Science - Fossils
- A fossil is evidence of past life.
- Fossils can be part of an organism, such as its bones, teeth, feathers, scales, branches or leaves.
- Fossils can also be traces, such as footprints, burrows and other evidence that an organism existed in an area.
- Fossils provide evidence that life has changed over time. Some life forms that used to exist on Earth no longer exist.
- Studying the fossil record also provides evidence that life forms have become more complex over time.
- The study of fossils is called Palaeontology.
Major Milestones in the history of life
- Ice Ages
- Cambrian Explosion
- Merger between mitochondria and anaerobic organisms
- Formation of the KT Boundary (Extinction of the dinosaurs)
- Motion of tectonic plates
- Land animals developing eggs
- Animals moving onto Land
Formation of life on Earth
- Planet Earth forms
- Core and Crust forms
- First Oceans
- First Life (Cyanobacteria or Archea)
- Oxygen accumulates in the atmosphere
- First Animals
- First Vertebrates (Fish)
- First land plants
- Dinosaurs go Extinct
Theory of evolution
- All life on Earth shares a common ancestor.
- All the different species on Earth underwent mutations in the past to better suit their environment.
- Evolution (Not Theory of Evolution) means “descent with modification”
- Natural selection is the concept of survival of the fittest.
- There are 4 conditions for natural selections: variation between individuals, heredity, reproduction and variation of fitness
- Selective pressures are phenomena that impact on an organism’s fitness
Stages of Natural Selection
- A species becomes separated by an environmental factor e.g. formation of a river
- A mutation occurs in one of the isolated groups
- If the mutation improves fitness, the mutation is passed on to the next generation
- After several generations, the isolated group has a majority of individuals carrying the mutation, and these individuals are considered to have evolved.
Law of Superposition
- Because upper layers are younger than the ones beneath them, the law of superposition states that a fossil’s age can be determined by the age of fossils around them. This only applies to UNDISTURBED rock.
- Relative age: age of the fossil based on the Law of Superposition, e.g. Fossil A is older than Fossil B but younger than fossil C.
- Absolute age: the actual age of the fossil, e.g. Fossil A is 6000 years old.
Analysing the Fossil record
- Faulting can cause projections of rock through other layers.
- Folding results in layers of rock being moved away from each other.
Why are fossils important?
- Fossils allow us to determine early biodiversity
- Fossils can be compared to modern day organisms
- Fossils improve our understanding of previous conditions on Earth
- Fossils support our estimates for the age of the Earth
- Fossils provide evidence for Evolution
- Fossils provide evidence of continental drift
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