Fossils Lesson 1 PDF

# Lesson 1: Fossils ## How can you study life evolution on the planet Earth? * If you organize a trip to the Geological museum at the River Nile bank in Zahraa El Maady, you will observe the presence of fossils there. * In this lesson, we will study: * Concept of fossils. * Types of fossi...

# Lesson 1: Fossils ## How can you study life evolution on the planet Earth? * If you organize a trip to the Geological museum at the River Nile bank in Zahraa El Maady, you will observe the presence of fossils there. * In this lesson, we will study: * Concept of fossils. * Types of fossils and their formation. * Importance of fossils. ## Concept of fossils * Fossils are considered as an exciting world (a story told by sedimentary rocks), that tell us about the deep past, millions years ago even before the creation of man on the Earth. * **Fossils:** They are traces and remains of old living organisms that are preserved in sedimentary rocks. * **Trace:** It is the traces of an old living organism that indicate its activity during its life. * **Examples:** Worms’ tunnels, Dinosaur’s foot print * **Remains:** They are the traces that indicate the remains of an old living organism after death. * **Examples:** Remains of a shark’s teeth, Remains of a dinosaur’s skull ## Enrichment information * In Latin, the word fossil means something buried in the Earth. * The science, which studies fossils is called "Paleontology". ## Types of fossils * Fossils are classified according to the way of formation (or preservation) into several types, among them are: * **Fossil of a complete body:** It is a type of fossils, which was formed as a result of the rapid burying of the organism as soon as it died in a medium that preserves it from decomposition as snow or amber. * **A complete body fossil:** It is a fossil that keeps the whole shape and all the details of the body of the living organism as a result of its rapid burying as soon as it died in a medium that preserves it from decomposition. * **Examples of a complete body fossil:** * **Mammoth fossil:** * Mammoth (a type of elephants) was extinct by the snow avalanche occurred in Siberia 25000 years ago. * The first mammoth fossil, which was discovered last century, and it keeps the whole shape, hair, flesh and food in its bowel. * **Amber fossil:** * During some old geologic ages, there were common pine trees, which secreted resinous matter that changed after its solidification into amber. * **Amber:** It is the solidified resinous matter, which was secreted by pine trees in old geologic ages. * **Way of formation:** * After its death, mammoth rapidly buried in snow which preserved its body from decomposition. * Insects were covered by the resinous matter which solidified and changed into amber that preserved the bodies of insects buried inside it from decomposition (decaying). * **G.R:** Amber is considered as a suitable medium for the formation of complete body fossils. Because it preserved the bodies of insects inside it from decomposition. * **Mold:** In the opposite figure, the face pattern that carries the internal details of a face mask is known as a mold. * **Before studying the mold fossils, we must know how to make a model of a solid mold.** * **Activity 1 Making a model of a solid mold:** * **Materials and tools:** Plaster of paris, Plastic container, Water, Brush, Metal mold (or a silicon mold), Food oil, Rod for stirring. * **Procedures:** 1. Paint the internal surface of the metal mold (or the silicon mold) with oil using the brush. 2. Mix plaster of paris with water and continue stirring to make suitable mixture. 3. Pour the mixture in the metal mold and wait until the plaster of paris solidifies. 4. Separate the hard mixture from the metal mold. * **Conclusion:** A replica of the internal shape of metal mold is formed and it is known as "Solid mold". * **Solid mold fossil:** It is the replica of the internal details of the structure of an old living organism left after its death in sedimentary rocks. * **Examples of solid mold fossils:** Ammonites fossil, Nummulites fossil, Trilobite fossil * **How is the solid mold fossil formed?** 1. When a snail (or clam) dies, it falls on the sea floor, where its soft parts decompose leaving the shell which is buried in sediments. 2. The sediments fill up the shell cavities and solidify as the time passes. 3. The shell decomposes completely, leaving a solid rock mold carrying the internal details of the snail. * **Real Life application: A Candle mold** Melt a piece of paraffin wax or wax remains in a water bath. Roll a piece of strong paper in the form of a cylinder, then put it in an empty yoghurt can, then pass a thick thread through the cylinder using a needle. Pour the melted wax in the cylinder keeping the thread in the middle all time. Remove the paper from around the wax after its solidification and put the candle in a suitable glass saucer. * **Cast:** To know what is meant by cast, we must carry out the following activity: * **Activity 2 Making a model of a cast:** * **Materials and tools:** Coloured clay, A shell of clam. * **Procedures:** 1. Press on the clay by your hand to make a plane surface. 2. Put the shell on the surface of the clay and press it gently. 3. Remove the shell from the clay. * **Conclusion:** A replica of the original external shell shape is formed and it is known as "Cast". * **Cast fossil:** It is the replica of the external details of the structure of an old living organism left after its death in sedimentary rocks. * **Examples of cast fossils:** Cast of ferns, Fish cast * **Petrified fossils:** They are fossils in which minerals replace the organic matter of an old living organism, after its death, part by part leaving the shape without any change. * **Petrification:** It is the process of conversion of the parts of old living organisms to rocky materials as a result of replacing the organic material of the organism with minerals, part by part. * **Examples of petrified fossils:** Petrified dinosaur’s tooth, Petrified dinosaur’s eggs, Petrified wood * **Petrified woods:** They are fossils which are formed as a result of replacing the wood material of trees with minerals such as silica, part by part, giving us details about the life of an old plant. * **How is the petrified wood formed?** 1. The stems and trunks of trees that are more than 35 million years of age were buried in certain environmental conditions. 2. The minerals replaced the wood material (organic matter) part by part, and this is known as "Petrification". 3. By passing time, the wood changes into rocks, which carry the same details of wood without change. * **G.R.:** Petrified woods are considered as fossils although they look like rocks. Because they give us the details about the life of an old plant. * **Note:** The area of petrified forests in Qattamiya is called the wood mountain G.R. Because it contains petrified woods, which look like rocks. ## Note * In the sedimentary rocks, mold or cast can be formed for an old living organism after its death. * **Comparison between a mold and a trace:** * **Mold:** It is the replica of the internal details of the structure of an old living organism leaving them in the sedimentary rocks after death. Ex.: Ammonites fossil. * **Trace:** Traces that indicate an activity of an old living organism leaving them in sedimentary rocks during its life. Ex.: Dinosaur’s foot print. ## Question * Choose the correct term (cast - mold - trace) of each of the following fossils: 1. Fossil ....... of ferns. 2. Fossil .......... of worms' tunnels. 3. Fossil .......... of trilobite. ## Petrified fossils ## Importance of fossils * Fossils are important, because they help in: * **Age determination of sedimentary rocks** * The scientists notice that: The lower layers of sedimentary rocks have fossils, whose relative age is greater than that of the fossils of the upper layers, these fossils are known as index fossils. * **Index fossils:** They are fossils of organisms that had lived for a short period of time in the past and had a wide geographical range distribution, then became extinct. G.R.: Index fossils indicate the age of sedimentary rocks existed in them. Because the age of rocks is the same age of fossils existed in them. * **Figuring out the paleoenvironment** * Fossils give us an idea about the environment, in which they lived during the old geologic ages, therefore they indicate the climate of these ages. * **Examples:** * **Nummulites fossils:** They are found in the limestone rocks of El-Mokattam mountain and they indicate that this area was a sea floor more than 35 million years ago. * **Ferns fossils:** They indicate that the environment, where they lived was a hot and rainy tropical environment. * **Coral fossils:** They indicate that the environment, where they lived was clear warm shallow seas. * **Studying life evolution** * **Fossil record:** The sequence of fossils in sedimentary rocks layers according to their sequence of appearance from simple to complicated. * **Studying the fossil record showed that:** * Life started first in sea then established on land. * Organisms always developed from simple to complicated. * **A In plant world:** * **Algae** appeared before **Mosses and Ferns** appeared before **Gymnosperms** appeared before **Angiosperms** * **B In animal world:** Invertebrates like (corals and mollusks with shells) appeared before vertebrates. Fish were the first vertebrates that appeared followed by amphibians then reptiles and finally, birds and mammals appeared together. * **The evolution of life from simple to complicated:** Invertebrates, Fish (vertebrates), Amphibians, Reptiles, Birds and mammals. * **Note:** Archaeopteryx fossil is considered a link between reptiles and birds. * **Petroleum exploration** * When searching for petroleum, geologists take samples from the rocks of the exploratory wells. * These samples are studied under microscope. If they contain microfossils like foraminifera and radiolaria, this could point to: * The age of rocks existed in exploratory wells. * The suitable conditions of petroleum formation. ## Question * Put () or (X): 1. Ammonites fossils are found in the limestone rocks of El-Mokattam mountain. () 2. Index fossils indicate the age of sedimentary rocks. () 3. Ferns fossils indicate that the environment where they lived was a sea floor. () * Give reason for: Index fossils are called by this name. ## Exercise * Arrange the following fossils starting with first appearance on the life stage and explain your answer. * Cast fossil of fish - Mammoth fossil - Trilobite fossil - Archaeopteryx fossil - Answer: * Trilobite is from invertebrates that appeared in seas. * Fish were the first vertebrates that appeared. * Archaeopteryx links between reptiles and birds which appeared after fish. * Mammoth is from the mammals that appeared after reptiles. ## Suitable conditions for fossils formation (or preservation): * **First:** Presence of hard skeleton of organism. * **Second:** The body of the organism must be buried immediately after death in a medium that preserves it from decomposition. * **Third:** The existence of a suitable medium, in which the mineral material of rocks replaces the organic material of the living organism. ## TRY to answer worksheet 17 in the Notebook ## TRY to answer worksheet 18 in the Notebook