Tutor profile: Maria J.

Name three types of essays and describe the necessary components and purposes of each.

An expository essay is one used to explain or describe something in a balanced and objective manner. It should include an introduction, thesis statement, body paragraphs, and a conclusion. An argumentative essay consists of evidence to support an opinion about a subject or question. It will also include an introduction, a thesis statement, body paragraphs, and a conclusion that summarizes an argument. A third type is a narrative essay which tells a story and is generally more creative than other types. These essays are written around a particular story, theme, or prompt. They follow different formats, but generally include a background (which introduces the theme), character introductions, development of the narrative, and a conclusion.

Name and describe two types of trophic cascade and provide an example in a specific environment.

Trophic cascades occur when one level of the ecosystem is altered resulting in a chain reaction within the food web. This can be a top-down trophic cascade in which top-level predator populations are reduced, impacting lower-levels of the trophic system or a bottom-up trophic cascade where primary producers control higher-levels of the food web. An example of this is on the Pacific Coast of the United States where sea otter populations have been extirpated. This has resulted in a significant population increase of sea urchins that have grazed heavily on kelp, leading to a decline in their abundance.

Identify three factors that affect the rate of plant photosynthesis and describe how they influence the process.

The rate of photosynthesis is influenced by factors such as temperature, wavelength of light, and pH. Though it depends on the plant, generally high temperatures can lead to denatured enzymes and very low temperatures lead to inefficient enzyme binding, both slowing the photosynthetic process. Because plant cells have pigments in their chloroplasts that absorb only certain wavelengths of light, some wavelengths are reflected, resulting in little or no photosynthesis. Other wavelengths are absorbed, causing a molecular chain reaction known as light-dependent photosynthesis. The rate of photosynthesis decreases when pH levels are too high or too low, as it impacts the enzymes ability to function properly.