Answer: a tiny muscle connected to each hair follicle and the skin. When it contracts it causes the hair to stand erect, and a "goosebump" forms on the skin.
Circulatory system;<span>The circulatory </span>system<span> circulates blood through the </span>body<span>, </span>supplies<span> cells with </span>oxygen<span> and </span>nutrients<span> and</span>removes waste<span> products. Organs: heart, arteries, veins. ... The respiratory </span>system supplies<span> blood with
</span>oxygen<span> in the lungs and </span>removes<span> carbon dioxide.</span>
<span>The human population is increasing, so the likelihood of a mass extinction is also increasing.
The human population is increasing, and historically, as human population has increased, species have gone extinct. As human population increases, and also destroy more habitats to pay for higher standards of living, the probability of mass extinction increases. </span>
But the many-celled algae, make their food by photosynthesis. Plants have complex, multi-cellular reproductive systems and might need wind, birds, or bugs for pollination. Algae can reproduce through tiny spores or even by replication or the growth of broken piec
