Ectotherms lecture 2

Question 1

What are the craniates?

Answer 1

Chordates that have a cranium (skull), neural crest, pharyngeal gill clefts (gill slits or ears)
A higher metabolic rate, two chambered heart, hemaglobin and kidneys

Question 2

What phyla do we first see development of a head in?

Answer 2

The myxini

Question 3

What are the features of the agnathans?

Answer 3

Median fins, two chambered heart, simple digestive system, sens organs, external fertilization

Question 4

What are the features of the myxini?

Answer 4

The most basal craniate with a cartilaginous skull, retention of the notochord, a small brain, eyes, ears and nose opening
Fond only in marine environments

Question 5

What are the petromyzontida?

Answer 5

The lamprey, an example of an agnathan

Question 6

What are the features of the lamprey?

Answer 6

Cartilaginous skeleton, rudimentary vertebrae, sucker like oral disc, 7 pairs of gill apertures, moderately well developed eyes, dioecious (separate sexes)
A long marine larval stage followed by adult stage in freshwater

Question 7

What are the five classes in the gnathostomata?

Answer 7

Chondrichytes, osteichthyes, amphibian, reptilian, mammalia

Question 8

What are the critical innovations in the super class of the gnathostomata?

Answer 8

Jaws and a mineralized skeleton
Scales and teeth
Paired fins
Lateral line

Question 9

How is the mineralised skeleton believed to have developed?

Answer 9

It started as dental elements present within the head, these develop into teeth then denticles and then a skull and finally a skeleton

Question 10

What are the classes in the chondriocytes?

Answer 10

Selachiformes, Rajifromes and Chimaeriformes

Question 11

What are the features of selachiformes?

Answer 11

350 fusiform species
Low metabolic rate
Variable dentition
Lamnid sharks: no nictitating membrane
Carcharhind sharks: nictitating membrane

Question 12

What are the features of rajiformes?

Answer 12

Stingray, eagle ray, manta ray rhinobatoids

Electric rays-capacitor effect

Question 13

What are the features of chimaerifromes?

Answer 13

Operculum, upper jaw fused to skull

Question 14

What are the characteristics of chondrichthyes?

Answer 14

Heterocaudal fin
Ventral mouth
Skin with placoid scales
Cartilaginous endoskeleton
Two-chambered heart
5-7 pairs gills and exposed gill slits
No operculum
No swim bladder or lung
Internal fertilization and separate sexes

Question 15

What are the features of the shark skeleton?

Answer 15

It advances on the agnatha with the presence of jaws and teeth, paired fins (pectoral and pelvic) and an enlarged braincase

Question 16

What are the features of the osteichthyes?

Answer 16

Bony skeleton, numerous vertebrae, homocercal tail
Skin with embedded scales (though some are without scales)
Paired fins with rays of cartilage or bones
Terminal mouth, usually many teeth
Gills supported by bony arches and covered by operculum
Swim bladder often present
Two chambered heart
Separate sexes, usually external fertilization

Question 17

What are the bony fish groups?

Answer 17

The class osteichthyes which is split into the subclasses of actinopterygii ( chondrostei, holostei, teleostei), crossopterygii (actinistia) and dipnoi

Question 18

What are the features of the actinopterygii subclass?

Answer 18

Contains a bone skeleton rather than a cartel age one with many spines and ribs with a complex skull of several layers

Question 19

What is the lateral line system?

Answer 19

It is a canal along the side of a fish containing pores that open into tubes supplied with sense organs and are sensitive to low vibrations

Question 20

What animal is in the subclass crossopterygi?

Answer 20

The coelacanth

Question 21

What animal is in the subclass dipnoi?

Answer 21

The African lungfish