module 5.1.1

Question 1

what does environmental change act as

Answer 1

a stimulus

Question 2

how do organisms react to stimulus

Answer 2

organisms change its behaviour or physiology

Question 3

what are communication systems needed to maintain

Answer 3

the constant internal environment in a changing external environment

Question 4

how will organisms survive external environmental changes

Answer 4

it places stress on living organisms. for example, a cooler environment will increase heat loss. in order to survive these changes must be monitored and the organism must change its behaviour and physiological process to reduce the stress

Question 5

what system does this use

Answer 5

the hormonal system

Question 6

what is the process of immediate changes in external environment

Answer 6

a quicker communication of the stimulus through the neuronal system

Question 7

what would have to happen in order to maintain metabolic process

Answer 7

these changes must be offset, requiring detection of the changing conditions and communication between cells to offset the changing internal environment

Question 8

what are some examples of metabolic processes being maintained

Answer 8

if carbon dioxide levels increase in the blood, it lowers the pH of the tissue fluid, which can disrupt the action of enzymes
communication between chemoreceptors in the blood, the brain, and the gaseous exchange system are required to offset this change

Question 9

what do the metabolic rates of the cells do

Answer 9

it alter the internal environment, reducing the concentration of substrates, and increasing the concentration of products, which may be toxic

Question 10

why is a good communication needed for groups of specialised cells performing specific functions forming tissues and organs

Answer 10

to ensure that different organs working together to perform the same function

Question 11

give an example of good communication between different organs

Answer 11

the receptor may be far away from the effector

Question 12

what are the 2 systems where cell signalling between distant cells

Answer 12

the neuronal system and the hormonal system

Question 13

describe what happens in the nervous system

Answer 13

it is a network of interconnected neurons that signal to each other across synapse junctions
the neurones can conduct a signal very quickly and enable rapid responses to stimuli that may be changing quickly

Question 14

describe what happens in the hormonal system

Answer 14

uses the blood to transport chemical signals
cells in endocrine glands release a hormone directly into the blood and it is transported throughout the body, but it only recognised by target cells with the complementary cell-surface receptors to the shape of the signalling molecule

Question 15

what does the hormonal system enable

Answer 15

it enables long-term responses to be coordinated

Question 16

what would be facilitated between adjacent cell gaps

Answer 16

the movement of small molecules from cell to cell in a tissue, such as those in the heart

Question 17

how would contact dependent communication may occur

Answer 17

between signalling molecules in the plasma membrane of the signalling cells and receptor proteins present in the plasma membrane of the target cell

Question 18

what do paracrine cells secrete and what do the molecules do

Answer 18

signalling molecules which diffuse locally through the extracellular fluid. the molecules are quickly broken down, so the impact is confined to adjacent cells with the complementary receptor site in the cell-surface membrane

Question 19

what is homeostasis

Answer 19

the maintenance of a constant internal environment despite changes in external and internal factors—CO2 concentration, body temperature, blood glucose, salt, and water potential, as well as pressure must be maintained within a small range of variables

Question 20

what is negative feedback

Answer 20

a deviation from the optimum is detected and a mechanism reverses the change

Question 21

outline the process of of what happens in negative feedback

Answer 21

he change in the internal environment must be detected by sensory receptors, such as temperature, osmo, baro, or chemoreceptors. Then this must be communicated via the hormonal or neuronal system, which transmit a signal via a coordination centre, usually the brain, to effectors which bring about a response. when the effector brings about a response that reverses the initial change in conditions, the system moves closer to the optimum, this is detected by sensory receptors and the stimulus is reduced

Question 22

what are examples of effectors

Answer 22

muscle and liver cells

Question 23

what is positive feedback

Answer 23

a deviation increases the original deviation, so is a mechanism whereby a change is increased. These systems are more rare in the body, but are used to effect larger changes over a short period

Question 24

what is an example from positive feedback

Answer 24

during pregnancy the dilation of the cervix causes the posterior pituitary gland to release oxytocin which increase uterine contractions which stretch the cervix more, causing more oxytocin to be secreted, increasing the dilation of the cervix. the action of neurons also involves positive feedback with an influx in sodium ions depolarising the cell, causing voltage-gated sodium ion channels to open

Question 25

what is an ectotherm

Answer 25

they are not able to control their body temperature using their metabolism; they rely on external sources of heat and their body temperature fluctuates with the external temperature

Question 26

why do many ectotherms bask in the sun

Answer 26

to gain heat directly from the sun, or change the orientation of their body to increase the surface area exposed to the sun during colder parts of the day, and orientate it away from the sun at the hottest parts, as locusts do

Question 27

what are endotherms

Answer 27

controls their body temperature within a small range of variables
- detected by thermoregulatory centre

Question 28

what are some physiological reactions to change in temperature

Answer 28

• endotherms: shivering, sweating, vasodilation-arterioles close to skin, vasoconstriction-arterioles further from skin, hair and/or feathers lie if its too hot; stand up if too cold

Question 29

do ectotherms use more or less energy, why

Answer 29

less because they use less energy in respiration so more energy and food can be converted into growth
This means that the van survives for longer periods than ectotherms

Question 30

what are some behaviour reactions to change in temperatures

Answer 30

• endotherms - basking in sun, orientating the body to increase surface area, playing in mud, find shade, licking skin or fur