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Ch 12: The History of Life

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Page 1: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Ch 12: The History of Life

Page 2: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Specific environmental conditions are necessary in order for fossils to form.

12.1 The Fossil Record

Page 3: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Fossils can form in several ways.

• Permineralization occurs when minerals carried by water are deposited around a hard structure.

12.1 The Fossil Record

Page 4: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Fossils can form in several ways.

• A natural cast forms when flowing water removes all of the original tissue, leaving an impression.

12.1 The Fossil Record

Page 5: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

• Trace fossils record the activity of an organism.

Fossils can form in several ways. 12.1 The Fossil Record

Page 6: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

• Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.

12.1 The Fossil Record

Fossils can form in several ways.

Page 7: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Fossils can form in several ways.

• Preserved remains form when an entire organism becomes encased in material such as ice.

12.1 The Fossil Record

Page 8: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

• Specific conditions are needed for fossilization.• Only a tiny percentage of living things became fossils.

12.1 The Fossil Record

Page 9: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Radiometric dating provides an accurate way to estimate the age of fossils.

• Relative dating estimates the time during which an organism lived.

– It compares the placementof fossils in layers of rock.

– Scientists infer the order inwhich species existed.

12.1 The Fossil Record

Page 10: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

– A half-life is the amount of time it takes for half of the isotope to decay.

• Radiometric dating uses decay of unstable isotopes.

– Isotopes are atoms of an element that differ in their number of neutrons.

12.1 The Fossil Record

Page 11: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

The geologic time scale divides Earth’s history based on major past

events.

Page 12: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Geologic Time Scale• Is a representation of the history

of the Earth• Organizes Earth’s history by major

changes or events that have occurred, using evidence from the fossil and geologic records.

Page 13: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Organization of the Geologic Time Scale

Divided into a series of units based on the order in

which different groups of rocks and fossils were

formed.

Page 14: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

3 basic units:

1. Eras- – last tens to hundreds of millions of years– consist of two or more periods– three eras: Cenozoic, Mesozoic, Paleozoic

2. Periods-– most commonly used units of time on the scale– lasting tens of millions of years– Each period is associated with a particular type of rock

system.

3. Epochs-– smallest units of geologic time– last several million years

Page 15: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Multicellular life evolved in

distinct phases.

Page 16: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Paleozoic Era• Multicellular organisms first appeared during

the Paleozoic era.• The era began 544 million years ago and

ended 248 million years ago.• The Cambrian explosion led to a huge diversity

of animal species.

Page 17: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Mesozoic era• known as the Age of Reptiles.• It began 248 million years ago and ended 65

million years ago.• Dinosaurs, birds, flowering plants, and first

mammals appeared during this time.

Page 18: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Cenozoic era• First appearance of mammals• The Cenozoic era began 65 million years ago

and continues today.• Placental mammals and monotremes (lay

eggs) evolved and diversified.• Anatomically modern humans appeared

late in the era.

Page 19: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Humans appeared late in Earth’s

history.

Page 20: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Primates• Primates are mammals with flexible hands and

feet, forward-looking eyes and enlarged brains.

• Also have arms that can rotate in a circle around their shoulder joint, as well as thumbs that can move against their fingers.

• Include:– Lemurs, monkeys, apes and humans

• Primates share physical traits and molecular similarities.

Page 21: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Primates

Page 22: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Evolutionary Relationships of Primates

• Primates are divided into 2 groups:– Anthropoids– Prosimians

• Anthropoids are divided into:– Hominoids– Monkeys

• Hominoids are divided into:– Lesser apes (gibbons)– Great apes (orangutans, chimpanzees, and gorillas)– Hominids (include humans)

Page 23: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record
Page 24: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Hominid Species• Classified into 2 groups:

– genus Australopithecus– genus Homo

• Australopithecus afarensis– Lived 3-4 million yrs ago in Africa– Smaller brain, humanlike limbs

• Homo habilis– Lived 2.4-1.5 million yrs ago in modern day Kenya and

Tanzania– Earliest known hominid to make stone tools– Brain was larger and shape was more similar to that of

a modern human

Page 25: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Hominid Species• Homo neanderthalensis

– Lived 200,000 to 300,000 yrs ago in Europe and Middle East

• Homo sapiens– Includes modern humans– First appeared in Ethiopia around 100,000 yrs ago

( according to fossils found there)– Different features from modern humans

• Proof that the species did not stop evolving

Page 26: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Examples of Hominid Skulls

Australopithecusafarensis

Homo habilis Homo neanderthalensis

Homo sapiens

Page 27: Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record

Assignment Draw the Geologic Time Scale (pg 367)

• You will need a few sheets of paper and markers/colored pencils, maybe a ruler.

• Please include the following on your time scale:– All eras and periods– The years for each– Brief description of what happened on Earth during

that time, animals, extinctions, etc.– PICTURES!!!

• BE CREATIVE!!! You HAVE to use color and pictures!!!! NO EXCEPTIONS!!!!!!