Which animal adaptation happened before the others? a. reproduction on land b. development of a coelom c. bilateral symmetry d. lungs

C. Bilateral symmetry

Explanation:

Just before the Cambrian explosion, approximately 600million years ago, multicellular aquatic animals are thought to have developed new body plans. As a result they split into two groups of organisms which were notably radially symmetrical and bilaterally symmetrical. These early bilaterally symmetrical animals were simple organisms without a body cavity called a coelom; further evolution, led to the development of complex coelomates. Eventually, land-dwellers capable of respiring out of water with the aid of lungs emerged, and subsequently, their adaptations allowed for reproduction in their new habitats.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

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