evolution/fossils

explain evolution

• The change in characteristics of a species over time

• Gradual - occurs over many generations

• Does not refer to a change in an individual or over 1 generation

define fossil & give examples

• Any preserved trace left by a previously living organism 

Examples: bone, teeth, shells, footprints, etc - for humans = bones, teeth & maybe footprints

explain why fossils are important

• Allows us to determine exactly what extinct species looked like

• Other materials associated with bones help develop a picture of life in the past

• Fossil records can help build a sequence of the evolution of a particular plant or animal

give examples of what researchers can picture of life in the past from fossils

diet, other organisms that existed at the same time, climate, etc.

define fossil record

The record of the occurrence & evolution of living organisms through geological time as inferred from fossils

how is the fossil record evidence for evolution?

• Establishes evolutionary links between species (shows common ancestry)

• Provides evidence of which organisms lived on earth in the past

• Provides examples of organisms which may not be extinct

• Provides examples of transitional organisms between species

why are many of the animal & plant fossils unlike anything that are living today?

due to evolution

what can you presume when present day forms are not preserved in the fossil record?

we presume that they did not exist in the past

identify the requirements to become a fossil / where you can find fossils

• Die in water - not on land

• Choose a low energy environment (lake or swamp)

• The finer the sediment the better

• Ice is good

• Soil conditions: an alkaline soil environment

• An acidic environment

explain why dying in water is desirable for fossilisation

your remains are more likely to be buried by sediment & less likely to be destroyed by scavengers or erosion

explain why a low energy environment is desirable for fossilisation

your remains are less likely to be destroyed by mechanical processes

explain why finer sediment is desirable for fossilisation

finer sediment dramatically reduces the amount of oxygen coming in contact with your corpse & slows bacterial decay, enabling soft tissues to be preserved 

explain why ice is desirable for fossilisation

being trapped in ice low temps which will stop the decay & whole bodies with soft parts can be preserved

explain why alkaline soil is desirable for fossilisation

favours the preservation of bone as new minerals are deposited into the pores of bones (petrified)

explain why an acidic environment is desirable for fossilisation

favors the preservation of soft tissues & bone provided it does not contain any OXYGEN & is at a low temp, complete preservation can occur

how does fossilisation occur?

occur if buried by drifting sand, mud deposited by rivers, volcanic ash or buried rapidly by others of its species slowing the decay process

what causes dead organisms to decay & leave no trace of those organisms

micro-organisms

name the process of discovering fossils

excavation - surface discovery due to erosion

define artefacts

any objects made by humans

identify reasons why there are few fossils / gaps in the fossil record

• No ideal conditions to form fossil 

• Buried too deep to be found

• Located in places that are not possible to get to

• Fossils may have become exposed but were then weathered or eroded

• Destroyed by geological processes/events

• Destroyed by human activity (mines, urbanisation ,etc)

• Fossils may not be recognised as fossils

• May not be looking in the right places

• When discovered scientist may disagree on the interpretation of fossils

• May not be able to date some fossils that are found due to limitations in dating methods