Bio Paper 2 Super Six Markers

Question 1

Transpiration

Answer 1

Transpiration is the movement of water
Upwards from the roots throughout the plants
Through the lignified cells of the xylem
Driven by evaporation of water through leaves
Flow is unidirectional
By cappilarry action
According to the cohesion tension theory

Question 2

Translocation

Answer 2

Movement of sugars from leaves
Through the plant
As sucrose
Through the living sieve cells
Of the phloem
Flow is bidirectional
To the sink in the plant where the sucrose is needed

Question 3

Thyroxine negative feedback mechanics

Answer 3

Low levels of thyroxine stimulate production of TRH in the hypothalamus
TRH stimulates the release of TSH in the anterior pituitary gland
TSH acts on the thyroid to produce thyroxine
When thyroxine leaves return to normal levels the realises of TRH is inhibited
Therfore stopping the release of TSH
The levels of thyroxine are controlled by negative feedback

Question 4

Menstrual cycle

Answer 4

The pituitary gland produces FSH which stimulates the development of a foccile in the ovary
An egg matures inside the foccile witch produces oestrogen
Oestrogen inhibits fsh
Oestrogen stimulates lh
Corpeous lute starts producing progesterone