Edexcel AS Biology - 6B101 + 6B102 - Unit 1 and Unit 2 Exam Discussion Thread

does anyone have a checklist/specification topics for the unit 2 exam

does anyone know what raw mark out of 80 was needed in unit 1 and 2 last year to get full ums? Or knows how to calculate it..

Transpiration is the movement of water. The water molecules are held together by cohesive bonds. (Cohesive-tension theory)
The movement is caused by the active transport of minerals into the xylem. Lowering itswater potential.
Water enters the xylem high to low WP via osmosis
This creates root pressure and water moves up in a CONTINUOUS COLUMN

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Can someone explain the garlic practical and important points surrounding it please

I'm pretty sure that our specification doesn't require us to learn about transpiration.

A number of questions to get you guys thinking

1. Give an example of each of the following:

- Anatomical adaptation
- Behavioural adaptation
- Physiological adaptation

2. Explain the plant fertilisation process.

3. Describe the structure of a seed.

4. How can cells become specialised?

5. What is the difference between a pluripotent stem cell and a totipotent stem cell?

6. Name two places in the body where stem cells can be obtained from.

7. What is polygenic inheritance?

It does

It doesn't I've checked the specification, nothing related to transpiration. You just need to be aware of the structure of xylem and sclerenchyma

"5 Compare the structures, position in the stem and function of sclerenchyma fibres (support) and xylem vessels (support and transport of water and mineral ions)."

The function of Xylem vessels includes the way they transport water:
This includes lignification, how structure aids the movement of water, how transpiration occurs and the transpiration stream.
You also need to know about the importance of cohesion and surface tension.

Sorry to burst your bubble

We were taught how structure aids the movement of water and the influence of lignin in xylem vessels but nothing to do with transpiration. My Biology teacher who teaches Topic 4 told me that we don't need to study that in depth.
Cohesion and Surface Tension is pretty much Topic 1 stuff

Page 179 in the Orange book, if you have it on you

My teacher asked the exam board for clarification, and that was what she was told.
Just trying to help

Pretty much everything in the orange book which isn't in a "Did you know?" box can be tested.

We weren't given the orange book, we were given the green book (the fat one).

We have both

I'll take a photo for you if you want?

Anatomical - regulating glucose levels by production of hormones such as insulin and glucagon (humans)
Behavioural - hunting in the night rather than the day (nocturnal animals)
Physiological - having a taller neck so that they can eat from higher trees (giraffes)

Easy peasy

Pollen grain lands on stigma. Pollen grain contains three nuclei (two generative, one pollen tube nuclei). Pollen tube nuclei producing enzymes which digest through the stigma to make a pathway to the ovary. The pollen tube goes through the microphyle and into the ovule. The tip of the pollen tube bursts and the pollen tube nuclei then degenerates leaving the two generative nuclei.
One generative male nuclei will fuse with the egg cell to form a diploid zygote, this will become the actual seed. The other generative male nuclei will fuse with the polar nuclei to form a triploid endosperm which becomes the food store of the seed. This is a double fertlisation

The structure of a seed?

Some genes are activated, other genes are inactive. Genes which are active will transcribe mRNA which will translate for proteins. These proteins modify the cell. This modification is near permanent and so is difficult to reverse. This entire process is called differentiation

Pluripotent stem cells are stem cells which can specialize to MOST not all types of cells however totipotent stem cells are those which can specialize to ALL types of cells

Placenta and Bone Marrow


Many genes working together and interacting to express one characteristic for example many genes work together and interact to express weight (bone density, metabolism, muscle growth, etc.)

It doesn't I've checked the specification, nothing related to transpiration. You just need to be aware of the structure and function of xylem and sclerenchyma

1. Suggest how genetic variation is achieved in meiosis (2 points)
2. Evaluate the use of seedbanks (4 marks)
3. Name another method that animal conservation happens besides captive breeding programmes and reintroduction

Hey Feraligatr, are you sure you didn't mix up Anatomical and Physological in your examples :P

1
Random assortment & Recombination/Crossing over

2
"Evaluate" (So I guess advantages and disadvantages? I haven't read all the mark schemes yet lol)
(+)Advantages
-Can preserve many plants in 'suspended animation' (seeds)
-X-ray can be used to ensure seeds contain fully developed embryos
-Low storage temperature ensures longer survival and prevents sudden germination
-Seeds are quite small so high numbers can be stored in small space=cheap
(-)Disadvantages
-Can't store some seeds such as mango,rubber, oak,avocado because these seeds have to be conserved differently

3
no idea
Education to raise awareness?? lol
Or using tissue culture??