Arthropods have their bodies organized into distinct regions, with a rear portion that often appears tail-like called the abdomen. This abdomen is the posterior tagma that contains much of the digestive and reproductive systems and can be long and segmented, giving that tail-like look in many species. The front region is the head, which houses sensory and feeding organs; the middle region is the thorax, which typically bears legs (and wings in many insects); the carapace is a protective shield on the front body in some crustaceans, not a posterior region. Therefore, the tail-like posterior segment corresponds to the abdomen.

Cetaceans are a group of mammals uniquely adapted to life in the sea. They breathe air through lungs, give birth to live young, and nurse their offspring, just like other mammals, but they have evolved body shapes, flippers, and tail flukes that make them expert swimmers. They are warm-blooded and insulated by blubber, and they include two main lineages: baleen whales and toothed whales, the latter of which encompasses dolphins and porpoises. Because whales, dolphins, and porpoises form this marine mammal group, they are the correct match. Bats are flying mammals, rabbits are small herbivorous mammals, and zebras are land-dwelling hoofed mammals, not aquatic mammals like cetaceans.

Understanding how energy moves through an ecosystem and how we visualize that flow is key. Producers capture solar energy and pass it to organisms higher up the food chain, but only a fraction of that energy moves to each new trophic level because much is lost as heat and through metabolic processes. An energy pyramid is the best way to represent this because it shows the amount of usable energy at each trophic level and why energy diminishes as you move upward, leading to fewer top-level consumers. Other terms don’t capture this quantitative aspect as clearly. A food chain shows a single linear path of energy transfer, which oversimplifies real ecosystems with many overlapping relationships. A food web maps who eats whom in a network but doesn’t inherently emphasize the changing amounts of energy at each level. A producer-consumer diagram or an ecosystem map isn’t a standard representation focused on energy transfer between trophic levels.

Elbow extension is carried out by the triceps brachii, a muscle that runs along the back of the upper arm. When it contracts, it straightens the elbow by pulling on the forearm, increasing the angle between the upper arm and forearm. The biceps brachii sits on the front of the arm and flexes the elbow, not extends it. The deltoids are shoulder muscles involved in lifting and rotating the arm at the shoulder, while the abdominal muscles belong to the core and don’t move the elbow. So the back-of-the-arm muscle that extends the elbow is the triceps.