Old and new species

• remains of organisms from many years ago
• they provide existence that organisms lived ages ago
• many soft bodied animals left little traces behind
• many fossils were destroyed by geological activities or haven't been found yet

GRADUAL REPLACEMENT BY MINERALS:

• things like teeth, shells and bones
• they form a rock like substance shaped like the original part
• surrounding sediments also turn to rock but fossil stays inside the rock

CAST AND IMPRESSION:

• fossils form when the organism is buried in a soft material like clay
• the clay will harden and a cast is formed

PRESERVATION WHERE NO DECAY HAPPENS:

• in Amber there is no oxygen or moisture so decay microbes can't survive
• in glaciers it's too cold

• extinction happens if you can't evolve quickly enough
• many species become extinct because: the environment changes too quick, a new predator kills them, new diseases, they can't compete for food, catastrophic event kills them
• speciation is the development of a new species
• a species is a group of similar organisms that can reproduce to give fertile offspring
• speciation occurs when population of the same species become so different that they no longer breed together to produce fertile offspring
• isolation and natural selection lead to speciation
• isolation is where populations of a specie are separated which can be due to a physical barrier
• the conditions on either side are different
• eventually individuals from either side will have changed so much that they can no longer breed with each other and become separate species