Osteichthyes

Question 1

Which group are Osteichthyes + Chondrichthyes in?

Answer 1

Gnathostomes

Question 2

What are actinopterygii?

What are sarcopterygia?

Answer 2

Ray-finned fish

Lobe-finned fish

Question 3

What are the features of osteichthyes?

Answer 3

> swim bladder/lung
mobile fins
reduced gill arches (3-4) + a gill cover (operculum)
bony skeleton

Question 4

What is the lung used for in ray-finned fish?

Answer 4

Buoyancy

- can move at low speeds + stay afloat

Question 5

What is Polypterus?

Answer 5

The most primitive living member of the ray-finned fish

Question 6

What does the presence of lungs in Polypterus suggest about the evolution of lungs?

Answer 6

Can breathe air
(warm, stagnant water has little O2)

Lungs originally evolved to help aquatic fish cope w/ low O2 water
- NOT for life on land

Lung later modified into swim bladder (buoyancy device)

Question 7

What are the fins like in Sarcopterygian fish?

Answer 7

Mobile fin base

- allows them to move the pectoral + pelvic fins

Question 8

What is a mobile fin made of?

Answer 8

A series of bony structs sporting a flexible membrane

Question 9

How can bony fish use their fins for propulsion?

Answer 9

Fold + unfold their fins

= changes their shape

Question 10

What is special about the fins in Polypterus?

Answer 10

Mobile fin bases (+ lungs) allow them to crawl up onto land

Question 11

Describe the respiratory system in bony fish

Answer 11

3 pairs of gills covered by a movable operculum
(lost in amniotes but retained in amphibians)

Advanced pumping mechanism - can effectively oxygenate blood while still

Question 12

What is bone made of in bony fish?

Answer 12

Mixture of collagen (protein) + calcium phosphate (mineral)

Question 13

Describe the mineralisation process

Answer 13

1st mineralised = external head plates + scales

Then deeper tissues are mineralised e.g. vertebrae, cartridges of fin skeleton + fin rays
Outside in

Question 14

What enables bony fish to perform complex movements?

Answer 14

Complex joints + rigid support structures

Question 15

What are the features of ray-finned fish/teleosts?

Answer 15

> swim bladder
loss of electroreception
reduced armour
mobile snouts

Question 16

Why are the Coelacanths special?

Answer 16

> Retain electroreceptors
Have internal fertilisation & give birth to live young
Muscular, limb-like fin base that’s v mobile - has a shoulder joint
Living fossils

Question 17

What is special about lungfish?

Answer 17

Obligate air breathers

Question 18

What does ‘amphibian’ mean?

Answer 18

‘dual-life’

Question 19

What is special about amphibians?

Answer 19

Bridge gap between aquatic + terrestrial

• water needed for reproductive cycle
• hunt for prey on land

Question 20

What features do Panederichthyes have?

Answer 20

Loss of midline fins
Eyes on top of head
Flattened head

Question 21

What does the flattened head & eyes on top of head of Panderichthyes imply?

Answer 21

Typical of bottom dwelling fish

- implies our ancestors were bottom-feeders

Question 22

What features do Tiktaalik have?

Answer 22

Well developed limb bones
Reduced fin rays

= functionally between a limb + a fin

Question 23

What features do Acanthastega have?

Answer 23

8 fingers + toes
Elongated limbs (weak wrist so can’t support weight on land)
Retains tail
Retains gill arches

Question 24

What were limbs + digits originally evolved for?

Answer 24

Walking underwater

• reduces chance of disturbing + altering prey
• easier than swimming against strong currents

Question 25

When did tetrapods move onto land?

Answer 25

After the end-Devonian mass extinction

Question 26

What features did terrestrial tetrapods have?

Answer 26

Eyes on side
Powerful legs
5 strong toes