BIOL 204L Practical 6

5 chordate synapomorphies

• Notochord

• Dorsal hollow nerve cord

• Pharyngeal slits

• Post-anal tail

• Endostyle (or thyroid)

Know several vertebrate synapomorphies and their functions

• Cranium- houses brain and sensory organs

• Tripartite brain- help deal with information from new sensory organs

• Lateral line system- for sensing vibration and water movement

• 2 chambered heart- accommodate increased blood flow

• Hemoglobin- carries oxygen in blood

• Liver- produces digestive juices, stores energy, filters out waste

• Kidney- maintains blood solute concentration, removes waste

• Vertebrae- protects spinal cord and supports body

Know what the purpose of the lateral line is

The lateral line detects vibrations and movement in the water 

Know what is different between shark scales and bony fish scales

Sharks have placoid scales (denticules) and bony fish have adenticulate scales

How do sharks and rays find their food

Sharks find their food by using the “ampullae of lorenzini” to detect changes in electrical field

Know how to tell apart hagfish and lampreys – life stages, parasitism, habitat, features

• Hagfish: mostly scavengers, direct development (no larval stage)

• Lampreys: mostly anadromous (migrate from sea to freshwater), have larval stage (ammocoete), undergo metamorphosis 

Know how to tell apart male and female sharks

Males have pelvic claspers, females do not

Why is it advantageous for a shark to have a heterocercal tail? 

The heterocercal tail is an uneven tail that is good for burst swimming

How do ray finned fishes regulate buoyancy?

They use a swim bladder or long for buoyancy

What is a key difference between your nose and a salmon’s nose?

Their nostril is only for smell but ours is connected to the mouth and used for breathing

What sort of skin do amphibians have? What are advantages? Disadvantages?

Amphibians have thin, moist skin with mucus and poison glands that allows gas exchange. The advantages are that it allows gas exchange, mucus helps prevent drying out, and the poison glands are defense. The disadvantage is that the skin can easily dry out so they must stay in moist environments.

What’s a unique trait about caecilians? How could you tell apart a caecilian and a worm?

Caecilians are legless amphibians with teeth and a tentacle sensory organ. You can tell them apart from a worm because worms don’t have teeth, a skull, or sense organs.

How many toes (front limbs) do frogs and salamanders have

Frogs and salamanders both have 4 front toes

What is an axolotl? 

A type of salamander that keeps its gills as an adult

Be able to identify what environment a frog is best adapted for

• Pond dweller → streamlined, long legs, webbed feet

• Burrower → short and stubby body, short hindlimbs, digging structures

• Climber/arboreal (tree) → small body, long legs, toe pads for adhesion

What does the amniote egg allow for with reproduction

The amniote leg allows reproduction on land. The key features are an amnion (fluid protection), chorion (gas exchange), and yolk (nutrition)

What trait unites all reptiles (turtles, birds, lizards, snakes, crocodiles)?

 Can reproduce outside of water, have internal fertilization, and a hard keratin covering. 

What is a turtle shell derived from? Can a turtle “take off” its shell?

The turtle shell is derived from its rib and vertebrae, so it cannot be taken off. 

Is a tuatara a lizard?

No, it is a separate lineage called a Sphenodon.

What is the name for a lizard being able to “drop” its tail? Why would it be able to do this

This is called tail autonomy and it is beneficial to escape predators.

Why do snakes flick out their forked tongues so much?

This allows them to detect smells and “taste” the environment. 

How could you tell apart a snake and a legless lizard?

• Snakes: Limbless, no external ear openings, no moveable eyelids, fusion of scale over eye 

• Legless lizard: external ear openings, moveable eyelids 

Be able to identify what environment a lizard is best suited for

• Sand runner- fringes on toes, flattened body, head wedged shaped

• Burrower- lack limbs, elongated

• Semi-aquatic- enlarged tail for swimming

• In trees- geckos have toe pads and chameleons have fused toes

Where are birds on the phylogenetic tree? How are they related to lizards, crocodiles, mammals?

Birds are dinosaurs. Their closest relatives are crocodiles. They are also closely related to lizards (both reptiles) but mammals are a different group.

What behavioral traits are shared between crocodilians and birds?

Four chambered heart, parental care, facultative bipedalism, nest building

What are some skeletal modifications that facilitate bird flight?

Hollow bones, fused bones, and keeled sternum.

What are feathers modified from? What is the rachis?

Feathers are modified from scales with beta-keratin. The rachis is the central axis of the feather.

Know at least TWO of the bird beak morphologies and what they would eat

The insect eater has a long and pointed beak. The seed cracker has a short and stubby beak with sharp edges.