Animal Evolution – The Chordates

Chapter 26 Part 2

26.10 Birds —The Feathered Ones

 Birds are the only animals with feathers • Descendants of flying dinosaurs in which scales became modified as feathers • • Long feathers are adapted for flight Downy feathers provide insulation

Dinosaurs and Feathers

Fig. 26-20a, p. 446

Fig. 26-20b, p. 446

Fig. 26-20c, p. 446

Fig. 26-20d, p. 446

Bird Adaptations

 Bird characteristics • • • • Eggs No teeth Produce body heat (

endotherms

) Lightweight skeleton, strong muscles, and efficient circulation and respiration for flight • Wings with flight feathers

A Bird Egg

yolk sac embryo amnion chorion allantois hardened shell albumin (“egg white”) Fig. 26-21, p. 446

Animation: Amniote egg

Adaptations for Flight

Fig. 26-22a, p. 447

Fig. 26-22b, p. 447

Fig. 26-22c, p. 447

skull radius ulna humerus pectoral girdle internal structure of bird limb bones pelvic girdle sternum (breastbone) two main flight muscles attached to keel of sternum Fig. 26-22c, p. 447

Animation: Avian bone and muscle structure

26.11 The Rise of Mammals



Mammals

are animals that nourish young with milk and have hair or fur; four kinds of teeth allow them to eat many kinds of food

Fig. 26-23a, p. 448

Fig. 26-23b, p. 448

incisors molars premolars canines Fig. 26-23b, p. 448

Mammalian Evolution



Monotremes

(egg-laying mammals) and

marsupials

the Jurassic (pouched mammals) evolved during 

Placental mammals

(mammals with a

placenta

that exchanges materials between the mother and embryo inside the body) evolved later

Distribution of Mammalian Lineages

 Mammals underwent adaptive radiation after dinosaurs died out  Continental movements influenced distribution  Some mammals show morphological convergence

Distribution of Mammalian Lineages

southern land mass Pangea A About 150 million years ago, during the Jurassic, the first monotremes and marsupials evolved and migrated through the supercontinent Pangea.

B Between 130 and 85 million years ago, during the Cretaceous, placental mammals arose and began to spread. Monotremes and marsupials that lived on the southern land mass evolved in isolation from placental mammals.

C Starting about 65 million ago, mammals expanded in range and diversity. Marsupials and early placental mammals displaced monotremes in South America.

D About 5 million years ago, in the Pliocene, advanced placental mammals invaded South America. They drove most marsupials and the early placental species to extinction.

Fig. 26-24, p. 448

Paleocene Mammals

The Largest Land Mammal

 Giraffe rhinoceros (

Indricotherium

) lived in Asia during the Oligocene

Convergent Evolution

26.7-26.11 Key Concepts

The Amniotes



Amniotes —reptiles, birds, and mammals—have waterproof skin and eggs, highly efficient kidneys, and other traits that adapt them to a life that is typically lived entirely on land



Reptiles and birds belong to one amniote lineage, and mammals to another

26.12 Modern Mammalian Diversity

 Egg-laying monotremes lay leathery eggs • Spiny anteaters, platypus  Pouched marsupials develop in a pouch • Kangaroos, koala, opossum, Tasmanian devil  Placental mammals include most living mammals • Rodents and bats are the most diverse groups

Monotremes: Platypus

Marsupials

Placental Mammals: The Placenta

embryo placenta uterus Fig. 26-30a, p. 451

Placental Mammals

26.13 From Early Primates to Hominids



Primates

: Mammalian subgroup including humans, apes, monkeys, and prosimians 

Anthropoids

: Humans, apes, and monkeys 

Hominids

: Humans and apes

Primate Classification

Primates

Adaptations for Walking

 Monkey, gorilla, and human

Overview of Key Trends

 Five trends led to uniquely human traits • • • • Enhanced daytime vision (binocular vision) Upright (

bipedal

) walking Better grips (power grip and precision grip) Modified jaws and teeth (omnivorous diet) • Brain, behavior, and

culture

(transmission of learned behavior between individuals and generations)

Adaptations for Walking

 Location of the foramen magnum in four-legged and upright walkers

a Hole at back of skull; the backbone is habitually parallel with ground or a plant stem b Hole close to center of base of skull; the backbone is habitually perpendicular to ground Fig. 26-32, p. 453

Better Grips

 Power grip (prehensile movement) and precision grip (opposable movement)

Origins and Early Divergences

 65 mya: First primates (shrewlike)  36 mya: Tree dwelling anthropoids  23-18 mya: First hominoids (early apes)  6 mya: Hominids

Early Primates

Fig. 26-33a, p. 453

Fig. 26-33 (b-d), p. 453

26.14 Emergence of Early Humans

 6-8 mya: Early hominids from Africa

a b c d e

Sahelanthropus

tchadensis 6 million years ago

Australopithecus africanus

3.2

–2.3 million years ago

Paranthropus

boisei 2.3

–1.2 million years ago

Homo habilis

1.9

–1.6 million years ago

Homo erectus

1.9 million to 53,000 years ago Fig. 26-34, p. 454

Australopiths

 The first bipedal hominids (

Australopithacus

) were probably human ancestors

Early Humans



Humans

are members of the genus

Homo

•

Homo habilis

emerged during the late Miocene

Early Humans

 In Africa 1.8 mya,

Homo erectus

had a larger brain, used simple stone tools and built fires

26.12-26.14 Key Concepts

Early Humans and Their Ancestors



Changes in climate and available resources were selective forces that shaped the anatomy and behavior of early humans and their primate ancestors



Behavioral and cultural flexibility helped humans disperse from Africa throughout the world

26.15 Emergence of Modern Humans



H. erectus

evolved in Africa and spread throughout the world 

H. neanderthalensis, H. floresiensis,

and modern

H. sapiens

evolved from

H. erectus

Two Models for the Origin of H. sapiens



Multiregional model

•

H. erectus

in Africa and other regions evolved slowly into

H. sapiens

(based on fossil record) 

Replacement model

•

H. sapiens

arose from a single African population of

H. erectus

and drove all other populations to extinction (based on genetics)

Two Models for the Origin of H. sapiens

H. erectus H. erectus

Time

H. sapiens

Africa Asia Europe

H. sapiens

Africa Asia Europe Fig. 26-39, p. 456

Leaving Home

 Starting 120,000 years ago, long-term shifts in global climate drove humans from Africa into the Middle East, Africa, Australia and Eurasia  15,000 years ago, humans crossed a land bridge from Siberia to North America

Dispersal Routes of H. sapiens

Origins and Extinctions of Hominid Genera

Homo rudolfensis Australopithecus anamensis Australopithecus africanus Homo habilis Australopithecus afarensis Australopithecus garhi

4

Homo erectus Paranthropus aethiopicus Paranthropus robustus

3 2 Time (millions of years ago)

Paranthropus boisei

1

Homo floresiensis Homo sapiens Homo neanderthalensis

present Fig. 26-41, p. 458

Animation: Feather development

Animation: Fossils of australopiths

Animation: Genetic distance between human groups

Animation: Homo skulls

Animation: Mammalian dentition

Animation: Mammalian radiations

Animation: Primate evolutionary tree

Animation: Primate skeletons

Animation: Skulls of extinct primates

Animation: Structure of the placenta

ABC video: Frogs Galore

ABC video: Ancient Human Skull

ABC video: Dinosaur Discovery

ABC video: Cahuachi Excavation

Video: Interpreting and misinterpreting the past

Video: Bald eagles

Video: Elephant seals

Video: Frog swimming

Video: Gopher

Video: Grizzly bears

Video: Grizzly feeding

Video: Loggerhead turtle

Video: Bittern at nest

Video: Puffin in flight

Video: Salamander

Video: Sea lions

Video: Spotted owl in old-growth forest

Video: Sting rays

Video: Tadpoles

Video: Humpback whales

Video: Salamander gills