Category: Resources

8 Most Useful Bill Nye Videos To Watch

-Even if you are in college.

Bill Nye the Science Guy hasn’t produced new episodes since the end of Season 5 in 1998, but the show’s namesake host remains active in the promotion of science – and many of his videos remain outstanding content to watch even if you’re in College (or beyond).

Here at Biology Junction, our focus is on our own namesake subject, and that’s what this list focuses on – but for those of you who came here for a more general list, we’ve also included a few non-Biology videos down at the bottom. These videos are helpful regardless of what type of science you’re interested in, so everyone should take a look at them.

How We Chose These Videos

What good is a list without an explanation of how we made it? It wouldn’t be good science if we just threw it up here! Truth is, though, creating this list wasn’t very hard. First, we narrowed our list of sources to the best selections of Bill Nye videos – his classic show and the more-recent Greatest Discoveries series.

Next, we considered how useful each topic is to know. For students studying biology, it does no good to dive into topics more advanced than you’re ready for. Fortunately, most of Bill Nye’s videos are accessible even to beginners and provide a strong foundation for the topic. This ended up being a minor concern, but we were determined to go through the process.

Finally, we checked for the availability of videos. It doesn’t help to be told to watch a video if you can’t find it. A simple search should be enough to locate any of the videos on this list. If that fails, you should be able to get them from your library or preferred streaming service. We had a preference for videos that are freely available since budgets can be tight in college, but that didn’t significantly impact this list.

For our non-Biology videos, we used a similar process. Instead of emphasizing Biology, though, we decided to focus on the foundations of science and the information that’s most useful for everyone to know.

The Best Biology Videos From Bill Nye

Here are our top choices for Biology videos.

1: Biodiversity (S1 E9)

Biodiversity is the 9th episode of Bill Nye the Science Guy, and while it’s not the first to feature a Biology topic, we think it’s easily one of the most important episodes. This video focuses on more than just where things live – it also explains the concept of ecosystems and how important it is to have a variety of living things in each area.

Fish in the habitat

Arguably the most important lesson of this episode is understanding that ecosystems are far more complex than figuring out which living things eat each other. Each part of an ecosystem affects all of the other parts. That’s why we have to be so careful when introducing plants or animals to new habitats – if the ecosystem isn’t ready to handle it, the whole thing could collapse.

A second lesson to focus on is how ecosystems can vary in size – and, in many cases, overlap each other. The Great Barrier Reef has its own ecosystem, but it’s part of the larger Pacific Ocean – and from there, it ultimately affects all life on the planet (even if the impact isn’t obvious).

Understanding biodiversity is critical to understanding biology as a whole. Life does not exist in a vacuum – not unless we put it there, anyway. Environments affect life and vice versa, and if you want to understand why something is the way it is, you have to look at the bigger picture.

2: Cells (S1 E17)

cells

Cells are a fundamental component of life – and even if you think you understand them, it’s good to get a refresher on the topic before you start your studies. The main reason for this is that when we say something “affects an organ”, what we mean is “it affects certain cells of the organ in a particular way”.

For example, if you want to understand why too much alcohol can hurt the liver, you need to look at its impact on the cells of the liver. If you want to heal that liver when you’re done, you have to figure out what will encourage the cells to do that. Cells are the ultimate “micro” topic in biology, making the Bill Nye cells video easily one of the most important episodes for biologists to watch.

3: Food Web (S2 E6)

It’s hard to talk about biology without eventually talking about food – but how things get their food is a little more complicated. Only watch this video after you’ve watched Biodiversity, because that video provides some important groundwork for this topic.

The short version is that a food web describes how each part of an ecosystem gets its food. Ultimately, each living thing gets food either from other living things (like insects, plants, or rodents) or from the sun. Every living creature is ultimately dependent on plants – who, let’s not forget, are often nourished by the uneaten bodies of dead creatures.

(If you’re having flashbacks to a certain Disney movie about a young lion, there’s a reason for that – the Circle of Life, where living things depend on each other, is quite real.) Watch Food Web

4: Plants (S3 E3)

Given how important plants are to the previous video, now’s a good time to get a refresher on what they are, how they work, and what sort of impact they have on our lives. The crazy thing is how plants can synthesize their own food as long as they have sunlight, water, and carbon dioxide – though healthy soil and a few other nutrients certainly help.

plant

Plants are also important for their impact on other aspects of Biology. For example, many medicines are made from plants or plant by-products and affect certain living things in specific ways. Once we understand how something works, we can start figuring out the best way to make use of it.

This is particularly helpful if you’re looking for a job with biology. Most of your work will likely involve seeing how various inputs (types of food, situations, etc.) affect living things, and plants will be a part of that. Studying life alone is a limited topic – but there are endless possibilities when studying the way things affect life.

5: Populations (S3 E19)

Populations are a group of similar living things living in a set area. We often refer to the population of the human race, but we may also talk about the population of a specific city, voting district, or another region.

sunset with population

In biology, the most important thing is understanding the populations of other living things, how they’ve changed over time, and what’s caused them to do so. As you learned in videos like Biodiversity and Food Web, living things all affect each other – and a sudden rise or drop in one population will ripple across the ecosystem and begin affecting other creatures.

There may not be as many fancy names or scientific terms here, but it’s still worth watching this video to ensure you have a good grasp of the fundamentals of biology.

6: Biology – Greatest Discoveries

Finally, Bill Nye’s Greatest Discoveries video on Biology rounds out the best videos on this topic with a look at 13 of the most important discoveries in biology. This includes a discussion on the discovery and impact of:

  • Microorganisms like bacteria, blood cells, and sperm
  • The Cell Nucleus that functions at the center point of most cells
  • Archaea, microorganisms that lack a cell nucleus but aren’t quite like bacteria
  • Cell Division, the process of growth and, in many ways, life itself
  • Sex Cells and how they differ from most other types of cells
  • Cell Differentiation and how different types of cells are made
  • Mitochondria, which are separate from cells but provide a critical function for metabolizing chemicals
  • The Krebs Cycle, which is how protein, fats, and sugars are turned into energy
  • Neurotransmission, which centralizes the body’s ability to control itself
  • Hormones, which are far more complicated than teenage urges
  • Photosynthesis, a process where light is turned into chemical energy
  • Ecosystems, a quick look back at larger ecological units
  • Tropical Biodiversity, or why warm and sunny places tend to have a much greater variety of life

Together, all of these are important for biologists to know.

The Best Overall Science Videos From Bill Nye

Whether or not you’re focused on biology, these videos are helpful for improving your overall understanding of science and are worth watching at any age.

1: Pseudoscience (S4 E9)

Many things that sound like science but aren’t. These things are often called pseudoscience, and learning how to recognize them is a valuable skill for any scientist. Fortunately, the entire topic can be brought down to a few simple principles.

First, science involves testing claims and ideas. If somebody says something can’t be tested, then it’s not within the realm of science and shouldn’t be treated as such. In those cases, it’s okay to say “perhaps we’ll never know for sure”.

Second, extraordinary claims require extraordinary proof. In other words, the more important your claim is, the more you need to support it with verifiable evidence. As the person making a claim, it is your job to provide corresponding proof. It is not the job of others to demonstrate that you’re right.

Furthermore, your results should be reproducible. Proper science only happens when someone tries to prove you wrong – fairly, of course – and fails to do so. If you repeat an experiment and keep getting results, you don’t have any answers – just more questions to ask.

Finally, you should learn critical thinking. This graphic is especially helpful for that and provides many questions that help you uncover the truth. For example, when presented with a claim, you may want to figure out who benefits from it, what the best/worst case scenarios of it are, where it might be a problem or solution, what might make it unacceptable, why people might need it, and how to approach it safely.

In many cases, purveyors of pseudoscience are simply looking to profit from your ignorance. As a scientist, it is your duty to see past things like that and uncover the truth. Watch Pseudoscience now.

2: Measurement (S5 E17)

Coming in as one of the last episodes ever aired, Measurement is something that honestly should have been one of the first videos they made. Measuring things is critical to the foundations of science as a whole. Proper measurements provide objective, verifiable information using a common set of standards, and it’s impossible to overstate how important this is.

There are a few important things to learn from this video, Measurement.

First, there are many ways of measuring things. You can measure units (members of a population), dimensions (the size of something), time (how long it takes something to happen), effects (what happens), and many other topics.

Second, you’ll learn why things should be measured. It’s not just to expand the amount of information we have, though that’s valuable in and of itself. Instead, measurements help us understand what’s different about two subjects so we can proceed to uncover why and how that difference occurred.

Taken far enough, this can lead to discoveries, such as finding that one person in a neighborhood didn’t get sick because they ate a particular herb.

Measurements are almost never a focus in and of themselves – but they’re a vital part of most scientific activities. If you want to be a scientist, then you’re almost certainly going to do a lot of measurements over the course of your career. That makes this innocent-sounding video one of the most helpful episodes of Bill Nye.

Significance of Editing and Proofreading Your Biology Research Essay

A review essay for the biological sciences serves to discuss and synthesize key findings on a particular subject

Seasoned writers know that the most critical stage of writing academic papers is always editing. While editing, you catch most of the standard mistakes and polish your papers. Properly polished papers often receive much better grades than raw ones because the general neatness of your paper and correct grammar are what most attract the reviewer’s attention. 

Suppose you want to create a decent biology research essay, which is a significant paper for your academic performance. In that case, you must dedicate enough time for thorough editing and utilize some effective hacks and tips. We have gathered the most valuable advice for proper proofreading: with our guidance, you will be able to elevate your writing to the next level. If you are still not confident in your abilities to write close-to-perfect papers, contact the science essay writing service for urgent assistance. 

Why Proofreading Is So Important 

Proofreading is reviewing a work with a critical eye for typos, grammatical mistakes, and punctuation issues. A typical proofreader’s duties include making sure all citations and formatting are consistent and pointing out any instances of ambiguity or misinterpretation. Proper proofreading aids in fixing mistakes such as run-on phrases, fragmented sentences, and comma splices. Little mistakes may slip your mind while you are engrossed in your research and writing. Proofreading is a great way to catch and repair these mistakes.

To be clear, proofreading is not the same as editing. Editing and proofreading are sometimes confused for one another by researchers and PhD candidates. Keep in mind that editing is done before proofreading, and the aim is to make the research paper more explicit by fixing spelling and grammar mistakes and ensuring it is easy to read.

Tips on Proofreading Your Biology Paper

1 – Verify Your Biology Research

Proofreading and editing means not only finding typos and errors in spelling but also applies to finding logical flaws. The most essential part of your biology paper is research, and we recommend starting by rechecking each number and statement from your study. Otherwise, you risk writing the whole paper based on inaccurate facts, which can disaster your academic performance.

2 – Understand the Difference

When you edit your work, you check it for logic, coherence, structure, and argument errors.  Grammar, spelling, punctuation, formatting, and consistency are all aspects of a paper that should be carefully examined during proofreading. Editing focuses on the overall structure, whereas proofreading is more concerned with the specifics.

3 – We Recommend Always Starting with Editing

It is standard practice to modify a document first before moving on to proofreading. Doing so can save you the trouble of going back and addressing tiny mistakes that can easily be edited out.

Before you revise your work:

1. Give it a thorough and critical read-through.

2. Make sure it has a clear objective, research question, or hypothesis.

3. Check that the journals and your field’s specific guidelines for paper format and structure are followed.

We also recommend verifying that you have adequately introduced your study topic and provided the necessary background information in your work. Also, check that your work is well-organized and clearly displays your techniques, findings, and discussion. It would also be smart to remember that you need to include credible sources to back up your statements and conclusions throughout the paper and check that the manuscript acknowledges the limitations and consequences of your research.

4 – Listen to Feedback & Use Advanced Writing Tools

When you edit your work, you risk missing typos or weak points in your argument. Because of this, you need to use editing tools and comments to improve your paper. Software or online platforms exist to assist with many aspects of document editing, such as checking for plagiarism, readability, word count, and style.  Another option to help you find typical mistakes in your writing is to utilize a grammar or spell checker. On the other hand, you shouldn’t put all your faith in these tools—they may miss inevitable subtle mistakes or details in your paper. The best way to improve your paper is to get comments from people you respect, such as classmates, bosses, or mentors. They will be able to provide you with honest, helpful criticism. Pay attention to their feedback and change your paper based on what they say.

5 – Apply Best Proofreading Techniques

When you proofread your work, you run the risk of missing typos or grammatical mistakes that you’ve grown accustomed to. Use these proofreading approaches to make your work more correct.

To catch typos or strange phrasing you would miss when reading it silently or on your computer, you could print a copy of your paper and read it out loud. Consider reading your paper backward: it will force you to concentrate on the structure and spelling of each word rather than the overall meaning or flow of the sentences. A checklist or guide can remind you what to search for and how to fix any mistakes or inconsistencies in your paper, while a ruler or finger can assist you in avoiding skipping or repeating lines or words.

6 – Double-Check Numbers, References and Symbols

Such mistakes will easily catch the attention of reviewers but can be hard to spot for an average writer. You write this number once at the start and never return to recheck it because you are sure that the stated information is absolutely correct. The standard proofreading practice is double-checking all facts and accurate information in your biology research.

7 – Focus on One Type of Error at a Time

Keep in mind that academic writing proofreading is no picnic. As you go through your text, focus on fixing one typical error type at a time. Checking for spelling, grammar, or punctuation errors could be a good place to start. This method can help you avoid accidentally missing potential mistakes. 

The Bottom Line 

Writing an excellent biology research essay requires diligence, perseverance, and proper proofreading. We recommend not only looking for spelling errors, but double-checking each number in your final draft and each fact from your study. The outstanding research paper is a balanced combination of accurate information, perfect writing, and impeccable quality, and thorough proofreading can help you guarantee all of these.

How to Write a Biology Essay

“The point of the essay is to change things.” –Edward Tufte

Writing a biology essay can be a complex task, requiring not only a deep understanding of the subject but also the ability to present scientific information clearly and effectively. Prepare well and exploit a structured approach to crafting a compelling and well-researched biology text. Some simple steps go from understanding the assignment and conducting detailed research to structuring your essay and incorporating credible sources so that you can reach academic excellence without any complications. For qualitative preparation check out biology essay examples on a trustworthy source and follow the expert instructions to ensure your text meets the high standards of scientific writing.

Use real-world examples and case studies to illustrate your points and demonstrate how they apply to your thesis when writing in Biology.

Understand the Biological Context

You will hardly create any qualitative content unless you clearly understand what you are going to write about. Identify the biological concept or phenomenon that is to be at the center of your writing. If you have any hesitations or your assignment seems ambiguous to you, consult your professor for clarifications or any educational assistant for further directions.

What can help you dive deeper into your biological context is also a literature review. Proceed through a thorough literature review to understand the current state of research on the topic. Look up databases like PubMed, Google Scholar, and institutional libraries.

Formulate a Hypothesis or Research Question

Pass on to generate a hypothesis or research question that is going to be the core of your essay. If your writing involves an experimental or observational study, formulate a clear, testable hypothesis. Develop a specific research question to guide your investigation if it’s a review or analytical essay. So, define the type of your text and formulate its central point respectively for further successful steps.

Conduct Detailed Research and Data Collection

Now that you know your context and your attitude as for the assignment it is time to back it up with the proof. Start with primary sources, covering research articles, original studies, and scientific experiments. When you have enough, pass on to secondary sources, such as review articles, meta-analyses, and books for broader context.

Additionally, biological research allows you to conduct data analysis to strengthen your essay arguments. If the step is relevant to your work, analyze raw data from experiments or existing datasets using statistical methods. Create or refer to graphs, tables, and figures to present data effectively.

Create and Follow a Structured Outline with Scientific Rigor

Sometimes it is very difficult to organize your work properly so that you can finish it on time and produce qualitative content without any delay. So the very next step is to create a structured outline with scientific rigor so that you can stick to it to write a fundamental essay.

● Abstract – if you are required to, begin with an abstract. Provide a concise summary of the essay, including the research question, methods, key findings, and conclusions.

● Introduction – the next step or the primary point when an abstract is not necessary is to write an introduction. For your introduction include detailed background information with references to key studies and findings. Explain the significance of the topic within the field of biology. And don’t forget to state your thesis or hypothesis clearly. The rest of your writing will be tied to it. Be confident you’ve singled out the central idea of your topic and the findings related.

● Methods – if necessary or stated in the assignment, dwell on the methods you’ve exploited when researching and writing. Provide a description of the experimental design, including controls, variables, and procedures. Add the list of materials and equipment used. Explain how data was collected and recorded. This part of the essay will be solid proof of your no-plagiarism work.

● Results – think of the way you are going to display the results of your research and organize them appropriately. Present data in an organizedmanner using figures, tables, and charts. Add statistical tests if used and their outcomes.

● Discussion – remember that you not only have to present the data and evidence you have collected but also analyze and show your attitude to the findings. Interpret the results in the context of the research question or hypothesis. Compare findings with previous studies and discuss similarities and differences. Be open about any limitations in your study or analysis.

● Conclusion – with the analysis of your findings ready, you should summarize your work with a proper conclusion. Dwell on how your findings support or disprove the thesis/hypothesis. Discuss the broader implications of your findings for the field of biology. Suggest areas for further research.

Make an outline and cover it step by step so that you have a logical and strong text in the end. This will help you to get everything important and finish up your essay on time. Usually with a scientific assignment, you don’t need the inspiration to guide you but should have a proper organization of the writing process to assist you. Outlining will be a crucial part of your well-organized work with the essay.

Incorporate Scientific Evidence

Your biological essay will be no more but the words compound together unless you exploit strong scientific evidence to support your arguments. Ensure all references are from peer-reviewed scientific journals or reputable academic sources. Use a consistent citation style (e.g., APA, MLA, Chicago) and include in-text citations and a bibliography to guarantee the genuineness and trustworthiness of your sources and proofs.

Exploit direct quotations sparingly; prefer paraphrasing and summarizing with proper citations. Put the evidence in between your personal conclusions and attitude to the issue you are addressing in your writing. This will display you have processed the question under study deeply and made your own conclusions out of your findings.

Biology essays often include scientific data, diagrams, and graphs. Ensure that these elements are accurately presented and relevant to your argument

Consider Formatting and Technical Details

Scientific essay requires a relevant approach to its formatting and presentation. Use proper scientific nomenclature, italicizing genus and species names (e.g., Homo sapiens). Make sure you exploit standard units of measurement (SI units) and provide conversions if necessary. Define acronyms and abbreviations the first time they are used. Pay attention to these points when proofreading and editing or get someone to help you with a fresh look. A thorough approach and consistency in details will only add to the quality of your essay.

Spend Time on Proofreading and Peer Review

Take care your scientific essay looks appropriate and proves your level of qualification. Proofreading and thorough review will help you create a desirable image for your writing. Check for grammatical errors, scientific accuracy, and clarity. Use apps and tools to optimize and speed up the process. If possible, have your writing reviewed by a peer or mentor in the field for additional feedback. Or reach out to professionals from online services for high-end proofreading and review.

Care about Adherence to Ethical Guidelines

In the age of tolerance, you should also be confident that your essay doesn’t diminish or offend anyone’s rights and position as to your topic under study. Begin with ethical considerations. If your writing involves discussing experiments on humans or animals, ensure it adheres to ethical guidelines and includes necessary approvals. Additionally, avoid plagiarism by properly citing all sources and using original language. Check your text for authenticity with the help of anti-plagiarism tools on the Internet but beware of scams for anyone to steal your work.

Biology Essay Conclusion

Writing a biology essay involves proper planning, thorough research, and attention to detail. Cover some essential measures so that you can craft a well-structured and scientifically sound text that effectively communicates your findings and arguments. Mind the assignment and formulating a hypothesis to presenting data and discussing implications since each element plays a crucial role in the overall quality of your work. Remember to adhere to ethical guidelines, properly cite all sources, and seek feedback from peers or mentors. With these tools and strategies, you’ll be well-equipped to produce a high-quality biology essay that displays your knowledge and analytical skills.

IMMUNODEFICIENCY NOTES

Immunodeficiency is the failure of the immune system to protect against disease or malignancy. Primary Immunodeficiency is caused by genetic or developmental defects in the immune system. These defects are present at birth but may show up later on in life. Secondary or acquired immunodeficiency is the loss of immune function as a result of exposure to disease agents, environmental factors, immunosuppression, or aging.

SECONDARY (ACQUIRED) IMMUNODEFICIENCIES

Immunodeficiencies associated with infections

Bacterial, viral, protozoan, helminthic and fungal infections may lead to B cell, T cell, PMN and macrophage deficiencies. Most prominent among these is acquired immunodeficiency syndrome (AIDS). Secondary immunodeficiencies are also seen in malignancies.

Immunologic abnormalities in the AIDS

All acquired immunodeficiencies have been outdone by AIDS that is caused by Human Immunodeficiency Virus (HIV)-1. This virus was first discovered in 1981 and the patients exhibited fungal infections with opportunistic organisms such as Pneumocystis carinii and in other cases, with a skin tumor known as Kaposi’s sarcoma. There are two major types of HIV: HIV-1 and 2, the former being the strain frequently found in North America. HIV is spread through sexual intercourse, infected blood and body fluids as well as from mother to
offspring. HIV, which was discovered in 1983, is a retrovirus with RNA that is reverse transcribed to DNA by reverse transciptase (RT) following entry into the cell. The DNA is integrated into the cell genome as a provirus that is replicated along with the cell. HIV-1 does not replicate in most other animals but infects chimpanzees although it does not induce AIDS in them. Severe combined immunodeficient mice (SCID) reconstituted with human lymphocytes can be infected with HIV-1. The HIV-1 virion consists of a viral envelope made
up of the outer lipid bilayer of the host cell in which are embedded glycoproteins composed of the transmembrane gp41 along with the associated gp120. The gp120 binds the CD4 expressed on host cells. Within the viral envelope is the viral core or nucleocapsid consisting of a layer of matrix protein composed of p17 and an inner capsid made up of p24. The viral genome consists of two single stranded RNA molecules associated with two RT molecules as
well as other enzymes including a protease and an integrase.

Replication cycle and targets of therapy

The virus attaches to the CD4 molecule on Th cells, monocytes and dendritic cells through the gp120 of HIV. For HIV infection, a co-receptor is required. The co-receptor is a chemokine receptor such as CXCR4 or CCR5. CCR5, expressed predominantly on macrophages, and CXCR4 on CD4+ T cells serve as coreceptors for HIV infection. After the fusion of HIV envelope and the host membrane, the nucleocapsid enters the cell. The RT synthesizes viral DNA which is transported to the nucleus where it integrates with the cell
DNA in the form of a provirus. The provirus can remain latent till the cell is activated when the provirus also undergoes transcription. Virions, consisting of the transcribed viral RNA and proteins, are produced. These bud out of the host cell membrane from where they acquire the envelope. Thus, therapeutic agents have been developed that target viral entry and fusion, as well as serve as RT, protease and integrates inhibitors. Highly active anti-retroviral therapy
is a cocktail of 3 or more such agents.

Immunological Changes

The virus replicates rapidly and within about two weeks the patient may develop fever. The viral load in the blood increases significantly and peaks in two months, after which there is a sudden decline because of the latent virus found in germinal centers of the lymph nodes. CTL develop very early whereas antibodies can be detected between 3 – 8 weeks. The CTL killing of
of Th cells around 4 – 8 weeks leads to a decrease in CD4+ T cells. When the CD4+ T cell count decreases below 200 per cubic mm, full blown AIDS develops.

Immunotherapy

There are several barriers to development of an effective HIV vaccine.

 Attenuated vaccine may induce the disease
 CD4+ T cells may be destroyed by the vaccine
 Antigenic variation of HIV
 Low immunogenicity of the virus by downregulation of MHC molecules
 Lack of animal models
 Lack of in vitro tests

The following reagents have been considered in developing vaccines:

 Immunization with deletion mutants to reduce pathogenicity
 Vaccination with recombinant proteins
 Gene encoding proteins introduced into virus vectors may be used for
vaccination
 Chemokines that compete for the co-receptors
 IL-2 to boost the Th cells.

Immunodeficiencies associated with aging

These include a progressive decrease in thymic cortex, hypo-cellularity of and reduction in the size of thymus, a decrease in suppressor cell function and hence an increase in auto-reactivity, a decrease in CD4 cells functions. By contrast B cells functions may be somewhat elevated.

Immunodeficiencies associated with malignancies and other diseases

B cell deficiencies have been noted in multiple myeloma, Waldenstrom’s macroglobulinemia, chronic lymphocytic leukemia and well differentiated lymphomas. Hodgkin’s disease and advanced solid tumors are associated with impaired T-cell functions. Most chemotherapeutic agents used for treatment of malignancies are also immunosuppressive.

Other conditions in which secondary immunodeficiencies occur are sickle cell anemia, diabetes mellitus, protein calorie malnutrition, burns, alcoholic cirrhosis, rheumatoid arthritis, renal malfunction, etc.

PRIMARY IMMUNODEFICIENCIES

Primary immunodeficiencies are inherited defects of the immune system (figure 1). These defects may be in the specific or non-specific immune mechanisms. They are classified on the basis of the site of lesion in the developmental or differentiation pathway of the immune system. Individuals with immunodeficiencies are susceptible to a variety of infections and the
type of infection depends on the nature of immunodeficiency (Table 1).

SPECIFIC IMMUNE SYSTEM

There are a variety of immunodeficiencies which result from defects in stem cell differentiation and may involve T-cells, B-cells, and/or immunoglobulins of different classes and subclasses (Table 2).

A defect in the early hematopoiesis which involves stem cells results in reticular dysgenesis that leads to general immune defects and subsequent susceptibility to infections. This condition is often fatal but very rare.

Lymphoid lineage immunodeficiency

If the lymphoid progenitor cells are defective, then both the T and B cell lineages are affected and result in the severe combined immunodeficiency (SCID). Infants suffer from recurrent infections especially by opportunistic micro-organisms (bacterial, viral, mycotic and protozoan infections).

In about 50% of SCID patients, the immunodeficiency is x-linked whereas in the other half the deficiency is autosomal. Both are characterized by an absence of T cell and B cell immunity and absence (or very low numbers) of circulating T and B lymphocytes. Thymic shadows are absent on X-rays.

The x-linked severe SCID is due to a defect in the gamma-chain of IL-2 also shared by IL-4,-7, -11 and 15, all of which are involved in lymphocyte proliferation and/or differentiation. The autosomal SCIDs arise primarily from defects in adenosine deaminase (ADA) or purine nucleoside phosphorylase (PNP) genes which results is accumulation of dATP or dGTP, respectively, and cause toxicity to lymphoid stem cells. Other genetic defects leading to
SCID include those for RAG1, RAG2 and IL-7-alpha. If suspected of SCID, the patient must not receive live vaccine, as it will result in progressing disease.

Diagnosis is based on enumeration of T and B cells and immunoglobulin measurement. Severe combined immunodeficiency can be treated with a bone marrow transplant (see MHC and transplantation). Recently, autosomal SCID patients with ADA deficiency have been treated with a retroviral vector transfected with the gene with some success.

SCID includes several disorders


Patients having both T and B cell deficiency lack recombinase activating genes (RAG1 and 2) that are responsible for the T cell receptor and Ig gene rearrangements. These patients are athymic and are diagnosed by examining the T cell receptor (TCR) gene rearrangement. Defects in B cells are not observed in early infant life because of passive antibodies obtained from the mother. NK cells are normal.

In some SCID patients, T cells may be present but functionally defective because of deficiency in signaling mediated by the CD3 chain that is associated with the TCR.

Interleukin-2 receptor common gamma chain (IL-2Rγc) may be lacking in patients there by preventing signaling by IL-2, 4, 7, 9 and 15. These patients are T and NK cell deficient.

Adenosine deaminase (ADA) is responsible for converting adenosine to inosine. ADA deficiency leads to accumulation of adenosine which interferes with DNA synthesis. The patients have defects in T, B and NK cells.

Disorders of T cells

DiGeorge’s Syndrome (Deletion 22 Syndrome)

This the most clearly defined T-cell immunodeficiency and is also known as congenital thymic aplasia/hypoplasia, or immunodeficiency with hypoparathyroidism. The syndrome is associated with hypoparathyroidism, congenital heart disease, low set notched ears and fish shaped mouth. These defects results from abnormal development of the fetus during the 6th to 10th week of gestation when parathyroid, thymus, lips, ears and aortic arch are being formed. No genetic predisposition is clear and not all DiGeorge syndrome babies have thymic aplasia. A thymic graft taken from an early fetus (13 – 14 weeks of gestation) can be used for treatment. Older grafts may result in GVH reaction. In severely immunodeficient DiGeorge patients, live vaccines may cause progressive infections.

DiGeorge syndrome is autosomal dominant (figure 2) and is caused by a deletion in chromosome 22 (figure 3). The deletions are of variable size but size does not correlate with severity of disease. In about 6% of cases, the chromosome 22 micro-deletion is inherited but most cases result from de novo deletion which may be caused by environmental factors.

T cell deficiencies with variable degrees of B cell deficiency

Ataxia-telangiectasia

Ataxia-telangiectasia is a deficiency of T cells associated with a lack of coordination of movement (ataxis) and dilation of small blood vessels of the facial area (telangiectasis). T- cells and their functions are reduced to various degrees. B cell numbers and IgM concentrations are normal to low. IgG is often reduced and IgA is considerably reduced (in 70% of the cases). There is a high incidence of malignancy, particularly leukemias, in these patients. The defects arise from a breakage in chromosome 14 at the site of TCR and Ig heavy
chain genes.

Wiskott-Aldrich syndrome

This syndrome is associated with normal T cell numbers with reduced functions, which get progressively worse. IgM concentrations are reduced but IgG levels are normal. Both IgA and IgE levels are elevated. Boys with this syndrome develop severe eczema, petechia (due to platelet defect and thrombocytopenia). They respond poorly to polysaccharide antigens and
are prone to pyogenic infection. Wiskott-Aldrich syndrome is an X-linked disorder (figure 4) due to defect in a cytoskeletal glycoprotein, CD43.

MHC deficiency (Bare leukocyte syndrome)

A number of cases of immunodeficiency have been described in which there is a defect in the MHC class II transactivator (CIITA) protein gene, which results in a lack of class-II MHC molecule on their APC. Since the positive selection of CD4 cells in the thymus depends on the presence of these MHC molecules, these patients have fewer CD4 cells and are infection prone. There are also individuals who have a defect in their transport associated protein (TAP) gene and hence do not express the class-I MHC molecules and consequently are deficient in CD8+ T cells.

Disorders of B lymphocytes

There are a number of diseases in which T cell numbers and functions are normal: B cell numbers may be low or normal but immunoglobulin levels are low. These are briefly summarized below.

X-linked infantile hypogammaglobulinemia

X-linked hypogammaglobulinemia, also referred to as Bruton’s hypoglobulinemia or agammaglobulinemia, is the most severe hypogammaglobulinemia in which B cell numbers and all immunoglobulin levels are very low. The patients have failure of B-cell maturation associated with a defective B cell tyrosine kinase (btk) gene. Diagnosis is based on
enumeration of B cells and immunoglobulin measurement.

Transient hypogammaglobulinemia

Children, at birth, have IgG levels comparable to that of the mother. Because the half life of IgG is about 30 days, its level gradually declines, but by three months of age normal infants begin to synthesize their own IgG. In some infants, however, IgG synthesis may not begin until they are 2 to 3 years old. This delay has been attributed to poor T cell help. This results in a transient deficiency of IgG which can be treated with gamma-globulin.

Common variable hypogammaglobulinemia (Late onset hypogammaglobulinemia)

These individuals have acquired deficiencies of IgG and IgA in the 2nd or 3rd decade of their life and are susceptible to a variety of pyogenic bacteria and intestinal protozoa. They should be treated with specially prepared gamma-globulin for intravenous use.

IgA deficiency

IgA deficiency is the commonest of all immunodeficiencies (1/700 of all Caucasians). About 20% of individuals with IgA deficiency also have low IgG. IgA-deficient patients are very susceptible to gastrointestinal, eye and nasopharyngeal infections. Patients with IgA deficiency have a high incidence of autoimmune diseases (particularly immune complex type) and lymphoid malignancies. Anti-IgA antibodies (IgG) are detected in 30 to 40 percent
of patients who should not be treated with γ-globulins. Laboratory diagnosis is based on IgA measurement.

Selective IgG deficiency

Deficiencies of different IgG subclasses have been found. These patients are susceptible to pyogenic infections.

Hyper-IgM immunodeficiency

Individuals with this type of immunodeficiency have low IgA and IgG concentrations with abnormally high levels of IgM. These patients cannot make a switch from IgM to other classes which is attributed to a defect in CD40L on their CD4 cells. They are very susceptible to pyogenic infection and should be treated with intravenous gamma-globulins.

NON-SPECIFIC IMMUNE SYSTEM

Primary immunodeficiencies of the non-specific immune system include defects in phagocytic and NK cells and the complement system.

Defects of the phagocytic system

Defects of phagocytic cells (numbers and/or functions) can lead to increased susceptibility to a variety of infections.

Cyclicneutropenia

This is marked by low numbers of circulating neutrophil approximately every three weeks. The neutropenia lasts about a week during which the patients are susceptible to infection. The defect appears to be due to poor regulation of neutrophil production.

Chronic granulomatous disease(CGD)

CGD is characterized by marked lymphadenopathy, hepato- splenomegaly and chronic draining lymph nodes. Leukocytes have poor intracellular killing (figure 5) and low respiratory burst. In majority of these patients, the deficiency is due to a defect in NADPH oxidase (cytochrome b558 : gp91phox, or rarely gp22phox) or other cofactor proteins (gp47phox, gp67phox) that participate in phagocytic respiratory burst. These patients can be diagnosed on the basis or poor Nitroblue tetrazolium (NBT) reduction which is a measure of respiratory burst. Interferon-gamma therapy has been successful.

Leukocyte Adhesion Deficiency

In this disease, leukocytes lack the complement receptor CR3 due to a defect in
CD11 or CD18 peptides and consequently they cannot respond to C3b opsonin.
Alternatively there may a defect in integrin molecules, LFA-1 or mac-1 arising
from defective CD11a or CD11b peptides, respectively. These molecules are involved in diapedesis and hence defective neutrophils cannot respond effectively to chemotactic signals.

Chediak-Higashi syndrome

Chediak-Higashi syndrome is marked by reduced (slower rate) intracellular killing and chemotactic movement accompanied by inability of phagosome and lysosome fusion and proteinase deficiency. Giant lysosomes (intracellular granules) are often seen (figure 6). The respiratory burst is normal. Accompanying NK cell defects and platelet and neurological disorders are noted.

DISORDERS OF COMPLEMENT SYSTEM

Complement abnormalities also lead to increased susceptibility to infections. There are genetic deficiencies of various components of complement system, which lead to increased infections. The most serious among these is the C3 deficiency which may arise from low C3 synthesis or deficiency in factor I or factor H.

How To Write A Scientific Biology Paper

Let’s try to figure out what essential features that biology essay contains.

First, this type of Biology essay is devoted to one particular problem or question, so the author’s position is not comprehensive. But often, one problem leads to the disclosure of many secondary issues, and the student should try not to “drown” in them but stick to a specific main position.

Second, the essay is a rather subjective genre. And this is its value. After all, the teacher expects from the essay writing a personal assessment of the specific biological topic, uniqueness, expression of an individual position, style of thinking and speech, free orientation in social science terms, and social events.

Thirdly, an essay requires ease of narration; that is, freedom in presenting one’s thoughts should be felt. The use of any formal settings can make a mini-essay “dry,” “stale,” and “non-scientific,” while the content should be captivating, sometimes even contradicting standard principles, and in this case, you can use any paper helper you need.

Fourth, essays on science topics should be peculiar in order to excite the reader, to give an opportunity to re-evaluate known facts, to challenge the truth, citing paradoxical definitions as proof.

Fifth, despite the paradoxical facts, the content must have inner harmony and consistency with the author’s personal judgments.

Sixth, the essay has such a trait as openness. Of course, as in any essay
or article, at the end of the essay, it is necessary to draw a conclusion so that any other author could continue to think about the issue disclosed, giving an analysis or supplementing
arguments.

The merits of the biology essay should include:

  • Availability of brief information about the author of the statement that became the topic of the essay (political figure, economist, philosopher, public figure);
  • Inclusion of his predecessors, followers, and opponents; – description of different points of view on the problem;
  • Multiple meanings of used concepts and terms in the context of the content;
  • Giving alternative solutions to the problem.

Criteria for evaluating essays

Before starting to write a biological essay, a student should be familiarized with the requirements for this type of task. More often than not, you can turn to practice assignments.

Scores for the essay are given in accordance with such criteria as the meaning of the statement is disclosed, your own position is presented with argumentation, and judgments and arguments are revealed with the support of theoretical provisions, conclusions and facts. But these criteria do not give students specificity. It should be remembered that the essay, as a specific type of task, requires students to express their skills and abilities.

Writing an essay starts with choosing a topic. The topics of the proposed problems are divided into categories: philosophy, sociology, economics, social
psychology, political science, and law. To prepare for writing an essay on biology, it is best for students to decide on two or three areas in which they are more successfully oriented, appealing to concepts and facts. Sometimes students choose a particular area of this science that they like to discuss topical issues on their own.

However, based on the experience of preparing for the essay, the student should try their hand in all directions, then the priority ones will be presented most clearly, and the student will put the emphasis already on them. Choosing
an essay topic is a complicated task. Pupils should be sure that they understand the chosen statement correctly, that they have sufficient social science concepts, and that they will be able to cite convincing facts and examples from history, social life, and their own experience.

Next, it is necessary to define the problem reflected in the statement, its relevance, and its scientific importance. Most often, the statement itself already contains a clue to the problem. In the first stages of preparation for writing an essay, it is necessary to pay attention of students to those terms that are used in the task. It is these concepts that need to be disclosed in the content of
the essay, and it is from these concepts that the argument is explored.

To build the logic of the presentation of the contents of the essay, students are helped by drawing up a plan or a kind of draft. The students have an opportunity to choose the sequence of arguments, facts, and examples, and this is where the unconventionality of the essay will come into play.

The three main positions of the structure



In my opinion, there are three main positions of the structure that should still be taken into account: the introduction, the main part, and the conclusion. This will make the work of the students much easier.

The introduction shows just how much the student understood the problem and reflected its relevance. Also, in the introduction, it is necessary to specify also own position on the submitted problem and to define the further directions of research.

The main part of the essay is a detailed study of the problem with its proof or refutation. This part of the essay structure is more voluminous and informative. Here the authors give their theses, determining the truth or falsity of the statement. The theses should be diluted with facts, phenomena of reality, and scientific evidence.

Facts should be interconnected, and it should be remembered that any fact has its validity only in a particular historical time. It is in this part that the definitions of concepts are revealed through the essential features of the subjects. Besides, the free use of social science concepts in the context of the content shows how complete the author’s knowledge is.

It is important that the concepts used are clear, correct, and generally accepted. A huge plus in writing an essay is giving examples. If the author has difficulty in this regard, you can use examples from your own life and accumulated experience. It should be borne in mind that examples must clearly relate to the analyzed problem.

The use of examples shows the free orientation of students in the social space and the ability to correctly assess events, processes, the actions of individuals.

The final part of the essay may contain brief conclusions of students on the topic, reflecting their own point of view, which is prospective in nature. Also, in conclusion, the author can offer his original solution to the problem.

The essay will become more interesting if the conclusions are bright, emotional, and unpredictable, with unusual twists. This will allow further reasoning on the analyzed problem (Man is only a part of a huge world, a world that is entangled in a thick web of mysteries and riddles. Will there be a spider to unravel it? Man…? What is it…? Who is it?…). Thus, the best way to write an essay is to do it sequentially.