Communication And Homeostasis 5.1

Question 1

Why do multicellular organisms need communication systems?

Answer 1

-animals and plants need to respond to changes in the internal and external environment
-they need to be able to coordinate the activities of different organs

Question 2

What is a sensory receptor?

Answer 2

-cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials

Question 3

What is an effector?

Answer 3

-a cell, tissue or organ that brings about a response

Question 4

What is negative feedback?

Answer 4

-the mechanism that reverses a change, bringing the system back to optimum

Question 5

What is positive feedback?

Answer 5

-the mechanism that increases a change, taking the system farther away from the optimum
E.g. during labour- the dilation of the cervix

Question 6

What is an endotherm?

Answer 6

-an organism that uses heat from metabolic reactions to maintain body temperature

Question 7

What is an ectotherm?

Answer 7

-an organism that relies on external sources of heat to maintain body temperature

Question 8

How do ectotherms increase their temperature?

Answer 8

-move into a sunny area
-lie on a warm surface
-expose a larger surface area to the sun

Question 9

How do ectotherms decrease their temperature?

Answer 9

-move out of the sun
-move underground
-reduced the body surface exposed to the sun

Question 10

What are the advantages and disadvantages of ectothermy?

Answer 10

ADVANTAGES-
Ectotherms rely on external sources of heat to keep warm. They do not use up energy to keep warm. Therefore:
->less of their food is used in respiration
->more energy and nutrients gained from food can be converted to growth
->they can survive for longer periods without food
DISADVANTAGES
->they are less active in cooler temperatures, meaning they are at risk from predators while they are cold and unable to escape and they cannot take advantage of food that is available while they are cold

Question 12

What are some physiological mechanisms used by endotherms to maintain body temperature?

Answer 12

Question 13

What are some behavioural responses used by endotherms to maintain body temperature?

Answer 13

Question 14

What are the advantages and disadvantages of endothermy?

Answer 14

ADVANTAGES-
Endotherms can:
->maintain a fairly constant body temperature whatever the temperature externally
->remain active even when external temperatures are low which means that can take advantage of prey that may be available or escape from potential predators
->inhabit colder parts of the planet
DISADVANTAGES-
Endotherms:
->use a significant part of their energy intake to maintain body temperature in the cold
->need more food
->use a lower proportion of the energy and nutrients gained from food for growth

Question 15

What is the role of hypothalamus in control of temperature regulation in endotherms?

Answer 15

->if the core temperature changes the temperature of the blood will change
->temperature receptors in the HYPOTHALAMUS of the brain detect this change. The hypothalamus then sends out impulses to cause different responses that will reverse this change

Question 16

What is the role of peripheral temperatures in endotherms?

Answer 16

-endotherms detect external temperatures via peripheral receptors; these are thermoreceptors found in the skin and mucous membranes
->receptors detect heat and cold
->impulses are sent from the receptors to the hypothalamus