fossils: Evidence for evolution

• A fossil is the preserved remains from a dead organisms from millions of years ago.
• Fossils are found in rocks
• Fossils can be formed from hard body parts, such as bones and shells, which do not decay easily or are replaced by minerals as they decompose
• Fossils can be formed from parts of organisms that have not decayed because of one or more of the conditions needed for decomposition. (dead animals and plants can be preserved in amber, peat bogs, tar pits, on in ice.)
• Fossils can be formed from preserved traces of organisms, such as footprints, burrows and rootlet traces- these become covered by layers of sediment, which eventually become rock.
• The fossils of the simplest organisms are found in the oldest rock and the fossils of more complex organisms are found in newer rocks, showing that over time organisms have evolved.
• scientist have a fairly completed fossil record for the evolution of a horse. it shoes that over 50 million year, the horse evolved from a dog-sized creature that lived in the rain forest, into an animal standing up to 2 meters high and adapted to living on the plains.
• the horses multi-toed feet, adapted for walking across the forest floor, evolved into single-toed hooves more suited for running over open country
• however, many fossil recorded are incomplete. there will be many fossils that have not been discovered yet. there are gaps in the fossil record because many early forms of life were soft-bodied. the soft parts of organisms do not form fossils well. this means that there is little information about what these organisms looked like. any traces of fossils that there may be were likely destroyed by geological activity.
• scientists cannot be certain on how life began because there is not enough evidence

  1. there is no fossil record
  2. there is no direct evidence