Change Over Time

7. Define a fossil and outline how they are formed.

ossils are the record of life preserved in monuments of stone. Almost all living organisms can leave fossils, but usually only the hard parts of plants and animals fossilize. Soft internal organs, muscle, and skin rapidly decay and are rarely preserved, but the bones and shells of animals are good candidates for fossilization. Almost no fossil record exists for soft organisms such as jellyfish and worms. Dinosaur Track Dinosaur Track. [ more ] Raptor Eggs Raptor Dinosaur Egg Fossils. [ more ] Copralite Copralite - Dinosaur Dung. [ more ] Swimming Tracks Dinosaur swimming tracks. [ more ] Fossils include the footprints of animals left in soft mud, later to be buried, and turned into stone. In some areas herds of fossilized tracks have been found such as at the Johnson farm in St. George, Utah. One of the more exotic fossils is that of swimming tracks made by animals as they brush against the mud and silt floors of an ocean or lake. Under certain circumstances fossils of animal dung, eggs, and even complete nests with eggs have been preserved in stone. Spider in Amber A spider entombed in amber. [ more ] Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt. Soft tissues quickly decompose leaving the hard bones or shells behind. Over time sediment builds over the top and hardens into rock. As the encased bones decay, minerals seep in replacing the organic material cell by cell in a process called "petrification." Alternatively the bones may completely decay leaving a cast of the organism. The void left behind may then fill with minerals making a stone replica of the organism. Fossils can form in unusual ways. Small bugs or insects can become trapped in tree sap. Eventually the sap hardens and forms the semiprecious material called amber. In some pieces of amber the entombed remains of organisms can be found. Volcanic eruptions can form fossils when animals get trapped in the hot ash flows. In this case, the fossil is a hole in the shape of the animal. By far the most common fossil remains are those of shelled invertebrate sea loving creatures such as snails, corrals, and clams. These make up most of the fossil record. Plants can leave fossils. In fact coal is the fossil record of whole forests; however, individual plant structures usually do not survive as the plant materials are compressed to less than one hundredth of their original size. Fossils of land animals are scarcer than those of plants. In order to become fossilized, animals must die in a watery environment and become buried in the mud and silt. Because of this requirement most land creatures never get the chance to become fossilized unless they die next to a lake or stream. Indeed there may be whole species of land animals in which no fossil record has been discovered. We may never know how many and diverse these animals were.

14. Explain the process of natural selection and its relevance to the theory of evolution, listing a number of possible selective agents.

Darwin and Wallace suggested that evolution occurs by natural selection. According to this theory, organisms that are well suited to their environment are more likely to survive long enough to produce offspring and also have a better chance of having a large number of offspring. Organisms that are not well suited to their environment are out-competed, die young and produce few or no offspring. Variation There are variations or differences between members of a species. In a rainforest some tree ferns grow faster and produce more spores than others. In a herd of sea lions certain males will grow larger and have deeper voices. Some sharks will be faster and have a better sense of smell than others. Butterflies of the same species may have slightly different patterns and colours on their wings. Importantly, certain variations give an advantage. The faster sharks are more likely to catch their prey and thus be well fed. The larger sea lions will win fights against other males and thus the right to mate with more females. The faster growing tree ferns will not be shaded by other ferns and will have sufficient light to continue to grow. The butterfly with the pattern that offers the best camouflage is less likely to be eaten before it can mate and lay eggs. camouflage Camouflage reduces this butterfly's chance of being eaten before she lays her eggs. Individuals with favourable variations are more likely to survive longer and produce more offspring. Those that possess unfavourable variations are likely to die having produced few or no offspring. A bird born with a long thin beak when hard seeds are the only food available will break its beak trying to eat the seeds and die of starvation before it can reproduce. A peacock with a small drab tail will fail to attract a mate and will not have an opportunity to produce offspring. A bright red caterpillar crawling in green vegetation is likely to be eaten by a bird and never go on to become a butterfly and reproduce. Selection The different living (biotic) and non-living (abiotic) selective agents in an environment select for survival those individuals who are best at surviving and obtaining what they need. In a rainforest the low availability of light is a selecting agent. Plants that can get access to light survive. Predators can act as selecting agents. Individuals that can outrun or hide from the predator live on and reproduce. Chemicals and disease-causing organisms can also be selective agents. When DDT was first used as an insecticide it killed most insects. A few were naturally resistant to DDT. They survived, reproduced and passed on their natural resistance to their offspring. The process was repeated over many generations and now many insects are resistant to DDT. Myxomatosis is a virus that, when first released, was deadly to most rabbits. It acted as a selecting agent. Those rabbits that did not die reproduced and passed on the resistance to the virus. The proportion of rabbits that are not killed by myxomatosis has increased. Survival of the fittest Darwin's theory of evolution by natural selection is often described as survival of the fittest. 'Fittest' in this instance does not mean those who can do the most sit-ups! It means that in a population with a range of features, those who are the best 'fit' to their environment are selected, survive and breed more successfully than their rivals. Selection at work The Galapagos finches (see Darwin's finches) provide an excellent example of natural selection. Darwin proposed that an ancestral species of finch had spread to a number of islands. In each place, different sources of food were available, and those individuals who had beaks that were better suited to obtain the local food survived and reproduced more successfully than others. The offspring of such birds also had these beaks and were more successful, until eventually the whole population of finches occupying that niche showed that adaptation. Over many generations, each group evolved to have a beak suited to its particular food.

8. Identify the conditions necessary for fossilisation to occur.

Fossilisation is a rare process, the vast majority of deceased organisms disappear without leaving a trace In order for fossilisation to occur, the following conditions are required: Hard body parts (bones, teeth, shells) - soft body parts will not fossilise, but may leave behind trace evidence (e.g. imprints) Preservation of remains (protection against scavenging, erosion and environmental damage) High pressure to promote mineralisation of remains (i.e. turn hard body parts into fossilised rocks) Anoxic (low oxygen) conditions to protect against oxygen damage and prevent decomposition by saprotrophs The stages of fossilisation generally occur as follows: 1. Death and decay - Soft body parts are decomposed or scavenged, leaving only the hard body remains 2. Deposition - The hard remains are rapidly covered with silt and sand, and over time more layers continue to build 3. Permineralisation - Pressure from the covering layers of dirt/rock cause the hard organic material to be replaced by minerals 4. Erosion / exposure - Movement of earth plates may displace the fossil and return it to the surface for discovery

3. Revise the following terms and concepts to help determine the geological history of an area: geological time, radioactive dating, index fossil, cross-cutting.

Geological time: the succession of eras, periods, and epochs as considered in historical geology. Radioactive Dating: any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product. Index fossil: a widely distributed fossil, of narrow range in time, regarded as characteristic of a given geological formation, used especially in determining the age of related formations. Cross-cutting: the technique of intercutting a scene with portions of another scene, especially to heighten suspense by showing simultaneous action.

16. Consider some population studies which demonstrate natural selection (resistance studies - myxomatosis, bacteria; computer simulation of the peppered moth, evolution of rock mice).

Rabbits were introduced to Australia in 1859 by a wealthy Victorian grazier keen on the sport of hunting. Hunters, however, could not keep up with the extraordinary rate at which the animals multiplied and soon millions of rabbits were competing with Australia's livestock for feed and were damaging the environment. The initial release of the myxoma virus led to a dramatic reduction of Australia's rabbit population. Within two years of the virus's release in 1950 Australia's wool and meat production recovered from the rabbit onslaught to the tune of $68 million. In the end the rabbit calicivirus did the job it was predicted and intended to do, without any adverse impacts and with major benefits to primary production and native ecology. They did, however, say that it might be possible to use the disease with some promise of temporary control of a rabbit population, but only under special conditions, including the presence of insect vectors in abundance and the absence of predatory animals Renewed calls for the use of myxomatosis By 1949 the situation was desperate. The traditional methods of control were quite inadequate. New and radical measures were called for. Dame Jean MacNamara once more took up her advocacy of using myxomatosis campaigning vigorously in the Melbourne-published Stock and Land and the Herald. The disease tends to be confined to the river flats and frontage country. In the Corowa ' Rutherglen area, where the most detailed observations have been carried out, there is a very obvious and clear relation between the activity of the disease and proximity of weedy lagoons. These are the breeding places of the dusk-biting Culex annulirostris mosquito. Along the river flats the stench of death lies heavy these hot days ' myxomatosis is striking at the millions of rabbits that swarm along the lagoons and river reaches. Fenner, who had already established an international reputation for his work on Ectromelia or mousepox (smallpox of mice) went on to make major contributions to myxoma virus research ranging from epidemiology to molecular genetics. He published detailed findings on the pathogenesis, morphology, classification, relationship with other poxviruses, immunity both passive immunity and active immunity. As Frank Fenner recalled in the interview with Max Blythe: Antibiotic resistance Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. It is a specific type of drug resistance. Antibiotic resistance evolves naturally via natural selection through random mutation, but it could also be engineered by applying an evolutionary stress on a population. Once such a gene is generated, bacteria can then transfer the genetic information in a horizontal fashion (between individuals) by plasmid exchange. If a bacterium carries several resistance genes, it is called multiresistant or, informally, a superbug. Causes Antibiotic resistance can also be introduced artificially into a microorganism through transformation protocols. This can be a useful way of implanting artificial genes into the microorganism. Antibiotic resistance is a consequence of evolution via natural selection. The antibiotic action is an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce. Early treatment may reduce the risk of death from invasive group A streptococcal disease. However, even the best medical care does not prevent death in every case. For those with very severe illness, supportive care in an intensive care unit may be needed. For persons with necrotizing fasciitis, surgery often is needed to remove damaged tissue. Strains of S. pyogenes resistant to macrolide antibiotics have emerged, however all strains remain uniformly sensitive to penicillin. Resistance of Streptococcus pneumoniae to penicillin and other beta-lactams is increasing worldwide. The major mechanism of resistance involves the introduction of mutations in genes encoding penicillin-binding proteins. Selective pressure is thought to play an important role, and use of beta-lactam antibiotics has been implicated as a risk factor for infection and colonization. Rock-Mice Rock pocket mice live in the deserts of the American southwest. Ancestral pocket mice had light-colored coats that blended in with the region's rocks and sandy soil, keeping the mice hidden from their owl predators. Starting about 1.7 million years ago, a series of volcanic eruptions spewed out wide trails of black lava that wove right through the middle of pocket-mouse territory. Today there are two forms of pocket mice: light-colored mice that live on sandy soil, and dark-colored mice that live on black lava rock. The dark mice came about through the process of evolution. Naturally occurring mutations to coat-color genes produced mice with dark fur. On black rocks, dark mice had an advantage over light mice: they were better-hidden from predators. They survived and reproduced, passing their dark-fur genes to their offspring, which still survive today. Once a favorable variation occurs, it can quickly become the major form in a population. Each year, mice produce more offspring than will reach adulthood. Thanks to natural selection, the offspring with favorable characteristics are more likely to survive and reproduce. MISCONCEPTION Recessive alleles are weak and they will eventually disappear. REALITY Natural selection maintains favorable alleles regardless of whether they are dominant or recessive. Even when they convey no selective advantage or disadvantage, recessive alleles are maintained in a population.

4. 3 main rock types and brief definitions (igneous, sedimentary and metamorphic)

Sedimentary Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Gradually, the sediment accumulates in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils. Examples of this rock type include conglomerate and limestone. Metamorphic Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that occurs due to intense heat and pressure (squeezing). The rocks that result from these processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing slowly over time, on their surface. Examples of this rock type include gneiss and marble. Igneous Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.

1. Identify the estimated age of the Earth

Since the planet Earth doesn't have a birth certificate to record its formation, scientists have spent hundreds of years struggling to determine the age of the planet. By dating the rocks in the ever-changing crust, as well as neighbors such as the moon and visiting meteorites, scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.

13. Discuss the evidence that suggests present day organisms have evolved from organisms of the past, including: - Fossil Evidence - Comparative anatomy - Comparing embryos - DNA studies

The fossil record The fossil record supports the theory of evolution by natural selection. It does this in a number of ways. The fossil record shows that the organisms living on Earth have become increasingly complex over time, and that some species that used to live on Earth have now become extinct. There is also fossil evidence of gradual change occurring in particular groups of organisms. For instance, fossils of ancient horse species have been found. They indicate that over the last 60 million years horses have become taller, their teeth have become adapted for grazing rather than eating soft leaves and fruit, and their feet have changed from having spread out toes to having a single hoof. The horses of 60 million years ago were ideally suited to the environment in which they lived: forests where they could feed on fruit and leaves and where their spread out toes and small size would have made it easier to walk on soft ground and remain inconspicuous. Over time the forests were replaced by open plains. Teeth suited for eating tough grasses became advantageous. Long legs and hoofs gave horses a better chance of getting away from predators. Fossils that show the transition between two groups of organisms have also been found. Such fossils are called transitional forms. The fossilised remains of Archaeopteryx show bird-like features including wings with feathers, but they also show reptilian features including teeth and a long bony tail. This supports the idea that birds evolved from dinosaurs. Comparative anatomy Comparative anatomy involves comparing the structural features of different species or groups of animals. The forearms of mammals, amphibians, reptiles and birds are remarkably similar in structure. Each, however, is used for a different function, such as swimming, walking or flying. The structure of the forearm can be traced back to the fin of a fossilised fish from which amphibians are thought to have evolved. Similarity in characteristics that result from common ancestry is known as homology. Anatomical signs of evolution such as the similar forearms of mammals are called homologous structures. In the diagram below, you can see that each limb has a similar number of bones that are arranged in the same basic pattern. Even though their functions may be different, the similarity of basic structure still exists. Homologous structures should not be confused with analogous structures. Unrelated species living in similar environments (with similar selection pressures) in different parts of the world often have similar structures. This is an example of convergent evolution. The fins of a dolphin and a shark, or the wings of a bat and a butterfly, are analogous structures: they perform the same role but have different evolutionary origins. Comparative embryology Organisms that go through similar stages in their embryonic development are believed to be closely related. During the early stages of development, the human embryo and the embryos of other animals appear to be quite similar. The embryos of fish, amphibians, reptiles, birds and mammals all initially have gill slits. As the embryos develop further, the gill slits disappear in all but fish. It is thought that gill slits were a characteristic that all these animals once shared with a common ancestor. Molecular biology The evolutionary relationships among species can also be reflected in their DNA and proteins. The closer the match in the DNA sequences, the more recent their common ancestor and hence the more closely they are related. You are more closely related to your brothers or sisters than to your cousins, who in turn are more closely related to you than your classmates. So your DNA is more similar to your siblings' DNA than to your cousins' DNA. Likewise, humans and chimpanzees have very similar DNA, compared to that of humans and ferns. DNA hybridisation is a technique that can be used to compare the DNA in different species to determine how closely related they are.

5. Analyse the different parts of the electromagnetic spectrum that are used to gather information about the universe, including visible light.

When you think of light, you probably think of what your eyes can see. But the light to which our eyes are sensitive is just the beginning; it is a sliver of the total amount of light that surrounds us. The electromagnetic spectrum is the term used by scientists to describe the entire range of light that exists. From radio waves to gamma rays, most of the light in the universe is, in fact, invisible to us! Light is a wave of alternating electric and magnetic fields. The propagation of light isn't much different than waves crossing an ocean. Like any other wave, light has a few fundamental properties that describe it. One is its frequency, measured in Hertz, which counts the number of waves that pass by a point in one second. Another closely related property is wavelength: the distance from the peak of one wave to the peak of the next. These two attributes are inversely related. The larger the frequency, the smaller the wavelength - and vice versa. You can remember the order of the colors in the visible spectrum with the mnemonic ROY G BV. Image via University of Tennessee. The electromagnetic waves your eyes detect - visible light - oscillates between 400 and 790 terahertz (THz). That's several hundred trillion times a second. The wavelengths are roughly the size of a large virus: 390 - 750 nanometers (1 nanometer = 1 billionth of a meter). Our brain interprets the various wavelengths of light as different colors. Red has the longest wavelength, and violet the shortest. When we pass sunlight through a prism, we see that it's actually composed of many wavelengths of light. The prism creates a rainbow by redirecting each wavelength out a slightly different angle. The electromagnetic spectrum The entire electromagnetic spectrum is much more than just visible light. It encompasses of range of wavelengths of energy that our human eyes can't see. Credit: NASA (via Wikipedia) But light doesn't stop at red or violet. Just like there are sounds we can't hear (but other animals can), there is also an enormous range of light that our eyes can't detect. In general, the longer wavelengths come from the coolest and darkest regions of space. Meanwhile, the shorter wavelengths measure extremely energetic phenomena. Astronomers use the entire electromagnetic spectrum to observe a variety of things. Radio waves and microwaves - the longest wavelengths and lowest energies of light - are used to peer inside dense interstellar clouds and track the motion of cold, dark gas. Radio telescopes have been used to map the structure of our galaxy while microwave telescopes are sensitive to the remnant glow of the Big Bang. Radio map of galaxy M33 This image from the Very Large Baseline Array (VLBA) shows what the galaxy M33 would look like if you could see in radio waves. This image maps atomic hydrogen gas in the galaxy. The different colors map velocities in the gas: red shows gas moving away from us, blue is moving towards us. Credit: NRAO/AUI Infrared telescopes excel at finding cool, dim stars, slicing through interstellar dust bands, and even measuring the temperatures of planets in other solar systems. The wavelengths of infrared light are long enough to navigate through clouds that would otherwise block our view. By using large infrared telescopes, astronomers have been able to peer through the dust lanes of the Milky Way into the core of our galaxy. Infrared image of the galactic center This image from the Hubble and Spitzer space telescopes show the central 300 light-years of our Milky Way galaxy, as we would see it if our eyes could see infrared energy. The image reveals massive star clusters and swirling gas clouds. Credit: NASA, ESA, JPL, Q.D. Wang, and S. Stolovy (via Wikipedia) The majority of stars emit most of their electromagnetic energy as visible light, the tiny portion of the spectrum to which our eyes are sensitive. Because wavelength correlates with energy, the color of a star tells us how hot it is: red stars are coolest, blue are hottest. The coldest of stars emit hardly any visible light at all; they can only be seen with infrared telescopes. At wavelengths shorter than violet, we find the ultraviolet, or UV, light. You may be familiar with UV from its ability to give you a sunburn. Astronomers use it to hunt out the most energetic of stars and identify regions of star birth. When viewing distant galaxies with UV telescopes, most of the stars and gas disappear, and all the stellar nurseries flare into view. UV image of spiral galaxy M81 A view of the spiral galaxy M81 in the ultraviolet, made possible by the Galex space observatory. The bright regions show stellar nurseries in the spiral arms. Credit: NASA (via Wikipedia) Beyond UV, comes the highest energies in the electromagnetic spectrum: X-rays and gamma rays. Our atmosphere blocks this light, so astronomers must rely on telescopes in space to see the x-ray and gamma ray universe. X-rays come from exotic neutron stars, the vortex of superheated material spiraling around a black hole, or diffuse clouds of gas in galactic clusters that are heated to many millions of degrees. Meanwhile, gamma rays - the shortest wavelength of light and deadly to humans - unveil violent supernova explosions, cosmic radioactive decay, and even the destruction of antimatter. Gamma ray bursts - the brief flickering of gamma ray light from distant galaxies when a star explodes and creates a black hole - are among the most energetic singular events in the universe. X-ray image of pulsar PSR B1509-58 If you could see in x-rays, over long distances, you'd see this view of the nebula surrounding pulsar PSR B1509-58. This image is from the Chandra telescope. Located 17,000 light-years away, the pulsar is the rapidly spinning remnant of a stellar core left behind after a supernova. Credit: NASA (via Wikipedia) Bottom line: the electromagnetic spectrum describes all the wavelengths of light - both seen and unseen. The shorter the wavelength, the more energetic the light. By using telescopes sensitive to different wavelength ranges of the spectrum, astronomers get a glimpse into a wide variety of objects and phenomena in the universe.

6. Define the theory of evolution, recognizing that it is a very slow process.

The theory of evolution encompasses the well established scientific view that organic life on our planet has changed over long periods of time and continues to change by a process known as natural selection. Charles Darwin, the 19th century naturalist, is given credit for the theory, not because he was the first person to suggest evolution occurs, but because he proposed (in his seminal 1859 text, On the Origin of Species) a mechanism that explains the process of change. The theory of evolution contains two parts, both of which are unnecessarily contentious. The first is the word "theory", which means something slightly different in everyday speech than it does in science. Natural selection In the case of artificial selection, humans choose which traits are desirable. In the case of natural selection, traits that increase the likelihood of survival and reproduction will become more common within a population or species over time. In the past, natural selection has been misrepresented by calling it the survival of the fittest. This statement oversimplifies the mechanism by making it sound like a tautology: the survival of those who survive. The truth is that individuals never survive. What survives is the process for making another individual, and this resides in genes found in populations. Natural selection has more to do with differential reproduction than survival, and what it selects are the genes that code for desirable traits or characteristics. The interaction of individuals with their environment provides a mechanism for sorting out which traits (not which individuals) will be passed on to the next generation. Nature of inheritance The second major component to the theory is the nature of inheritance, which follows the insights made by Gregor Mendel in 1865 and has advanced considerably since then due to our understanding of genes, DNA and the molecular processes of life. When natural selection was first formulated by Darwin, the nature of inheritance was not understood. Our current understanding of inheritance is very sophisticated and includes the precise mechanisms for passing genes on to the next generation, how genes are modified by mutation and how they are shared among sexual species. If we know enough about a gene and its various forms, it is possible to accurately predict the change in the frequency of those genes over time using mathematical formulae from population and evolutionary genetics theory. This alteration of gene frequencies is subtle and does not, at first glance, seem worthy of being called evolution. But it is precisely these small changes at the genetic level that lead to large changes in the organisms that carry them. The sorting of genes affects the fate of populations: populations drift apart and become species, and species diverge to create whole groups of plants or animals that dominate the landscape for millions of years. The intricate details of cellular processes are responsible for the glorious and majestic diversity of life on our planet. The theory of evolution includes large changes over vast periods of time and tiny changes made when one cell divides into two. These processes form a continuum that is the history of life on Earth.

11. Identify evidence that supports the big bang theory - e.g. expansion of the universe, cosmic microwave background radiation and the abundance of light/simple elements).

There are two key pieces of evidence for Big Bang Theory: these are red shift and the Cosmic Microwave Background (CMB) radiation. Red-shift You may have noticed that when an ambulance or police car goes past, its siren is high-pitched as it comes towards you, then becomes low-pitched as it goes away. This effect, where there is a change in frequency and wavelength, is called the Doppler effect. It happens with any wave source that moves relative to an observer. This happens with light too. Our sun contains helium. We know this because there are black lines in the spectrum of the light from the sun, where helium has absorbed light. These lines form the absorption spectrum for helium. spectrum of light with black verticle lines Spectrum of the sun When we look at the spectrum of a distant star, the absorption spectrum is there, but the pattern of lines has moved towards the red end of the spectrum, as you can see below. as before, but the lines are shifted towards the left and right ends of the spectrum Spectrum of a distant star This is called red-shift, a change in frequency of the position of the lines. Astronomers have found that the further from us a star is the more its light is red-shifted. This tells us that distant galaxies are moving away from us, and that the further a galaxy is the faster it is moving away. Since we cannot assume that we have a special place in the universe this is evidence for a generally expanding universe. It suggests that everything is moving away from everything else. The Big Bang Theory says that this expansion started billions of years ago with an explosion. Cosmic Microwave Background radiation Scientists discovered that there are microwaves coming from every direction in space. Big Bang Theory says this is energy created at the beginning of the universe, just after the Big Bang, and that has been travelling through space ever since. A satellite called COBE has mapped the background microwave radiation of the universe as we see it. Big Bang theorists are still working on the interpretation of this evidence. The light from other galaxies is red-shifted. The other galaxies are moving away from us. This evidence can be used to explain both the Big Bang theory and Steady State universe. The further away the galaxy, the more its light is red-shifted. The most likely explanation is that the whole universe is expanding. This supports the theory that the start of the universe could have been from a single explosion. Cosmic Microwave Background (CMB) The relatively uniform background radiation is the remains of energy created just after the Big Bang. Red-shift is used to explain both the Steady State and Big Bang theories of the universe. Cosmic Microwave Background radiation is evidence for the Big Bang theory only. This discovery has led to the Big Bang theory becoming the currently accepted model.

2. Define the principle of superposition of rock layers.

a basic law of geochronology, stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.

12. Identify that the estimated age of the universe

the estimated age of the universe is 13.8 billion years old, and that this number has been determined scientifically.

8. Recall that gravity is an attractive force between all objects with mass.

gravity is an attractive force between all objects with mass.

12. Briefly compare the 5 major eras of the world's evolution.

- Cainozoic Era The Cenozoic Era began 65 Million Years Ago with the extinction of the dinosaurs and continues into the Present. The extinction of the dinosaurs at the end of the Mesozoic Era opened up vast new habitats and environments for early mammals and birds to adapt to and occupy. - Mesozoic era The Mesozoic Era extended from 248 Million to 65 Million Years Ago. The Mesozoic Era was important for the fossil remains of the dinosaurs and other reptiles that lived. However, the Mesozoic Era landscape was also occupied by insects, early mammals, plants such as conifers and ferns, fish, and finally flowering plants and early birds. - Palaeozoiz era The Paleozoic Era is the oldest of the three Eras and dates from 540 Million to 248 Million Years Ago. During the Paleozoic Era multicelled living things acquired hard body parts, bones, vertebral columns, mandibles, and teeth. Common in the Paleozoic Era were trilobites, crinoids, brachiopods, fish, insects, amphibians, and early reptiles. Proterozoic: Life begins in sea Archean: Oldest rocks, Earth curst forms. earth's crust had cooled enough to allow the formation of continents and life started to form. Hadean: Earth forms. The Hadean Eon is characterized by Earth's initial formation—from the accretion of dust and gases and the frequent collisions of larger planetesimals—and by the stabilization of its core and crust and the development of its atmosphere and oceans. Throughout part of the eon, impacts from extraterrestrial bodies released enormous amounts of heat that likely prevented much of the rock from solidifying at the surface. As such, the name of the interval is a reference to Hades, a Greek translation of the Hebrew word for hell.

5. Explain the importance of the following factors in the rock cycle: - The movement of tectonic plates - Erosion agents like water, ice and wind - Deposition of sediments

- The movement of tectonic plates Plate tectonics is the movement of the Earth's crust through convection currents that occur in the mantle. Divergent plate boundaries occur where hot magma rises to the surface, pushing the plates apart. The mid-ocean ridges form at divergent plate boundaries. Convergent plate boundaries occur where cooled rock becomes denser than the rocks around it and sinks back into the mantle. Oceanic trenches, folded mountains and volcanic mountains occur at convergent plate boundaries. Sliding plate boundaries occur when one plate slides past another plate through a twisting force. The San Andreas Fault is an example of a sliding plate boundary. - Erosion agents like water, ice and wind Weathering Weathering is when the elements break down the rock so much that it turns into sediment. Then this sediment is transported by wind or rain to places far from where they were broken apart from. Erosion Erosion is the same as weathering. Both factors happen to all rocks on earth. Heat The factor of heat transforming rocks is when movements in the crust of the Earth cause rocks on the surface to be pulled under the surface. This happens quite frequently. With temperatures rapidly increasing the closer to the inner core you go, most rocks likely melt into magma at around 100 to 200 kilometres within the Earth, where the temperature is hot enough. This process is different from melting, as the rock does not completely changed its physical shape. Pressure Rocks can undergo many different changes within the Earth, without heat. This is because pressure can transform a rock in its solid state before that rock hits boiling point. This factor of the Rock Cycle occurs mainly from the amount of pressure from rocks on top of the changing rock. Both factors, Heat and Pressure, work together underneath Earth's surface to morph rocks from one type to another. This is generally known as Metamorphism, and most likely result in a Metamorphic Rock being produced. Compacting Compacting is the factor of sediment building up in layers over time in lakes, oceans and valleys, and eventually becoming so heavy that the top layers compact the bottom layers into rocks. The sediment for this process is found through rocks that have been weathered down into sediment. When the sediment accumulates in lakes, oceans and valleys, it begins to accumulate in layers. These layers, over time, end up putting weight on the layers and material beneath them. Over a long period of time, this compacted material begins to form into rock. Cooling Cooling is when magma from in the earth starts to turn back into rock. The rock that is formed from the process of cooling magma is Igneous Rock, as Igneous is the only rock formed from magma. Fun fact: Only quickly cooled magma creates igneous rocks, slowly cooled magma creates another type of rocks. - Deposition of sediments Under natural conditions, the pressure created by the weight of the younger deposits compacts the older, buried sediments. As groundwater moves through these sediments, minerals like calcite and silica precipitate out of the water and coat the sediment grains. These precipitants fill in the pore spaces between grains and act as cement, gluing individual grains together. The compaction and cementation of sediments creates sedimentary rocks like sandstone and shale, which are forming right now in places like the very bottom of the Mississippi delta. Because deposition of sediments often happens in seasonal or annual cycles, we often see layers preserved in sedimentary rocks when they are exposed (Figure 5). In order for us to see sedimentary rocks, however, they need to be uplifted and exposed by erosion. Most uplift happens along plate boundaries where two plates are moving towards each other and causing compression. As a result, we see sedimentary rocks that contain fossils of marine organisms (and therefore must have been deposited on the ocean floor) exposed high up in the Himalaya Mountains - this is where the Indian plate is running into the Eurasian plate.

11. Compare diagrams of rock layers to deduce the relative age of fossils (stratigraphy)

A geological cross-section is a section of the crust. These are useful as they can be used to reconstruct the geological history of an area. The sequence of rocks tells the order in which things happened and fossils in the rocks can be dated to tell when it all happened. Fossils are found in sedimentary rock. Sedimentary rock forms from layers of sediments that have built up over time and have become cemented (stuck together). The older layers of sediments were laid down first, so if we look at a cross-section of sedimentary rock the older rock layers are usually on the bottom and the younger rock layers are at the top. If any living thing was trapped in the rock layer at the time it was laid down, there is a chance it may have been fossilised. It would therefore be approximately the same age as the rock that surrounds it. This can help us work out the relative age of the fossil. This method for dating fossils does need to be used with care, however, as the plates in which the rocks lie are still moving. It is possible that a layer (or layers) containing fossils could have been thrust upwards by a sideways force to form a fold, or broken and moved apart in opposite vertical directions to form a fault. Steno first proposed that if a rock contained the fossils of marine animals, the rock was formed from sediments that were deposited on the seafloor. These rocks were then uplifted to become mountains. Based on those assumptions, Steno made a remarkable series of conjectures that are now known as Steno's Laws. Original Horizontality Because sediments are deposited under water, they will form flat, horizontal layers (Figure 11.11). If a sedimentary rock is found tilted, the layer was tilted after it was formed. Figure 11.11: Sedimentary layers that have been deposited horizontally. Lateral Continuity Sediments were deposited in continuous sheets that spanned the body of water that they were deposited in. When a valley cuts through sedimentary layers, it can be assumed that the rocks on either side of the valley were originally continuous. Superposition Sedimentary rocks are deposited one on top of another. Therefore, the youngest layers are found at the top, and the oldest layers are found at the bottom of the sequence. Cross-Cutting Relationships A rock formation or surface that cuts across other rock layers is younger than the rock layers it disturbs. For example, if an igneous intrusion goes through a series of metamorphic rocks, the intrusion must be younger than the metamorphic rocks that it cuts through (Figure 11.12). Matching Rock Layers Superposition and cross-cutting are helpful when rocks are touching one another, but are useless when rocks are kilometers or even continents apart. Three kinds of clues help geologists match rock layers across great distances. The first is the fact that some sedimentary rock formations span vast distances, recognizable across large regions. For example, the Pierre Shale formation can be recognized across the Great Plains, from New Mexico to North Dakota. The famous White Cliffs of Dover in southwest England can be matched to similar white cliffs in Denmark and Germany. A second clue could be the presence of a key bed, or a particularly distinctive layer of rock that can be recognized across a large area. Volcanic ash flows are often useful as key beds because they are widespread and easy to identify. Probably the most famous example of a key bed is a layer of clay found at the boundary between the Cretaceous Period and the Tertiary Period, the time that the dinosaurs went extinct (Figure 11.16). This thin layer of sediment, only a few centimeters thick, contains a high concentration of the element iridium. Iridium is rare on Earth but common in asteroids. In 1980, a team of scientists led by Luis Alvarez and his son Walter proposed that a huge asteroid struck Earth about 66 million years ago, causing forest fires, acid rain, and climate change that wiped out the dinosaurs.

3. Identify the common stages in the life cycle of stars.

All stars begin life in the same way. A cloud of dust and gas, also known as a nebula, becomes a protostar, which goes on to become a main sequence star. Following this, stars develop in different ways depending on their size. Stars that are a similar size to the Sun follow the left hand path: red giant star -> white dwarf -> black dwarf Stars that are far greater in mass than the Sun follow the right hand path: red super giant star \rightarrow supernova \rightarrow neutron star, or a black hole (depending on size) A nebula A star forms from massive clouds of dust and gas in space, also known as a nebula. Nebulae are mostly composed of hydrogen. Gravity begins to pull the dust and gas together. Protostar As the mass falls together it gets hot. A star is formed when it is hot enough for the hydrogen nuclei to fuse together to make helium. The fusion process releases energy, which keeps the core of the star hot. Main sequence star During this stable phase in the life of a star, the force of gravity holding the star together is balanced by higher pressure due to the high temperatures. The Sun is at this stable phase in its life. Red giant star When all the hydrogen has been used up in the fusion process, larger nuclei begin to form and the star may expand to become a red giant. White dwarf When all the nuclear reactions are over, a small star like the Sun may begin to contract under the pull of gravity. In this instance, the star becomes a white dwarf which fades and changes colour as it cools. Supernova A larger star with more mass will go on making nuclear reactions, getting hotter and expanding until it explodes as a supernova. An exploding supernova throws hot gas into space. Neutron star or black hole Depending on the mass at the start of its life, a supernova will leave behind either a neutron star or a black hole.

9. Describe the relationship between an object's mass and gravity.

An object with twice as much mass will exert twice as much gravitational pull on other objects. The gravitational force increases as the size of an object increases. On the other hand, the strength of gravity is inversely related to the square of the distance between two objects.

15. Explain the importance of mutation to natural selection.

As you saw in the previous section, mutations are a random and constant process. As mutations occur, natural selection decides which mutations will live on and which ones will die out. If the mutation is harmful, the mutated organism has a much decreased chance of surviving and reproducing. If the mutation is beneficial, the mutated organism survives to reproduce, and the mutation gets passed on to its offspring. In this way, natural selection guides the evolutionary process to incorporate only the good mutations into the species, and expunge the bad mutations. Natural selection "chose" this trait as favorable. In successive generations, further mutations placed the nose farther back on the head because the whales with this mutation were more likely to reproduce and pass on their altered DNA. Eventually, the whale's nose reached the position we see today. Natural selection selects those genetic mutations that make the organism most suited to its environment and therefore more likely to survive and reproduce. In this way, animals of the same species who end up in different environments can evolve in completely different ways.

6. Identify some of the equipment used to gather information about the universe.

Astronomers use various types of equipment based on the portion of the E-M Band to be observed. Telescopes and radio dishes are used from the surface of the Earth to study visible light, near infrared light, and radio waves. Attached to these telescopes are various tools like special made CCD cameras, a wide variety of filters, photometers and spectrometers. These various instruments are designed to record what we normally cannot see with our eyes. From space, astronomers use special telescopes to study X-ray and gamma ray emissions. In addition, space based telescopes like the Hubble Space Telescope can peer deep into the Universe without atmospheric interference. Other specialized instruments are also finding their way into main stream astronomy, like neutrino detectors deep underground and gravity wave detectors. Telescopes and radio dishes are also pairing up to create interferometers to increase the resolution capabilities. Radio dishes are often found as members of a group like the VLA in Socorro, New Mexico. The following sections will look into the more common pieces of equipment used today to gather valuable data. Optical Telescopes The now-indispensable optical telescope instrument was pioneered by Galileo Galilei in 1609, although others had created similar tools by then. He used his "three-powered spyglass" to discover the four main moons of Jupiter as well as numerous previously unknown features of the moon. Over the centuries, telescopes evolved from simple hand-held objects to mounted beasts on mountain-top observatories and finally to telescopes orbiting the earth in outer space, which introduced the advantage of eliminating atmospheric distortion of the visual field. Today's telescopes are capable of seeing almost to the edge of the known universe, giving humanity a glimpse back in time many billions of years. Radio Telescopes In contrast to conventional telescopes, radio telescopes detect and assess celestial objects using not the light waves they emit but their radio waves. Rather than being tubular, these telescopes are built in the form of parabolic dishes, and are often arranged in arrays. Only as a result of these telescopes have objects such as pulsars and quasars have become a part of the astronomical lexicon. While visible objects such as stars and galaxies emit radio waves as well as light waves, others can only be detected by radio telescopes. SCIENCING VIDEO VAULT Spectroscopes Spectroscopy is the study of different wavelengths of light. Many of these wavelengths are visible to the human eye as distinct colors; a prism, for example, separates plain light into different spectra. The introduction of spectroscopy into astronomy gave birth to the science of astrophysics, for it allows for an exhaustive analysis of objects such as stars, which mere visualization does not. For example, astronomers can now place stars into different stellar classes based on their distinct spectra. Each chemical element has its own "signature" spectral pattern, so it's possible to analyze the composition of a star from many thousands of light-years away provided astronomers can collect its light. Star Charts Without telescopes, binoculars and other instruments of observation, star charts would not exist as they do today. But star charts, in addition to serving as guides to the sky for astronomers and mere astronomy buffs, have served as important tools in non-astronomical areas of life, such as nautical navigation. The Internet and other modern media have made star charts -- many of them interactive -- all but ubiquitous. But star charts have been around in some form for many millennia. Indeed, in 1979, archaeologists discovered an ivory tablet dated at over 32,500 years old and believed to depict, among other things, the constellation Orion.

17. Relate the unique fauna and flora of Australia to its isolation after Gondwanaland broke up.

Australia is a land like no other, with about one million different native species. More than 80 per cent of the country's flowering plants, mammals, reptiles and frogs are unique to Australia, along with most of its freshwater fish and almost half of its birds. Australia's geographic isolation has meant that much of its flora and fauna is very different from species in other parts of the world. Most are found nowhere else. However, some closely related species are found on the continents which once made up the ancient southern supercontinent Gondwana. Covered in rainforest and ferns 300 million years ago, Gondwana included South America, Africa, India and Antarctica. Most of Australia's flora and fauna have their origins in Gondwana, which broke up about 140 million years ago. Australia separated from Antarctica 50 million years ago. As it drifted away from the southern polar region, its climate became warmer and drier and new species of plants and animals evolved and came to dominate the landscape. Flora Most of the Gondwanan forests were replaced by tough-leaved open forests of eucalypts and acacias. Some isolated remnants of the ancient Gondwanan forests remain. These include the cool and warm temperate rainforests of Tasmania and eastern Australia and the dry rainforests or scrub forests of northern Australia. These forests have high conservation values. Australia has over 1000 species of acacia, which Australians call 'wattle', and around 2800 species in the Myrtaceaefamily, which includes eucalypts (or gum trees) and melaleucas. Wildflowers, including everlasting daisies, turn the arid and savanna grassland areas of Australia into carpets of colour after rain. Native forests are limited to wetter coastal districts, and rainforests are found mainly in Queensland. The high diversity of flora includes large numbers of species in ecologically significant genera such as Acacia,Eucalyptus, Melaleuca, Grevillea and Allocasuarina. Acacias tend to dominate in drier inland parts of Australia, while eucalypts dominate in wetter parts. Australia's unique flora includes the Proteaceae family of Banksia, Dryandra,Grevillea, Hakea and Telopea (waratah). The most common vegetation types today are those that have adapted to arid conditions, where the land has not been cleared for agriculture. The dominant type of vegetation in Australia—23 per cent—is the hummock grasslands in Western Australia, South Australia and the Northern Territory. In the east eucalypt woodlands are prevalent, and in the west there are Acacia forests, woodlands and shrublands. Tussock grasslands are found largely in Queensland. Fauna. In Australia there are more than 378 species of mammals, 828 species of birds, 300 species of lizards, 140 species of snakes and two species of crocodiles. Of the mammals, almost half are marsupials. The rest are either placental mammals or monotremes. Among Australia's best-known animals are the kangaroo, koala, echidna, dingo, platypus, wallaby and wombat. Australia has more than 140 species of marsupials, including kangaroos, wallabies, koalas, wombats and the Tasmanian Devil, which is now found only in Tasmania. In many rural areas where their populations are high, kangaroos are regarded as pests because they compete with sheep and cattle for scarce pasture and water. Kangaroo harvesting contributes to the sustainability of the Australian environment. The dingo is Australia's native wild dog and its largest carnivorous mammal. In some pastoral areas, dingoes are also regarded as pests due to the threat they pose to sheep and other farm animals. In an effort to keep fertile south-east Australia relatively free of dingoes, the world's largest fence was built, spanning 5320 kilometres from Queensland to South Australia. Australia hosts another unique animal group, the monotremes, which are egg-laying mammals, often referred to as 'living fossils'. The most distinctive is the platypus, a riverdwelling animal with a duck-like bill, a furry body and webbed feet. Isolation has also contributed to the development and survival of unusual birds. These range from tiny honeyeaters to the large, flightless emu, which stands nearly two metres tall. In between is a vast array of waterbirds, seabirds and birds that dwell in open woodlands and forests.

7. Describe some of the difficulties in obtaining information about the universe from Earth.

Ever expanding universe Expansion happens on a very large scale that is very hard to notice from Earth. The larger the universe gets, the more there is to discover and the further away things become. It is hard to even comprehend the sheer size of the universe already, and its still getting better. Distance Things in the universe are very far away, so it is very hard to get detailed imaging of places in space even with large telescopes. Astronomers can get quite good picture of the Sun and neighboring planets, but when they starting exploring other galaxies, it becomes harder and harder. Blocked Radiation Our knowledge of the universe comes mostly from the radiation arriving on the Earth from distant cosmic objects. Only a small fraction of that radiation makes it unimpeded through the atmosphere, that in the visible and radio parts of the spectrum. The Earth's atmosphere weakens most of the rest, letting some infrared radiation through, but absorbing entirely the UV, X-ray and gamma ray radiation. To observe these parts of the spectrum astronomers have to take their telescopes to remote locations, such as high, dry mountain tops or the Antarctic plateau, high-flying airplanes and balloons and even into space with satellite observatories. Atmospheric Distortion The radiation that does penetrate the atmosphere is subject to distortion because of variations in air density and motion. By putting observatories on mountain tops above some of the atmosphere, astronomers improve their chances of a good image, but there will still be limits to how clear the images will be, especially for faint sources. Putting observatories in space, means that they pick up the radiation before it can be distorted by the Earth's atmosphere.

10. Describe using examples how gravity affects the interactions of objects in space.

Gravity is a very important force. Every object in space exerts a gravitational pull on every other, and so gravity influences the paths taken by everything traveling through space. It is the glue that holds together entire galaxies. It keeps planets in orbit. It makes it possible to use human-made satellites and to go to and return from the Moon. It makes planets habitable by trapping gasses and liquids in an atmosphere. It can also cause life-destroying asteroids to crash into planets. Creating Stars Giant molecular clouds made up of gas and dust slowly collapse because of the inward pull of their gravity. When these clouds collapse, they form lots of smaller areas of gas and dust that will eventually collapse as well. When these fragments collapse, they form stars. Because the fragments from the original GMC stay in the same general area, their collapse causes stars to form in clusters. Formation of Planets When a star is born, all of the dust and gas not needed in its formation ends up trapped in the orbit of the star. The dust particles have more mass than the gas so they can begin to concentrate in certain areas where they come in contact with other dust grains. These grains are pulled together by their own gravitational forces and kept in orbit by the gravity of the star. As the collection of grains becomes bigger, other forces also begin to act upon it until a planet forms over a very long period of time.

9. Explain why some life forms are more likely to leave fossils than others.

It is very likely that any organism on Earth will be either eaten by scavengers or decomposed by microorganisms after it dies. Organisms decompose more quickly when they are in contact with oxygen. Most environments exposed to the open air are in contact with plenty of oxygen, so the soft tissues of dead organisms, whether plants or animals, decay quickly. Many, if not most, underwater environments also have a lot of oxygen, since water can dissolve oxygen from the atmosphere. For an organism to become a fossil, it must not decompose or be eaten. This can happen if the organism either lives within or is moved to a place where it can be buried and kept from decaying. When an organism is buried quickly, there is less decay and the better the chance for it to be preserved. The hard parts of organisms, such as bones, shells, and teeth have a better chance of becoming fossils than do softer parts. One reason for this is that scavengers generally do not eat these parts. Hard parts also decay more slowly than soft parts, giving more time for them to be buried.

2. Compare the relative sizes of different objects in the universe (i.e. planets to stars).

On a 1-to-10 billion scale: Sun is the size of a large grapefruit (14 centimeters). Earth is the size of a tip of a ballpoint pen, 15 meters away. Can discuss compressing the scale by another factor of 1 billion, so the galaxy fits on a football field... distance to Alpha Centaur is now just 4 mm, and our solar system sits around the 20-yard line if galactic center is at midfield. The Milky Way has about 100 billion stars. On the same 1-to-10 billion scale... The Milky Way is one of about 100 billion galaxies. 1011 stars/galaxy x 1011 galaxies = 1022 stars It has as many stars as grains of (dry) sand on all Earth's beaches.

1. Recall the definitions of the following astronomical terms: stars, supernovae, planets, moons, gravity, galaxies, light year, nebulae, comet, and asteroid.

Star A massive ball of gas that generates prodigious amounts of energy (including light) from nuclear fusion in its hot, dense core. The Sun is a star. Supernova A star ending its life in a huge explosion. In comparison, a nova is a star that explosively sheds its outer layers without destroying itself. planets a celestial body moving in an elliptical orbit round a star. Moon A moon is defined to be a celestial body that makes an orbit around a planet, including the eight major planets, dwarf planets, and minor planets. A moon may also be referred to as a natural satellite, although to differentiate it from other astronomical bodies orbiting another body, e.g. a planet orbiting a star, the term moon is used exclusively to make a reference to a planet's natural satellite. Gravity the force that attracts a body towards the centre of the earth, or towards any other physical body having mass. Light-year The distance that light (moving at about 186,000 miles per second) travels in one year, or about 6 trillion miles. Nebula Latin for "cloud." Bright nebulas are great clouds of glowing gas, lit up by stars inside or nearby. Dark nebulas are not lit up and are visible only because they block the light of stars behind them. Comet A comet is a "dirty snowball" of ice and rocky debris, typically a few miles across, that orbits the Sun in a long ellipse. When close to the Sun, the warmth evaporates the ice in the nucleus to form a coma (cloud of gas) and a tail. Named for their discoverers, comets sometimes make return visits after as little as a few years or as long as tens of thousands of years. Asteroid (Minor Planet) A solid body orbiting the Sun that consists of metal and rock. Most are only a few miles in diameter and are found between the orbits of Mars and Jupiter, too small and far away to be seen easily in a small telescope. A few venture closer to the Sun and cross Earth's orbit.

4. Identify that nuclear reactions within stars create all the elements larger than hydrogen.

Stars are formed in clouds of gas and dust, known as nebulae. Nuclear reactions at the centre (or core) of stars provides enough energy to make them shine brightly for many years. The exact lifetime of a star depends very much on its size. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. Smaller stars, however, will last for several billion years, because they burn their fuel much more slowly. Nuclear reactions within stars create all the elements larger than hydrogen.

10. Identify that the oldest fossils are very simple organisms (eg bacteria) and fossils of more complex organisms like humans are only found in relatively young rocks.

the oldest fossils are very simple organisms (e.g. bacteria) and fossils of more complex organisms like human are only found in relatively young rocks. Not all fossils are of equal value in dating rocks; the most useful are called index or zone fossils. Ideally, index fossils should be common, readily preserved and easily recognisable. They should have spread rapidly and widely, and for accuracy of dating, they should have evolved rapidly so that individual species existed during only a short interval of time. Very few index fossils meet all of these criteria. Amongst the most important index fossils are graptolites, ammonites, foraminifera, pollen, conodonts and trilobites.