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Bsc 111 Test 2 Chapter 29
Terms in this set (18)
Describe the four features that define the Phylum Chordata.
1. notochord-longitudinal flexible rod between digestive tract and nerve cord
-present at some point in all chordate embryos
-retained in invert and basal chordate groups, replaced in vertebrates by backbone (except disks)
2. Dorsal, hollow nerve cord-nerve cord is ectoderm in origin; formed as a rolled tube; develops into the brain and CNS-differs from other animals, usually ventral and solid nerve cord
3. Pharyngeal slits or clefts-slits in pharynx (posterior to mouth)
-allows water to enter mouth and exit-functions in suspension feeding in invert chordates
-modified into various structures (gills, jaws, hearing)
4. muscular, post-anal tail
-tail past anus
-with muscles for propulsion
What is the basic Urochordate body plan? Why is it still a chordate?
-sessile, marine suspension feeders; mucus net covers pharynx, captures food
-tunic = covering of cellulose -like carbohydrate
-tunicate does not look much like a chordate, but the larval form does.
It's still a chordate because of the larval form (I guessed)
How do cephalochordates demonstrate the basic chordate body plan?
-lancelet body plan (Fig. 29.2)
-basic chordate body plan(all defining features of the phyla persist in the adult organism)
-ecology -small, infaunal marine animals; suspension feeders with tentacles not common usually, but may be locally abundant (e.g. GOM -sturgeon food)
-swimming -like a fish musculature occurs in serial blocks (somites) -like vertebrates
What characters define the Vertebrata?
1. vertebral column -notochord replaced by bony or cartilaginous column (support and protects nerve cord)
2. cranium (& brain) -brain case with enlarged anterior end of dorsal nerve cord
3. endoskeleton of cartilage or bone
4. Other characteristics:
Chapter 29-Vertebrate Evolution 2-multiple clusters of Hox genes, greater diversity of organ systems (e.g., liver, kidney, etc...)
Briefly describe the two groups of agnathans (cyclostomes).
cyclostomes-jawlessfishes (name = circle mouth); no appendages
A. Hagfish (Myxini)
1. with cranium but lack vertebral column(secondarily lost)
skeleton = cartilage with notochord for support and locomotion
2. marine scavengers (about 30 species)
3. slime glands -predator defense
B. Lampreys (Petromyzontida)
1. rudimentary vertebral column (backbone), but not ossified -skeleton still cartilage
2. about 35 species -predators and external parasites
3. life history in some -larvae in freshwater (like a lance-let); adults in ocean
What advantages did the gnathostomes have over the cyclostomes?
Why gnathostomes ruled -advantages of jaws and paired fins-jaws (with teeth) -gripping & handling of food, no longer just suspension feeding -> predators-paired fins -greater mobility -> better predators
What is the origin of the jaw?
Origin of jaw: B. Origin of jaws (Fig. 29.7)
1. modification of support elements of pharyngeal slits
2. some slits retained as gills (respiration)
Briefly describe the two groups of bony fishes.
a. Actinopterygii (ray wings)
-ray-finned fishes- most familiar of fish groups; fins supported by rays-examples of diversity
b. lobe-finned fishes(Sarcopterygii)
-Actinistia& Dipnoi & tetrapods '
-pectoral and pelvic fins
-muscular with skeletal support mostly extinct except for three lineages; example
-Latimeria-the coelacanth; thought extinct until rediscovered in 1938
-lungfishes (Dipnoi) Southern Hemisphere distribution limited # of species extant, but common during Devonian
-have functional lung to aid in gas exchange; live in low O2 environments
What is the evolutionary origin of tetrapods?
A. Evolution of tetrapods -from lobe-finned fish ancestor
1. tetrapod= vertebrates with skeleton-supported legs, not fins
2. intermediate tetrapods
-400-350 mya is transition to land
-skeleton of intermediate fishes much like that of terrestrial tetrapods
-steps in the origin of limbs with digits
-adaptations to life in shallow aquatic environments & use of lungs to breath air were prelude to life on land
Although mostly terrestrial, why are amphibians still closely tied to water?
Still closely tied to water
-gas exchange through skin
-require moist environments-many require water for reproduction (eggs dry out easily)
Describe the features of the amniotic egg and why it was important for the evolution of terrestrial tetrapods.
key toterrestrial transition = amniotic egg -allowed reproduction away from water
-structure of amniotic egg (Fig. 29.16)
-more than just a hard shell-series of extra embryonic membranes creates a protected environment for the embryo
1) amnion -surrounds embryo with fluid -protection / shock absorber
2) yolk sac
3) allantois -waste disposal
4) chorion -surrounds everything / respiration
What are the phylogenetic relationships among the major amniote groups?
-Parareptiles(anapsids) includes turtles? / otherwise extinct
-Diapsids-reptiles, birds & dinosaurs
-Lepidosauria-tuatara and squamates (lizards & snakes)
-Archosauria-crocodiles, birds & dinosaurs
Birds fall into the reptile category.
Explain why Class Reptilia without birds is a paraphyletic grouping.
birds are a problem for cladistic systematists
-Class Reptilia = paraphyletic w/o birds
What characteristics make reptiles successful terrestrial organisms?
-The adaptation of the shelled egg
- Waterproof skin (tegument)
- More efficient respiration movements
- water conserving kidneys
- internal fertilization
Describe the main groups of extant(living)reptiles.
1. Testudine-turtles -ancient lineage
2. Squamata-lizards and snakes; most diverse group
3. Crocodilia -crocs and gators; largest individuals; closest living relative of birds
What features distinguish birds as a group?
1. bones -honeycomb look -strong but light
2. endothermic; also efficient respiration and circulation
3. sensory development -good vision; large brain areas for senses and locomotion
4. feathers -modified scales (keratin)
5. wings -modified forelimbs; airfoil effect; soaring, hovering, speed
6. beak (keratin) -diversity of shapes / functions
What features distinguish mammals as a group?
1. hair (keratin)
2. mammary glands -milk production
3. endothermic; efficient respiration & circulation
4. placenta (not all groups) -formed by uterus and extra embryonic membranes
5. larger brains (per size)6. teeth specialization
What are the three main groups of mammals.
1. Monotremes-platypus & echidna
2. Marsupials-opossums, kangaroos, etc..
3. Eutherians (placentals)
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