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Embracing Motherhood Why Leaves Change Color in the Fall

Why Do Leaves Change Color in the Fall?

A few years ago when we were playing outside in the fall leaves, Ruby asked me, “Why do the leaves change color?” So I started telling her about how the earth tilts in the fall making us get less sunlight which affects the amount of sun that the plant gets from photosynthesis and so on, but truth be told, her attention had wandered to something else before I could even finish my explanation. So we gathered a variety of multi-colored leaves, and I made a large mural on our wall to teach her more about photosynthesis and its role in the leaves changing color, but still, the answer was too complex.

Teaching Photosynthesis Wall Art

Teaching Photosynthesis Wall Art

I continued learning more and more about photosynthesis all the while thinking of the Einstein quote,

“If you can’t explain it simply, you don’t understand it well enough.”

After watching countless videos (like this amazing one), reading numerous articles (like this very scientific one), and making a large photosynthesis mural in our new house, it finally dawned on me when I was invited to teach an art lesson in my daughter Ruby’s 1st grade class.

Photosynthesis Mural

Photosynthesis Mural

For the art lesson, I chose to have the students make trees out of multi-colored leaves. I also wanted to do a mini-lesson about, you guessed it, why leaves change color! As I was thinking about where to start, this other Einstein quote was on my mind,

“Everything should be made as simple as possible, but not simpler”

It finally dawned on me that I needed to start with chlorophyll.

Chlorophyll

Chlorophyll

Chlorophyll is what makes leaves green, it is basically the heart of photosynthesis, and the absence of it in the fall is what makes the leaves change color. Eureka! This was it!

Chloroplasts

The hexagon shapes are the plant cell walls. The little circles inside are chloroplasts. Cholorophyll is what makes chloroplasts green.

So I began my mini-lesson by showing the students one green leaf. I explained how chlorophyll is what makes leaves green. They all said the word chlorophyll, and I showed them my chlorophyll poster. (Click here to see a really cool video of chloroplasts moving to music.)

Then, I explained how chlorophyll was a part of photosynthesis. Now, I know that photosynthesis is a complex system that even I struggle to fully understand, but I believe that children learn things in layers. By really understanding chlorophyll and then being introduced to photosynthesis, they are creating new pathways in their brains that will continue to be strengthened over time through repeated exposure.

Why Leaves Change Color

Why Leaves Change Color

I had all of the kids take a deep breath in and I asked them what they just breathed in. “Oxygen,” explained one student. I then had them exhale and asked them what they just breathed out. Ruby was the only one who could tell me carbon dioxide. (She had an unfair advantage!)

I then explained how we breathe out carbon dioxide which is just perfect for trees because even though they don’t breath, they need to take in carbon dioxide to make their own food. As I explained the rest of photosynthesis and how trees take in carbon dioxide, water, and light (which is absorbed by the chlorophyll) which they use to make glucose (also known as sugar or sap) and then give off oxygen as a waste product (which is perfect for us!), I knew that I was going over their heads. I even told them, “I know that photosynthesis seems like a really big idea for a first grader to learn about, and I know that it seems like a confusing big new word, but the more you hear about it, the more you will understand it. All I want you to really remember right now though, is chlorophyll.”

Then I talked about how in the fall when the days are shorter and there’s not as much water, the trees don’t make as much chlorophyll and photosynthesis slows down until it completely stops. Chlorophyll is what makes the leaves green and as it goes away, we start to see some of the colors like orange and yellow that were in the leaf all along. The leaves that turn red and purple are from sugars that get left behind.

As the tree gets ready to hibernate for the winter, the veins in the leaves that carry the sap into the tree start to close by forming a separation layer. When the leaves finally detach and fall to the ground, they start to decay and turn brown.

Then I showed the children how to make their tree art. As I passed out the green leaves, I had them look at the green color made from chlorophyll, feel the veins that carry the sap from the leaves into the tree, and look at the stem where the separation layer is formed. As I passed out the orange and yellow leaves, I explained how these colors were already in the leaves and once the chlorophyll left, we could finally see them. When I passed out the red leaves, I explained how some leaves leave sugar behind, and it turns the leaves red. (Warm sunny days and cool, crisp, but not freezing nights make the most sugar get trapped in the leaf as its vein closes and makes the most brilliant of red leaves.) Finally, we put some brown leaves on the ground, and I explained that they are brown because they are decaying.

The students that finished early were able to do some leaf rubbings with crayons. This is an excellent way to really see all of the veins in the leaves.

IMG_2306

At the end of the lesson, I brought all of the children together again and asked them, “So why do leaves change color in the fall?” Hands shot up all over the place and kids told me how it was because of chlorophyll. We all said chlorophyll again together, and I told them to remember that chlorophyll is what makes leaves green, that chlorophyll helps the leaves absorb light during photosynthesis, and that in the fall without as much light and without chlorophyll, the leaves change color.

In a Nutshell

Chlorophyll is a green pigment that allows plants to absorb light during photosynthesis. It is what makes leaves green. In the fall, when there isn’t as much sunshine and water, the leaves don’t produce as much chlorophyll, and so they lose their green color. The yellow (from xanthophylls pigments) and orange colors (from carotenoid pigments) were there all the time in small amounts, we just didn’t see them because they were covered up by the green chlorophyll. The red and purple colors we see are made from sugars that were left behind in the leaf (called anthocyanins). When leaves fall from the trees and start to decay, they turn brown (tannins are the last pigments to decay and they are brown). (Source)

In Conclusion

So now, when the next one of my children asks, “Why do the leaves change color?” I will simply explain that it’s because of the chlorophyll. When I have their attention and curiosity, I will explain more and more layer upon layer, lesson upon lesson, day by day until their curiosities are fully satiated and we are ready to move on to the next question!

Further Resources

  • Fall Leaf Art Projects – by me!
  • Autumn Leaves and Fall Foliage: Why Do Fall Leaves Change Color? by Science Made Simple (This article gives two explanations, one with a really simple explanation and one with a more complex explanation.)
  • The Science of Color in Autumn Leaves by the United States National Arboretum (A very comprehensive explanation that I used as a resource for this article.)
  • Why Leaves Change Color by the USDA Forest Service (Another very comprehensive article that I used as a resource.)
  • Why Do Leaves Change Color in the Fall? YouTube video by Super Scienced (A 2:43 minute video that provides a simple and accurate explanation with cartoon animation that also explains the difference between coniferous and deciduous trees.)
  • Why Do Trees Shed Their Leaves In Autumn Season? YouTube video by T-Series Tree Hut (This is an excellent 2:43 minute video. All of the videos in this series do an amazing job of answering typical questions posed by children in a way that includes the scientific information presented in a simple and easy to understand way with entertaining cartoon graphics. The speaker has an accent and there are some translation mistakes, but it’s still the best thing out there and my kids love them!)
Embracing Motherhood How Children's Brains are Wired for Learning

How Children’s Brains are Wired for Learning

As a former elementary school teacher and now mother of four young children, I have always been fascinated by the brain and how it works. One of the most interesting things I’ve learned and observed with my own children is the how capable they are of learning at a very very young age with just little nudges in the right direction when they are ready (i.e. teaching in the zone of proximal development).

We often think of children being ready to “learn” when they are old enough for formal schooling, but by the time children are old enough for kindergarten, the frameworks of their brains are pretty much set for life. The crucial window of brain development begins at about 6 months and peaks at 2-3 years of age. I think this is a window that is largely ignored, but if can recognize its importance and provide stimulating experiences during this golden opportunity of time, we can help our children to develop their best brains.

Romanian Orphans

Before we start getting into some of the nitty gritty about how the brain works, I wanted to point out what happens at the other end of the spectrum when it doesn’t work. In this example, you’ll see what happens to childrens’ brains when they are ignored, neglected, abandoned, and mistreated.

In his NPR article, “Orphans’ Lonely Beginnings Reveal How Parents Shape A Child’s Brain“, Jon Hamilton explains how when the corrupt Romanian government was overthrown in 1989, the world was shocked to learn about the more than 100,000 children in government care that were left alone in their cribs, wallowing in their own filth, and with nothing but the white ceiling to stare at and the cries of the other babies to keep them company…for days and days and days. There was no one there to soothe their cries, no one there to hold them and give them affection, and no one there to talk to them and help them to interact with their environment.  The result was stunted growth and a range of social and emotional problems.

The odd behaviors, language delays, and range of other symptoms suggested problems with brain development, and so researchers began studying the children using a technology known as electroencephalography (EEG), which measures electrical activity in the brain. What they found were disturbingly low levels of brain activity. As the children grew, there were able to conduct MRIs on them, and it showed that their brains were actually smaller and that they had a reduction in grey and white matter. (The grey matter is near the outer part of the brain and is mostly all of the neurons bunched together. The white matter is on the inner part of the brain and is mostly the myelinated axons that connect the neurons together.)

fresh brain sliced open to show gray matter and white matter

White Matter and Grey Matter – Photo Credit: Wikimedia Commons (2007) Suseno

In another experiment conducted after the orphaned children had been adopted, it showed that their brains could not discriminate the face of a stranger from the face of their adoptive mother. Because their brains were not able to identify with a loving caregiver at a young age, that part of their brain wasn’t developed, and then when someone was ready to give them love, they didn’t know how to accept it.  This is called reactive detachment disorder, and with lots of patience and love, it is possible to rewire the brain, unfortunately it’s just not very probable. Today, the system in Romania is still corrupt, and there are currently 70,000 children waiting for adoption. 🙁

How the Brain Works

Okay, so now that we’ve established that the environment is a crucial factor in brain development, let’s take a look at why that it. I love this video clip below because it shows how the brain is an interconnected web of not just the neurons, but the connections (synapses) that are between them.

Neural_signaling-human_brain

How the Brain Transmits Signals – Photo Credit: Wikimedia Commons (2013) Gif created from Inside the Brain: Unraveling the Mystery of Alzheimer’s Disease

Understanding Neurons

When you look at an individual neuron, you’ll notice that it’s made up of three main parts.

parts of a neuron

Diagram of a Neuron – Photo Credit: Wikimedia Commons (2005)

  1. Cell Body: This is the main part of the neuron, It’s where the nucleus is and it directs all activities. This is what makes up most of the gray matter in the brain.
  2. Dendrites: These short fibers sticking out of the cell body receive messages from other neurons. If you were to zoom in close to look at the tip of a dendrite, you would see that it never actually touches another neuron, but connects via a synapse (more on this in a minute).
  3. Axon: This long single fiber carries messages away from the cell body to other cells. It might send a message to a nearby neuron or to a far away muscle fiber. Axons that are used over and over get coated with a myelin sheath which helps messages to transmit faster and is what makes up the white matter in the brain (more on this in a minute too).

Synapses are Where It’s At

Neurons on their own can’t really do much, but when they are connected, that is what creates brain activity. When neurons connect, they actually don’t ever touch each other, but instead communicate across a gap called a synapse. One single neuron can have anywhere from hundreds to thousands of synapses.

Chemical_synapse_schema_cropped

How Synapses Work – Wikimedia Commons (2009) US National Institutes of Health, National Institute on Aging created original

How Synapses Work:

  1. First, A neuron fires an electrochemical signal from its cell body that travels through the axon and out to the tip of the dendrites.
  2. From here, neurotransmitters cross the synaptic cleft and are met with receptors on the other side that welcome it to the next neuron.
  3. This happens from one neuron to the next in a sort of a domino effect.

Synapses As We Age

We are born with about 100 billion neurons, which is pretty much the same number of the neurons the brain will ever have. The number of synapses, however, is a number that does change over time. In the first decade of life, a child’s brain can form trillions of synapses. The number of synapses peaks at about 2-3 years of age. (source)

When children are born, they have about 2,500 synapses per neuron and by age 2 or 3, they can have about 15,000 synapses! (source) From the time a child is about 6 months old until they are about 2-3 years of age, there is a SYNAPTIC EXPLOSION!!! Because children are not very mobile or explicitly expressive about what they are learning and what they need in addition to the fact that parents are often overwhelmed with sleep issues, teething, and other parenting concerns (With four children 5 and under, I am WELL aware of this! :), I feel like the importance of this learning period is often overlooked and undervalued.

There are an ENORMOUS amount of connections that are being formed at 6 months and 2 years of age. Click here to see a really cool chart showing the synaptic explosion happening between 6 months and 2 years.

Experiences Make Neural Connections

Genes provide the basic framework in the brain, but experiences determine which neurons are used and which pathways are formed and strengthened. When children are very young, their brains are very “plastic” (malleable), meaning that they are easily able to learn something new through experience, but this changes over time and the brain becomes less “plastic” and it becomes more challenging to learn something new from experience.

Click here to see a really cool graph that shows how when we are 2, experiences are easily able to shape the brain, but the ease with which this happens declines with age. When we reach our 20s, we’re kind of at an even plateau, and then as we age from there it gets progressively harder for the brain to change from experiences.

The reason why it’s easier to learn something new at a young age is because the brain is like a blank slate. This tabula rasa allows for children to shape their brains about their environment and experiences, but as we age and our brains become more established, learning something new requires rerouting the information through existing pathways rather than simply creating new ones.

Myelination Speeds Up Connections

Neuron

Structure of a Neuron – Photo Credit: Wikimedia Commons (2011)

It wasn’t until fairly recently that we realized the true importance of myelination. Myelination can be seen as the white matter in the brain and is comprised mostly of the fatty substance called myelin that coats the axons. This myelin sheath is made out of schwann cells that over time and with continued use wrap around the axon like a spiral. (Check out a cool video here to see this in action.)

The myelin sheath serves two functions:

  1. It protects the axon so that it doesn’t lose the electrical impulse.
  2. It increases the speed at which the electrical impulse travels. In an unmyelinated axon, the electrical impulse travels in a wave, but in a myelinated axon, the electrical impulse sorts of hops through it.

The first time a child tries to walk, the pathway hasn’t been myelinated yet, so he only takes a few shaky steps and then falls down. But over a long period of time and lots and lots and lots of repetition, he will take two steps, and then three, and before you know it, he’ll be running everywhere! The pathway that controls walking becomes myelinated so that he doesn’t even need to think about it anymore, it just happens. It’s why they say, “You only need to learn how to ride a bike once.”

Whatever experiences a child has over and over and over again will determine which pathways will become myelinated. The myelinated pathways are the ones that will remain, the rest will become pruned away.

Synaptic Pruning

Much like a painter likes to work with more paint than is needed for the job and a builder likes to construct with more materials than is needed for the project, a child’s brain is provided with far more neurons and synapses than are functionally needed and/or preferred. Synaptic pruning is the process by which these extra neurons and synapses are eliminated. This is what increases the overall efficiency of the neural network.

The entire process begins to happen at a significant and rapid rate when a child is approximately 3 years old. By the time, a child is 10, most of the synaptic pruning has occurred. In fact, when a child is 10, 50% of the synapses that were present at 2 years of age have been eliminated.

We talked about the synaptic explosion earlier, but now let’s take a look at what happens when the synapses are pruned. (Click here to see a graph that I wish I could include, if only it were on Wikimedia Commons!) When you look at the brain of a 2 year old, it kind of looks like a jumbled mess compared to the brain of a 4 year old. In the 4 year old’s brain, there is more organization and cohesion. The neurons that exist and the pathways that have been used over and over again to connect them are making the brain more efficient. This continues to be more obvious in the 6 year old’s brain.

By the time a child is 10, the framework for the brain is pretty much set, and the brain continues to focus on specialization. The adult brain is similar to the 6 year old’s brain but with fewer, yet stronger, neurons and connections. (Click here to see another image I wish that I could include!)

In one of my education classes, my professor explained it by saying that the brain is like a giant house with hundreds of rooms. Whatever rooms the child goes into over and over and over again, those are the rooms that will remain, and the rooms that are unused will become closed off and die.

So what rooms does your child want to go into over and over again? What experiences and opportunities will you help to provide repetitiously? I believe that every child is different and that every child’s brain should be given the freedom and opportunity to develop as it is meant to. For me as a parent, that means that I provide multiple opportunities for all of my children to achieve this goal.

In Conclusion

This “use it or lose it” concept is fascinating because it gives so much more meaning to the younger formative years as the brain is forming. People assume that because little babies aren’t physically able to engage with their environment, that they are not mentally capable of it. But that’s just not true. Before babies start talking, they are immersed in language and exposed to it over and over and over again. Their brains are busy forming pathways before they even speak!

In this way, each child’s brain becomes specifically wired to adapt best to the environment that he or she is in. If the child is to grow up in a stimulating environment with lots of learning possibilities, then they need a brain that is primed and ready to thrive in that type of environment.

I think that by just being aware of how the brain functions, it can help us to better understand what is going on in the minds of our children. By providing a loving, nurturing, and stimulating environment full of lots of learning opportunities, we can help our children to develop their best possible brain.

To see how to put this information about the brain into practice, check out some of my other articles:

Resources for Further Research

Throughout this article, I’ve linked to my resources where appropriate, but I also read the following articles and watched the following videos that helped me to get a broad understanding of this topic. If you’d like to learn more about this topic, I highly recommend checking out some of these videos and articles.