Vertebrate Beginnings (Chordates) Flashcards
How many extant vertebrate species are there?
> 67 000
How are the vertebrates broken down my groups?
49% fish
11% amphibians
15% non avian reptiles
16% avian reptiles (birds)
8% mammals
Bilateral symmetry and segmentation become common in what period
Cambrian explosion
What happened during Cambrian explosion?
When most of the modern phyla appeared - including the phylum chordates
Major transformations of vertebrates
-inner support: notochord and then backbone
-jaws
-teeth and bone
-fin to limb
-water to land
-feathers and fur
-Endothermy
-return to water
-flight
Homologous
Traits that share common ancestry
-may have different functions
Analogous Structures
Characteristics or features similar due to convergent evolution, not shared ancestry
Chordates and only a few groups of invertebrates are ______
Deuterostomes
Why are echinoderms puzzling
-are free moving yet radial
-evolved from bilateral ancestor
-larvae are still bilateral
Radial symmetry more for sessile than moving
All vertebrates are _____
Chordates
Chordata is a the phylum
Non vertebrate chordates include which two groups
Cephalochordata
Urochordata
What 5 things make a chordate
- Notochord
- Dorsal hollow nerve cord
- Paired pharyngeal splits (gill slits)
- Endo style or thyroid gland
- Post-anal muscular tail for propulsion
Notochord
-flexible but semi-rigid rod to which muscles attach
-stiffens the body
-persists throughout life in amphioxus and jawless vertebrates
-present at embryonic stage in other chordates
Dorsal hollow nerve cord
Single, hollow nerve cord is dorsal to notochord and gut
-anterior end enlarged in vertebrates to form a brain
Notochord extends ______ to nerve cord in amphioxus
Nerve cord extends _____ to notochord in vertebrates
Anterior
Anterior
Paired pharyngeal slits (gill slits)
-gill slits related to filter-feeding in non-vertebrate chordates and respiration in vertebrates (fish)
-in amphioxus, gill slits open into atrium (not into water)
Endo style (thyroid gland)
-assists with feeding (non-vertebrate chordates)
-secretes mucous strands that trap food particles
-homologous to thyroid gland of vertebrates
After food is captured by Endo style, where is it moved?
Hepatic cecum where they are digested within cells
Why is the Endo style homologous to thyroid
Both bind iodine
Endo style of lamprey metamorphoses into thyroid gland of adult lampreys
Post anal muscular tail
Propels animal forward, at least during swimming portion of an animals life
(Humans don’t have one past development)
Cephalochordata:
Genus Branchiostoma
Common names
Lancelets (amphioxus) “sharp ends”
-coastal marine species, worldwide
Is amphioxus alive today?
Yes
Branchiostoma (amphioxus) characteristics
-small (3-7cm)
-slender (diffusion through body)
-filter feeders, mostly buried in sediment
-sexes separate but no dimorphism (no size difference)
-26 pairs of gonads (testes or ovaries)
Nutrient, water and gas exchange of amphioxus
Oral cirri= sensory devices and filter
Food and water enter mouth; cilia in mouth and pharynx drive movement
Water moves through gills to space (atrium) and exits the atriopore
Good trapped in Endo style (mucous gland) then digested in hepatic cecum and intestine, exits through anus
Gas exchange is done over body surface, not gills or blood
Support and movement of amphioxus
-semi-rigid notochord combined with V-shaped myomeres (muscle segments)
-post anal tail
-dorsal hollow nerve cord
Which group of the Cephalochordates is closer in relation to humans
Urochordates (tunicates) are more similar to vertebrates
Urochordates (Tunicates)
-habitat
Adults of almost all species are sedentary in shallow areas
Sedentary adults have little resemblance to other chordates (no notochord or tail)
What are the most well known Tunicates
Ascidians (sea squirts)
Why are Tunicates called what they are?
Named for tunic or cellulose cover
When touched they squirt water out of siphon
The larval or adult form of Tunicates have all 5 chordate parts?
Larvae
Adults only have pharyngeal slits and Endo style
Larvae of Tunicates mobility
Free swimming
What evidence suggests that our closest non-chordate relative is Urochordates (Tunicates)
Molecular data
Tunicates have some traits of vertebrates like the neural crest tissues
What is the hypothesis of the common ancestor of tunicates and vertebrates
Sessile adult form derived
Although we are more closely related to the tunicates, the ancestral chordate probably resembled a _____
Cephalochordate (amphioxus)
Characteristics of vertebrates
-expansion of brain and sensory system: nerve cord extends more anterior than notochord; and has a relatively large brain and better defined head; more sensory organs including paired eyes and ears
-expanded respiration with a muscular pharynx and external gill slits with gill arches
-heart and circulatory system
-dorsal fun (increased swimming ability)
Lamprey larva: Ammocoete larva lifestyle
-sedentary filter feeder form for 3-7 years
Vertebrate traits in Ammocoetes
-gill arch skeleton (branchial basket)
-muscular pharynx with external slits
(Draw water into mouth, gills pump it out)
-larger brain
-eye
-medial nostril
-auditory vesicle
-chambered heart
-nerve cord extended anterior to notochord
-dorsal fun
-heart
Differences in non-vertebrate chordates (amphioxus) and early vertebrate chordates (ammocoetes; adult)
Non
-filter feeding using cilia
-gills function in feeding
-respiration through skin
-notochord (no vertebral elements)
Vert:
-muscular pharynx pumps food and water into mouth
-gills function primarily in respiration: water pumped through gills and external hill slits for O2 and CO2 exchange
-vertebral elements surrounding notochord, at least in embryo
-expanded brain and sensory structures
Upgrades from non- vertebrate chordate to vertebrate chordate
Upgrade in structures (respiration, brain and sensory organs) to find and digest food
Upgrade support higher metabolic rate and increased activity
Vertebral elements are made up of ______ in early vertebrates
Cartilage pieces called arcualia
(Present in lamprey)
Myomere difference in non-vertebrate chordates and vertebrates
W shaped in vertebrates
V shaped in non-vertebrates
Do non-vertebrate chordates have a heart
Not a true heart, blood moved by contracting regions of the vessels
Which geological era contains vertebrate life?
When was it established?
What parts make up it?
Phanerozoic era
541 mya began
Paleozoic
Mesozoic
Cenozoic
Metazoans
Animal kingdom
The vertebral column replaces the _______
Embryonic notochord
Additional unique characteristics of vertebrates
-Cranium (skull)
-Head with complex sense organs
-Pituitary (hormones regulator)
-Mineralized tissues (calcium deposits in tissues (bones, cartilage, enamel)
-muscular contractions (peristalsis)
-closed circulatory system
-3-chambered heart
-find or limbs present
3 subphyla of phylum chordata
Urochordata (Tubicata)
Cephalochordata (amphioxus/ lancelets)
Vertebrata (vertebrates)
Unlike Urochordates, cephalochordates retain ______ throughout their life
All 5 diagnostic chordate chracterisitcs
