vertebrate diversity (PP21) Flashcards
explain and show chordate characteristics in humans
Notochord eventually forms spinal disks between vertebrae in our spine
Hollow dorsal nerve cord remains as our spinal nerve cord
Pharyngeal slits disappear during embryonic development
Post-anal tail eventually reduces during embryogenesis & no longer exists in adult
Coccyx (tail bone) = remains of a structure that is longer in many other chordates
what are the invertebrate chordates
Cephalochordates (
Urochordates
explainn cephalochordates and give an example
(e. g. Lancelets)
- Named for their blade-like (lance-like) shape
- Sessile as adults
- Marine suspension feeders that retain the characteristics of the chordate body plan as adults
explain urochordates and give an example
(e. g. Tunicates)
- Belong to the deepest-branching lineage of chordates
- Marine suspension feeders (commonly called sea squirts)
- Most resemble chordates during their larval stage (may be as brief as a few minutes) –only retain pharyngeal slits
explain class myxini and give examples
“Jawless fish” (Agnathostomes)
- Display all the features of craniates, but least derived
- Have a cartilaginous skeleton derived from notochord, but no vertebrae
- Not actually “vertebrates”
- Have teeth, but no jaw, and so generally dwell near the bottom of the ocean, or attach and feed parasitically off of other animals
ex: hagfish and lampreys
explain gnathosomes
Vertebrates with jaws
Jaws evolved from skeletal rods of pharyngeal slits
Enhanced sensory systems (including the lateral line system) Extensively mineralized endoskeleton Paired appendages (“limbs”)
What are the The earliest gnathostomes in the fossil record
extinct lineage of armored vertebrates called placoderms
explain class Chondricthyes and give example
“Cartilaginous fish”: internal skeletons of cartilage
Modified from mineralised skeleton
Posses a (toothy) jaw Allows consumption of tougher foods
Paired fins
Formation of vertebrae
Cartilage skeleton that forms around the dorsal hollow nerve cord
Internal fertilisation (involves physical copulation between male & female) The embryonic shark often develops inside the mother (live birth)
ex: sharks and rays
explain Class Actinopterygii and give example
“Bony fish”: mineralized (ossified) calcium-based skeletons
Similar composition to mammalian skeleton
Most use external fertilisation (oviparous)
Some fish fertilize internally like chondrichthyes
Scales & mucus secretion to reduce drag
Use gills to extract oxygen from the water
Air can be stored in a swim bladder
Gas stored or released to maintain buoyancy
ex:rayfish
explain Sarcopterygii
Also “bony fish”: mineralized calcium-based skeletons
Developed sturdy, skeletally supported, lobe-like fins
Groundwork for terrestrial limb
Divided into 2 classes:
Actinista (Coelocanths)
Deep-sea species thought extinct until capture in 1938
Dipnoi (Lungfish)
Have primitive lungs (possible that ancestors capable of breathing air directly)
explain tetrapods
-Gnathostomes with 4 locomotory limbs (able to walk)
(Evolutionary advantage to living on land, even if partially because they can avoid marine predators)
Terrestrial environment would provide a large variety of food & resources without many initial competitors
Prior to tetrapods, very few animals had transitioned to become terrestrial: great potential for the first tetrapods
explain class amphibia
Amphibians: ~5500 species
-First terrestrial tetrapods
For earlier organisms that originate from the water, there -must be a good way of keeping wet
-Most amphibians have moist skin that complements the lungs in gas exchange
-Bones & structures require additional strength to counter gravity
-Reproduction requires assistance (ancestor relied on external fertilisation)
what was the solution to ambient who needed assistance for reproduction
Solution: lead “double” lives - spend portions of their lives in both land & water
To successfully mate, intercourse must take place in the water
Zygote develops in water (tadpole)
Tadpoles resemble simple chordates (gills, no limbs)
As the amphibian matures, it will grow limbs & eventually become terrestrial, relying on its lungs to breath
what are amniotes and explain
Group of tetrapods including reptiles, birds, mammals
Named for the amniotic egg (major derived character of the clade)
Contains specialized membranes that protect the embryo
Other terrestrial adaptations:
Relatively impermeable skin
Ability to use rib cage to ventilate the lungs
what are the parts of the amniotic egg
Amnion
Yolk sac
Allantois:
Chorion
