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

Fig. 26-21, p. 446

yolk sac embryo amnion chorion allantois

hardened shell albumin (“egg white”)

Animation: Amniote egg

Adaptations for Flight

Fig. 26-22a, p. 447

Fig. 26-22b, p. 447

Fig. 26-22c, p. 447

Fig. 26-22c, p. 447

skull

radius

pectoral girdle

internal structure of bird limb bones

ulna

humerus

pelvic girdle

sternum (breastbone)

two main flight muscles attached to keel of sternum

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

Fig. 26-23b, p. 448

incisors

molars premolars canines

Mammalian Evolution

Monotremes (egg-laying mammals) and marsupials (pouched mammals) evolved during the Jurassic

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

Fig. 26-24, p. 448

Pangea

southern land mass

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.

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

Fig. 26-30a, p. 451

placenta

uterus

embryo

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

Fig. 26-32, p. 453

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

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

Fig. 26-34, p. 454

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

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

Fig. 26-39, p. 456

H. erectus H. sapiens

Africa

Asia

Europe

H. erectus H. sapiensAfrica

Asia

Europe

Time

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

Fig. 26-41, p. 458

Homo floresiensisHomo rudolfensis

Homo habilis Homo sapiens

Australopithecus anamensis Australopithecus

africanusHomo erectus

Australopithecus afarensis Australopithecus garhi

Homo neanderthalensis

Paranthropus robustusParanthropus aethiopicus

Paranthropus boisei

4 3 2 1 present

Time (millions of years ago)

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