chapter 19

The 4 major derived character of this clade is an amniotic egg with four internal membranes.

1. The amnion is a fluid-filled sac surrounding the embryo. 2. The yolk sac contains a rich store of nutrients for the developing embryo. 3. The allantois also helps dispose of metabolic waste. 4. The chorion (and allantois) enable the embryo to obtain oxygen from the air and dispose of carbon dioxide.

Three lineages of jawed fishes with gills and paired fins are commonly called fishes

1. chondrichthyans—sharks and rays, 2. ray-finned fishes—tuna, trout, and goldfish, and 3. lobe-finned fishes—coelacanths and lungfishes.

Lobe-fins have muscular pelvic and pectoral fins that are supported by rod-shaped bones.Today, three lineages of lobe-fins survive:

1. coelacanths, living deep in the oceans, were once thought to be extinct, 2. lungfishes, which can gulp air into lungs, inhabit stagnant waters in the Southern Hemisphere, and 3. tetrapods, adapted to life on land, include terrestrial vertebrates.

A phylogenetic tree shows that all primates are divided into three groups:

1. lemurs, lorises, and pottos, 2. tarsiers, 3. anthropoids, including monkeys and apes with a fully opposable thumb, in which the tip of all four fingers can touch the thumb.

note 4

Analysis of mtDNA and Y chromosomes suggests that all living humans inherited their mtDNA from a woman who lived 160,000-200,000 years ago and diverged from a common African ancestor.

larger brain marked the evolution

Australopiths had such small brains (400-450 cc) that they were too small to be members of Homo.
Homo habilis (2.4-1.6 million years ago) had a brain size of 510-690 cc. Their fossils are found with stone tools.
Homo ergaster (1.9-1.6 million years ago) had a brain size ranging from 750 to 850 cc. Their - fossils are found with more sophisticated stone tools and - long, slender legs were adapted for long-distance walking.
Homo sapiens has a brain size of around 1,300 cc.

evolution connection

During the late Devonian, a line of lobe-finned fishes gave rise to tetrapods, jawed vertebrates with limbs and feet that can support weight on land.Adapting to life on land was a key event in vertebrate history.All subsequent groups are descendants of these early land-dwellers.

birds are feathered reptiles

Flight is very costly, and present-day birds have a high rate of metabolism. Unlike other living reptiles, birds are endothermic,using heat generated by metabolism to maintain a warm, steady body temperature.Birds have relatively large brains and display complex behaviors. They have acute senses,fine muscle control, and excellent eyesight.

who were the hobbits

Fossils of small hominins named Homo floresiensis that were found in Indonesia are controversial. The 2004 discovery of the nearly complete skeleton was of a hominin that was about 1 meter tall,had a chimp-sized brain, and had a skull that displayed some humanlike traits. Scientists are trying to determine their relationship to other hominins.

note

Gorillas, chimpanzees, and humans have a high degree of social organization

what are hagfish

Hagfishes are deep-sea scavengers that produce slime as an antipredator defense.

note 6

Human skin color varies geographically, likely as a result of natural selection. Natural selection may have selected for the competing abilities of skin to block UV radiation, which degrades folate, and absorb UV radiation to synthesize vitamin D. Folate is vital for fetal development and spermatogenesis.Vitamin D is essential for proper bone development.

what are lampreys

Lamprey adults are parasites that penetrate the sides of fishes with their rasping tongues.
Larval lampreys resemble lancelets and are suspension feeders that live in freshwater streams,where they feed, buried in sediment.

Birds are feathered reptiles with adaptations for flight

Most birds can fly, and nearly every part of their bodies reflects adaptations that enhance flight. - The forelimbs have been remodeled as feather-covered wings that act as airfoils.Large flight muscles anchored to a central ridge along the breastbone provide power.Many features help reduce weight for flight:present-day birds lack teeth.he tail is supported by only a few small vertebrae.Feathers have hollow shafts. Their bones have a honeycombed structure that makes them strong but light.

Monkeys do not constitute a monophyletic group

Old World monkeys (Africa and Asia)probably evolved first,lack a prehensile tail, and - have nostrils that open downward. New World monkeys have a prehensile tail and - nostrils that are wide open and farther apart. In addition to monkeys, the anthropoid group includes apes: gibbons, orangutans, gorillas, chimpanzees (and bonobos), and humans.

note 5

Our species emerged from Africa in one or more waves, migrating to Asia 50,000-60,000 years ago and then to Europe, Southeast Asia, and Australia.The capacity for creativity and symbolic thought may have spurred human evolution.

HOMININ EVOLUTION

Paleoanthropology is the study of human origins and evolution, the brief history since the divergence of human and chimpanzee lineages.
Paleoanthropologists have unearthed about 20 species of extinct hominins, species that are more closely related to humans than to chimpanzees, and thousands of hominin fossils.

what are Repties

Reptiles (including birds) and mammals are amniotes.

mammal info

The first true mammals arose 200 million years ago and were probably small, nocturnal insectivores. Monotremes are the oldest lineage of mammals.Marsupials diverged from eutherians (placental mammals)about 180 million years ago. Mammals underwent an adaptive radiation following the Cretaceous extinction of dinosaurs, giving rise to large terrestrial carnivores and herbivores, bats, and aquatic whales and porpoises.

primate diversity

The mammalian order Primates includes the lemurs, tarsiers, monkeys, and apes. - Primates probably arose as small arboreal mammals before 65 million years ago, when dinosaurs still dominated the planet.
Many primate characters are arboreal adaptations. - Shoulder and hip joints allow climbing and brachiation. - Grasping hands and feet are highly mobile and flexible. - Sensitive hands and feet aid in manipulation. - A short snout and forward-pointing eyes enhance depth perception.

note 2

The oldest hominin yet discovered, Sahelanthropus tchadensis, lived about 7 to 6 million years ago.
The fossil record suggests that hominin diversity increased dramatically between 4 and 2 million years ago.

note 7

Thousands of new species of organisms are discovered each year. The pace of discovery has recently increased due to better access to remote areas and new mapping technologies.

note 3

Unlike chimpanzees, humans walk upright and - have larger brains. Bipedalism arose millions of years before larger brain size. Evidence of bipedalism includes 3.6-million-year-old upright-walking hominin footprints and fossil skeletons.

Chondrichthyans have

a flexible skeleton made of cartilage, electrosensors on their heads, and a lateral line system that helps them locate prey.Most sharks are fast-swimming predators, with sharp vision and a keen sense of smell.Most rays are adapted for life on the bottom, with dorsoventrally flattened bodies and eyes on the top of their heads.

Ray-finned fishes have

an internal skeleton reinforced with a hard matrix of calcium phosphate,flattened scales covered with mucus,an operculum that covers a chamber of gills, and a buoyant swim bladder (derived from an ancestral lung). With more than 27,000 species, ray-finned fishes are the most diverse group of vertebrates.

jawed vertebrates

appeared in the fossil record about 470 million years ago and quickly diversified using their paired fins and tail to chase a wide variety of prey.Jaws may have evolved by modifications of skeletal supports of the anterior pharyngeal (gill) slits.The remaining gill slits remained as sites of gas exchange.

Hagfishes and lampreys

are craniates,have a notochord, but lack hinged jaws and paired fins.

Monotremes

are egg-laying mammals. Living monotremes include the duck-billed platypus and - echidnas.Unlike monotremes, the embryos of marsupials and eutherians are nurtured by a placenta, in which nutrients from the mother's blood diffuse into the embryo's blood.

mammals

are endothermic amniotes with hair, which insulates their bodies, and mammary glands, which produce milk.Mammals have efficient respiratory and circulatory systems that support their high rate of metabolism.Mammalian teeth are differentiated for many kinds of diets.

Eutherians

are mammals that bear fully developed live young. They are commonly called placental mammals because their placentas are more complex than those of marsupials

gibbons

are monogamous and the only fully arboreal apes

orangutans

are shy, solitary, and live in rain-forest trees and the forest floor.

gorillas

are the largest of the apes and fully terrestrial.

birds

evolved from a lineage of small, two-legged dinosaurs called theropods. - Archaeopteryx is the oldest, most primitive known bird (150 million years old), with feathered wings.It resembled a small bipedal dinosaur, with teeth, wing claws, and a long tail with many vertebrae.

Like plants, vertebrates faced obstacles on land inregard to

gas exchange, water conservation,structural support,a means of locomotion,adapting sensory organs that worked well in water but not on land, and reproduction

homo erectus

had a brain volume of around 940 cc and - was the first hominin to leave Africa.
The oldest known fossils of hominins outside of Africa are about 1.8 million years old.

Marsupials

have a brief gestation and give birth to tiny, embryonic offspring that complete development while attached to the mother's nipples.

reptiles

include lizards, snakes, turtles, crocodilians, birds, and extinct dinosaurs,have a skin covered with scales and waterproofed with keratin,obtain most of their oxygen using lungs, and are ectothermic, absorbing external heat rather than generating much of their own.

Amphibians

include salamanders, frogs, and caecilians, - use their moist skins to supplement their lungs for gas exchange,often have poison glands in their skins,usually return to standing water to reproduce,undergo metamorphosis from a larval stage to the adult form, andwere the first tetrapods able to move on land.

apes

lack a tail and have relatively long arms and short legs, have relatively larger brains with respect to size, and more flexible behavior.

Lampreys but not hagfishes have rudimentary vertebral structures. Thus,

lampreys are vertebrates but hagfishes are not vertebrates.

nonhuman apes

live only in Africa and Southeast Asia, in tropical rain forests and have a smaller geographic range than monkeys.

Homo neanderthalensis, commonly called Neanderthals

lived in Europe from about 350,000 to 28,000 years ago when they went extinct, had brains as large as modern humans, and hunted big game with tools made of stone and wood

chipanzees

make and use tools.
Humans and chimpanzees are closely related, share 99% of their genes, and diverged from a common ancestor between 5 and 7 million years ago.

how Neanderthal relate to regular humans

An analysis of mtDNA isolated from Neanderthal bones suggests that they were a distinct species from modern humans.The last common ancestor between humans and Neanderthals lived about 500,000 years ago.