Bio 2: Chp 34

Chordate key characteristics (4)

Notochord
Dorsal, hollow nerve cord
Pharyngeal slits/clefts
Muscular, post-anal tail

Notochord fxn

Provides skeletal support throughout most of the length of a chordate

Dorsal, hollow nerve cord fxn

Develops into CNS

Pharyngeal slits/cleft fxn

Suspension-feeding structures
Gas exchange in some vertebrates
Develop into parts of inner ear, head, & neck

Muscular, post-anal tail

Provides propelling force in aquatic species

Lancelets (Cephalocordata)

Retain characteristics of chordate body plan from larval to adult
They’re the chordate poster-child

Tunicates (Urochordata)

Resemble chordates in larval stage
Adults only retain the pharyngeal slits/clefts
Shoot water through siphon when attacked

Derived vertebrate characteristics

Have vertebrae
2 or more sets of Hox genes
Neural crest cells

Fate of neural crest cells

Teeth
Some bones & cartilage of skull
Neurons
Sensory capsules

Cyclostomes (2)

Vertebrates w/out jaws
Hagfish & Lampreys

Hagfish characteristics

Produce a ton of slime from rows of glands

Lamprey characteristics

Parasites that feed by clamping mouth into live fish

Conodonts

First vertebrates
Mineralized mouthparts

Gnathostomes characteristics

Jaws w/ teeth
Duplication of Hox genes
Enlarged forebrain
Enhanced smell & vision
Lateral line system

Chondrichthyans organisms

Sharks, rays, etc.

Chondrichthyans characteristics

Skeleton composed primarily of cartilage

Features of sharks

Fast in straight line
Swim continually
Cloaca: common external opening for everything

Osteichthyes characteristics

Have bony skeleton

Osteichthyes groups (2)

Bony fish
Tetrapods

Fish characteristics

Gills protected by operculum
Control buoyancy with swim bladder
Lateral line system: orients fish in water

Ray-finned fish

Supported by long, flexible rays
Stereotypical fish

Lobe-finned fish

Have muscular pelvic & pectoral fins
Coelacanth, Lungfish, and Tetrapods

Derived characteristics of tetrapods

4 limbs w/ digits
Neck
Fusion of pelvic girdle to backbone
No gills
Ears

Tiktaalik

Shows both fish & tetrapod characteristics

Common traits of amphibians

Live aquatically & terrestrially
Have moist skin that fxn in gas exchange

Amphibian orders (3)

Salamanders
Frogs
Caecilians

Salamander characteristics

Amphibians w/ tails
Pedomorphosis: retention of juvenile features in sexually mature organism

Frog characteristics

Lack tails
Powerful hind legs
Tadpoles have lateral line system & gills

Caecilians

Legless
Resemble earthworms

Amniotes groups (3)

Reptiles
Birds
Mammals

Amniotic egg significance

Key adaptation for life on land
Amnion is fluid-filled sac that surrounds, bathes, & cushions embryo

Reptile key characteristics

Scales protect skin from desiccation & abrasion
Lay shelled eggs
Are ectothermic

Reptile lineages (4)

Turtles
Lepidosaurs (tuataras, lizards, & snakes)
Crocodilians
Birds

Turtle key characteristics

Boxlike shell fused to vertebrae, clavicles, & ribs

Tuatara key characteristics

No external ears
Nocturnal
Third eyespot
New Zealand (only)

Lizard key characteristics

External ear
Eyelids

Snake key characteristics

No external ear
No eyelids
Carnivorous

Crocodilians key characteristics

Semi aquatic reptile upturned nostrils

Birds key characteristics

Feathers
No urinary bladder
One ovary
Small gonads
Teethless
Honeycombed bone structure

Oldest known bird?

Archaeopteryx

Derived traits of class Mammalia

Mammary glands
Hair
Fat
Kidneys
Endothermic
Larger brain
Differentiated teeth
Extensive parental care

Human Domain

D - Eukarya

Human Kingdom

K - Animalia

Human Phylum

P - Chordata

Human Class

C - Mammalia

Human Order

O - Primates

Human Family

F - Hominidae

Human Genus

G - Homo

Human Species

S - sapien

Monotreme characteristics

Lay eggs
Lack nipples
Echidnas & Platypus

Marsupials

Embryo develops w/in placenta in mom’s maternal pouch = marsupium

Eutherian characteristics

More complex placenta
Longer pregnancies
Complete embryonic develop w/in uterus joined to mom by placenta

Primates key characteristics

Fully opposable thumb
Forward facing eyes
Well developed cerebral cortex

Monkey characteristics

Long tail
Smaller
Diurnal

Ape characteristics

Reduced tail
Larger
Longer arms
Family Hominidae

Human key characteristics

Upright posture
Bipedal locomotion
Complex thought
Complex tools
Reduced jawbones/muscles
Shorter digestive tract

Main difference b/w human & chimp genome

Changes in regulatory genes have largest effects

Hominin?

Study of human origins = paleoanthropology
Hominin = human adjacent species

Hominin origins

6-7 mya
Show evidence of small brains & increasing bipedalism
Teeth were larger & jaws more projected
Smaller in stature

Hominin Clarification #1

Early hominins were NOT chimpanzees

Hominin Clarification #2

Human evolution is NOT like a ladder that leads directly to Homo sapiens

Australopiths

Bipedal
Small brain & body

Homo habilis

Stone tools = “handy man”

Homo Ergaster

Large brained
Well adapted hip joints for walking long distances

Homo Erectus

First to leave Africa

Neanderthals

Thick boned
Largest brain
Buried their dead
Made hunting tools

Homo sapiens

Symbolic & sophisticated thought

Homo Naledi

Fully bipedal
Fine motor skills

Homo florensis

Indonesia
Much shorter
Smaller brains