Category: Nursing

VARK Questionnaire Essay assignment

Learning styles represent the different approaches to learning based on preferences, weaknesses, and strengths. For learners to best achieve the desired educational outcome, learning styles must be considered when creating a plan. Complete “The VARK Questionnaire,” located on the VARK website, and then complete the following:

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Click “OK” to receive your questionnaire scores.

Once you have determined your preferred learning style, review the corresponding link to view your learning preference.

Review the other learning styles: visual, aural, read/write, kinesthetic, and multimodal (listed on the VARK Questionnaire Results page). VARK Questionnaire Essay assignment.

Compare your current preferred learning strategies to the identified strategies for your preferred learning style.

Examine how awareness of learning styles has influenced your perceptions of teaching and learning.

In a paper (750‐1,000 words), summarize your analysis of this exercise and discuss the overall value of learning styles. Include the following:

Provide a summary of your learning style according the VARK questionnaire.

Describe your preferred learning strategies. Compare your current preferred learning strategies to the identified strategies for your preferred learning style. VARK Questionnaire Essay assignment.

Describe how individual learning styles affect the degree to which a learner can understand or perform educational activities. Discuss the importance of an educator identifying individual learning styles and preferences when working with learners.

Discuss why understanding the learning styles of individuals participating in health promotion is important to achieving the desired outcome. How do learning styles ultimately affect the possibility for a behavioral change? How would different learning styles be accommodated in health promotion?

VARK means visual, auditory, read/write and kinesthetic. MY VARK SCORE: HIGHT SCORE Visual 6 AND KINESTHETIC 6  COMPARED TO  AUDITORY AND AUDITORY AND RED/WRITE WITH LOW SCORE 2.

In formal writing you should avoid personal references and use of first person. This assignment does make this more difficult. There are ways to write without saying “I”. Work to limit the use of “I statements” in this paper. VARK Questionnaire Essay assignment.

Try: The writer of this paper found that the visual learning style had the highest score….

Or: According to the findings of this author….

Or: After taking the VARK questionnaire the author of this paper was surprised to find the results included a strong preference for aural learning. This is not a strategy often used

 

www.vark-learn.com

Learning Styles: A Guide to the 4 VARK Styles

https://www.definedstem.com/wp-content/uploads/2017/05/VARK.pdf

https://www.verywellmind.com/vark-learning-styles-2795156

 

Cite to at least three peer‐reviewed or scholarly sources to complete this assignment. Sources should be published within the last 5 years and appropriate for the assignment criteria.  VARK Questionnaire Essay assignment.

Prepare this assignment according to the guidelines found in the APA Style. An abstract is not required.

This assignment uses a rubric. Please review the rubric prior to beginning the assignment to become familiar with the expectations for successful completion.

RUBRIC: Personal learning style according to the VARK questionnaire is identified and described in detail. Summary offers examples that display personal insight or reflection.

Personal learning strategy is clearly described. A comparison of current preferred learning styles and VARK identified learning styles is detailed. Overall discussion demonstrates insight into preferred learning strategies and how these support preferred learning styles.

Importance of learning styles for a learner, and importance of educator identifying individual learning styles and preferences when working with learners, is thoroughly discussed. The importance of learning styles for learners participating in healthy promotion, and identifying them as an educator, is clearly established. Strong rationale and evidence support discussion.

Understanding the learning styles of individuals participating in a health promotion, and the correlation to behavioral change and achieving desired outcomes is discussed in detail. A strong correlation has been established. Accommodation of different learning styles is discussed. The narrative demonstrates insight into the importance of learning styles to health promotion and behavioral outcome VARK Questionnaire Essay assignment

Thesis is comprehensive and contains the essence of the paper. Thesis statement makes the purpose of the paper clear.

Clear and convincing argument that presents a persuasive claim in a distinctive and compelling manner. All sources are authoritative. Writer is clearly in command of standard, written, academic English. All format elements are correct. Sources are completely and correctly documented, as appropriate to assignment and style, and format is free of error. VARK Questionnaire Essay assignment

Compose an MLA essay, response to
ONE
of the prompts below.

Your response should have an appropriate and interesting introduction with a strong thesis regarding what you are trying to prove in the essay; body paragraphs, each with a clear main point that relates to and helps support your thesis; and a conclusion that effectively and powerfully wraps up the essay.

You should draw upon sources in writing your response. These include the articles, essays, stories, books, and poems we have read for class and any additional research that you may conduct. Provide in-text citations and a Works Cited page in MLA format.

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For any of these prompts, you may NOT choose a text that you have used in ANY of the other course assignments (aside from journals).

Element Approach
: Choose ONE text that we have read to analyze in depth.
Your ultimate goal should be to show how ALL of the other elements work to show the main theme (choose only one) of the work.
In so doing, you will make an argument that the theme you have chosen is the main theme of the work and will support your argument by analyzing ALL of the other elements within the work. In a cohesive, thoughtful essay, engage in some in-depth analysis and interpretation of your selected work. You may choose any novel, short story, poem, film, or drama (play) we have read for class. You should
quote
from (
and directly cite
) at least
8 times
from your chosen work. MLA essay

Literary Theory Research Approach:
Choose ONE text that we have read to analyze in depth.
Your ultimate goal should be to apply one literary theory to the work and conduct some outside research to provide some context for the application of the theory.
In so doing, you will make an argument that the theory you have applied provides an important interpretation for the work and will support your argument using both the literary text you’ve selected and some outside research. In a cohesive, thoughtful essay, combine both passages from your selected text and from your outside research to create a specific theoretical-based reading. You may choose any novel, short story, poem, film, or drama (play) we have read for class. You should
quote
from (
and directly cite
) at least
5 times
from your chosen work AND
3 times
from your outside research. MLA essay.

Creative Approach:
Propose your own prompt.
This should align with the course objectives and needs to be cleared by me before you begin.

You may use outside research for this MLA essay. However, make sure your voice and ideas are the clear focus.
DO NOT plagiarize
. Any plagiarism—from one sentence to the whole essay, intentional or unintentional—will result in a “0” and an “F” for the course.

Use your journals to help you with this essay—draw upon your previous ideas and writing here if it is helpful.

Page length: 5 full pages minimum

 

Clarity

[10]

Does the essay use proper and varied sentence structure, punctuation, etc.? Does it avoid grammatical errors: fragments, run-ons, spelling mistakes, etc.?

 

 

Did the essay meet the assignment criteria in purpose and appearance?

Correct MLA formatting? Proper citations?

Coherence/ Structure [10]

 

 

Does the essay have a strong, clear, well-structured thesis?

 

 

 

 

Does the essay employ tight, polished paragraphs in the correct format or are ideas just thrown together?  Does each body paragraph include one main idea/topic sentence that points the reader back to the thesis?

Does the essay contain a strong backbone/ structure?  Does it use the intro. well? The conclusion? Does every IP present a unified argument? (Does it “flow” well?)  Are there effective transitions? MLA essay

Critical Thinking [30]

 

 

 

 

 

How advanced is the essay’s content?  Does it explore new ideas that challenge both the writer and reader or simply regurgitate class discussions or popular thought?  Does it meet the page length?

 

 

 

 

Does the paper make a logical connection between the thesis, topic sentences, and examples/proof? (i.e., Does it “connect-the-dots” between claims made in the thesis and examples for that claim?)

Does the paper provide adequate “proof”? (Quotations or paraphrase, research, expert opinions, statistics, examples, details, etc?)

Comments:                                                                                                                              Total Pts.

                 /50

X

=

Grade MLA essay

 

50

A+

39

C+

49-46

A

38-36

C

45

A-

35

C-

44

B+

34-30

D

43-41

B

29-0

F

40

B-

MLA essay

NURS 6053 Assignment: Developing Organizational Policies and Practices

Assignment: Developing Organizational Policies and Practices

Competing needs arise within any organization as employees seek to meet their targets and leaders seek to meet company goals. As a leader, successful management of these goals requires establishing priorities and allocating resources accordingly.

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Within a healthcare setting, the needs of the workforce, resources, and patients are often in conflict. Mandatory overtime, implementation of staffing ratios, use of unlicensed assisting personnel, and employer reductions of education benefits are examples of practices that might lead to conflicting needs in practice. NURS 6053 Assignment: Developing Organizational Policies and Practices.

Leaders can contribute to both the problem and the solution through policies, action, and inaction. In this Assignment, you will further develop the white paper you began work on in Module 1 by addressing competing needs within your organization.

To Prepare:

Review the national healthcare issue/stressor you examined in your Assignment for Module 1, and review the analysis of the healthcare issue/stressor you selected.

Identify and review two evidence-based scholarly resources that focus on proposed policies/practices to apply to your selected healthcare issue/stressor.

Reflect on the feedback you received from your colleagues on your Discussion post regarding competing needs.

The Assignment (4-5 pages):

Developing Organizational Policies and Practices

Add a section to the paper you submitted in Module 1. The new section should address the following:

Identify and describe at least two competing needs impacting your selected healthcare issue/stressor.

Describe a relevant policy or practice in your organization that may influence your selected healthcare issue/stressor.

Critique the policy for ethical considerations, and explain the policy’s strengths and challenges in promoting ethics.

Recommend one or more policy or practice changes designed to balance the competing needs of resources, workers, and patients, while addressing any ethical shortcomings of the existing policies. Be specific and provide examples.

Cite evidence that informs the healthcare issue/stressor and/or the policies, and provide two scholarly resources in support of your policy or practice recommendations. NURS 6053 Assignment: Developing Organizational Policies and Practices.

 

 

 

Excellent

Good

Fair

Add a section to the paper you submitted in Module 1. In 4–5 pages, address the following:

·   Identify and describe at least two competing needs impacting your selected healthcare issue/stressor.

23 (23%) – 25 (25%)

The response accurately and clearly identifies at least two competing needs impacting the healthcare issue/stressor selected.

20 (20%) – 22 (22%)

The response identifies at least two competing needs impacting the healthcare issue/stressor selected.

NURS 6053 Assignment: Developing Organizational Policies and Practices

18 (18%) – 19 (19%)

The response identifies at least two competing needs impacting the healthcare issue/stressor selected that is vague or inaccurate.

0 (0%) – 17 (17%)

The response describes at least two competing needs impacting the healthcare issue/stressor selected that is vague and inaccurate, or is missing.

·   Describe a relevant policy or practice in your organization that may influence your selected healthcare issue/stressor.

·   Critique the policy for ethical considerations and explain the policy’s strengths and challenges in promoting ethics.

27 (27%) – 30 (30%)

The response accurately and thoroughly describes in detail a relevant policy or practice in an organization that may influence the healthcare issue/stressor selected.

The response accurately and thoroughly critiques in detail the policy for ethical considerations and explains in detail the policy’s strengths and challenges in promoting ethics.

24 (24%) – 26 (26%)

The response accurately describes a relevant policy or practice in an organization that may influence the healthcare issue/stressor selected.

The response accurately critiques the policy for ethical considerations and explains the policy’s strengths and challenges in promoting ethics.

21 (21%) – 23 (23%)

The response describes a relevant policy or practice in an organization that may influence the healthcare issue/stressor selected that is vague or inaccurate.

The response critiques the policy for ethical considerations and explains the policy’s strengths and challenges in promoting ethics that is vague or inaccurate.

NURS 6053 Assignment: Developing Organizational Policies and Practices

0 (0%) – 20 (20%)

The response describes a relevant policy or practice in an organization that may influence the healthcare issue/stressor selected that is vague and inaccurate, or is missing.

The response critiques the policy for ethical considerations and explains the policy’s strengths and challenges in promoting ethics that is vague and inaccurate, or is missing.

·   Recommend one or more policy or practice changes designed to balance the competing needs of resources, workers, and patients while addressing any ethical shortcomings of the existing policies. Be specific and provide examples.

·   Cite evidence that informs the healthcare issue/stressor and/or the policies and provide two scholarly resources in support of your policy or practice recommendations.

NURS 6053 Assignment: Developing Organizational Policies and Practices

27 (27%) – 30 (30%)

The response provide one or more accurate, clear, and thorough recommendations for policy or practice changes designed to balance the competing needs of resources, workers, and patients while addressing any ethical shortcomings of the existing policies.

Specific and accurate examples are provided.

Accurate and detailed evidence is cited that informs the healthcare issue/stressor selected and a specific synthesis of at least two outside scholarly resources in full support of the policy or practice recommendations is provided. The response integrates at least 2 outside resources and 2 or 3 course-specific resources that fully support the healthcare issue/stressor selected.

24 (24%) – 26 (26%)

The response provides one or more recommendations for policy or practice changes designed to balance the competing needs of resources, workers, and patients while addressing any ethical shortcomings of the existing policies.

Specific examples may be provided.

Evidence is cited that informs the healthcare issue/stressor selected and a synthesis of at least one outside scholarly resource that may support the policy or practice recommendations is provided. The response integrates at least 1 outside resource and 2 or 3 course-specific resources that may support the healthcare issue/stressor selected.

21 (21%) – 23 (23%)

The response provides one or more recommendations for policy or practice changes designed to balance the competing needs of resources, workers, and patients while addressing any ethical shortcomings of the existing policies that is vague or inaccurate.

Examples may be provided.

Vague or inaccurate evidence is cited from 2 or 3 resources that informs the healthcare issue/stressor selected and may support the policy or practice recommendations provided.

0 (0%) – 20 (20%)

The response provides one or more recommendations for policy or practice changes designed to balance the competing needs of resources, workers, and patients while addressing any ethical shortcomings of the existing policies that is vague and inaccurate, or is missing.

Examples are missing.

Vague and inaccurate evidence is cited that informs the healthcare issue/stressor and may include at least 1 scholarly resource that vaguely and inaccurately supports the policy practice recommendations is provided, or is missing.

Written Expression and Formatting – Paragraph Development and Organization:

Paragraphs make clear points that support well-developed ideas, flow logically, and demonstrate continuity of ideas. Sentences are carefully focused—neither long and rambling nor short and lacking substance. A clear and comprehensive purpose statement and introduction is provided which delineates all required criteria.

5 (5%) – 5 (5%)

Paragraphs and sentences follow writing standards for flow, continuity, and clarity.

A clear and comprehensive purpose statement, introduction, and conclusion is provided which delineates all required criteria.

4 (4%) – 4 (4%)

Paragraphs and sentences follow writing standards for flow, continuity, and clarity 80% of the time.

Purpose, introduction, and conclusion of the assignment is stated, yet is brief and not descriptive.

3.5 (3.5%) – 3.5 (3.5%)

Paragraphs and sentences follow writing standards for flow, continuity, and clarity 60%–79% of the time.

Purpose, introduction, and conclusion of the assignment is vague or off topic.

0 (0%) – 3 (3%)

Paragraphs and sentences follow writing standards for flow, continuity, and clarity < 60% of the time. No purpose statement, introduction, or conclusion was provided. NURS 6053 Assignment: Developing Organizational Policies and Practices Written Expression and Formatting – English writing standards: Correct grammar, mechanics, and proper punctuation 5 (5%) – 5 (5%) Uses correct grammar, spelling, and punctuation with no errors. 4 (4%) – 4 (4%) Contains a few (1 or 2) grammar, spelling, and punctuation errors. 3.5 (3.5%) – 3.5 (3.5%) Contains several (3 or 4) grammar, spelling, and punctuation errors. 0 (0%) – 3 (3%) Contains many (≥ 5) grammar, spelling, and punctuation errors that interfere with the reader’s understanding. Written Expression and Formatting – The paper follows correct APA format for title page, headings, font, spacing, margins, indentations, page numbers, parenthetical/in-text citations, and reference list. 5 (5%) – 5 (5%) Uses correct APA format with no errors. 4 (4%) – 4 (4%) Contains a few (1 or 2) APA format errors. 3.5 (3.5%) – 3.5 (3.5%) Contains several (3 or 4) APA format errors. NURS 6053 Assignment: Developing Organizational Policies and Practices 0 (0%) – 3 (3%) Contains many (≥ 5) APA format errors. Total Points: 100 Name:  NURS_6053_Module02_Week03_Assignment_Rubric NURS 6053 Assignment: Developing Organizational Policies and Practices

Genotypes, Phenotypes, and Alleles Essay Assignments

Variants of a gene are called alleles, which can be either dominant or recessive. An organism’s genotype (its genetic makeup) determines its phenotype (its expressed traits).

Through his experimentation with cross-breeding different varieties of pea plants, Gregor Mendel concluded that there were two variants for pea color and that the yellow one masked the green one. Today, scientists understand that 
diploid
 organisms carry two copies of each gene. The copies of the genes may be different. A version of a gene is known as an 
allele
. When one allele masks the expression of another, it is said to be a 
dominant allele
. The allele whose expression is masked by another allele is a 
recessive allele
. When an individual has two identical alleles for a gene, it is said to be 
homozygous
. If an individual carries two identical dominant alleles for a gene, it is called homozygous dominant, while individuals with two recessive alleles are called homozygous recessive. When an individual has two different alleles for a gene, it is said to be 
heterozygous
. A heterozygous individual will have a phenotype of the dominant allele but may pass the recessive allele to offspring. Genotypes, Phenotypes, and Alleles Essay Assignments.

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The observable characteristics (in Mendel’s case, the color of the pea) of an organism that result from genetic and environmental influences is the organism’s 
phenotype
. The genetic makeup of the organism is its 
genotype
, while its expressed traits make up its phenotype. Mendel’s 
law of independent assortment
 is the principle that states that alleles of different genes are sorted into gametes independently of one another. However, some genes lie very close to each other on their 
chromosomes
. These genes that are frequently inherited together are called linked genes.

The tool geneticists use to predict the possible genotypic outcomes of a cross between two individuals is called a 
Punnett square
(named after its creator, Reginald C. Punnett, a British geneticist). The alleles of one parent are listed individually across the top, while the alleles of the other parent are listed individually down the left side. The square is then filled in with the corresponding alleles. By convention, the dominant allele is written using an uppercase letter, and the recessive allele is written using the same letter in lowercase. Genotypes, Phenotypes, and Alleles Essay Assignments.

This Punnett square shows a cross between a parent that is homozygous dominant for a trait (BB), meaning that the parent has two dominant alleles, and a parent that is homozygous recessive for the trait (bb), meaning that the parent has two recessive alleles. All possible offspring are heterozygous (Bb), meaning they have one dominant and one recessive allele.

The Punnett square for Mendel’s pea plants uses the letter Y to represent the color of the peas, because the dominant color is yellow. Genotypes, Phenotypes, and Alleles Essay Assignments.

Punnett Square Showing Parent Pea Pod Color Inheritance

A Punnett square shows the predicted possible genotypes (genetic makeup) from a single cross. In this case, crossing a plant with yellow peas (YY) and a plant with green peas (yy) can give only plants with yellow peas (Yy). The yellow allele (Y) is dominant over the green one (y). Each allele is a variant of the trait, in this case, pea color.

A Punnett square can then be used to predict the offspring of the self-pollination of the first generation (F
1
). When the first generation of pea plants self-pollinates, a Punnett square can then be used to determine the chances of the offspring having yellow peas or green peas. The resulting offspring have a 3:1 chance of having yellow peas as opposed to green peas. Genotypes, Phenotypes, and Alleles Essay Assignments.

Punnett Square showing F1 Generation Pea Pod Color Inheritance

When the first generation (F
1
) is self-pollinated, the resulting offspring have a 3:1 chance of having yellow peas as opposed to green. Because yellow (Y) is dominant, three of the possible genotypes (YY, Yy, and Yy) have yellow peas, and only genotype yy has green peas.

Importantly, a Punnett square doesn’t show 
how many
 offspring will have each genotype. Rather, it shows the 
chances
each offspring has of having each genotype. In other words, self-pollinating a plant with genotype Yy four times does not guarantee two offspring with Yy genotype, one with YY, and one with yy. Each event has the same chance as the others of producing each genotype. Thus, the pollination of a plant with genotype Yy with another plant with genotype Yy gives a 25 percent chance of an offspring with genotype YY, a 50 percent chance of an offspring with genotype Yy, and a 25 percent chance of an offspring with genotype yy. Because both genotypes YY and Yy have plants with yellow peas, this cross results in a 75 percent chance of an offspring with a phenotype of yellow peas and a 25 percent chance of an offspring with green peas. Genotypes, Phenotypes, and Alleles Essay Assignments.

Gregor Mendel Pea Plant Experiments Essay Assignments

Organisms have many units of heritable material that code for particular traits, each called a
gene
. Each 
trait
, or characteristic, is determined by an organism’s genes. Two hundred years ago, however, the mechanisms of inheritance were not known. 
Gregor Mendel
 (1822–84) is an Austrian monk credited with discovering the principles underlying genes and inheritance. Mendel performed a series of experiments with pea plants in the 19th century. These led to the discovery of the genetic basis of inheritance (the traits that are received by offspring from parents) and resulted in him being posthumously considered the father of modern genetics.

The Pea Plant Experiments

Mendel used pea plants to learn the genetic basis of inheritance.

Since childhood, Mendel had been a gardener. In the monastery, he set up a series of experiments using pea plants. Mendel observed that pea plants could vary in terms of seven different characteristics:

flower color (purple or white)

flower position (axial, on the shoot where a branch begins; or terminal, at the end of the shoot)

pea color (green or yellow)

pea shape (round or wrinkled)

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plant size (tall or short)

pod color (green or yellow)

pod shape (constricted or inflated)

In his experiments Mendel cross-fertilized plants with different characteristics and observed the resulting 
offspring
. He noticed that patterns emerged; some of these patterns were immediately evident and others required multiple generations to emerge. Mendel concluded that each plant had factors that determined how the plant would look. Today, Mendel’s factors are known as 
genes
. Gregor Mendel Pea Plant Experiments Essay Assignments.

To better understand Mendel’s experiments, one can follow an example using pea color as the selected characteristic. Mendel observed that peas could be green or yellow. He began by crossing a plant with green peas and a plant with yellow peas. The original two organisms that are crossed to produce offspring are called the 
parent generation (P)
. The first offspring resulting from a parental cross are called the 
first filial generation (F
1
)
. Mendel’s first generation plants all had yellow peas. Gregor Mendel Pea Plant Experiments Essay Assignments. He then pollinated one of these offspring plants with itself. The offspring of a cross between individuals of the first generation are called the
second filial generation (F
2
)
. Mendel’s second generation plants had a mixture of green and yellow peas. In fact, the ratio of plants with yellow peas to plants with green peas was 3:1. Mendel then pollinated each plant in the second generation with itself, and he found that one plant with yellow peas gave only plants with yellow peas, while others continued to give plants showing the 3:1 ratio. The plant with green peas gave only plants with green peas. This is the basis for Mendel’s law of segregation. Gregor Mendel Pea Plant Experiments Essay Assignments.

spermatogenesis and oogenesis – Gamete Formation essay Assignments

Sexually reproducing organisms use gametes (sex cells) to reproduce.

Bacteria and other single-celled organisms reproduce simply by copying their genetic material, then splitting in half. The benefit of this method is that these organisms do not need to find a mate. The downside, however, is that each offspring has the same genetic makeup as the parent. While asexual reproduction has its benefits, the transfer of genetic material that occurs during sexual reproduction allows for genetic variation in offspring. The genetic variation achieved with sexual reproduction allows the potential for some offspring to have an increased chance to survive their environment. spermatogenesis and oogenesis – Gamete Formation essay Assignments.

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Sexual reproduction involves the combination of genetic material from two parents. This happens through the production and transmission of gametes. A 
gamete
 is the sex cell of a sexually reproducing organism, with a haploid set of chromosomes. Gametes are produced from cells called germ cells. They are different from the rest of the body cells in their functions, and they stay that way for their entire lives. When an animal is of reproductive age, the germ cells are activated in the gonads, the areas of the body where gametes are produced (in humans, this is the testes for males and the ovaries for females). It is here that the sex cells are formed. 
Spermatogenesis
 is the formation of sperm through the process of meiosis. Spermatogenesis produces four sperm cells from a single existing precursor cell. 
Oogenesis
 is the process of egg cell formation during meiosis. Oogenesis produces one viable egg cell from one existing precursor cell. Once these cells have been made, they undergo the process of 
meiosis
, a process in cell division during which the number of chromosomes is reduced to half the original number by two divisions of the nucleus, resulting in the production of gametes. This reduction of chromosomes (bundles of genetic material) present in each cell is referred to as 
haploid
 (1
n
 or 
n
), half the total of the parent. Gametes must be haploid in sexually reproducing organisms in order to combine with the gamete from the parent of the opposite sex and form an offspring with a complete complement of chromosomes. spermatogenesis and oogenesis – Gamete Formation essay Assignments.

Sperm production happens in the male in specialized organs called the testes. In most mammals, the testes are located in an external sac called the scrotum because normal sperm production requires temperatures slightly lower than the organism’s body temperature. Special cells, called Sertoli cells, provide nutrition for the developing sperm. Meiosis in sperm cells begins with a 
spermatogonium
, which is the diploid (2
n
) cell that is the origin cell in spermatogenesis. 
Diploid
 means having a double set of chromosomes in homologous pairs; the diploid condition is designated by 2
n
. Sperm production involves the following processes:

Step 1.
 The spermatogonium divides, producing two diploid primary spermatocytes. A 
primary spermatocyte
 is a diploid (2
n
) cell that is the first cell formed in spermatogenesis.

Step 2.
 The primary spermatocytes then divide, reducing the chromosome number to form two haploid secondary spermatocytes. A 
secondary spermatocyte
 is the haploid (1
n
) cell that is the second cell formed in spermatogenesis. spermatogenesis and oogenesis – Gamete Formation essay Assignments

Step 3.
 The secondary spermatocytes then divide into spermatids, which are immature sperm cells. These stay connected to each other via cytoplasmic bridges, areas that connect the cells via their cytoplasm. This attachment coordinates development. Many genes required for sperm maturation are coded on the X chromosome, but not all sperm have an X chromosome due to being haploid. By staying connected via the cytoplasm (the cell’s watery interior), the new spermatocytes are able to share this genetic information.

Step 4.
 When fully developed, haploid (1
n
) male sex cells, the mature 
spermatozoa
, separate. spermatogenesis and oogenesis – Gamete Formation essay Assignments

Sperm production results in four individual sperm cells being produced from each precursor germ cell. It begins when the organism reaches reproductive age and continues throughout the male’s life span. By producing far more sperm than are needed (each ejaculation can contain 20 million sperm), the chances that at least one will make it to the female egg cell and fertilize it increase.

In spermatogenesis, the spermatogonia divide to produce the primary spermatocytes, which then further divide to produce secondary spermatocytes. These form the spermatids, which remain connected to each other until they are fully developed as spermatozoa, or haploid male sex cells.

The formation of an 
oocyte
, the female haploid (1
n
) sex cell, is called oogenesis. It begins with oogonia, which are the diploid (2
n
) cells that will further divide to form the egg cells. This process is complete before birth, so female organisms are born with all the oogonia they will ever have. For this reason, the formation of oogonia is not considered part of oogenesis proper, but it is vital to the process of forming oocytes. The formation of oocytes involves the following events:
Step 1.
spermatogenesis and oogenesis – Gamete Formation essay Assignments.The first true step of oogenesis is
oocytogenesis
, the process by which oocytes develop, which happens after a female is born. During oocytogenesis, the oogonia undergo mitosis to form the primary oocytes. A 
primary oocyte
 is a diploid (2
n
) cell that undergoes meiosis to produce the secondary oocyte (egg cell). It is thought that oocytogenesis is complete shortly after birth, but this idea has recently been challenged and is under investigation by researchers.

Step 2.
 
Ootidogenesis
 is the part of meiosis that produces the secondary oocyte from the primary oocyte. In this step, the primary oocyte undergoes meiosis, splitting its genetic material between two daughter cells. However, this process is halted in prophase I. The oocytes remain in this stage until triggered to continue during the female’s fertile period. During each fertile cycle, only some cells move forward in the process and are available for fertilization (in humans, just one or two; hundreds may be available for fertilization during a single cycle in species that lay many eggs at once, such as sunfish or seahorses).

Step 3.
 The oocyte continues through the end of meiosis I, forming one viable cell (the secondary oocyte) and a 
polar body
(a non-viable cell produced at the end of meiosis in females which contains no genetic material). However, this secondary oocyte is halted at metaphase II of meiosis II until fertilization occurs. spermatogenesis and oogenesis – Gamete Formation essay Assignments.

Step 4.
 Upon fertilization , the cell completes meiosis II, producing an 
ootid
 (a fertilized egg cell) and another polar body.

Oogenesis begins when the diploid (2
n
) oogonium undergoes mitosis to produce the diploid primary oocyte (2
n
). The primary oocyte enters meiosis but is halted early until the female enters her fertile cycle. The fertile cycle triggers the cell to finish meiosis I, producing the haploid secondary oocyte (1
n
) and a polar body (a nonviable cell). The secondary oocyte is halted in meiosis II unless fertilization occurs. Upon fertilization, the cell completes meiosis II, producing a single viable cell and other polar bodies. spermatogenesis and oogenesis – Gamete Formation essay Assignments.

Deoxyribonucleic acid (DNA) Essays

Introduction to DNA

DNA provides the blueprint for all traits an organism possesses. The structure of DNA serves to determine which traits are expressed.

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Deoxyribonucleic acid (DNA)
 is an organic molecule containing coded instructions for the life processes of an organism, which consists of nucleotides bonded together to form two complementary strands. Whether the organism has brown fur, has 14 legs, has green eyes, or reaches sexual maturity after 10 years of growth, it relies on its DNA to provide instructions that generate these traits. In 
eukaryotic
 organisms, DNA is found in structures called chromosomes. Deoxyribonucleic acid (DNA) Essays. Different species have different total numbers of chromosomes. For example, humans have 23 pairs, or 46 individual chromosomes. Chimpanzees, the closest living relatives of humans, have 48 individual chromosomes. Fruit flies, on the other hand, only have 8 individual chromosomes. There is even a species of fern that possesses more than 1,000 individual chromosomes.
Prokaryotic cells 
also have DNA, but instead of having chromosomes, they have a circular piece of DNA within their 
cell membrane
. This is called a plasmid. The structure of prokaryotic DNA is helpful when the organism reproduces. Because this DNA is not constrained by a nucleus, it can just be copied and then moved into the new cells.

Prokaryotes have a single circular strand of DNA, the molecule that determines every trait an organism expresses. Eukaryotes have multiple strands in the form of linear chromosomes, structures found in the nucleus. Deoxyribonucleic acid (DNA) Essays.

Structure and Composition of Cell Membrane Essay Assignments

Role of the Cell Membrane

Cells have a unique cell membrane that serves many functions, including controlling the passage of substances into and out of the cell and cell communication.

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Both prokaryotes and eukaryotes have a 
cell membrane
. This cell structure is a semipermeable membrane found outside the cytoplasm, or gel-like interior, of the cell. It is helpful to think of the cell membrane as a boundary that forms between the cell’s internal and external environment. The cell membrane has many functions. First, it defines a cell by enclosing cellular contents within the cell. Structure and Composition of Cell Membrane Essay Assignments.

Despite the difference in structure of prokaryotic and eukaryotic cells, they both have a cell membrane (a semipermeable membrane found outside the cytoplasm of a cell) that surrounds the inner contents of the cells. Structure and Composition of Cell Membrane Essay Assignments.

Second, it creates a barrier that selectively controls what enters the cell from the outside environment and what substances leave the cell. Because of selective permeability, only specific molecules are able to cross the cell membrane. Essential molecules such as nutrients are able to enter the cell, while waste is able to exit the cell. Molecule size also plays a role in this permeability. Small molecules such as water and oxygen are able to freely cross the cell membrane, but larger molecules such as sugars are regulated.Last, the cell membrane aids in cell communication. Receptors are proteins that are found on the surface of cell membranes or inside the cell. Receptors can serve as either receivers of extracellular signals or activators of intracellular processes. For example, some cells have receptors for hormones that play a role in the regulation of biological processes in which the cell takes part. The binding of the hormone to the receptor changes the activity of the cell. Cells also have receptors that can bind to circulating immune cells, helping the immune system detect the presence of disease-causing organisms or viruses. Structure and Composition of Cell Membrane Essay Assignments.

Cell Membrane Structure

The cell membrane structure is a lipid bilayer with proteins, carbohydrates, and other lipids embedded within.

Cell membranes all have the same basic structure, composed of two facing layers of lipids. However, cells may have a variety of other types of membrane components. Different cell types have unique sets of structures embedded within the basic membrane structure. Some cells may have membrane components found only in that specific cell type. In some cases, it is not the identity of the component but the number of specific components found on a certain type of cell that distinguishes it from other cells.

A 
phospholipid
 is a lipid molecule composed of two fatty acid tails. Both tails are attached to a phosphate head by a glycerol molecule. Phospholipids create a specific structural design of the cell membrane. Their behavior in aqueous solutions assembles them into bilayers. Within each bilayer, the 
hydrophilic
 (water-loving) phospholipid heads that face outside the cell contact the extracellular fluid (watery solution outside cells), and the hydrophilic phospholipid heads that face inside the cell contact the cytoplasm (contents of the cell enclosed by the cell membrane,). The 
hydrophobic
(water-fearing) tails of each layer face each other because the tails are resistant to water. Structure and Composition of Cell Membrane Essay Assignments.

The cell membrane consists of a phospholipid bilayer that contains both hydrophobic, or water-fearing, fatty acid tails and hydrophilic, or water-loving, heads. The hydrophilic heads are found toward the more aqueous sides of the cell (inside and outside).

Cholesterol
is a lipid component found in some cell membranes that associates with the head of phospholipids, and sits between adjacent phospholipids. It contributes to cell membrane fluidity by preventing adjacent fatty acids from getting too close and effectively solidifying. Cholesterol also plays a role in cell signaling by stabilizing the association of signaling molecules with the membrane, allowing them to perform their function. Structure and Composition of Cell Membrane Essay Assignments.

The lipid bilayer is a thin polar membrane made of two layers of lipid molecules. Many different substances make up the cell membrane and contribute to its selectively permeable nature. Structure and Composition of Cell Membrane Essay Assignments.

A 
carbohydrate
is an organic molecule that contains carbon, hydrogen, and oxygen and provides energy to cells. Carbohydrates are commonly found on the exterior surface of the cell membrane. Carbohydrates can form hybrid molecules such as glycoproteins (carbohydrates bound to proteins) and glycolipids (carbohydrates bound to lipids). Glycoproteins and glycolipids are both found in cell membranes, often as receptors for cell signaling. The purpose of the carbohydrate portion of these molecules is to aid in cell-to-cell recognition by binding to complementary structures on adjacent or circulating cells, such as immune cells.Proteins are found both embedded within the lipid bilayer and associated with the surface of the membrane facing the inside of the cell. Many cell membrane proteins function in cell signaling and in transport of substances across the membrane. Some proteins are involved in the cell shape and structure of tissue by binding to the cell’s cytoskeleton, to the extracellular matrix, or to adjacent cells. Membrane proteins can also be enzymes that are involved in cellular processes, particularly in the membranes of the mitochondrion and the chloroplast. Structure and Composition of Cell Membrane Essay Assignments.

Cell Membrane Proteins

Proteins associated with cell membranes are either associated with one side of the membrane or are embedded in it and have several roles in membrane activity.

Proteins of the cell membrane can be either embedded in the membrane or associated with one side of the membrane. A 
peripheral protein
 is a protein that is not embedded within the lipid bilayer but is closely associated with the membrane through non-covalent interactions with other membrane components. Peripheral proteins are often involved in cell communication and enzymatic activity. An 
integral protein
 is a protein that is embedded within the cell membrane. Some integral proteins are inserted into one side of the membrane but do not go all the way across the membrane. Other integral proteins traverse the entire lipid bilayer and are called transmembrane proteins. Transport proteins are classified as a type of integral protein. There are two types of transport proteins: carrier proteins and channel proteins.

A 
carrier protein
physically binds to a molecule and facilitates its transport across the cell membrane’s lipid bilayer. Carrier proteins have a specific binding site for an ion or molecule. When the binding site is occupied, the carrier protein changes shape. The change in shape allows the bound substance to have access to the opposite side of the cell. One example of a carrier protein is the glucose transporter protein, which moves glucose across the cell membrane. Structure and Composition of Cell Membrane Essay Assignments.

A 
channel protein
, also known as an ion channel, creates a pathway that has a hydrophilic interior for ions (polar molecules) to pass through. The hydrophilic interior of these proteins is exposed to the cytoplasm and extracellular fluids. They have a hydrophilic channel within their core that creates an opening in the cell membrane. Some channels can be opened or closed in response to a stimulus, and these are called gated channels. Gated channels are critical to the functioning of nerve cells by allowing the controlled movement of ions that propagate the signal. Sodium and calcium ion channels are examples of channel proteins.

Fluid Mosaic Model of Cell Membrane Structure

The fluid mosaic model describes the nature of the cell membrane in that the membrane is not rigid and it contains many components.

The fluid mosaic model describes the changeable structure of the cell membrane. The term 
fluid
refers to the nature of the lipid bilayer itself. The phospholipids do not form rigid sheets; rather, the lipids form a flexible film of movable components. This is somewhat similar to a layer of soap bubbles, where each bubble can move in relation to the rest of the bubbles but is still connected to the whole. Because the lipids “flow” past each other, the membrane resembles a fluid. Structure and Composition of Cell Membrane Essay Assignments.

The term 
mosaic
refers to the membrane in which other component molecules such as proteins, cholesterol, and carbohydrates are embedded or with which they are associated. Many of these component molecules can change location within the plane of the membrane. In some cases, the movement of membrane components is driven by specific intracellular and extracellular signals. Certain proteins may also be localized to a particular part of the cell membrane, either for functional or structural reasons. For example, carrier proteins are often grouped together on the membrane to more efficiently transport material across the membrane and reduce the energy needed for this transport. Structure and Composition of Cell Membrane Essay Assignments.

Eukaryotic cells Essays

Eukaryotic cells contain a nucleus that directs functions and activities of the cell’s organelles.

Eukaryotes are cells categorized as having a nucleus and a variety of other membrane-enclosed organelles. Eukaryotes include plants, animals, fungi, and protists. Eukaryotic cells have greater mass than prokaryotic cells and have far more internal complexity. Within each eukaryotic cell, internal membranes create multiple compartments. These compartments, called organelles, carry out specific functions through independent chemical reactions. Eukaryotic cells Essays.

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In eukaryotic cells, the DNA is separated from the rest of the cell in the nucleus by the nuclear membrane. This separation is important in the regulation of protein synthesis, as the cellular structures that produce proteins are found outside the nucleus. The nuclear membrane limits the type of molecules that can reach the DNA and also limits the type of molecules that can leave the nucleus and reach the protein synthesis machinery of the cell. Eukaryotic cells have more precise regulation of the production of proteins and their RNA intermediates than do prokaryotes, in which the DNA is not sequestered from the rest of the cell.

One feature of eukaryotic cells, particularly within multicellular organisms, is the variety of shapes and sizes of these cells. The shape of the cell is related to the function it performs. Nerve cells, for example, have fingerlike projections that allow them to communicate over a distance. In addition, cells aggregate to form larger structures, such as tissues and organs, that perform specific functions. Eukaryotic cells Essays.

Types of Human Cells

Eukaryotic cells differ widely in size and shape. Nerve cells (neurons) carry messages from the brain to other parts of the body. Blood cells transport oxygen and nutrients to the cells. Cardiac muscle cells are found in the heart. Skin surface cells provide a layer of protection. Eukaryotic cells Essays.

Membrane-Bound Organelles

Eukaryotic cells contain a variety of organelles, each with specific functions within the cell. The complexity of eukaryotic cells can be compared to the various body systems of mammals.

The nucleus fulfills a similar function as an animal’s brain, directing a cell’s growth, division for reproduction, activities, and death. The nucleus houses most of the DNA. Within the nucleus is the 
nucleolus (plural, nucleoli)
, a site within the nucleus where ribosomal subunits are assembled before export to the cytoplasm. RNA carries the message encoded on DNA from the nucleus into the cytoplasm, the combination of cytosol, organelles, and other components in the interior of the cell. Eukaryotic cells Essays.

An 
endomembrane system
 is a system of membranes suspended within eukaryotic cells to partition the cells into functional compartments, such as the Golgi apparatus and endoplasmic reticulum. The 
endoplasmic reticulum (ER)
 is a network of membranes that helps process molecules in a cell and transports cell materials. The endoplasmic reticulum may be rough, if studded with ribosomes, or smooth, without ribosomes. The 
Golgi apparatus
 is an organelle that attaches chemical markers to molecules produced in the endoplasmic reticulum in order to transport the molecules to their places inside or outside a cell. It is a group of stacked and flattened membrane sacs. Molecules move from the endoplasmic reticulum through the successive sacs of the Golgi apparatus.

A 
lysosome
 is an organelle that digests bacteria that enter a cell, eliminates toxins, and recycles unneeded cell materials. A 
peroxisome
is a structure in eukaryotes that transforms fatty acids into sugars and aids chloroplasts in oxidizing plant sugars. Peroxisomes also contain enzymes involved in the degradation of lipids and alcohols. Eukaryotic cells Essays.

Called the power plant of eukaryotic cells, a 
mitochondrion (plural, mitochondria)
 is an organelle that changes energy from food into energy a cell can use. It has a smooth outer membrane and an inner membrane that is highly folded. A eukaryotic cell has several mitochondria, which are the site of cellular respiration, an activity that removes chemical energy from food. Mitochondria also have their own DNA and can replicate independently of the cell’s replication. Both plant and animal cells derive energy from cellular respiration.

Plant cells have chloroplasts that are involved in photosynthesis, the transformation of radiant energy from the sun into chemical energy in the bonds of sugars. A 
chloroplast
is a membrane-bound organelle found in plants and some other organisms that captures energy from light and converts it into chemical energy. Chloroplasts have two membranes and groups of stacked membrane sacs inside. Chloroplasts have their own DNA and can replicate independently of the cell’s replication. Eukaryotic cells Essays.

Junctions and Other Structures

Multicellular organisms have a variety of cells that have to maintain close connections with other cells to form tissues in order to fulfill their function in the organism. The type of connections between cells depends on the function that the resulting tissue will have within the organism. A cell 
junction
 is a point at which cells are bound together, usually connecting cells to other cells. The types of cell junctions include tight junctions, anchoring junctions, and gap junctions.

Tight junctions seal two cells together to form a tissue barrier that blocks unwanted substances from moving between cells, similar to a watertight seal.

Anchoring (or adhesion) junctions link one cell to its neighbor via their cytoskeletons. Desmosomes bind cells in animals.

Gap junctions allow materials to move through cells. Molecules of water and oxygen, as well as electrical signals, pass through gap junctions of cells. When a muscle flexes, the signal to flex moves along neurons through gap junctions to the brain. Plasmodesmata connect cells in plants.

Cells are bound to each other at cell junctions. The three types of cell junctions are tight junctions, anchoring junctions, and gap junctions.

There are two other common structures in cells. Eukaryotic cells have a cytoskeleton that determines their shape. The 
cytoskeleton
 is a network of filaments that gives the cell its shape and forms the support network for cell functions, such as cell division. The cytoskeleton is formed by a network of different types of protein filaments and extends throughout the cell. The filaments of the cytoskeleton form the support network for the transport of materials within the cell, aid in cell movement, and form the spindle involved in separating chromosomes during cell division. The 
centrosome
 is a structure in the cytoplasm of animal cells that coordinates the formation of microtubules, which allow cell division to proceed during reproduction. Eukaryotic cells Essays. It is composed of a ring of protein tubes called microtubules, which are also part of the cytoskeleton. The centrosome directs the formation of the spindle involved in cell division. Together, the centrosome and the spindle ensure that each new cell has an equal number of chromosomes by pulling the chromatids apart during reproduction.

Plant Cells

Plant cells are eukaryotic cells with a cell wall and organelles (called chloroplasts) involved in photosynthesis.

While both animals and plants are composed of eukaryotic cells, their cells have different structures and functions. Plant cells are generally rectangular and tend to be larger than animal cells. Plant cells, like animal cells, join together to form tissues. Plants have far fewer types of tissues than higher order animals, but the basic cell structure of plants (such as algae and a giant sequoia) are the same. Eukaryotic cells Essays.

Plants are autotrophs; they produce their own food and form the primary level in most food chains. Food production occurs because plant cells have specialized membrane-bound organelles called chloroplasts. Chloroplasts contain chlorophyll, which provides the plant’s green hue and is the plant’s means of absorbing light energy from the sun. The sun’s energy is combined with water and carbon dioxide in the plant’s process of photosynthesis. The end products of photosynthesis are sugars and waste oxygen. Eukaryotic cells Essays.

While chloroplasts perform the primary task of food production, other organelles play a role in cellular metabolism. Vacuoles are membrane-bound sacs, much like a bubble, that store nutrients and waste products. Water stored in vacuoles helps keep plant stems, limbs, and branches rigid. The crunch of a carrot comes from the vacuole’s ability to maintain turgor pressure, the pressure of water against the plasma membrane, within each cell. That pressure supports the cell wall and the overall structure of the plant. When the vacuoles do not retain sufficient water, plants wilt. Organelles called peroxisomes have a variety of tasks related to conversion of waste from cellular metabolism. These organelles transform fatty acids into sugars and aid chloroplasts in oxidizing plant sugars.

Plant cells have stiff cell walls that are made of cellulose, which protect both the cell itself, and the plant as a whole. Plant cells join together to form tissues, such as the vascular tissues phloem and xylem. The phloem transports sugars away from the leaves, while the xylem transports water, minerals, and other nutrients upward from the roots. Other types of cells form protective tissue layers to help plants retain water. Eukaryotic cells Essays.

Plant Cell

Specialized structures of plants cells include a stiff cell wall for protection and chloroplasts that facilitate photosynthesis. Being eukaryotic, plant cells also contain a nucleus.

Animal Cells

Animal cells are eukaryotic cells that generally lack a cell wall.

Animal cells are eukaryotic cells enclosed within a plasma membrane and contain a variety of membrane-bound organelles suspended in the cytoplasm. Like plant cells, animal cells have a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and ribosomes. They may also have centrioles, cilia or flagella, and lysosomes, which are not usually found in plant cells.

A centriole is made up of a ring of nine groups of fused microtubules, long strands of protein that form tubes. These structures are part of the cytoskeleton, a lattice-like structure that protects cells. In an animal cell, a centrosome consists of two centrioles arranged perpendicular to each other. Centrosomes are organelles that divide and migrate during reproduction Eukaryotic cells Essays. They provide strength to a cell’s structure and pull apart chromatids (threadlike strands containing a double helix of DNA) when cells divide.

Some animal cells also contain cilia or flagella, structures that are anchored in the cell membrane. Cilia and flagella push fluids along the surfaces of cells. Flagella are thin, whiplike tails that assist cells in movement. A sperm cell, for example, has a flagellum to enable it to move to find and fertilize an egg. 
Giardia
 is a common protist parasite that has a flagellum. Cilia are tiny hairlike structures found on the surface of unicellular animals, such as paramecia, and function in locomotion. Cilia are also found on the cells lining the human respiratory tract, where they help remove debris from the lungs.

Animal cells contain lysosomes, which are organelles that hold enzymes created by the cell that break down complex molecules such as proteins. Lysosomes fuse with vacuoles that contain material derived from within the cell, such as damaged organelles, or ingested from outside the cell. Once the membranes fuse, the contents of the vacuoles are exposed to the enzymes in the lysosome and are degraded. The components can then be reused by the cell.

Animal cells exhibit a variety of shapes and sizes that are related to their function Eukaryotic cells Essays. Elongated smooth muscle cells, round white blood cells, and spiky neurons all have the same basic cellular components.

Animal Cell

Animal cells are eukaryotic. Specialized structures of animal cells include lysosomes, the “digestive system” of the cell. Animal cells may also have cilia or flagella, which assist in movement of the cell within the fluids around it.

Comparison of Plant and Animal Cells

Plant and animal cells share some structures. The differences in structures help each type of cell carry out its specific functions. Eukaryotic cells Essays

Prokaryotes: Bacteria and Archaea Essays

Prokaryotes: Bacteria and Archaea

Learn all about prokaryotes in just a few minutes! Jessica Pamment, professional lecturer at DePaul University, explains the similarities and differences between bacteria and archaea. Prokaryotes: Bacteria and Archaea Essays.

Bacteria and Archaea

The two prokaryotic domains, Bacteria and Archaea, contain diverse single-celled organisms that exhibit a wide variety of metabolic abilities.

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Although members of the domains (largest taxonomic groupings) Bacteria and Archaea have many important differences, they are united by their general cell type. Unlike members of the domain Eukarya, Bacteria and Archaea are prokaryotes. Prokaryotic cells lack a membrane-bound nucleus to contain the DNA, other membrane systems such as the endoplasmic reticulum, or membrane-bound organelles such as mitochondria, making them much smaller and simpler than eukaryotic cells. Prokaryotic organisms are all single-celled. Though some prokaryotes live together in colonies or attached in a group, they do not share the same level of connection and coordination as a multicellular organism. Prokaryotes: Bacteria and Archaea Essays. Prokaryotes carry their genes on a single circular chromosome, unprotected in the gel-like cytoplasm filling the interior of the cell. They may also carry some genetic material in plasmids. A
plasmid
 is a small, circular piece of bacterial DNA that replicates on its own and can be transferred between cells. As single-celled organisms, their reproduction is equivalent to cell division. Prokaryotes: Bacteria and Archaea Essays. Prokaryotic cell division consists of replication of the single chromosome followed by a simple split of the cell, known as binary fission.

Prokaryotes as a group have diverse mechanisms for obtaining energy and carbon, collectively known as metabolic processes. Some prokaryotes are phototrophs. A 
phototroph
 is an organism that obtains energy from the sun. A 
chemotroph
 is an organism that obtains energy through chemical reactions with certain organic or inorganic compounds, such as those containing sulfur. An 
autotroph
 is an organism that can make its own food. Prokaryotes: Bacteria and Archaea Essays. Autotrophs get their carbon from the atmosphere as carbon dioxide, or from other inorganic sources. A
heterotroph
 is an organism that obtains energy and carbon from consuming other organisms. Heterotrophs obtain carbon from organic molecules. Bacteria can be described by combining their source of energy and their source of carbon. For example, a photosynthetic bacterium is considered a photoautotroph because it obtains its energy from the sun and its carbon from the atmosphere. There are prokaryotic species in each metabolic category.

There are multiple ways a unicellular organism called a prokaryote obtains carbon and energy. In general, an organism will first be categorized as either an autotroph or heterotroph. Autotrophs rely on carbon dioxide as their carbon source while heterotrophs rely on organic molecules as a carbon source. These organisms are further divided based on the method they use to get energy and carbon. Each method is used by at least one prokaryote. Prokaryotes: Bacteria and Archaea Essays.

Bacteria

Bacteria are small unicellular organisms that obtain food through a variety of processes.

The domain Bacteria is further classified into the kingdom Eubacteria and is the most diverse kingdom (second largest taxonomic grouping). It represents the greatest number of organisms, called by the generic term bacteria, although individuals in this kingdom are among the smallest of all life. They are so diverse that humans and potatoes are more closely related than many bacterial species are to each other. In addition to bacteria being metabolically diverse as a group, some individual bacteria are able to change metabolic strategies based on the environment. Prokaryotes: Bacteria and Archaea Essays. For example, some bacteria are able to use oxygen when it is present and switch to fermentation when oxygen is absent. Bacteria reproduce through simple cell division, but they can also exchange genetic material through conjugation.
Conjugation
 involves the direct transfer of genetic material between two bacteria, using a small piece of DNA called a plasmid.

Although a relatively small proportion of pathogenic, or disease-causing, bacteria receives the most public attention, many bacteria perform critical ecological functions. Arguably the most important bacterial contribution to life on Earth was the transformation of the atmosphere by ancient photosynthetic cyanobacteria that made life possible for those organisms that require oxygen. However, bacteria still provide important ecological services, Prokaryotes: Bacteria and Archaea Essays.

All organisms require nitrogen for the formation of proteins. However, the nitrogen found in the atmosphere is not in a form that most living organisms can use. Some bacteria, called nitrogen-fixing bacteria, can convert atmospheric nitrogen into ammonia and other nitrogen-containing compounds. These compounds can then be used by plants, and subsequently animals, to supply their nitrogen needs. In this way, bacterial species are responsible for modifying atmospheric nitrogen to a form that eukaryotic organisms can use.

Bacteria function in the cycling of other elements through their role as decomposers. A 
decomposer
 is an organism that breaks down dead materials and organic wastes, releasing energy within an ecosystem. Bacteria break down these materials to release carbon, nitrogen, phosphorus, and other elements back into the ecosystem. Without the decomposing actions of bacteria and other organisms such as fungi, the supply of chemical elements in the environment would diminish and the continuity of life would cease.

A growing body of evidence has shown the importance of the microbiome, the types of organisms living in the human digestive tract. The specific organisms present, or absent, in the intestinal microbiome can play a role in obesity, diabetes, cardiovascular disease, and diseases of the digestive system. In addition, differences in intestinal microbiome can explain some nutritional deficiencies. Understanding the role of intestinal bacteria in health is a major area of research. Prokaryotes: Bacteria and Archaea Essays.

Major Groups of Bacteria

Gram staining is a method used to identify, based on cell wall structure, members of the different types of bacteria, such as Proteobacteria, Spirochetes, and Cyanobacteria.

Scientists use a method called a 
Gram stain
 to differentiate between types of bacteria based on cell wall structure. Developed in 1884 by Danish bacteriologist Hans Christian Gram, this staining method was originally developed to make bacteria more visible, not differentiate between variations. Prokaryotes: Bacteria and Archaea Essays. This method allows researchers to visualize the peptidoglycan layer found between the cell membrane and cell wall. Gram-positive cells have a thick layer of peptidoglycan that stains purple. Gram-negative cells have a thin layer of peptidoglycan and stain red. Gram-negative bacteria include Proteobacteria, Chlamydias, Spirochetes, and Cyanobacteria.

Proteobacteria are a diverse gram-negative group of bacteria that contain both oxygen-loving (aerobic) and oxygen-avoiding (anaerobic) species. 
Salmonella
 and 
E. coli
 are members of this group, as is the bacteria behind stomach ulcers.

Chlamydias are parasitic, requiring an animal host for survival. Their cell walls lack peptidoglycan, and one species from this group causes the human illness chlamydia.

Spirochetes move in a rotating spiral fashion with the help of a motile cell structure, the flagella. Not all are pathogenic, but Lyme disease is caused by a bacterium in this group. Prokaryotes: Bacteria and Archaea Essays.

Cyanobacteria are photoautotrophs that play an important role in the carbon cycle, converting carbon dioxide into organic compounds using energy from the sun. Ancient cyanobacteria were the evolutionary precursors of modern chloroplasts, the organelle involved in photosynthesis, and also helped to oxygenate the early Earth.

Gram-positive bacteria are responsible for strep infections, botulism, and anthrax.

Kingdom Eubacteria contains prokaryotic unicellular organisms. They can be found in just about every environment on Earth. They can be found in the water, in the air, and even in close association with animals, such as this koala. The bacteria live in the intestines of the koala and allow it to digest the leaves of eucalyptus. Prokaryotes: Bacteria and Archaea Essays.

Archaea

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Archaea are prokaryotic organisms with a variety of structural and metabolic characteristics that distinguish them from bacteria.

The original classification of the Archaea was to place them within the kingdom Archaebacteria. While this classification scheme is not widely used anymore, it is still appropriate to include when comparing characteristics of all the kingdoms. This maintains consistency in the taxonomy and allows for six kingdoms instead of just five. This helps to further identify where these organisms sit in the hierarchy of life. Archaea share some characteristics with domain Bacteria, but genetic and other evidence indicates that archaea diverged from Bacteria a very long time ago Prokaryotes: Bacteria and Archaea Essays. Archaea are currently thought to be more closely related to eukaryotes than to bacteria, their fellow prokaryotes. Archaea cells lack a nucleus or membrane-bound organelles, like bacterial cells. They also have a single circular chromosome. However, archaea cell walls do not have peptidoglycan, while bacterial cells do. Archaea also share some typically eukaryotic traits, many related to DNA. Like eukaryotes, some archaea have histones. A
histone
 is a protein used to package DNA in condensed chromosomes. These proteins assist in DNA structure and control of gene expression. Archaea also have introns in some of their genes. An 
intron
 is a DNA sequence within a gene sequence that does not code for a specific protein; these must be removed from the mRNA during processing. This is a trait found in domain Eukarya but not in domain Bacteria. Archaea RNA polymerases (enzymes used to make mRNA) are also more similar to those of Eukarya than to those of domain Bacteria.

Archaea have some unique traits that are not shared by any other domain. For example, many have lipids with branches in their cell membranes, while organisms of other domains have unbranched lipids in the cell membrane. This trait is thought to help stabilize membranes at high temperatures, as it is more common in heat-loving archaea. The members of Archaea gained reputations for being extremophiles. An 
extremophile
is an organism that thrives in extreme conditions such as extreme salinity, pressure, chemical concentration, or temperature. This is partially because the first identified archaea were found under conditions that would not support most other life. For example, some archaea live in the very salty Great Salt Lake in Utah. Another example is the archaea that live near deep-sea hydrothermal vents Prokaryotes: Bacteria and Archaea Essays. They thrive in very hot, high-pressure environments. Some archaea go beyond merely tolerating these extreme conditions and require them to survive. However, not all archaea live in such extreme conditions. For example, some reside in the human gut. A 
methanogen
 is an organism that uses carbon dioxide and hydrogen gas for energy. Methanogens release methane as a by-product. Among other functions, these archaea assist in digestion in some grass-eating animals, such as cattle. Oxygen is toxic to these archaea.

Archaea can be found in places where most other life cannot survive, such as under high-temperature, high-pressure conditions near deep-sea hydrothermal vents. Prokaryotes: Bacteria and Archaea Essays.