10.2: Emotional and Self-Development in Adolescence
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Learning Objectives
By the end of this section, you will be able to:
- Describe the course of emotional development during adolescence
- Discuss the development of self-regulation and emotional intelligence in adolescence
- Describe the development of self-concept and self-esteem in adolescence
- Explain the relevance of body image in adolescence
The alarm sounds early on fifteen-year-old Kenji’s school days. After dressing and eating breakfast, he practices twenty minutes of meditation each morning. Meditation helps clear his mind and focus his energy and emotions. Today he is especially stressed because he has exams in two classes and a paper due in another. As he enters school, Kenji joins friends exchanging fist bumps. During lunch, two of his tablemates start teasing the girl sitting alone at the end of the table. Kenji weighs saying something to them or moving to a different table to avoid trouble. He decides to move. The end of the school day brings a sense of relief, although several hours of homework await.  Kenji’s day is not only busy but full of different motivational states, opportunities for self-regulation, and emotions.
Emotions are the result of a complex set of cognitive, physiological, behavioral, and environmental components and interactions (Ekman et al., 1972, Scherer, 1997). They often motivate behavior, so it’s not surprising that they play a prominent role in adolescent experience. They are important as teens develop an understanding of themselves, including their developing emotional intelligence, self-concept, and self-esteem, and their increased ability to self-regulate.
Emotional Intelligence
For many, adolescence is a time when the social world expands significantly. Not only do teens spend more time outside the home, both in school and at after-school activities, but their new reasoning capabilities, fueled by physical brain developments, make interacting with peers and non family adults a central means of development. They learn to recognize and understand their own emotions, including their triggers, strengths, and weaknesses, and they begin achieving self-awareness . They learn to control impulses, manage stress, and adapt to changing circumstances with the developing skill of self-regulation. They are on their way to achieving emotional intelligence (EI) , the ability to recognize their own and others’ emotional states and feelings, to regulate emotions, and to remain motivated (Goleman, 1998).
Emotionally intelligent individuals can also express their emotions, convey empathy, and maintain their psychological, social, and emotional well-being (Alina et al., 2021). Through social interactions, adolescents learn to express their emotions in appropriate verbal and nonverbal ways. These communication skills in turn help them grow increasingly adept at resolving conflicts and establishing healthy boundaries in their relationships. And emotional intelligence allows adolescents to use emotions as valuable information for problem-solving with rationality and flexibility.
Parents can also help foster emotional intelligence. In particular, the authoritative parenting style has shown a positive relationship with the development of emotional intelligence; while the authoritarian style has been linked with lower emotional intelligence in adolescents (Nastas & Sala, 2012; Nguyen et al., 2020). Recall that authoritative parents are sensitive to their child’s daily needs and emotional states, actively encourage them to express themselves, and help them work through emotional, motivational, and social challenges. These behaviors model the use of emotional intelligence (Reyes-Wapano, 2021).
Emotional intelligence also has long-lasting benefits. Adolescents with high EI have stronger academic performance, are less likely to experience school burnout, have a deeper sense of life satisfaction overall, and tend to view themselves as having the coping skills and capabilities needed to overcome adversity (Collado-Soler, et al., 2023). Next, we’ll look at self-regulation more specifically.
Self-Regulation
The major developments in the frontal lobe and limbic system during adolescence support the growing ability to exert self-regulation , the ability to manage and control behavior and emotions without outside assistance (Muraven & Baumeister, 2000; McClelland et al., 2017). This skill allows us to change or inhibit certain thoughts, emotions, and behaviors to achieve better outcomes (Baumeister & Alquist, 2009; Moilanen et al., 2015). Related abilities include task persistence, delayed gratification, self-monitoring, self-reward for progress, management of frustration and distress, and the capacity to seek help when needed (Murray & Rosanbalm, 2017) (Figure 10.5).
Self-regulation increases steadily across adolescence, shaped in part by parental and peer influences (Farley & Kim-Spoon, 2014). Caregivers regulate a child’s behavior and provide an initial set of expectations and guidance. As an adolescent develops and exhibits self-control, caregivers can reduce the amount of explicit regulation support they provide. A good-quality parent-adolescent relationship predicts good self-regulatory skills in the developing teen. However, this influence can work both ways, and a teen having difficulty regulating their emotions or behaviors will likely contribute to a difficult parent-teen relationship. Caregivers can model many of the same emotion regulation and self-regulation techniques you’ve learned about to help adolescents improve their own regulation skills. However, they can also begin to reduce their support while offering helpful reminders of emotion-regulation tools when frustration levels seem too high (Murray & Rosanbalm, 2017). For example, if a teen seems frustrated with a challenging homework assignment and is about to give up, a caregiver might remind them of the value of taking a short break, eating a snack, and then breaking the homework down into smaller steps.
Positive peer relationships are also an important predictor for, and outcome of, good self-regulation skills, including emotional self-regulation. This influence also goes both ways. Teens who exhibit strong self-regulation skills have been found to form caring, close friendships with peers. In turn, these close peer relations can help to support and reinforce self-regulation (Scholte & Van Aken, 2006; Meldrum & Hay, 2012).
Self-Concept and Self-Esteem
Our self-concept is the mental image or representation we have of ourselves, the cognitive portion of identity. During adolescence, it goes beyond the tangible descriptions of middle childhood (like “dog lover” or “middle child”) to encompass abstract qualities like “fair” and “loyal.” Teens develop their self-concept by comparing their qualities with others’ characteristics and abilities (Harter, 2006). For example, a fifteen-year-old might pride herself on being “trustworthy” and “hard working.” She judges herself to be as trustworthy as her best friend; she believes she works far harder than most peers in her classes.
The dimensions of the self-concept, as outlined by Harter (1983), are scholastic competence, social acceptance, athletic competence, physical appearance, behavioral conduct, and self-acceptance. By the end of adolescence, they have been built into a coherent whole that informs an overall identity . Longitudinal research on children suggests self-concept is relatively stable from middle childhood to middle adolescence (Kuzucu, et al., 2014), which may be a result of peer perception and niche-picking. For example, once a ten-year-old demonstrates athletic prowess, peers will likely continue to react to this by encouraging the child to join their team during athletic games, reinforcing this part of the self-concept (peer perception). Likewise, someone who discovers they are good at a skill or activity will likely seek situations that support it (niche-picking). Encouraging adolescents to try out new opportunities can help them to discover new interests, skills, and parts of their self-concept.
If self-concept is the cognitive understanding of our self, self-esteem is the motivational and emotional piece (Harter & Whitesell, 2003). Numerous studies have found a link between low self-esteem and risks of developing depression (Masselink et al., 2018; Nelis & Bukowski, 2019). Adolescents with low self-esteem have been found to have a smaller group of friends who can offer social support, and to show social adjustment problems (Marshall et al., 2014).
Overall, however, self-esteem rises over the course of adolescence, and the factors most likely to predict positive self-esteem at a later age include positive parental relationships, healthy physical activity, and positive body image (Birkeland et al., 2012). No clear sex differences in average levels of self-esteem have been reported (Masselink et al., 2017). Healthy self-esteem and a sense of mastery can be enhanced by practicing strategies like mindfulness and self-compassion (Marshall et al., 2015). Positive reinforcement, supportive feedback, and encouragement of self-discovery and physical activity can also help.
Body Image
Physical appearance is one of the main dimensions of self-concept. Our mental image or representation of our body is our body image and is closely related to self-esteem. Given the rapid physical development of adolescence, and the social environment’s ever-changing response to these developments, body image becomes a major psychological feature of the adolescent experience (Figure 10.6). If someone’s body image is healthy, their mental representation of their body size and shape is healthy and positive. An unhealthy body image is just the opposite: the person’s view of their body does not match objective reality and contains negative self-evaluations (Engeln, 2017; Voelker et al., 2015).
All adolescents are susceptible to the development of an unhealthy body image. The timing of puberty is particularly influential to this because cultural ideals for physical beauty can heighten a teen’s sense of being on time or off-track for physical development relative to peers and cultural expectations. For early-maturing adolescent females in the United States, for example, breast and hip development may differ from beauty standards of a thin or athletic body shape (Lee & Styne, 2013; Uhlmann et al., 2018). For both adolescent males and females, early maturation is linked to a variety of negative psychological, social, and health outcomes (Hoyt et al., 2020). This includes being more likely to engage in risky health behaviors like experimenting with drugs and higher risks of depressive symptoms both in adolescence and in young adulthood.
Research on teen body image highlights the interplay among media exposure, cultural values, and individual factors shaping body image perceptions in different racial and ethnic groups. For instance, among Latina girls living in the United States, frequent viewing of mainstream television is linked to decreased body satisfaction, while viewing of Black-oriented television improves body satisfaction for Latina girls who have adopted more U.S. cultural beliefs (Schooler, 2008). Black adolescent girls’ exposure to stereotypical media images of Black women predicted more negative interpretations and impacts of these images, particularly when racial identity was low (Jean et al., 2022). This may indicate that having a strong racial identity may protect some adolescents from the harmful influences of negative media images on body image. Asian American girls’ body image perceptions are influenced by both mainstream White culture and Asian culture, which can lead to disordered eating and a lower likelihood of receiving treatment for eating disorders (Javier et al., 2019).  Overall, many contextual influences and individual differences interact to shape an adolescent’s body image.
Link to Learning
Watch this clip to learn more about a school in East London is the first to start lessons using a Body Confidence Campaign Toolkit to help schoolchildren develop healthy confidence in their bodies.
Information that contributes to adolescents’ body image comes from peers, family members, television and movies, advertisements, and social media. The Surgeon General of the United States recently published an advisory for parents, educators, and practitioners warning of the dangers of social media use by adolescents (Office of the U.S. Surgeon General, 2023). It notes a particular concern for adolescent girls, citing an increase in the risk for developing a negative body image and eating disorders (Holland & Tiggemann, 2016). Parents’ words, attitudes, and behaviors related to health, diet, exercise, and physical development contribute to teens’ sense of their physical selves, and mothers play a significant role in their teenage daughters’ views (Helfert & Warschburger, 2011; Neumark-Sztainer, et al., 2010). Peers provide feedback about which body types are valued and how someone is doing relative to those standards.
Life Hacks: Promoting a Healthy Body Image
What can we do to encourage a healthy body image in adolescents? Caregivers can start with developing their own healthy body image so they can better model healthy behaviors, emotions, and thoughts for their children (Jensen et al., 2018). Similarly, adults can embrace and encourage body diversity, the idea that our physical diversity is good, and that people all have different strengths. Further, teaching children about media literacy and critically analyzing media messages builds a good set of lifelong skills, helping children counteract negative information about beauty ideals as represented in the media. Finally, one counter intuitive but important recommendation is to avoid saying positive things about someone based solely on notions of physical beauty. By praising someone for their physicality alone, adults are inadvertently signaling that this matters above other characteristics like personality, intelligence, or talents. Instead, praise desirable characteristics and effort.
Here are some other tips for promoting healthy body image:
- Avoid making comments about your weight or the weight of others, especially around children and teens (Neumark-Sztainer et al., 2010). In addition, avoid making negative comments about your own body.
- Promote media literacy by talking about media representations that may model an unhealthy body image. If a character in a show says negative things about their own body or another person’s body, caregivers can use that as an opportunity to talk about how to interpret media messages.
- Engage in healthy behaviors at home to maintain a healthy body, including a good diet and exercise habits. Be careful though—it’s better to frame your workout and nutrition choices as being to “stay strong” or “stay healthy” rather than talk about specific beauty or weight goals.
- If you catch yourself saying something negative about your body, other bodies, or promoting an unhealthy diet—make it right. You can point out that you made a mistake, apologize, and note that you. should do better with being body positive—for your own well-being and the well-being of others.
Link to Learning
Watch this clip of actors depicting a non-judgmental parent-teen conversation about body positivity, followed by some tips about having such conversations from a nutritionist.
References
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14.7: Employee Behavior Outside of Work
- Discuss laws related to employee behavior outside of the workplace
- Discuss laws related to employee social media use
Federal laws related to employee behavior include the National Labor Relations Act (discussed below) and the Occupational Safety and Health (OSH) Act (discussed in Module 14: Safety, Health, and Risk Management), as well as the laws that apply to human conduct in general. However, an employer’s ability to control or discipline an employee’s behavior outside the workplace is typically regulated by state law. Thus, it is essential to know the laws of your state.
In general, state laws variously protect employee’s right to participate in political activities, to volunteer for civic organizations and to smoke or drink outside working hours. The laws also detail the circumstances under which an employer can restrict or modify policies based on lawful off-duty behavior.
For example, California law, which applies to all employers, protects an employee’s right to engage in political activity and specifies that employers are prohibited from controlling or influencing political activities or affiliations or restricting employees participation in political activities. Illinois protects an employee’s right to off-duty use of lawful products but also allows employers to “offer, impose or implement a health, disability or life insurance policy that makes distinctions between employees for the type of coverage or price of coverage based on the employee’s use of lawful products, under certain circumstances.”
Consider developing and working through relevant scenarios using SimplicityHR’s “ Can you fire an employee for their off-duty behavior ?” article as a prompt.
Employee Social Media Use
Employee use of social media may or may not be protected as “concerted activity” by the National Labor Relations Act. The National Labor Relations Board (NLRB) notes that an employee has “the right to act with co-workers to address work-related issues. Examples include: talking with one or more co-workers about your wages and benefits or other working conditions, circulating a petition asking for better hours, participating in a concerted refusal to work in unsafe conditions, openly talking about your pay and benefits, and joining with co-workers to talk directly to your employer, to a government agency, or to the media about problems in your workplace.” [1]
An employer “cannot discharge, discipline, or threaten [an employee] for, or coercively question you about,” this type of activity. However, making statements that are “egregiously offensive or knowingly and maliciously false,” or “publicly disparaging your employer’s products or services without relating your complaints to any labor controversy” is not protected concerted activity.
For perspective on what is protected and not protected activity, refer to the NLRB’s interactive map and summaries of recent cases: Protected Concerted Activity.
SimplicityHR reports that claims of wrongful termination (retaliation) due to online remarks is “the leading type of claim filed with the Equal Employment Opportunity Commission.” [2]
House Rule 537— Social Networking Online Protection Ac t (SNOPA), introduced in the House on 02/06/2013 but parked at the Subcommittee on Workforce Protections since 4/23/2013.
The California Peculiarities Employment Law Blog notes that using social media in hiring decisions can expose an employer to liability. [3] California’s AB 1844 prohibits employers from requesting an applicant’s log-in information, asking applicants to “friend” other employees, or asking an applicant’s “friends” to disclose what the applicant has posted on social media. Although employers are not specifically prohibited from accessing publicly available information, the author’s advise against it, noting it could be a “discrimination trap,” since social media reveals personal information that would be illegal to ask during the hiring process.
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Concerted Activity
." National Labor Relations Board. Accessed September 12, 2019. ↵
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Can You Fire and Employee for Their Off-Duty Behavior?
" Simplicity HR. Accessed September 12, 2019. ↵
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Lubeley, Aaron R. and Candace Bertoldi "
She Posted What? Employers Face Increased Legal Scrutiny for Using Social Media in Hiring Decisions.
" Seyfarth Shaw. April 17, 2013. Accessed September 12, 2019. ↵


12.3: Writing for Success- Outlining
LEARNING OBJECTIVES
By the end of this section, you will be able to:
- Identify the steps in constructing an outline.
- Construct a topic outline and a sentence outline.
Your prewriting activities and readings have helped you gather information for your assignment. The more you sort through the pieces of information you found, the more you will begin to see the connections between them. Patterns and gaps may begin to stand out. But only when you start to organize your ideas will you be able to translate your raw insights into a form that will communicate meaning to your audience.
Tip
Longer papers require more reading and planning than shorter papers do. Most writers discover that the more they know about a topic, the more they can write about it with intelligence and interest.
Organizing Ideas
When you write, you need to organize your ideas in an order that makes sense.  In some courses, the only direct contact you may have with your instructor is through the assignments you write for the course. You can make a good impression by spending time ordering your ideas.
Order refers to your choice of what to present first, second, third, and so on in your writing. The order you pick closely relates to your purpose for writing that particular assignment. For example, when telling a story, it may be important to first describe the background for the action. Or you may need to first describe a 3-D movie projector or a television studio to help readers visualize the setting and scene. You may want to group your support effectively to convince readers that your point of view on an issue is well reasoned and worthy of belief.
In longer pieces of writing, you may organize different parts in different ways so that your purpose stands out clearly and all parts of the paper work together to consistently develop your main point.
Methods of Organizing Writing
The three common methods of organizing writing are chronological order , spatial order , and order of importance . You will learn more about these in Chapter 8 “Writing Essays: From Start to Finish”; however, you need to keep these methods of organization in mind as you plan how to arrange the information you have gathered in an outline. An outline is a written plan that serves as a skeleton for the paragraphs you write. Later, when you draft paragraphs in the next stage of the writing process, you will add support to create “flesh” and “muscle” for your assignment.
When you write, your goal is not only to complete an assignment but also to write for a specific purpose—perhaps to inform, to explain, to persuade, or for a combination of these purposes. Your purpose for writing should always be in the back of your mind, because it will help you decide which pieces of information belong together and how you will order them. In other words, choose the order that will most effectively fit your purpose and support your main point.
Table 7.1 “Order versus Purpose” shows the connection between order and purpose.
Table 7.1 Order versus Purpose
| Order | Purpose |
|---|---|
| Chronological Order | To explain the history of an event or a topic |
| To tell a story or relate an experience | |
| To explain how to do or make something | |
| To explain the steps in a process | |
| Spatial Order | To help readers visualize something as you want them to see it |
| To create a main impression using the senses (sight, touch, taste, smell, and sound) | |
| Order of Importance | To persuade or convince |
| To rank items by their importance, benefit, or significance |
Writing a Thesis Statement
One legitimate question readers always ask about a piece of writing is “What is the big idea?” (You may even ask this question when you are the reader, critically reading an assignment or another document.) Every nonfiction writing task—from the short essay to the ten-page term paper to the lengthy senior thesis—needs a big idea, or a controlling idea, as the spine for the work. The controlling idea is the main idea that you want to present and develop.
Tip
For a longer piece of writing, the main idea should be broader than the main idea for a shorter piece of writing. Be sure to frame a main idea that is appropriate for the length of the assignment. Ask yourself, “How many pages will it take for me to explain and explore this main idea in detail?” Be reasonable with your estimate. Then expand or trim it to fit the required length.
The big idea, or controlling idea, you want to present in an essay is expressed in a thesis statement . A thesis statement is often one sentence long, and it states your point of view. The thesis statement is not the topic of the piece of writing but rather what you have to say about that topic and what is important to tell readers.
Table 7.2 “Topics and Thesis Statements” compares topics and thesis statements.
Table 7.2 Topics and Thesis Statements
| Topic | Thesis Statement |
|---|---|
| Music piracy | The recording industry fears that so-called music piracy will diminish profits and destroy markets, but it cannot be more wrong. |
| The number of consumer choices available in media gear | Everyone wants the newest and the best digital technology, but the choices are extensive, and the specifications are often confusing. |
| E-books and online newspapers increasing their share of the market | E-books and online newspapers will bring an end to print media as we know it. |
| Online education and the new media | Someday, students and teachers will send avatars to their online classrooms. |
The first thesis statement you write will be a preliminary thesis statement, or a working thesis statement . You will need it when you begin to outline your assignment as a way to organize it. As you continue to develop the arrangement, you can limit your working thesis statement if it is too broad or expand it if it proves too narrow for what you want to say.
Tip
You will make several attempts before you devise a working thesis statement that you think is effective. Each draft of the thesis statement will bring you closer to the wording that expresses your meaning exactly.
Writing an Outline
For an essay question on a test or a brief oral presentation in class, all you may need to prepare is a short, informal outline in which you jot down key ideas in the order you will present them. This kind of outline reminds you to stay focused in a stressful situation and to include all the good ideas that help you explain or prove your point.
For a longer assignment, like an essay or a research paper, many college instructors require students to submit a formal outline before writing a major paper as a way to be sure you are on the right track and are working in an organized manner. A formal outline is a detailed guide that shows how all your supporting ideas relate to each other. It helps you distinguish between ideas that are of equal importance and ones that are of lesser importance. You build your paper based on the framework created by the outline.
Tip
Instructors may also require you to submit an outline with your final draft to check the direction of the assignment and the logic of your final draft. If you are required to submit an outline with the final draft of a paper, remember to revise the outline to reflect any changes you made while writing the paper.
There are two types of formal outlines: the topic outline and the sentence outline. You format both types of formal outlines in the same way.
- Place your introduction and thesis statement at the beginning, under roman numeral I.
- Use roman numerals (II, III, IV, V, etc.) to identify main points that develop the thesis statement.
- Use capital letters (A, B, C, D, etc.) to divide your main points into parts.
- Use arabic numerals (1, 2, 3, 4, 5, etc.) if you need to subdivide any As, Bs, or Cs into smaller parts.
- End with the final roman numeral expressing your idea for your conclusion.
Here is what the skeleton of a traditional formal outline looks like. The indention helps clarify how the ideas are related.
- IntroductionThesis statement
-
Main point 1 →
becomes the topic sentence of body paragraph 1
-
Supporting detail →
becomes a support sentence of body paragraph 1
- Subpoint
- Subpoint
-
Supporting detail
- Subpoint
- Subpoint
-
Supporting detail
- Subpoint
- Subpoint
-
Supporting detail →
becomes a support sentence of body paragraph 1
-
Main point 2 →
becomes the topic sentence of body paragraph 2
- Supporting detail
- Supporting detail
- Supporting detail
-
Main point 3 →
becomes the topic sentence of body paragraph 3
- Supporting detail
- Supporting detail
- Supporting detail
- Conclusion
Tip
In an outline, any supporting detail can be developed with subpoints. For simplicity, the model shows them only under the first main point.
Tip
Formal outlines are often quite rigid in their organization. As many instructors will specify, you cannot subdivide one point if it is only one part. For example, for every roman numeral I, there must be a For every A, there must be a B. For every arabic numeral 1, there must be a 2. See for yourself on the sample outlines that follow.
Constructing Topic Outlines
A topic outline is the same as a sentence outline except you use words or phrases instead of complete sentences. Words and phrases keep the outline short and easier to comprehend. All the headings, however, must be written in parallel structure. (For more information on parallel structure, see “Refining Your Writing: How Do I Improve My Writing Technique?”.)
Here is the topic outline that Mariah constructed for the essay she is developing. Her purpose is to inform, and her audience is a general audience of her fellow college students. Notice how Mariah begins with her thesis statement. She then arranges her main points and supporting details in outline form using short phrases in parallel grammatical structure.
Checklist
Writing an Effective Topic Outline
This checklist can help you write an effective topic outline for your assignment. It will also help you discover where you may need to do additional reading or prewriting.
- Do I have a controlling idea that guides the development of the entire piece of writing?
- Do I have three or more main points that I want to make in this piece of writing? Does each main point connect to my controlling idea?
- Is my outline in the best order—chronological order, spatial order, or order of importance—for me to present my main points? Will this order help me get my main point across?
- Do I have supporting details that will help me inform, explain, or prove my main points?
- Do I need to add more support? If so, where?
- Do I need to make any adjustments in my working thesis statement before I consider it the final version?
Writing at Work
Word processing programs generally have an automatic numbering feature that can be used to prepare outlines. This feature automatically sets indents and lets you use the tab key to arrange information just as you would in an outline. Although in business this style might be acceptable, in college your instructor might have different requirements. Teach yourself how to customize the levels of outline numbering in your word-processing program to fit your instructor’s preferences.
Constructing Sentence Outlines
A sentence outline is the same as a topic outline except you use complete sentences instead of words or phrases. Complete sentences create clarity and can advance you one step closer to a draft in the writing process.
Here is the sentence outline that Mariah constructed for the essay she is developing.
Tip
The information compiled under each roman numeral will become a paragraph in your final paper. In the previous example, the outline follows the standard five-paragraph essay arrangement, but longer essays will require more paragraphs and thus more roman numerals. If you think that a paragraph might become too long or stringy, add an additional paragraph to your outline, renumbering the main points appropriately.
Writing at Work
PowerPoint presentations, used both in schools and in the workplace, are organized in a way very similar to formal outlines. PowerPoint presentations often contain information in the form of talking points that the presenter develops with more details and examples than are contained on the PowerPoint slide.
Key Takeaways
- Writers must put their ideas in order so the assignment makes sense. The most common orders are chronological order, spatial order, and order of importance.
- After gathering and evaluating the information you found for your essay, the next step is to write a working, or preliminary, thesis statement.
- The working thesis statement expresses the main idea that you want to develop in the entire piece of writing. It can be modified as you continue the writing process.
- Effective writers prepare a formal outline to organize their main ideas and supporting details in the order they will be presented.
- A topic outline uses words and phrases to express the ideas.
- A sentence outline uses complete sentences to express the ideas.
- The writer’s thesis statement begins the outline, and the outline ends with suggestions for the concluding paragraph.
Exercises
1. Using the topic you selected in “Apply Prewriting Models,” develop a working thesis statement that states your controlling idea for the piece of writing you are doing. On a sheet of paper, write your working thesis statement.
2. Using the working thesis statement you wrote in #1 and the reading you did in “Apply Prewriting Models,” construct a topic outline for your essay. Be sure to observe correct outline form, including correct indentions and the use of Roman and arabic numerals and capital letters. Please share with a classmate and compare your outline. Point out areas of interest from their outline and what you would like to learn more about.
3. Expand the topic outline you prepared #2 to make it a sentence outline. In this outline, be sure to include multiple supporting points for your main topic even if your topic outline does not contain them. Be sure to observe correct outline form, including correct indentions and the use of Roman and arabic numerals and capital letters.
Contributors and Attributions
- Successful Writing. Authored by : Anonymous. Provided by : Anonymous. Located at : http://2012books.lardbucket.org/books/english-for-business-success/ . License : CC BY-NC-SA: Attribution-NonCommercial-ShareAlike


8.4: Understanding GNU’s General Public Licence—A Legal Bastion
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“The [GNU’s] GPL has become a powerful force in the information age. A hack on the copyright system, it turns the concept of copyright upside down, creates a whole community cooperating around the world and enables the development of software by the people, of the people and for the people. Many new licenses were modeled after or influenced by the GPL”. – Tai (2001)
Stallman founded the GNU Project in 1984 to create a free software operating system. GNU sought to replace the proprietary Unix platform which AT&T, with the help of Sun, was seeking to establish as the monolithic operating system for the industry. Hence the recursive name of the project, “GNU is Not Unix” (Free Software Foundation, Inc. 2007). In 1985, Stallman founded the Free Software Foundation, Inc. (FSF), a non-profit organization dedicated to supporting the free software movement in general, and the GNU Project in particular. Between 1984 and 1988, GNU and the FSF developed special licences for specific GNU programs (Tai, 2001). This licensing approach was eventually consolidated in February 1989 as the GNU General Public Licence (GPL) Version 1 (Tai, 2001). The GPL became the gold standard for ensuring the future of freely sourced software for a variety of reasons. First, the GPL protected user rights to free software by delineating responsibilities with regard to distribution, copying and modification of the software. While similar to earlier licences, the GPL was unique in that:
if you distribute[d] copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must tell them their rights (Free Software Foundation, Inc., February 1989).
Here, Stallman ensured that any distributions would carry the original rights to distribute, copy and modify. This was further specified in Section 2.b stating that any secondary programming containing the original free work “be licensed at no charge to all third parties under the terms of this General Public License” (Free Software Foundation, Inc., February 1989). Thus, the GPL effectively prevented proprietary commercialization of the free programs. As opposed to “copyright”, GPL became commonly known as “copy left.”11
From the programmers’ perspective, another critical aspect of GPL was that the licence ensured any distribution, copying, or modification would always make clear that the originators of the software did not provide any type of warranty with regard to the software. The GPL was updated as Version 2 in 1991 along with the release of a licence variation called the Library GPL. The second version of GPL included a section to counteract claims that users were unable to fulfill the GPL licence and were therefore not bound by the terms. GPL Version 3 is currently under discussion. Some new aspects have to deal with digital rights management issues, as high-lighted in legal cases against peer-to-peer sharing of copyrighted materials.
Two additional licensing documents connected to the GPL are the Library GPL, or as it’s now called, the GNU Lesser General Public Licence (LGPL) and the Free Documentation Licence (FDL). The LGPL was originally released in 1991 and updated in 1999 (Free Software Foundation, Inc., 1991/1999). It was developed to allow non-free software to interface with free software. Previously, under the terms of the original GPL, such an interaction would have made the “using” non-free software subject to the GPL (Free Software Foundation, Inc., 1991/1999). The FDL was added to the GPL legal library in November 2000. It was later revised in 2001 and 2002. The original intention was to align manual licensing requirements for GPL software with the GPL, but the licence scope is not limited to free software manuals. The FDL applies to “any manual or other work, in any medium” and ensures the work has “a world-wide, royalty-free licence, unlimited in duration” as long as the FDL terms are met (Free Software Foundation, Inc., November 2002). Similar to the GPL, with regard to the work in question, the FDL grants:
everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially … this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others (Free Software Foundation, Inc., November 2002).
Through the GPL licences, Stallman and the FSF legally and successfully entrenched the ethical obligation to keep free software and any derivative works free. Ultimately, many subsequent agreements, like those among the 58 licences approved by the OSI (Open Source Initiative, 2006b) or The Debian Social Contract Version 1.0 (Software in the Public Interest, 1997) owe a great deal to the GPL. Stallman and Moglen said this of GPL in 2005:
The GPL is employed by tens of thousands of software projects around the world, of which the Free Software Foundation’s GNU system is a tiny fraction. The GNU system, when combined with Linus Torvalds’ Linux—which has evolved into a flexible, highly portable, industry-leading operating system kernel—along with Samba, MySQL, and other GPL’d programs, offers superior reliability and adaptability to Microsoft’s operating systems, at nominal cost. GPL’d software runs on or is embedded in devices ranging from cellphones, PDAs and home networking appliances to mainframes and supercomputing clusters. Independent software developers around the world, as well as every large corporate IT buyer and seller, and a surprisingly large proportion of individual users, interact with the GPL.


12.4: Finite-length Transmission Lines
A transmission line of infinite length is an interesting abstraction, but physically impossible. All transmission lines have some finite length, and as such do not behave precisely the same as an infinite line. If that piece of 50 Ω “RG-58/U” cable I measured with an ohmmeter years ago had been infinitely long, I actually would have been able to measure 50 Ω worth of resistance between the inner and outer conductors. But it was not infinite in length, and so it measured as “open” (infinite resistance).
Nonetheless, the characteristic impedance rating of a transmission line is important even when dealing with limited lengths. An older term for characteristic impedance, which I like for its descriptive value, is surge impedance . If a transient voltage (a “surge”) is applied to the end of a transmission line, the line will draw a current proportional to the surge voltage magnitude divided by the line’s surge impedance (I=E/Z). This simple, Ohm’s Law relationship between current and voltage will hold true for a limited period of time, but not indefinitely.
If the end of a transmission line is open-circuited—that is, left unconnected—the current “wave” propagating down the line’s length will have to stop at the end, since electrons cannot flow where there is no continuing path. This abrupt cessation of current at the line’s end causes a “pile-up” to occur along the length of the transmission line, as the electrons successively find no place to go. Imagine a train traveling down the track with slack between the rail car couplings: if the lead car suddenly crashes into an immovable barricade, it will come to a stop, causing the one behind it to come to a stop as soon as the first coupling slack is taken up, which causes the next rail car to stop as soon as the next coupling’s slack is taken up, and so on until the last rail car stops. The train does not come to a halt together, but rather in sequence from first car to last: (Figure below)
Reflected wave.
A signal propagating from the source-end of a transmission line to the load-end is called an incident wave . The propagation of a signal from load-end to source-end (such as what happened in this example with current encountering the end of an open-circuited transmission line) is called a reflected wave .
When this electron “pile-up” propagates back to the battery, current at the battery ceases, and the line acts as a simple open circuit. All this happens very quickly for transmission lines of reasonable length, and so an ohmmeter measurement of the line never reveals the brief time period where the line actually behaves as a resistor. For a mile-long cable with a velocity factor of 0.66 (signal propagation velocity is 66% of light speed, or 122,760 miles per second), it takes only 1/122,760 of a second (8.146 microseconds) for a signal to travel from one end to the other. For the current signal to reach the line’s end and “reflect” back to the source, the round-trip time is twice this figure, or 16.292 µs.
High-speed measurement instruments are able to detect this transit time from source to line-end and back to source again, and may be used for the purpose of determining a cable’s length. This technique may also be used for determining the presence and location of a break in one or both of the cable’s conductors, since a current will “reflect” off the wire break just as it will off the end of an open-circuited cable. Instruments designed for such purposes are called time-domain reflectometers (TDRs). The basic principle is identical to that of sonar range-finding: generating a sound pulse and measuring the time it takes for the echo to return.
A similar phenomenon takes place if the end of a transmission line is short-circuited: when the voltage wave-front reaches the end of the line, it is reflected back to the source, because voltage cannot exist between two electrically common points. When this reflected wave reaches the source, the source sees the entire transmission line as a short-circuit. Again, this happens as quickly as the signal can propagate round-trip down and up the transmission line at whatever velocity allowed by the dielectric material between the line’s conductors.
A simple experiment illustrates the phenomenon of wave reflection in transmission lines. Take a length of rope by one end and “whip” it with a rapid up-and-down motion of the wrist. A wave may be seen traveling down the rope’s length until it dissipates entirely due to friction: (Figure below)
Lossy transmission line.
This is analogous to a long transmission line with internal loss: the signal steadily grows weaker as it propagates down the line’s length, never reflecting back to the source. However, if the far end of the rope is secured to a solid object at a point prior to the incident wave’s total dissipation, a second wave will be reflected back to your hand: (Figure below)
Reflected wave.
Usually, the purpose of a transmission line is to convey electrical energy from one point to another. Even if the signals are intended for information only, and not to power some significant load device, the ideal situation would be for all of the original signal energy to travel from the source to the load, and then be completely absorbed or dissipated by the load for maximum signal-to-noise ratio. Thus, “loss” along the length of a transmission line is undesirable, as are reflected waves, since reflected energy is energy not delivered to the end device.
Reflections may be eliminated from the transmission line if the load’s impedance exactly equals the characteristic (“surge”) impedance of the line. For example, a 50 Ω coaxial cable that is either open-circuited or short-circuited will reflect all of the incident energy back to the source. However, if a 50 Ω resistor is connected at the end of the cable, there will be no reflected energy, all signal energy being dissipated by the resistor.
This makes perfect sense if we return to our hypothetical, infinite-length transmission line example. A transmission line of 50 Ω characteristic impedance and infinite length behaves exactly like a 50 Ω resistance as measured from one end. (Figure below)
If we cut this line to some finite length, it will behave as a 50 Ω resistor to a constant source of DC voltage for a brief time, but then behave like an open- or a short-circuit, depending on what condition we leave the cut end of the line: open (Figure below)
or shorted. (Figure below)
However, if we terminate the line with a 50 Ω resistor, the line will once again behave as a 50 Ω resistor, indefinitely: the same as if it were of infinite length again: (Figure below)
Infinite transmission line looks like resistor.
One mile transmission. Shorted transmission line. Line terminated in characteristic impedance.In essence, a terminating resistor matching the natural impedance of the transmission line makes the line “appear” infinitely long from the perspective of the source, because a resistor has the ability to eternally dissipate energy in the same way a transmission line of infinite length is able to eternally absorb energy.
Reflected waves will also manifest if the terminating resistance isn’t precisely equal to the characteristic impedance of the transmission line, not just if the line is left unconnected (open) or jumpered (shorted). Though the energy reflection will not be total with a terminating impedance of slight mismatch, it will be partial. This happens whether or not the terminating resistance is greater or less than the line’s characteristic impedance.
Re-reflections of a reflected wave may also occur at the source end of a transmission line, if the source’s internal impedance (Thevenin equivalent impedance) is not exactly equal to the line’s characteristic impedance. A reflected wave returning back to the source will be dissipated entirely if the source impedance matches the line’s, but will be reflected back toward the line end like another incident wave, at least partially, if the source impedance does not match the line. This type of reflection may be particularly troublesome, as it makes it appear that the source has transmitted another pulse.
Review
- Characteristic impedance is also known as surge impedance , due to the temporarily resistive behavior of any length transmission line.
- A finite-length transmission line will appear to a DC voltage source as a constant resistance for some short time, then as whatever impedance the line is terminated with. Therefore, an open-ended cable simply reads “open” when measured with an ohmmeter, and “shorted” when its end is short-circuited.
- A transient (“surge”) signal applied to one end of an open-ended or short-circuited transmission line will “reflect” off the far end of the line as a secondary wave. A signal traveling on a transmission line from source to load is called an incident wave ; a signal “bounced” off the end of a transmission line, traveling from load to source, is called a reflected wave .
- Reflected waves will also appear in transmission lines terminated by resistors not precisely matching the characteristic impedance.
- A finite-length transmission line may be made to appear infinite in length if terminated by a resistor of equal value to the line’s characteristic impedance. This eliminates all signal reflections.
- A reflected wave may become re-reflected off the source-end of a transmission line if the source’s internal impedance does not match the line’s characteristic impedance. This re-reflected wave will appear, of course, like another pulse signal transmitted from the source.


15.5: Community Ecology
By the end of this section, you will be able to do the following:
- Discuss the predator-prey cycle
- Give examples of defenses against predation and herbivory
- Describe the competitive exclusion principle
- Give examples of symbiotic relationships between species
- Describe community structure and succession
In general, populations of one species never live in isolation from populations of other species. The interacting populations occupying a given habitat form an ecological community. The number of species occupying the same habitat and their relative abundance is known as the diversity of the community. Areas with low species diversity, such as the glaciers of Antarctica, still contain a wide variety of living organisms, whereas the diversity of tropical rainforests is so great that it cannot be accurately assessed. Scientists study ecology at the community level to understand how species interact with each other and compete for the same resources.
Predation and Herbivory
Perhaps the classical example of species interaction is the predator-prey relationship. The narrowest definition of the predator-prey interaction describes individuals of one population that kill and then consume the individuals of another population. Population sizes of predators and prey in a community are not constant over time, and they may vary in cycles that appear to be related. The most often cited example of predator-prey population dynamics is seen in the cycling of the lynx (predator) and the snowshoe hare (prey), using 100 years of trapping data from North America (Figure \(\PageIndex{1}\)). This cycling of predator and prey population sizes has a period of approximately ten years, with the predator population lagging one to two years behind the prey population. An apparent explanation for this pattern is that as the hare numbers increase, there is more food available for the lynx, allowing the lynx population to increase as well. When the lynx population grows to a threshold level, however, they kill so many hares that hare numbers begin to decline, followed by a decline in the lynx population because of scarcity of food. When the lynx population is low, the hare population size begins to increase due, in part, to low predation pressure, starting the cycle anew.
Defense Mechanisms against Predation and Herbivory
Predation and predator avoidance are strong selective agents. Any heritable character that allows an individual of a prey population to better evade its predators will be represented in greater numbers in later generations. Likewise, traits that allow a predator to more efficiently locate and capture its prey will lead to a greater number of offspring and an increase in the commonness of the trait within the population. Such ecological relationships between specific populations lead to adaptations that are driven by reciprocal evolutionary responses in those populations. Species have evolved numerous mechanisms to escape predation and herbivory (the consumption of plants for food). Defenses may be mechanical, chemical, physical, or behavioral.
Mechanical defenses, such as the presence of armor in animals or thorns in plants, discourage predation and herbivory by discouraging physical contact (Figure \(\PageIndex{2}\) a ). Many animals produce or obtain chemical defenses from plants and store them to prevent predation. Many plant species produce secondary plant compounds that serve no function for the plant except that they are toxic to animals and discourage consumption. For example, the foxglove produces several compounds, including digitalis, that are extremely toxic when eaten (Figure \(\PageIndex{2}\) b ). (Biomedical scientists have purposed the chemical produced by foxglove as a heart medication, which has saved lives for many decades.)
Many species use their body shape and coloration to avoid being detected by predators. The tropical walking stick is an insect with the coloration and body shape of a twig, which makes it very hard to see when it is stationary against a background of real twigs (Figure \(\PageIndex{3}\) a ). In another example, the chameleon can change its color to match its surroundings (Figure \(\PageIndex{3}\) b ).
Some species use coloration as a way of warning predators that they are distasteful or poisonous. For example, the monarch butterfly caterpillar sequesters poisons from its food (plants and milkweeds) to make itself poisonous or distasteful to potential predators. The caterpillar is bright yellow and black to advertise its toxicity. The caterpillar is also able to pass the sequestered toxins on to the adult monarch, which is also dramatically colored black and red as a warning to potential predators. Fire-bellied toads produce toxins that make them distasteful to their potential predators. They have bright red or orange coloration on their bellies, which they display to a potential predator to advertise their poisonous nature and discourage an attack. These are only two examples of warning coloration, which is a relatively common adaptation. Warning coloration only works if a predator uses eyesight to locate prey and can learn—a naïve predator must experience the negative consequences of eating one before it will avoid other similarly colored individuals (Figure \(\PageIndex{4}\)).
While some predators learn to avoid eating certain potential prey because of their coloration, other species have evolved mechanisms to mimic this coloration to avoid being eaten, even though they themselves may not be unpleasant to eat or contain toxic chemicals. In some cases of mimicry, a harmless species imitates the warning coloration of a harmful species. Assuming they share the same predators, this coloration then protects the harmless ones. Many insect species mimic the coloration of wasps, which are stinging, venomous insects, thereby discouraging predation (Figure \(\PageIndex{5}\)).
In other cases of mimicry, multiple species share the same warning coloration, but all of them actually have defenses. The commonness of the signal improves the compliance of all the potential predators. Figure \(\PageIndex{6}\) shows a variety of foul-tasting butterflies with similar coloration.
Click the link to visit the Bug Guide webpage (new window) and learn about Batesian mimicry and view stunning examples of mimicry in insects.
Competitive Exclusion Principle
Resources are often limited within a habitat and multiple species may compete to obtain them. Ecologists have come to understand that all species have an ecological niche. A niche is the unique set of resources used by a species, which includes its interactions with other species. The competitive exclusion principle states that two species cannot occupy the same niche in a habitat: in other words, different species cannot coexist in a community if they are competing for all the same resources. This principle works because if there is an overlap in resource use and therefore competition between two species, then traits that lessen reliance on the shared resource will be selected for leading to evolution that reduces the overlap. If either species is unable to evolve to reduce competition, then the species that most efficiently exploits the resource will drive the other species to extinction. An experimental example of this principle is shown in Figure \(\PageIndex{7}\) with two protozoan species: Paramecium aurelia and Paramecium caudatum . When grown individually in the laboratory, they both thrive. But when they are placed together in the same test tube (habitat), P. aurelia outcompetes P. caudatum for food, leading to the latter’s eventual extinction.
Symbiosis
Symbiotic relationships are close, long-term interactions between individuals of different species. Symbioses may be commensal, in which one species benefits while the other is neither harmed nor benefited; mutualistic, in which both species benefit; or parasitic, in which the interaction harms one species and benefits the other.
Commensalism
A commensal relationship occurs when one species benefits from a close prolonged interaction, while the other neither benefits nor is harmed. Birds nesting in trees provide an example of a commensal relationship (Figure \(\PageIndex{8}\)). The tree is not harmed by the presence of the nest among its branches. The nests are light and produce little strain on the structural integrity of the branch, and most of the leaves, which the tree uses to get energy by photosynthesis, are above the nest so they are unaffected. The bird, on the other hand, benefits greatly. If the bird had to nest in the open, its eggs and young would be vulnerable to predators. Many potential commensal relationships are difficult to identify because it is difficult to prove that one partner does not derive some benefit from the presence of the other.
Mutualism
A second type of symbiotic relationship is called mutualism, in which two species benefit from their interaction. For example, termites have a mutualistic relationship with protists that live in the insect’s gut (Figure \(\PageIndex{9}\) a ). The termite benefits from the ability of the protists to digest cellulose. However, the protists are able to digest cellulose only because of the presence of symbiotic bacteria within their cells that produce the cellulase enzyme. The termite itself cannot do this: without the protozoa, it would not be able to obtain energy from its food (cellulose from the wood it chews and eats). The protozoa benefit by having a protective environment and a constant supply of food from the wood chewing actions of the termite. In turn, the protists benefit from the enzymes provided by their bacterial endosymbionts, while the bacteria benefit from a doubly protective environment and a constant source of nutrients from two hosts. Lichen are a mutualistic relationship between a fungus and photosynthetic algae or cyanobacteria (Figure \(\PageIndex{9}\) b ). The glucose produced by the algae provides nourishment for both organisms, whereas the physical structure of the lichen protects the algae from the elements and makes certain nutrients in the atmosphere more available to the algae. The algae of lichens can live independently given the right environment, but many of the fungal partners are unable to live on their own.
 In this relationship, the parasite benefits, but the organism being fed upon, the host, is harmed. The host is usually weakened by the parasite as it siphons resources the host would normally use to maintain itself. Parasites may kill their hosts, but there is usually selection to slow down this process to allow the parasite time to complete its reproductive cycle before it or its offspring are able to spread to another host.
The reproductive cycles of parasites are often very complex, sometimes requiring more than one host species. A tapeworm causes disease in humans when contaminated, undercooked meat such as pork, fish, or beef is consumed (Figure \(\PageIndex{10}\)). The tapeworm can live inside the intestine of the host for several years, benefiting from the host’s food, and it may grow to be over 50 feet long by adding segments. The parasite moves from one host species to a second host species in order to complete its life cycle. Plasmodium falciparum is another parasite: the protists that cause malaria, a significant disease in many parts of the world. Living inside human liver and red blood cells, the organism reproduces asexually in the human host and then sexually in the gut of blood-feeding mosquitoes to complete its life cycle. Thus malaria is spread from human to mosquito and back to human, one of many arthropod-borne infectious diseases of humans.
To learn more about “Symbiosis in the Sea,” watch this webisode of Jonathan Bird’s Blue World
Characteristics of Communities
Communities are complex systems that can be characterized by their structure (the number and size of populations and their interactions) and dynamics (how the members and their interactions change over time). Understanding community structure and dynamics allows us to minimize impacts on ecosystems and manage ecological communities we benefit from.
Biodiversity
Ecologists have extensively studied one of the fundamental characteristics of communities: biodiversity. One measure of biodiversity used by ecologists is the number of different species in a particular area and their relative abundance. The area in question could be a habitat, a biome, or the entire biosphere. Species richness is the term used to describe the number of species living in a habitat or other unit. Species richness varies across the globe (Figure \(\PageIndex{11}\)). Ecologists have struggled to understand the determinants of biodiversity. Species richness is related to latitude: the greatest species richness occurs near the equator and the lowest richness occurs near the poles. Other factors influence species richness as well. Island biogeography attempts to explain the great species richness found in isolated islands, and has found relationships between species richness, island size, and distance from the mainland.
Relative species abundance is the number individuals in a species relative to the total number of individuals in all species within a system. Foundation species, described below, often have the highest relative abundance of species.
Foundation Species
Foundation species are considered the “base” or “bedrock” of a community, having the greatest influence on its overall structure. They are often primary producers, and they are typically an abundant organism. For example, kelp, a species of brown algae, is a foundation species that forms the basis of the kelp forests off the coast of California.
Foundation species may physically modify the environment to produce and maintain habitats that benefit the other organisms that use them. Examples include the kelp described above or tree species found in a forest. The photosynthetic corals of the coral reef also provide structure by physically modifying the environment (Figure \(\PageIndex{12}\)). The exoskeletons of living and dead coral make up most of the reef structure, which protects many other species from waves and ocean currents.
Keystone Species
A keystone species is one whose presence has inordinate influence in maintaining the prevalence of various species in an ecosystem, the ecological community’s structure, and sometimes its biodiversity. Pisaster ochraceus , the intertidal sea star, is a keystone species in the northwestern portion of the United States (Figure \(\PageIndex{13}\)). Studies have shown that when this organism is removed from communities, mussel populations (their natural prey) increase, which completely alters the species composition and reduces biodiversity. Another keystone species is the banded tetra, a fish in tropical streams, which supplies nearly all of the phosphorus, a necessary inorganic nutrient, to the rest of the community. The banded tetra feeds largely on insects from the terrestrial ecosystem and then excretes phosphorus into the aquatic ecosystem. The relationships between populations in the community, and possibly the biodiversity, would change dramatically if these fish were to become extinct.
BIOLOGY IN ACTION: Invasive Species
Invasive species are non-native organisms that, when introduced to an area out of its native range, alter the community they invade. In the United States, invasive species like the purple loosestrife ( Lythrum salicaria ) and the zebra mussel ( Dreissena polymorpha ) have altered aquatic ecosystems, and some forests are threatened by the spread of common buckthorn ( Rhamnus cathartica ) and garlic mustard ( Alliaria petiolata ). Some well-known invasive animals include the emerald ash borer ( Agrilus planipennis ) and the European starling ( Sturnus vulgaris ). Whether enjoying a forest hike, taking a summer boat trip, or simply walking down an urban street, you have likely encountered an invasive species.
One of the many recent proliferations of an invasive species concerns the Asian carp in the United States. Asian carp were introduced to the United States in the 1970s by fisheries (commercial catfish ponds) and by sewage treatment facilities that used the fish’s excellent filter feeding abilities to clean their ponds of excess plankton. Some of the fish escaped, and by the 1980s they had colonized many waterways of the Mississippi River basin, including the Illinois and Missouri Rivers.
Voracious feeders and rapid reproducers, Asian carp may outcompete native species for food and could lead to their extinction. One species, the grass carp, feeds on phytoplankton and aquatic plants. It competes with native species for these resources and alters nursery habitats for other fish by removing aquatic plants. Another species, the silver carp, competes with native fish that feed on zooplankton. In some parts of the Illinois River, Asian carp constitute 95 percent of the community's biomass. Although edible, the fish is bony and not desired in the United States. Moreover, their presence now threatens the native fish and fisheries of the Great Lakes, which are important to local economies and recreational anglers. Asian carp have even injured humans. The fish, frightened by the sound of approaching motorboats, thrust themselves into the air, often landing in the boat or directly hitting boaters.
The Great Lakes and their prized salmon and lake trout fisheries are being threatened by Asian carp. The carp are not yet present in the Great Lakes, and attempts are being made to prevent its access to the lakes through the Chicago Ship and Sanitary Canal, which is the only connection between the Mississippi River and Great Lakes basins. To prevent the Asian carp from leaving the canal, a series of electric barriers have been used to discourage their migration; however, the threat is significant enough that several states and Canada have sued to have the Chicago channel permanently cut off from Lake Michigan. Local and national politicians have weighed in on how to solve the problem. In general, governments have been ineffective in preventing or slowing the introduction of invasive species.
The issues associated with Asian carp show how population and community ecology, fisheries management, and politics intersect on issues of vital importance to the human food supply and economy. Socio-political issues like the Asian carp make extensive use of the sciences of population ecology, the study of members of a particular species occupying a habitat; and community ecology, the study of the interaction of all species within a habitat.
Community Dynamics
Community dynamics are the changes in community structure and composition over time, often following environmental disturbances such as volcanoes, earthquakes, storms, fires, and climate change. Communities with a relatively constant number of species are said to be at equilibrium. The equilibrium is dynamic with species identities and relationships changing over time, but maintaining relatively constant numbers. Following a disturbance, the community may or may not return to the equilibrium state.
Succession describes the sequential appearance and disappearance of species in a community over time after a severe disturbance. In primary succession, newly exposed or newly formed rock is colonized by living organisms; in secondary succession, a part of an ecosystem is disturbed and remnants of the previous community remain. In both cases, there is a sequential change in species until a more or less permanent community develops.
Primary Succession and Pioneer Species
Primary succession occurs when new land is formed, for example, following the eruption of volcanoes, such as those on the Big Island of Hawaii. As lava flows into the ocean, new land is continually being formed. On the Big Island, approximately 32 acres of land is added to it its size each year. Weathering and other natural forces break down the rock enough for the establishment of hearty species such as lichens and some plants, known as pioneer species(Figure \(\PageIndex{14}\)). These species help to further break down the mineral-rich lava into soil where other, less hardy but more competitive species, such as grasses, shrubs, and trees, will grow and eventually replace the pioneer species. Over time the area will reach an equilibrium state, with a set of organisms quite different from the pioneer species.
Secondary succession
A classic example of secondary succession occurs in oak and hickory forests cleared by wildfire (Figure \(\PageIndex{15}\)). Wildfires will burn most vegetation, and unless the animals can flee the area, they are killed. Their nutrients, however, are returned to the ground in the form of ash. Thus, although the community has been dramatically altered, there is a soil ecosystem present that provides a foundation for rapid recolonization.
Before the fire, the vegetation was dominated by tall trees with access to the major plant energy resource: sunlight. Their height gave them access to sunlight while also shading the ground and other low-lying species. After the fire, though, these trees are no longer dominant. Thus, the first plants to grow back are usually annual plants followed within a few years by quickly growing and spreading grasses and other pioneer species. Due, at least in part, to changes in the environment brought on by the growth of grasses and forbs, over many years, shrubs emerge along with small pine, oak, and hickory trees. These organisms are called intermediate species. Eventually, over 150 years, the forest will reach its equilibrium point and resemble the community before the fire. This equilibrium state is referred to as the climax community, which will remain until the next disturbance. The climax community is typically characteristic of a given climate and geology. Although the community in equilibrium looks the same once it is attained, the equilibrium is a dynamic one with constant changes in abundance and sometimes species identities. The return of a natural ecosystem after agricultural activities is also a well-documented secondary succession process.
Contributors and Attributions
Remixed and/or curated from the following works:
Fowler, S., Roush, R., & Wise, J. (2013). 19.4 Community Ecology . In Concepts of Biology . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction ).


1.8: Translating your topic into searchable keywords
It is important to think about your search terms more carefully so you get better and more relevant results for your research. Take the time to think about the essential concepts that make up your research question. These concepts can become keywords, concise terms that you can use to make your search more efficient and relevant. Here are some examples of how you might go about generating keywords to improve your search. For these examples we’ll assume you have a class project on the topic “home design that is safe and comfortable for the elderly.”
Go to Google
One way of generating keywords would be to go to Google and search for that exact phrase. Using this approach, you’ll find lots of results, but only some of them will be helpful and relevant. As you examine your results, you might find synonyms or alternate vocabulary that could be useful, including: “home safety,” “universal design,” “accessible housing,” “older adults,” and so on. These can become helpful keywords for you to use when building a new search.
Find the essential concepts
Another way to find keywords is to break your topic into its essential concepts. Our example could be split up like this:
- Concept 1: home design
- Concept 2: safe and comfortable
- Concept 3: elderly
Once you have these concepts, you can search for them in a thesaurus, a tool that suggests synonyms based on the term you use. Be aware that some terms in the thesaurus may match your intended meaning better than others, for example, the word “benefit” could have several different meanings. Below, we’ve listed some potential keywords from both our Google search and the thesaurus, alongside the original concepts they relate to:
- home design : universal design, design for aging, elder-friendly design, housing design, architecture, architectural design, design features, supportive design, design
- safe and comfortable : home safety, accessibility, barrier-free
- elderly : senior citizens, seniors, old, older adults, older people, aging, aged, elderly people, elder
Use your keywords effectively
Now that we’ve identified keywords for our concepts, we can bring them together to build a search, such as:
- home design and safety and elderly
- universal design and safety and older people
- housing design and accessibility and senior citizens
In your search, you want to include keywords for each of the concepts. This will reduce the number of extra results that are partly off-topic. In our example, a search for the two concepts “safety and home design” could also find articles on making homes safe for babies and children instead of for senior citizens. Mix and match the keywords and try out different combinations to see which strategies produce the most relevant results. Are some terms or strategies more successful? Save useful searches and try them out in other search tools as well.
Need some more practice? Try this How to Generate Keywords tutorial, from the University of Texas at Austin. It will take you through the steps of brainstorming synonyms for the topic of your choice. You can experiment with searching for these terms using the ISU Library website .
Sometimes the topic you’re researching is so new to you that you don’t know whether you’re using the right keywords. When that’s the case, finding background information can help. Background information can lead you to new concepts and keywords related to your topic. Believe it or not, Wikipedia can be a good source for this type of information.


18.1: Introduction to Lock out Tag out
Introduction
Since OSHA's formation in the 1970's they have adopted various lockout/tagout related provisions from existing national consensus standards and other Federal standards, which were developed for specific types of equipment or industries. In 1990 a new standard 1910.147 Control of Hazardous Energy (Lockout/Tagout) went into effect. This standard seeks to safeguard employees from the unexpected startup of machinery or equipment or release of hazardous energy while performing service or maintenance work.
Application to construction
The provisions of 1910.147 standard, while not mandatory for construction, provide a good foundation for safe lockout/tagout procedures no matter where the maintenance operation occurs. The OSHA 1910.147 standard is intended to be used when electrical supply lines are being de-energized for the purpose of performing maintenance type operations. While a comprehensive lockout/tagout standard does not exist for construction there are components of some standards that require this protection. These lockout/tagout provisions will also be reviewed in this lesson.
Scope and Application
The Lockout/Tagout standard covers the servicing and maintenance of machines and equipment in which the "unexpected" energizing or startup of the machines or equipment, or release of stored energy could cause injury to employees. The standard establishes minimum performance requirements for the control of such hazardous energy.
This standard does not cover the following:
- Construction, agriculture and maritime employment;
- Installations under the exclusive control of electric utilities for the purpose of power generation, transmission and distribution including related equipment for communication or metering; and
- Exposure to electrical hazards from work on, near, or with conductors or equipment in electric utilization installations, which is covered by Subpart S.
- Oil and gas well drilling and servicing.
Normal production operations
Normal production operations are not covered by this standard (See Subpart 0 of this Part). Servicing and/or maintenance which takes place during normal production operations is covered by this standard only if:
- An employee is required to remove or bypass a guard or other safety device; or
- An employee is required to place any part of his or her body into an area on a machine or piece of equipment where work is actually performed upon the material being processed (point of operation) or where an associated danger zone exists during a machine operating cycle.
Minor tool changes and adjustments
Minor tool changes and adjustments, and other minor servicing activities which take place during normal production operations, are not covered by this standard if they are routine, repetitive, and integral to the use of the equipment for production, provided that the work is performed using alternative measures which provide effective protection.
Application of standard
This standard does not apply to the following:
- Work on cord and plug connected electric equipment for which exposure to the hazards of unexpected energizing or startup of the equipment is controlled by the unplugging of the equipment from the energy source and by the plug being under the exclusive control of the employee performing the servicing or maintenance.
- Hot tap operations involving transmission and distribution systems for substances such as gas, steam, water or petroleum products when they are performed on pressurized pipelines, provided that the employer demonstrates that-
- continuity of service is essential;
- shutdown of the system is impractical; and
- documented procedures are followed, and special equipment is used which will provide proven effective protection for employees.
Definitions
The following definitions are applicable to the lockout/tagout standard:
Affected employee: An employee whose job requires him/her to operate or use a machine or equipment on which servicing or maintenance is being performed under lockout or tagout, or whose job requires him/her to work in an area in which such servicing or maintenance is being performed.
Authorized employee: A person who locks out or tags out machines or equipment in order to perform servicing or maintenance on that machine or equipment. An affected employee becomes an authorized employee when that employee’s duties include performing servicing or maintenance covered under this section.
Capable of being locked out: An energy isolating device is capable of being locked out if it has a hasp or other means of attachment to which, or through which, a lock can be affixed, or it has a locking mechanism built into it. Other energy isolating devices are capable of being locked out, if lockout can be achieved without the need to dismantle, rebuild, or replace the energy isolating device or permanently alter its energy control capability.
Energized: Connected to an energy source or containing residual or stored energy.
Energy isolating device: A mechanical device that physically prevents the transmission or release or energy, including but not limited to the following: A manually operated electrical circuit breaker, a disconnect switch, a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors and, in addition no pole can be operated independently; a line valve; a block; and any similar device used to block or isolate energy. Push buttons, selector switches and other control circuit type devices are not energy isolating devices.
Energy source: Any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy.
Hot tap: A procedure used in the repair maintenance and services activities which involves welding on a piece of equipment (pipelines vessels or tanks) under pressure, in order to install connections or appurtenances, it is commonly used to replace or add sections of pipeline without the interruption of service for air, gas, water, steam, and petrochemical distribution systems.
Lockout: The placement of a lockout device on an energy isolating device, in accordance with an established procedure, ensuring that the energy isolating device and the equipment being controlled cannot be operated until the lockout device is removed.
Lockout device: A device that utilizes a positive means such as a lock, either key or combination type, to hold an energy isolating device in the safe position and prevent the energizing of a machine or equipment. Included are blank flanges and bolted slip blinds.
Normal production operations: The utilization of a machine or equipment to perform its intended production function.
Servicing and/or maintenance: Workplace activities such as constructing, installing, setting up, adjusting, inspecting, modifying, and maintaining and/or servicing machines or equipment. These activities include lubrication, cleaning or unjamming of machines or equipment and making adjustments or tool changes, where the employee may be exposed to the unexpected energizing or startup of the equipment or release of hazardous energy.
Setting up: Any work performed to prepare a machine or equipment to perform its normal production operation.
Tagout: The placement of a tagout device on an energy isolating device, in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.
Tagout device: A prominent warning device, such as a tag and a means of attachment, which can be securely fastened to an energy isolating device in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tag out device is removed.
Energy Control Program
General
The employer shall establish a program consisting of energy control procedures, employee training and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, startup or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source and rendered inoperative.
Not capable of being locked out
If an energy isolating device is not capable of being locked out, the employer s energy control program shall utilize a tagout system.
Capable of being locked out
If an energy isolating device is capable of being locked out, the employer energy control program shall utilize lockout, unless the employer can demonstrate that the utilization of a tagout system will provide full employee protection.
Effective date
After January 1990, whenever replacement or major repair, renovation or modification of a machine or equipment is performed, and whenever new machines or equipment are installed, energy isolating devices for such machine or equipment shall be designed to accept a lockout device.
Tag out device use
When a tagout device is used on an energy isolating device which is capable of being locked out, the tagout device shall be attached at the same location that the lockout device would have been attached, and the employer shall demonstrate that the tagout program will provide a level of safety equivalent to that obtained by using a lockout program.
Full employee protection
In demonstrating that a level of safety is achieved in the tag out program which is equivalent to the level of safety obtained by using a lockout program, the employer shall demonstrate full compliance with all tagout-related provisions of this standard together with such additional elements as are necessary to provide the equivalent safety available from the use of a lockout device. Additional means to be considered as part of the demonstration of full employee protection shall include the implementation of additional safety measures such as the removal of an isolating circuit element, blocking of a controlling switch, opening of an extra disconnecting device, or the removal of a valve handle to reduce the likelihood of inadvertent energizing.