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
4 functions of movable fins
- stability (e.g. dorsal fin and anal fin)
- steering (paired pectoral fins as well as paired pelvic fins)
- power and trust (e.g. caudal fin)
- deters predators
4 reasons why the development of the jaws and fins were so NB
- increased flexibility and strength
- increased diversity of diet
- more food= bigger individuals
- moveable fins increased agility in movement
3 characteristics of placoderms (could compare them with acanthodii= same characteristics are very different)
- covered by heavy bony plates & scales
- no separate teeth
- fins with internal skeletal support and muscle
3 characteristics of acanthodii (spiny sharks)
- smell, light scales, streamline bodies
- well developed eyes, large jaws and numerous teeth
- ventral spines and fins with internal skeletal support
chrondrichthyes are referred to as …branchs
elasmobranches
elasmobranchs (chondrichthyes )include 3 species
- skates
- rays
- sharks
skates and rays are both
dorsoventrally-flattened bottom dwellers
sharks 6 characteristics
- streamlined
- dominant predators
- flexible fins but not movable
- lightweight skeleton
- buoyant livers
- no gill cover- breathing=less efficient
Elasmobranch feeding adaptations 2
- teeth develop in spirals(new teeth migrate forward as old break off)
- digestive system modified to incr time food stays in digestive system and SA for absorption
Definition of olfaction
the sense of smell
elasmobranch sensory systems are composed of 4 things
1, vision
- olfaction - smell
- electroreceptors
- lateral-line system
what is the function of the electroreceptors of elasmobranch
to detect weak electric currents produced by prey
what is it and the function of the lateral-line system of elasmobranch
It is a row of tiny sensors in canals along both sides of the body
function = detects vibrations in the water
elasmobranch undergo internal/external fertilisation
internal
the embryos of elasmobranch are nourished in 3 ways
- produce large yolky eggs with tough leathery shells
- retain eggs within the oviduct until young hatch
- nourish young within a uterus
2 lineages of bony fishes
- actinopterygii-ray-finned fishes
2. sarcopterygii-fleshy-finned fishes
actinopterygii have fins supported by?
thin, flexible bony rays
sarcopterygii have fins supported by…..2
- muscles
2. internal bony skeleton
actinopterygii branch to form
teleosts e.g. seahorses
2 NB structures in teleost
- operculum
2. swim bladder
difference between reproduction of teleost reproduction in marine fishes vs freshwater fish
Marine= produce planktonic larvae-eggs fertilised and hatch in water
Freshwater= direct development - eggs hatch into baby fish or sometimes gives birth to live young (frequently parental care)
sarcopterygii species lobe-finned fishes example
- 2 species of the coelacanths in Indian ocean
sarcoptrygii have 2 species
- lobed-finned fish
2. lungfishes
NB adaptation lungfish have
primitive lungs supplement/ replace breathing with gills
