AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

Why don't we start questioning each other like we did on the BIO1 thread? It really helps!

Reply 103

ilyking

Original post by Insanity514

Why don't we start questioning each other like we did on the BIO1 thread? It really helps!

what's the phospholipid bilayers function?

Reply 104

_sa

^ isnt that unit 1?

Acts as a barrier to water soluble substances but
allows lipid soluble molecules to pass through.

Reply 105

Original post by Insanity514

Why don't we start questioning each other like we did on the BIO1 thread? It really helps!

We've been doing that already

here, answer

Describe the adaptations of an insect for efficient gas exchange. (6)

Describe the adaptations of a plant for efficient gas exchange. (6)
Positive Rating!

Reply 106

kingam

can anyone remember all the questions

Reply 107

Tinkle

i soo want to do well on this one!

Reply 108

Spongebobu

6

I reckon I can nail this exam, it is just the DNA/Genes that I need to learn everything else is absolutely fine. much better than unit 1 this unit is like 80% learning how stuff works :biggrin:

Reply 109

Original post by SteveCrain

We've been doing that already

here, answer

Describe the adaptations of an insect for efficient gas exchange. (6)

Describe the adaptations of a plant for efficient gas exchange. (6)
Positive Rating!

Wow I think I'll just answer the first one :tongue:

Insects have a ventilation mechanism called air sacs. These air sacs produce short bursts of oxygenated air and pump them to cells for quick respiration. Spiracles close during the contraction of air sacs to stop air escaping. Also the tracheole tips in insects provide a large surface area for oxygen to diffuse across meaning the rate of diffusion increases. The tips of the tracheoles are also filled with fluid meaning that oxygen can dissolve in it before it diffuses again making the rate of diffusion faster. The tracheoles also directly penetrate the cells in an insect and so oxygen and air is directly delivered to each cell and so the rate of diffusion is quicker. The insect also has a waxy skin layer so that water vapours cannot diffuse out of its surface and so this means less useful gases are lost to the environment.

EDIT also the cells of an insect actively use oxygen in respiration thereby maintaining a diffusion gradient...

Anything to add? I hate insects lol

(edited 12 years ago)

Reply 110

anti-up

3

you could also say that during vigorous exercise insects respire anaerobically, producing lactic acid. this reduces the water potential of of the tissue causing water in the tracheoles to move into the tissue - this increases the rate of diffusion in places where oxygen is required the most xD

adaptations of a plant for efficient gas exchange:

Stomata allow diffusion of gases in and out of the leaf, spongy mesophyll layer provides a large surface area for diffusion of gases increasing the rate of gas exchange, palisade mesophyll cells contain many chloroplasts, so CO2 is used up, creating a concentration gradient into the air space. Plants need to balance CO2 intake for photosynthesis with water loss by transpiration, otherwise they will become dehydrated - when guard cells lose turgor they close the stomata, limiting water loss. Waxy cuticle, hairs around stomata, sunken stomata all help limit water loss...

Was this in a paper? If so which one? Struggling to find 6 points there and not sure if they want to hear about the xerophytic adaptations... what have i missed?

Reply 111

Original post by Insanity514

Wow I think I'll just answer the first one :tongue:

Insects have a ventilation mechanism called air sacs. These air sacs produce short bursts of oxygenated air and pump them to cells for quick respiration. Spiracles close during the contraction of air sacs to stop air escaping. Also the tracheole tips in insects provide a large surface area for oxygen to diffuse across meaning the rate of diffusion increases. The tips of the tracheoles are also filled with fluid meaning that oxygen can dissolve in it before it diffuses again making the rate of diffusion faster. The tracheoles also directly penetrate the cells in an insect and so oxygen and air is directly delivered to each cell and so the rate of diffusion is quicker. The insect also has a waxy skin layer so that water vapours cannot diffuse out of its surface and so this means less useful gases are lost to the environment.

EDIT also the cells of an insect actively use oxygen in respiration thereby maintaining a diffusion gradient...

Anything to add? I hate insects lol

You sure air sacs are on the syllabus?

Reply 112

Original post by SteveCrain

You sure air sacs are on the syllabus?

For AQA yeah they are. Its the ventilation mechanism in Insects.

Reply 113

Circadian_Rhythm

14

Original post by Insanity514

For AQA yeah they are. Its the ventilation mechanism in Insects.

Taken from the only AQA endorsed book:

"Ventilation. The movement of muscles in insects can create mass movements of air in and out of the tracheae, This further speeds up the exchange of respiratory gases."

No air sacs for insects.

Reply 114

STARMissyB

1

Im so dreading this exam! :frown:

Reply 115

Original post by Insanity514

For AQA yeah they are. Its the ventilation mechanism in Insects.

But all we need to know is that insects have a ventilation method called Ventilation, or, the mass movement of muscles, which replaces air in the tracheae and tracheoles

Reply 116

Original post by SteveCrain

But all we need to know is that insects have a ventilation method called Ventilation, or, the mass movement of muscles, which replaces air in the tracheae and tracheoles

I dunno we got taught about air sacs as wel :s-smilie:

Reply 117

liviaaa

What does it mean appreciate the tentative nature that can be drawn relating to the causes of varitation in the spec?

Reply 118