Biological magnification is a rising concern amongst researchers who examine the ways that chemicals and pollutants may have long-term effects on ecosystems.  In this article, we’ll dive deep into what it is and the impacts it’s already had on our environment. 

Biology researchers and students are likely familiar with the field of ecotoxicology, or the study of how chemicals and toxins affect ecosystems and their organisms.  In this field, the term biological magnification is frequently used to describe the amplified concentrations of these substances as you move up through the food chain.

Also fittingly called bioamplification or biomagnification, this process explains why harmful substances like have metals, or chemicals found in fertilizers or pesticides, present in even the largest, carnivorous predators.

In this article, we will discuss the process of biomagnification and how it works.  We will define the terminology, and then give real-life examples and case studies documenting how chemicals travel through soil, water, and smaller organisms to eventually make their way to the top of the food chain in large concentrations.  

What is Biological Magnification?

Put simply; the term biological magnification is used to describe the process by which substances used in farming or produced in industrial waste make their way into and up the food chain.

We see increased levels of these toxins and chemicals accumulating through the trophic levels of the food chain thanks to this phenomena.

Pesticides, fertilizers, and heavy metals from industrial waste are some of the most common culprits who contribute to the problem.

Typically, the materials are carried through water sources like rivers, lakes, and streams as a result of surface runoff where they are then ingested by aquatic animals like frogs or fish.  These small organisms are then preyed upon by predators higher up in the food chain, like birds, larger fish, or animals, which is how these same substances make their way into their body.

Many of these toxins and chemicals are fat soluble and get stored in their internal organs or fat tissue.  This results in an accumulation of the substance over time and in greater concentrations the higher up the food chain you go.  This phenomenon is called food chain energetics.

Although biomagnification doesn’t always have a direct effect on living organisms, long-term exposure to harmful chemicals may result in unpleasant and irreversible side effects that could threaten a species.

Biological Magnification vs. Bioaccumulation

It’s important to note that there is a significant difference between biomagnification and bioaccumulation.  Although some may use the words interchangeably, they actually describe different scenarios in an organism.

Biological magnification specifically refers to increasing concentration of materials in each higher link in the food chain.  However, bioaccumulation examines the increased presence of a particular substance inside a single organism.

While the two processes may be interconnected, for the purpose of this article it’s important to differentiate the terminology to understand the real-life examples and practice.

Examples of Biological Magnification

There are numerous, well-documented examples of biomagnification where researchers find high concentrations of chemicals in apex predators.  Many of these studies also demonstrate the potential negative consequences of this build up over time. Here are a few examples.

Bald Eagles

During World War II troops faced a plethora of health issues, including outbreaks of malaria, body lice, typhus and bubonic plague spreading through mosquito bites at encampments throughout the world.

DDT is a pesticide that was developed to kill these biting bugs to help control the spread of these diseases, and following the war had agricultural applications.  Farmers used the product on their crops to control pests, and it was both popular and widespread thanks to its low cost and easy application.

It was approved as being safe and effective by the EPA at the time because there did not appear to be any harmful side effects of ingesting the chemical in animals or humans.  However, this did not take into account the possibility of biomagnification. 

DDT doesn’t break down over short periods of time in the environment and is a substance that gets stored in the fatty tissues of animals who consume it.  This became particularly problematic for bald eagles.

A predator near the top of the food chain, bald eagles were consuming large quantities of fish who had been affected by the chemical.  Runoffs from farms hit the waterways, and DDT infiltrated aquatic plants and animal life, and the eagles ingested the chemical with each meal they ate.

Over time, the chemical disrupted their ability to lay eggs with strong shells, causing the bald eagle population to decrease to the point of near extinction.  In 1940, Congress stepped in to pass an act to protect the species, but DDT wasn’t banned until 1972.

It wasn’t just species of eagles affected.  Other predator birds like brown pelicans and peregrine falcons saw the same side effects.  The thinning off the eggshells made incubation and hatching near impossible and also threatened these bird populations.

Fish and Pregnancy

Another notable example of biomagnification is in predator fish.  Species like Shark, Swordfish, Orange Roughy, Tuna, King Mackerel, or Tilefish contain proportionally larger levels of toxic mercury than smaller fish and shellfish.

In fact, the levels are so high that the FDA advises that pregnant women avoid consuming these species for fear of exposing developing fetuses to levels that may cause nerve damage.

How does this toxicity occur?  Mercury is introduced into the ecosystem in one of two ways.  As a naturally occurring element, it can leach from rocks and volcanoes into our water supply over time, but those natural changes are not likely to significantly impact the environment.

However, when you take the natural occurrences and combine them with human contributions through coal-burning power plants which impact the air, rain, soil, and water around these facilities, the mercury levels rise drastically.

As we now know, once an element enters the water supply, it’s inevitable that it gets ingested by aquatic life at every level of the food chain.  When plankton and small crustaceans that make up the majority of the diet of the larger, predatory fish have moderate levels, then the species who eat them will have a compounded effect.

For example, according to the FDA, the average amount of mercury found in a serving of scallops is 0.003 parts per million.  Lobsters, one of the main predators of the scallop have a concentration of 0.107 parts per million.  

Monkfish love dining on lobster, and have an average of 0.161 parts per million of mercury in their system, and shark and swordfish at 0.979 and 0.995 parts per million respectively regularly dine on monkfish.

In this example, it’s easy to see how quickly the effects compound and how concentrated they become with only four steps up the food chain ladder.

What Causes Biological Magnification?

Although biomagnification is a natural phenomenon that happens in all organisms, the instances where it is worrisome are largely due to anthropogenic factors.  Materials that humans introduce into the environment can cause unexpected and hazardous side effects and typically fall into one of the following subcategories.

Organic Contaminants

We live in an age where the word organic is closely correlated with natural and healthy, but too much of anything could be bad.  Organic elements like phosphorus, nitrogen, and carbon are necessary for survival, but if they appear in excessive quantities in ecosystems, they may cause eutrophication.

Eutrophication is a phenomenon when an organism that thrives in these conditions, like algae, for example, experience exponential growth and suddenly have an overwhelming population.  This can then disrupt the ecosystem and kill off other organisms because there aren’t enough resources, like oxygen, to go around.

Waste

Waste produced from manufacturing plants, factories, and other industrial enterprises can release waste and toxins into the air and water that contribute to the problem. 

Agricultural and Industrial

Chemicals introduced into the environment from inorganic pesticides, fungicides, fertilizers and herbicides that mix with our natural water sources due to runoff when it rains release toxic elements as well.

Plastic Pollution

Not only does plastic physically impact our environment, often ending up in our oceans and disrupting marine ecosystems, but it can also leach toxic chemicals into water too.

For example, Bisphenol A, or BPA, has made headlines recently as a substance that can produce a range of health conditions in humans that is used in making plastic water bottles.  It is one of the leading chemical pollutants in the environment.

Heavy Meals

As we discussed in our earlier case study, heavy metals that enter our water sources can wreak havoc on the ecosystem.  Mining activities are sometimes at fault for releasing deposits that can pollute aquatic plants and contaminate water sources with elements like zinc or cobalt.  

Potential Negative Effects of Biological Magnification

DDT and mercury aren’t the only hazardous substances that have the potential to biomagnify.  Substances like polychlorinated biphenyls (PCB’s) that can impair reproductive systems, heavy metals, polynuclear aromatic hydrocarbons which are a known carcinogenic, cyanide, and selenium have been extensively studied and proven to have similar outcomes.

There are dozens of potential adverse effects to our environment, including but not limited to:

• Reproductive implications for marine and other animal life
• Killing coral reef ecosystems
• Disrupting the natural food chain as species die off

There is also a significant risk of health impacts on humans who consume many of the organisms affected by this process.  They include an increased risk of the following:

• Cancer
• Kidney failure
• Liver disease
• Birth defects
• Brain damage
• Respiratory disorders
• Heart disease

Final Thoughts

Bioamplification isn’t a new phenomenon, but the humans have introduced pollutants to the environment that makes it a threat to the ecosystem and our food sources.  Understanding how and why it occurs is the first step to combating the problem and preventing the destruction over time.

Conversations and advocacy for sustainability need to continue to ensure the long-term health of our environment.

How much do you know about cell parts? Can you list the differences between plant and animal cells? Here are the main differences you need to know about between these two cell types. We have also found some study guides to help you go further.

Plant and animal cells have many similarities, including shared organelles. However, these cells differ in size and structure. They also use a different mechanism for respiration. Here is what you need to know about animal and plant cell parts.

The Main Differences Between Plant And Animal Cells

The most noticeable difference between plant and animal cells is the size. An animal cell will typically range between 10 and 30 micrometers in length, while a plant cell can reach 100 micrometers in length.

Plant cells are larger because they contain vacuoles that store water. Animal cells also have vacuoles, but these organelles aren’t used to store water.

The cell wall is another important difference. Animal cells are protected by a cell membrane. Plant cells also have a membrane, but there is an outer layer made of cellulose. This outer layer is called the cell wall since it is rigid.

The rigid cell wall helps shape plant cells. These cells typically have a rectangular or cube shape. There is far less variety in the shapes of plant cells compared to animal cells. Animal cells have more varied shapes and have irregular shapes.

The mechanism used for growth is also different. Animal cell growth is achieved by producing new cells while plant cells grow by increasing their size. This is achieved by storing more water in the vacuoles of a cell.

Energy is stored differently. Animal cells store energy in the form of complex carbohydrate glycogen while plant cells store energy in the form of starch.

Plant cells can produce more amino acids than animal cells. There are 20 different amino acids cells used to produce proteins. Animal cells can typically produce 10 of these amino acids and will need to obtain the rest from nutrients that come from the animal’s diet while plants can synthesize 20 amino acids.

Different Organelles

There are a few different cell parts that are unique to animal and plant cells. The core organelles such as the nucleus are shared by both cell types.

The centrioles are organelles that organize and structure the microtubules during the process of cell division. Animal cells have centrioles while plant cells don’t.

The primary cilium isn’t present in plant cells. Animal cells have a primary cilium to detect external stimuli, and some animal cells have more cilium to make the cell move.

Plant cells need to digest lipids, which is why they have organelles known as glyoxysomes. These cell parts aren’t found in animal cells.

Animal cells rely on lysosomes for digesting macromolecules. Lysosomes can digest old organelles, viruses, bacteria, and nutrients. The vacuoles have a similar purpose in plant cells.

The chloroplasts are another major difference between plant and animal cells. These cell parts play a crucial part in the photosynthesis process that plant cells are known for. These organelles transform light into energy the cell can use.

Even though vacuoles are present in both cell types, these organelles are different. Animal cells have small vacuoles while plant cells have vacuoles that can take up as much as 90 percent of a cell’s volume. Vacuoles are used for storing nutrients in animal cells, while they store water in plant cells.

Different Processes

The differences in structure and organelles mean that some processes happen differently between plant and animal cells.

Cell division is slightly different. With animal cells, the cytoplasm and the cell membrane is pinched in half until the cell completely divides. With plant cells, a plate is constructed to divide the cell in two.

Plant and animal cells communicate differently. There are pores called plasmodesmata in the wall of a plant cell. Molecules and communication signals can exit the cell via these pores.

Animal cells don’t have plasmodesmata. Instead, there are proteins embedded in the outer membrane of the cell that let nutrients and chemicals in and out of the cell. These proteins can bind with a hormone or another transmitter to communicate a signal.

There are some similarities in cell respiration. Both cell types will break down glucose molecules to produce carbon dioxide, water, and ATP. The main difference is that animal cells absorb glucose as a nutrient while plant cells produce glucose via photosynthesis.

Study Guides

You can learn more about plant and animal cells with these study guides. We have found the best resources for learning about cells and organelles and have organized them.

The Basics

You can get started with this table that sums up the main differences between plant and animal cells. This study guide is made for younger students, but this is a good way to brush up on what you already know about cells.

You can then move on to this more comprehensive study guide about the different organelles. You should print this study guide and use it as a reminder of what different organelles do. If you have already studied organelles in class, this study guide will help you keep this knowledge fresh in your mind. It’s a great starting point if you are new to learning about the different parts of a cell.

We have found this helpful quiz you can use to assess how much you know about organelles and their functions. Don’t move on to other topics until you can answer all these questions.

We also like this video about organelles. If you are more of a visual learner, this video should be a helpful resource you can go back to and go over the different organelles and their functions.

Plant Vs. Animal Cells

If you want to explore the differences between plant and animal cells, the Khan Academy has an excellent article on this topic. The material is designed for high school students, but it is a very comprehensive review of the differences between these cell types.

We have found another helpful resource on this topic. We like this study guide because it organizes the information by organelle. This is the best resource for studying how cell structures and parts differ between plant and animal cells.

Eukaryotic And Prokaryotic Cells

We have been focusing on eukaryotes, but this study guide is an excellent resource if you need a reminder of the difference between eukaryotic and prokaryotic cells.

Test Your Knowledge

We have found this online activity where you can label the different parts of an animal cell. This activity requires you to label the different parts of a plant cell.

Try to briefly explain what the different organelles do as you label them. Take the time to practice with these activities because you are likely to have to label similar diagrams in tests.

Going Further

There are different topics that we briefly mentioned to point out the differences between plant and animal cells. You can use these study guides to explore these topics further.

Note that these study guides are more advanced and are designed for college-level students. You should still be able to follow these study guides if you are in an AP class or if you are curious to learn more about biology.

You can start learning about cell cycle with this study guide. It will help you gain a better understanding of how the functions of the different organelle help cells grow and reproduce.

This study guide is about cell division. It is best to start learning about the entire cell cycle and then focus on the process of cell division.

We talked about cell respiration and photosynthesis. You can assess how much you know about cell respiration by going over these questions and answering them as best as you can.

The Khan Academy has a very comprehensive course on the topic of cell respiration. The information is well-structured, and you will be able to take quizzes as you go through the content to see how much you have learned. You can explore the introduction section by itself to get an overview of how cell respiration works without going into details and looking at the chemical aspect of this process.

This overview of photosynthesis is very comprehensive and will help you gain a better understanding of this process.

Flashcards And Quizzes

Flashcards are a great way to assess how much you know and to review the information you have already studied. We have found different sets of flashcards and quizzes you can use to test your knowledge, expand your vocabulary, and make sure you have understood all the important concepts linked to cells.

Here are the best flashcards and quizzes we found:

• These flashcards go over all the organelles you will find in animal cells.
• These flashcards list all the plant cell organelles.
• Use these flashcards to assess how much you know about cell respiration.
• These flashcards cover cell respiration and photosynthesis.
• Use these flashcards to test your knowledge about cell division.

The key to learning about plant and animal cells is to organize your study sessions. You could have some sessions dedicated to learning about the different organelles or decide to focus on a specific type of cell. You can then move on to learning about different mechanisms and processes like respiration and division.

The Punnett square worksheet is a great teaching tool for genetics. This worksheet helps students get an idea of the different possible combinations for genetic traits and helps them calculate how likely each combination is. Here are some ideas for using the Punnett square in your classroom.

The Punnett square is a diagram used to make sense out of genetics and inheritance. The purpose of this diagram is to show the different possible combinations of alleles. This is a useful tool you can use to teach biology and probabilities regardless of the level of your students. Here are a few ideas to use the Punnett square in your classroom.

Understanding Dominant And Recessive Alleles

You should talk about genetics and alleles before introducing the Punnett square worksheet in your classroom. Students should ideally also have a good understanding of how to calculate probabilities.

Students should be familiar with genes and understand that genes are a unit of hereditary information while an allele is a possible sequence or variant of a gene.

You should also talk about observable genetic traits, also known as phenotypes. Students should understand that there are dominant and recessive alleles that won’t become phenotypes unless they are combined with another recessive allele. You can introduce the notion of codominant alleles with high school students.

Make sure the Punnett square activities are connected to lessons about genetics, inheritance, and alleles. You can use these activities to introduce these concepts or to help students get a more thorough understanding of genetics and probabilities.

The Punnett Square

The Punnett square is a simple diagram that shows the different possible combinations. Here is an example for the offspring of two organisms with the same Aa allele combination:

	A	a
A	AA	Aa
a	Aa	aa

 

Using this worksheet helps students see all the different possibilities and gives them an idea of which phenotype is more likely to occur.

Ten Ideas For Using The Punnett Square Worksheet In Your Classroom

Middle School

Introduce The Punnett Square With Legos

You can use Legos to introduce the Punnett square to your students. This visual approach would be ideal for an activity that you will use to introduce concepts like genetics and alleles.

You need to have Legos with two different shapes to represent the dominant and recessive alleles. Use cups or other small containers to represent the animals or plants that inherit the genetic material.

Start with two cups that contain a different combination of two Lego shapes to represent the parents. Have the students fill out the worksheet with the four possible combinations of Lego shapes.

The students can then place the four different combinations inside of four cups or small containers that represent the offspring.

This approach helps students understand the logic behind the Punnett square and gives them a visual reference you can use once you start talking about alleles.

Plant Genetics

Plants are a great example at the middle school level because you can easily identify a phenotype that students will understand, such as the color of a flower. You can even grow flowers in the classroom to illustrate the lesson.

Students can fill out a Punnett square worksheet for plant genetics. The purpose of this activity is to introduce the idea of dominant and recessive alleles and have students get used to seeing a capital letter for the dominant trait and a lowercase letter for the recessive trait.

Create a simple worksheet with four squares and ask students to write the different possible combinations. You can work with different phenotypes:

• Create a worksheet for a blue flower BB and a blue flower Bb.
• Create a worksheet for a blue flower Bb and a white flower bb.
• Create a worksheet for a tall plant TT and a tall plant Tt.
• Create a worksheet for a tall plant Tt and a small plant tt.

You can then ask students to identify the number of possible combinations and to calculate the probability of a flower being blue or of a plant being tall. You can also have students draw what the plants will look like.

High School

You can introduce advanced ideas at the high school level and connect the Punnett square with more real-life examples. You should introduce concepts like homozygous genes, heterozygous genes, or mutations.

You can also focus on probabilities and have students use a worksheet to calculate the probability of a trait appearing in offspring.

Predicted Outcome And Actual Outcome

Introduce the idea that the predicted outcome of a Punnett square doesn’t always reflect what happens in real life. Students should be aware that these worksheets will show how likely an allele combination is.

Have students use a Punnett square worksheet to predict the outcome of a coin flip or another random event. Once the worksheet is filled out, have students flip a coin and compare the outcome with what the Punnett square predicted.

Guessing The Parents’ Allele Combination

Provide students with different allele combination for the offspring and tell them how frequent each combination is.

Have them use the Punnett square to find the allele combinations of the parents. This is an activity that only takes a few minutes to complete, but it is a great way to brush up on how the Punnett square works and to make sure that students have a solid understanding of inheritance.

Bear Fur Color

You can work with phenotypes that are observable in animals and introduce the idea that there are different possible allele combinations for the same phenotype.

The brown bear fur color is an excellent example since a bear can have BB or Bb alleles and have brown fur. On the other hand, only a bear with a bb allele combination will have black fur.

Have your students use the Punnett square to calculate the probability of offspring having brown or black fur. This problem encourages students to create more complex tables since the bear parents can either have the BB or Bb allele combination.

Eye Color

Predicting eye color is another interesting activity you can introduce at the high school level. Start by making a list of the different possible allele combinations for each eye color.

You can have students calculate the probability of their eye color based on the eye color of their parents, or have students determine the allele combinations of two parents based on the phenotypes of their children.

Eye color is more complex than other phenotypes and gives students an opportunity to create more advanced worksheets that reflect the different possible allele combinations of the parents based on their phenotypes.

You can make things more complicated and combine eye color with hair color.

Research

Have students research different genetic traits and create a presentation on how these traits are inherited. You can have students work in groups and assign a trait to each group.

Students will have to define the trait you assigned to them, explain how it is inherited, and create different Punnett squares that show how the trait can be inherited or skip a generation.

Here are a few examples:

• A specific hair color.
• A specific eye color.
• Tongue rolling.
• Freckles.
• Free or attached earlobes.

This project will help students understand how complex genetic inheritance is and will also help them connect what they learned in class with real-world examples.

AP Level

Cat Coat Genetics

Students can look at pictures of cats and predict what the offspring will look like with Punnett squares. This is similar to the bear fur activity, but cat coat genetics are more complex.

Students will have to work with genotypes that affect hair length as well as color. Here are a few facts to help you get started with planning this activity:

• A cat with short hair will have an LL or Ll genotype.
• A cat with long hair will have an ll genotype.
• A cat that is entirely white can have a WW or Ww genotype. A cat with white fur and some colored hair has a ww genotype.
• White cats can have a W allele and another allele for a dense pigment or piebald spotting.
• There is a gene for dense pigment. A black, brown, or orange cat will have a DD or Dd allele combination.
• A cat with gray, cream or light brown fur will have a dd allele combination.
• Piebald cats with the SS and Ss allele combination have some white hair, while piebald cats with no white hair have the ss genotype.

Genetic Disorders

You can combine the Punnett square with topics like genetic disorders. Studying how sickle cell anemia is inherited could be an interesting project for AP level students.

You can have students create a worksheet to determine the probability of a child inheriting sickle cell anemia based on the parent’s allele combinations.

Have Students Create A Species

Have students design a species from scratch to test their understanding of genetic rules. Ask them to make a list of dominant and recessive traits. Determine how many traits students will have to work with depending on how much time you want them to spend on this project.

Creating a species and determining how common some genetic traits are going to be is a great way to make sure students have a solid understanding of the Punnett square. You can have students create illustrations for the different genetic combinations.

You can go further and ask students to create genetic traits for an imaginary species, determine which traits are dominant and recessive, and ask them to create problems that other students will have to solve.