The main variables which affect photosynthesis are light, water, CO2 concentration and temperature.
On a deeper level, other factors like amount of chlorophyll, availability of nutrients (eg Mg is needed for chlorophyll synthesis) will also affect the rate of photosynthesis, though these are rarely covered in discussion of this topic.
The thing is that photosynthesis will be held back by whichever factor is in shortest supply.
As I sit in my study in England, the sun is shining brightly, but the temperature outside is only 5ºC. I suspect the rate of photosynthesis is limited by temperature today.
Yesterday was a dull day, but in the middle of the day it was not cold and I suspect there wasn't enough light for photosynthesis. If I had turned the security lights on my house on, the plants in my garden might (possibly) have photosynthesised faster.
In summer, some farmers growing crops in glasshouses actually increase the amount of carbon dioxide in the air as all their plants have plenty of water and light and the temperature is near the best possible for photosynthesis.
A good way to investigate this might be with the help of algae and you can use the 'Immobilised Algae' practical for this.
Although water is needed as a raw material for photosynthesis, don't bother trying to investigate water as a variable - plants normally wilt and wither long before water restricts photosynthesis at the biochemical level. They need water to support the plant to face the sun as well as a raw material of photosynthesis.
The simplest equation for photosynthesis:-
Carbon dioxide + water -----(in light, with chlorophyll and enzymes)----> sugar + oxygen
Temperature speeds up all chemical reactions - photosynthesis is no exception.
Enzymes work better in warm conditions (up to about 50ºC when enzymes start to be destroyed by heat).
The idea to get across is that different conditions will be most important on different occasions. This morning, my garden could do with more warmth - yesterday, it could do with more light / sun!
5: the parasite and the host need each other
Answer:
The most appropriate answer would be option B.
The flaw in their reasoning is that they compared different molecules in a different set of organisms.
For example, they compared the DNA of lizard A and B whereas they compared the RNA of lizard B and C.
In addition, the mutation rates of different molecules (DNA and RNA) are different and thus, comparison of DNA in one set of organism and comparison of RNA in another set cannot be used as the basis for the conclusion.
Answer:
C. About 18 percent of the variation in blood pressure can be explained by a linear relationship between blood pressure and caffeine consumed.
Explanation:
Here, r = 0.428
∴ We can say it will give a positive curve, as 0.428 indicates it is a positive correlation.
Though the amount of correlation is low, still it is positive and more than 0.4
So, nearly about 18% of the variation in the blood pressure can be observed by the consumption of caffeine water. As consumption of caffeine water and blood pressure is both increasing so we can say that r= 0.428 will give a positive linear curve.
