, was an important adaptation for fish because it helps
with _____.
a. Sensing vibrations in the water - Lateral Line System
b. Sensing chemicals in the water
c. Maintaining a supply of oxygen
 What subphylum did this appear/ or was it talked about –
Actinotperygii (Ray-Finned)
d. Adjusting buoyancy - Swim Bladder
e. Underwater reproduction
According to one hypothesis how did jaws evolve in Gnathostomes?
 Hypothesis states that jaws evolved by modification of skeletal rods
that had previously supported the gill slits. The remaining gill slits are
used for respiration
What is the “lateral line system?”
 organs that form a row along each side of the body and are
sensitive to vibrations in the surrounding water.
 When did this appear: In Gnathostomes!
What is missing in a lamprey’s cartilaginous skeleton that is present in most other
cartilage seen in nature?
 collagen
What is the function of the “spiral valve?”
 Within the digestive tract of Chondrichthyans there is a SPIRAL VALVE
that increases surface area and increases the time that the food is in the
digestive system.
 Do they have a long or short Digestive Tract? SHORT
Define the following terms and give an example of an animal for each type:
 Oviparous - – the eggs hatch outside the mother’s body

Ovoviviparous – fertilized eggs retained. Nourished by the egg yolk they
grow and hatch inside, then are born

Viviparous – Embryo develops within the uterus and is nourished through a yolk sac
placenta from the mother’s blood. Live birth.
In sharks the excratory system, digestive tract, and reproductive tract empty into a
common opening called the…
 cloaca
How are ray-finned fishes able to maintain buoyancy underwater?
 Fishes control their buoyancy through the use of a SWIM BLADDER.
Movement of gasses from the blood to the bladder control how buoyant the
fish is.
Based on the length of the intestine how can you tell if a fish is an herbivore or a
carnivore?


Short intestine carnivore. Long intestine herbivore.
Why do Herbivores need a longer intestine? Need more time to break
down cellulose and tough plant matter.