Evolution: The Science behind the theory Geological time Fossils Darwin & Natural Selection Species changing over time Anatomical & Embryological evidence Speciation

Summary of Evolution of Life Formation of the earth’s early crust and atmosphere Small organic molecules form in the seas Large (biopolymers) First protocells Single-cell prokaryotes eukaryotes Variety of multicellular organisms form, first in the seas and later on land Chemical Evolution (1 billion years) Biological Evolution (3.7 billion years)

How do we know about the past? Fossils

What is a fossil? A fossil is an impression, cast, original material or track of any animal or plant that is preserved in rock after the original organic material is transformed or removed.

Material that has replaced the once living thing A fossil may be: an original skeleton or shell; a mold or cast; traces such as footprints or worm tubes Material that has replaced the once living thing

Types of Fossils Body fossils – actual parts of an organism bones, shells, leaf imprints

Types of Fossils Trace fossils – evidence of life having been there tracks, burrows, casts

Trace Fossils Mold – reproduction of the inside or outside surface of a living thing Cast – duplicate of the original organism; usually formed by replacement of inside of living thing Molds and casts are actually two common types of trace fossils. A mold forms when something is pressed into soft mud and removed by decomposition or pulled out, leaving an impression of the object. A cast is a 3-D example of an object of the past created when a mold fills up with sediment like mud, sand or volcanic ash.

Trace Fossils Burrows or borings – Spaces dug out by living things & preserved as is or filled in Tracks – impressions of passage of living things

Trace Fossils Imprint – Thin objects such as a leaf that falls onto sediment & leaves an imprint then the sediment hardens into rock

Petrified Fossils Amber & Ice Minerals penetrate & replace the hard parts of an organism producing a copy of them Amber & Ice An entire organism was quickly trapped in ice or tree sap that hardens into amber

Where are fossils found? Sedimentary Rock What type of rock formation is this? Sedimentary, Metamorphic, or Igneous? Sedimentary, you can see the layers. 12

Why sedimentary rock? The animal dies and lies on the ground or sinks to the sea floor. The body begins to decay and is buried under layers of sediment such as mud or sand. These layers eventually become sedimentary rock. http://web.ukonline.co.uk/conker/fossils/how-fossils-were-made.htm 13

What conditions promote fossilization? Hard body parts such as skeletal bones or exoskeletons Rapid burial and/or lack of Oxygen

Unaltered - insects or plant parts trapped in amber or ice ; original unaltered material from the living organism Replacement – the hard parts of an organism dissolve and are replaced by other minerals Petrification – rock-like minerals seep in slowly and replace the original organic tissues unaltered preservation (like insects or plant parts trapped in amber, a hardened form of tree sap) original, unaltered material from the living organism replacement (An organism's hard parts dissolve and are replaced by other minerals, like calcite, silica, pyrite, or iron) petrification (in which rock-like minerals seep in slowly and replace the original organic tissues with silica, calcite or pyrite, forming a rock-like fossil - can preserve hard and soft parts - most bone and wood fossils are permineralized) authigenic preservation (molds and casts of organisms that have been destroyed or dissolved). Authigenic- molds or casts of organisms tissue material is decomposed or of markings left behind by an orgasnism

Putting it all together Examples of Fossils . . . 16

Sporadoceras Nautilus Sporadoceras, which lived during the Devonian period 350,000,000 years ago, are extinct relatives of the chambered nautilus.  The shells of these creatures accumulated on the sea floor and were buried in sediment.  Over the ages they hardened to stone.  Today they are quarried from what is now the Sahara Desert in Morocco. Nautilus 17

Orthoceras Orthoceras were marine, or sea animals similar to modern squid.  They had a shell shaped like a cone.  Orthoceras were active swimmers in warm shallow seas and swam by squirting water out of the body cavity.  They ate small animals and some grew to be 6 feet long.  In the fossilized remains of the shell, you can often see different chambers where the animal lived Squid 18

Trilobites Scientists think that trilobites were the first multiple-celled animal to exist on earth.  These extinct sea animals had exoskeletons, or outer armor, that was divided into 3 parts.  Some crawled on the sea bed, some floated and some swam.  The lived all over the world.  Crabs and lobsters are modern relatives. Lobster 19

Fossil Fish Fish are the oldest and most primitive type of vertebrate.  The first fish were small, the size of a minnow.  They had heavy, bony plates for skin.  They lived on the ocean floor and are through slits on both sides of their throats.  Later, fish began to develop gills, scales and fins and learned to live in fresh water, too.  Some even developed lungs.  Over half the species of vertebrates, both living and extinct, are fish 20

Dinosaur Bones The word dinosaur means "terrible lizard".  Dinosaurs  were reptiles that lived throughout the world and dominated the land for over 140 million years.  Some were as small as a rooster in size.  Other grew to be the largest land animals ever to live and weighed up to 80 tons.  Many dinosaurs ate plants.  Others were meat eaters.  They began to die out when the Earth's climate became colder and plant life changed. 21