Classification and Evolution

Question 1

prokaryotae

Answer 1

• unicellular
• no membrane bound organelles
• small ribosomes
• ring of DNA with no associated proteins
• no feeding system (absorbs nutrients across surface/some photosynthesise)

Question 2

protoctista

Answer 2

• unicellular or multicellular
• nucleus and membrane bound organelles
• some have chloroplasts
• some have cilia or flagella
• autotrophic/heterotrophic/parasitic

Question 3

fungi

Answer 3

• unicellular or multicellular
• nucleus, membrane bound organelles and chitin cell wall
• made up of threads or hyphae
• saprophytic feeders (some parasitic)
• can store food as glycogen

Question 4

plantae

Answer 4

• multicellular
• nucleus, membrane bound organelles and cellulose cell wall
• chloroplasts and chlorophyl
• autotrophic
• store food as starch

Question 5

animalia

Answer 5

• multicellular
• nucleus and membrane bound organelles
• can move with cilia, flagella, muscles
• heterotrophic
• store food as glycogen

Question 6

autotrophic

Answer 6

organism that synthesises complex organic molecules from inorganic molecules via photosynthesis

Question 7

heterotrophic

Answer 7

organisms that acquire nutrients by the ingestion of other organisms

Question 8

saprophytic

Answer 8

organisms that acquire nutrients by absorption (mainly off decaying material)

Question 9

taxonomic hierarchy

Answer 9

kingdom
phylum
class
order
family
genus
species

Question 10

Methods of classification

Answer 10

• DNA sequencing
• amino acid sequencing (less accurate as the genetic code is degenerate so it won’t show all mutations)
• comparative anatomy (even less accurate as organisms can look similar without being closely related because of similar environments, selective pressures, similar alleles having a selective advantage therefore similar proteins being produced)

Question 11

Carl Woese

Answer 11

• introduced the three domain system in 1990
• archaea, bacteria, eukaryota
• determined by type of RNA, ribosomes and cell membrane structures
• six kingdom system
• prokaryotae split into eubacteria (“true bacteria” found everywhere) and archaebacteria (found in extreme environments)

Question 12

Theory of evolution

Answer 12

• 1958 - Wallace proposed the theory of natural selection leading to evolution
• Darwin peer reviewed these ideas
• both had similar ideas so published scientific journals
• Darwin published “On the Origin of Species”

Question 13

Evidence for evolution

Answer 13

• paleontology - imprints from dead organism shows older simple organisms compared to more recent complex vertebrates/shows relationships between extinct and living organisms
• comparative anatomy - homologous structures show common ancestors (divergent evolution)
• molecular evidence - comparing proteins by sequencing DNA bases or amino acids

Question 14

Which genes and proteins are usually compared?

Answer 14

cytochrome C (in mitochondria) and haemoglobin as a large number of species have them and they are highly conserved

Question 15

neutral evolution

Answer 15

most variability within the structure of a molecule does not affect its function therefore the accumulation of neutral substitutions (mutations) are not affected by natural selection

Question 16

homologous structure

Answer 16

structure that appears superficially different (and may perform different functions) in different organisms but has the same underlying structure (pentadactyl limbs)

Question 17

Genetic causes of variation (5)

Answer 17

• alleles
• environmental change
• mutation
• meiosis
• sexual reproduction

Question 18

analogous structures

Answer 18

structures that have adapted to perform the same function but have different genetic origins (tail fins of a fish and a whale)

Question 19

convergent evolution

Answer 19

unrelated species start to share similar traits as a result of similar environments or selective pressures therefore similar alleles having a selective advantage

Question 20

three types of adaptation

Answer 20

• anatomical
• physiological
• behavioural

Question 21

ways in which the scientific community can validate research

Answer 21

• different people repeat a study and compare results
• peer review and public a scientific journal
• scientific conferences
• look for evidence from other people’s work

Question 22

how can the age of extinct organisms be estimated? (2 marks)

Answer 22

• fossils
• the deeper the fossil, the older the organism
  (could compare to fossils of known organisms at the same depth in the same area)