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 chimps Instead, 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 locomotion Called bipedalism

Prosimians First primates Only 1 species, the lemur survives today About 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 mya Footprints 3.6 mya Australopithicus 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 years Longer 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 sapiens Cro-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