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AS Biology P1 MCQs Preparation Thread
- Thread starter Soldier313
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From all the sunlight arriving at the plant, a lot is wasted from transpiration, the light misses the leaf, the light passes through the leaf without getting absorbed by the chloroplasts etc... so only 1% of the sunlight is actually used in photosynthesis (this is a number you must know from studying ecosystems)
Also, we know that 10% of the energy in produces is actually useful to primary consumers. This is due to several reasons. For example, the cellulose in the plant's cell walls cannot be digested, so it just passes through the feces of the herbivore. A lot of energy is also wasted in respiration, and also in chewing the plant.
Secondary consumers are more efficient because more parts of the herbivore can be digested such as flesh and meat. However, there are still parts such as bones which cannot be digested. As a result, the efficiency in secondary consumers is higher than that in primary consumers. So the only option is 20%.
All the remaining energy (from cellulose, bones, organic waste) can be digested and used by microorganisms/detrivores/decomposers, so they get the remaining 80% of the energy.
During interphase, DNA replicates. During prophase, histones unwind the DNA so that they can be condensed.
You don't need to know what histones are, just that they allow DNA to be condensed.
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rather call it a Bogus nerve as it is causing confusion!It's not C because athletes, who have greater cardiac outputs, have a lower blood pressure. Hence it can't be C or D. Also, greater cardiac output = more oxygen supplied to muscles = more carbon dioxide taken in.
I don't know why the impulses in the vagus nerve wouldn't increase.The vagus nerve decreases the heart rate.
To clarify even further, plants have a lot of material that is completely useless to herbivores such as cell walls made of cellulose and chloroplasts. Most animals cannot digest cellulose, so it passes through the animal without being used. Secondary consumers eat the herbivores. Herbivores don't have any cellulose in them, nor any chloroplasts. They have mainly flesh and meat which can be completely broken down in the carnivore's digestive system and used as energy in the carnivore. In other words, there is less "waste" in the herbivore than in the plant. Hope that helps
THX. Btw, what does condensation and spiralisation of DNA really means ??
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as u add more substrate to the non competitive inhibition it remains the same rate not increasing
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Pressure potential in a plant cell is how much a plant's cell membrane pushes a cell wall. This happens in a turgid cell. If a turgid cell is placed in a solution, water will leave by osmosis. This will continue to happen until the water potentials of the solution and the cell are the same. When this happens, the cell is no longer turgid, so the cell membrane will not exert a pressure on the cell wall, so the pressure potential will be zero.
Condensation means that the DNA molecules get shorter and thicker (so that it can be viewed by a light microscope after appropriate staining)
Oh i see. Thanks friend
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but the question states that "Turgid plant tissue is placed in a solution which has the same solute potential" so thier will be net movement
Hey, what's the difference between reducing transpiration rate and reducing water potential gradient ??? For reducing transpiration rate, rolled leaves, fleshy leaves, sunken stomata and thick cuticle are needed. As for reducing water potential gradient, only rolled leaves, hairy leaves and sunken stomata are involved. Sigh
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Yess itx C ..well that was so easy
thankss
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Yes its C thankssssss !!!
XPFMember
XPRS Moderator
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Aoa!
need help with some more questions plz...
need help with some more questions plz...
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For 19th questn, visualize mitosis. focus on the spindle fibers at each stage. A is when they are forming that is during prophase. B shows no considerable change in their length so this is meta phase. C shows that the length is reduced.. this must be when chromatids are separated, the anaphase. this leaves D to be the telophase. Here centromeres are detached from spindle fibers as the fibers are now disappearing.