evolution/evidence for classification

Question 1

what were original classification systems based on compared to now and why

Answer 1

• 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

Question 2

what evidence do scientists look at for relationships between organisms now

Answer 2

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

Question 3

when and who proposed the 3 domain system

Answer 3

• Carl Woese
• 1990

Question 4

how does Carl Woese’s system work

Answer 4

• groups organisms using differences in the sequence of nucleotides in the cells’ rRNA
• and cells’ lipid structure
• and cell’s sensitivity to antibiotics

Question 5

what is Carl Woese’s 3 domain system

Answer 5

domains:
- Archaea
- bacteria
- eukarya
kingdoms:
- archaebacteria
- eubacteria
- protoctista
- fungi
- plantae
- animalia

Question 6

differences in RNA and ribosomes in the 3 domains

Answer 6

eukarya
- 80s
- RNA polymerase contains 12 proteins
archaea
- 70s
- RNA polymerase contains 8-10 proteins
bacteria
- 70s
- RNA polymerase contains 5 proteins

Question 7

difference between archaebacteria and eubacteria

Answer 7

• both single celled
• chemical makeup is different
• e.g. eubacteria contains peptidoglycan in cell wall while archaebacteria does not

Question 8

archaebacteria

Answer 8

• ‘ancient bacteria’
• can live in extreme environments
• e.g. thermal vents, anaerobic conditions, highly acidic env.

Question 9

eubacteria

Answer 9

• ‘true bacteria’
• all environments
• most bacteria

Question 10

3 main sources of evidence of evolution

Answer 10

• palaeontology
• comparative anatomy
• comparative biochemistry

Question 11

evidence provided by palaeontology

Answer 11

• fossils formed when organism remains are preserved under 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

Question 12

why is the fossil record incomplete

Answer 12

• 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

Question 13

comparative anatomy definition

Answer 13

• the study of similarities and differences in the anatomy of different living species
• involves homologous structures

Question 14

homologous structures

Answer 14

• structure that appears superficially different in different organisms but has the same underlying structure e.g. pentadactyl limb in vertebrates
• evidence for divergent evolution

Question 15

comparative biochemistry

Answer 15

• 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