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biology cycles help

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nitrogen----first of all u need to know abt 3 bacterias
------1)nitrogen fixing bateria which converts nitrogen gas inro ammonia
-----2)nitrifying bactreia converts ammonia into nitrates/nitrites which are used by plantss
-----3)denytrifying bacteria converts nitrites into nitrogen gas

plants absorb nitrates into their rooots by active uptake
the nitrates combine with glucose to form protein(which can be used for growth and tissue repar.....)
some denitrifying bacteria break down nitrates and release nitrogen back into the air.this is a dsetructive process which commonly occurs in waterlogged soils)
farmers increase fertility by
@ adding artificial fertilisers
@ adding manure or compost
@ growing leguminous plants

nitrates can be obtained by plants from the soil with urine, faeces, dead bodies of animals(decomposed bu decomposers)

Menstrual cycle----is of 28 days
the FSH is first released by pituary gland in brain which stimulates the follicle of ovum.
the ovum releases oestrogen which increases thethickness of endrometrium
by negative feedback ovum is released from ovary to the oviduct(ovulation)
at the same time LH is released which increases the size of left over follicle which then releases progestrone which also increases the thickness of endrometrium until a certain point...after negative feeedback of LH the walls of uterus(endometrium) shed and menstuation begins.

hope this helps! :)