BIOL10004 Lecture Notes - Lecture 1: Cambrian Explosion, Semipermeable Membrane, Extraterrestrial Life
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BIOL10004 – Biology of Cells
MODULE 1: CELL BIOLOGY
LECTURE 1 – WELCOME TO BIOLOGY
1. Evolution through natural selection accounts for the animal kingdom’s diversity – both the
similarities and differences
o Evolution = Unifying theory in biology
§ Earth has a long history
§ All living organisms arose from earlier, more primitive forms
§ Hence, all organisms share a common ancestor
o Natural selection:
§ Individuals in a species show a wide range of variation
§ Fitter individuals with characteristics best suited to the environment are more
likely to survive and reproduce to pass the genes on à DIFFERENTIAL
§ Over time, species will evolve (differential reproduction)
o Origin of life is unknown but there are several theories:
§ Extra-terrestrial life – life from another planet
§ Special/spontaneous creation by supernatural forces – i.e. reducing
environment facilitated organic molecule formation (i.e. RNA)
2. Unity of Biochemical Processes – all organisms share a common ancestor
o Hence, all organism shares certain biochemical reactions
o I.e. All organisms have genetic material (DNA) that contains instructions for how
o Organisms have proteins to carry out these specified instructions
3. The Cell theory – all organisms consists of cells
o The cell is a bag/closed domain where the chemical reactions for life are carried out
o Surrounded by semi-permeable membrane
§ Allows movement of molecules in/out of cell (i.e. toxins out)
o Cell theory:
§ All living organisms are composed of cells
§ All cells come from pre-existing cells (no spontaneous generation of cells)
§ The cell = smallest organisational unit
Darwin’s Dilemma – objections to his theory of evolution
• Where were the first cell(s) in the fossil record?
o Stromatolites – referred to as “living fossils”
o Has cyanobacteria on their surface à looks almost identical to modern day bacteria
o Complex cell types appear more recently
§ How did eukaryotic cells evolve from prokaryotic cells?
o Photosynthetic due to cyanobacteria within.
• How to explain the Cambrian explosion?
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