4.3.3 evidence used in classification
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what’s convergent evolution
2 unrelated species could adapt in similar ways & thus, look similar
how can we determine the differences between animals seen today is evolution
by assuming the earliest living things all had identical versions of these molecules (certain large biological molecules in all living things)
evidence for organisms not evolving separately for long
if they have similar molecules
how can we determine organisms have evolved separately for longer
if they have very different versions of the molecule
what do the differences between these molecules in different species reflect
evolutionary relationships
what can we also use biological molecules in classification for
to clarify & correct relationships we are unsure about
what’s cytochrome c
protein used in respiration which all living organisms who respire must have (but not identical in all species)
what can be compared within cytochrome c to compare between species
the amino acid sequences
what certain conclusions can be drawn when comparing amino acid sequences in cytochrome c
• if sequences same = 2 species must be closely related • if sequences different = 2 species aren’t closely related • more differences found between sequences = less closely related the species are
how can DNA be used to classify organisms
• found in all living organisms • genetic code same for all organisms = universal • changes to sequence of DNA = mutations • comparison of DNA sequences can be used to classify species • more similar sequence in section of DNA = more closely related 2 species
who created the 3-domain system
1990 carl woese
components of the 3-domain system
• eukaryotes • prokaryote = bacteria & archaeae
structural differences of bacteria compared to archaeae & eukaryotes
• diff. cell membrane structure • flagella w/ diff. internal structure • diff. enzymes (RNA polymerase) for synthesising RNA • no proteins bound to genetic material • different mechanisms for DNA replication & synthesising RNA
features archaeae share with eukaryotes
• similar enzymes (RNA polymerase) for synthesising RNA • similar mechanisms for DNA replication & synthesising RNA • production of some proteins that bind to DNA
what did woese argue
• that the differences between bacteria & archaea are fundamental • he suggested these 2 groups are more different than archaea & eukaryotes • thus, an accurate classification system must reflect difference