Ch 34 Chordates - Fish Flashcards
Three major groups of bilateral animals
1) Deuterostomes
2) Lophotrocozoa
3) Ecdysozoa
What clade of bilaterians do humans belong to?
Deuterostomia
All echinoderms are what?
Marine animals
Echinoderms have what kind of symmetry?
Secondarily evolved radial symmetry
From where did the symmetry of echinoderms evolve?
A bilateral ancestor
What kind of symmetry is exhibited by echinoderm larva?
Bilateral symmetry
Echindoerms have what kind of internal support system?
A calcium-containing endoskeleton
Endoskeleton
Internal skeleton
What is the internal support system of echinoderms composed of?
Plate or tiny, scattered bony elements
Are any of the echinoderms parasites?
No
How do echinoderms move?
Via a water-vascular system
Water-vascular system
Fluid is pushed from muscular ampullae into tube feet, causing them to extend
What two things typically cover the surface of echinoderms?
1) Spines
2) Pedicellariae
Pedicellariae
Tiny jaws
Pedicellariae serve what purpose?
They keep the surface clear of debris and parasites
Catch collagen
Changes rapidly between solid and liquid states in response to stimulation from the nervous system
What is a unique connective tissue of echinoderms?
Catch collagen
What kind of symmetry is observed in sea cucumbers?
Secondarily evolved bilateral symmetry
How do sea cucumbers digest organic matter
In ingested sediment
How is the digestive system of sea cucumbers used as a defensive mechanism?
It can be expelled (and regenerated)
Four shared derived characters of chordates
1) Notochord
2) Dorsal, hollow nerve cord
3) Pharyngeal slits/clefts
4) Muscular, post-anal tail
Notochord
A semi-rigid rod of cells enclosed by a fibrous sheath
Function of the notochord
Functions as a skeletal muscle
Nerve cord
Dorsal and hollow
Runs length of body
Pharyngeal slits
Openings in the pharyngeal cavity (throat) to the outside of the animal
In later chordates, what gave rise to the structures of the middle ear, tonsils, and internal gills?
The evolution of pouches between the pharyngeal slits
Post-anal tail
Muscular
Evolved for locomotion in water
Two clades of the chordates that divered early in the evolution of vertebrates
1) Cephalochordata
2) Urochordata
Cephalochordates (lancelets)
Small, thin filter feeders
Found in sandy bottoms in coastal waters
Cephalochordates lack what?
1) Gills
2) Heart
Cephalochordates posses what?
A closed circulatory system
Are urochordates or cephalochordates more closely related to chordates?
Urochordates
How do urochordates (tunicates) feed?
Filter feeding
Draw water in through an incurrent siphon
Do all urochordates (tunicates) posses all four chordate traits?
No, only the free-swimming larva have all four traits
Craniates
Chordates that have a head
Craniates posses what?
1) Heat with at least two chambers
2) Red blood cells with hemoglobin
3) Kidneys
Neural crest
Feature unique to craniate embryos
The neural crest gives rise to what structures?
Some bone of the cartilage of the skull
Haikouella
Among the most primitive of chordate fossils
How long ago did Haikouella live?
530 mya
Haikouella possesed what?
1) Well formed brain
2) Eyes
3) Muscular segments
Haikouella lack what?
A skull
Is “fish” a good monophyletic group within the chordates?
No
Two groups of jawless fishes
1) Myxini
2) Petromyzontida
Myxini skeletal system
Notochord only “backbone”
Petromyzontida skeletal system
Fibrous and cartilaginous skeleton
Myxini braincase
Cartilaginous braincase
Petromyzontida braincase
Cartilaginous braincase
Myxini fins
No paired fins
Myxini digestion
No stomach
Petromyzontida fins
No paired fins
Petromyzontida digestion
Distinct stomach
Myxini circulatory system
Partially open circulatory system with four hearts
Petromyzontida circulatory system
Closed circulatory system with one heart
Gnathostomes
Chordates with jaws
Gnathostomes include (six):
1) Sharks, etc
2) Ray-finned fishes
3) Lobe-finned fishes
4) Amphibians
5) Reptiles (including birds)
6) Mammals
Two advantages of jaws
1) Improved respiratory efficiency
2) Facilitated prey handling
How did jaws improve respiratory efficiency?
Closing jaws prevent backflow when water is passed over the gills
How did jaws facilitate handling prey?
They allows for grasping, biting, and suction feeding
From what structures may the jaws of gnathostomes evolve?
Skeletal supports of the pharyngeal slits
What are the earliest gnathostomes in the fossil record?
Placoderms
Placoderms
An extinct lineage of armored vertebrates
How long ago did placoderms live?
450 mya
Chondricthyans have a skeleton composed primarily of what?
Cartilage
The largest and most diverse group of chondrichthyans include what?
1) Sharks
2) Rays
3) Skates
What is a derived trait of chondrichthyes?
The lack of mineralization in their cartilaginous skeleton
The vertebrate ancestors of chondrichthyes possessed what?
Calcified bony skeletal elements
What kind of scales are found on chondricthyans?
Placoid
Placoid scales
Modified to form horns, spines, and teeth
The teeth of skates and rays are modified into what?
Plates for crushing molluscs, crustaceans, or fish
What is one intestinal adaptation of the chondrichthyans?
Spiral valve
Spiral valve
Slows the passage of food and increases the surface area for absorption
What contributes to buoyancy in sharks?
A huge, oily liver
Why must sharks continually swim?
Because they are denser than water and will sink if they stop swimming
Claspers
Modifications of the pelvic fins used in copulation
Are shark eggs fertilized internally or externally?
Internally
Three ways shark eggs develop:
1) Oviparous
2) Ovoviviparous
3) Viviparous
Oviparous
Eggs hatch outside the mother’s body
Ovoviviparous
The embryo develops within the uterus and is nourished by the egg yolk
Viviparous
The embryo develops within the uterus and is nourished through a yolk sac placenta from the mother’s blood
What clade of gnathostomes do a vast majority of vertebrates belong to?
Osteichthyes
Osteichthyans include:
1) Bony fish
2) Tetrapods
Actinopterygii
Ray-finned fishes
Nearly all the familiar osteichthyans belong to what?
The Acinopterygii
Osteichthyans have what kind of skeletal system?
A bony skeletal system
What covers the gills of osteichthyans?
A plate-like operculum
Operculum
Allows fish to breath efficiently without forward movement
How are bony fishes more diverse than the chondricthyes?
They have more diverse teeth and digestive system
What increased swimming efficiency and maneuverability in bony fishes?
The evolution of a gas bladder
