1. 64R: Ch 12 The History of Life 12.1 The Fossil Record
How Fossils Form:
Permineralization: minerals carried by water are deposited around a hard structure.
Natural cast forms: flowing water removes all of the original tissue, leaving an impression.
Amber-preserved fossils: organisms that become trapped in tree resin that hardens after the tree is buried.
Preserved remains form when an entire organism becomes encased in material such as ice.
Only a tiny percentage of living things became fossils!!

2. Relative dating estimates the time during which an organism lived.
Radiometric Dating:
Relative dating estimates the time during which an organism lived.
It compares the placement of fossils in layers of rock.
Radiometric dating uses decay of unstable isotopes.
Isotopes are atoms of an element that differ in their number of neutrons

3. Half-Lives

4. 12.2 The Geologic Time Scale
Index fossils can provide the relative age of a rock layer.
existed only during specific spans of time
occurred in large geographic areas
Index fossils include fusulinids and trilobites.
The history of Earth is represented in the geologic time scale.

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

8. Periods last tens of millions of years.
most commonly used units of time on time scale
associated with rock systems.
Epochs last several million years.

10. 12.3 Origin of Life
The most widely accepted hypothesis of Earth’s origins is the nebula hypothesis.
There are two organic molecule hypotheses.
Miller-Urey experiment: test input of E from light
meteorite hypothesis: off Australia, had 90aa found on Earth
electrodes
heat source
amino acids
water
“atmosphere”
“ocean”

11. There are different hypotheses of early cell structure.
iron-sulfide bubbles hypothesis
Martin/Russell proposed
Conditions needed for early life
lipid membrane hypothesis
Crucial step in the origin of life!

12. A hypothesis proposes that RNA was the first genetic material.
Ribozymes are RNA molecules that catalyze their own replication.
DNA needs enzymes to replicate itself.

13. 12.4 Early Single-Celled Organisms
Microbes have changed the physical and chemical composition of Earth.
The oldest known fossils are a group of marine cyanobacteria.
prokaryotic cells
added oxygen to atmosphere
deposited minerals

14. Fossil stromatolites provide evidence of early colonies of life.
Endosymbiosis is a relationship in which one organism lives within the body of another.
Mitochondria and chloroplasts may have developed through endosymbiosis.
Genetic variation is an advantage of sexual reproduction.
Sexual reproduction may have led to the evolution of multicellular life.

15. 12.5 Radiation of Multicellular Life
Life moved onto land during the 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.

16. Reptiles radiated during the Mesozoic era.
The Mesozoic era is 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.

17. Mammals radiated during the Cenozoic era.
The Cenozoic era began 65 million years ago and continues today.
Placental mammals and monotremes evolved and diversified.
Anatomically modern humans appeared late in the era.

18. 12.6 Primate Evolution
Primates are mammals with flexible hands and feet, forward-looking eyes and enlarged brains.
Primates evolved into prosimians and anthropoids.
Prosimians are the oldest living primates.
They are mostly small and nocturnal.

19. Anthropoids are humanlike primates.
They are subdivided into the New World monkeys, Old World monkeys, and hominoids.
Homonoids are divided into hominids, great apes, and lesser apes.
Hominids include living and extinct humans.

20. Bipedal means walking on two legs.
foraging
carrying infants and food
using tools
Walking upright has important adaptive advantages.

21. Modern humans arose about 200,000 years ago.
Homo sapiens fossils date to 200,000 years ago.
Human evolution is influenced by a tool-based culture.
There is a trend toward increased brain size in hominids.
Australopithecus
afarensis
Homo habilis
Homo
neanderthalensis
Homo sapiens