<h2>540 million years ago
</h2>
Paleozoic.
Era immediately follows Precambrian It lasted about 4.5 billion years.
When did abundant fossil evidence first appear in the geologic record.
540 million years ago.
<h2><em>what is the main theme in reproduction.</em></h2>
- <em>The five central themes of biology are</em><em> </em><em><u>structure and function of cells, interactions between organisms, homeostasis, reproduction and genetics, and evolution</u></em>
<em>hope </em><em>it</em><em> helps</em>
<em>#</em><em>c</em><em>a</em><em>r</em><em>r</em><em>y</em><em> </em><em>on</em><em> learning</em>
<em>follow</em><em> me</em><em> and</em><em> mark</em><em> me</em><em> as</em><em> brainlist</em><em> plss</em>
Answer: Your brain constantly gets signals from your body which detect the amount of oxygen and carbon dioxide in your blood. Your brain will send signals to the muscles involved in breathing and adjust your breathing rate depending on how active you are.
HOPE THIS HELPED HAVE A WONDERFULL DAY!
Answer:
Cell theory
Explanation:
Also known as the cell membrane.