Fish has a singular circulatory system, means the blood carrying oxygen from pulmonary circuit will be dumped into the same chamber as the blood carrying wastes and CO2 in the heart, because the heart has only one chamber.
amphibians has a 3 chamber heart, but still not a complete separated pulmonary circulation. However, it does have 2 loops at this stage. Of course birds and mammal also has this feature. So the distinction will be between fish and amphibian, which is the evolutionary double loop pathway.
The energy pyramid (also called ecological pyramid) quantifies the energy transfer from one organism to another along the food chain. Energy decreases as you move through the levels from the bottom to the top of the pyramid.At the bottom are the p<span>roducers which bring energy from nonliving sources (sun) into the community (photosynthesis).
</span><span><span>After the producers (above them) are the primary consumers. They eat the producers, which makes them herbivores. Above them are the s</span><span>econdary consumers. They eat the primary consumers, which makes them carnivores. And at the top are the </span><span>Tertiary consumers.</span></span>
Answer:
in the wall of the right atrium of the heart.
Explanation:
The sinoatrial node (SA), consisting of spindle-shaped cells, initiates the electrical activity of the heart. From its location in the right atrium in proximity to the superior vena cava, the electrical activity spreads to the atria, whose cells are larger than those of the SA.