Presentation on theme: "The History of Life & the Origin of Species"— Presentation transcript:
1The History of Life & the Origin of Species Georgia Performance Standards:SB5a: Trace the history of the theory of evolution.SB5 c: Explain how fossil and biochemical evidence support the theory of evolution.Essential Questions:Why are there species alive now that were not found in the past fossil record?Why is important to understand evolutionary theory?How does fossil and biochemical evidence support the evolutionary theory?
214–1 The Fossil Record You can study life’s history by examining fossils.The fossil record provides evidence about the history of life on Earth.It also shows how different groups of organisms have changed over time.Paleontologists are scientists who collect and study fossils.
3Fossils can show: That life on Earth has changed over time. What past life forms were like and if they are extinct (the species died out)The structure of the organismsWhat they ateWhat ate themThe environment in which they lived.
4How Fossils FormEither the remains of the organism or some trace of its presence must be preserved.Most fossils form in sedimentary rockThe quality of fossil preservation varies.
5Formation of a FossilSection 17-1Dead organisms are buried by layers of sediment, which forms new rock.Water carries small rock particles to lakes and seas.The preserved remains may later be discovered and studied.Go to Section:
7Interpreting Fossil Evidence Relative dating, the age of a fossil is determined by comparing its placement with that of fossils in other layers of rockuse index fossils to compare the relative ages of fossils.Relative dating allows paleontologists to estimate a fossil’s age compared with that of other fossils.
8Interpreting Fossil Evidence Radioactive dating is the use of half-lives to determine the age of a sample.A half-life is the length of time required for half of the radioactive atoms in a sample to decay. In radioactive dating, scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains.
9Compare/Contrast Table Section 17-1Comparing Relative and Absolute Dating of FossilsCan determineIs performed byDrawbacksRelative Dating(Absolute Dating) Radioactive DatingAge of fossil with respect to another rock or fossil (that is, older or younger)Age of a fossil in yearsComparing depth of a fossil’s source stratum to the position of a reference fossil or rockDetermining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimenImprecision and limitations of age dataDifficulty of radioassay laboratory methodsGo to Section:
10Geologic Time ScalePaleontologists use divisions of the geologic time scale to represent evolutionary time.After Precambrian Time, the basic divisions of the geologic time scale are eras and periods.
11Geologic Time ScaleGeologists divide the time between the Precambrian and the present into three eras.Paleozoic EraMesozoic EraCenozoic EraEras are subdivided into periods, which range in length from tens of millions of years to less than two million years.
15Chapter 14The History of Life14.1 Fossil Evidence of ChangePlate tectonics describes the movement of several large plates that make up the surface of Earth.These plates, some of which contain continents, move atop a partially molten layer of rock underneath them.
17Concept Map Evolution of Life Section 17-2 Go to Section: Early Earth was hot; atmosphere contained poisonous gases.Earth cooled and oceans condensed.Simple organic molecules may have formed in the oceans..Small sequences of RNA may have formed and replicated.First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.Later prokaryotes were photosynthetic and produced oxygen.An oxygenated atmosphere capped by the ozone layer protected Earth.First eukaryotes may have been communities of prokaryotes.Multicellular eukaryotes evolved.Sexual reproduction increased genetic variability, hastening evolution.Go to Section:
18Spontaneous generation is the idea that life arises from nonlife. Chapter 14The History of Life14.2 The Origin of LifeOrigins: Early IdeasSpontaneous generation is the idea that life arises from nonlife.Francesco Redi, an Italian scientist, tested the idea that flies arose spontaneously from rotting meat.
19Chapter 14The History of Life14.2 The Origin of LifeThe theory of biogenesis states that only living organisms can produce other living organisms.Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms.
20Simple organic molecule formation Chapter 14The History of Life14.2 The Origin of LifeOrigins: Modern IdeasSimple organic molecule formationThe primordial soup hypothesis was an early hypothesis about the origin of life.Organic molecules could have been synthesized from simple reactions.UV light from the Sun and electric discharge in lightning might have been the primary energy sources.
21Chapter 14The History of Life14.2 The Origin of LifeStanley Miller and Harold Urey were the first to show that simple organic molecules could be made from inorganic compounds.Later, scientists found that hydrogen cyanide could be formed from even simpler molecules in simulated early Earth environments.
23Life requires proteins. Chapter 14The History of Life14.2 The Origin of LifeMaking ProteinsLife requires proteins.One possible mechanism for the formation of proteins would be if amino acids were bound to a clay particle.
24Some RNA sequences appear to have changed very little through time. Chapter 14The History of Life14.2 The Origin of LifeGenetic CodeSome RNA sequences appear to have changed very little through time.Many biologists consider RNA to have been life’s first coding system.Other researchers have proposed that clay crystals could have provided an initial template for RNA replication.
25Scientists hypothesize that the first cells were prokaryotes. Chapter 14The History of Life14.2 The Origin of LifeCellular EvolutionScientists hypothesize that the first cells were prokaryotes.Many scientists think that modern prokaryotes called archaea are the closest relatives of Earth’s first cells.
26Photosynthesizing Prokaryotes Chapter 14The History of Life14.2 The Origin of LifePhotosynthesizing ProkaryotesArchaea are autotrophic.They do not obtain their energy from the Sun.Archaea also do not need or produce oxygen.
27Chapter 14The History of Life14.2 The Origin of LifeMany scientists think that photosynthesizing prokaryotes evolved not long after the archaea.Prokaryotes, called cyanobacteria, have been found in rocks as old as 3.5 billion years.
28The Endosymbiont Theory Chapter 14The History of Life14.2 The Origin of LifeThe Endosymbiont TheoryThe ancestors of eukaryotic cells lived in association with prokaryotic cells.The relationship between the cells became mutually beneficial, and the prokaryotic symbionts became organelles in eukaryotic cells.This theory explains the origin of chloroplasts and mitochondria.
29Chapter 14The History of Life14.2 The Origin of Life
31Checkpoint Questions: What can be learned from the fossil record?Which type of dating provides an absolute age for a given fossil? Describe how this is done.How are eras and periods related?Many more fossils have been found since Darwin’s day, allowing several gaps in the fossil record to be filled. How might this information make relative dating more accurate?