Chapter 6-3

Rate of Change

How Do New Species Form?

A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits that prevent reproduction.

Example-Fig 1 on p181 The squirrels are separated by the Grand Canyon. They are the species but overtime can become separate species.

What Patterns Describe the Rate of Evolution?

Two patterns describe the pace of evolution: gradualism & punctuated equilibrium.

Gradualism

Involves small changes that add up to major changes over a long period of time.

Punctuated Equilibrium

Short periods of rapid change and then don’t change much.

Primates

A group of mammals that includes humans, apes, monkeys, and prosimians

Characteristics:Opposable thumb (bends opposite index

finger)Binocular vision (eyes at front of head, 3-

D)

Our closest living relative?

Chimpanzee!

97% of our genetic material is identical

Humans did not descend from chimpsInstead, humans and chimps share a common

ancestor• Split approximately 7 mya

Hominids

Hominids include humans and human-like ancestors

Walk upright on two legs for locomotionCalled bipedalism

Prosimians

First primatesAbout 55 mya

Only 1 species, the lemur survives today

Australopithecines

“Southern Man Ape”

Long arms, short legs, small brains

Brains are larger than ape brains, but smaller than modern humans

Lucy (1979) 2 myaFootprints 3.6 myaAustralopithicus afarensis

Homo habilis

“Handy Man”

2.3 mya

Used crude stone tools

Short in size, small brain, and large jaw

Homo habilis

Homo erectus

Survived for nearly 1 million yearsLonger than any other species

Lived in caves, built fires, wore clothing, hunted large animals, made tools

Migrated across the globe

Homo sapiens?Neanderthals

230,000 years ago

Hunted large animals, made fires, wore clothing

Cared for the sick and elderly, buried the dead

Heavy brow rides, larger brain than modern humans

Homo sapiensCro-Magnon

100,000 years old

Smaller and flatter faces, high round skulls, thicker and heavier bones

Made cave paintings, sculptures, and carvings

Complex social organization and civilizations

Cave Paintings