On week 5, we studied about endosymbiotic
theory. Lynn Margulis, the American biologist provided evidence that some
organelles within cell were at one time free living cells themselves.
Endosymbiotic
theory suggests that :
- - Eukaryotes
arose from a symbiotic relationship between various prokaryotes.
- - Heterotrophic
( aerobic ) bacteria became mitochondria.
- - Cyanobacteria
( photosynthetic ) became chloroplasts.
- - Host
cell was a large eukaryotic cell.
Basically, the theory said that eukaryotes
evolved when a primitive respiring bacteria was engulfed by another bacteria. There
are many evidences for endosymbiosis. One of them are mitochondria and chloroplasts
are similar in size and morphology to
bacterial prokaryotic cells, and also divided by binary fission. Other than
that, Mitochondria and chloroplast have their own DNA and their own ribosomes. It
have approximately 7 to 8 evidencies related to the endosymbiotic theory.
Next, we learnt about cell division and
totipotency. I am pretty sure that you all that take science stream during
schools have learnt this chapter ( cell division ). As I enter matriculation
programme, I studied again about this topic. When said about cell division or
cell cycle, the word that crossed through my mind are mitosis, meiosis, G1
phase, G2 phase and also S phase. In prokaryotes, the cell cycle is simple and
may occur as often as 20 minutes. In eukaryotes, cells that divide regularly
will go through the cell cycle in about 24 hours. Cells in multicellular organisms
divide to replace lost or damaged cells, and also allow the organism to grow.
While unicellular organism divide to reproduce.
And in Thursday, we have Test 1 for
chapter 1 and 2. The question is basically about evolution, about the scientist
involved in the evolution theory especially Darwin. Sorry Dr :( I will do
better next test.
Thank you !
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