“Nothing in biology makes sense except in the light of evolution.” Theodosius Dobzhansky, 1973 Theodosius Dobzhansky (25 Jan. 1900 – 18 Dec. 1975) was a noted geneticist and evolutionary biologist, born in Ukraine (then part of Imperial Russia) and emigrated to the United States in 1927.

Fossils Fossils are the preserved remains of organisms. They may consist of hard parts: Teeth bones and shells of animals, or Moulds (leaves and stems of plants have decayed, leaving an impression of the plant in the rock.) Moulds may fill with another sediment, making a cast. Trace fossils are traces of living things (eg. footprints or tracks) 12 BIOLOGY, CH 10

Fossilisation Organic matter must be deposited in an environment that lacks oxygen or water or both. The seabed is a very good site for fossils. Limestone generally contains more fossils than other rock types. Mineralisation occurs when minerals have replaced the natural bone or shell salts Sedimentary material, such as mud, silt or sand is carried by rivers and streams and forms sedimentary rock. Sedimentary material can protect organic matter from scavengers and slow decay. Fossils are never found in volcanic rocks as molten lava is hot enough to burn any organic material. 12 BIOLOGY, CH 10

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Set 1 SRAM 343-4, 2012: Fossil Record 12 BIOLOGY, CH 10

Dating Fossils Relative age of fossils is obtained from stratification (comparing fossils in similar sedimentary layers) Index fossils are fossils that occur in layers of the same age. Absolute dating techniques: Radiodating - some elements occur as isotopes that have an unstable nucleus and emit radioactive particles. The half-life of an isotope is the time taken for half of the radioactive atoms to decay. 12 BIOLOGY, CH 10

Half-life 12 BIOLOGY, CH 10 (From Jacaranda 3&4)

Half-life of Carbon-14 The age of a fossil can be determined by measuring the proportion (percentage) of 14C to 12C in a sample. When the fossilised organism was alive its 14C/12C ratio was constant (the same as the atmosphere). From the time the organism died the amount of 14C reduced because it decays at a known rate to nitrogen-14 (14N). The 14C decays by half every 5730 years (its half-life) as shown in the graph. 12 BIOLOGY, CH 10 (From Heinemann 3&4)

Half-life of Potassium-40 The element potassium is present in minerals that are found in rocks. A small amount (about 0.012 %) of K is in the form of the radioactive isotope K-40, while most is in the stable form of K-39. K-40 decays at a known constant rate to form the inert gas, argon-40, which accumulates within K-containing mineral crystals in rock. The older a rock, the longer the time for K-40 to decay and for Ar-40 to accumulate. The K-39 does not decay and it provides a measure of the original amount of K-40 present. 12 BIOLOGY, CH 10 (From Jacaranda 3&4)

Electron spin resonance (ESR) Minerals collect electrons in their crystal lattice over time. The electrons are mildly magnetic and this magnetism can be measured to give an electron spin resonance reading. ESR is useful for dating corals, quartz and mollusc shells, as well as tooth enamel. 12 BIOLOGY, CH 10

Luminescence techniques Thermoluminescence (TL) is the light that is emitted from a mineral when it is heated. Optically stimulated luminescence is the light that is emitted from a mineral when it is exposed to visible light. 12 BIOLOGY, CH 10

Set 2 12 BIOLOGY, CH 10

Geological time Earth time Geological time is divided into: ERAS which are subdivided into PERIODS which are then subdivided into EPOCHS It is specified in millions of years before present (m.y.B.P.) Earth’s Age 12 BIOLOGY, CH 10

Pangea and Gondwana The Earth’s crust floats on the fluid mantle underneath The crust is divided into plates which collide with each other and cause earthquakes, volcanoes, etc. 200 mya a single super-continent, Pangea, existed and broke up into Laurasia in the north (Nth. America, Asia, Europe), and Gondwana (Antarctica, Australia, NZ, India, Sth. America) over 20 million years. Gondwana broke up over the next 100 m.yrs. Gondwana Split Continental Drift Australian Drift Ancient maps 12 BIOLOGY, CH 10

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Temp, climate & sea levels Evidence from a number of sources has indicated that the Earth has undergone many changes over millions of years. 12 BIOLOGY, CH 10

Bacteria can thrive in atmospheric conditions of low oxygen. Oxygen levels Bacteria can thrive in atmospheric conditions of low oxygen. Larger eukaryotic cells have a much smaller surface area to volume ratio than the smaller prokaryotic bacteria. It was not until 700–750 million years ago that the atmospheric oxygen level was high enough to support larger eukaryotic cells, and hence multicellular organisms. 12 BIOLOGY, CH 10

Ancient oxygen levels http://www.csiro.au/helix/sciencemail/newsletter.html 12 BIOLOGY, CH 10

Set 3 12 BIOLOGY, CH 10

Patterns of evolution Divergent evolution A group of organisms that has a recent common ancestor may develop – evolve – different adaptations in response to a range of environmental pressures. As a population moves into unfilled niches, its members evolve adaptations over successive generations that enable them to exploit it. They may diverge enough to become new species. The process is sometimes called adaptive radiation. 12 BIOLOGY, CH 10

Comparative Anatomy Embryology Study of structural similarities and differences of embryos of different species. 12 BIOLOGY, CH 10

Comparative Anatomy Homologous structures Pentadactyl limb SRAM 345, 2012: Homologous Structures 12 BIOLOGY, CH 10

Analogous structures Analogous structures are features of organisms that have the same function but not the same basic structure. Wings of bats, birds, butterflies Octopus and human eyes 12 BIOLOGY, CH 10

Videos about the Evidence for Evolution: Richard Dawkins: “Show me the Intermediate Fossils”. What Every Creationist Must DENY. A MUST see for Creationists. 60 Transitional Fossils in 4 Minutes. 12 BIOLOGY, CH 10

Set 4 12 BIOLOGY, CH 10

Set 5 12 BIOLOGY, CH 10

Set 5 12 BIOLOGY, CH 10

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….. another possibility …… 12 BIOLOGY, CH 10

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Isaac NEWTON Albert EINSTEIN Charles DARWIN 12 BIOLOGY, CH 10