lecture 6 Flashcards
what characteristics of the living hagfishes and lampreys suggest that their lineages arose very early in vertebrate evolution?
Hagfishes lack bone, paired fins, and scales in their skin. Hagfishes have neither a cranium nor vertebral column.
Lampreys have only rudimentary traces of vertebrae.
These observations suggest that their lineages arose before these structures appeared in vertebrates
what traits in conodonts and ostracoderms are derived (more advanced) relative to those in hagfishes and lampreys?
structures made of bone or bone-like material and, in some ostracoderms, a brain sub-divided into 3 regions
why was the evolution of jaws so important for the evolution of vertebrates? 4
- increased flexibility and efficiency
- increased diversity of diet
- more food= bigger individuals
- moveable fins increased agility in movements
how do the air bladder and fins of Actinopterygii increase their locomotor abilities?2
- allowing them to rise or sink easily in the water column.
2. Their fin rays allow them to engage in precise movements during locomotion
what characteristics do bony fishes possess that make them so competitive? 5
- strong light bones
- moveable fins
- scales and mucus (=streamlining and anit-bacterial)
- swim bladder (=improved buoyancy control)
- operculum (=improved breathing)
what characteristics of sharks make them more efficient predators than the acanthodians or placoderm? 4
- well developed sensory system to detect prey
- lightweight skeleton and absence of a heavy body armor allow them to ursue prey rapidly
- numerous teeth that are replaced when damaged or worn
- loosely attached jaws that permit them to suck in large chunks of food
How do the lungs of lungfishes allow them to survive in stressful environments?
allow them to survive in environments with low oxygen content because they can acquire oxygen from the air
Ghathostomata includes the evolution of 2 things?
- hinged jaws
2. movable fins
common name for myxinoidea
hagfish
petromyzontoidea common name
lampreys
which agnathan hasnt got a specialised structure around the dorsal nerve cord? (no rudimentary vertebrae)
myxinoidea -hagfishes
which agnathan has an oral disk
petromyzontoidea-lampreys
Condonts (cone tooth) :
2 identifying features (rest are in the phylogeny tree)
- movable eyes
2. bone/bone-like tissue: bone-like feeding structures made of dentine
2 characteristic of ostracoderms
- armored skin with bony plates and scales
2. no true vertebral column or fins
jaws evolved from…..
gill arches in the pharynx of jawless ancestor.
- one pair of ancestral gill arches formed bones in the upper and lower jaws
- 2nd pair attached the jaws to the cranium