<span>I think you have repeated the same question
The intrinsic conduction system determines the basic rhythm of the beating heart. It consists of autorhythmic cardiac cells that initiate and distribute impulses (action potentials) throughout the heart which causes the heart to contract and expand which causes the beating or pumping of heart</span>
Cycas and Ginkgo are referred to as living fossils because they have not yet changed over the years while its related members or species have become extinct or fossilised. You can put Cycas as your answer
Two of the five bases in nucleic acids are adenine and guanine which are purines.
They are less brighter because of the lesser amount of heat in them. In fact, sunspots are identified as areas that don't subject to heat very much, and are shown as dark spots because it's not hot enough to glow the yellowish orange color we usually see
Hope this helped!
Thanks!
~Steve
