Seton 10 Biology Chapter 12: Algae
What is a lichen?
A lichen is a plant structure composed of an alga and a fungus growing together in a symbiotic relationship. The alga provides food for the fungus, and the fungus provides security and moisture for the alga.
List some reasons why an abundance of algae in a body of water is hazardous.
An abundance of algae in a body of water (e.g., the "red tide" formed by dinoflagellates) is hazardous because it destroys millions of fish and, subsequently, the dead fish wash up on the shore, producing a stench as well as a health hazard.
What is an alternation of generation?
An alternation of generations is a type of life cycle in which the asexual reproductive stage alternates with the sexual reproductive stage.
Consider the five methods of algal reproduction. Which method most nearly represents the one used by land animals?
Five methods of reproduction of algae are fission, accidental breaking of filaments, conjunction, formation of spores, which are alike, and formation of sperm and eggs. The last is most like reproduction of land animals.
Is an alga in a lichen a landlord, a slave, or a sharecropper?
In a lichen, the alga is held like a slave by the fungus, which uses part of the food which the alga produces by means of its chlorophyll. Yet, the fungus holds the alga in a position where it receives sunlight, and this position, along with the network if the fungus, holds rain water. The alga is either a sharecropper or a slave that is well treated.
What types of algae are used as food?
In the Arctic, reindeer moss (a lichen) is an abundant source of food for reindeer. In the Arctic and Antarctic regions, diatoms feed the great whales. Small crustaceans, crab- and lobster-like animals, and other creatures eat the algae.
Why are nitrogen-fixing algae and bacteria so important?
Nitrogen-fixing algae (Nostoc and Anabaena) and bacteria are very important because they are the only organisms that can form nitrogen compounds and fix them in the soil.
How might Protococcus help a person who is lost in the woods? What precaution should be taken?
Protococcus grows most abundantly on the shaded side of the tree trunk, which usually is the north side. But consider where the tree is standing. Do not look at one, which is shaded by the other trees on one side.
Is reproduction mostly asexual or sexual among the members of the phylum (Chlorophyta)?
Reproduction varies between asexual or sexual among the members of this phylum. · Protococcus reproduces asexually by fission (spontaneous division of the body into two or more parts each of which grows into a complete organism). · Chlamydomonas reproduces asexually when joining gametes fuse to form a zygote (fertilized egg). · Spirogyra reproduce by conjugation, which takes place between two adjacent cells; a tube forms that connects the two cells, and the contents of one cell pass into the second call—both asexual and sexual reproduction occur, but sexual reproduction occurs in reponse to unfavorable conditions. · Ulothrix reproduces asexually and sexually. · Oedogonium and other similar species reproduce when one filament produces two kinds of gametes; some cells produce sperm cells that are similar to zoospores of Ulothrix in appearance.
How may soil bacteria growing over a period of time solve the problem of too many algae in a greenhouse?
Soil bacteria and molds break down dead plants and animals, changing them too humus. When mixed into a soil, humus makes it porous, holding some air, which is needed by plant roots. Even if algae grow on the surface of humus, they do not exclude all the air.
What is special about the Clamydomonas' cell wall?
The Chlamydomonas' cell wall is composed of a protein and a carbohydrate instead of cellulose.
Would you classify forms as large as the red and brown algae among the Protista? Why or why not?
The authors of the textbook consider classification a matter of convenience. Even on this basis, it would be well for all biologists to agree in classifying organisms, but unfortunately such agreement is not complete. It seems strange to classify plants as large as kelps among the Protista, but their reproduction is more like that of the algae than like that of any other plant.
What gives this phylum (Chlorophyta) its characteristic color?
The chloroplasts give this phylum its characteristic grass-green color.
Discuss direct and indirect methods of increasing human food through algae.
The direct method is for people to eat blue-green algae (such as Nostoc and kelp). The indirect method is to care for a fish pond in such a way that the algae, which are food for small fish, will thrive. Or perhaps algae are eaten by tiny animals, which the fish eat. Lastly, the fish are eaten by man.
Give the typical color associated with each phylum.
The typical color associated with each of the following phyla are as follows: · Chrysophyta—golden or yellowish green · Phaeophyta--brown · Rhodophyta--red · Dinoflagellates—red or pink
