Fishes: Evolution and Systematics

Question 1

What is evolution?

Answer 1

Genetic change through time

Question 2

Define systematics.

Answer 2

Study of the relationships between extant/extinct organisms over time

Question 3

What is phylogeny?

Answer 3

A visual representation of the evolutionary history and relationships between organisms

Question 4

What does cladistics involve?

Answer 4

Constructing a phylogeny using traits of an organism

Question 5

What is phylogenetics?

Answer 5

Constructing a phylogeny using molecular data

Question 6

List the characteristics of infraclass Agnatha.

Answer 6

• Without jaws
• Notochord in larvae and adults
• Cartilaginous skeleton
• Absence of paired fins
• Seven or more paired gill pouches
• External fertilization and development
• Covered by skin, no scales

Question 7

What is infraphylum Agnatha known for?

Answer 7

Jawless fish

Question 8

What are the classes under infraphylum Agnatha?

Answer 8

• Class Conodonta (extinct)
• Class Myxini: hagfish (slime eels)
• Class Hyperoartia: lampreys

Question 9

What are elements of Class Conodonta?

Answer 9

Tooth-like mineralized structures

Question 10

Describe ostracoderms.

Answer 10

Several groups of jawless fish covered in bony plates

Question 11

What are the characteristics of Class Hyperoartia?

Answer 11

• Toothed, funnel-like sucking mouth
• Herbivorous and carnivorous (parasitic on live fish)
• 4 different types of chambered blood pumping ‘heart’

Question 12

What are the characteristics of Class Myxini?

Answer 12

• Skull but no true vertebrae
• Bottom feeders
• Can release slime or mucus as a defense
• Skin can be used as leather for clothing

Question 13

When did jaws in fishes evolve?

Answer 13

~430 million years ago from the 1st gill arch

Question 14

What is Class Placodermi known for?

Answer 14

First jawed fish with simple beak-like jaws made of bone plates

Question 15

What are the features of Class Chondrichthyes?

Answer 15

• Skeletons primarily composed of cartilage
• Jawed, teeth and vertebrae sometimes calcified
• Lack a swim bladder
• Paired fins (pectoral)

Question 16

What are the subclasses of Class Chondrichthyes?

Answer 16

• Subclass Elasmobranchii: sharks, rays, skates, and sawfish
• Subclass Holocephali: chimaeras

Question 17

What is the significance of the superorder Selachimorpha?

Answer 17

Includes sharks with 8 extant orders and 5 extinct

Question 18

What is the superorder Batoidea known for?

Answer 18

Includes skates, rays, sawfish, and electric rays

Question 19

What is Super Class Osteichthyes?

Answer 19

Bony fish, largest group of living vertebrates

Question 20

What percentage of Osteichthyes are marine?

Answer 20

59%

Question 21

What are the adaptive traits of Teleost fishes?

Answer 21

• Reduction in bony elements
• Modification of gas bladder
• Form and position of paired fins
• Position and number of dorsal fins
• Modification of bony elements of the caudal fin

Question 22

What is the significance of the coelacanth?

Answer 22

A Lazarus taxon, known as a living fossil

Question 23

What are the characteristics of Class Dipnoi?

Answer 23

• Freshwater lungfishes
• Can breathe through primitive lungs
• Tooth plates formed on interior bones
• Build burrows in times of drought

Question 24

List the subdivisions of Teleosts.

Answer 24

• Osteoglossomorpha
• Elopomorpha
• Otocephala
• Euteleostei

Question 25

What is the most recent radiation of teleosts?

Answer 25

Subdivision Euteleostei

Question 26

What is the importance of phylogenies?

Answer 26

They help understand the evolutionary relationships and traits of organisms

Question 27

True or False: All jawed fish belong to the class Osteichthyes.

Answer 27

False