Lecture 18: Deuterostomes 1 Flashcards
What are the three groups of deuterostomes?
in order of importance
1.Hemichordates: acorn worms, pterobranchs
2.Echinoderms: sea stars and sea urchins
3.Chordates: lancelets, tunicates, vertebrates
Vertebrates includes tetrapods and other fish
What makes deuterostomes so diverse?
Adult body plans, feeding methods, modes of locomotion, and reproductive strategies
Ecolution is not a linear progression from simple to complex
What is an invertebrate?
Invertebrates are animals that are not vertebrates.
Vertebrates dominate in deuterostomes even though 95% of known animal species are invertebrates.
What phyla is pharyngeal gill slits a common feature of?
Chordates. But, it can also be in hemichordates. (lost in echinoderms)
What are echinoderms and what is their common niche? What 3 synapomorphies identify echinoderms as a monophyletic group?
Echinoderms (“spiny-skins”) are named for their spines or spikes. They are all marine animals.
3 synapomorphies:
1. Radial symetry in adults (bilateral in larvae)
2. Endoskeleton of calcium carbonate
3. Water vascular system and tube feet
What is the water vascular system and tube feet in echinoderms?
Water vascular system:
- Series of branching, fluid-filled tubes and chambers
- Sea water flows in and out of system
Tube feet:
- Important part ofw ater vascular system
- Elongated, fluid-filled appendages consisting of ampulla on inside and podium on outside
What is the endoskeleton (in echinoderms)?
Endoskeleton is hard protective and supportive struccture located inside thin layer of epidermal tissue.
Endoskeleton forms during development through secretion of calcium carbonate plates.
Is radially symmetric
In some species, plates fuse and form rigid case:
- Plates remain independent and flexible
- Tissue that connects plates is reversibly stiff or flexible depending on conditions
Elaborate on symmetry in echinoderms and its development throughout life?
Larvae are bilaterally symmetric as are all deuterostomes.
Adults are pentaradially symmetric (five-sided)
pentaradial symmetry originated early in echinoderm evolution
What are the 3 major lineages or subphyla of chordata?
- Cephalochordata
- Urochordata
- Vertebrates !!
What are cephalochordates?
lancelets or amphioxus
- Small, torpedo shaped animals with fish like appearance
- Mobile suspension feeders
- adults live on ocean floor, burrow in sand and suspension feed
- Dorsal hollow nerve cord runs parallel to a notochord, which stiffens body
- Muscle contractions result in fishlike movement
What are urochordates?
tunicates
- have external coat of polysaccharide (tunic) that covers and supports body
- three sub lineages are sea squirts, salps, and larvaceans
- urochordates are closest living relatives of vertebrates, considered a sister group
What species are included in vertebrates?
- Hagfish
- Lampreys
- Sharks and rays
- bony fishes
- amphibians
- mammals
- reptiles (including birds)
What are the most species-rich and ecologically diverse vertebrates?
Ray-finned fishes and tetrapods
Ray-finned fishes ->
- goldfish, tuna, salmon
- fins supported by bony rods
Tetrapods ->
- reptiles, amphibians, mammals
- large herbivores and predators in terrestrial environments
What are the vertebrate synapomorphies?
Cartilage: strong flexible tissue consisting of scattered cells in a gel-like matrix of polysaccharides and protein fibers
Bone: dense tissue consisting of cells and blood vessels encased in a matrix made of calcium phosphate
What are the earliest vertebrates?
Jawless fishes are the earliest vertebrates, dated to the cambrian explosion around 520 mya ago.
- has a cranium made of cartilage and possibly cartilaginous reinforcements to notochord
- has specialized neural crest cells and other cells responsible for brain, cranium, and sensory cell information
neural crest cells and cartilaginous cranium are synapomorphies for vertebrates
