B2.6 Old and New Species

The Origins of Life on Earth
1. There is no evidence for the origin of life on Earth yet we believe it was 3-4 Billion years ago
2. What can we learn from fossils?
  1. They are the remains of organisms preserved in rock
  2. How they form:
    1. From hard parts the animal that do not decay
    2. None of the animal decays properly because of little or no oxygen or bacteria and temperature
    3. Hard parts of the animal are replaced with minerals
    4. Some are footprints or traces of animals
3. Lack of evidence
  1. Many of the earaliest life forms were soft bodied organisms so created no fossils
  2. Most of the time, fossil conditions were not right so many organisms didn't get fossilised
  3. Many fossils have been destroyed by geological activity
4. How something gets fossils
  1. 1) The reptile dies and falls to the ground
  2. 2) The flesh rots leaving the skeleton buried in clay, sand or soil
  3. 3) over millions of years, the skeleton becomes mineralised and becomes rock
  4. 4) the fossil emerges
Exploring Fossil Evidence
1. Using the fossil record
  1. We have enough fossils to understand how specific species went through evolution
  2. Some species such as sharks adapted very early and haven't changed since as there is no reason for them to
2. Extinction
  1. Roughly 4 Billion species have existed and many are extinct
  2. As conditions change species must evolve to suit the conditions. If they can not, then die out
  3. Some species are completely dead and others have living relative
  4. Causes can include new predators, new diseases, or more successful competitivors.
  5. The change of climate may both cause species to evolve or die
3. Organisms that cause extinction.
  1. New predators wipe out prey quickly as the pray can not escape. This is sometimes to human intervention.
  2. New diseases caused by microorganisms can quickly spread and cause species to die. This is common on islands. The Australian Tasmanian Devil is dying of cancer
  3. Some organisms can cause others to be extinct by adapting and taking their food such as rabbits in Australia
More about Extinction
1. The biggest influences on species is a change in their environment
2. Environmental Changes
  1. changes to the climate have been the main cause of extinction
  2. There have been 5 different occasions of extreme extinction from climate change
3. Extinction on a Large Scale
  1. Mass extinction usually happens over a short period of several million years
  2. single catastrophic event like an asteroid, supernova or volcanic eruption
4. The Dinosaurs
  1. 65 million years ago, asteroid collided with Earth in Mexico
  2. The asteroid caused tsunamis, fires, earthquakes, landslides and fired dust everywhere causing a global dark winter and plant life to die
  3. 50-70% of all species became extinct including dinosaurs
  4. Another theory is that global warming caused sea ice to melt and drop water temperature by 9°C
Isolation and the evolution of new species
1. Isolation and Evolution
  1. If two of the same species become isolated from each other in different conditions, different genetic variety will be dominant. The two populations lose the ability to breed and become a new species
  2. Geographical isolation is the easiest way to cause isolation
    1. Mountain range, river, island
    2. Australia
2. Organisms in isolation
  1. When a species evolves in isolation and is only found in one area it is endemic
  2. In Borneo this is very common
3. Speciation
  1. alleles for characteristics enable organisms to survive and breed in new conditions .
  2. When species can no longer breed with originals, this is speciation

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B2.6 Old and New Species

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	Created by mhancoc3 about 10 years ago