Echinoderms are defined as various invertebrate marine animals characterized by a hard, spiny covering or skin. They have attracted much attention due to their extensive fossil record, ecological importance, and unusual body forms. Although most echinoderms are extinct, many living representatives still exist. All living echinoderms have an internal skeleton and a central body cavity, but their outward appearance can vary significantly. For example, starfish and brittle stars have arms that extend from a central disk; sea lilies have a central stalk, or stem, and resemble flowers; and sea cucumbers are wormlike and tend to burrow. The ways in which echinoderms move and feed are as diverse as their body forms. Table 1 lists certain echinoderms and their methods of locomotion (movement) and feeding. Table 2 includes examples of echinoderm habitats around the world. According to Table 1 and Table 2, crinoids can be found feeding on plankton.

Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Based on Figure 1, during which year were the greatest number of prey animals available?

Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Studies have shown that a certain species of deer will only eat a specific type of plant found in the deer's nat- ural habitat, and nothing else. Is this finding supported by the information in the passage?

Predation is an interaction between individuals of 2 species in which one is harmed (the prey), and the other is helped (the predator). Predation can occur among plants and animals as well as between plants and animals. Some biologists contend that herbivores, or plant eaters, are predators. Table 1 indicates some characteristics and examples of certain predators. Predation is very important in maintaining a natural balance in any given ecosystem. For example, without predators, prey populations tend to grow exponentially. Without prey, predator populations tend to decline exponentially. Predators consume individual members of the prey population, thereby controlling the overall numbers in the ecosystem. The number of prey consumed depends on the number of prey present as well as the number of predators present. The rate of change in the number of prey is a function of the birth of new prey minus the death of other prey, due either to predation or other causes. The death rate is assumed to depend on the number of prey available and the number of predators. The rate of change in the number of predators is a function of the births of new predators-which depends on the number of prey-minus the death of some predators. Over long periods of time, predator and prey tend to balance each other out. This is called the predator-prey cycle. Prey numbers will increase when predator numbers decrease. When the number of prey reaches a certain point, predators will start to increase until they eat enough prey to cause a decline in prey numbers. When this happens, the number of predators will begin to decrease because they can't find enough prey to eat, and the cycle will begin again. Figure 1 represents an example of a predator-prey cycle.Based on Figure 1, during the first year, predator numbers were mostly:

Suppose scientists discover a new echinoderm that uses its tube feet to move across the deep-sea floor as it hunts for prey. This newly discovered echinoderm can most likely be classified as a(n):

The instrument shown is used to study:

When the thermometer was in the 40°C water, in the time interval between 0 sec and 2 sec, approximately how rapidly, in °C/sec, was the temperature registered by the thermometer changing?