evolution of life

definition for life

no universal defenition

• in biology: physical entities that have biological processes (eg. metabolism & birth)

to be functionally alive 3 parts are required:

• information that is physically represented (= DNA & RNA)

• Machinery that uses energy to make copies of the information (= replication)

• structure that houses the information and the machinery

modern ‘tree’ of lfie

Eukaria

• single or multicellular

• eukaryotes: DNA in nucleus

• most complex

Archaea

• single celled

• prokaryotes: no nucleus

• can adapt to extreme environments

Bacteria

• single celled

• prokaryotes: no nucleus

• most succesful form of life

phylogentics

study of the evolutionary history of life

• uses phenotype (anatomical similarities & differences) & genotype (genetic similarities & differences)

Which principle is used in phenotypical comparisons in phylogenetics

PARSIMONY PRINCIPLY = phylogeny that requires the least amount of evolutionary changes is most likely to be correct

Complications with parsimony principle

1) hard to distinguish analogous and homologous traits

• similar adaptions can evolve independently to solve similar environmental challenges

2) nature does not always work in simplest possible way

• came clear with advances in genetics

• some species look totally different but are closely related (eg. platypus and hedgehog - vogelbekdier en egel)

earth has not been a stable environment

environmental conditions on this planet have been extremely diverse during its history → organisms have been shaped acoordingly during different periods

1) earth’s position in space in relation to the sun

• rlipitical orbit 

• variation of tilt

• axial wobble

2) regular incidents (eg. movements of tectonic plates)

3) unpredicted incidents (eg. meteorites)

eon

history of life is divided into eons → ‘similar’ environmental conditions and dominant groups of species within 1 eon

between eons = drastic environmental changes that triggered mass extinctions

When did different forms of life evolve

precambrian eon (archean area): simple life (3.8-3.6 bya)

• where?→ we don’t know only hypotheses (eg. deep ocean / thermal vents…)

• what kind? → simple life 

Proterozoic eon: multicellular eukaryotic organisms (2bya)

cambrian eon: multicellular animals (600 mya)

Ordovician period: first chordates from which vertebrates evolved (460 mya)

2 facts about early earth

• sun ignited ± 5 billion years ago

• hadean eon: earth changed from liquid to solid & crust cooled

early eath was different 

• less oxygen (>1%)

• violent volcanic activity

• faster rotation speed

• hostile environment for life

Prime candidate to be the first form of life (but…)

self replicating RNA

• but they do not leave fossils → no traces of themselves…

life has changed the environment on earth and environmental changes have changed life

• give an example of the first

bacteria started with fotosynthesis → O2 in atmosphere → protective ozone layer around the planet

What’s good in extinctions?

large number of species dissapears → ecological richness open up → species that survived can employ this ecological niches

• adaptive radiation

• eg different type of mammals & birds: dinos went extinct → new ecological niches opened → new species of mammals & birds started to diversify from those species that survived the evolutionary bottle neck that killed the dinos

last common ancestor

the last common ancestor of two species is the species in the past form which the two species started to differentiate

common ancestor for all known life (when + name)

last UNVIERSAL common ancestor

• 3800 mya

• ‘LUCA’

timeline of lives

5 billion ya: sun is born & pretty soon after that the solar system (earth & moon) formes

• How did the moon formed? → earth had a sister planet (Thea) & she ran into earth splitting the planet in 2 → moon

  • In the early solar system the moon was much closer to earth & it is gradually drifting away as it orbit is distancing from the planet => earth spin is constantually slowing & slowing as the gravitational pool of the moon gets weaker & weaker

3.8 billion ya: first forms of life are born (cells without nuclei)

3.5 billion ya: fotosyntheses => rise of oxygen in the atmosphere => ozone layer

2 billion ya: eukaryotes (first cells with nuclei)

Cambrian explosion: multicellular animals

300 million years ago: reptiles → dinos

250 millions ya: birds & mammals

• Only after dinos went extinct, birds & mammals started massive adaptive radiation into different species

10 millions ya: primate evolution 

• However, the modern human (homosapien) only have been around for the last 200 000 years (= short in evolution time scale)