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

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Presentation on theme: "Ch 12: The History of Life. Specific environmental conditions are necessary in order for fossils to form. 12.1 The Fossil Record."— Presentation transcript:

1 Ch 12: The History of Life

2 Specific environmental conditions are necessary in order for fossils to form The Fossil Record

3 Fossils can form in several ways. Permineralization occurs when minerals carried by water are deposited around a hard structure The Fossil Record

4 Fossils can form in several ways. A natural cast forms when flowing water removes all of the original tissue, leaving an impression The Fossil Record

5 Trace fossils record the activity of an organism. Fossils can form in several ways The Fossil Record

6 Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried The Fossil Record Fossils can form in several ways.

7 Preserved remains form when an entire organism becomes encased in material such as ice The Fossil Record

8 Specific conditions are needed for fossilization. Only a tiny percentage of living things became fossils The Fossil Record

9 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 placement of fossils in layers of rock. – Scientists infer the order in which species existed The Fossil Record

10 –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 The Fossil Record

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

12 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.

13 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.

14 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

15 Multicellular life evolved in distinct phases.

16 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.

17 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.

18 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.

19 Humans appeared late in Earth’s history.

20 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.

21 Primates

22 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)

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24 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 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

25 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

26 Examples of Hominid Skulls Australopithecus afarensis Homo habilisHomo neanderthalensis Homo sapiens

27 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!!!!!!


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