Fishes: Evolution and Systematics Flashcards
What is evolution?
Genetic change through time
Define systematics.
Study of the relationships between extant/extinct organisms over time
What is phylogeny?
A visual representation of the evolutionary history and relationships between organisms
What does cladistics involve?
Constructing a phylogeny using traits of an organism
What is phylogenetics?
Constructing a phylogeny using molecular data
List the characteristics of infraclass Agnatha.
- 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
What is infraphylum Agnatha known for?
Jawless fish
What are the classes under infraphylum Agnatha?
- Class Conodonta (extinct)
- Class Myxini: hagfish (slime eels)
- Class Hyperoartia: lampreys
What are elements of Class Conodonta?
Tooth-like mineralized structures
Describe ostracoderms.
Several groups of jawless fish covered in bony plates
What are the characteristics of Class Hyperoartia?
- Toothed, funnel-like sucking mouth
- Herbivorous and carnivorous (parasitic on live fish)
- 4 different types of chambered blood pumping ‘heart’
What are the characteristics of Class Myxini?
- Skull but no true vertebrae
- Bottom feeders
- Can release slime or mucus as a defense
- Skin can be used as leather for clothing
When did jaws in fishes evolve?
~430 million years ago from the 1st gill arch
What is Class Placodermi known for?
First jawed fish with simple beak-like jaws made of bone plates
What are the features of Class Chondrichthyes?
- Skeletons primarily composed of cartilage
- Jawed, teeth and vertebrae sometimes calcified
- Lack a swim bladder
- Paired fins (pectoral)
What are the subclasses of Class Chondrichthyes?
- Subclass Elasmobranchii: sharks, rays, skates, and sawfish
- Subclass Holocephali: chimaeras
What is the significance of the superorder Selachimorpha?
Includes sharks with 8 extant orders and 5 extinct
What is the superorder Batoidea known for?
Includes skates, rays, sawfish, and electric rays
What is Super Class Osteichthyes?
Bony fish, largest group of living vertebrates
What percentage of Osteichthyes are marine?
59%
What are the adaptive traits of Teleost fishes?
- 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
What is the significance of the coelacanth?
A Lazarus taxon, known as a living fossil
What are the characteristics of Class Dipnoi?
- Freshwater lungfishes
- Can breathe through primitive lungs
- Tooth plates formed on interior bones
- Build burrows in times of drought
List the subdivisions of Teleosts.
- Osteoglossomorpha
- Elopomorpha
- Otocephala
- Euteleostei
What is the most recent radiation of teleosts?
Subdivision Euteleostei
What is the importance of phylogenies?
They help understand the evolutionary relationships and traits of organisms
True or False: All jawed fish belong to the class Osteichthyes.
False
