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Agnatha, the earliest vertebrates, are considered more primitive compared to Gnathostomata, which evolved later. Agnatha species are mostly scavengers or parasites, such as lampreys, which latch onto other fish to feed. Gnathostomata, with their jaws, dominate aquatic and terrestrial ecosystems. This group includes predators like sharks, and herbivores like grazing fish. Additionally, Gnathostomata possess more advanced skeletal systems, often with bones or cartilage providing robust support. Based on this evolutionary context, which of the following features is exclusive to Gnathostomata but absent in Agnatha?

Which of the following is not true of starfish?

Below is a cladogram, use the information in the diagram to the answer the question. Which listed characteristic would be considered apomorphic?

How can you identify a brown widow?

What is the purpose of the telson in a crayfish?

What is the purpose of the uropod in a crayfish?

True or false: the majority of amphibians must lay their eggs in the water.

How can a queen bee be identified?

Which of the following describes the heart and metabolism of birds?

Amphibians are unique vertebrates that are thought to bridge the gap between aquatic and terrestrial life. Most amphibians, such as frogs, salamanders, and caecilians, have moist, permeable skin that plays a key role in respiration, allowing them to absorb oxygen and release carbon dioxide directly through their skin. They also possess lungs, but their reliance on cutaneous (skin-based) respiration is significant, particularly in aquatic or damp environments. Amphibians have a double life, spending part of their life cycle in water and part on land. Their eggs are laid in water or moist habitats, as they lack protective shells, making them susceptible to drying out. Additionally, amphibians undergo metamorphosis, transitioning from aquatic larvae with gills to terrestrial adults with lungs. This ability to adapt to different environments highlights their role as indicators of environmental health. Based on these characteristics, which of the following is true about amphibians?