SAC 3 (biological systems and homeostasis)

Question 1

xylem cells

Answer 1

• responsible for the transport of water and minerals from the roots to the leaves of the plant
• one way flow
• made up of vessel elements and tracheids
• system of dead cells

Question 2

phloem cells

Answer 2

• responsible for the transport of sugars and other nutrients throughout the plant
• two way flow
• made up of sieve cells and companion cells

Question 3

stomata

Answer 3

• small pore on the leaf’s surface
• opens and closes to regulate gas exchange

Question 4

transpiration

Answer 4

• the evaporation of water from leaves and movement of liquids up the xylem
• capillary action help water move up xylem
• cohesion - attach water molecules to each other
• adhesion - attaches water molecules to the side of xylem vessels

Question 5

translocation

Answer 5

• the movement of substances from a source to other tissues in the plant via the phloem.

Question 6

homeostasis

Answer 6

• the maintenance of a stable internal environment despite changes in the external environment
• e.g change in temp or ph level

Question 7

role of hormones

Answer 7

• endocrine system hormones are carried in blood
• hormones are chemical

Question 8

negative feedback - homeostasis

Answer 8

stimulus - change in internal environment
receptor - detects change
control centre - interprets the message and responds
effector - muscle or gland that responds
response - what the muscle or gland does to return to homeostasis

Question 9

blood glucose - too high

Answer 9

stimulus - blood glucose too high
receptor - cells on pancreas that detect glucose levels
control centre - pancreas release insulin
V insulin message
effector - liver, fat cell, muscle cells
response - absorb glucose from blood

Question 10

blood glucose - too low

Answer 10

stimulus - blood glucose too low
receptor - cell on pancreas that detect glucose levels
control centre - pancreas glucagon is releases
V glucagon
effector - liver, muscles
response - break down glycogen to glucose, release glucose into blood

Question 11

water balance - high water

Answer 11

stimulus - high water
receptor - osmoreceptors
control centre - hypothalamus
effector - kidneys (primary), bladder (secondary)
response - kidney will release water from blood to bladder (increased urine)

Question 12

water balance - low water

Answer 12

stimulus - low water
receptor - osmoreceptors
control centre - hypothalamus
effector - kidneys
response - reabsorb water into blood (less water to bladder, less urination)

Question 13

antiduretic hormone (ADH)

Answer 13

presence of ADH - less urination
absence of ADH - more urination

(duretic means urination, so anti means less)

Question 14

water balance in plants

Answer 14

• guard cells cause stomata to close when the plant has lost to much water
• stomata reduces exposure to the sun