bio evolution test
Development of the Nucleus - Eukaryotic cells
A prokaryote grows and develops folds in its membrane to maintain an efficient Surface area to volume ratio. The infoldings are pinched off forming an internal membrane. The nucleoid region is enclosed in the internal membrane, becoming the nucleus.
Development of the Mitochondria + chloroplast - Eukaryotic cells
An aerobic proteobacterium enters a larger anaerobic prokaryote (as prey or parasite and survives digestion). It provides a rich source of ATP to the host, which allows it to out-compete other prokaryotes. The host cell grows and so does the proteobacterium, subsequent generations also contain these and it evolves and assimilates to become a mitochondrion
evidence of endosymbiotic theory
Mitochondria and chloroplasts: have their own DNA, have ribosomes similar to prokaryotes (70S) and a double + inner membrane similar to them. THey are roughly the same size as bacteria and susceptible to antibiotics. They use mRNA to synthesize their own proteins and transcribe DNA. RNA in prokaryotic ribosomes are closely related to RNA in mitochondrial ribosomes. Both organelles can only be produced by division of pre-existing ones by binary fission
criticisms of endosymbiotic theory
When mitochondria and chloroplasts are removed from the cell, they cannot survive on their own. The ability to engulf another cell and have it survive does not guaruntee the host cells ability to pass onto their offspring the genetic information to make the newly acquired organelle
Cell specialization and multicellularity
cells evolved further due to their ability of compartmentalization which allows for reactions to proceed more efficiently and more specialization. Multicellularity (showed up 1.2 billion years ago) allows for cell differentiation into different tissues and organs which have developed the ability to communicate so that organisms can better adapt to their environments.