Incomplete Dominance: Definition, Examples, and Practice Problems

You may already know that in the study of genetics, dominance refers to the relationship between alleles, which are two forms of a gene. In a dominant relationship between alleles, one allele “masks” the other and influences a specific trait.

When the phenotype (the observable characteristic) of the heterozygote is identical to the dominant homozygote, the relationship is considered to be “complete dominance.” Since genetics is full of variations and changes, complete dominance isn’t always the outcome but rather incomplete dominance.

In this article, we’ll give you an in-depth explanation of incomplete dominance (also known as partial dominance), some examples, and a practice problem so that you can try out on your own, so you can gain a better understanding of this type of relationship.

A Quick Look At Important Terms

As you study genetics, you may find that it’s difficult to remember all the of the terms and what they mean. Before you can completely understand incomplete dominance, it’s a good idea to go over some basic genetic terminology.

Gene: The DNA for a trait
Allele: A different or variant form of a gene
Heterozygote: An individual with two different forms of a specific gene, one from each parent
Homozygote: An individual with two identical forms of a gene, results in true breeding for a characteristic
Phenotype: Observable characteristics of the genetic makeup
Genotype: The genetic makeup of an organism, such as traits

Now that we’ve reviewed a few of the genetic terms that you’re likely to see frequently when learning about partial dominance let’s move on to the concept of partial dominance.

Mendel’s Law of Dominance

Gregor Mendel is often referred to as the “Father of Genetics” because without his experiments, persistence, and years of research we probably wouldn’t have a good understanding about who we are or why we share traits with our ancestors. Mendel created three “laws” that he is known for: the law of dominance, the law of segregation, and the law of independent assortment.

To get a better understanding of partial dominance, we’ll take a closer look at Mendel’s “Law of Dominance.” In this “law” Mendel found (through his years of experiments) that the dominant trait is the trait whose appearance is always in the offspring. As we mentioned earlier, dominance is the relationship between the two alleles.

If someone inherits two different alleles from each of the parents and the phenotype (such as hair or eye color) of only one allele is noticeable in the offspring, then that allele is dominant.

If one parent has two copies of allele “A” (which would be dominant) and the other parent has two copies of allele “a” (which would be recessive), then the child will inherit an “Aa” genotype and still display the dominant phenotype.

Now that we have a full understanding of the dominance relationship between alleles, let’s see how the partial dominance differs.

Incomplete Dominance: What Is It?

We understand complete dominance, but you might still be wondering how partial dominance differs. Is it much like the name suggests? Partial dominance is when one allele for a specific trait is not entirely dominant over its counterpart (or the other allele). The result, which is seen in offspring, is a combined phenotype.

What does this mean? The traits of each parent are neither dominant or recessive. In a partial dominance relationship, between two alleles, a third phenotype is a result and is a combination of phenotypes of the two homozygotes; this is often referred to as an “intermediate form of inheritance.” The alleles do not blend, but partial dominance is often referred to as “blending” because traits are mixed and appear to be “blended.”

Examples of Incomplete Dominance

A better way to understand partial dominance is through examples and here are a few:

Snapdragon Flowers

A common example of partial dominance that many instructors of Biology use in the genetics unit are a snapdragon flower. In this example, the Snapdragon is red or white.

If a red homozygous snapdragon is paired with a white snapdragon (which is also homozygous), the hybrid result would be a pink snapdragon. Here’s how it the partial dominance looks when broken down:

The genotypes are Red (RR) x White (rr) = Pink (Rr)

When the first offspring (F1) generation, which is all pink flowers, cross-pollinates, the resulting flowers in the F2 generation consist of all the phenotypes: ¼ Red (RR): ½ Pink (Rr): ¼ White (rr). The phenotypic ratio is 1:2:1.

If the F1 generation cross-pollinates with the “true breeding” red flowers (homozygotes), the F2 generation will result in red and pink flowers (half-red and half-pink); the phenotypic ratio is 1:1.

If the F1 generation cross-pollinates with “true breeding” white flowers, the F2 generation will result in white and pink flowers (half of each and a phenotypic ratio of 1:1).

In the case of partial dominance, the intermediate (or 3rd ) trait is the heterozygous genotype. The pink snapdragon flowers are heterozygous with an Rr genotype, and the red and white flowers are homozygous for flower color with genotypes RR and rr (or red and white).

While snapdragon flowers are a common example, you can find the same results with red and white tulips, roses, and carnations.

Incomplete Dominance in Animals

Just like plants and humans (which we’ll give an example of briefly), partial dominance can occur in animals; as it can occur in every living organism.

Let’s look at an example of rabbits. If a breed with long fur, like an Angora rabbit, mates with a breed with short fur, like a Rex rabbit, the offspring is likely to have fur that is in the middle; not too long or too short.

Andalusian chickens are also a popular example of partial dominance in animals due to their unique blue-ish feathers. The chickens don’t always have slate blue feathers, but it is often a result of a white rooster mating with a black hen. Since both parents have the inheritance of blue alleles (about 50%), the offspring is likely to have feathers with a splash of blue.

If you consider cats and dogs, there are usually some cats or dogs that have more markings than one of the same breed. When a heavily spotted or market dog or cat marks with a mate that has solid-colored fur (and no markings), the offspring is likely to have some markings but not the same as either parent.

Partial dominance can apply to the length of tails, the color of fur, and many other phenotypes in animals.

Incomplete Dominance in Humans

By now, you’re probably able to see a pattern in how partial dominance works in genetics. It’s a complex idea, but when you break it down it’s not as complex as some people make it, right?

Consider some ways that partial dominance may occur in humans. Like the fur length on an animal, the child of one parent with curly hair and the other with straight-hair is likely to have wavy hair. Both straight and curly hair is dominant, but neither one dominates the other.

Diseases like sickle cell disease or Tay-Sachs disease is another example of partial dominance in humans. Skin color, height, voice pitch, and even the size of one’s hands can all be attributed to partial dominance.

Think about your own features. Are you a carbon copy of one of your parents or do some of your features sit “in the middle” and are a result of partial dominance?

A Practice Problem For Incomplete Dominance

Whether you want to study up on partial dominance or just want to play around with some scenarios and see what you come up with, take a look at a few of these practice problems.

A cross between a bird with blue feathers and a bird with white feathers produces offspring with silver feathers. The color of the birds is determined by only two alleles.

1What are the genotypes of the parent birds?
2What is the genotype of the bird with silver feathers?
3Can you figure out the phenotypic ratios of the offspring of two birds with silver feathers?

The answers are as follows. How did you do?

The answer for #1 is BB (homozygous blue) for the bird with blue feathers and WW (homozygous white) for the bird with white feathers.

The answer to #2 is one blue allele and one white allele. Since neither allele is dominating another, we get a “blend” which results in the bird with silver feathers.

To figure out #3, you need to fill out a Punnett Square. Silver x silver = BW x BW. Your results should be 25% of offspring are homozygous white (WW), 25% are homozygous blue (BB), and 50% are hybrid, which means they have silver feathers.

7 Cell Raps to Help Memorize the Functions of Cells

If you’re studying for a science test, one of the best ways to help remember the material is by setting to music! That’s right; cell raps can help you remember the names of the organelles located in each cell, as well as their functions.

We’ve rounded up our top seven picks for cell raps that we think you’re going to love.

Best Cell Rap for Sixth-Graders: Cells Cells by Crappy Teacher

5 out of 5 stars

As YouTuber CrappyTeacher (Emily Crapnell) explains in her cell rap video, she created this video to help her sixth-grade science students learn the different parts of a cell. At over 5.7 million views, it seems that this cell rap has caught on with more than just Crapnell’s students! We can’t blame people for watching it; it’s catching and makes science–dare we say it?–fun!

“Today’s the day,” the rap begins; “let’s talk about the building blocks of life–cells that make us.”

The cell rap chorus covers some of the most vital parts of cellular biology. It explains that cells are made of organelles, and mentions cytoplasm, the nucleus (“controllin’ everything”), the membrane, the vacuole (“we can float around for hours”), and chloroplasts by name.

The next chorus explains that there are two different types of cells–animal and plant cells, while the final three stanzas are devoted to explaining in more details with each part of the cell does. “The cell membrane is the border patrol,” raps CrappyTeacher, and then later, “The mitochondria’s something every cell needs, breaking down the food and releasin’ energy.”

Over second thousand people have taken the time to comment on this cell rap. Many mention how they heard it years ago and still remember it, speaking to the catchy lyrics and the arresting beat. While designed for sixth-graders, the content is sophisticated enough that even college students report finding it helpful!

We also feel like it’s one of the best mixes of catchy lyrics and useful information, managing to find a good balance between repetition and new information. Plus, it provides a great video with very helpful images which will further solidify the information in your mind. For these reasons, we’ve given it five stars!

The rap can be viewed here or may be purchased.

Best Karaoke Option: The Cell Song by Glenn Wolkenfeld

5 out of 5 stars

The Cell Song, created and sung by Glenn Wolkenfeld, isn’t a cell rap–but it is a fantastic way to use the power of song to help commit the parts of a cell to memory! And with over two million views, we’re not the only people who think so.

The song is a folksy, bluesy tune where the singer asks what happens when he goes into a cell. “Who drives this bus,” sings Wolkenfeld, and then he “found myself talking to the boss, the nucleus.”

Wolkenfeld does two things in this song; he gets deeper into the molecular biology involved in the parts of a cell, and he offers a karaoke version.

Unlike some of the other cell raps available, The Cell Song explains that chromosomes stores genetic information, the ribosomes make proteins, and the lysosome use enzymes to dissolve, and centrioles organize chromosomes into spindles.

Wolkenfeld also uses The Cell Song to explain how rigid cell walls allow plants to grow extremely tall, and the purpose of green in the plant cell. “I went into a plant cell, ‘why’s it so green?’” sings the artist. “‘Cause I make food from sunlight,’” answers a green chloroplast.

The video is filled with helpful drawings and diagrams to further illustrate each concept. Wolkenfeld, as we mentioned already, also offers a karaoke version, which is the same version, but instead of Wolkenfeld singing, the lyrics are on the screen.

The Cell Song, like Cells Cells by CrappyTeacher, also gets five stars thanks to its ability to combine great video content with helpful, relevant information about cells.

You can find The Cell Song here, and the karaoke version here.

Best Song With Video: The Parts of a Cell Song by Jam Campus

5 out of 5 stars

The Parts of a Cell Song is a cell rap created by an organization called Jam Campus. It’s one of many Jam Campus creations; in fact, the YouTube channel creates educational videos on everything history to science to mathematics.

With over 54,000 views, The Parts of a Cell Song is catchy and well-loved. What we especially love, in addition to the self-made music, is the high quality illustrated video! Any time you can marry great visual images with catchy lyrics, you increase the likelihood of you remembering the information.

The Parts of a Cell Song gets right down to business, stating in its first line, “here’s what each cell contains, outer layer is the cell membrane.” The lyrics point out where cells get their energy (mitochondria), and what ribosomes do (help with protein synthesis).

We also appreciate this lyric, which helps to sum up the parts of a cell, something most cell raps don’t do:

Cell membrane, mitochondria, lysosomes and the ribosomesCytoplasm, nucleus, E.R. and Golgi body, and the nucleolus

We especially appreciate how accurate the presented information is here (many cell raps mistakenly identify ribosomes as making proteins; however, they simply help in the assembly of polypeptides, chains of amino acids, which are the building blocks of protein), which is a big part of why this song gets five out of five stars.

Best for Repetitive Learning: The Cell Rap with Mr. Simons’ Fifth Grade Class

4 out of 5 stars

Mr. Simons and his fifth grade have teamed up to create another great cell rap, available on YouTube. This cell rap has approximately 468,000 views, and we understand why–out of all the cell raps we’re sharing today, this one is probably the most likely to get stuck in your head!

Every song has to decide how to balance repetition with new information; as you’ll see later, some of the cell rap songs we’ve rounded up choose to focus on including as much data as possible. This rap, however, from Jake Simons, focuses on repetition.

In fact, we feel it focuses a little too much on repetition (we downgraded it to four stars), but it’s still a great rap that will help cement many of the things you’re learning about cell biology into your memory.

This five-minute rap features the cytoplasm, the nucleus, the membrane, the vacuoles, and the mitochondria of the cell. Here’s an example of a lyric:

“Just like us, the cell has energy. The mitochondria takes the food and puts it where it needs to be.”

Here’s another line from the cell rap, this one memorably explaining how the cell membrane works:

“There’s a thing called a membrane that holds it all in place so none of us will ever complain.”

Is this the cell rap to turn to if you need to memorize complicated material? Probably not; but it is a great option for younger students or people who need just the basic parts of a cell!

Best Use of Additional Resources: The Cell Song by Keith Smolinski

4 out of 5 stars

The Cell Song was written and recorded by Dr. Keith Smolinski as part of a doctoral study to research how music can help students learn complex science concepts. In addition to The Cell Song, which features the parts of a cell, there are another nine songs sold in an album called Biorhythms: The Music of Life Science.

Songs in Biorhythms cover everything from cellular division, to the digestive tract, to the ecosystem. The song we’re featuring, The Cell Song, isn’t a cell rap, but it is well-performed, catchy, and interesting to listen to!

While the accompanying video doesn’t include images (that’s why it only has four stars and not five), it does utilize the lyrics on screen. In just two minutes and nineteen seconds, Dr. Smolinski manages to cover everything from the nucleus to the cell membranes.

In The Cell Song, listeners learn that the nucleus contains the genetic code, the mitochondria are the power plants of the cell, and the vacuoles store food and water. We also learn that the ribosomes make proteins, the Golgi bodies pack and ship the proteins, and the endoplasmic reticulum carries them.

Plus, the song teaches that lysosomes are janitors, cytoplasm is gel-like, and cell membranes help regulate what comes in and out of the cell.

In the notes section of this video, Dr. Smolinski also explains that additional teacher’s resources are available on his website, including a Teacher’s Guide for The Cell Song. All of Dr. Smolinski’s resources are based on the National and State of Connecticut Science Standards, so you can be sure you’re getting accurate and helpful information.

Best Rap Alternative: Organelles Song by ParrMr

4 out of 5 stars

ParrMr, a YouTube creator, has garnered over one hundred thousand subscribers thanks to her (or his!) ability to put science lyrics to popular songs. If you cringe over cells raps or want music you’re already familiar with, you can find videos on everything from Pangaea to the atmosphere to the planets.

ParrMr’s songs are set to hits like Forget You by Cee Lo Green, Toothbrush by D’NCE, and Jealous by Nick Jonas. The one we’re featuring here, with four out of five stars, is Organelles Song, set to Counting Stars by OneRepublic.

The music is easy to remember if you’re already familiar with the song–our one complaint, however, is that the lyrics have very little repetition. This has the upside of packing a ton of information into the four-plus minute song, but if you’re trying to make sure the material sticks, this might be a downside.

“Look inside a cell,” sings ParrMr, who created this song for his or her sixth-grade students, “and you will see…organelles have jobs, yeah, organelles have…jobs.”

The next lines focus on how plant cell walls and cell membranes protect the line like a fence, letting the right things in and out. ParrMr covers vacuoles, lysosomes, the nucleus, chromatin, DNA, and ribosomes.

The final stanza explains proteins and their relationships to the endoplasmic reticulum, Golgi bodies, and cytoplasm. Mitochondria and chloroplasts are also mentioned.

Organelles Song by ParrMr has racked up over 700,000 views, and for a good reason–we give this cells video four out of five stars!

Runner-up Rap Alternative: Cells Song by ParrMr

3 out of 5 stars

Another much-loved option (four hundred thousand views!) by ParrMr, also for a sixth-grade classroom, this is another song about cells set to hit music. This one, called Cells Song, is set to Sail by AWOLNATION.

In it, ParrMr sings about cell membranes, cytoplasm, organelles, mitochondria, endoplasmic reticulum, ribosomes, and Golgi bodies.

“Cells cells cells cells cells,” he sings, before starting another chorus about vacuoles, the nucleus, and lysosomes.

Here is the final stanza:

Capturing Sun’s energyChloroplasts in plants and treesAnd cell walls giving box-like shape, rigid

If you’re a fan of pop or dance music or are simply looking for a non-rap alternative to cell raps, this is a great option. It’s short on useful information, but what is included is presented appealingly, and will be likely to stick!

Thanks to these seven awesome cell raps, we have a feeling you’re going to ace your next quiz or test. We’d say good luck, but we don’t think you’ll need it!

7 Bio Poem to Help Remember the Hardest Material For Biology Test

Biology is a massive subject, and if you’re trying to study for a test, remembering all those facts, strange Latin names, and confusing concepts can seem impossible. The smartest students, however, have found clever ways to increase the amount of information they remember. One of the best ways is using a biology poem to help remember the difficult material.

A bio poem is a mnemonic device or a simple poem that includes the facts, names, or concepts you’re trying to remember. The idea is that your brain retains the information better that way, and when it comes down to test day, you’ll be able to call forth the learned material by reciting the poem.

Below, we’ve listed seven bio poems that will help you perform better on your next exam. Plus, keep reading for the ultimate guide on remembering difficult things and studying for big exams.

How We Chose Our Ratings

You can see below that we’ve rated the poems we’ve included in this roundup; since we’ve scoured available bio poems, we’ve been able to bring you only the best and most helpful.

Top 7 Best Bio Poems

Best Classic Biology Poem: Dear King Philip

5 out of 5 stars

A mnemonic device is a great way to help our brains remember complicated groups of information–especially when the data has to go in a specific order. The Dear King Philip device has been used for generations to help students remember the order of taxa in biology.

The order is as follows: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Each of the mnemonic’s first words matches the words of the taxa, in order: Dear King Philip Came Over For Good Spaghetti.

It sounds ridiculous and hilarious, but that’s exactly why it works so well; because it involves our emotional response (laughter and hilarity), we’re more likely to remember it! Other variations include the following:

Dumb Kids Prefer Cheese Over Fried Green Spinach
Do Kings Play Chess On Fine Green Silk?
Dakota Kills People Cause Other Friends Got Sad

The following two classic biology mnemonics don’t include the letter D, so if your biology professor doesn’t ask for you to remember Domain, these will work better for you:

Keep Pond Clean Or Fish Get Sick
Kids Pick Candy Over Fancy Green Salad

You can also make up your own.

With or without the Domain, a taxon is a group of organisms. Taxonomists use these groups to organize what we know about animals. African elephants, for example, form the genus Loxodonta. While scientists largely agree on where African elephants belong, they often disagree about other classifications, a fact that isn’t widely known!

Best Basic Bio Poem: MRS GREN

5 out of 5 stars

Mnemonics can help us remember extremely simple things (the difference between dessert and desert, for example, is the extra s, which gives you a clue about its meaning. Don’t you want to eat more dessert?) but they can also help you outline more complicated concepts.

Biology teaches us that seven processes define living things, and once again we turn to a mnemonic to help us remember that process: MRS GREN.

The letters stand for the following:

M → Movement
R → Respiration
S → Sensation

G → Growth
R → Reproduction
E → Excretion
N → Nutrition

Movement is a vital process for living things as it allows them to find or better position themselves to attract or produce food.

Respiration is the process through which living things convert energy from carbohydrates and fats. Most of the organisms we’re familiar with use oxygen to break down (this produces a by-product know as carbon dioxide), but some organisms utilize nitrates, iron, or other material to break the sugars down.

Sensitivity is connected to movement and, in fact, is what triggers movement for many organisms. An organism is a living organism if it can react to changes in its environment. A plant, for example, will move its leaves towards the sun or towards a grow light.

Just like sensitivity and movement are connected in this bio poem, so growth and respiration are connected. In fact, it is respiration that allows for growth!

The excess energy organisms create when they break down sugars during respiration can be used in the production of new cells–whether that’s a larger shell (as in the case of a snail) or a new leaf (as in the case of a plant). Special note: for growth to be considered, it must be irreversible.

Reproduction is the fifth of the living processes that define whether or not something is alive. It can range from the ultra-simple division of cells to the conception of new human life!

We’ve already referenced one by-product that occurs during normal function in a living cell–carbon dioxide. Carbon dioxide is excreted and is an example of the sixth living process: excretion. A living simple creates waste as it functions normally, and this waste must be excreted.

Nutrition is the taking in of food. That food can vary wildly and can be anything from water in the soil to other organisms. Regardless, nutrition is a vital part of the living process.

Best Bio Poem for Phases of Mitosis: I Passed My Anatomy Test

5 out of 5 stars

Another great bio poem that lends itself to helping us remembering the phases of mitosis is this one: I Passed My Anatomy Test. The letters (I, P, M, A, and T), stand for the following phases:

Prophase
Metaphase
Anaphase
Telophase

If your professor requires you to learn about cytokinesis, as well (this phase begins during anaphase or telophase), you can add the word “calmly” onto your bio poem so that it reads: I Passed My Anatomy Test Calmly.

Other possible devices for the phases of mitosis include the following:

I Propose Men Are Toads
Idiot, Pass Me Another Tequila
I Picked My Apples Today

Which device should you select? Choose the one that makes you laugh, smile, or that sticks in your head readily. The easier it is for you to remember, the better!

Best Bio Poem for Embryonic Development: Zikes!

5 out of 5 stars

There are four stages of embryonic development:

Zygote, in which the fertilized ovum (the united sperm and egg cells) begins to divide rapidly
Morula, which is comprised of 10-30 cells
Blastula, which gets its names from the Greek word for “sprout,” and in which the morula forms an inner cavity filled with fluid, forming a blastula
Gastrulation is the embryonic phase in which the blastula (single-layered) turns into the gastrula (three-layered)
Neurula, in which the nervous system becomes to develop

The first letters of each of these stages correspond to the following mnemonic: Zikes! Martin is a Big Giant Nerd! (Note that “is” and “a” aren’t counted!)

Best Bio Poem for Taxonomy of Humans: All Cool Men

5 out of 5 stars

A common question that likes to pop up on biology tests is about the taxonomy of humans, and these clever devices help us remember the right order.

First, here’s the taxonomy: Animalia, Chordata, Mammalia, Primate, Hominidae, Homo sapien.

Now, here’s the mnemonic: All Cool Men Prefer Having Heavy Sideburns.

Best Bio Poem for Kingdoms of Life: Biology People

5 out of 5 stars

If you’re confident the kingdoms of life will show up on your biology exam soon, here’s a great bio poem to help you remember the five kingdoms: Biology People Find Plants Attractive.

It will help you remember these five kingdoms:

Bacteria (monera)
Protista
Fungi
Plantae
Animalia

Best Bio Poem for Major Fungal Classes: Zombies

5 out of 5 stars

Another hilarious mnemonic device–Zombies Are Brown and Dirty–is one of several that can help you recall the major fungal classes!

The classes are:

Zygomycetes
Basidiomycetes
Deuteromycetes
Ascomycetes

In addition to Zombies Are Brown and Dirty, you can use:

Zap A Bear Dead
Zebras Are Big Dummies
All Zebras Dance Badly

Using Poetry to Help You Remember Things

Memory is a fascinating process and understanding how it works can help you better study for your next exam–with or without a bio poem!

The first step in remembering is called encoding. Encoding is the process through which something external–an interaction with another person, a biology concept, or the route to a new place, for example–is converted into a construct. A construct is stored inside the brain and if it’s laid down correctly, can be played later, like a movie.

Encoding a Memory

Encoding begins when we pay attention to something, and our interest in the subject matters hugely, as does emotion. This is why, for example, it’s so easy to remember the lyrics from a favorite song. Music can evoke emotion, and because we like the genre, we’re paying close attention.

However, you probably have trouble remembering the name on the nametag of the person who checked out your groceries this morning–because you weren’t very interested and because no emotions were called for.

This is why poetry is so helpful. By translating obtuse concepts into funny, interesting rhymes (even if you don’t think the rhyme is interesting; the new combination of words that rhyme is read as unusual and worth paying attention to by your brain) help you recall complex or boring material at a later time.

Two More Powerful Memory Devices

Using bio poems, however, isn’t the only way to remember complicated information. There is a whole host of available memory devices that can improve your ability to retain and recall reams of data. Here are just a few:

1. Method of Loci

“Loci” means “places” in Latin and the method of loci is often called the memory journey or the memory palace in today’s world. This memory device has been around since the time of the ancient Romans and Greeks (Cicero, for example, wrote about it in his De Oratore). It’s used today by champion memorizers and sometimes even shows up in pop culture (in the hit television show Sherlock, for example).

To use the method of loci, visualize the physical layout of a place that’s familiar to you–your bedroom, for example. Then, assign a concept or term to the different objects in your bedroom. Here is an example of how you might assign parts of a cell:

Doorway → lysosome
Carpet → nucleus
Nightstand → nucleolus
Lamp → microtubules
Water bottle → cytoplasm
Clock → Golgi apparatus
Bed frame → mitochondrion
Mattress → Golgi vesicles
Pillow → rough endoplasmic reticulum
Bedspread/comforter → smooth endoplasmic reticulum
Curtains → cell membrane
Poster → centrioles
Trophy → pinocytotic vesicle

You can assign more than just the name to each place in your bedroom; you can also assign the function of each part of the cell.

This way, when you get to a test question that asks you to name the parts of a cell and their functions, you can mentally “walk” through your room, and each object in your room will help trigger your recall so you can answer the test question.

2. Chunking & Organizing

Chunking is a method of memory recall best explained by two popular examples: telephone numbers and social security numbers.

Telephone numbers have as many as eleven numbers, and social security numbers have nine; a string of eleven numbers or nine numbers would be difficult to memorize, but by organizing the strings into smaller chunks of numbers, they’re accessible to even small children!

This is a great device to use when you’re dealing with long strings of information because you’ll be able to focus on smaller groups instead of larger pieces of data, which have the added issue of being overwhelming!

Your Best Exam Yet

Thanks to the seven bio poems and two memory devices we shared above, you’re all set for your best exam yet. Good luck!

Significant Figures Worksheet(Sig Figs): Definition, Examples, and Practice

Meta: Whether you’re relatively new to significant figures or are just looking for a refresher, you’ve come to the right place. Read on to learn more!

Significant Figures (Sig Figs): Definition, Examples, and Practice

Significant figures are a vital concept when you’re working in any field that requires precision; chemistry, for example. And while it feels like a complex subject, it’s fairly simple and straightforward. In this article, we’re answering your questions about significant figures and prepping you for significant figures worksheets with lots of examples.

Reason for Significant Figures

We can all agree that there’s nothing worse than complicated mathematics concepts that don’t seem to have anything to do with real life. Fortunately, that’s not the case with significant figures! The primary purpose for this somewhat abstract concept is precision.

The numbers we use in everyday life, as it turns, are not that precise. When you’re working in specialized fields, however, the precision of the data is everything. Significant figures help you communicate how precisely you’ve measured and help to ensure mistakes are made with the data.

Let’s Build a Tower

Here’s an example: let’s say you’re building a tower. As you might imagine, precision matters hugely. You don’t want to get to the top of the tower only to realize your tower is taller–or shorter!–than you thought. Let’s say, then, that the steel manufacturer has measured its vertical beams to the nearest centimeter and is sending you three beams that are each 20.5 meters tall.

This measurement is precise to the centimeter, but the number doesn’t tell you anything about millimeters. This is a problem because the glass you’re cutting to cover the building in is measured to the nearest millimeter; in fact, the glass company is sending the glass to you in 15.75-meter sheets.

You know that your steel beams will stand end to end and that your finished tower will be (20.5*3) meters tall, or 61.5 meters tall. Three glass sheets will be 47.25 meters tall; too short. Four glass sheets will be 63 meters tall; too tall. You’ll need to lay three sheets of glass and cut the fourth to size. Now you need to figure out how much you should cut down that fourth sheet of glass.

The Problem With Imprecision

Here’s the problem: your steel is measured to the centimeter, but the glass cutter cuts to the millimeter. Each steel beam is 20.5 meters, which means it’s twenty meters and five centimeters; but how many millimeters is it?

We don’t know. It could be three millimeters (20.53 meters), or it could be seven millimeters (20.57 meters). Let’s say it’s the latter, and your three steel beams each have an extra seven millimeters that you don’t know about because they’ve only been measured to the nearest centimeter.

You think you’ve only got 61.5 meters of a tower (because 20.5*3 = 61.5) but you have 61.71 meters (because 20.57*3 = 61.71). That’s a difference of .21 meters, or a whopping two centimeters and one millimeter! If you cut your glass to 61.5 meters, you’ll get to the top of the tower to install it–only to realize you’re missing two centimeters and a millimeter of glass.

Oops!

This is an oversimplified example, but it helps to illustrate how important precision is–and now you know how significant figures work, even if you don’t know the concept by that name yet. That’s for the next section!

Rules for Significant Figures

The first thing you should remember is that significance doesn’t indicate whether a number is computed or not; it simply indicates the precision of measurement. We’ll explain; let’s start with the basic ground rules about significant figures, and then we’ll practice with some examples you might see on a significant figures worksheet:

If it’s not a zero, the number is a significant figure (e.g., 1, 2, 3, 4, 5, 6, 7, 8, and 9 are all significant no matter where they are in the number)
If a zero is between a non-zero digit, it is significant (e.g., the zeros in these numbers are significant: 507, 5007, 5000.07)
Trailing zeros (the zeros at the end of a number) are only significant if the number has a decimal point (e.g., 5.0500 or 5.50); they are not significant if there are no decimal points (e.g., 500 or 50) (special note: in the latter case, significance can be indicated with a bar above or below the last measured figure)
Leading zeros (zeros before non-zeros) are never significant (e.g., 005 or 0.005)

EXAMPLES

51 has two significant figures (5 and 1; all numbers are non-zeros)
1234.56 has six significant figures (1, 2, 3, 4, 5 and 6; all numbers are non-zeros)
505.5505 has seven significant figures (5, 5, 0, 5, 5, 0, and 5; all non-zeros are significant, and all zeros between non-zeros are significant)
0.0057 has two significant figures (5 and 7; the zeros are leading and are not significant)
500 and 50 each have one significant figure (5 and 5; trailing zeros are not significant unless there is a decimal point)
5.0500 has five significant figures (5, 0, 5, 0, and 0; the first zero is between two non-zeros and the trailing zeros are significant because the number contains a decimal)
0.00050500 has five significant figures also (remember that leading zeros do not count)
1300 has two significant figures (one and three) while 1300. has four significant figures (1, 3, 0, and 0) because the latter number has a decimal point

Multiplying, Dividing, Adding, and Subtracting with Significant Figures

Before we get into the mechanics of multiplying, dividing, adding, and subtracting with significant figures, you’ll first need to know how to round up significant figures. For example, if you have a number (let’s say 54.896) that has five significant figures, and you need to round it up to three significant figures, how do you do that?

Rounding Up

Here’s how:

Identify the significant figures (in our example, there are five significant numbers: 5, 4, 8, 9, and 6)
Identify the last of the desired significant figures (we know we need three significant figures, so eight, the third significant figure from the left, is the last significant figure)
Look at the number to the right of the significant figure. If it is five or greater, add one to the last significant figure (in our example, eight is followed by nine; nine is greater than 5; therefore, eight is rounded up by 1 to 9 so that our new number is 54.9). If, however, the number is four or less, simply remove all the remaining numbers to the left (don’t replace them with zeros)

Here’s another example using 0.01234500:

If you want to round it to three significant figures, the answer would be 0.0123 (leading zeros are not significant; 4 is less than five, so 4 and all subsequent numbers are removed).

Special note: rounding significant figures is different than rounding decimals. For example, if you wanted to round our example number to three decimal places, the answer would be .012, which is a different number altogether from a precision standpoint.

Multiplying and Dividing

When you begin working seriously with multiplying and dividing, you’ll notice how quickly things can move from precise to imprecise. For example, let’s go back to our tower example and say we want to measure the area of our glass sheets. They are 15.75 meters tall and 2.5 meters wide.

A simple calculation (15.75*2.5=39.375) tells us the area is 39.375, but if you’re thinking, “wait! That measurement is more precise than what we measured!” you’d be right. To keep our quotients and products as precise as our initial measurements, we need to round up (or down).

The general rule is that the significant figures in the answer cannot be more than the smallest amount of significant figures used in the equation. In our glass sheets example, the two numbers we multiplied are 15.75 (which has four significant figures) and 2.5 (which has two significant figures). The smallest number of significant figures in either of these factors is two, so our answer can’t have more than two significant figures.

Our answer (39.375) has five significant figures, with 9 being the second significant figure. The number to the right of 9 is 3, which is less than 5, so we simply discard 3 and everything to its right. Our answer, then, is 40. (9 rolls to the 0 and the 3 becomes a 4; also note the use of the decimal!).

Adding and Subtracting

Adding and subtracting numbers with different amounts of significant digits is very similar to multiplying and dividing, except that the rounding up (or down) happens before the calculation.

Back to our tower example, let’s say you had one steel beam that was 20.5 meters and one that was 20.45 meters, you are dealing with two different levels of precision. The first beam has three significant figures and is less precise than the second beam, which has four significant figures.

If you add them together as is, it’s just messy. So, you need to round up the more precise number so that it matches the least precise number. That is, you would round up 20.45 to 20.5 and add both numbers (20.5 + 20.5 = 41.0; note that the answer is also precise to three significant figures).

Hopefully, significant figures are no longer mystifying, and you’re ready to tackle your significant figures worksheet; good luck!

Classification of Living Things: Definition, Examples, and Practice

For centuries, there were only two ways to classify living things; either as a plant or an animal. Today, thanks to the classification of living things, we can gain a better understanding of all living organisms. Learn more about the classification of living things and some tips for remembering the classification.

Classification of Living Things: Definition, Examples, and Practice

From an early age, we all learned the difference between plants and animals, and it probably wasn’t until a few years later when we learned that there are different types of animals and plants; even though they share some similarities, they are entirely different.

Centuries ago, living things were classified as either plants or animals. Today, the classification of living things helps us gain a better understanding of the world we live in, our relation to living things, and understanding Biology better overall. Let’s take a closer look at the classification, a little bit of its history, and some tips for learning how to use it when exploring a living organism.

What Is The Classification Of Living Things?

You might already know a little about the classification of living things, which is also referred to as taxonomy. Many students learn the basics of taxonomy in elementary school, but unless you spend a lot of time focused on Biology, the details may have become a bit fuzzy over the years.

Classification of all living things got its start with Swedish Botanist, Carl Linnaeus. Due to his interest in plants and animals, his first classification guide, Systema Naturae, was published in 1735.

Linnaeus, who is often considered to be the “Father of Taxonomy,” and his classification system is still in use today. While the classification system continues to grow, Linnaeus will always remain an integral part of how we name, rank, and classify plants and animals.

The classification system starts out by sorting living organisms into groups based on basic and shared characteristics (such as a plant or animal). Then each group is broken down further into more specific classifications; it might be helpful to think of a classification system like a family tree.

Next, we’ll take a closer look at the eight levels of the taxonomy, depending on your resource, you may see seven levels discussed.

Domain

The first or top level of the classification system is the domain. A domain has the most number of individuals in the group since it’s the broadest level. The domain level helps to distinguish between cell types. Currently, there are three types of domains, which include Bacteria, Archaea, and Eukarya.

Kingdom

Kingdoms are levels which are broken down from the domains. There are six kingdoms which include Eubacteria, Archaebacteria, Plantae, Animalia, Fungi, and Protista. While kingdoms are a little more specific, it should still be relatively easy to categorize a living organism based on the kingdom.

The Plantae Kingdom is broken down even further to include divisions. The following divisions include:

Bryophyta: mosses, liverworts, and hornworts
Psilotophyta: whisk ferns
Lycophyta: club mosses and quillworts
Sphenophyta: horsetails
Polypodiophyta: ferns
Coniferophyta: pines, spruces, redwoods
Ginkgophyta: ginkgoes
Cycadophyta: cycads
Gnetophyta: gnetophytes
Magnoliophyta: flowering plants

Learning the kingdoms can be a little tricky, and if you don’t get the kingdoms right from the beginning, you may have a difficult time classifying something correctly. Check out this checklist for figuring out which kingdom that an organism belongs to.

Phylum

The phylum is the next level in the classification system and is used to group living organisms together based on some common features. A good example to consider is when you sort your laundry by items of clothes. Your socks aren’t all the same, you most likely group them together and put them in the same dresser drawer.

Consider the animal kingdom, there is a phylum group called “chordates,” and it refers to all animals with a spinal column. As humans, we are also part of the chordate phylum. Like the Plantae Kingdom, phyla is broken down into divisions:

Porifera: sponges
Coelenterata: jellyfish, hydras, and corals
Platyhelminthes: flatworms
Nematoda: roundworms
Annelida: segmented worms
Arthropoda: arthropods like insects
Mollusca: mollusks like clams
Echinodermata: sea urchins
Chordata: chordates

Class

The class level is another way to group together organisms that are alike, but it becomes even more specific than phylum. There are more than 100 classes, but some of the more common ones that you’ll likely use on a regular basis in Biology class includes the vertebrates, invertebrates, dicots, or monocots.

Order

As you might guess, the order is just another way to break down the class of plants and animals. Think of it as “refining your search.” Some orders include carnivores, primates, rodents, fagales, and pinales.

Family

The next level in the classification of living organisms is categorized much like the group of people that we call family. We are all different, but we share enough similarities that we belong in the same family; the same applies to all living things.

Genus

The genus is the first part of a living thing’s scientific name, also known as binomial nomenclature. Let’s look at lions and tigers, for example, the scientific name for a lion is Panthera leo, and the tiger is Panthera tigris; Panthera is the genus.

Species

The species is the final and most specific level of the classification system. The best way to describe a species is a group of organisms that are best suited for breeding healthy offspring, which can also continue to reproduce.

Some Examples of Classification

Classifying living things takes a lot of practice, and while it may take you a long time to familiarize yourself with the scientific names in a domain or phylum, it’s best to learn and memorize the levels of classification as soon as you can. Forgetting about the phylum or order can make the classification process even more difficult.

Many people use a mnemonic device to remember the order of the levels of taxonomy. Some people use “Dear King Phillip Came Over For Good Soup,” but you can come up with whatever and works best for you.

Let’s take a look at a few in-depth examples. We’ll start out by classifying humans.

Classification of Humans

The Domain is Eukarya because we have a nucleus and organelles. The Kingdom is Animalia because we ingest food, are multicellular, and have no cell walls. The Phylum is Chordata because we have spinal cords (our subphylum is vertebrata because we have a segmented backbone).

The Class is Mammalia because we nurse our offspring and the Order is Primates due to our higher level of intelligence. The Family is Hominidae because we are bipedal (walk upright). The Genus is Homo for Human, and the Species is H. sapiens, which means modern human.

The result is Homo Sapiens, which as we all know translates to today’s human beings.

Classification of a Fruit Fly

Everyone will agree that fruit flies can be a nuisance, but they can be a fascinating organism to study. Here’s how we can classify a fruit fly.

The Domain is Eukarya because it has a nucleus and organelles. The Kingdom is Animalia because it ingests food, is multicellular, and has no cell wall. The Phylum is Arthropoda due to the hard exoskeleton, paired legs, and a segmented body. The Class is Insecta because it is terrestrial, has six legs, and antennae. The Order is Diptera due to having two-wings.

The Family is Drosophilidae, the Genus is Drosophila, Species is D. melanogaster; also known as the common fruit fly. As you looked at the different levels of classification, can you see where we’re related to the annoying and small insect?

Classification of a Maple Tree

We can get syrup from a maple tree, and it has stunning foliage in the fall, but you probably haven’t thought much beyond that. Here’s the classification of a red maple tree.

The Domain is Eukarya because it has a nucleus and organelles and the Kingdom is Plantae since it makes its own food and has a multicellular cell wall. Immediately, we can see that a maple is nothing like a human.

The Phylum is Tracheophyta due to the tissue-level organization, and the Class is Angiospermae because it flowers. The Order is Sapindales because it produces sap and the Family is Aceraceae. The Genus is Acer, the Species is A. rubrum, and we end up with a red maple.

Classification of a Dandelion

People either love or hate dandelions but like other organisms, they are a living thing, and they have a complex level of classification. Let’s see if you can guess the Domain, Kingdom, and Phylum. Did you guess Eukarya, Plantae, and Angiosperms? Then, you’re right.

The Class is Magnoliopsida, the Order is Asterales, Family is Asteraceae, the Genus is Taraxacum, and the Species is T. officinale; your result is the dandelion.

The more time you spend classifying living things, the easier it becomes, and even in these quick examples, you probably started to see some similarities.