evolution/evidence for classification Flashcards
(15 cards)
what were original classification systems based on compared to now and why
- originally based on observable features
- now based on evolutionary relationships between organisms
due to - scientists not agreeing on how relatively important different features are
- grouping organisms solely based on physical features doesnt show how related they are
what evidence do scientists look at for relationships between organisms now
embryological
fossil
molecular:
- analysing similarities in proteins and DNA
- e.g. how DNA is stored and its sequencing
- comparing amino acids in proteins
- e.g. cytochrome C, haemoglobin
when and who proposed the 3 domain system
- Carl Woese
- 1990
how does Carl Woese’s system work
- groups organisms using differences in the sequence of nucleotides in the cells’ rRNA
- and cells’ lipid structure
- and cell’s sensitivity to antibiotics
what is Carl Woese’s 3 domain system
domains:
- Archaea
- bacteria
- eukarya
kingdoms:
- archaebacteria
- eubacteria
- protoctista
- fungi
- plantae
- animalia
differences in RNA and ribosomes in the 3 domains
eukarya
- 80s
- RNA polymerase contains 12 proteins
archaea
- 70s
- RNA polymerase contains 8-10 proteins
bacteria
- 70s
- RNA polymerase contains 5 proteins
difference between archaebacteria and eubacteria
- both single celled
- chemical makeup is different
- e.g. eubacteria contains peptidoglycan in cell wall while archaebacteria does not
archaebacteria
- ‘ancient bacteria’
- can live in extreme environments
- e.g. thermal vents, anaerobic conditions, highly acidic env.
eubacteria
- ‘true bacteria’
- all environments
- most bacteria
3 main sources of evidence of evolution
- palaeontology
- comparative anatomy
- comparative biochemistry
evidence provided by palaeontology
- fossils formed when organism remains are preserved in rocks by deposits of sediment to form layers of rock
evidence provided: - fossils of simplest organisms (bacteria, algae) are found in the older rocks and fossils of complex organisms (vertebrates) are found in recent rocks
- sequence in which organisms are found matches with their ecological links to each other
- studying similarities in anatomy of fossil organisms shows how closely related organisms evolved from the same ancestor
- allow relationships between extinct and living organisms to be investigated
why is the fossil record incomplete
- soft-bodies organisms decompose quickly before they have a chance to fossilise
- conditions needed for fossils to form are not often present
- many fossils have been destroyed by the earth’s movements
comparative anatomy definition
- the study of similarities and differences in the anatomy of different living species
- involves homologous structures
homologous structures
- structure that appears superficially different in different organisms but has the same underlying structure e.g. pentadactyl limb in vertebrates
- evidence for divergent evolution
comparative biochemistry
- the study of similarities and differences in the proteins and other molecules that control life processes
- e.g. cytochrome C and rRNA
- no. of differences that exist in DNA base order are plotted against rate the molecule undergoes neutral base pair substitutions which tells scientists the point at which the 2 organisms last shared a common ancestor
