biology questions ,please help?

Hi, I'll try to help you with answers to most of these by telling you which ones are wrong and why ( because that's the best way to learn).

Q1:
- A makes no sense, because the plant takes up water as water and CO2 as CO2, so the same oxygen can't be used for both.
- D is wrong, because NADPH has no oxygen in it, it's just NADP+, H+ and 2e-.
- C is also wrong, because the oxygen given off by the plant is acquired from water, not from CO2. If you remember, the plant splits water apart to get at the H+ ions for the Calvin cycle, and O2 is just a byproduct.
- Therefore, B is correct.

Q2: For this question you have to think about what each part of the leaf is for.
- B is wrong because the cuticle on the plant isn't really a tissue, it's just a layer of waxy stuff to stop the plant using water. It's totally transparent and doesn't photosynthesize at all.
- C and D are both wrong for the same reason. "Epidermis" means skin, and the skin of a leaf is only one layer thick. It doesn't do much beyond holding the leaf together. True, it does photosynthesize a bit, but the question asks where you'd find the MOST chloroplasts.
- A is correct. The mesophyll is all the stuff in the middle of the leaf. The only purpose of this part is photosynthesis. Therefore, lots of chloroplasts.

Q3: This one is a little tricky, because the correct answer is only right when you think about it's implications.
- A is totally wrong. DNA mutation is the same speed in every organism alive (even if more complex ones like us are better at fixing our DNA).
- B is wrong, because obviously not everything needs to photosynthesize to be as big as a panda.
- D is also wrong, because all life, even the tiniest bacteria, use enzymes. They might not be very complex ones, but life is impossible without them.
- The answer is C. Think about how amoebas and pandas get nutrients. Pandas have a complex digestive system and active transport into cells. Amoebas have to just rely on diffusion of nutrients into them. If amoebas got to panda-sizes, their surface-area to volume ratio would be too small and they would die.

Q4: First of all, the function of the collagen fibres in animals is for support.
- A is wrong, because the cuticle provides no support whatsoever.
- B is also wrong for the same reason.
- D is wrong, because phloem companion cells simply regulate what the phloem is doing, but don't provide any support.
- C is correct. Xylem (the water transporter) is the support for a tree, and eventually becomes the wood.

Q1) in the atmosphere, released through open stomata. Q2) pallisade cells Q3) C, diffusion is too slow to provide the life neccities for that surface area:volume ratio.