TBR 3 - Evolution and life on Earth Flashcards
Define industrial melanism
Darker individuals come to predominate over lighter ones eg peppered moths
Who was responsible for the initial experiments with peppered moths in the 1950s?
Bernard Kettlewell = releasing dark and light moths into un/polluted woods and seeing how many were recaptured
Define artificial selection
Favouring specific traits and allowing them to be inherited = directional selection
Define systematics
Study of evolutionary relationships
What does a phylogenetic tree represent?
Hypothesis about patterns of relationship between species
What are some issues with assuming different appearances meant less relatedness?
- Evolution can be rapid when environ changes quickly, or slow if environ doesn’t change
- Evolution can be convergent
Define taxonomy
Science of classifying living beings into a hierarchy based on shared traits
Define monophyletic group
Includes the most recent common ancestor + all its descendants
Define paraphyletic group
Most recent common ancestor only
Define polyphyletic group
Doesn’t include most recent common ancestor
What is the biological species concept (BSC)?
Defines species as interbreeding populations reproductively isolated from other groups
What 2 issues with the BSC were solved by the phylogenetic species concept (PSC)?
- BSC can’t be used with groups isolated by speciation = can’t tell if interbreeding possible
- BSC can only be applied to sexual forms, PSC to both a/sexual
What are some potential issues with the PSC?
- Lead to recog of every slightly different population as individual species
- Species may not always be monophyletic eg if 1 in 5 populations evolved differently and other 4 became paraphyletic
List some of the molecules present in Earth’s early reducing atmosphere
CO2, N2, H2O, H2, H2S, NH3, CH4
Why was Earth’s atmosphere reducing?
Wouldn’t have required as much energy to drive chemical reactions = easier to from organics
List the simple organics that might have been present in Earth’s early atmosphere
Formaldehyde and hydrogen cyanide -> formic acid and urea -> glycine and alanine
Where did all of today’s molecular O2 come from? When did this happen?
Photosynthetic oxidation of water, mainly in the late Archaean
What are microfossils and what do they resemble in the modern world?
- Fossilised forms of microscopic life = single celled, no appendages, little internal structure
- Resemble prokaryotes
What 2 ways did ancient fixation of C happen?
- Calvin cycle as in photosynthetic bacteria
- Reductive version of citric acid cycle as in lithotrophic bacteria
What are biomarkers and an example of one?
Organic molecules with clear biological origin eg hydrocarbons from fatty acid tails of lipids
Describe how changes in atmosphere led to weathering and later glaciation in the proterozoic
Late Proterozoic = tropics + continental shifts exposing land to ocean = accelerated weathering and decreased CO2 = lower temp = glaciation
How did plants contribute to glaciation?
- Initial colonisation + release of organic acids = lower CO2 + increased weathering = released P + root dvlpmnt = algal growth + weathering = lower CO2 = glaciation
