Eukaryotic cell structure and function

Biology Qs

The primary source of difficulty that researchers and biologists have had in classifying the protists results from the great diversity of the kingdom, including widely varying morphological and reproductive features. Determining when branches in the classification are called for and the degree of relation between the various protests is a difficult task, and currently the determination of classification is made largely on whether the protists are more animal-like (protozoa) or plant-like (algae) in their general appearance and functionality. Developments in DNA and RNA sequencing has led to the belief that this might not actually be the most accurate way to classify the protests from an evolutionary perspective, however, and that other relationships and/or divisions might exist that aren't yet fully understood by researchers. As similarities and differences in RNA molecules are identified, the classification of many protests is likely to change.

2)

Generally, "algae" refers to more plant-like protozoa while "protozoa" refers to those that are more animal-like. Both algae and protozoa can be unicellular, though algae is often multicellular and/or lives in massive colonies. Algae generally create energy through photosynthesis, and while some protozoa such as phytoplankton photosynthesize as well, they often ingest other organic material to use for fuel.

3)

Because all algae photosynthesize, the main difference used for classification of algae is their general morphology, which also relates to the environments where certain phyla are found. Members of the phylum Euglenophyta are motile, and can detect and move to areas of bright light to facilitate better photosynthesis. The phylum Bacillariophyta contains organisms with hard silica shells and not all are motile. Rhodophyta are red in color, generally multicellular, and grow on rocks. Cholorphyta are green and have cellulose walls, and come in unicellular and multicellular varieties. Phaeophyceae are brown algae that include the different kelp varieties; these algae are generally multicellular and live in marine environments.

4)

Protozoa, the more animal-like species of the kingdom of protista, are generally classified by their method of movement. The Sarcodinians move by extending their cytoplasm and bunching up again; amoebas are a well-known example. The Zoomastagina propel themselves with long flagella, while the Ciliophora use small hair-like cilia to propel themselves in any direction. The final classification of the protozoa is the Sporozoa, which cannot actually move by themselves.

5)

Though immobile like most plants, fungi do not photosynthesize or have cellulose walls; their cell walls contain chitin instead. Fungi grow from spores, which are essentially packages of cloned material from the parent organism. Most fungi can also reproduce through sexual reproduction both with the same organism mixing gametes and with reproduction between two separate organisms. The cells of many fungi are primarily copies of each other, without differentiation of organs (except in the fruiting sections of the organism, such as the mushrooms and molds typically visible and known to humans).

6)

Fungi are considered a separate kingdom for several reasons. They are different from plants in their inability to produce energy from sunlight, and in fact most grow in dark places. Unlike animals and many protozoa, they cannot move; unlike most protozoa, they exist almost entirely as multicellular and colonial organisms.

7)

The various classifications of fungi are determined based on their method(s) of reproduction. Zygomycota produce both asexual and sexual spores, while Basidiomycota rarely produce asexually and produce a different type of sexual spore. Ascomycota produce asexual spores, and can also grow buds that break off and form new organsiams as well as growing new and sexually differentiated hyphae as means of reproduction. Deuteromycota have never been observed to reproduce sexually, meaning that the organisms today have been genetically unaltered for millions -- perhaps billions -- of years.

8)

a. Because almost all algae create energy from photosynthesis, it makes sense that algae would be more prevalent during the months when they receive the most sunlight. The warmer months are made warmer by the increased sunlight during the time, which would also encourage algae growth.

b. Many algae species, in addition to performing photosynthesis, are also heterotrophs. Fertilizers contain many compounds that algae are made up of, and the increased use of fertilizers thus provides another food source for many species of algae as well as creating environments that are unfriendly to competing organisms.