Skip to main content

Light and Algal Coloration

Light and Algal Coloration
Light is a form of energy that travels in waves. When the Sun’s light arrives at Earth, it has a white quality to it. White light is made up of the colors red, orange, yellow, green, blue, indigo, and violet. The color of light is dependent on the length of the light wave. Light in the visible spectrum contains colors and has wavelengths between 0.4 and 0.8 microns (1 micron equals 1/1000000 m; a micron is also known as a micrometer). Violet light has the shortest wavelength in the visible spectrum and red has the longest.

Light is affected differently by water than it is by air. Air transmits light, but water can transmit, absorb, and reflect light. Water’s ability to transmit light makes it possible for photosynthesis to take place beneath the surface. All of the wavelengths of visible light are not transmitted equally, however; some penetrate to greater depths than others.

Light on the red side of the spectrum is quickly absorbed by water as heat, so red only penetrates to 49.2 feet (15 m). Blue light is not absorbed as much, so it penetrates the deepest, reaching 100 feet (33 m). Green light, in the middle of the spectrum, reaches intermediate depths. When light enters water that is filled with particles such as dirt and plant matter, as in an estuary, it takes on a greenish brown hue because it only penetrates far enough to strike, and be reflected from, the particles. In tropical water where particulate levels are very low, light travels much deeper before it reaches enough particles to be reflected back to the surface, so tropical water appears blue. Below 1,500 feet (457.2m), no light is able to penetrate.

Because of the way light behaves in water, aquatic plants do not receive as much of the Sun’s energy as do plants on land. To compensate, most species contain some accessory pigments, chemicals that are adept at capturing blue and green light. These accessory pigments provide the plants additional light and thereby help macroalgae increase their rate of photosynthesis. Some of these pigments mask the green of chlorophyll and give colors to macroalgae that are not usually associated with plants. Accessory pigments explain why seaweed occurs in shades of brown, gold, and red. Green algae contain accessory pigments, too, but they do not mask the color of chlorophyll as the pigments in other kinds of algae do.

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)…