Evolution of Life on Earth

Chapter 11-12

How old is the Earth?

• About 4.5 billion years old• Time scale is divided into:

–Eons•Eras

–Periods•Epochs

Fossil Evidence of Life

• Oldest fossils found in the lowest rock layers

• How do you find the real age of a fossil?

• Carbon-dating using half-life (you’ll learn more about this in Chemistry)

Life on Earth

• Precambrian Era- Before 600 million years ago

• Limited life on earth–Evidence of bacteria

The First Prokaryotes

• Prokaryotes were Earth’s sole inhabitants– From 3.5 to about 2 billion years

ago– As prokaryotes evolved, they

exploited and changed young Earth

• The oldest known fossils are stromatolites– Rocklike structures composed of many

layers of bacteria and sediment– Date back 3.5 billion years ago

Lynn Margulis (top right), of the University of Massachussetts, and Kenneth Nealson, of the University of Southern California, are shown collecting bacterial mats in a Baja California lagoon. Themats are produced by colonies of bacteria that live in environments inhospitable to most other life. A section through a mat (inset) shows layers of sediment that adhere to the sticky bacteria asthe bacteria migrate upward.

Some bacterial mats form rocklike structures called stromatolites,such as these in Shark Bay, Western Australia. The Shark Baystromatolites began forming about 3,000 years ago. The insetshows a section through a fossilized stromatolite that is about3.5 billion years old.

(a)

(b)

Figure 26.11a, b

The origin of eukaryotes

• Symbiotic relationships –Large cell engulfs cyanobacteria

(chloroplast?)–Large cell engulfs aerobic bacteria (pre-

mitochondria?)• Small cell becomes dependent on genetic

material present• Animal cell may have evolved from a plant

cell that lost its chloroplast

• The prokaryotic ancestors of mitochondria and plastids– Probably gained entry

to the host cell as undigested prey or internal parasites

Figure 26.13

CytoplasmDNA

Plasmamembrane

Ancestralprokaryote

Infolding ofplasma membrane

Endoplasmicreticulum

Nuclear envelope

Nucleus

Engulfingof aerobic

heterotrophicprokaryote

Cell with nucleusand endomembranesystem

Mitochondrion

Ancestralheterotrophiceukaryote Plastid

Mitochondrion

Engulfing ofphotosyntheticprokaryote insome cells

Ancestral Photosyntheticeukaryote

Cambrian Period

• Began 590 MYA (Million Years Ago)• Huge increase in the number and

diversity of living things

From Water to Land

• In order of appearance:• Plants• Fungi• Arthropods• Amphibians

Where did the rest of us come from?

Amphibians

Reptiles

BirdsMammals

Extinctions

• Permian extinction–250 MYA: 90% of ocean species and

many land insects• Cretaceous extinction

–65 MYA: Majority of dinosaurs, sea and land species

• Why???

Monkey Business!

• What do you know about primates? Write down each type of primate that you can think of. See how many you can get!

Mammals

• First appeared 220 MYA• Evolved from small, active, meat-

eating reptiles• What are the characteristics of

mammals?

Primates

• 65 MYA• A group of mammals that include all

monkeys, apes, and humans• 2 groups:

–Prosimians–Anthropoids

Prosimian

• Pre-monkey• Small, monkey-like primate• Large, forward-facing eyes

Anthropoid

• “Humanlike”• Monkeys, apes, humans

Characteristics of Primates

• Make a fist: opposable thumb • Sensitive finger tips and protective nails• Arms move freely in shoulder joint• Binocular vision: use both eyes at once with

overlapping fields• Relatively large brains• Some species make and use simple tools• Complex social behaviors and family

relationships

ADAPTATION OF THE PRIMATE (& HUMAN) HAND

Living things have bodies that are adapted for the places they live and the things they do.

• Fish have gills to obtain oxygen from water• Birds have hollow spongy bones so that they will be

light enough to fly. • Arctic animals have layers of fat and thick coats of

fur to keep warm in the frigid Arctic climate. Primates, too, are adapted for the things they do.

One of our adaptations is our hand. Humans, as well as monkeys, gorillas, and other primates, have a hand that can grasp objects.

Adaptation of the Human Hand

YOUR TASKDo each of the following activities and have

your partner time how long it takes you to do each one. Record the times in a data sheet.

A. Tie a knot in a piece of string. B. Remove one shoe and replace it on your foot. C. Unbutton two buttons and button them again. D. Open a door. E. Write your name on a piece of paper.

NEXT, firmly tape or band your thumb to the palm of your hand and complete the same activities again, timing how long it takes you this time. Enter the times in your data table.

Time to perform various actions:

ACTION Time (in seconds) to perform the action with THUMBS FREE

THUMBS TAPED

Tie knot in string Remove and replace shoe Unbutton and rebutton Write name

Open door

1. Describe how your hand is adapted for doing the actions you tested.

  2. You have an opposable thumb. Explain

what you think this means.

3. Why do you feel that human hand adaptations have helped to make humans such a successful species on earth? (List and explain at least 2 reasons.)

Hominids

• Anthropoids that evolved to become the human family

• 5-8 MYA• Many different species existed at once• Today, only Homo sapiens

Lucy, a famous fossil

• Discovered in 1974• Small female hominid skeleton• 3-4 MYA, dubbed by some as the

“Missing Link”• Australopithecus afarensis

Homo habilis

• “Handy Man”• Discovered in 1964• Used and made tools• 2.4 - 1.6 MYA• Direct ancestor to Homo sapiens

Homo erectus

• “Upright Man”• Migrated out of Africa into Asia and

Europe• Taller with a larger brain• Built fires, wore animal skin clothing,

lived in caves, made stone tools• 1.8 MYA

Neandertals

• 300,000 – 200,000 years ago• 1856, fossils found in Neander Valley,

Germany• Europe, Asia, Middle East• Cold-weather adapted• Social structure, tools, buried dead,

hunted

Cro-Magnon

• Appeared 40,000 years ago• H. sapiens archaic• Taller and lighter than Neandertals,

like modern humans• Complex tools, culture, well-designed

dwellings, language, art, trade• Tools from bone, antler, wood, stone,

ivory

Us!

• Homo sapiens sapiens• Appeared 100,000 years ago• “Out of Africa”

–Supported by fossil and DNA evidence

Now/Homework

• Read pp. 280-294–P.284 #1-3–P.289 #1-4–P.294 #1-3