De document geeft een korte en bondige samenvatting van de lectures : Evolution, human history, modernity and future.
De samenvatting is gebaseerd op de lectures en de bijbehorende aantekeningen. Het geeft een overzicht van de stof voor het tweede deeltentamen van het vak.
,Lecture 5 Evolution
Life on earth → 3.8 billion years ago. Only single-celled bacteria started in the ocean.
Prokaryotes.
DNA → blueprint for every living thing.
Photosynthesis → early development. Oxygen, “most important waste product in the history
of world”. Some bacteria live with oxygen, for others it was toxic and led to death. Oxygen
proved to be a more efficient way of life to produce energy.
Prokaryotes die-off → 2.5 billion years ago. Because of the oxygen holocaust.
Eukaroytes evolved → 1.6 and 2 billion years ago
Due to mutations new species evolve.
Cambrian exploding → 550 million years ago. Huge proliferation for plants and enimals.
Amphibians moved from the sea to the land. First animals with eggs.
Dinosaurs → around 250 million years ago. Dominated the Earth for over 150 million years.
After the extinction of dinosaurs the mammals evolved. They possessed forward-facing eyes
and five-fingered, grasping hands.
Charles Darwin → evolution by natural selection. Species are not fixed entities but
constantly changing.
Species → a large collection of individual organisms that are similar enough to interbreed,
but not quite identical to each other. Over a large period of time, random variations in the
features of individuals may cause the average features of an entire species. Such minor
changes accumulate over thousands of generations.
This is not pure chance, individuals that had the luck to inherit from their parents features
that makes them slightly better adapted to their envirionment. They will then pass these
same features on to their childrens. Over time these features will be more and more
common.
So It isn’t that whole species adapted, the individuals who happened to be better adapted by
pure chance were the onces that shape future generations.
Adaptation → living organisms seem to be exquisitely (uitstekend) fitted for the environments
in which they live.
Habitats → the geographical environments in which species live
Niche → explains the way an organism lives. The particular way of living for which an
organism seems to have been sculpted or adapted by evolutionary processes.
As environments are vareid and changeable, organisms have to keep adapting if they are to
survive. This is why evolution never ends. Because there is no fixed standard of perfection
or “progress, adaptation is an endless process.
Selfish gene theory → it is in the genes of ther mother lion to expend resources to feed her
offpsrings. Altruisme → doing something without getting benefit of it.
Multi-level selection → says that natural selection also operates as a group. They can
operate as a group in competition against other groups.
2
, Selfishness beats altruism within groups. Altruistic groups beat selfish groups. Everything
else is commentary.
Inheritance → it had to be very accurate (otherwise no stable species could exist), but not
too accurate (otherwie there would never be change). The qualities of the parents pass on
their offsprings, but their should be slight variations that might either enhance or threaten the
health of particular individuals.
Gregor Mendel →principle of inherdity. Figured out that organisms inherit one gene package
from their father and one from the mother. He also showed that only one of these traits is
expressed in the offspring. If your parents have blue and brown eyes you won’t get a muddy
blue but you will inherit one color or the other. So Inheitance (overerving) does not
automatically lead to the dilution (verwatering) of traits that Darwin had feared.
Watson and Crick → identified the double-helix structure of DNA. They proposed that the
DNA copied itself by splitting the two strands, allowing each strand to acquire free floating
DNA to reassemble complete strands, resulting in full copies of the originals.
Rosalind Franklin → X-ray crystallography images of DNA.
DNA → The sequence of ACGT nucleotides encodes all instructions needed to build and
maintain an organism
Chromosome → single DNA molecule together with other molecules (proteins and RNA)
needed to support and read DNA
Gene → specific region of a chromosome that codes for a singly polypeptide (chain of amino
acids)
Proteins → one or more polypeptides. Proteins do most of the work in the cell.
Genes are expressed in a 2 step proces:
1. Transcription → RNA copy
2. translation → RNA copy is translated into amino acids sequence
3. A triplet, sequence of three codes encodes which amino acid.
All cells in a body have the same DNA, but different genes are expressed in different cells
and under different conditions.
DNA → RNA → Protein
Prokaryotes:
- unicellular → no membrane-bound: DNA floats free in the cytoplasm
- reproduction usually asexual (not two partners needed)
- transcription and translation are simultaneous
Eukaryotes:
- multicellular → DNA within a membrane-bound nucleus
- division of chromosome in cell with mitosis and meiosis
- transcription separated from translation
- sexual reproduction: 2 partners contribute equally to offspring
- alternation of haploid and diploid phases. 1 vs 2 copies of each gene and
chromosome.
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