Reader Favorites from 2015

It is hard to believe that 2015 is nearing an end, this year just seemed to fly by. As I prepare to turn the calendar page I thought it would be fun to share the posts that were reader favorites from this past year. I’ve made some annotations about each of the posts so that if you missed a post, you can catch the summary and jump over if you would like to read more.

Reader Favorites from 2015 @EvaVarga.netSome of these posts were not actually published in 2015, but they are reader all time favorites showing up on this year’s list. It is not surprising to me that many are from STEM Club, the homeschool science co-op I have directed the past three years.

Free Science Curriculum for Middle School I understand that budgets are tight and we have to make tough decisions about what extra-curriculars and curriculum we can afford. The best things in life are indeed free so in this post I have compiled a list of free science curriculum specifically for middle school.

modeling plate tectonicsSTEM Club: Plate Tectonics The theory of plate tectonics was first suggested by Alfred Wegener in 1915. It wasn’t widely accepted however until the 1970s as new information was obtained about the nature of the ocean floor, Earth’s magnetism, the distribution of volcanoes and earthquakes, the flow of heat from Earth’s interior, and the worldwide distribution of plant and animal fossils. This simple activity allow students to model each of the different types of interactions at plate boundaries.

STEM Club: Introduction to Body Systems  At the middle school level, students should begin to view the body as a system, in which parts do things for other parts and for the organism as a whole. I thereby developed this unit for students to understand that there are different systems within the body and that they work independently and together to form a functioning human body.

Autobiography Maps: Our Life as an Island  Creating an autobiography map is a wonderful activity with which to get to know students better. It is especially great at the beginning of the year.  They began by brainstorming important things that have happened during their lives, items or activities that represent them currently, and goals that they have for the future.

bromoblueSTEM Club: The Respiratory System The most popular and well received lesson in the Human Body Systems unit were those related to the respiratory system. I had several stations set up around the room and the kids loved each of the quick demonstrations in which they took part.

Building Toothpick Bridges: A Lesson Plan We have had an opportunity to build toothpick bridges a couple times and it is always a fun and challenging experience. This post describes our first foray into learning about bridge engineering. You might also be interested in learning more about Joseph Strauss, the engineer who designed San Francisco’s Golden Gate Bridge.

STEM Club: Scientific Classification and Dichotomous Keys Whenever I begin a life science unit, I begin with a review of scientific classification and how to use a dichotomous key. In this post I provide a couple of free printables you can use with your own students.

genealogy with kidsGenealogy With Kids Digging into the family tree gives kids a sense of connection within their families, as well as a sense of general history. It also can provide a context for understanding complex issues, such as war and immigration. Exploring genealogy together offers a practical benefit for adults as well. I share a variety of ways in which to integrate genealogy activities into your homeschool curriculum beginning with the youngest of learners.

How to Teach Middle School Science  I realize that not everyone feels comfortable teaching science – especially utilizing a hands-on approach. I have thereby compiled advice from homeschool experts – homeschool parents just like you and I – who have been teaching our own children for a number of years. They share their wisdom and advice for teaching science at home.

Introduction to Orienteering @EvaVarga.netOrienteering for Kids We love the sport of Orienteering which originated in Sweden. It is an exciting adventure sport that will get your kids running – and provides lots of great learning opportunities for homeschooling. It combines athleticism with geography, math, science, and technology.

What was your favorite post this past year? Share in the comments. 🙂

STEM Club: Let’s Get Dirty – Soil Horizons & Particle Size

Soil is the part of the ground where plants grow. Soil is a mixture of tiny particles of rock and rotting plant and animal material, with water and air between them. Soils help plants grow in two ways. First, soil holds the plants into place. Second, soil contains nutrients that plants need in order to survive. These nutrients include water, phosphorous, nitrogen, and potassium.

Over the course of the next few weeks, STEM Club will be investigating soil ecology as a part of the Year of Soils. I’ve shared a few of our past endeavors relating to soils here:

Soil Ecology Activities for Middle School

Cycles and Ecosystems {Free Printable}

Soils Support Urban Life: Rain Gardens & Composting

Soils Support Agriculture: Ideas to Integrate Writing

STEM Club: Let's Get Dirty (Soil Ecology)

Today, I share a lesson on soil horizons and particle size.

Soil Horizons

Soil particles vary greatly in size. The largest particles settle to the bottom first. The fine particles settle slowly; some are suspended indefinitely. The amount of open space between the particles has much to do with how easily water moves through the soil. This also determines how much water the soil will hold, which has a major effect on the type of plants that can grow in the soil.

STEM Club: Let's Get Dirty (Soil Ecology)

Things to look for in soil are color, texture, structure, depth, and pH. A general soil profile is made up of a litter layer, A horizon, B horizon and C horizon. A soil sampling device (pictured in the collage above) allows you to gather data on the soil makeup on any site.

Soil Particle Size

Soil scientists classify soil particles into sand, silt, and clay. Scientists use these three components and the calculated percentages on the texture triangle to determine the textural class of the soil at a given site.

A soil’s texture depends on the size of its particles and living things depend on the right texture to thrive in the soil. Every soil type is a mixture of sand (2mm – 0.05mm; feels gritty), silt (0.05 – 0.002mm; feels like flour), clay (Smaller than 0.002; feels sticky when wet), and organic matter. Squeeze some soil between your fingers. Is it crumbly? Sticky?

STEM Club: Let's Get Dirty (Soil Ecology)

Let’s Get Dirty ~ Terrestrial Soils

One of the best activities to engage kids in the study of soil ecology is the sample the soils around your home or school yard. Begin by asking the following questions:

1.  Are there different types of soil near your home?

2.  What texture class is this soil?

3.  What is the particle size make-up of this soil?

The answers generated prior to the investigation are part of your hypothesis. Record your ideas in your science notebook before you begin and give reasons. Why do you suppose the soil in your yard is predominately sand? What experience or prior knowledge do you have to help you make this statement?


  • 1 Soil probe
  • 1 Metric ruler
  • 1 Quart jar with lid
  • 1 Set index cards for diagrams


  1. Use the soil probe to collect soil cores as deep as possible from a predetermined site.
  2. Diagram and measure the depth of each layer or horizon in your sample.
  3. Fill the quart jar at least half and no more than two thirds full.
  4. Fill the rest of the jar with water, seal tightly and shake vigorously for 10 minutes. Let the jar stand for 24 hrs.
  5. The next day, mark the soil layers of each sample on an index card placed behind the bottle. Mark the top of the soil and the points where the layers change. Calculate the percent of sand, silt and clay in your sample. To do this, measure the following marks you made on the card: entire height, sand (bottom) layer, silt (middle) layer, and clay (top) layer. Then take the height of each layer by the total height and multiple by 100. Record the figures on the data sheet.

STEM Club: Let's Get Dirty (Soil Ecology)
Analysis of Results

  1. At which site was the soil the most sandy? silty? mostly clay?
  2. Do you think that this is a trend and would be found at other sites? Explain.
  3. What are some factors that may change the results of this experiment? Explain.


  1. Did you achieve your hypothesis? Explain.
  2. What did you learn by doing this exercise?
  3. Do you think the soil will be the same at other sites (park, forest, meadow, near the shore of a lake or river, etc.)? Design an inquiry project to learn more.

STEM Club: Cycles and Ecosystems

Every spring, when the weather is still yet cool, I like to take our STEM Club outdoors for more in-depth, hands-on ecology lessons. This year, to align with the International Year of Soils, we are focusing on soil ecology.

STEM Club: Cycles & Ecosystems w/free printable @EvaVarga.netAs I begin each ecology study, we review the cycles of energy and nutrients. Ecosystems are characterized by different cycles that enable organisms to survive. Plants and animals interact with each other and with their environment through these important ecosystem cycles.

  • Energy Cycle
  • Carbon and Oxygen Cycle
  • Nitrogen Cycle
  • Water Cycle
  • Disturbance Cycle

The Energy Cycle

An ecosystem is a type of community in which all of the plants and animals that live in it either feed off each other or depend upon one another in some way. Just as people interact and depend on each other in our communities. In each ecosystem, there are different feeding levels called trophic levels: primary producers (or plants) that convert energy from the sun through photosynthesis, primary consumers (herbivores), secondary consumers (animals that eat the primary consumers), tertiary consumers (animals that each both primary and secondary consumers), and decomposers that break down dead or dying matter into nutrients that can be used again by producers.

The Carbon and Oxygen Cycle

Another important cycle in an ecosystem is the carbon and oxygen cycle. Each of these elements is needed in order for plants and animals to live. Plants take in carbon dioxide during the process of photosynthesis. They use the carbon from carbon dioxide to make food which provides matter and energy to make new plant cells. During respiration plants take in carbon dioxide, a gas they need to live, and release oxygen. Animals breathe in oxygen, a gas they need to live, and release carbon dioxide. Dead plants and animals release carbon dioxide during the decaying process. The carbon is stored as fossil fuels that include coal, gas, and oil.

The Nitrogen Cycle

Nitrogen is a gas that makes up about 78% of the air we breathe. It is an important part of proteins and other plant and animal matter. Plants and animals cannot use nitrogen directly from the air. The nitrogen must be changed into a form that plant roots can take up and use. Certain bacteria, like lichen, are able to take nitrogen from the air and change it into a form that plants can use. The process of changing nitrogen into a form that plants can use is called nitrogen fixation. The bacteria break down the nitrogen containing tissues of dead plants and animals and change them into nitrates. Plants absorb the nitrates through their roots and release nitrogen gas back into the air.

The Water Cycle

Organisms need water to survive. The water cycle is very important in an ecosystem. The water cycle is the movement of water from the ocean to the atmosphere to land and back to the ocean. An ecosystem, especially a wetland or forest, is essential to the water cycle because it stores, releases, and filters the water as it passes through the system.

There are three steps to the water cycle:
  1. Evaporation occurs when the sun heats the water in soil, rivers, lakes, and oceans, causing it to evaporate and become water vapor, which is a gas.
  2. Condensation occurs when water vapor rises, cools, and condenses to form tiny water droplets or ice crystals in clouds.
  3. Precipitation occurs when the water falls back to earth as rain, snow, or other precipitation. Most water returns to the sea or sinks into underground water sources.

The Disturbance Cycle

A regular cycle of events including fires, floods, landslides, and storms keep every ecosystem in a constant state of change and adaptation. Although the disturbance cycle can cause  disruption, some species depend on this cycle for survival and reproduction. For example, some forests depend on fire for reproduction. The cones of the trees are sealed shut around the seed with a resin that will only dissolve under very high temperatures such as those caused by fires. Another example is flooding. Flooding, in some areas like the Nile Delta in Egypt, brings rich nutrients to the soil.


It is a delicate balance within each ecosystem. Competing for food, water, light, and other resources is how plants and animals stay in balance. This balance is called homeostasis.

If a new plant or animal is brought into an ecosystem, where it did not exist before, it competes with the existing organisms for available resources. The new plant or animal can out compete other organisms and cause them to become extinct by breaking the chain and thereby affecting other organisms that depended on the extinct organisms for food.

When an ecosystem functions smoothly, there are many benefits to people including healthy forests, streams, and wetlands which contribute to clean air and water. The survival of healthy ecosystems, however, is sometimes threatened by human activities that include deforestation, filling of wetlands, damming rivers, and polluting the air, soil, and water. Today, there are government agencies and other organizations that work to manage and protect Earth’s natural resources and ecosystems.

Bring it Home

Review the cycles of energy and nutrients with your students and ask that they illustrate each cycle. I’ve put together an interactive Ecosystem Cycles Flip Book specifically for this purpose – print this freebie and get started today!

If you are interested in more in-depth ecology activities, I encourage you to check out my curriculum materials:


Ecology Explorations is one of my favorite hands-on life science curriculum because it provides several opportunities to explore your local ecosystems. What better way to learn about ecology than to get out there, collect data, and experience the physical factors that influence the animal and plant communities first hand.

Estuary Ecology is a fourteen lesson unit study that focuses upon estuaries and salt water marshes. It incorporates a month-long moon observation project as well as a field trip to an estuary or salt marsh.