B2.2 The Challenges Of Size

Question 1

Why do large multicellular organisms need transport systems?

Answer 1

They have a small surface area to volume ratio and so the rate of diffusion alone would not be fast enough to transport substances around

Question 2

Give 4 examples of substances transported within organisms

Answer 2

• Oxygen is transported in for respiration
• CO2 is transported out from respiration
• Dissolved food molecules from digestion
• Urea and waste products

Question 3

Why do mammals need a double circulatory system?

Answer 3

Double circulatory systems have blood at a higher pressure, allowing it to flow faster and move substances quickly around the body

Question 4

Describe the double circulatory system in mammals

Answer 4

The heart pumps blood to the lungs, the oxygenated blood returns to the heart and is then pumped around the body

Question 5

What is the difference in function between veins, arteries and capillaries?

Answer 5

Arteries carry blood away from the heart Veins carry blood towards (into) the heart
Capillaries flow close to tissues for exchange

Question 6

Describe the structure of arteries

Answer 6

They have thick walls made of muscle and elastic tissue and a small lumen to transport blood under high pressure

Question 7

Describe the structure of capillaries

Answer 7

They have thin walls about one cell thick to allow for the easy exchange of substances at the tissues.

Question 8

Describe the structure of veins

Answer 8

Veins have less muscle and elastic tissue than arteries and they have a larger lumen as the blood is at lower pressure, they also have valves to prevent backflow

Question 9

Describe the structure of the lungs

Answer 9

• The trachea branches into two bronchi
• The bronchi branch into bronchioles
• These bronchioles end in alveoli which are lined with capillaries for exchange

Question 10

Describe the blood flow through the right side of the heart

Answer 10

• Deoxygenated blood flows into the right atrium from the vena cava
• This blood passes through the right AV valve into the right ventricle
• The blood is then pumped out of the heart to the lungs through the right SL valve and into the pulmonary artery

Question 11

Describe the blood flow through the left side of the heart

Answer 11

• Blood enters into the left atrium from the pulmonary vein
• The blood is then pumped through the left AV valve into the left ventricle
• The blood is then pumped out through the left
  SL valve and into the aorta

Question 12

What is the name of the wall that separates the right and left sides of the heart?

Answer 12

The septum

Question 13

What is the name of the artery that supplies the heart tissue with blood?

Answer 13

The coronary artery

Question 14

What type of muscle is the heart made of?

Answer 14

Cardiac muscle

Question 15

Why is the wall of the left ventricle thicker than the wall of the right ventricle?

Answer 15

The left ventricle has to pump blood a further distance around the whole body so the blood needs to be under a higher pressure

Question 16

How is plasma adapted as a transport medium?

Answer 16

Plasma is the liquid part of the blood and most molecules transported in blood need to be dissolved in water

Question 17

Give 3 adaptations of red blood cells to their function

Answer 17

• They have a biconcave shape which gives them a large surface area
• They have no nucleus so there is more space for haemoglobin
• They are very flexible so they can fit through capillaries

Question 18

How are root hair cells adapted to their function?

Answer 18

• Long root hair extension to increase surface area for uptake
• Thin membranes to decrease the diffusion distance

Question 19

What does the xylem transport?

Answer 19

Water and minerals

Question 20

State 3 benefits of transpiration

Answer 20

• The stream of water cools the plant
• The water helps to support the plant by
  creating turgor pressure
• The plant has a constant water supply for
  photosynthesis

Question 21

How is the xylem adapted to transport water?

Answer 21

• It is waterproofed using a substance called lignin

- The xylem cells are dead and have no organelles so there is more space for water

Question 22

Describe the process of transpiration

Answer 22

• Water is lost through the stomata
• More water is drawn up to replace the
  lost water

Question 23

What is the transpiration stream?

Answer 23

The transpiration stream is the flow of water through a plant

Question 24

How does temperature affect the rate of transpiration?

Answer 24

• As the temperature increases, so does the transpiration rate
• The molecules have more KE and evaporation happens faster

Question 25

How does light intensity affect the rate of transpiration?

Answer 25

• The brighter the light, the more stomata are open and the rate of photosynthesis increases which both decrease the amount of water in the plant
• The rate of transpiration increases

Question 26

How does the wind speed affect the rate of transpiration?

Answer 26

• The faster the wind speed, the faster the water is moved away from the plant, creating a steeper gradient and increasing the transpiration rate

Question 27

Describe how to use a potometer to measure transpiration

Answer 27

• The plant is placed in the end of an airtight tube containing water
• A single air bubble is introduced to the tube and the movement of the bubble is measured over time

Question 28

What does the phloem transport?

Answer 28

Sugars like sucrose

www.pmt.education

Question 29

Describe translocation

Answer 29

• Translocation is the movement of sugars up or down the phloem from source to sink (with the use of energy)