Answer:
Option A, oxygen in the atmosphere
Explanation:
The highest level of oxygen reached during this phase of the geological cycle of earth. The oxygen level in Carboniferous period accounted for 35% as compared to 21% of oxygen in the atmosphere in present time.
Due to high oxygen content, the giant and wide varieties of terrestrial animal and plant species evolved. For example – size of insects and carwlies increased, plant became extremely giant, increase in number of tree ferns etc.
Most autotrophs<span> make their "food" through photosynthesis using the energy of the sun.</span>Heterotrophs<span> cannot make their own food, so they must eat or absorb it.</span>
Hello. You have not submitted the experiments to which this question refers, which makes it impossible for it to be answered. However, I will try to help you in the best possible way.
A dependent variable is one that is influenced by an element, in order to present a result, that is, it is a variable that does not establish itself, being dependent on another variable to establish itself. An example of a dependent variable can be seen in an experiment that seeks to determine the differences in growth rates of bean plants that were fertilized with different organic fertilizers. As you can see, this is an experiment where the different organic fertilizers influence differences in the growth rate of bean plants. Thus, the growth of these plants depends on the fertilizer, this growth being the variable dependent on the experiment.
A control group, in turn, is an element of the experiment that does not receive the element that is being tested in the same experiment. The control group is important, because it allows the researcher to see the results of a system where the tested element does not exist, thus being able to determine the real differences that the tested element is capable of causing. Using the same example presented in the paragraph above, we can see that the different organic fertilizers are the elements tested in the experiment. These fertilizers will be applied to the plants, however it is important that at least one of these plants does not receive any fertilizer, so that the difference between a system with fertilizer and a system without fertilizer can be evaluated. This plant that received no fertilizer is the control group.
The awnser is the last one
