Scientists have suggested that organelles such as mitochondria and chloroplasts are similar to one another as a result of the endosymbiotic theory. Why is this

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

a physical change is being made.