6 Markers

Question 1

Outline the structures involved in the mammalian gaseous exchange system

Answer 1

Nasal cavity -
Large surface area and good look supply
Traps dust and microbes
Trachea -
Cartilage rings to prevent from collapsing
Ciliates epithelium and goblet cells which secrete mucus and trap microbes
Bronchi -
Smooth muscle, allow air to move in and out
Alveoli -
Thin wall to increase rate of diffusion
Elastic fibres to stretch and recoil
Large surface area
Surfactant

Question 2

Describe and explain how the structure and properties of different carbohydrate and lipid molecule suit them to their role as energy shortage molecule

Answer 2

Carbohydrates are polymers of glucose, so can be used in respiration to release energy
They are large insoluble molecules so so not affect water potential
Held together by 1-4 glycosidic bonds so can be broken down easily to release glucose
Coiled shape so take up less space

Lipids are fats with more carbon-carbon double bond and are energy rich so more energy can be stored in less space.
They also are insoluble so do not affect water potential

Question 3

Describe and explain how a tiger with striped fur may have evolved from a non striped ancestor (6)

Answer 3

They will have mutated.
For example there was a selection pressure of prey availability so tigers adapted to have striped fur to be able to camouflage this meant that they had a great chance of survival and were more likely to reproduce.
The beneficial alleles were passed on to the next generation, more and more of the relevant gene would have increased with each generation. After many generation all tigers within a population would have been striped.

Question 4

Plants lose water by transpiration.
Plan an investigation into the rate of transpiration in two species of plant that would allow valid data to be collected

Answer 4

Choose two plant species you would like to compare.
Set up a potometer and measure the rate of transpiration by measuring the distance of a bubble travelled over a set time interval. Repeat this experiment 3 times, remove any anomalies and calculate a mean.

When completing this practical make sure that variables are controlled. I.e. Temperature, humidity, light, wind movement and surface area of leaves. They should all be the same for both leaves

Then plot a graph for both plants. The x axis will be time and the y axis will be the distance travelled by the bubble.

Question 5

Mammals and fish both need circulatory systems to transport oxygen to respiring tissues. Compare and contrast the circulatory systems of mammals and fish.

Answer 5

Similarities - both are closed systems
Both have a heart
Both carry oxygen using haemoglobin
Both have arteries, veins and capillaries

Differences - fish have single circulatory
Mammals have double circulatory

Fish have no septum in heart ( one atria and 1 ventricle), mammals have a septum in heart and two atria two ventricle.

In Fish blood pressure is lower to organs, in mammals blood is maintained at higher pressure

Fish is less efficient at transporting oxygen to tissues, mammals are more efficient at transporting oxygen to tissues.

Question 6

Describe and explain the precautions that need to be taken when setting up and using the potometer to ensure no air is present (6)

Answer 6

When setting up
Cut stem under water so no air can enter through xylem
Have apparatus under water so air bubble could block xylem

when using
do not allow the bubble to move too far so that the bubble does not enter the xylem and same bubble could be reused

Measure transpiration accurately to ensure validity of the results

Keep the shoot supported to avoid breaking of the water column