Classification and Evolution Flashcards
prokaryotae
- unicellular
- no membrane bound organelles
- small ribosomes
- ring of DNA with no associated proteins
- no feeding system (absorbs nutrients across surface/some photosynthesise)
protoctista
- unicellular or multicellular
- nucleus and membrane bound organelles
- some have chloroplasts
- some have cilia or flagella
- autotrophic/heterotrophic/parasitic
fungi
- 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
plantae
- multicellular
- nucleus, membrane bound organelles and cellulose cell wall
- chloroplasts and chlorophyl
- autotrophic
- store food as starch
animalia
- multicellular
- nucleus and membrane bound organelles
- can move with cilia, flagella, muscles
- heterotrophic
- store food as glycogen
autotrophic
organism that synthesises complex organic molecules from inorganic molecules via photosynthesis
heterotrophic
organisms that acquire nutrients by the ingestion of other organisms
saprophytic
organisms that acquire nutrients by absorption (mainly off decaying material)
taxonomic hierarchy
kingdom
phylum
class
order
family
genus
species
Methods of classification
- 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)
Carl Woese
- 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)
Theory of evolution
- 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”
Evidence for evolution
- 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
Which genes and proteins are usually compared?
cytochrome C (in mitochondria) and haemoglobin as a large number of species have them and they are highly conserved
neutral evolution
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
homologous structure
structure that appears superficially different (and may perform different functions) in different organisms but has the same underlying structure (pentadactyl limbs)
Genetic causes of variation (5)
- alleles
- environmental change
- mutation
- meiosis
- sexual reproduction
analogous structures
structures that have adapted to perform the same function but have different genetic origins (tail fins of a fish and a whale)
convergent evolution
unrelated species start to share similar traits as a result of similar environments or selective pressures therefore similar alleles having a selective advantage
three types of adaptation
- anatomical
- physiological
- behavioural
