3. biological systems

Question 1

what is xylem?

Answer 1

tubes that transport water in one direction from the roots to the leaves of the plant.

Question 2

what is phloem?

Answer 2

tubes that transport sugars around a plant in both directions.

Question 3

what is the stomata?

Answer 3

stomata are the gaps between guard cells. they open and close to allow carbon dioxide in for photosynthesis, and oxygen out.

Question 4

what is transpiration? how does it work?

Answer 4

transpiration is the movement of water within a plant.
cohesion means water molecules are attracted to each other. adhesion means water is attracted to the sides of the xylem. together, cohesion, adhesion and water pressure produces capillary action (helps water flow in xylem) moving water to the leaves out of the stomata for evaporation.

Question 5

what is translocation? how does it work?

Answer 5

translocation is the movement of nutrients within a plant. glucose is produced in the leaf, and pumped in companion cells to diffuse into phloem. increased concentration causes water to diffuse in from xylem, increasing turgor pressure. turgor pressure pushes liquid in phloem throughout the plant as glucose is transported into required cells.

Question 6

what is homeostasis?

Answer 6

process that maintains the internal environment of an organism so that cells and systems can function properly. relies on communication between tissues and organs.

Question 7

explain the negative feedback loop.

Answer 7

1. stimulus (change in the internal environment)
2. receptor (detects the change)
3. control centre (interprets the message and responds)
4. effector (muscle/gland/organ that responds)
5. response (what muscle/gland/organ does to return to homeostasis)
6. negative feedback

Question 8

explain how blood glucose is regulated through a negative feedback loop.

Answer 8

1. stimulus (change in blood glucose levels)
2. receptor (chemoreceptor)
3. control centre (pancreas)
4. effector (variety of cells and tissues)
5. response (increase/decrease in blood glucose levels)

Question 9

explain how water balance is regulated through a negative feedback loop.

Answer 9

1. stimulus (change in water volume and osmolality)
2. receptor (osmoreceptor)
3. control centre (hypothalamus)
4. effector (kidneys)
5. response (reabsorption of water changing the osmolality)