Old and New Species

• Fossils - important evidence on how life has develpoed
• imposible to know for sure how life began 
• No record of the origin of life
• No one there to see it
• Fissils give information about organisms that lived long times ago
• Many beleve that early organisms were soft bodied so fossil records are incomplete

• Remains of plant and animals
• Found in rocks
• Evidence of life years ago
• GRADUAL REPLACEMENT - things that dont decay easily (bones, teeth etc.) replaced by minerals forming a rock like substance 
• CASTS/IMPRESSIONS - buried in soft material (clay) clay hardens leaving a cast eg roots, footprints ec. 
• PRESERVATION 
  • amber - no oxygen so decay microbes cant survive
  • glaciers - to cold for decay microbes to work
  • peat bogs - too acidic

Extinction: 

may be caused by - 

• new predators
• new diseases
• new more sucessful compertition

Mass Extinction:

may be caused by - 

• a single catastrophic event
• volcano or asteroid strikes

the development of a new species

speciation takes place when an isolated population becomes so different from the original population that succesful interbreeding can no longer take place. 

specise - a groupe of similar organisms that can reproduce to give fertile offspring.

• when populations of a species are seperated.
• can be due to physical barrier
• geographical isolation - flood or something diving them
• conditions on either side of the barriers are different (eg different climate)
• different characteristics with become more common due to natural selection
• changed so much that they wont be able to breeed = separate species