Chapter 15 - Evidence For Evolution Flashcards
What is a genome?
The complete set of DNA in each cell of an organism
What happens to DNA when speciation occurs?
The DNA of the two species will be very similar
What happens to new species as they change due to evolutionary mechanisms?
They accumulate more differences in their DNA
How much DNA do humans share with chimps?
98%
What is junk DNA?
DNA that has no apparent function and serves no purpose
What is an example of junk DNA?
Endogenous retroviruses
What is an ERV?
A viral sequence of DNA that has become a part of an organisms genome
How does an ERV become inserted into a cell?
- enter cell - copies RNA genome into DNA (reverse transcription)
- DNA becomes inserted into one of the host cells chromosomes
When does an ERV become endogenous?
- when it inserted into a sperm or an egg cell
How does DNA provide evidence for evolution?
- all species use the same 4 bases that make up DNA
- the sequence of these bases varies from species to species
- the more similarities, the more closely related
What is the structure of mitochondrial DNA?
Small circular molecules
Where is mtDNA found?
Mitochondria
How does mtDNA provide evidence for evolution?
- only inherited through mother’s lineage
- mtDNA mutates faster than DNA
- more similarities more closely related through mother’s lineage
How do amino acids provide evidence for evolution?
- all proteins in all species are made up of the same amino acids
- the sequence of these amino acids varies form species to species
- the more similarities between the amino acid sequence of a protein of two species the more closely related
What it an ubiquitous protein?
Proteins found in a range of organisms and perform the same function
What is an example of an ubiquitous protein?
Cytochrome c
How does cytochrome c provide evidence for evolution?
- some sequences of amino acids of cytochrome c are always the same
- differences also exist between species
- the less differences that exist the more closely related two species are
How does embryology provide evidence for evolution?
- involves comparing the embryos of different species
- many similarities exist between different species in the embryonic stage eg. Gills - evolved from fish hundreds of millions of years ago
- the later differences arise, the more closely related species are
How do homologous organs/structures provide evidence for evolution?
- involves comparing structures that are similar but used in different ways
What are vestigial organs?
Organs that may have once been important but have lost or changed their function as a species has evolved
How do homologous structures provide evidence for evolution?
- present in ancestors
What are some examples of vestigial organs?
- appendix: digesting leaves
- coccyx: part of the tail
- wisdom teeth: help grind down plant matter
What is a fossil?
An preserved trace left by an organism that lived long ago
What is stratigraphy?
The study of layers, or strata
What is an index fossil?
A fossilised organism that was widely distributed and only present on earth for a short period of time
What does the correlation of rock strata involve?
Involves matching similar layers of rock from different areas
What does the principle of superimposition assume?
Assumes that in layers of sedimentary rock the layers at the top are younger than those beneath them
What is a half life?
The time required for half of any amount of radio active material to decay into a stable non radioactive material
How can index fossils be used to relatively date?
- using index fossils to date relatively is more precise because of their short span of life on earth
- sedimentary rocks that contain the same index fossils are assumed to be the same age
What does fluorine dating involve?
- bone absorbs fluorine ion from water in soil
- the older the bone, the more fluorine it contains
Why is it not possible to relatively date fossils from different sites using fluorine dating?
- the bones absorb fluorine from the surroundings
- the concentration of fluoride ions varies between locations
What is the half life of carbon 14?
5730 years
What does carbon 14 decay to?
Nitrogen
How does carbon 14 dating work?
- living organisms take in carbon
- an organism stops taking in carbon when it dies
- the carbon then begins to decay to nitrogen
- it’s has a half life
- by comparing the ratio of carbon to nitrogen in the sample and knowing the half life an approximate age of when the organism died can be determined
What is the half like of potassium?
1.26 billion years (1.3)
What does potassium-40 decay to?
Argon-40
What are limitations of potassium argon dating?
- fossils over 100,000 years old
- rock being dated must be the same age as the fossil being dated
- the rock sample must be igneous containing potassium
What are some limitation of carbon dating?
- can only be used to date up to 70,000 years
- sample must be organic and contain carbon
- is only reliable if the amount of C-14 in the air has been constant
What are some limitations of stratigraphy?
- the law of superposition cannot always be applied, as due to the earths shifting tectonics strata can be flipped upside down
- fossils can be buried by animals after the deposition of sediment and the animal may be younger then the layers above it
What are some limitations of index fossils?
- the longer the time period a species lived, the less reliable the index fossil
- an animal may have lived in different areas at different times
- an animal may have become extinct in one area before another
