1- four single bonds, 2- two single and one double bond, 3- one single and one t<span>riple bond, 4- two double bonds.</span>
Answer:
List the features of gas exchange surfaces in animals.
1)They are moist to prevent the cells from drying and to allow gases to dissolve;
2)They have a large surface area , so that a lot of gas can diffuse across at the same time;
3)They have a high concentration gradient - maintained by the movement of air & blood.
The reason why nost scientists thought that the first true cells formed on Earth were anaerobic is being shown in the second option :B. because there was no oxygen on early Earth. Paying attention to this fact scientists discovered that first cells were prokaryotes and greatest part of them created oxygen as a toxic by-product of their own metabolism which make them understand how the planet was provided with oxygen and made a conclusion that first cells were anaerobic.
Answer:
A
Explanation:
.............................spermatophytes...........................
Answer:
This process occurs in two stages: the light reactions and the Calvin cycle. Both stages of photosynthesis take place in chloroplasts. The light reactions take place in the thylakoid membranes, and the Calvin cycle takes place in the stroma.
Explanation:
all living organisms require energy to function.
