Mod 8 IQ 12

Question 1

What do living organisms need to control

Answer 1

Living organisms need to control:
 body temperature and metabolic rates
 the concentration of dissolved minerals
 concentration of nutrients such as glucose
 input and output of water
 quantities of wastes (e.g. nitrogenous wastes)
 oxygen and carbon dioxide concentrations
 removal of malfunctioning cells, pathogen, and foreign substances
 repair of damaged cells

Question 2

Stimulus model response

Answer 2

Homeostasis can be explained using a stimulus-response model in which a change in the external or internal environmental conditions is detected and appropriate responses occur via a negative feedback mechanism. It involves
 A stimulus which is a change in the environment that is a disturbance to homeostasis
 A receptor that detects the change in the environment
 A control center that controls the response
 An effector that receives the message and carries out the response
 A response that mitigates the original stimulus, hence the negative feedback

Question 3

How is temperature-controlled in humans

Answer 3

 Detecting changes from the stable state: of our body temperature rises, the temperature rise in the blood stimulates anterior hypothalamus ( and inhibits the posterior hypothalamus). Alternatively, when we experience cold, skin receptors increase activity and send nerve impulses to the posterior hypothalamus

Question 4

Glucose

Answer 4

 glucose is the main source of fuel for cells
after you have eaten a meal the blood glucose level rise
this rise is detected in which case more insulin is produced
Glycogen raises blood glucose levels by metabolizing glycogen into glucose

Question 5

How do animals keep cool and lose heat

Answer 5

Behavioural adaptations
Burrowing
 Nocturnal activity
 Seeking shade
 Cooling down in the water
 Stretching out to increase the surface area for heat loss
Structural adaptations
 Large ears increase the surface area for evaporative heat loss
 A large surface area to volume ratios helps maximize heat loss
Physiological
 Sweating to increase evaporative heat loss
 Increased blood flow to the extremities; more blood flow more blood enters the skin and capillaries and heat is lost

Question 6

How do animals keep warm

Answer 6

Behavioral adaptations
Hibernation
 Migration
 Curling up in a ball or huddling together to decrease the surface area
Structural adaptations
 Insulation such as fat layers, blubber, hair, fur, and feathers
 A small surface area to volume ratio helps to minimize heat loss
Physiological adaptations
 Reduce blood flow to the extremities which keeps the core of the body warm
 Shivering causes rapid contraction and relaxation of skeletal muscles resulting in more heat being generated
 Increase in metabolic activity

Question 7

Hormones that allow homeostasis to be maintained

Answer 7

• Adrenalin which increases heart rate blood pressure and changes the body metabolism
• Cortisol: a steroid hormone that regulates processes such as metabolism and immune response
• Antidiuretic hormone (ADH) and aldosterone  together these hormones help maintain water balance

Question 8

What happens when a person begins to dehydrate

Answer 8

 If a person begins to dehydrate, their blood volume drops this change is detected by the hypothalamus, which stimulates the pituitary to secrete ADH. ADH stimulates the nephrons in the kidney to reabsorb more water. This decreases urine production, increases urine concentration and maintains the concentration of water in the blood

Question 9

Mechanisms of plants that allow water balance to be maintained

Answer 9

Australian sclerophyll plants have a range of adaptations to minimize water loss ( and at the same time allow for gas exchange) such as thin leaves with waxy cuticle, sunken stomata, and stomata only on the underside of the leaf. Leaves hang vertically to reduce the surface area exposed to the sun for limited water and have shallow, extensive root systems to enable uptake of water as soon as it rains. Other plants have deep root systems to access water from deeper soil layers

Question 10

Other mechanisms in plants to allow water balance include

Answer 10

• Dropping leaves in response to water stress through the production of abscisic acid
• Leaf shape, such as small, thick leaves to minimize water loss
• Root hairs that increase the surface area, ensure close contact with the soil and greatly increase the rate of water uptake
• Fleshy leaves that store water