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The History of Life Chapter 12. The Fossil Record Fossil Forming  Perminerilization  Natural Casts  Trace Fossils  Amber preserved fossils  Preserved.

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Presentation on theme: "The History of Life Chapter 12. The Fossil Record Fossil Forming  Perminerilization  Natural Casts  Trace Fossils  Amber preserved fossils  Preserved."— Presentation transcript:

1 The History of Life Chapter 12

2 The Fossil Record Fossil Forming  Perminerilization  Natural Casts  Trace Fossils  Amber preserved fossils  Preserved remains Most fossils form in sedimentary rock

3 The Fossil Record

4 Relative Dating  Estimates the time an organism was alive based upon it’s placement in rock layers  Allows for inferences of species origin  Does not provide actual age dating of fossil

5 The Fossil Record Radiometric Dating  Estimates actual or absolute age  Calculation of the age of a sample based upon the amount of remaining radioactive isotopes Half life  The amount of time it takes for half of the iostopes in a sample to decay into another element  Different items have different half lives

6 The Fossil Record Carbon-14 Dating  Good for recent remains  Carbon-14-taken up by organisms while they are alive  C-14 begins to break down when organism dies  Researchers compare the amount of Carbon-14 to Carbon-12 or Nitrogen-14 The larger the ratio of C-14 to C-12 (or N-14), the older the organism

7 The Geologic Time Scale Index Fossils  Easily recognized and the species must have existed for a short period, but have a wide geographic range It will only be found in a few layers, but they will be specific and in different locations  Trilobite

8 Geologic Time Scale Evolutionary time is represented by the Geologic Time Scale  This orders rock by age Divided into units based on order rocks and fossils were formed

9 Geologic Time Scale Time between the Precambrian period and now is divided by eras  Paleozoic  Mesozoic  Cenozoic These divisions are defined somewhat by the organisms present

10 Geologic Time Scale To further define time, eras are divided into periods The Cambrian period is important to biology due to the huge explosion of organisms Epochs  Smallest unit of time; several million years

11 Origin of Life Earth is about 4.6 billion year old How did the earth get here? Formed by a condensing nebula Material pulled together Collisions caused the formation of planets

12 Origin of Life Earth was very hot, violent first 700 million years Many objects struck Earth releasing heat – kept Earth in a molten state  Objects eventually separated into layers Hydrogen, carbon monoxide, water vapor, methane, and carbon dioxide released  Oxygen not released until about 2 billion years ago

13 Origin of Life Miller-Urey Experiment  Lightning strikes caused inorganic molecules to form organic molecules  Electricity applied to these inorganic molecules led to the production of amino acids

14 Origin of Life Meteorite Hypothesis  Amino acids have been found in meteorites  Suggests that amino acids could have been present when Earth formed

15 Origin of Life Iron Sulfide Hypothesis  Iron sulfide from deep sea vents form chimneys  Compartments in these chimneys acted as pockets for biological molecules  The walls of these compartments acted as the first cell membranes

16 Origin of Life Lipid Membrane Hypothesis  Lipids tend to form spheres – liposomes  These spheres could enclose organic molecules  Give rise to cells

17 Origin of Life RNA – Early Genetic Material  Ribozymes – RNA molecules that can catalyze chemical reactions  Can make enzymes that would cut itself, copy itself, and make more of itself  Short chains of RNA can form from inorganic molecules

18 Early Single-Celled Organisms Early microbes changed the Earth  Deposited minerals, gave off oxygen  Cyanobacteria – bacteria that carry out photosynthesis Stromatolites – colonies of cyanobacteria  Release of oxygen allowed for aerobic organisms

19 Early Single-Celled Organisms Early prokaryotes are considered the ancestors of eukaryotes Early on some smaller prokaryotes began to enter into other prokaryotes Endosymbiotic Theory  Eukaryotic cells arose from living communities formed by prokaryotic cells

20 Eukaryotic Origins Evidence of the Endosymbiotic Theory  Mitochondria and chloroplasts: Contain DNA similar to bacterial DNA Have ribosomes whose structure and size closely resemble bacterial ribosome Reproduce by binary fission These three key pieces of evidence are what give credence to the idea that eukaryotes formed from prokaryotes

21 Reproduction and Multicellularity After arrival, eukaryotes reproduced sexually This increased the speed of evolution Sexual reproduction allowed for shuffling of genes Offspring never resembled their parents exactly This increased the gene combinations – So?

22 Early Single-Celled Organisms Sexual Reproduction vs. Asexual reproduction  Asexual – ease, rate of reproduction, energy efficient  Sexual – genetic diversity, increase in evolution

23 Paleozoic Era Fossil evidence shows a very diverse life during this era Was initially thought that much of this life originated during this era Actually came about much earlier

24 Cambrian Period Cambrian Explosion  The explosion and diversification of life during this period Organisms had shells and outer skeletons Common organisms:  Jellyfish, worms, sponges  Brachiopods, trilobites

25 Ordovician and Silurian Periods Ancestors of modern octopi and squid appeared Arthropods became the first land animals Jawless fishes became the first vertebrates Plants evolved from aquatic ancestors

26 Devonian Period Plants began to adapt to drier areas This allowed for invasion of new habitats “Age of Fishes”  Many groups of fishes present in the oceans Vertebrates began to also invade land

27 Carbiniferous and Permian Period Reptiles evolved from amphibians Winged insects began to appear  Dragonflies and cockroaches Plants became abundant and when they died, their remains are now coal

28 Mesozoic Era Lasted approximately 180 million years This era is marked by two main features  Dinosaurs  Flowering plants

29 Triassic Period Fishes, insects, reptiles, and cone-bearing plants were prominent “Age of the Reptiles”  Coelophysis – meat eater Mammals first appeared – mouse or shrew style

30 Jurassic Period Dinosaurs the prominent life form Ruled the earth for about 150 million years Many scientists think that birds are close relatives

31 Cretaceous Period Dinosaurs still present New life came about:  Leafy tress  Shrubs  Small flowering plants Another mass extinction brought this period to and end  More than half the plant and animal groups wiped out

32 Cenozoic Era About 65 million years ago Mammals evolved  Could live on land, in water, and even the air Tertiary Period  Warm and mild climate  Whales and dolphins evolved Quaternary Period  Climate cooled – ice ages  Earth warmed up about 20,000 years ago  Homo sapiens – 200,000 years ago in Africa

33 Extinction 99% of all species that ever existed are extinct Extinctions happen for reasons  Resources  Environments change Each extinction brings an opportunity for other species to succeed

34 Primate Evolution Common Ancestors  Primates are mammals with flexible hands and feet  Divided into two groups Prosimians Anthropoids

35 Primate Evolution Promisians  Oldest primate group  Active at night  Lemurs, tarsiers Anthropoids  Divided into old and new world monkeys as wells as hominoids  Hominids can be even further divided Lesser apes (gibbons) Greater apes (gorillas) Hominids (humans)

36 Primate Evolution Bipedalism  Walking upright, on two legs  Came before larger brains and tool manipulation  Allowed to reach higher into trees, freed the hands

37 Primate Evolution Early Human Fossils  Two important genus Homo Australopithecus  Homo habilis  Homo neanderthalensis Neanderthals  Homo sapiens Modern humans

38 Primate Evolution Human Evolution  Modern humans came about 100,000 years ago  Came out of Ethiopia  Brain was key to evolution Enlarged skull and brain

39 Primate Evolution Australopithecus afarensis Homo erectus Homo neanderthalensisHomo sapiens


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