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Ap Biology Hardy Weinberg Essay About Myself

Are you shooting for a score of 4 or 5 on the AP Biology exam? If you’re taking the class, you’re probably nodding your head right now or shouting “yes!” After all, who doesn’t want free college credit, the experience and challenge of taking a college-level biology course, and a great looking high school transcript? The first thing you need to know, however, is that the AP Bio exam will be a challenge for you, no matter what kind of experience you have.

It’s helpful to look at past AP score distributions to show you the level of difficulty of the exam. On the 2014 AP Biology exam, only 6.5% of all test takers earned the coveted score of 5. (Fun fact: 3 students out of 214,000 got a perfect score!). That may sound intimidating, but it’s not all bad since 22.2% earned a 4 and 35.1% earned a 3, meaning 63.8% of all test takers passed the 2014 exam. Only 36.2% did not receive a passing score, with 27.4% earning a 2, and 8.8% earning a score of 1. This means that more than half of students passed the exam, which should boost your confidence and show you that it’s definitely doable. However, the test is by no means easy. In fact, it’s one of the hardest AP exams out there. Sure, you need to memorize facts and concepts, but you also have to be able to think scientifically and analytically, which is much easier said than done.

Luckily, this list of 50 AP Bio tips is here to give you the best chance of getting that 5. Whether you’re taking this class in school or self-studying, these tips will tell you everything you need to know, from how to study, what to study, what the exam consists of, and everything in between. Let’s get started!

How to Study for AP Biology Tips

1. Familiarize yourself with the format of the exam. The first step in getting ready to study for the AP Biology exam is knowing what the exam will look like. The exam is 3 hours long and consists of two sections. The first 90-minute section has two parts: a multiple-choice part with 63 questions and a grid-in part with 6 questions. Section I makes up 50% of your overall exam score. Section II, also making up 50% of your exam score, consists of 8 free-response questions. You’ll have 90 minutes to answer two long free-response questions, one of which will be lab or data-based, and six short free-response questions, which each require a paragraph-length argument or response.

2. Get your vocabulary down first! Vocabulary is extremely important in AP Bio, but understanding concepts and making connections is even more important. Why, then, do you have to focus on vocab first? It just makes sense. When you think about it, concepts are useless if you don’t understand key terms. “This thing does this to that and this process works by doing that.” It just doesn’t work. Make and use flashcards regularly, learn the Greek and Latin prefixes, suffixes, and roots, and take great notes. When you know vocabulary terms inside and out, it is much easier to think analytically, apply terms to different situations, and make important connections. Quizlet’s Ultimate AP Biology Vocabulary review flashcards has a great list of all the vocab terms you need to know, complete with definitions and helpful diagrams and images.

3. Know what is NOT included on the exam. There are a number of concepts, facts, terms, and ideas that are beyond the scope of the AP Biology exam. You do NOT have to know:

•Names, molecular structures, and specific effects of plant hormones

•Details of fossil dating methods

• Names and dates of extinction events

• Steps in the Calvin cycle, the structure of the molecules and the names of enzymes (EXCEPT for ATP synthase)

• Steps in glycolysis and the Krebs cycle

• Names of the specific electron carriers in the ETC

• Names of specific stages of embryonic development

•  Genetic code

• Names and phases of mitosis

• Epistasis and pleiotropy

• Details of sexual reproduction cycles in plants and animals

•  Specific mechanisms of diseases and action of drugs

•  Details of communications and community behavioral systems

•  Types of nervous systems, development of the human nervous system, details of the various structures and features of the brain parts, and details of specific neurologic processes

• Molecular structure of specific nucleotides, chlorophyll, amino acids, lipids, and carbohydrate polymers

• Functions of smooth ER in specialized cells

•Specific examples of how lysosomes carry out intracellular digestion

•  Specific symbiotic interactions

Source: CollegeBoard AP Biology Exam and Course Description

4. Make flashcards with diagrams. Diagrams are important in AP Bio. You’ll have to interpret many of them on the exam. That’s why it’s really beneficial to draw your own diagrams on your flashcards. Use different colors, label the important parts, and list the steps. Whether it’s the Krebs cycle or the nitrogen cycle, find a way to make it stick in your brain.

5. Don’t lose track of the big picture. As you’re studying for the exam, you’ll probably find yourself getting hung up on little details. AP Bio has a way of throwing a lot of facts, specific names, dates, and functions at you. It would be impossible to memorize everything! That’s why it’s essential to remember why you’re reading a certain chapter, what that chapter contributes to the bigger picture, and how all these concepts you’re reading about connect together. Don’t overwhelm yourself with trying to know absolutely everything about everything.

6. Keep on top of the readings. Did you know that AP Bio is one of the most reading-intensive AP classes that the CollegeBoard offers? Your teacher will probably require you to read one or two chapters per night, which means you’ll probably have to tackle 30 to 60 pages of AP Bio material each evening. That’s why you absolutely must keep on top of it since even if you miss one night of reading, you’ll fall behind very quickly. Don’t just passively read the information, either. You have to actively read and make sure you’re actually absorbing the material as you go. Try reading the chapter summary first, highlight important info, take meaningful notes, and explain a concept to yourself out loud if you seem to be struggling with it.

7. Know the 4 Big Ideas. The CollegeBoard divides the AP Biology curriculum into 4 Big Ideas. This means that all the key concepts and content you need to know for the exam are organized around four main principles:

Big Idea 1: The process of evolution drives the diversity and unity of life.

Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis.

Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes.

Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties.

To find out more about the 4 Big Ideas and the information you need to know for each, check out the AP Biology Curriculum Framework.

8. Invest in a review book. AP Biology textbooks are heavy, thick, and full of details that are sometimes beyond the scope of the exam. How do you know, then, which information you actually need to know? Buy a review book! Many of them come with practice exams, chapter reviews, and helpful hints. It’s important to only buy a review book that has been published in 2013 or later, since the exam was completely redesigned in 2013. Check out our Best AP Biology Review Books of 2015 to find out which review book is best for you.

9. Watch the Crash Course Biology series on YouTube. Sometimes, reading textbooks and review books can get tiring. When you find yourself bored and unmotivated, try watching biology videos. The Biology Crash Course on YouTube has 40 videos dedicated to teaching you all the most important biology concepts. Injected with humor, fast-paced, and entertaining, these videos make it feel like you’re not actually studying at all. Still, make sure to actively watch, take notes, pause if you don’t understand something, or make a flashcard for a new term you hear about.

10. Participate in the “Dirty Dozen” labs. Odds are, you’ll be able to participate in these 12 important labs in class. If not, you should research them for yourself. Bozeman Science has videos on all 12 labs, walking you through the steps of each. The LabBench is also a great resource for understanding the key concepts and technical terms behind the 12 labs, along with self-quizzes to make sure you understand the material.

Start your AP Biology prep today

AP Biology Multiple-Choice Review Tips

1. Know what the multiple-choice questions look like. The multiple-choice questions on the AP Bio exam are probably different to other AP exams you’ve taken. They involve a lot of reading and analyzing diagrams, data, and images. They aren’t just simple “What do plants release during photosynthesis?” fact-recall type questions. You’ll have to read a paragraph for each question, or interpret a graph or diagram, and use your knowledge of biological concepts to choose the best answer. Let’s look at a few examples:

Example #1.

By discharging electric sparks into a laboratory chamber atmosphere that consisted of water vapor, hydrogen gas, methane, and ammonia, Stanley Miller obtained data that showed that a number of organic molecules, including many amino acids, could be synthesized. Miller was attempting to model early Earth conditions as understood in the 1950’s. The results of Miller’s experiments best support which of the following hypotheses?

A. The molecules essential to life today did not exist at the time Earth was first formed.

B. The molecules essential to life today could not have been carried to the primordial Earth by a comet or meteorite.

C. The molecules essential to life today could have formed under early Earth conditions.

D. The molecules essential to life today were initially self- replicating proteins that were synthesized approximately four billion years ago.

Answer: C.

Example #2.

When DNA replicates, each strand of the original DNA molecule is used as a template for the synthesis of a second, complementary strand. Which of the following figures most accurately illustrates enzyme-mediated synthesis of new DNA at a replication fork?

Answer: D.

As you can see from these two example questions, there is more to think about than just simply recalling facts. Often, several questions will be based on the same data sets and diagrams. For more questions like these, check out Albert.io.

2. Find and read the question first. Lab-set questions and diagram questions can be tedious since you’ll have to do so much reading and analyzing. Skip the diagram or any long paragraph at first, find the question they’re asking you, and then go back to the data to find the answer to that question. It’s a simple technique, but when you have 63 long multiple-choice questions to read, analyze, and answer in such a short time, pinpointing the actual question first can be helpful.

3. Use standard multiple-choice strategies. Using multiple-choice techniques, such as process of elimination, making educated guesses, and budgeting your time are important for any multiple-choice test. Let’s look at how these apply to the AP Bio exam. On the multiple-choice section, you will have four options, rather than five. This means that if you can eliminate two choices, you have a 50% chance of getting the answer correct. When it comes to budgeting your time, it’s important to remember that you have about 45 seconds to 1 min for each multiple-choice question. Try and stick to that time limit for each question, otherwise you may run out of time and have to leave some questions unanswered. You should also watch out for reverse questions, such as “EXCEPT,” since all the data and information they’re throwing at you can be distracting and you may miss important keywords.

4. Practice! The only way to get better at answering complicated AP Bio multiple-choice questions is to practice as much as possible. Practicing gets you familiar with the format of the questions and gives you some much-needed confidence. You can find practice questions online, in review books, and in the CollegeBoard’s AP Biology Course and Exam Description. Make sure you’re practicing questions from 2013 and later, because exams before that follow the old, fact-recalling multiple-choice format and won’t help you for future AP Bio exams.

AP Biology Grid-In Response Tips

1. Know these quick tips:

•  Your answer can start in any column

•  Extra columns should be left blank

•  Units are not required

•  Fill in only one bubble per column

•  Use decimals and other symbols if necessary

•  The grid is machine-scored so fill in the bubbles correctly

•  Mixed numbers need to be gridded as a decimal or improper fraction

2. Pay attention to the instructions. The directions will specify how to round your answers and whether or not your fractions should be reduced. Pay close attention to these instructions because even if your answer is correct, you won’t get any points if it’s not in the proper form and not bubbled in correctly.

3. Don’t memorize formulas. For the AP Bio exam, there is no need to memorize formulas since you will be given a formula list to use during the exam. Look over this list to see what kinds of formulas you need to be practicing. It’s important to remember, though, that while you don’t have to memorize formulas, you still need to be familiar with them.

4. Know how to apply mathematical formulas. The most important thing you need to know for the grid-in questions is how to apply a formula to reach the correct answer. You need to know how to work with Chi Squares, surface area and volume, water potential, Hardy-Weinberg, probability, and standard deviation. This comprehensive AP Biology Math Review has everything you need to know math-wise for the grid-in section of the exam. Remember that you are allowed to use a basic four-function calculator (with square root), but NOT a graphing calculator, on the exam.

Start your AP Biology prep today

AP Biology Free Response Tips

1. Know the FRQ format. At the start of the AP Bio free-response section of the exam, you will be given a 10-minute reading and planning period. After that, you’ll have 80 minutes to answer 8 essay questions, broken down like this:

Long Free-Response

Short Free-Response

How many?


How much time?

20 minutes for each6 minutes for each

How much value?

10-point scale for each 25% of final exam score10-point scale for each 25% of final exam score


2. Use the entire 10-minute reading period. Don’t underestimate the importance of the planning period! It’s given to you for a reason. You should read through all 8 of the questions, re-read them, and use the “planning space” to start putting your thoughts on paper. Draw diagrams, underline keywords, make notes, outline your responses, or whatever else you need to do to start formulating your answers. Ten minutes will feel like a long time, but use the entire time. Make sure you really know what the question is asking you; take the time to fully digest the question.

3. Define your terms. Never write down a biological term without defining it. For example, you probably won’t get the point if you just write osmosis, without mentioning “movement of water down a gradient across a semipermeable membrane.” Always incorporate a definition of some shape or form to show the AP readers that you know what you’re talking about. In other words, don’t just inject fancy vocab words into your essays if you don’t know what they mean; the AP readers will know.

4. Connect biological concepts to larger big ideas. Your main focus in studying for the AP Biology exam should be making connections. Knowing your vocabulary and labs is not useful if you can’t connect them to larger big ideas. On the FRQs, you’ll have to make claims and defend them, providing evidence to support your reasoning. How can you do this, while still making insightful connections across big ideas? The CollegeBoard has a few suggestions:


Example Question

Relate a proposed cause to a particular biological effect.What is the evidence that a single mutation caused the phenotypic change seen in an organism?
Identify assumptions and limitations of a conclusionIf a nutrient has a positive effect on one plant, can you appropriately conclude that it is effective on all plants?
Connect technique/strategy with its stated purpose/function in an investigationIdentify the control from a list of experimental treatments.
Identify patterns or relationships (and anomalies) from observations or a data setIs the behavior of an organism the same in different environments?
Rationalize one choice over another, including selection and exclusionWhich question from this list of questions can best be investigated scientifically?

5. Be aware of the free-response booklet instructions. It’s helpful to know the actual AP Bio FRQ exam instructions:

•  Each answer should be written out in paragraph form; outline form is not acceptable.

•  Do not restate questions or provide more than the number of examples called for.

•  Diagrams alone will not receive credit, unless called for in the question.

•  Write clearly and legibly.

•  Begin each answer on a new page.

•  Do not skip lines.

•  Cross out any errors you make.

6. Know the types of questions. The table below outlines some of the most common free-response question types, how to answer them, and real example questions from past AP Bio exams.

*Click on the links included in the example questions to see sample responses.

Question Type

What To Do

Example Question

Predict and Justify/Predict andState what you think will happen in a certain circumstance and prove this reasoning using examples.Predict the effects of the mutation on the structure and function of the resulting protein in species IV. Justify your prediction. (2014 AP Bio exam)
ProposeCome up with an improvement, solution, or idea that answers the prompt. Be specific.Propose an evolutionary mechanism that explains the change in average number of spots between 6 and 20 months in the presence of the predator. (2014 AP Bio exam)
IdentifyName one or more items, list the parts, and give an example.Identify TWO environmental factors that can change the rate of an enzyme-mediated reaction. (2010 AP Bio exam)
ExplainMake something understandable. Give reasons and examples, instead of just descriptions.Explain how paper chromatography can be used to separate pigments based on their chemical and physical properties. (2010 AP Bio exam)
Compare/ContrastPoint out what is similar and what is different between two or more concepts. Do not explain or describe the objects separately.Compare and contrast reproduction in nonvascular plants with that in flowering plants. (2009 AP Bio Exam)
DiscussThink of this question as an “all of the above” type question. You need to consider different theories, points of view, and ideas, implementing the identify, describe, and explain strategies.Discuss THREE ways that an invasive species can affect its new ecosystem. (2011 AP Bio Exam)
DescribeProvide the characteristics/properties of a term or concept.Describe THREE different factors that contribute to the success of invasive species in an ecosystem. (2011 AP Bio Exam)

Many times, a single free-response question on the AP Bio exam will include several of these key terms, while some only include one key term. Pay attention to exactly what the question is asking you to do and be sure to answer every part. An example of a question that asks you to do several things in one would look like this:

“Based on the data in the table below, draw a phylogenetic tree that reflects the evolutionary relationships of the organisms based on the differences in their cytochrome c amino-acid sequences and explain the relationships of the organisms. Based on the data, identify which organism is most closely related to the chicken and explain your choice.”

7. Claim + Evidence + Reasoning. This model of scientific argumentation can be helpful to keep in mind when writing your FRQs. Essentially, you have to read and understand the question you’re being asked, directly answer this question with a claim statement, back up your claim with detailed examples of evidence, then use reasoning to explain how this evidence justifies your claim. Just remember claim, evidence, reasoning when you’re writing your essays.

8. Answer the parts of the question in the order called for. Try not to skip around too much when answering your FRQs. If you do, you might accidentally miss a part of a question. Instead, use the question’s labels (a, b, c, d, etc.) to stay organized and clear. Make it as easy as possible for the AP readers to follow your answer.

9. Know how to answer “Design an Experiment” questions. Sometimes, you’ll be asked to design an experiment as part of your FRQ. This is where your knowledge of the “Dirty Dozen” labs comes in. You need to be familiar with lab procedures and terms. In your response, make sure to include:

•  Hypothesis (using the “if…then” structure)

•  Independent and dependent variables

•  Control, stating directly, “Controls are…”

•  Explanation of the data you will collect and how you will measure it

•  Materials list

•  Procedure list (what you will actually do)

•  Description of how the data will be graphed and analyzed

•  Conclusion (what you expect to happen and why, compare your results to your hypothesis)

Remember that your experiment should be at least theoretically possible and that your conclusions should stay consistent with the way you set up your experiment.

10. Know how to answer “Draw a Graph” questions. If you’re asked to draw a graph based on data, be sure to include the following in your response:

•  Labeled x-axis (independent variable) and y-axis (dependent variable)

•  Equal and proportional increments

•  Name and units

•  Smooth curve

•  Appropriate title

•  If more than one curve is plotted, label on each curve instead of using a legend

Hint: Most of the points for a graphing question come from proper setup!

11. Be specific and thorough. Avoid flowery and vague language in your essays. You don’t want to say something like: “Many parts of a cell are important in cell respiration.” This sentence is way too general and doesn’t really say anything at all. Whenever you use a biology term in your essay, offer specific examples of that term. Remember that your goal is to convince an AP reader that you know what you’re talking about.

12. Manage your time. It can be easy to get carried away when writing your FRQs. Just remember that you have to write 8 essays in only 80 minutes. You need to spend more time on the two long free-response questions than on the six short free-response questions. You should be spending 20 minutes on each long FRQ and only 6 minutes for each short FRQ. Use a watch and time yourself during the exam. You don’t want to end up with no time to answer a question and miss out on 10 points.

Tips by AP Biology Teachers

1. Look for “real life” examples of what you’re learning. Go to websites like Biology News, Science Daily, and The Chemical Heritage Foundation. Search for articles in the subject you’re learning. The more ways you learn something the better!

2. Watch Bozeman Biology videos. Mr. Anderson, the teacher behind Bozeman Biology, has a wide variety of videos for AP Bio. Watch them before you start a unit to get a general idea of what you’ll be learning and before tests so you can review. Thanks to Ms. Lorie X. from Riverdale High for the tips!

3. Underline important terms in the question. Such as: “OR” and “CHOOSE TWO” and the power verbs such as: ‘DESCRIBE,’ ‘IDENTIFY,’ ‘LABEL,’ ‘CONSTRUCT,’ ‘DESIGN,’ or ‘EXPLAIN.’

4. Find the core biology topic. Even if you don’t understand the question or you draw a blank, find the ‘core biology topic’ being asked about and elaborate on it. Thanks to Mrs. S. from North High School for the tips!

5. Write! Write! Write! For the free-response questions, usually, the longer your answer to the question, the more points you will earn! That being said, don’t just do a mind dump.

6. Apply the language of science. FRQs require that you show depth, elaboration, and give examples. You need to loop together your ideas and show how they connect. Don’t just rely on factual regurgitation. Thanks to Mr. Jeremy M. from Blue Valley Northwest High School for the tips!

7. Know how to set up your essays. When you’re planning your essays, follow this structure:

1. Introductory sentence

2. Several broad points

3. Examples to prove your points

4. Closing sentence to summarize

Fill in this general structure with details and specifics. Write in short, declarative sentences. Thanks to Mr. C. from Alliance Cindy & Bill Simon Technology Academy High School for the tip!

8. Answer the question as concisely as possible. Avoid writing down everything you know about a certain topic. If you do, you might contradict yourself or write down something which is wrong. You can be penalized for this. Thanks to Mr. F. from Dauphin Regional Comprehensive Secondary School for the tip!

9. Remember that the AP graders are looking for certain statements to award points. If a FRQ asks you describe mutualism, for example, you need to both define it and elaborate on it to receive full points. As a general rule, always support your definitions with at least one example. Thanks to Dr. L. from Framingham High School for the tip!

10. Answer something for every question. If you don’t know how to answer a free-response question, don’t panic. Begin with defining some terms related to the topic. Elaborate with an example or more detailed explanation of the things you can remember. Thanks to Ms. Kelly O. from Colleyville Heritage High School for the tip!

11. No detail is too small as long as it is to the point and on topic. For example, if a question asks about the structure of DNA, talk about the helix, the bases, the hydrogen bonds, introns, exons, etc. Do not waste time talking about RNA, expression, Mendelian genetics, etc. Thanks to Ms. Louise H. from Friedrich Von Steuben Metropolitan Science Center for the tip!

Tips from Past AP Biology Students

1. Do lots of genetics practice problems. Practice working with Hardy-Weinberg formulas, Punnett Squares, and Chi-Square tests. Also, memorize the common crosses, like dihybrid monocross.

2. For test prep, use the released exams! I worked through all the available FRQs on the CollegeBoard website, and my teacher provided multiple-choice practice from the last two years. Those went a long way in helping me figure out the type of questions they ask, the common material they test, and how to manage my time. I would also recommend checking out the student answers to released FRQs, as well as the FRQ answer keys to get an idea of what kind and how much information are needed to get the points.

3. It helps to memorize things. AP Bio is less memorization than it used to be, but it still helps to memorize things. You should still be able to recall things at the drop of a hat, but you don’t need to know all 12 of the reactions involved in glycolysis like you once did.

4. The human body is important. It’s important to know your anatomy and human body systems. Focus on the nervous, immune, and endocrine systems. Don’t just memorize the parts, but understand the processes. For example, know how an antibody attacking postsynaptic receptors leads to certain responses.

5. When in doubt, focus on these topics:

•  Evolution (as a whole)

•  Genetics/genetic regulation (transcription, translation, etc.)

• Population ecology

•  Animal function/physiology

• Muscular System

•  Nervous System

• Endocrine System

• Immune System

6. Understand the concepts, functions, processes and relationships between subjects. The AP Bio test isn’t simply just recalling facts anymore. You need to analyze information rather than just recall information from your studies.

7. Make sure you know all about DNA/RNA (transcription/translation), cellular respiration/photosynthesis, and evolution. Make sure you have a great detailed and conceptual understanding of these topics!

8. Know the “how” and “why” of a topic. If you can’t explain how something works, knowing it is pointless. Stop and quiz yourself about something you just learned. How does that process work? If you can’t explain it in your own words, you need a better understanding of it.

9. Know all about anatomy/physiology. This includes both humans and plants. Know the basics of plant transport systems and focus on the nervous and endocrine systems.

10. Make study sheets or chapter outlines. Making study sheets requires more active work than flashcards, which helps the information stick in your head. It also refreshes your memory on the definitions in context, which is important for AP Biology.

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To be honest, back when I was in college and even when I first started teaching Biology, whenever I hit the Hardy Weinberg questions, I thought big whoop who cares. It’s just a couple of equations that describe a population genetics. And they only work if things don’t change and how often does that happen? It wasn’t until a colleague of mine was getting all excited about teaching Hardy Weinberg, that I found that maybe it is a big warp and maybe I should care.

You see in science, whenever you’re studying something you always want a control group, to compare to your experimental group. And if you are studying something like human evolutions, it’s really hard to get funding, to build yourself a giant second earth. Put your control humans on, compared to this earth's humans. Instead, using some basic statistical math, you can just mathematically create a control group.

It’s kind of like if a friend of yours. If you think there is something funny going on with his coin, well you don’t need to sit there and flip it 100 times and then compare that Result to 50 other coins that you also flipped 100 times. Instead you could just say, well assuming there’s nothing weird with the way he’s flipping it, or weird with the weight or shape of the coin., it should be 50-50, it’s the same thing.

I assume if you’re watching this video, you’ve done some genetic problems. And you know just how useful Punnett squares for predicting the outcome, when you have two different organisms breeding. Well the Hardy Weinberg equations are essentially Punnett squares for an entire population.

Before I go much further we’re going to spend a little bit time defining the terms of the Hardy Weinberg equations and making sure you know what those mean. Next as a statistical tool, Hardy Weinberg is based on a few assumptions. And if it’s predictions don’t much reality, then it indicates that one or more of those assumptions have been broken. The last thing we’ll do is, we’ll go through a couple of the standard Hardy Weinberg equations problem sets that you’ll see on the actual on the actual AP exam.

I’ve already mentioned one of the basic concepts of Hardy Weinberg, which is a population. A population is a group of interbreeding organisms in a particular area. So what are some of the other terms? Well there is this other concept called a gene pool. You got to understand a gene pool is an abstract idea. You can’t go swimming it. What a gene pool is just the sum total of all of the genes in a population. Let’s take a look at an example.

In this population, we have six individuals. And we’re going to be looking at the tongue rolling gene, the ability to do this. That’s a dominant trait. So we can see here that we have two people who are homozygous dominant for the tongue rolling ability. Three individuals who are heterozygous, and then one individual in our population of six, who is homozygous recessive i.e. a non tongue-roller.

So how big is our gene pool? How many copies of this gene do we have? Well we know that every individual has two copies of every gene, that’s Mendel’s first law. So two times six is 12. So we have a gene pool of six genes here. So what’s the frequency of that big R within our gene pool? Let’s take a look.

So I could write big R is one, two and I do some math I count up. And I see seven out of my 12 possible alleles is the big R. I type that into my calculator and get roughly that’s equal to 0.58. In Hardy Weinberg terms they call that the frequency of the dominant allele. And they use the variable ‘p’ to represent whatever the dominant allele is.

What if I was trying to figure out the frequency of this recessive little r, or in Hardy Weinberg terms, ‘q’? Well I could sit there and I could count out the number of the little r’s divide that by twelve. Or I can rip up my incredible math skills and I can say, "Well I know p plus q that frequency of the recessive allele that’s a grand total of one."

So I just plug in my numbers 0.58+q= 1. Subtract 0.58 from both side and I get q equals 0.42. Not so tough. Now what if I was trying to, well what does this mean? It means that the chances of me randomly spinning around and pointing at somebody, and that person happens to have at least big R is 0.58. What’s the chance of that person having two big R’s? Well, if you remember from your math classes, I will just take the probability of it happening once and multiply by the probability of that happening again. Essentially 0.58 times 0.58 or more simply p.

Hey wait a minute, let’s take a look at that p+q=1 thing, again. So p+q=1 let’s see. if I square both sides of this equations I get p² plus 2pq plus q² and 1² is 1.So p² is the chances of somebody being homozygous dominant, well that makes sense. The chance of getting a p and p. q² is the frequency of the homozygous recessive individuals. And then that leaves 2pq to be those individuals who are heterozygous. So that makes sense, p times q, why 2. Well you could get the big R from your mommy and little r from daddy, or the other way around. So there’s two ways to get a dominant and recessive and trait. So that’s why we have that 2 there, and is not just because of the math, it's because it works and it represents reality.

Now I’ve been flinging a bunch of terms out there at you. So let’s take a quick look and make sure that everybody is on the same page with this.

So p is the frequency of the dominant allele in the gene pool. q is the frequency of the recessive allele in the gene pool. So these are describing the abstract concept of the gene pool. P² is the frequency of homozygous dominant people or organisms in the population. So here we’re talking about actual numbers of actual creatures. 2pq is the frequency of heterozygous individuals in the population. While q² is the frequency of homozygous recessive individuals.

So that is basically how Hardy Weinberg works. Now we say this is how it should it out. Let’s take a quick look at our original gene pool and let's plug in our numbers and see if this works.

Well we have here P², here is p. So 0.58² that's p² equals, I do some quick math and I get 0.34. And if you remember, that’s roughly 1/3, that’s 2 of our 6, hey yeah that works. What about 2pq? Well 2pq equals 2 times 0.58 times 0.42. You do some math and that’s simply 0.49. Again I’m rounding a little bit interestingly. And if I look, that’s rough 1/2 and 3 out of my 6 hey it matches.

Now you see how I’m plugging in the numbers on that, I'm just skipping to the end? Ways to get points on essays on Hardy Weinberg. And they like to ask these sorts of questions. Show the math, show the equation and it’ll help increase your score. Let’s do that last one q² and again see if it matches our predictions. q² is simply 0.42². Again I do some simple math and I get 0.18. And 0.18 that’s roughly a 6 and hey 1/6 is my population marks.

So yes this population is in Hardy Weinberg genetic equilibrium. So I’d say that the population was in Hardy Weinberg equilibrium. And that means that from one generation to the next, those gene frequencies shouldn’t change. But there is some assumptions that’s based on. So let’s take a closer look at what are the assumptions of the Hardy Weinberg equations.

First, since it’s a statistical method, it has to be assumed that we’re talking a large population. So if you predict from the Hardy Weinberg equations that you should have 64% of your population is homozygous dominant. But it turns out only say 47% are, then that is an indication that you’re either talking about a small population. Or at some point in the past, the population size greatly get reduced and that caused a tweaking of the predicted outcome.

And this is kind of like if you’re doing that thing with your friend’s coin, and you’re flipping the coins and you’re only flipping three times you know. If you only flip it like I said three times, you can’t get 1.5 heads and 1.5 tails, it just doesn’t work that way.

The thing next is no migration in and out of the population. If some individuals come in, who are all homozygous dominant, then they’re going to skew the results. So that’s another thing that Hardy Weinberg assumes isn’t happening.

Similarly no mutation. You can’t have the things changing. Because if a big R changes into a little r or vice versa again that’s skews the results. Just like if you’re flipping the coin, and instead of getting head or getting tail, the heads turns into tail or a into a foot that just screws things up.

Next up, random mating. Again this is statistical method. And it’s based on the idea that these combination are coming together randomly. And so, if you’ve been able to eliminate the first three assumptions, then that might clue in that the skewing of your Hardy Weinberg predictions is due to non random mating.

The next big one is natural selection. And this like I said is a biggy. Natural selection is giving advantage or disadvantage to one allele or the other. If say having little r was a big advantage, then the one individuals who’s homozygous recessive, he’s going to have great success in providing children for the next generation. So you’ll see a great increase in the numbers of little r’s in the gene pool.

So that’s the assumptions of the Hardy Weinberg equations. And again if everything matches our assumptions, then yes you’re in equilibrium and the frequencies will stay say one generation to the next. But if they aren’t matching out predictions, then this is the nice thing about Hardy Weinberg. Because it give scientist a direction. Rather than just saying something seems wrong, instead they can say, something is wrong. It doesn’t much my numbers, now I have direction in which to go, to solve the problem. To figure out what’s the cause.

So how will Hardy Weinberg show up on the actual exam? Before I get into it, I really recommend that you go online, and check out the official version of the AP lab that deals with Hardy Weinberg. Because that will give you a good example of the kind of questions they may show you and some of the contexts. Also in your bonus materials folder, I’ve also included a worksheet that I gave to my students.

Now because you’re getting a chance to work on it at home I’ve made the numbers pretty hard. On the AP biology test, and in fact on most teacher's test they don’t let you use a calculator. And that’s actually a good thing because that means the numbers that they’re going to give you are pretty easy. So if you don’t know them already, I’d spent a little bit of time just brushing up on your common squares and common square roots. And it’ll make spotting the right answer much faster and much easier.

So let’s take a look at one of the first kinds of questions that they’re going to show you. So here for example, if the frequency of little r, the non rolling alleles is 0.6, then what’s the frequency of the heterozygote? Or the heterozygous individuals in the population?

Well I recall little r is, that’s q. So if I know q equals 0.6, and this is one of the tricks for maxing out your score on the AP exam, the essay portion. State everything. So q equals 0.6, well then I write my equation p plus q equals 1. Again, I just got myself a point by stating one of the equations. I plug in my numbers. And again, show your work. Imagine you’re doing one of your first geometry proofs, and your teacher's sitting there with a ruler ready to get you if you skip something.

So I plug it in, so p plus 0.6 equals 1. So I solve and I get p equals 0.4. So far so good, so now p is 0.4, q is 0.6. So heterozygous individuals they’re 2pq. Plug in my numbers 2 times 0.6 times 0.4, sorry I reversed p and q. I do some math and I get 0.48. So far so good.

Now this was one of the easier questions, because they gave you what q was. What they really like to do is trick you. Let’s take a look at the standard trick question. And I can tell you it’s a standard trick question because I use it all the time on my test. 0.91 of the population can roll their tongue, which is a dominant trait. What’s the frequency of the homozygous dominant individuals?

Now people will sit there and go, "I know it’s 0.91." They’re trying to soccer you in. Because they see 0.91 they say they can roll their tongue, it’s an easy question. No it isn’t. Remember this is the potion of the population that has at least one big R. This includes both the homozygous dominants and the heterozygotes. So the trick is find the q’s, find the q² individuals.

If 100% of the population is 1, then 1 equals p², plus 2pq, plus q² right. So let me plug in. I know that P² plus 2pq is 0.91 plus q². That tells me q² is 0.09. Now I got that, now I take my square root of both sides and I get q equals 0.3. I’ve got q, now p plus q equals 1. Plug it in, go over here. And so I get p equals I do some math 0.7. Now I just say p² my homozygous dominant, is 0.7² or 0.49 and there we go. That’s it, that’s not that hard.

So the trick is, read what they’re giving you, if they say the frequency of the gene is then they’re giving you p or q. The frequency of the alleles. If they say some fraction of the population, then you start thinking they’re trying to trick me. Read very carefully. Are they saying 91% of the population do this dominant thing? They’re trying to sneak it past you. Look for the freaky ones, look for homozygous recessives. Find them, and then you can get q. Once you get q then you can get p, and then you can plug it in to figure out whatever genotype that you want. And that’s it.

Outside of the whole square root thing, none of the math is actually all that hard. And in fact, in the most recent question that involved Hardy Weinberg, they actually gave you p, and they gave you a q. So don’t get too wordy about it.

And remember, the Hardy Weinberg equation is all about describing the gene frequencies, and genotype within a population. Now, it’s based on some assumptions, things like known natural selection or a large sample size, or large population. So if all those assumptions are met, then you don’t expect to see any changes from one generation to the next. If you do see changes, or you see that the predictions don’t match the outcome, then it’s because one or more of those assumptions have been broken.

Go through the end of the chapter questions in your textbook, do some of the problems, and that will give you the practice that you need to do well in the AP exam. And if you can handle all of the questions on my worksheet, then you’re pretty good. You’ve mastered Hardy Weinberg. Just be careful I made them tough and I’ll make you actually to think.

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