Module 16

Question 1

Synapomorphies in vertebrates

Answer 1

Endostyle - thyroid gland
Distinct head
Special cranial sense organs
Semicircular canals for balance and articulated vertebrate

Question 2

Endostyle

Answer 2

Develops in the thyroid gland
Produces hormones that regulate metabolism in all vertebrates

Question 3

Distinct head

Answer 3

Brain is housed within the cranium/skull
Cranium is made up of either cartilage or bone
- Primary function is to protect the brain

Brain: forebrain, midbrain, and hindbrain
- brain integrates signals from the sophisticated sensory organs
- gives vertebrates far greater situational awareness
- enables vertebrates to grow large

Question 4

Special cranial sense organs

Answer 4

Derived from ectodermal places

Question 5

Semicircular canals for balance and articulated vertebrae

Answer 5

Protects the dorsal hollow nerve cord
Vital in locomotion

Question 6

Movement of marine animals onto land

Answer 6

Some vertebrates began venturing into new niches on land
- Only those with key predisposing features could breathe air and move around
- Had to adapt to the full effects of gravity on their mass
- Terrestrial vertebrates must support the full weight of their bodies against gravity
- Has consequences for the development of skeleton and muscle

Low dentistry of air means that we only experience noticeable drag at high velocities
- Flight is possible if we can generate life
- This requires serious modifications to vertebrate bodies to reduce mass and thus weight

Question 7

Fishes

Answer 7

Describes the paraphyletic group of aquatic, scaly, finned creatures

Question 8

Class Petromyzontida

Answer 8

Lamprey
- eel-like bodies
- cartilaginous skeleton
- scaleless and lack paired appendages
- round mouths and horny teeth made of keratin

Suctorial round mouth with teeth allow them to attach to the outside of other fishes
- gouge a hole and drink their vital juices
- move rocks when building nests

Question 9

Class Myxini

Answer 9

Hagfishes
- Wholly marine organisms
- Lay large eggs that hatch directly into miniature adults that feed on detritus and carrion
- notable for producing copious amounts of slime/mucous that they use as a defence against predators

Question 10

Class Chondrichthyes

Answer 10

Cartilaginous fishes
- includes the elasmobranchs (strap gills) such as sharks and rays
- includes the holocephalans (chimeras)
- mostly marine

Question 11

Subphylum Elasmobranchii

Answer 11

Subphylum of Class Chondrichthyes
- teeth are derived from overlapping placid scales that clever the skin’s surface
- the fluting of the scales reduces drag when the animal is swimming

Batoids:
- skates, rays, and sawfishes
- majority are bottom dwellers - benthic
- torso-ventrally flattened and have large pectoral fins
- teeth are arranged in crushing plates for tackling hard prey

Question 13

Subclass Holoceephali

Answer 13

Subclass of Class Chondrichthyes
- wholly marine and mostly live in deep water
- have large pectoral fins that they use to fly through water
- have a strong spine on their dorsal fin
- whip-like tail
- upper jaw is fused to the cranium
- have plate-like crushing teeth

Question 14

Class Osteichthyes

Answer 14

Occur in two distinct subclasses:
- Actinopterygii
- Sarcopterygii

Question 15

Class Actinopterygii

Answer 15

Ray-finned fishes:
- Have paired pectoral and ventral fins – capable of complex movements
- Fins comprise fin membranes supported by bony rays
– Muscles that operate the fins sit within the body
- Mouth is terminal
– Upper jaw is framed by the premaxillary and maxillary bones
- Caudal fin is typically homocercal
- Many have a swim bladder
- Have four gill arches covered by bony operculum

Question 16

Sarcopterygii

Answer 16

Lobe-finned fishes
Relict group with few species

Sister group to the tetrapods
- Bone replaces cartilage during development – cartilage acts as the template
- Lung or swim bladder present – evolved as an extension of gut
- Several cranial and dental characters – teeth develop within the jaw bone

Question 17

Evolutionary trends of class Actinopterygii

Answer 17

Scale morphology from heavy dermal armour in primitive finned fishes
Light, thin, flexible cycloid and ctenoid scales in teleosts
→ This trend lowered mass and increased mobility to avoid predators and catch prey
- Scales of teleost overlap and lie within the epidermis rather than project from the skins
- Evolution of fin spines for protection – changes in the location of this fins allow either greater speed or greater maneuverability

Question 18

Class Sarcopterygii

Answer 18

Key derived characters:
The presence of muscular pectoral and pelvic fins – the muscles and bones of the appendicular skeleton protrude from the body
Fins are lobed

Question 19

Class Amphibia

Answer 19

Primarily made up of frogs
- First group of vertebrates to make extensive forays into terrestrial environments anc occur over an impressive range of habitats
- Rely on their thin, moist skin for their gas exchange needs
- Four libs derived from the pectoral and pelvic gills of fishes
- Thin skin
- Well developed paired lungs and a three chambered heart
- Ectotherms – body temperature matches their environment

Question 20

Class Reptilia

Answer 20

Includes lizards, snakes, crocodiles, non-avian dinosaurs, and turtles
Another paraphyletic grouping:
Lepidosauria – lizards and snakes
Testudines – turtles
Crocodilia
→ All three groupings broke the amphibians’ dependance on water for reproduction
Have a shelled egg which protects the developing embryo for desiccation
Horny, waterproof epidermis which protects them from desiccation and predators also assisted in their invasion of land
Most have scales in the epidermis – turtles and crocodilians have bony plates that lie in the dermis
Ectothermic – to gain metabolic advantages they will “sun” themselves
Most are carnivorous with few being herbivores

Question 21

Class Aves

Answer 21

Birds:
- Feathers derived from scales
- Lay hard-shelled eggs
- Have hollow bones
- Toothless beaked jaws
- Endothermic
- Have a four chambered heart

Question 22

Class Mammalia

Answer 22

Have mammary glands with which females produce milk for nursing their young
Have a neocortex in the brain
Hair for insulation
Three middle ear bones used in hearing
Homeotherms
High metabolic rate
→ Arose from a reptilian ancestor in the mid-Mesozoic
Evolved on land
Few are marine