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!
Answer: C. scorpions have changed as a result of natural selection
Explanation:
The text tells us that scorpions today are now smaller than they were in the past. This means that the scorpions have changed since then i.e. they have evolved.
The primary reason for evolution is natural selection which refers to a situation whereby only the organisms that are better adapted in their species survive.
The conclusion that can be drawn from this research therefore is that we have smaller scorpions today because they stood a better chance of survival than the larger ones and so survived whilst the larger ones died out.
Answer:
D/ Kilograms per cubic-centimeter
Geological processes are events that occur on a geological timescale ranging between millions of centuries, hundreds of meters, and thousands of kilometers. Compare this to the everyday models from physics and engineering operated at laboratory units an
