Evidence For Evolution Flashcards
Comparative biochemistry-DNA, mtDNA
DNA
- dna sequence varies between species
- determine the sequence
- can be compared in different species
- junk dna, non functionl dna so cant be selected for/against
- endogenous retroviruses, viral sequence that has become part of the organisms genome
- less differences in dna sequence means more closely related, more differences means distantly related
mtDNA
- dna sequence varies between species
- determine the sequence
- inherited from only the mother, higher rate of mutations than nuclear dna
- estimates closeness of relationship through maternal ancestry
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Comparative biochemistry-protein sequences
- proteins are made up of long chains of amino acids
- determine the type and sequence of amino acids
- can compare sequence in different species, cytochrome c a ubiquitous protein
- less differences in amino acid sequence means more closely related, more differencesin amino acids sequence means distantly related
Bioinformatics
- use of computers to describe molecular components of living things
- measure changes in dna rather than traditional techniques
- allows for comparison of genomes
- can identify a dna sequence via annotation
Comparative genomics
- compares genome sequences of different species
- compares human genome with other genomes
- helps identify which genes are preserved in species
- helps identify genes that give each organism its unique characteristics
- has helped identify similarity between humans and chimps
Comparative anatomy, embryology and vestigial organs
Anatomy: organs of similar structure across species, yet not necessarily of similar function. If different species of animals have similar structures, can assume they come from a common ancestor
- pentadactyl limb of vertebrates=similar bone structure and position of bones
- species that share homologous structure infers a common ancestor, more structures in common more closely related
Embryology: comparing early stages of development of organisms, vertebrates have similar embryos, gills slits, tail, two chambered heart
-species that have similar embryonic development infer common ancestor
Vestigial organs: structures that have no function in the body, may have once had a function but no longer does, never had a function, once had a minor function/has changed function
- appendix, coccyx, nictitating membrane
- function and structure of vestigial organs helps identify ancestors and times of evolutionary change
Fossil formation
- Organism dies
- Land in a place or buried by others
- Animals and micro organisms eat the soft tissues
- Layers of sediment form on body
- Organic material replaced by minerals
- More sediment is placed on top
- Sediment becomes rock
- Exposed due to natural earth movements
- One fossil is found, means a dig takes place
Best conditions for fossilisation
Quick burial, alkaline soil, anoxic
Perfectly intact fossils are rare, why?
Poor soil conditions, predators carry bones away, erosion, decayed or destroyed
Usually found
Around old lakes or rivers, inside caves, around volcanically active areas
Relative dating, stratigraphy, fluorine dating
Stratigraphy: study of sequence of rock layers, uses principle of superposition-layers on the top are younger than those beneath them. Limitations include, distortions of earths crust, depends on presence of index fossils
Index fossils: used to correlate rock strata, must have bee widespread and in existence for a short period of time
Fluorine dating: when bone is left in soil, fluorine ions replace some of the ions in the bone, the older the fossil the more fluorine in it so relative ages can be set
Absolute dating, potassium-argon, radio carbon, accelerator mass spectrometry
Potassium argon: based on decay of potassium to form calcium and argon, the older the sample is the more potassium argon-40 and calcium-40. Decays at slow fixed rate, limitations in lude only for volcanic deposits, only used for very old samples 100,000 to 200,000 years old
Radiocarbon dating: plants absorb both c-12 and c-14 through photosynthesis, humans or animals eat plant meaning we have c-14 inside us, c-14 decays into nitrogen at a fixed rate with a half life of 5730 years giving of radiation, we can measure the ratio of c-14 and c-12 in a sample, the amount of c-14 indicates number of half lives, number of half lives x 5730 years=approx age=absolute age
Limitations include up to 60,000 years, at least a 3g sample, organic sample
Accel mass spec: new technique for radiocarbon dating, machine that counts actual number if c-14 atoms in a sample, sample can be as small as 100 micrograms eg cave paintings
