Endosymbiosis

what did all eukaryotes evolve from

• unicellular ancestor

• had nucleus

• reproduced sexually (meiosis and fertilisation)

• reproduced asexually (mitosis)

• respired anaerobically

• engulfed aerobically respiring bacterium

what did the bacterium provide the common ancestor

supply of ATP produced efficiently from aerobic respiration

what did the common ancestor provide the bacterium

nutrients and food so bacterium could grow and divide and be passed onto daughter cells when the host cell divided

why is this called endosymbiosis

• endo = one organisms inside another organism

• symbiosis = organisms living together

why is the relationship between the bacterium and host cell ‘mutualistic’

• both organisms benefit

what eventually happened overtime to the bacterium and host cell

eventually relationship was so close that neither the host cell or the bacteria could survive without the other - bacteria evolved into mitochondria

what happened when some eukaryotes ingested photosythetic bacterium

could carry out photosynthesis

these bacteria evolved into chloroplasts in plants and eukaryotic algae

what is the evidence for endosymbiosis

both mitochondria and chloroplasts:

• measure around 8 micrometers in length

• have double membranes

• circular naked DNA

• 70S ribosomes

• divide by binary fission

• susceptible to some antibiotics that target prokaryotic structures and mechanisms