Regulation in Plants and Animals

Question 1

Homeostasis

Answer 1

The maintenance of a constant/stable internal environment, within narrow limits, in the face of external change

Question 2

Metabolism

Answer 2

All of the chemical reactions in an individual or cell

Question 3

Negative Feedback

Answer 3

The response opposes the original stimulus

Question 4

Stimulus/stimuli

Answer 4

Change(s) in the environment

Question 5

Order of events in closing the stomata

Answer 5

1. Abscisic acid is released in response to low water levels and is recognised by specific guard cell receptors
2. Chloride and potassium ions are pumped out of the guard cells
3. Water moves out of the guard cells by osmosis (FROM the hypotonic cytosol, THROUGH the partially permeable plasma membrane, TO the hypertonic surrounding fluid).
4. The guard cells become flaccid and the stoma closes.

Question 6

What is the receptor and coordinator in thermoregulation (regulation of body temperature)?

Answer 6

The thermoregulatory centre in the hypothalamus (in both cases)

Question 7

Name the three categories of adaptation seen in organisms that make them better suited to survive and reproduce in their environment.

Answer 7

Structural, Physiological and Behavioural

Question 8

Name the hormone released in response to low blood glucose levels and the cells that release this hormone, and describe the effects of the hormone.

Answer 8

Glucagon, released by alpha cells of the pancreas. This causes glycogen in the liver and muscle cells to be broken down into glucose, increasing blood glucose concentration.

Question 9

Name the hormone released in response to high blood glucose levels and the cells that release this hormone, and describe the effects of the hormone.

Answer 9

Insulin, released by beta cells of the pancreas. This causes glucose to be stored as glycogen in the liver and muscle cells, decreasing blood glucose concentration.

Question 10

Name the receptor and coordinator for regulation of blood glucose levels

Answer 10

The pancreas (in both cases)

Question 11

Which hormone is released in response to a decrease in blood water level, and which gland produces the hormone?

Answer 11

Anti-diuretic hormone (ADH, or vasopressin), produced by the pituitary gland.

Question 12

Explain the effect that anti-diuretic hormone (ADH, or vasopressin) has on blood water content

Answer 12

Because ADH increases the permeability of the convoluted tubules and collecting ducts of the nephrons, then more water is re-absorbed into the blood. This causes urine to become more concentrated and increases the water content of the blood.

Question 13

What is the receptor and coordinator in osmoregulation (regulation of blood water content)?

Answer 13

Receptor - osmoreceptors in the hypothalamus. Coordinator - hypothalamus