Life on Earth Year 11 Biology

Life On Earth

Life on Earth1. Analysis of the oldest sedimentary rocks provides evidence for the origin of life.1.2.1. Identify the relationship between the conditions on early Earth and the origin of organic moleculesHow old is the Earth? 4.6 Billion Years Old Earth formed about 4600mya. Age is based on age of mineral crystals. WA = oldest crystals, 4400mya. Some of our most primitive meteorites are remnants of t his time. Life thought to have originated 3500-4000mya.How Did the Earth Form? Big bang theory = an explosive event marked beginning of universe, about 20,000mya, throwing compacted material outward and producing the expanded universe as it is today. Thought that solar system formed from a cloud of dust and gases (solar nebula) which collapsed and condensed over time (1 mil yrs). Once there was significant mass in centre, nuclear reactions (fusion reactions which release a great deal of energy) were finally triggered that ignited proto-sun. Surrounding gases condensed to form planets Collision and mass aggregation of the gases over time resulted in formation of early earth. Solar nebula = remnant of an earlier star that has completed its life and exploded e.g. supernova Fusion = combining of nuclei of light element (H) into those of a heavier element i.e. HE. The resultant loss of mass is converted into energy (stars and thermo-nuclear weapons use this kind of reaction).Conditions on the Early Earth For first 500myrs of earths existence, earth was frequently bombarded by asteroids, comets and other fragments left over from the formation of the planets of the solar system. Earths surface was hot and was exposed to destructive shortwave UV from sun, no ozone as there was no gaseous oxygen. Volcanic eruption and violent electrical storms also occurred No seas, lakes, rivers and water lifelessThe First Atmosphere leftover stardust (H, He lightweight gases that could not be retained by earths gravitational pull and gradually escaped into space)

The Secondary Atmosphere Permanent secondary atmosphere developed several hundred myas. Believed to have originated from emission of volcanic gases: volcanic outgassing Atmosphere consists of: H2O vapour, CO2, N2; smaller amts methane (CH4), ammonia (NH3), sulfurous gases (corrosive sulphur dioxide (SO2) and hydrogen sulfide (HS) ) NO FREE OXYGEN (ANOXIC) bound to other elements water (H2O), carbon monoxide (CO), carbon dioxide (CO2), SiO2 quartz)Rain Earths secondary atmosphere initially thin with low air pressure As more gases were added from volcanic activity, air pressure increased. Because temp range was suitable, this increase in air pressure caused water vapour to condense as liquid water. Rain, eventually forming seas & oceans. Presence of liquid water essential condition for evolution of life on earth Sedimentary rock (sandstone, mudstone) 3800mya evidence that water cycle existed as composed of particles eroded from pre-existing rocks deposited under water and compacted into rock. Other evidence = ripple marks on ancient rocksThe Impact of Water on CO2 (Disappearance of CO2) Early earths atmosphere originally had high concentration of CO2 but today its low (0.03%). It turned into rock. CO2 readily dissolves into water. When water cycle was established on earth, CO2 gas flushed out of atmosphere into seas by rain.CO2 reacts with water to form carbonic acid, H2CO3. H2CO3 reacted with dissolved mineral ions in seas such as Ca and produced insoluble calcium carbonate- CaCO3 that was deposited on sea floor. Sediments later compressed to form rocks (chalk) After removal of CO2 principal gas remaining in atmosphere was NKey Phases in the Origins of the Earth Gases and dust condensed (4.5 billion yrs ago) Early Earth (Hot, Volatile, Lightweight gases) Secondary Atmosphere (Outgassing, heavier gases, rain) The Water Cycle Reduced Carbon Dioxide

1.2.2 Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on earthWhat are Organic Molecules? Carbon based molecules Carbon- forms strong bonds with itself and can form complex molecular structures- long chains, branching chains and rings.The Beginning of Life on Earth- When and How? Hadeon eon 4600-3900mya earth apparently lifeless Archaean eon 3900-2500mya first evidence of life (rocks) 3500-4000mya earth had right conditions for life to exist several theories about originWhat we know: Living organisms require liquid water became available once water cycle established (at least 3800mya). Living organisms require an energy source for functioning & reproduction (energy sources on early earth were chemical and UV radiation) Living organisms consist of organic (carbon based) molecules Life needs protection from harmful UV radiation coming from sun.Chemicals for Life (ORGANIC MOLECULES) none present on early earth Water H, O CarbohydratesC, H, O LipidsC, H, O Proteins (20 amino acids)C, H, O, N, S, P Nucleic Acids (DNA/RNA)C, H, O, N, P

1.2.3 Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of lifeWhat is Necessary for Life? Essential components for the emergence of life on Earth included the presence of the following: Liquid water provides medium where reactions necessary for life occur, essential solvent for many materials A useable energy source functioning and reproduction; chemical energy and sunlight Organic molecules proteins, carbohydrates, lipids, nucleic acids: NONE PRESENT ON EARLY EARTHFrom where did the first organic molecules come?Two hypothesises:a) Organic molecules were carried here from outer spaceb) Organic molecules were produced on the early earth under the conditions that existed at that time.Theory 1 Organic molecules that are building blocks of life could have been transported to the earths surface from space, carried here on meteorites. Meteorite: fragment of solar system that has fallen to the earths surface. They can be fragments of asteroids, comets or blasted from the surface of planets- Mars. Organic molecules are NOT living organisms (not saying life itself travelled from outer space). Panspermia hypothesis. Certain types meteorites (carbonaceous chrondrites) found to contain organic molecules including amino acids, some of which same as found on earth and some completely different.Murchison meteorite 1969 meteorite piece landed on farmland near Murichson, central Victoria Murichson farm contained 92 amino acids, 19 similar to those found on earth, the rest unlike anything found on earth Pieces collected on same day and handled carefully to avoid contamination Analysis revealed many amino acids (protein) Amino acids on earth consist exclusively of L-form, meteorite = D and L-forms not due to contamination by organisms from earth Provided evidence that organic molecules can be formed extraterrestrial & gave support to hypothesis that some of the organic molecules on early earth might have come from space.Theory 2 Correct conditions existed on earth for creation of complex organic molecules Energy from UV radiation or lightening strikesExperimental evidence January 2001 NASA experiment results published = organic molecules can be made in space Scientists duplicated conditions existing in interstellar clouds in spaceThis is what they did:1. Mix water with inorganic chemicals that exist in interstellar clouds- ammonia, carbon monoxide, carbon dioxide and methanol.2. Freeze mixture in a vacuum at temp close to absolute zero (-263deg) to form space ice.3. Zap resulting ice with shortwave UV radiation. Experiment showed that the organic molecules that are building blocks of life can be produced in space. Conclusion: results of Miller and Urey experiment and related experiments show that organic molecules could have been produced on early earth. Other findings indicate that these organic molecules could have come from outer space. The origin of the organic molecules on early earth remains unresolved.Summary of theories1. Spiritual forces2. Outer space3. Reactions of chemicals on Earth

1.2.4 Discuss the significance of the Miller and Urey experiment in the debate on the composition of the primitive atmosphereMiller-Urey experiment: organic from inorganic In 1950s, Stanley Miller and Harold Urey conducted an experiment (carried at uni of Chicago 1953) that they believed demonstrated that several organic compounds, including amino acids could be formed spontaneously by simulating the conditions of Earths early atmosphere. Starting material = inorganic matter, water vapour and other gases that Urey believed were present in early atmosphere of earth. Electric discharge was like lightening.Evacuate air from a sterilised glass apparatus. Makes an anoxic environment.1. Add equal proportions of methane (CH4), ammonia (NH3) and hydrogen (H2).2. Add one cup of water3. Heat the water to boiling so that the apparatus becomes filled with steam (H2O vapour)4. Activate the electrodes so that repeated electric discharges are applied to the steam5. After some days, cool the apparatus so that the steam condenses to water that collects in the trap.

What did they find? Condensed water in apparatus went from colourless to dark. Organic molecules found including many amino acids (buildings blocks of protein). Miller and Urey success at converting carbon in methane and nitrogen in ammonia into many different kinds of organic molecules including amino acids. Oparin (1894-1980) and Haldane (1892-1964) hypothesised that organic molecules required for development for life were synthesised on early earth by natural chemical processes. Miller & Urey provided first experimental evidence that under conditions that may have existed on early earth, inorganic substances could be converted to organic molecules. modifications to experiment (by other scientists): started w different mixtures of inorganic molecules that probably existed in atmosphere of early earth used various energy sources produced range of inorganic molecules, including all 20 amino acids (protein), sugars (DNA/RNA), some lipids organic molecules needed for life could have been formed on early earth from simple inorganic molecules present in anoxic atmosphere and an energy source (UV, lightning, heat etc)

1.2.5 Identify changes in technology that have assisted in the development of an increased understanding of the origin of life and evolution of living things Atmosphere of early earth = CH4, H2, CO2, NH3 floating above bodies of warm water Energy source diffuses in, causes chemical reactions primitive soup of amino acids, nucleotides, sugars Living chemicals living cells in which all chemicals cooperatively function to maintain life cells divide, new organisms formExamples of changing in technology that enabled scientists to accumulate evidence take measurements and do experiments to develop and increase understanding of origin of life: Deep sea equipment that enabled exploration of remote env. E.g. ocean trenches X- ray crystallography Chemical analysis Chromatography Radiometric dating of rocks - uses known decay rates of radio-active isotopes Microscopy especially the electron microscope Biochemical analysis- especially DNA- enable comparison of organisms at genetic level, to see change and hence possible evolutionary pathways

Early technologies- experimental techniques improved over time Humans proposed hypotheses to explain origin of life Scientists independently developing new technologies enabling hypotheses to be tested cooperation of scientists and technologists in all branches of science REDI few glass jars and some cotton material maggots in decaying meat came from eggs laid by flies SPALLANZANIS FLASKS showed that the microorganisms in broth came from air SWAN-NECKED FLASKS designed by Louis Pasteur demonstrated that spontaneous generation didnt occur LIGHT MICROSCOPES Leeuwenhoek discovered in 1676 discover organisms not seen w naked eye More recent technologies The sequence of past events on earth had been determined before absolute dates could be assigned to them. Because the technology of radiometric dating had not been developed.Plate tectonics and continental drift Develop knowledge of structure of earth: Seismology: study of pressure/shock waves from earthquakes Seismograph: record wave patterns from earthquakes Studied changes in earths magnetic field and composition of meteorites/volcanoes Changing structure in surface layers of earth influenced origin/evolution of life Beginning 17C English philosopher Francis Bacon east coast America/west coast Africa FIT TOGETHER Supported by scientists study of fossil remains, identical species plants/animals 1912 WEGENER (German geologist) suggested land mass broke up and continents drifted apart 1965 J. TUZO WILSON (Canadian geophysicist) supported continental drift idea and introduced concept of sea floor spreading (ridges in sea floor produced new material and spread apart) Based on evidence from magnetic surveys of ocean ridges e.g. Mid Atlantic/East Pacific ridges Ships measured magnetic field direction in rocks either side ridge sample drilling on ocean floor, ultrasound depth sounding Rock age increased farther away from ridge on either side Plate tectonics: earths crust composed of 6 major plates 40km thick which move over partially molten layers of mantle below. As they move the plates bump into each other, move apart/slide past each other carrying oceans and continents w them (continental drift) major impact on theories relating to evolution on lifeRadiometric Dating Principle of superposition: the lower the strata, the older the stratum Developed chronology of geologic time periods/some forms of life As rocks form the older rocks were buried by newer rocks so the lower levels or strata became the oldest Organisms in deeper layers were older than shallow areas Stratigraphic correlation: correlation (relate together in order) of the strata from different locations of being of the same or different ages Similar fossils found in widely different locations were found to be same age Radioactivity: emission of alpha, beta, gamma rays from unstable isotopes of some elements each isotope decays emits radiation and forms another element at its own constant rate As rocks/living matter form, radioactive isotopes are incorporated into them in proportion to the isotopes abundance in environment. When dead, level of radioactive isotope decreases as no further matter exchange w environment Measurement of radioactive to stable isotope in the sample can indicate its age (each isotopes decay acts as radiometric clock) U-238 common radioisotope used by geochemists to measure rock ages long half life, decays into lead By measuring amt U-238 still present in rock compared w amt lead, rock age = 95% accuracy Isotopes w long half lives can be used to date old formations (C-14 half life of 5500yrs, commonly used) Radiometric dating: established age of earth as 4.5b years older than previously estimatedOther technologies Simulation of conditions in early earth testing feasibility of hypotheses (depend on construction of equipment modern laboratory technology) Electron microscopy microorganism remains/mineral nature of early rocks can be studied under electron microscope Nature of minerals gives clues to environment; structure of organisms reflects possible survival in environment Modern techniques in biochemical analysis enable comparisons between ancient organic material/biological compounds Gas/liquid chromatography Radioactive tracing Spectrophotometry Amino acid and nucleoid sequencing 3 major sources of knowledge/understanding about earths past/origin of life1. Earths geological history2. Fossil record3. Studies of biochemistry/metabolism of modern organisms1.3.1 Gather information from secondary sources to describe the experiments of Urey and Miller and use the available evidence to analyse:Reason for their experimentsTo verify whether it was possible for organic molecules to have formed in a reducing and energy rich environment similar to that of early earth.Result of their experimentsNumerous organic molecules were produced in the simulated conditions. (Amino acids, sugars, lipids and building blocks for nucleic acids)Importance of their experiments in illustrating the nature and practice of scienceScientists have proposed a model and through experimentation it was demonstrated that the model could have been correct. Urey and Miller demonstrated usefulness of modelling showing that it was possible that organic molecules were formed on early earth from inorganic.Contribution to hypothesis about the origin of lifeSupport for Haldane and Oparins theories about how the first organic molecules could have formed. These scientists believed that the first organic molecules could have evolved in the conditions of early earth.

2. The fossil record provides information about the subsequent evolution of living things2.2.1 Identify the major stages in the evolution of living things, including the formation of organic molecules, membranes, procariotic cells, eukaryotic cells, endosymbiosis and various orgamismsOrganic Molecules As primitive biological concentration increased, reacted w each other to form more complex molecules Most stable survived - natural selection Once chemical compounds had evolved, they began to react w each other first metabolism Earliest microfossils found in Australia dated at 3.5by; south Africa at 3.4by Aggregation of organic chemicals to form first cells must have occurred following first billion years of earthMembranes Chemical compounds separated from surroundings metabolise effectively (e.g. valuable products not lost) Membranes formed around chemicals, producing first primitive cells Hydrophobic molecules cluster together form boundary between them and surrounding aqueous solution E.g. oil drops in water. Lipids and many large proteins have hydrophobic parts and could have separated themselves from surrounding water. Microspheres (small drops) of chemicals can form when certain chemicals are mixed together, simple chemical reactions can take place inside them. Theyre not cells but precursors. Microspheres contents separated from external environment by primitive liquid membranes Some compounds could have assumed role of enzymes (biological catalyst) directed metabolism inside cells Eventually material similar to RNA could have begun to replicate and set in action first cellular reproductionProkaryotic cells Cell wall, cell membrane, cytoplasm- organic chemicals; one organelle- ribosome- synthesises proteins. Dominated earth for about 2b years before eukaryotic cells evolved smaller than eukaryotic Two major groups are: Bacteria (heterotrophic) Cyanobacteria (autotrophic)

Heterotrophic and autotrophic prokaryotes (3.5 1.5bya) Heterotroph: use chemicals from outside sources for energy/synthesis of molecules Autotroph: make own compounds from simple molecules/light energy Early cells heterotrophic, eventually used up all biological molecules in environment Environmental pressure favouring autotrophs (make own molecules from environment) Heterotrophs continued to exist but depended on autotrophs for nutrientsEukaryotic cells Development of compartments (organelles) w/in cells to separate some metabolic reactions from others Cells with these compartments (organelles) were at advantage. First eukaryotic cells. Loose cooperative associations between cells = colonial organisms Permanent associations between cells = multicellular organisms Eukaryotic cells emerged during Precambrian period in environment dominated by prokaryotic cells 2-1byaThe Endosymbiotic symbiosis How did the eukaryotic cell emerge? Endosymbiotic hypothesis: the eukaryotic cell is the result of the symbiotic relationship between small groups of prokaryotic cells. Primitive prokaryotic cells became organelles inside eukaryotic cells Organelles (except ribosomes) not been found in primitive prokaryotic cells O2 accumulated in atmosphere 2.5-2bya evolutionary pressure placed on organisms for survival Organisms that could use O2 were favoured prokaryotic organisms present at time adopted various strategies:1. Occupied anaerobic environments (marshes, swamps, sea floor); evolved into modern bacteria (decomposers)2. Species that could use O2 evolved into modern forms of aerobic bacteria3. Some associated symbiotically to form eukaryotic cells Smaller prokaryotes lived inside larger prokaryotes first eukaryotic cells symbiotic cells were possible forerunners of eukaryotic cell Smaller cells = nutrients/protection, larger cells = new material/energy Mitochondria in eukaryotic cells believed to be descended from specialised bacteria Mitochondria and chloroplasts contain their own DNA (probably own cell once). Mitochondria & chloroplasts contain small ribosomes like bacteria. Mitochondria- membranes contain enzymes like those in bacterial membranes Believed symbiotic relationships established at different sites great diversity eukaryotic cells Endosymbiotic hypothesis also accounts for fact that complex or simple organelles (apart from ribosomes) have not been found in primitive prokaryotic cells. A small number of modern cells live symbiotically w/in larger cells (feasible) Australian termite digest wood because Endosymbiotic protist present in gut Unicellular to Multicellular 1.5-0.5bya Sexual reproduction in eukaryotic cells = 1.5-0.5byaFirst eukaryotic organisms from Protista kingdom Independent evolutionThree groups of protists;1. Algae photosynthetic, some multicellular Chlorophyta (green algae) believed precursors of plants2. Slime moulds resemble fungi in some ways3. Protozoa/unicellular heterotrophs that are animal likeColonial organisms Individual cells subjected to certain environmental pressures associated together into colonies Cells connected by cytoplasm strands that integrate colony still maintain degree of independence modern green algae, colonial; Volvox likely some cells become permanently attached to each other in some colonies function more efficiently than as independent colonial cellsMulti-cellular organisms functions of different cells became specialised another method by which unicellular organisms could have changed = repeated cell divisions w/out cytoplasmic division one large cell, many nuclei

2.2.2 Describe some of the paleontological and geological evidence that suggests when life originated on earth study of rocks/fossils = evidence of early life forms and activities oldest sedimentary rocks about 3800myPaleontological evidence microfossils similar to present day single celled anaerobic prokaryotic organisms Fossilised chains bacteria like cells found in rocks in Marble bar region in WA earliest direct evidence life on earth occur in rocks dated 3500my first living cells appeared on earth at least 3465mya

microbe/microscopic organism Recently some scientists have challenged validity of Marble Bar fossils and argued that these particular structures were produced by geochemical not biological action. Stromatolites layered mats photosynthetic prokaryotic cells (cyanobacteria) modern descendants WA 3500myo Aus Stromatolites (cyanobacteria aggregation) fossils OLDEST EVIDENCE hundreds Stromatolites locations throughout WA: 3460my to present Stromatolites formed when filaments photosynthetic bacteria grow towards light during day; trap sediment sediment accumulates on/w/in layers microbial filaments at bottom shallow seas/lakes filaments lay flat at night and bind sediment fine layered structure Stromatolites 2800-3000my Fig Tree Group of rocks in South Africa Stromatolites 2000my Gunflint Chert rock found in shores of Lake Superior in Nth America microfossil/Stromatolites 3400-3500my rocks, Warrawoona Group in WAGeological evidence First microbes heterotrophic obtained energy by consuming other organic compounds by product O2 Carbon isotopes in rocks NOVEMBER 1996 chemical evidence (not fossilized microbes) tiny carbon particles found in 3850my old rock carbon atoms can exist in different forms- isotopes living organisms use lighter C-12 isotope during chemical reactions (C-13 heavier) substances made by biological processes = higher ratio lighter to heavier stable isotopes compared w substances made by geochemical processes SHRIMP instrument higher ratio isotopes. Scientists measured ratio of isotopes in the carbon particles from the rock. carbon inclusions had biological origin and provided indirect evidence that life existed on earth 3850mya Banded iron formations (BIFs) Generally believed O2 in chemical reaction w ferrous (Fe2+) ions present in solution in sea water 4Fe + 3O2 2Fe2O3 Insoluble ferric oxide deposited on sea floor deposition stopped from time to time, other material deposited (silica). This may have been because the pop of microbes died out at end of season. In time, the microbial pop recovered and the deposition of ferric oxide recommended and so on. Cyclic process produced rocks w dark layers ferric oxide interspersed w lighter coloured layers other material BIFs provide evidence for when1. The first photosynthetic microbes appeared on earth2. The first free O2 released into atmosphere BIFs produced in small amounts from 3400mya first photosynthetic microbes had evolved by that time Major production of BIFs occurred from 2500-2000mya O2 production by photosynthesis on global scale

2.2.3 Explain why the change from an anoxic to an oxic atmosphere was significant in the evolution of living thingHow life changed the earths environment Earths atmosphere changed over time originally no free O2 but now 21% atmosphere (produced by new types of microbes that used sunlight as an energy source - LIFE) First primitive cells were heterotrophic- obtained energy by consuming other organic compounds cells containing pigments developed photosynthesizedOxygen in the atmosphere 2000mya BIF stopped when all dissolved ferrous iron in sea oxidised O2 produced by photosynthetic microbes accumulated as free O2 (anoxic to oxic) Some of atmospheric O2 reacted w mineral deposits on land esp. ferrous iron oxidised surfaces to produce red-beds (formed 2000mya 800mya earth had fully rusted) some O2 tolerant microbes evolved ability to use in energy-releasing activities*aerobic respirationOxygen from sunlight-trapping microbes 3500-2700mya some microbes evolved ability to photosynthesise Possibly like present-day cyanobacteria that forms green slime on water Sunlight, H2O, CO2 readily available to use waste O2 produced eventually changed atmosphere (anoxic to oxic) Evolution of photosynthesis had dramatic effect on earths environment explosion in abundance photosynthetic organisms (multiplication in numbers) used up CO2 gradually reduced levels present in atmosphere O2 produced originally taken up by rocks oxidized rocks ancient banded iron/red bed rock formations Once rocks absorbed all O2 they could or became saturated, O2 became to build up as a gas. UV radiation from sun reacted with some of free O2 gas to form ozone. Eventually ozone formed round earth high in atmosphere- act as a shield absorbing UV radiation so less reach surface of earth.

The ozone Layer Sunlight acted on O2 MOLECULES in stratosphere (upper atmosphere) Split to form O2 atoms reacted w molecular O2 to form ozone (O3) O2 O + O O + O2 O3 Resulting ozone layer in stratosphere absorbs short wavelength UV (UVC and some UVB) radiation harmful to life Formation of ozone layer eventually helped organisms to colonise land surfaces and unshaded surfaces of water O2 levels rose, photosynthetic organisms = more abundant (more), growth/metabolism anaerobic organisms declined Significance of change from anoxic to oxic atmosphere is that anaerobic organisms declined. today anaerobic organisms survive only in very low O2 concentration mud in swamps/bogs, deep underground etc As O2 levels rose, living systems developed ways to use O2 directly to produce chemical energy. Aerobic organisms evolved and they could produce energy more efficiently via respiration. greater metabolic activity became possible organisms more active increase in size/complexity (eukaryotic cells evolved also multicellular plants and animals) O2 presence inhibits formation of complex organic molecules (amino acids)

2.2.4 Discuss the ways in which developments in scientific knowledge may conflict with the ideas about the origins of life developed by different cultures Some believe all creatures created when earth formed none descended/evolved from any other Biblical creationism- created by god on first 6 days

2.3.1 Process and analyse information to construct a timeline of the main events that occurred during the evolution of life on earth

2.3.2 Gather first-hand or secondary information to make observations of a range of plant and animal fossils

Stromatolites: They are formed from cyanobacteria whose filamentous gel like form trapped sediments in shallow, salty oceans.

Footprints: They are formed when an organism leaves an impression on a surface which is later filled in with other materials.

Mould: They are formed when an organism leaves an impression or mould which is later filled in with other materials.

Cast: They are formed when an organism leaves an impression or mould which is later filled in with other materials or the original organic material has been replaced by inorganic minerals in a process known as petrifaction.

Bones: They are formed when an organism dies and its squishy bits rot out and so all thats left is bones. The bone then decays and is slowly replaced by rock like minerals.

Fossil preserved in amber: They are formed when an organism gets preserved in amber (tree sap).

Actual preserved organism (e.g. in ice, peat, bog, etc): They are formed when an animal is buried rapidly by either ice or sediment. The decay of the organism must be prevented or reduced to allow fossilisation to occur.

Coprolite (fossilised animal excreta): They are formed from animals droppings. They are rapidly buried and the organic material is replaced with sediment, etc.

2.3.3 Identify data sources, gather, and process, analyse and present information from secondary sources to evaluate the impact of increased understanding of the fossil record on the development of ideas about the history of life on earth

Always been debates about when fossils were first recognised to be remains of living things. Some early European scholars claimed that fossils were accidents of nature Christians say that fossils can be a result of Noahs flood. Extinction believed to be a result of divine intervention or extreme natural catastrophe. Eventually Darwin and Lamarck suggested that extinction was natural part of evolution. Over last 150 years people are now accepting scientific explanation for the evolution of living things and the expanding fossil record has been a factor in this. Technology has greatly improved our understanding. E.g. mass spectrometers, remote sensing and imaging to locate fossil beds, use of computer modelling or biomechanics to produce realistic models of ancient organisms, CAT scans.

3. Further developments in our knowledge of present-day organisms and the discovery of new organisms allows for better understanding of the origins of life and the processes involved in the evolution of living things

3.2.1 Describe technological advances that have increased knowledge of prokaryotic organisms

ELECTRON MICROSCOPY Fine details e.g. structure of cells BIOCHEMISTRY Study of metabolic pathways = similarities/differences unknown before MOLECULEAR BIOLOGY Comparative sequencing of amino acids in proteins Nucleotide sequencing of RNA/DNA along lengths of chromosomes The more similar the sequences, the more closely related the organisms are considered to be clues to evolutionary relationships of organisms Allows to determine common ancestors of certain organisms CARL WOESE discovered 2 fundamentally different types prokaryotic cells comparative sequencing

3.2.2 Describe the main features of the environment occupied by one of the following and identify the role of this organism in its ecosystem

Archaea (means ancient) - group includes 3 sub-groups which all live in extreme hostile environments 1. Methanogens Environment- bogs, deep soils, marine and fresh water sediments, intestinal tracts of herbivores and in sewage treatment works. Anaerobic (obligate anaerobes) Use H2 as energy source, CO2 as carbon source and produce methane as by-product. Role in ecosystem- recycling of carbon, important decomposers. Methane released in air is part of carbon cycle Form symbiotic relationships with other organisms e.g. when found in get of cattle or termites Role: assist in break-down of cellulose- aids digestion in host. 2. Halophiles (halobacteria) Environment- very high salt concentrations e.g. Dead sea in Middle East, Great Salt lake, USA, and evaporating ponds of saline water Aerobic but have a second system for producing energy using photosynthesis which involves pink pigment, bacteriorhodopsin (so they can also produce energy without using O2). Pink tinge in salt flats may be detected and photographed by satellites. Role in ecosystem- part of food chain, consumed by filter feeders. Little known about role.

3. Thermopiles (or thermoacidophiles) Environment- requires high temps for growth (80-105deg), can live in highly acidic environments and can use sulphur as an energy source. Found in hot springs, geysers, hydrothermal vents (areas of volcanic activity) which are often highly acidic and in cracks of ocean floor. Sometimes called deep-sea bacteria. Some die if temp reaches as low as 55deg. Role in ecosystem- oxidise sulphur to produce energy, therefore primary producers (chemo-autotrophs, as opposed to photo- autotrophs) Ones live in deep sea are part of deep-sea floor web. Some organisms feed on them directly and others form a symbiotic relationship with them with bacteria providing nutrients and the organism providing shelter. E.g. giant tube worm which lives in hydrothermal vents, grows to over 1m in length, has now mouth, gut or anus and derives all its nutrition from the sulphur bacteria living in a special organ inside it called a trophosome.

3.3.1 Use the available evidence to outline similarities in the environments past and present for one of the following:

Archaea (Methanogens) Past environment: Thought to have dominated the anoxic environment of early earth. Present environment: Anaerobic conditions in swamps, the digestive system of ruminants. Some are found below the top layers of marine sediments. Also found in hot springs and hydrothermal vents. Have been found under kms of ice in Greenland and in the hot, dry soils of deserts.

3.3.2 Analyse information from secondary sources to discuss the diverse environments that living things occupy today and use available evidence to describe possible alternative environments in which life may have originated

Today living organisms exist in most places on earth from oceanic depths (even round Arctic and Antarctica) to high mountains (11300). Also found in extreme env such as volcanic vents, deep ocean trenches, hot springs, salty lakes, acidic and alkaline conditions, underground, under high pressure and many cold places. Idea of Haldane and Oparin: origins of life = warm, shallow seas. Since then other suggestions of origins have been made as result of discovering life in places that are thought to be lifeless. E.g. deep sea bacteria in hydrothermal vents Alternative env where life could have originated are warm ponds, ocean beaches, water under frozen ice sheets, kms below earths surface and thermal springs. Also possibly Mars or elsewhere in space brought here by comets or asteroids.

4. The study of present-day organisms increases our understanding of past organisms and environments

4.2.1 Explain the need for scientists to classify organisms Makes it easier to describe and study the enormous diversity of living organisms enable easier communication between scientists understand relationships large number organisms- 1.8mil of different organisms reveal trends, identify new organisms conservations taxonomy science of classifying organisms all scientists must agree

4.2.2 Describe the selection criteria used in different classification systems and discuss the advantages and disadvantages of each system

Biologists do not always agree on criteria that should be used to group organisms. Even highest of classification theres more than one system: (3 kingdoms- Monera, plants and animals) or (5 kingdoms - Monera, Protista, Fungi, plants and animals). Criteria often used for determining similarities and differences in organisms are:

Anatomy (structure) - morphology Most practical- its easily observed in living, dead and fossilised organisms. usually remains constant over life of organism doesnt change according to season, age etc

Physiology (functioning) Plants grouped according to both structure and method of production where classification of animals is largely based on structure.

Behaviour Can be observed first hand and is most common criteria for biologists

Biochemistry (functioning at a molecular level) when cannot be easily identified by morphology alone

Genetics and molecular structure identify evolutionary relationships DNA (mutate at a predictable and constant rate. Used to date events e.g. when organism diverges from a common ancestor) and protein analyse used to reveal relationships that cant be viewed in any other way.

4.2.3 Explain how levels of organisation in a hierarchical system assist classification Provides framework that reflects level of similarity or difference between organisms in a systematic way. Determine what stage they diverged Hierarchy allows us to retrieve and store info

Classification over time 18th cent: Carolus Linnaeus divided world into animal (life, sensation & locomotion), vegetable (life) and mineral (concrete bodies without life, etc). Included non-living things. Also devised binomial system for naming organisms at genus and species level. 1866: Ernst Haekel- 3 kingdom system- Animalia, Plantae (also fungi) and Protista (everything else). 1950s: electron microscope- prokaryotic cells placed in separate kingdom- Monera. 1967: R.H. Whittaker- fungi as separate eukaryotic kingdom. Also proposed 5 kingdoms. Eukaryotes organised into Animalia, Plantae, fungi and Protista. 1977: Woese- radical new scheme- used molecular characteristics instead of morphology for classification of living things.

5 kingdoms are: ANIMALIA Unicellular/multicellular organisms do not contain chlorophyll/make own food (heterotrophic) Eukaryotic cells, no cell wall PLANTAE Contain chlorophyll/other pigment can make own food (photosynthetic autotrophs) Eukaryotic cells, rigid cell wall containing cellulose FUNGI Eukaryotic cells, cell wall containing chitin, do not contain chlorophyll (heterotrophic) Some unicellular (yeasts), others multicellular Typically form from a spore produced by one parent PROTISTA Multicellular/unicellular eukaryotic organisms (protozoans, some algae) Can be photosynthetic autotrophs or heterotrophic MONERA Single celled, prokaryotic organisms (bacteria, cyanobacteria) Some may form chains of cells Reproduce by binary fission (one cell splits in two) Can be autotrophic (photo/chemosynthetic) or heterotrophic

KingdomAnimaliaHeterotrophKing

PhylumChordate, vertebrate/invertebrateBackbonePhillip

ClassMammalHair/suckle youngComes

OrderPrimateForward eyes/opposable thumbsOver

FamilyHominidNo tailFor

GenusHomoUpright walkGood

SpeciesSapienLarge forebrainSex

4.2.4 Discuss, using examples, the impact of changes in technology on the development and revision of biological classification systems Light microscope living cells made up of cells Electron microscope internal structure of cells in more detail, study difference between eukaryotic/prokaryotic cells Can now make comparisons at molecular level Biochemical techniques identify amino acid sequences in proteins/bases in DNA Sequence data held in databases accessible to scientists worldwide now used as tools in classification/help to accurately chart evolutionary relationships

Examples: DNA sequencing has revealed tree shrews not related to primates. They have been reclassified as the only member of a new group, Scandentia. Woeses discovery of 2 major groups within Monera are based on molecular rather than anatomical structure 1988: new classification of flowering plants proposed by international group of botanists- using traditional morphological features as well as gene sequences revealed by new techniques. This new system suggested some evolutionary relationships previously unknown. E.g. AUS plant family Proteaceae (includes grevilleas, banksias and waratahs) was shown to be related to northern hemisphere family Platanaceae (plane trees). Also family Epacridaceae (AUS native heaths) should be placed in the family Ericaceae (includes azaleas, rhododendrons and Scottish heather).

4.2.5 Describe the main features of the binomial system in naming organisms and relate these to the concepts of genus and species The binomial aspect of this system means that each organism is given two names- a generic name (genus) and a specific name (species). Binomial system= binary nomenclature This system allows scientists to speak the same language when referring to living things and avoids confusion of multiple common names that may differ based on religion, culture or native language. Scientific name (in italics) Genus is capitalised and species name is in lower case. Homo sapiens (humans)

1. GENUS (pl genera) generic Taxonomic classification lower than family and higher than species. So more general. 2. SPECIES specific epithet second part of scientific name refers to one species within a genus species: group organisms w similar anatomical characteristics; successfully interbreed viable offspring A mule isnt because its an infertile hybrid of a male donkey and female horse.

4.2.6 Identify and discuss the difficulties experienced in classifying extinct organisms

difficult to classify extinct organisms becoming impossible to study biochemistry/fine cell structure studying modern organisms not always guarantee of similar ancestors

4.2.7 Explain how classification of organisms can assist in developing an understanding of present and past life on Earth

On discovering unknown organisms, researchers begin classification by:1. looking for anatomical features that appear to have same function as those found on other species2. determining whether or not similarities are due to an independent evolutionary development or descent from common ancestor then two species probably closely related and should be classified into same/near biological categories Homology: anatomical features of different organisms w similar appearance/function common ancestor bear, bird, human same functional types of bones as common reptilian ancestor homologous structures Homoplasies: non homologous structural similarities between species independent development. The common ancestor did not have the same anatomical structures as its descendants. Homoplastic structures can be the result of parallelism, convergence, analogies or mere chance. Parallelism/parallel evolution: similar evolutionary development in different species lines after divergence from common ancestor that did not have characteristic but did have initial anatomical feature that led to it. Convergence/convergent evolution: the development of a similar anatomical feature in distinct species lines after divergence from a common ancestor that did not have the initial trait that led to it. Common ancestor= more distant in time. There are a number of Australian marsupials that are striking examples of convergent evolution with placental mammals elsewhere. Both parallelism and convergence are thought to be due to separate species lines experiencing the same kinds of natural selection pressures.

Analogy: anatomical features that have the same form/function in different species that have no known common ancestor. E.g. wings of butterflys and birds are analogous structure because theyre superficially similar in shape and function. Although wings are quite different on inside- birds have bones where butterflys had no bones at all and are kept rigid mostly through flying pressure. Analogies may be due to homologies or Homoplasies but the common ancestor if any is unknown.

Problems in classifying Organisms The listing system makes it appear that the species characteristics are fixed forever but thats not the case because evolution has always been happening and always will change. Within a species, each organism is genetically and physically diverse. Determining specific characteristics that actually distinguish from all other types of organisms. Not obvious what most important traits are. Splitter approach: defines new species based on minor differences between organisms. Lumber approach: ignores minor differences and emphasises major similarities. Results in fewer species being defined. Breeding experiments if 2 organisms can mate and produce fertile offspring theyre members of same species. Although must be careful because members of closely related species can reproduce together and small fraction may be fertile. E.g. mules about 1 out of 10,000 are fertile. Breeding experiments: rarely undertaken because of practical difficulties- time consuming and wild animals do not always cooperate. Comparisons of DNA sequences- commonly used as aid of distinguishing species. It tells us that they might be closely related but not if theyre the same species. Therefore were left with morphological characteristics as most commonly used criteria for identifying species differences. Linnaean scheme for classification of living things lumps organisms together based on presumed homologies. Assumption: the more homologies 2 organisms share the closer they must be in evolutionary distance. Hierarchical system highest category consists of all living things and lowest is a single species. Species- has heaps of sub categories.

Cladistics they make a distinction between derived and primitive traits when they evaluate importance of homologies for determining placement of organisms within the Linnaean classification system. Derived traits are those that have changed from the ancestral form and/or function. E.g. the foot of a modern horse. Its distant early mammal ancestor had 5 digits. The bones of these digits have been largely fused together in horses giving them essentially only one toe with a hoof. In contrast, primates have retained the primitive characteristic of having 5 digits on the ends of their hands and feet. Animals sharing a great many homologies that were recently derived, rather than only ancestral, are more likely to have a recent common ancestor. This assumption is the basis of the approach to classifying known as cladistics.

4.3.1 Perform a first-hand investigation and gather information to construct and use simple dichotomous keys and show how they can be used to identify a range of plants and animals using live and preserved specimens, photographs or diagrams of plants and animals

A dichotomous key can be used to help identify plants and animals. It offers 2 possibilities at each step (dichotomy). With a dichotomous key: An organism can be keyed out or identified using the key An organism can be described by working backwards through the key

When constructing the following ideas need to be followed: The features used to separate organisms must be clear and accurate e.g. use 3 pairs of legs rather than many legs Features need to be observable (structural usually) Features cannot change. Some trees have juvenile leaves which are different from adult Useful to have labelled diagram of observable features with key