Evolution

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Evolution

•Is the change in heritable characteristics of organisms or biological populations over many generations

Fossil

•A fossil is the preserved remains of a past organism, or indirect evidence of their existence (such as a footprint).

Body Fossils

Direct evidence, Fossilised remains of the actual parts of an organism (or even the entire organism), such as bones, teeth or eggs(that may contain embryos) +could be preserved by amber (Tree sap)

Moulds + Casts

•A replica of an organism or part of an organism, illustrating its 3D shape, • Cast=Formed when a hollow mould (3D impression) of the organism fills with sediments, minerals and then hardens over time, •Thus, moulds and casts may be found together (top picture) Mould is filled with sediment to form cast(3d model of organism)

Conditions for fossilisation - Organisms which contain hard parts (bones, shells etc.) are more likely to be preserved

Explanation - These are replaced by minerals. Softer parts (flesh) will decay quickly.

Conditionals for fossilisation - Organism is buried quickly

Explanation: Otherwise, the remains may be eaten by scavengers. This also slows down decay. 

Transitional fossil

•A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.

Why are transitional fossils important?

•They help scientists bridge gaps in the tree of life, resulting in a picture of gradual changes (evolution) over millions of years

Index fossils

•Index fossils are fossils used to define and identify geologic periods.

Index fossils must be distinctive, abundant and must have a wide geographic distribution

isotope

a variant of a chemical element that has the same number of protons (atomic number) but a different number of neutrons in its nucleus so basically just remember same proton + different neutron → unstable, however some are stable like carbon 12 with 6 neutrons (IN OUR BODY)

Absolute/Radioactive dating - still has degree of uncertainty

•Involves determining the numerical age, or date range, of the rock material surrounding the fossil or of the fossil sample

•Some elements have atoms which exist in unstable forms called radioactive isotopes

•They will decay into more stable atoms at a consistent rate by releasing energy or particles

•We can look at the percentage of radioisotopes left in a sample to determine approximately how old that fossil is

Relative dating of fossils

•Fossils may be dated by comparing how young they are to other fossils by looking at the order of sediment layer formation.

•The youngest layers (strata) are on the top and the oldest layers are at the bottom. 

Reasoning: This is because fossils are generally found in sedimentary rock, which is formed as layers, when sediments are deposited on top of each other over time.

Half life

•The time it takes for half of the radioactive isotopes in a sample to decay into stable forms.

Example of Half life

Carbon-14 decays into Nitrogen-14. Its half-life is 5730 years.