Transcript VERTEBRATE EVOLUTION AND DIVERSITY – Vertebrates have unique endoskeletons composed of: • A cranium (skull) • A backbone made of a series of bones.

VERTEBRATE EVOLUTION AND
DIVERSITY
– Vertebrates have unique endoskeletons composed of:
• A cranium (skull)
• A backbone made of a series of bones called vertebrae
Cranium
(protects brain)
Vertebra
Figure 17.26
Characteristics of Chordates
– Chordates (phylum Chordata) all share four key
features that appear in the embryo and sometimes
the adult:
•
•
•
•
A dorsal, hollow nerve cord
A notochord
Pharyngeal slits
A post-anal tail
Dorsal,
hollow
Notochord
nerve cord
Brain
Muscle segments
Mouth
Anus
Post-anal
tail
Pharyngeal
slits
Figure 17.27
– Another chordate characteristic is body
segmentation, apparent in the:
• Backbone of vertebrates
• Segmental muscles of all chordates
– Chordates consists of three groups of invertebrates:
• Lancelets are bladelike animals without a cranium.
• Tunicates, or sea squirts, also lack a cranium.
• Hagfishes are eel-like forms that have a cranium.
– All other chordates are vertebrates.
Mouth
Tail
Lancelet
Tunicates
Figure 17.28
Ancestral
chordate
Chordates
Tunicates
Lancelets
Hagfishes
Vertebrates
Lampreys
Cartilaginous
fishes
Bony fishes
Amniotes
Reptiles
Mammals
Figure 17.29
Tetrapods
Amphibians
(a) Hagfish (inset: slime)
Figure 17.30a
– Lampreys:
• Are vertebrates
• Have a cranium
• But lack jaws
(b) Lamprey (inset: mouth)
Figure 17.30b
– The two major groups of living fishes are the:
• Cartilaginous fishes (sharks and rays) with a flexible
skeleton made of cartilage
Lateral line
(c) Shark, a cartilaginous fish
Figure 17.30c
• And bony fishes with a skeleton reinforced by hard
calcium salts
– Bony fishes include:
• Ray-finned fishes
• Lungfishes
• Lobe-finned fishes
Operculum
Lateral line
(d) Bony fish
Figure 17.30d
– Cartilaginous and bony fishes have a lateral line
system that detects minor vibrations in the water.
– To provide lift off the bottom:
• Cartilaginous fish must swim but
• Bony fish have swim bladders, gas-filled sacs that make
them buoyant
Amphibians
– Amphibians:
• Exhibit a mixture of aquatic and terrestrial adaptations
• Usually need water to reproduce
• Typically undergo metamorphosis from an aquatic larva to
a terrestrial adult
• Were the first vertebrates to colonize land
• Descended from fishes that had lungs and fins with
muscles
(a) Tadpole and adult golden palm tree frog
Red-eyed tree frog
Texas barred tiger salamander
(b) Frogs and salamanders: the two major groups of amphibians
Figure 17.31
– Terrestrial vertebrates are collectively called
tetrapods, which means “four feet.”
– Tetrapods include:
• Amphibians
• Reptiles
• Mammals
Reptiles
– Reptiles (including birds) and mammals are
amniotes, which produce amniotic eggs that consist
of a fluid-filled shell inside of which the embryo
develops.
– Reptile adaptations to living on land include:
• Amniotic eggs
• Scaled, waterproof skin
– Reptiles include:
•
•
•
•
•
•
Snakes
Lizards
Turtles
Crocodiles
Alligators
Birds
Snake
Lizard
Turtle
Figure 17.33
Birds
– Recent genetic evidence shows that birds evolved
from a lineage of small, two-legged dinosaurs.
– Birds have many adaptations that make them lighter
in flight:
• Honeycombed bones
• One instead of two ovaries
• A beak instead of teeth
– Unlike other reptiles, birds are endotherms,
maintaining a warmer and steady body temperature.
Mammals
– The first true mammals:
• Arose about 200 million years ago
• Were probably small, nocturnal insect-eaters
– Most mammals are terrestrial although dolphins,
porpoises, and whales are totally aquatic.
– Mammalian hallmarks are:
• Hair
• Mammary glands that produce milk, which nourishes the
young
– There are three major groups of mammals:
• Monotremes, egg-laying mammals
Monotremes
(hatched from eggs)
Echidna adult and egg
Figure 17.35a
• Marsupials, pouched mammals with a placenta
Marsupials
(embryonic at birth)
Kangaroo newborn and mother
Figure 17.35b
• And eutherians, placental mammals
Eutherians
(fully developed at birth)
Wildebeest newborn and mother
Figure 17.35c
– Primates are distinguished by characteristics that
were shaped by the demands of living in trees. These
characteristics include:
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•
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Limber shoulder joints
Eyes in front of the face
Excellent eye-hand coordination
Extensive parental care
– Hominoids, the ape relatives of humans
Ring-tailed
lemur
Tarsier
Black spider monkey
(New World monkey)
Patas monkey (Old World monkey)
Gorilla (ape)
Orangutan (ape)
Gibbon (ape)
Chimpanzee (ape)
Human
Figure 17.37
– Upright posture and an enlarged brain appeared at
separate times during human evolution.
– Different human features evolved at different rates.
Australopithecus and the Antiquity of
Bipedalism
– Before there was the genus Homo, several hominid
species of the genus Australopithecus walked the African
savanna.
– Fossil evidence pushes bipedalism in A. afarensis back to
at least 4 million years ago.
(a) Australopithecus
afarensis skeleton
(b) Ancient footprints
(c) Model of an
Australopithecus
afarensis male
Figure 17.39
Homo Habilis and the Evolution of
Inventive Minds
– Homo habilis, “handy-man”:
• Had a larger brain, intermediate in size between
Australopithecus and modern humans
• Walked upright
• Made stone tools that enhanced hunting, gathering, and
scavenging on the African savanna
Homo Erectus and the Global Dispersal of
Humanity
– Homo erectus was the first species to extend
humanity’s range from Africa to other continents.
– The global dispersal began about 1.8 million years
ago.
– Homo erectus:
• Was taller than H. habilis
• Had a larger brain
• Gave rise to Neanderthals
© 2010 Pearson Education, Inc.
The Origin and Dispersal of Homo
Sapiens
– The oldest known fossils of our own species, Homo
sapiens:
• Were discovered in Ethiopia
• Date from 160,000 to 195,000 years ago
• DNA studies strongly suggest that all living humans can
trace their ancestry back to a single African Homo
sapiens woman who lived 160,000 to 200,000 years
ago.