Skip to main content

Complex Invertebrates on the Coral Reef

Complex Invertebrates on the Coral Reef
In the sea, as well as on land, invertebrates dominate the animal kingdom. Sponges and corals fill the reefscape with bright colors and endless body forms. Worms hide in every crevice, crack, and safe spot they can find. As abundant as these animals are, they only make up a small portion of the reef invertebrate population. Living alongside them are myriad invertebrates that are more complex and sophisticated. Many of these have well-developed body systems, some of which are very similar to those found in vertebrates.

Simple invertebrates, such as sponges, satisfy all of their oxygen needs by absorbing the gas directly through their cells. The larger and more complex invertebrates do not have this luxury. Complex invertebrates need greater quantities of oxygen than can be provided by simple absorption. In addition, their bodies are often covered with waterproof external structures, further reducing the amount of contact they have with oxygen-rich water. These structural characteristics demand a more complex respiratory system and have led to the development of gills.

Gills are respiratory organs made of thin tissues that contain thousands of tiny blood vessels. Because they are tightly folded, gills pack a large surface area into a small space. As water flows over the gills, oxygen that is dissolved in the water diffuses into the bloodstream. At the same time, carbon dioxide dissolved in the blood diffuses into the water and is carried out of the body.

Popular posts from this blog

Advantages and Disadvantages of an Exoskeleton

More than 80 percent of the animal species are equipped with a hard, outer covering called an exoskeleton. The functions of exoskeletons are similar to those of other types of skeletal systems. Like the internal skeletons (endoskeletons) of amphibians, reptiles, birds, and mammals, exoskeletons support the tissues and give shape to the bodies of invertebrates. Exoskeletons offer some other advantages. Serving as a suit of armor, they are excellent protection against predators. Also, because they completely cover an animal’s tissues, exoskeletons prevent them from drying out. In addition, exoskeletons serve as points of attachment for muscles, providing animals with more leverage and mechanical advantage than an endoskeleton can offer. That is why a tiny shrimp can cut a fish in half with its claw or lift an object 50 times heavier than its own body.
Despite all their good points, exoskeletons have some drawbacks. They are heavy, so the only animals that have been successful with them …

Differences in Terrestrial and Aquatic Plants

Even though plants that live in water look dramatically different from terrestrial plants, the two groups have a lot in common. Both types of plants capture the Sun’s energy and use it to make food from raw materials. In each case, the raw materials required include carbon dioxide, water, and minerals. The differences in these two types of plants are adaptations to their specific environments.
Land plants are highly specialized for their lifestyles. They get their nutrients from two sources: soil and air. It is the job of roots to absorb water and minerals from the soil, as well as hold the plant in place. Essential materials are transported to cells in leaves by a system of tubes called vascular tissue. Leaves are in charge of taking in carbon dioxide gas from the atmosphere for photosynthesis. Once photosynthesis is complete, a second set of vascular tissue carries the food made by the leaves to the rest of the plant. Land plants are also equipped with woody stems and branches that …

Prokaryotic Cell Structure

Prokaryotic cells are about 10 times smaller than eukaryotic cells. A typical E. coli cell is about 1 μm wide and 2 to 3μm long. Structurally, prokaryotes are very simple cells when compared with eukaryotic cells, and yet they are able to perform the necessary processes of life. Reproduction of prokaryotic cells is by binary fission—the simple division of one cell into two cells, after DNA replication and the formation of a separating membrane and cell wall. All bacteria are prokaryotes, as are the archaea.

Embedded within the cytoplasm of prokaryotic cells are a chromosome, ribosomes, and other cytoplasmic particles (Fig. 1). Unlike eukaryotic cells, the cytoplasm of prokaryotic cells is not filled with internal membranes. The cytoplasm is surrounded by a cell membrane, a cell wall (usually), and sometimes a capsule or slime layer. These latter three structures make up the bacterial cell envelope. Depending on the particular species of bacterium, flagella, pili (description follows)…