Cnidarians were the first phylum that scientists saw tissue level organization in. Tissue level organization meaning cells all of one type start to function in a unified way.
The answer is most definitely a
Reduce!<span> Buy and use less stuff. This is the best way to conserve natural resources. For example, it takes one ton of raw materials from the earth to make one laptop computer! We can also pay special attention to reducing the amount of non-renewable resources we use. For instance, by reducing our use of non-renewable oil and coal to give us energy and electricity, we can make less air pollution. Instead, we can get energy from the sun, the wind and the ocean's tides to heat our homes and light our rooms. These sources of renewable energy don't create pollution and they will never run out! We can also look for different natural resources to use so that we don't use up too much of one kind. For example, we can make tree-free paper out of plants like kenaf, bamboo, and hemp instead of trees! Using tree-free paper is much better for our forests and all the animals that depend on a healthy forest in order to survive.</span>
Yes, because even though other trees produce more oxygen, the small trees will still produce some oxygen. On top of this there are more small trees than big trees, so even though they make less oxygen, in whole they end up making more when added together!