Fish

Question 1

What were the first vertebrates?

Answer 1

Fish

Question 2

What two groups can fish be categorised into?

Answer 2

Agnatha - jawless

Gnathostomes = jaws

Question 3

What are some features of ancient jawless fish (Ostracoderms)

Answer 3

Heavily armoured

Covered with bony plates

Plates around mouth probably acted as scoop for food

Lacked pectoral fins - probably bad swimmers

Went extinct when jawed fish arose

Question 4

What are the main features of modern jawless fish? What animals come under these?

Answer 4

Eel-like

Lack paired fins and jaws

No armour

Cartilaginous skeleton

Hagfish and lampreys

Question 5

What were some ancient jawed fishes?

Answer 5

Placoderms

Question 6

What animals come under cartilaginous fish?

Answer 6

Sharks

Rays

Ratfish

Chimaeras

Question 7

What are the main features of cartilaginous fish?

Answer 7

Flexible endoskeleton of cartilage

Many covered in small tooth-like placoid scales

Cartilaginous skeleton is a derived trait - not present in the ancestor

Acute senses e.g. lateral line for detecting pressure changes

Heterocercal tail (top fin bigger than the other) and wing-like pectoral fins

Have more rods than cones

Question 8

What are the main features of bony fish?

Answer 8

Endoskeleton made of calcium phosphate

Skin has flattened bony scales

Lateral line system

Have a gas-sac organ e.g. a swim bladder or lung (for buoyancy and may act as a oxygen reservoir)

Question 9

What are the three classes of bony fish?

Answer 9

Lobe-finned fish

Lungfish

Ray-finned fish

Question 10

What are the main features of lobe-finned fish?

Answer 10

Muscular pectoral and pelvic fins that are supported by extensions of the skeleton

Large bottom dwellers that may have walked on the sea bed

Coelacanth is the only living species

Question 11

What are the main features of lungfish?

Answer 11

Have lungs and nostrils

Breathe air

Live in stagnant ponds and and swamps