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Chapter 26: Animals – The Vertebrates
Characteristics of Chordates
 Bilateral
 Some species are invertebrates but the vast majority are vertebrates
 Vertebrates – chordates with a backbone and a brain located inside a
protective chamber
 Chordate – an animal that exhibit the following 4 main features. In many
cases these features are temporary, appearing only during embryonic
development
 4 Features Evident in Chordate Embryos
1. Notochord – a long rod of stiffened tissue (not cartilage or bone), helps
support the body
2. Nerve Cord – nervous system develops from this tubular structure.
Anterior end increases in mass and forms brain
3. Pharynx – for feeding and/or respiration. Has distinctive slits in the wall
4. A tail forms in embryos and extends past the anus
Chordate Classification
 3 Subphyla of Chordates
1. Urochordata – tunicates
2. Cephalochordata – lancelets
3. Vertebrata
 8 Classes of Vertebrates
1. Agnatha – jawless fish
2. Placodermi – jawed, armored fish (extinct)
3. Chondrichthyes – cartilaginous fish
4. Osteichthyes – bony fish
5. Amphibian – amphibians
6. Reptilia – reptiles
7. Aves – birds
8. Mammalia – mammals
Invertebrate Chordates
 Tunicates
 Sea squirts
 In marine habitats
 Most adults remain attached to rocks
 Filter feeders – water flows in siphon and passes through gill slits, and out
another siphon
 Once sea squirt reaches adult stage its tail and notochord disappear
 A very simplified nervous system
 Lancelets
 Live in nearshore marine sediments around the world
 Most of time buried in sand
 Lancelet refers to the sharp tapering of their body
 Have a closed circulatory system, but no red blood cells
 Filter feeders
 No brain
Existing Jawless Fishes (Ostracoderms)





Ex. Hagfish and lampreys
75 species
Cylindrical body and a skeleton of cartilage
Hagfish prey on worms or scavenge
Lampreys are parasitic and have a sucker like oral disk
Existing Jawed Fishes (Placoderms)
 Vertebrate fish outnumber all other vertebrates
 Swim Bladder – an adjustable flotation device that exchanges gases with
blood
 Scales – small bony plates at the body surface that protect body without
weighing it down
 Cartilaginous Fishes (Chondrichthyes)
 Skates, sharks, rays
 Predators
 Prominent fins
 Skeleton of cartilage
 5-7 gill slits
 Scales are small
 Bony Fishes (Osteichthyes)
 Most numerous and diverse vertebrates
 Body plans very greatly
 3 lineages
1. Ray-finned fishes
2. Lobe-finned (1 species remains today)
3. Lungfish (3 species remain today)
Origin of Amphibians
 Lobed finned fish probably pulled themselves up out of dried up ponds to
ones that still had water. They gulped air and had lungs
 Amphibian – a vertebrate with a body plan and reproductive mode
somewhere between fishes and reptiles
 Most have largely bony endoskeleton
 Four legs
 Salamanders, frogs, toads, have not escaped water entirely
 Even with lungs or gills, they can use their thin skin as a respiratory surface
 Respiratory surfaces must be kept moist
Salamanders
 Newts
 Like fishes and early amphibians salamanders bend from side to side when
they walk
 Carnivores
Toads and Frogs
 Long hindlimbs and powerful muscles allow them to catapult through the air
or water
 Sticky-tipped tongue for catching prey
 Frogs have mucus and poison glands. Poison types have bright coloration
The Rise of Reptiles






A divergence from the amphibian lineage gave rise to reptiles
First to escape dependency on standing water
Have tough dry scaly skin that restricts loss of water
Fertilization is internal. Sperm do not require free water to reach eggs
Kidneys are good at conserving water
Amniote Egg – egg that has an extra embryonic membranes and often a
shell. Embryo develop to an advanced stage before hatching
 Early reptiles chased prey with far greater cunning and speed
 Limbs were more efficient at supporting the trunk of the body on land
 Nervous system increased in complexity
 Crocodilians were the first animals with a muscular four-chambered heart fully
separated into 2 halves
 Reptiles depend on lungs not skin for gas exchange
Crocodilians




Closest relatives of birds and dinosaurs
Live in or near water
Adjust body temperature with behavioral and physiological mechanisms
Like birds in social behaviors when parents guard nests and assist hatchlings
into water
Turtles
 Live inside shell that is attached to skeleton
 Have tough horny plates instead of teeth
 Lay eggs on land then leave them
Lizards and Snakes





95% of reptiles
Short-legged long-bodied lizards gave rise to the elongated limbless snake
Some snakes have bony remnants of ancestral hindlimbs
All snakes are carnivores
Snakes usually do not act aggressively toward humans
Tuataras
 Have a third “eye”. It can only register changes in daylength and light
intensity
 Engage in sex after 20 years old
 Look like a lizard
Birds (Aves)
 Feathers – lightweight structures derived from skin, are used for flight body
insulation or both
 Birds descended from tiny reptiles that ran about on 2 legs





Feathers evolved as highly modified reptilian scales
Birds have scales on legs
Lay eggs
Differ greatly in body size, proportions, coloration, and capacity for flight
Large durable 4 chambered heart
The Rise of Mammals











Mammals – vertebrates with hair and mammary glands
A few aquatic mammals – whales, dolphins, manatees, platypuses, otters
Care for young for an extended period
Adults serve as model for their behavior
Behavioral Flexibility – a capacity to expand on basic activities with novel
forms of behavior
Cerebral Cortex – outermost layer of the forebrain receives, processes and
stores information from sensory structures and it issues commands for
complex responses
Primates have most highly developed cerebral cortex
Most mammals secure, cut and sometimes chew food before swallowing
Dentition – type, number, and size of teeth differ from reptiles
Have 4 types of upper and lower teeth
1. Incisors – nip or cut food
2. Canines
3. Premolars – crush grind shear
4. Molars – crush grind shear
Teeth offer clues to life styles
Portfolio of Existing Mammals
 3 lineages of Mammals
1. Monotremes – egg laying mammals
2. Marsupials – pouched mammals
3. Eutherians – placental mammals
 Spiny anteaters and duck billed platypus are the only living monotremes
 Most marsupials are native to Australia
 Newborns finish development in a permanent pouch on the mother
 Placenta – a spongy tissue of maternal and fetal membranes. Forms inside
pregnant females uterus
 Grow faster in placenta then in marsupial pouch
Primate Classification
 Order Primates – prosimians, tarsioids, anthropoids






4.
5.
Prosimians dominated forests millions of years ago
Anthropoids – monkey, apes, humans
Apes are closer to humans than monkeys in comparing biochemistry
Hominids – humanlike and human species of a line of descent that started
with its divergence from apes
Most are arboreal or tree dwellers
5 Trends helped to define lineage leading to humans
1. Less reliance on sense of smell and more on vision
 Eyes are forward directed
 Respond to variations in color and light intensity
2. Skeletal changes led to upright walking, which freed hands
 Bipedalism – walk on two legs
3. Changes in bones and muscles led to refined hand movements
 Opposable thumb led to a precision grip (holding a pen)
Teeth became less specialized
Evolution of the brain, behavior and culture
 Parents put more effort in fewer offspring and formed stronger bonds
 Language developed
From Early Primates to Hominids
Origins and Early Divergences





Primates evolved from mammals more than 60 million years ago
First ones resembled small rodents
Stayed in trees because abundant food and safety
Climate changed so they had to move out of the trees or die
One lineage gave rise to great apes and other gave rise to the first hominids
The First Hominids




Australopiths – southern apes
Australopiths has a large face, protruding jaws, small skull and brain
Were apelike in many skeletal ways but humanlike in walking upright
Australopithecus afarensis – “Lucy” 3.2 million years old
Emergence of Early Humans
 The brain sets humans apart from apes
 Earliest humans – Homo habilis means handy human
 A great stone tool maker
 Homo erectus – means upright man
 Clearly related to modern humans
 Traveled out of Africa to Europe, Asia
 Larger brain
 More advanced tool maker
 Built fire
 Used furs for clothing
 Homo sapiens
 Means wise man
 Evolved 100,000 years ago
 Smaller teeth and jaw
 Larger brain
 Developed complex language
 Neandertals
 Lived in Europe 200,000 – 30,000 years ago
 Massively built and large brain
 Their disappearance coincided with the appearance of anatomically
modern humans in the same regions about 40,000 – 30,000 years ago.
 We have no evidence that they interbred with the later arrivals
 Neandertal DNA has unique sequences, so they might not have
contributed to the gene pools of modern European populations
 We still do not know what happened to them
 Humans spread rapidly through the world by devising cultural means to deal
with a broader range of environments.
Chapter 26: Animals – The Vertebrates
Characteristics of Chordates

 Some species are invertebrates but the vast majority are vertebrates
 Vertebrates –
 Chordate – an animal that exhibit the following 4 main features. In many
cases these features are temporary, appearing only during embryonic
development
 4 Features Evident in Chordate Embryos
1. Notochord –
2. Nerve Cord –
3. Pharynx –
4. A tail forms in embryos and extends past the anus
Chordate Classification
 3 Subphyla of Chordates
1. Urochordata –
2. Cephalochordata –
3. Vertebrata
 8 Classes of Vertebrates
1. Agnatha –
2. Placodermi –
3. Chondrichthyes –
4. Osteichthyes –
5. Amphibian –
6. Reptilia –
7. Aves –
8. Mammalia –
Invertebrate Chordates
 Tunicates


 Most adults remain attached to rocks
 Filter feeders –
 Once sea squirt reaches adult stage its tail and notochord disappear
 A very simplified _______________ system
 Lancelets
 Live in nearshore marine sediments around the world
 Most of time buried in sand
 Lancelet refers to the sharp tapering of their body
 Have a ____________ circulatory system, but no red blood cells


Existing Jawless Fishes (Ostracoderms)
 Ex.

 Cylindrical body and a skeleton of cartilage
 Hagfish prey on worms or scavenge
 Lampreys are parasitic and have a sucker like oral disk
Existing Jawed Fishes (Placoderms)
 Vertebrate fish outnumber all other vertebrates
 Swim Bladder –
 Scales –
 Cartilaginous Fishes (Chondrichthyes)






 Bony Fishes (Osteichthyes)
 Most numerous and diverse vertebrates
 Body plans very greatly
 3 lineages
1.
2.
3.
Origin of Amphibians
 Lobed finned fish probably pulled themselves up out of dried up ponds to
ones that still had water. They gulped air and had lungs
 Amphibian –
 Most have largely bony endoskeleton

 Salamanders, frogs, toads, have not escaped water entirely
 Even with lungs or gills, they can use their thin skin as a respiratory surface
 Respiratory surfaces must be kept __________
Salamanders

 Like fishes and early amphibians salamanders bend from side to side when
they walk

Toads and Frogs
 Long hindlimbs and powerful muscles allow them to catapult through the air
or water
 Sticky-tipped tongue for catching prey
 Frogs have mucus and __________ glands. Poison types have bright
coloration
The Rise of Reptiles
 A divergence from the amphibian lineage gave rise to reptiles
 First to escape dependency on standing ____________
 Have tough dry scaly skin that restricts loss of ____________
 Fertilization is ____________. Sperm do not require free water to reach eggs
 ____________ are good at conserving water
 Amniote Egg –
 Early reptiles chased prey with far greater cunning and speed
 Limbs were more efficient at supporting the trunk of the body on land

 Crocodilians were the first animals with a muscular four-chambered heart fully
separated into 2 halves
 Reptiles depend on __________ not skin for gas exchange
Crocodilians
 Closest relatives of __________ and _______________

 Adjust body temperature with behavioral and physiological mechanisms
 Like birds in social behaviors when parents guard nests and assist hatchlings
into water
Turtles
 Live inside shell that is attached to _______________
 Have tough __________ __________ instead of teeth
 Lay eggs on land then leave them
Lizards and Snakes
 _______ of reptiles
 Short-legged long-bodied lizards gave rise to the elongated limbless snake
 Some snakes have bony remnants of ancestral hindlimbs
 All snakes are _______________
 Snakes usually do not act aggressively toward humans
Tuataras
 Have a third “eye”. It can only register changes in daylength and light
intensity
 Engage in sex after _______ years old
 Look like a _______________
Birds (Aves)
 Feathers –
 Birds descended from tiny _______________ that ran about on 2 legs
 Feathers evolved as highly modified reptilian ____________
 Birds have scales on __________

 Differ greatly in body size, proportions, coloration, and capacity for flight
 Large durable _______ chambered heart
The Rise of Mammals
 Mammals –
 A few aquatic mammals –
 Care for young for an extended period
 Adults serve as model for their behavior
 Behavioral Flexibility –
 Cerebral Cortex –
 Primates have most highly developed cerebral cortex
 Most mammals secure, cut and sometimes chew food before swallowing
 Dentition –
 Have 4 types of upper and lower teeth
1.
2.
3.
4.
 Teeth offer clues to life styles
Portfolio of Existing Mammals
 3 lineages of Mammals
1. Monotremes –
2. Marsupials –
3. Eutherians –
 Spiny anteaters and duck billed platypus are the only living monotremes
 Most marsupials are native to _______________
 Newborns finish development in a permanent pouch on the mother
 Placenta –
 Grow faster in placenta then in marsupial pouch
Primate Classification
 Order Primates –
 Prosimians dominated forests millions of years ago
 Anthropoids –
 Apes are closer to humans than monkeys in comparing biochemistry
 Hominids –
 Most are arboreal or tree dwellers
 5 Trends helped to define lineage leading to humans
1. Less reliance on sense of smell and more on vision


2. Skeletal changes led to upright walking, which freed hands
 Bipedalism –
3. Changes in bones and muscles led to refined hand movements

4. Teeth became less specialized
5. Evolution of the brain, behavior and culture
 Parents put more effort in fewer offspring and formed stronger bonds

From Early Primates to Hominids
Origins and Early Divergences
 Primates evolved from _______________ more than 60 million years ago
 First ones resembled small _______________
 Stayed in __________ because abundant food and safety
 Climate changed so they had to move out of the trees or die
 One lineage gave rise to great apes and other gave rise to the first hominids
The First Hominids
 Australopiths –
 Australopiths has a large face, protruding jaws, small skull and brain
 Were apelike in many skeletal ways but humanlike in walking upright
 Australopithecus afarensis –
Emergence of Early Humans
 The brain sets humans apart from apes
 Earliest humans – Homo habilis means ___________ __________

 Homo erectus – means ____________ ____________
 Clearly related to modern humans
 Traveled out of Africa to Europe, Asia

 More advanced tool maker


 Homo sapiens
 Means
 Evolved __________ years ago


 Developed complex language
 Neandertals
 Lived in ____________ 200,000 – 30,000 years ago

 Their disappearance coincided with the appearance of anatomically
modern humans in the same regions about 40,000 – 30,000 years ago.
 We have no evidence that they interbred with the later arrivals
 Neandertal DNA has unique sequences, so they might not have
contributed to the gene pools of modern European populations
 We still do not know what happened to them
 Humans spread rapidly through the world by devising cultural means to deal
with a broader range of environments.