Gas Exchange: Insects, Fish and Plants

Question 1

as the organism gets larger the ——— gets ——-

Answer 1

surface area to volume ratio

smaller

Question 2

what is ficks law

Answer 2

diffusion rate = surface area x concentration gradient / diffusion distance

Question 3

what is the weakness to having a large surface area to volume ratio

Answer 3

they lose more heat

Question 4

how do single celled organisms exchange oxygen and carbon dioxide

Answer 4

simple diffusion across their cell surface membranes

Question 5

name 3 things that make a good exchange surface

Answer 5

1. large surface area
2. large concentration gradient
3. thin exchange surface - short diffusion pathway

Question 6

explain the movement of oxygen in insects

Answer 6

1. oxygen enters through spiracles and into the trachae
2. spriacles close
3. oxygen diffuses through the trachae into the tracheoles where gas exchange occurs
4. oxygen is delivered directly to respiring tissues

Question 7

where does gas exchange in insects occur

Answer 7

tracheoles

Question 8

give 4 adaptations of the tracheoles which make it an efficient gas echange

Answer 8

• highly branched which provides a large surface area
• thin walls so there is a short diffusion pathway
• supply tissues so diffusion is directly into cells
• walls are permeable to oxygen

Question 9

what is abdominal pumping

Answer 9

movement of the insects body by its muscles

Question 10

explain how abdominal pumping helps maintain the concentration gradient of gases in insects

Answer 10

• during movement, muscles around the trachea contract and pump air in the sacs deeper into the tracheoles
• this pumps out carbon dioxide and pushes oxygen through their tracheal system
• this maintains the concentration gradient for oxygen and carbon dioxide

Question 11

explain 3 ways insects balance water loss with efficient gas exchange

Answer 11

1. exoskeleton - impermable which reduces water loss
2. spiracles close to prevent water loss
3. small hairs around the spiracles trap water which reduces the water potential gradient

Question 12

explain the movement of oxygen in Fish

Answer 12

1. water carrying oxygen moves in through the mouth and out through the gills
2. the gills have many finger like projections called gill filaments
3. each filament has many lamellae
4. the lamellae contain capillaries and are the site of gas exchange
5. as water carrying oxygen passes through the lamellae, most of the oxygen is removed and enters the capillaries
6. water containing little oxygen leaves through the gill opening

Question 13

what is the site of gas exhange in fish

Answer 13

lamellae

Question 14

explain 3 adaptations of the lamellae that make it an efficient gas exhange surface

Answer 14

1. many gill filaments that contain many lamellae which provide a large surface area
2. the lamellae have a thin epithelium which means there is a short diffusion distance between water and blood
3. the lamellae are positioned at right angles which allows water to pass through the gills

Question 15

describe the term countercurrent flow

Answer 15

water and blood move in opposite directions

Question 16

explain how countercurrent flow increases the fishes ability to absorb oxygen from water

Answer 16

• water and blood move in opposite directions
• thie means the concentrationgradient is maintained along the entire length of the gill lamellae

Question 17

explain the movement of carbon dioxide into plants

Answer 17

• carbon dioxide enters by the stomata which are opened by guard cells
• it diffuses into the air sacs of the spongy mesophyll down a concentration gradient

Question 18

explain 3 adaptations of the leaf that allow efficient gas exchange

Answer 18

• flat so they have a larger surface area to volume ratio
• contain many stomata which allow ait to move in and out of the leaf
• air spaces in the spongy mesophyll which means there is a short diffusion pathway

Question 19

give 4 adaptations of a plant that reduces their water loss

Answer 19

• at night the guard cells close the stomata
• upper and lower surfaces have a waxy cuticle
• most stomata are found in the lower epidermis
• air spaces are saturated with water vapour from the xylem which reduces the water potential gradient

Question 20

what are xerophytes and give an example

Answer 20

plants that live in dry environments, such as a cactus

Question 21

explain 4 adaptations of xerophytes that help them to reduce water loss

Answer 21

• thick waxy cuticles which means there is an increased diffusion distance which decreases transpiration
• hairs, stomata in pits and rolled leaves all trap water vapor and decrease the water potential gradient
• leaves are reducd to spines which reduces the surface area to volume ratio
• small leaves with reduced number of stomata