Topic 27: clade vertebrata Flashcards
Ancestral chordates may have resembled
lancelets
The same ___ genes that regulate vertebrate brain development are expressed during the development of
lancelet’s simple nerve cord tip
Hox
chordates evolved into invertebrates during the:
Cambrian period
Vertebrates
chordates that have a backbone
_______ allowed vertebrates to become more efficient at capturing food and evading predators
A skeletal system and complex nervous system
Vertebrate shared, derived traits
- Vertebrates have a vertebral column (backbone)
- Elaborate braincase enclosing brain
- two or more sets of Hox genes
- Neural crest cells
- Dorsal, ventral, and anal fins stiffened by fin rays
- Modified circulatory system
what protects nerve cord
Skeletal elements (cartilage or bone) enclose and protect the nerve cord
___ replaces the notochord
vertebral column
Vertebrate brain enclosing included
Head consists of a brain, sense organs, including paired eyes, and a cranium (skull) without jaws
A cranium allowed for
evolution of more complex nervous system to coordinate more complex movement and feeding behaviours
vertebrate Hox genomes arose due to
whole-genome duplication
Hox genes control
the body plan of an embryo along the head-tail axis; determine the type of segment structures that will form
Benefit of neural crest cells
Neural crest cells develop along the edge of the neural tube of vertebrate embryos and eventually forming various structures, e.g. teeth, some bones/cartilage of the skull, several types of neurons (nerves)
Fins
- are membrane extensions supported by cartilaginous or bony spines (rays)
- provide balance and propulsion while swimming
Modification to the circulatory system in vertebrates
- closed circulatory
- heart with at least two chambers
- hemoglobin in red blood cells
- kidneys
hagfishes and lampreys lack
backbone and jaw
Chordates evolved into the
vertebrates
earliest vertebrates
Conodonts
vertebrates that have jaws are called
gnathostomes
Shared, derived traits of gnathostomes
- Opposing jaws that open/close the mouth forcefully to capture and process diverse foods
- mineralization of the skeleton
- two pairs of lateral appendages
- gene duplication (incl HOX genes)
- enlarged forebrain for smell and vision
- lateral line system that is sensitive to vibrations
Two pairs of _____ that had supported pharyngeal slits were modified to pump water over the gills by opening and
closing the mouth more effectively
skeletal rods
Posterior pharyngeal rods evolved to
specialized supports for gas exchange (gill slits)
Mineralization with calcium phosphate appears to have originated with ______
vertebrate mouthparts
were first vertebrates with mineralized skeletal elements in their mouth and pharynx
Conodonts
Natural selection for mineralization of mouthparts would have led to selection for ______
stronger and tougher mechanism for opening
and closing the mouth, i.e. true opposing jaws
Two types of bones
- Endoskeleton is derived from preformed cartilage
2. Dermal skeletons are bony structures derived from intramembranous ossification
How gnathostomes get bony
cartilage becomes ossified (bony) with calcium phosphate as the embryo develops.
Cartilage
a “flexible connective tissue with an abundance of collagenous fibers embedded in chondroitin sulfate”
placoderms
an extinct lineage of armored vertebrate fish that are the earliest gnathostomes fossils
Three lineages of extant gnathostomes
chondrichthyans, ray-finned fishes, and lobe-fins
Chondrichthyans
cartilaginous fish (Endoskeleton of cartilage, but have bony teeth and bony placoid (pointed, tooth-shaped) scales)
