Origin of Life Flashcards
(21 cards)
Evidence for life dates back to early what geological eon?
Archean
Significance of Te Po: Hadean Period
Inhospitable to life: extreme volcanic activity, intense geothermal heat, frequent planetary and meteorite collisions.
Conditions contributed to the synthesis of organic molecules. possibly through processes like lightning-driven reactions in the atmosphere, hydrothermal vent activity, or delivery by meteorites.
collision with another planet created the moon and magma ocean which later cooled to become solid crust and liquid water ocean, gradually changing the atmosphere to support life.
How did magma ocean create new atmosphere?
outgassing: As magma ocean cooled and solidified, gases like co2, nitrogen & h20 vapour were released into the atmosphere
water vapour from outgassing condensed forming liquid water and super ocean covering the crust.
Co2 absorbed into ocean reducing greenhouse gases, allowing atmosphere to regulate temp better
early oceans provided stable environments where organic molecules could accumulate and interact
How did life create oxygen rich atmosphere?
The majority of molecular atmospheric O2 was produced by photosynthetic organisms, mostly cyanobacteria
Oxygenic photosynthesis (process by which organisms use sunlight to split h20 and produce O2 as a byproduct
This Great Oxygenic Event (GOE) dramatically increased oxygen levels on earth, enabling more life to be supported
Haldane-Oparin Theory: (3)
Primordial Soup (pre-biotically)
Theory proposes, that life originated from a primordial soup of organic molecules in early oceans.
These molecules were formed by chemical reactions driven by natural energy sources like UV rad from the sun, lightning, and volcanic activity which could convert simple organic molecules to more complex molecules.
As these molecules accumulated, some may have formed simple membrane like structures known as coacervates which concentrated the molecules and created conditions for further chemical reactions. This could have led to the first simple life forms.
Chem oriented
Definition/of life (3)
1) Reproduction: Must contain genes, genetic information of how to replicate/reproduce.
2) Metabolism: Must be able to metabolise energy (via proteins) from external environment to fuel chemical rxns.
3) Contained: Must have defined barrier (lipids) to contain molecules used to replicate and maintain metabolism
RNA world hypothesis
Suggests that early life may have started with RNA rather than DNA or proteins.
According to this idea, RNA could have carried out all the functions of life including self replicating, storing genetic information (like DNA), self catalysing chemical rxns (like proteins)
LUKA (Last Universal Common Ancestor
All life came from a common ancestor before splitting into 3 main domains (Bacteria, Archaea, Eukaryotes)
Steps of Speciation (5)
- Genetic Variation within a population
- Geographical isolation between populations (barrier)
- Natural selection, subject to different selection pressures
- Mutation, accumulation of beneficial mutations
- Reproductive Isolation interbreeding is impossible
What is the role of mutation? (relate to natural selection)
To create/introduce new alleles, contributing to natural selection by creating favourable/unfavourable alleles to be selected for/against to help the species survive/exploit certain features in an environment.
What is Natural Selection?
When populations of organisms are subjected to selection pressures and individuals with favourable alleles that make them best suited to their environment are more likely to survive and reproduce.
What is Sexual Selection?
A type of natural selection where members of one sex choose mates of the opposite sex based on phenotypic features.
What is Gradualism?
The accumulation of changes step-by-step until the organisms are so different from one another that they are considered another species. (occuring over millions of years)
What is Divergent and Convergent evolution?
Divergent: The process where closely related populations of an ancestral species accumulate genetic differences due to being exposed to different selection pressures. This leads to the formation of distinct species, as mutations and favorable alleles spread within each group, allowing them to adapt/become best suited to their specific ecological niches.
Convergent: The independent evolution of two or more unrelated species who evolve to resemble one another due to being exposed to similar selection pressures.
Define Evolution
The process by which the traits of species adapt to their environment over successive generations through random genetic mutations that happen to be more favorable for the survival of the species.
Difference between mutation and natural selection
Mutation variation is random, natural selection and what is favourable is not.
Why was the concept of evolution controversial?
1) Human exceptionalism (hierarchy in nature) where humans were superior
–> diversity of species is great
2) million year timescale (hard to accept what you can’t see/don’t beleive in - 6k earth)
3) The randomness of traits being selected was unappealing (everything happens for a reason)
What did James Hutton (geologist) suggest?
Uniformitarianism - the earth has been gradually changing over a long period of time.
(river/rain erosion changing landscapes over millions of years)
What idea Lamarck was attributed for?
First to put together a coherent evolutionary theory, how the environment shapes the evolution of animals
1) force driving complexity in animals
2) competing force adapts animals to their environment
Darwins observations at the Galapagos Islands:
All species diverged from a common ancestor species
– due to creation of a new niche where selection pressure selected for certain traits to be favoured (long neck turtle).
– After many generations, the favourable traits changed the species until it became a new species.
–> more variation between species with a geographical barrier (no gene flow) which fuelled speciation
3 types of selection pressures
–> directional –>
–> stabilising <–
<– diversifying –>
