Oxygen is transported in the blood in two ways: A small amount of O 2 (1.5 percent) is carried in the plasma as a dissolved gas. Most oxygen (98.5 percent) carried in the blood is bound to the protein hemoglobin in red blood cells. A fully saturated oxyhemoglobin (HbO 2) has four O 2 molecules attached.
(https://www.cliffsnotes.com/study-guides/anatomy-and-physiology/the-respiratory-system/gas-transport)
Answer:
One key way by which species evolve over time in response to changes in environmental conditions is adaptation by natural selection acting over generations. Characteristics that aid in effective survival and reproduction in the new environment grow more prevalent, while those that do not become less prevalent.
Explanation:
Law of Horizontality in Sediments. ... The Law of Original Horizontality was first proposed by Danish geological pioneer Nicholas Steno in the 17th century. The law states that layers of sediment were originally deposited horizontally under the action of gravity.
Answer: We have found fossils that share specific bony traits that are found only in all whales but absent in every other mammal group, indicating descent from a shared common ancestor with modern whales, and these fossils had legs fully adapted for walking on land, and fundamentally identical to those of older mammals that precede the shared common ancestor that these mammals share with whales.
This tells us that the shared common ancestor of whales and these mammals with legs almost certainly had legs themselves, and inherited those legs from their own older mammal ancestors.
Therefore, whales have ancestors in their lineage that walked on land with legs.
(We also have multiple fossils of ancient whales that had legs transitional in form between fully terrestrial walking legs and flippers adapted for swimming, and modern whales still possess a remnant hip bone buried deep in their bodies.)
