3.1.1- Exchange Surfaces

Question 1

when does the need for specialised exchange surfaces arise?

Answer 1

when the size of an organism’s surface area to volume ratio decreases.

Question 2

what is an exchange surface used for?

Answer 2

to help organisms to absorb required substances (oxygen) and to remove waste substances (carbon dioxide).

Question 3

what happens to an organism’s SA:V ratio when it increases in size? why?

Answer 3

it’s SA:V ratio decreases, due to there being less SA for absorption, and greater volume. causing a longer diffusion distance.

Question 4

why don’t single-celled organisms have specialised exchange surfaces? 4 reasons?

Answer 4

• their metabolic activity is low, so oxygen demand and carbon dioxide production is low
• their SA:V ratio is large so gases exchange quickly..
• large surface area allows maximum absorption
• small volume so diffusion distance is small.
• simple diffusion can be used.

Question 5

what are the 4 key features of an effective exchange surface, and where are they found?

Answer 5

• increased surface area, in root hair cells.
• thin layers, in alveoli
• good blood supply, in gills
• ventilation to maintain diffusion gradient, in alveolus.

Question 6

what is the equation connecting ratio, surface area and volume?

Answer 6

ratio = SA / V

Question 7

in the mammalian gaseous exchange system, where does it take place?

Answer 7

in the walls of the alveoli (tiny air sac filled with air)

Question 8

what is the order of air entering a mammals body? 5?

Answer 8

1-mouth/nose
2-trachea
3-bronchi
4-bronchioles
-alveoli

Question 9

what are the three key features of the nasal cavity?

Answer 9

• increased surface area with good blood supply, warming air to body temp.
• hairy lining that secretes mucus to trap bacteria, protecting the lung tissue.
• moist surfaces, increasing humidity, decreasing evaporation.

Question 10

what is the trachea?

Answer 10

the main airway carrying, clean, moist, warm air to the lungs.

Question 11

what are the key features of the trachea?

Answer 11

• wide tube with incomplete rings of strong, flexible cartilage, which stops trachea from collapsing
• lined with ciliated epithelium with goblet cells between and below.
• goblet cells= secrete mucus to trap dust
• cilea= beat/move mucus along to the top of trachea, away from lungs.

Question 12

what is the bronchi?

Answer 12

a division of branches of trachea, similar in structure, smaller versions.

Question 13

what are the key features of the bronchioles?

Answer 13

• walls contain smooth msucle, when it contracts, bronchioles constrict, vise versa, this changes the amount of air reaching the lungs
• lined with thin layer of flattened epithelium, allowing some exchange to occur.

Question 14

what are the key features of the alveoli?

Answer 14

• thin layer of thin, flattened epithelium cells, collagen, elastic fibres.
• elastic tissue allows alveoli to stretch as air is drawn in, preventing bursting.
• increased surface area, thin layers
• good blood supply, good ventilation

Question 15

what is elastic recoil of the alveoli?

Answer 15

when the alveoli stretch when air is drawn in, and return to resting size, helping air squeeze out.

Question 16

what is ventilation?

Answer 16

=the flow in and out of the alveoli, as the result of pressure changes in the chest cavity, brought about breathing movements.

Question 17

what are the two types of ventilation?

Answer 17

• inspiration

- expiration

Question 18

what is a spirometer?

Answer 18

= a device used to measure lung volume and different aspects of the lungs.

Question 19

how does someone use a spirometer?

Answer 19

they breathe in and out of a breathing chamber, which causes it to move up and down, leaving a drawing on a graph.

Question 20

what do fish have to make sure they have efficient gas exchange?

Answer 20

• gills, with a large SA, good blood supply + thin layers
• gill cavity coated with protective operculum, which maintains the flow of water over the gills.
• tips of adjacent gill filaments overlap, slows movement of water (resistance), allowing more gas exchange to occur.
• countercurrent flow

Question 21

what is the COUNTERCURRENT FLOW in bony fish?

Answer 21

an adaptation that means that blood flows in one direction and water flows in the opposite direction over the gills, which maintains a steep conc gradient.

Question 22

what does an insects gaseous exchange system do?

Answer 22

delivers the oxygen directly to the cells + to remove the carbon dioxide in the same way

Question 23

what do insects have to allow gaseous exchange?

Answer 23

• spiracles (small openings), where air enters + leaves
• sphincters, open and close the spiracles, reducing water loss + maximising air entry.
• trachea, lined with chitin
• tracheoles, spread into tissue, gaseous exchange occurs here from tube to cell.