Download Chapter 34 Vertebrate Evolution and Diversity Phylum Chordata

Chapter 34
Vertebrate Evolution and Diversity
Phylum Chordata
- 3 subphyla: 2 invertebrate subphyla
Vertebrata
- 4 anatomical features at some point in life:
notochord
- long, flexible rod between guy and nerve cord
- supports adult in some invertebrate chordates
- becomes gelatinous material between intervertebral discs in most
vertebrates
dorsal hollow nerve cord (solid in other phyla) – develops into brain, spinal cord
pharyngeal slits - permits water entering mouth from having to travel through entire
digestive system (AKA gill slits)
- used for suspension feeding in invertebrate chordates
- become modified for gas exchange in many vertebrates
muscular postanal tail
- propulsive force
Subphylum Urochordata
- tunicates (sea squirts)
- marine; adhere to rocks, etc.
- filter feeders
- no notochord, nerve cord, or tail (only pharyngeal slits)
- free-swimming larvae
Subphylum Cephalochordata
- lancelets (bladelike shapes); marine filter feeders
- adults have notochord, nerve cord, gill slits, postanal tail
- feeble swimmers
Vertebrates
neural crest
- features:
- embryonic cells found only in vertebrates
- help form structures such as cranial bones and cartilage
greater cephalization - brain and sense organs on anterior end
skeleton
- cranium and vertebral column as main axis of body
axial skeleton
cranium
- protects brain
vertebral column
- support
ribs
- protect internal organs
appendicular skeleton - 2 pairs of appendages
- 2 major superclasses: Agnatha
- no jaws
Gnathastomata - have jaws
Superclass Agnatha
- jawless vertebrates
- lampreys
- ell-shaped
- rasping mouth parts; feed by clamping round mouths onto fish
- penetrate skin and feed on blood
hagfishes
- scavengers; no rasping mouth parts
Superclass Gnathastomata
Class Chondrichthyes - cartilaginous fishes
- skeletons made of flexible cartilage; well-developed jaws; paired fins
sharks - streamlined bodies; swift swimmers
- tails propel through water
- dorsal fin stabilizes; pectoral and pelvic fins for lift
- most must swim continuously to provide water flow through mouth and over gills
- most are carnivorous; teeth evolved from scales
- sharp vision and olfactory sense
- lateral line
- 2 rows of microscopic organs along flanks
- sensitive to water pressure changes and detects vibrations in water
- internal fertilization
- cloaca - common chamber for reproductive, digestive, and excretory systems
rays
- bottom-dwellers
- flattened bodies
- jaws crush mollusks, crustaceans
- enlarged pectoral fins for propulsion
- whiplike tail
Class Osteichthyes
- marine and fresh waters
- bony skeleton
- flattened bony scales cover skin
- skin glands produce mucus
- lateral line
(row of tiny pits on both sides)
- gas exchange - water drawn in mouth, through phaynx, and out over gills
operculum
- covers gill chamber
- moves back and forth
- swim bladder - dorsal to digestive tract
- contains gases; provides buoyancy
- flexible fins (maneuverable swimmers)
- most have external fertilization
Class Amphibia - first vertebrates to move onto land
- most stay close to water (damp habitats)
- gas exchange through skin
- lungs aid gas exchange but are small and inefficient
- external fertilization in water
- 3 orders of amphibians:
salamanders
- some aquatic, some terrestrial
frogs/toads
- enlarged hindlegs for hopping
- sticky tongue to capture prey
- camouflage; poison skin glands
- many metamorphosize - larval stage called tadpole (gills, lateral line, etc.)
caecilians
- legless ; almost blind
- most burrow in tropical soils
Class Reptila
- several adaptations for land dwelling not seen in amphibians:
- scales (made of keratin) to prevent dehydration
- lungs
- internal fertilization
- oviparous
- produce amniotic egg (membranes) with leathery shell - prevents drying out
- some are viviparous - live young (some snakes, lizards)
- ectothermic - absorb solar energy to regulate body temperature
- most have 3-chambered heart (not crocs or gators  4)
- early reptiles - dinosaurs and pterosaurs (winged)
- dinosaurs may have been endothermic (kept bodies warm through their own metabolism)
- modern reptiles:
turtles - hard shell; all lay eggs on land
snakes - probably descended from burrowing lizards
- limbless
- carnivorous
- acute senses; no eardrums but sense ground vibrations
- some have heat-detecting organs
- flicking tongue carries odors to olfactory organs on roof of mouth
- poisonous snakes inject toxin with hollow fangs
crocodiles/ alligators - spend most time in water
Class Aves
- birds
- reptilian similarities: amniotic egg (but with hard shell), scales on legs
- adaptations for flight: hollow (honeycombed) bones - reduces weight
some organs are reduced (only 1 ovary in females)
strong pectoral muscles
air sacs (reduce body density)
- gizzard grinds food
- beak - made of keratin; no teeth
- endothermic (feathers, fat layer)
- 4-chambered heart
- feathers
- aid in insulation and flight
- made of keratin (evolved from scales)
- efficient circulatory system; 4-chambered heart (separates oxygenated from unoxygenated blood)
- efficient lungs attached to air sacs
- well developed nervous systems; complex behaviors
- internal fertilization
- wings
Archaeopteryx - share a common ancestor with modern birds
- clawed forelimbs, teeth, long bony tail, feathers
- may have been a tree glider
Class Mammalia
monotremes
marsupials
- hair made of keratin for insulation
- endothermic
- efficient respiratory system with a diaphragm
- 4-chambered heart (separates oxygenated from unoxygenated blood)
- mammary glands
- produce milk
- teeth of various sizes and shapes
- internal fertilization; most viviparous (placenta nourishes embryo)
- large brains; capable of much learning
- parent scare for young
- egg-laying mammals (oviparous)
- platypuses, echidnas
- hair, mammary glands
- opossums, kangaroos, koalas, etc.
- young born early; use forelimbs to climb from mother reproductive tract to marsupium
- marsupium - “pouch”; young attaches to a teat to complete development
placental mammals
- embryonic development completed in uterus
- placenta joins embryo to mother
some orders: Chiroptera
- bats (wings, nocturnal, some eat blood, some fruit)
Insectivora
- shrews
Lagomorpha - rabbits
Perissodactyla - odd-toed ungulates (horses, rhinos, etc.)
Artiodactyla
- even-toed ungulates (shhep, deer, etc.)
Sirenia
- sea cows
Proboscidea
- elephants
Cetacea
- whales, dolphins
Carnivora
- cats, dogs, raccoons, seals, bears
Rodentia
- rats, squirrels, beavers
Primates
- monkeys, apes, humans
Primates
- dexterous hands with opposable thumbs
- sensitive fingers; nails (no claws)
- eyes close together on front of face (enhanced depth perception)
- prental care
Old World Monkeys
- Africa, Asia
- tree and ground dwellers
New World Monkeys - South America
- all tree dwellers
Apes - 4 genera:
gibbons
orangutans
gorillas
chimpanzees
- large legs, short legs, no tails
- gorillas and chimps highly social
- larger brains than monkeys (more adaptable behavior)
Paleoanthropology
- study of human origins and evolution
first humans  Australopithecus africanus
- discovered 1924 (brain 1/3 that of modern humans)
- “Lucy” discovered in 1974 (40% complete)
Homo habilis
- larger brain, walked upright, used tools
Homo erectus - first hominid to migrate from Africa into Europe and Asia
- taller and larger brain than Homo habilis
- lived in huts or caves, built fires, wore animal skins, designed more refined tools
- descendants - Neanderthals
- Homo sapiens
Homo sapiens - could change environment to meet its needs
- didn’t need to adapt to environment through natural selection
- may be changing the world faster than species can adapt
- overwhelming rate of extinction due to habitat destruction and pollution
- global warming due to fossil fuel consumption
- destruction of tropical rain forests (which help maintain gas balance & moderate global
weather)
- may be creating the most devastating crisis in the history of life!