Environmental Science: How Species Respond to Environmental Changes

Last week I shared with you three activities I shared with the Scouts. A timeline activity to introduce them to the historical events that have helped shape environmental policy in the United States, key terms bingo, and a fortune teller illustrating the metamorphosis of honey bees.

Today, my focus is on how organisms respond to changes in the environment and endangered species. These activities were selected to meet the requirements for #3a and 3e of the environmental science merit badge.

 Each Sunday through the month of September, I will post a description of the activities I coordinated and the resources I used to teach the environmental science merit badge. Today’s post is the second in the series.

Environmental Changes & How Species Respond @EvaVarga.netResponding to Environmental Changes

Ecologists do not only study organisms; they also study how organisms interact with other organisms and how they interact with the nonliving parts of their environments, like chemicals, nutrients, habitats, and so on.

The range and type of interactions that organisms can have with each other and with their environments are large and complex. Some ecologists focus on how individual organisms respond to their environment. Other ecologists are more interested in how organisms of the same species interact with each other in populations.

Still others spend their days examining how whole populations interact with other populations in a community. At the highest level, some ecologists focus on the big picture, studying the interactions between all of the living and nonliving elements in a given area, or ecosystem.

Natural Environmental Changes

Our environment is constantly changing. Natural disasters can cause drastic environmental changes and if severe enough, even mass extinctions. By examining previous natural disasters – earthquakes, tsunamis, hurricanes, and volcanoes to name just a few – and their environmental impacts we can learn what to expect in the future.

We opened our lesson with a discussion on the processes of erosion. The Scouts were asked to submit to me photographs of areas where they had observed erosion and to describe what elements contributed to the process. Here are a few of the photos they submitted:

Why Should We Care?

So, why should we care about ecology? For some communities changes to climate are causing longer droughts, more severe floods, and harsher environments. Let’s put it into perspective with just one case study made famous by John Steinbeck’s novel, Cannery Row.

Every year, more than 92 million tons of ocean life (like fish, aquatic plants, and so on) are “harvested” from around the world for human consumption. Billions of people rely on these harvests to sustain life – either for food directly or for their livelihood. A poor understanding of marine ecology can result in disaster.

One of the most well-known of these disasters occurred off of the coast of California in Monterey Bay in the mid-1950s. At the time, this bay was one of the most productive fisheries in the world, particularly sardines. However, before 1960, harvests had plummeted, and, by 1973, the last sardine cannery in Monterey closed its doors forever.

Unfortunately, the fishing industry had not applied common ecological sense in their decisions. Sardines were removed from the bay faster than they could reproduce, resulting in a population crash and the end of an economy.

How Do Caterpillars Respond to Stimuli?

Rainforest CaterpillarsBefore my children were born, I volunteered on an Earthwatch expedition to study Rainforest Caterpillars. It was one of the most memorable experiences of my life – particularly when I consider the impact it had on my classroom teaching strategies. While the focus of our study was on Parasitism in Caterpillars, what stands out to me about this experience was the real-time observations we were able to make in the field – recording how the caterpillars responded to mechanical stimuli.

Essentially, we would gently pet them with a small paint brush and then pinch them carefully with a pair of tweezers (enough to get a reaction but not to harm).  We would then record their behavior or reaction to the stimuli.

We did this to get a general idea of how the different species would defend themselves and observed a wide variety of behaviors including thrashing about, rearing up and attempting to bite the attacker (that would be us), as well as and most amusing, kicking frass at us.

If you have caterpillars in your local area, give this a try. How do your local species respond to the same stimuli described above?

How Do Aquatic Organisms Respond to Stimuli?

Materials

  • Living specimen of planktonic aquatic life
  • Droppers
  • Vinegar
  • Caffeinated and decaffeinated coffee
  • Sugar
  • Specimen pipettes
  • Compound micropscope
  • Salt crystals
  • Microscope slides and coverslips
  • Cotton fibers

Procedure

  1. Using a specimen pipette, remove a drop from the collected specimen.
  2. Place culture on the microscope slide and cover. Focus microscope to locate organism.
  3. After first observing normal activity, introduce artificial stimuli so the the response can be observed. Record behavior observations on a chart in a lab notebook.
  4. Prepare a new culture specimen if necessary; repeat steps 1-3.
  5. Carefully place a small salt crystal near some of the swimming organisms. Observe and record their response.
  6. Continue to add each stimuli, observing and recording the behavior each time.
  7. Observe movement. Are new structures visible on the organism? Has movement increased or decreased?

Alternatively, you might consider the Goldfish Lab I shared sometime ago.

Environmental Science Endangered SpeciesEnvironmental Changes & Endangered Species

In addition to the activities and discussion described above, Scouts were expected to write a 100 word (minimum) report an an endangered species of their choice. They were then asked to present what they had learned with the group. In this way, we would have a broader perspective and learn how environmental changes have effected a variety of species.


Join me next week as we explore topics related to pollution and acid rain.

STEM Club: Let’s Get Dirty – Life in the Mud

Mud, or sediment, is an active part of aquatic ecosystems. Sediment varies widely within and among ecosystems in its biotic and abiotic characteristics.

Biotic factors are the living components of a community or larger ecosystem.

Abiotic factors are essentially non-living components that effect the living organisms of a community.

In many ecosystems sediment can release excess phosphorus (a common aquatic pollutant) into the water column causing internal eutrophication.

When studying aquatic ecosystems, people often think about the water and things that live in the water. However, the mud at the bottom of lakes and wetlands – the sediment – is an active part of these ecosystems. A wide diversity of organisms, both macroscopic and microscopic, live in sediments.

Sediments can often be a source of nutrients, especially nitrogen and phosphorus. Nutrients released from sediments are part of an ecosystem’s internal load (as opposed to the external load, which consists of nutrients that come from outside the  ecosystems).

Most commonly, sediments release large amounts of phosphorus as phosphate, sometimes causing excessive algal growth, harmful algal blooms (growth by algae that produce toxins), and even fish kills (as dead algae fall to the bottom of an ecosystem, fuel bacterial decomposition, and consume oxygen). These negative effects caused by sediment release of phosphorus are called internal eutrophication.

STEM Club: Life in the Mud @EvaVarga.netLife in the Mud

Gather around a picnic table at a local pond or wetland area. Lead the class in a discussion about how the abiotic and biotic components of the pond could interact. Use what the students have said to link the nutrient content of the sediment and water to the activity of living things in the water. For example, nutrients released from the sediment can enhance growth of algae in the water.

Ask students to hypothesize about what they expect to see in the mud. What makes up the sediment? What makes up the pond water? Describe some possible interactions between the sediment and the water column.

Materials

  • 2 quart jars with lids for each group
  • Mud from a pond (enough for about 1/3 of each of the jars)
  • Water from a pond–algae WILL be there (enough to fill the other 2/3 of each of the jars)
  • Shovel (one for each group)
  • Water quality kits for measuring nutrients for each group
  • Compound microscope (for each pair of students)
  • Microscope slides
  • Optional Materials: Dissolved oxygen meter, dissecting microscope, thermometer, conductivity meter, funnel

STEM Club: Life in the Mud @EvaVarga.netExperimental Set Up

  1. Split into small groups and distribute materials evenly. Each group should disperse to a different area around the pond perimeter to begin the experimental set up.
  2. Each group should utilize the water quality kit to test the pond water and record the data in their journals.
  3. Each group sets up the jars: one with nothing but pond water in it (control group) and another jar with 1/3 pond sediment and 2/3 water in it (treatment).
  4. After collecting mud samples, return to the table. Lead students through the process of developing a hypothesis with the guiding questions: What differences do you expect to see in the treatment group and control group in about a week? Why do you think those differences might occur? Possible hypothesis: There will be a greater number of algae in jar with sediment and pond water compared to the jar with only pond water.
  5. Check the jars after one week. If you do not see obvious responses, check them again after two weeks as it may take some time for visible algal growth to occur.

Data Collection

  1. Qualitative Observations: appearance of the water and sediment, look for evidence of algae growth—cloudy water and green “slime” on the sediment; any bubbles coming from the sediment, smell, layers in sediment evidenced by color difference or texture changes; macroscopic organisms in either sediment or water; bacterial growth (slime).
  2. Quantitative Observations: use a microscope to count the algal cells in the water in each jar; if available, test the water in each jar with any available nutrient water testing kit (nitrogen and/or phosphorus), depth of water and sediment over time, water temperature, conductivity and dissolved oxygen, pH.If you would like to do undertake this outdoor lab activity with you students, I’ve created a free printable student page, Life in the Mud, for your use. If you download it, please leave a little note in the comments.

STEM Club: What Lives in Our Soil?

Soil is rarely devoid of life. Soil which supports plant life is teeming with many soil organisms, the majority of which are too small to see. Some examples of soil organisms are fungi, bacteria, nematodes, diatoms (algae), earthworms, ants, centipedes, millipedes, beetles, snails, and slugs. All these soil creatures and more make up the soil community. In STEM Club, we sought to discover for ourselves, what lives in our soils?

Most fungi and bacteria are supported by relationships with plant roots, so they stay close to plants. Any creatures that live on fungi and bacteria also stay close to the roots. Other larger herbivores, like beetles, ants, centipedes, and termites, feed closer to the surface where more plant debris is located.Therefore most soil creatures live within a few inches of soil closest to their food sources.

STEM Club: What Lives in Our Soils @EvaVarga.netThis community of organisms is deeply involved in the soil food web. It’s basically a recycling program, where plant and animal residues are broken down by a chain of soil consumers (nematodes, bacteria, fungi, mites, earthworms, etc), who are then consumed by birds and other mammals, cycling carbon and essential nutrients.

Soil protects soil organisms from harsh sun, wind and, rain, while still providing air, water, and nutrients essential to life. When soil organisms break down plant and animal debris they change the structure of the soil. Creatures like earthworms break down larger vegetative clumps into smaller clumps of organic matter, making the soil structure finer. In a good plant debris-based soil, the actions of earthworm, as well as the amount of organic matter, greatly increases the soil’s ability to hold nutrients and water, as well as structure (pores).

Soil lacking in oxygen, water, and organic matter would be very bare and devoid of biodiversity. The area would consist only of a few, very specific kinds of soil organisms and specific plants that could tolerate these challenging environmental conditions.

What Lives in Our Soil?

Can you think of any other examples of food webs? What are some reasons why a soil would not have a layer of organic matter or humus near the surface? What would be some environmental strategies to remedy such a soil? What would happen if a group from the soil food web (fungi, animals, plants, insects, earthworms) suddenly disappeared?

STEM Club: What Lives in Our Soil? @EvaVarga.netThe goal of this activity is to discover what lives in soil. Students will select a location to collect a soil sample, return to the classroom, and thereby note a variety of characteristics of the soil (moisture content, texture, color, etc.).

Materials

  • Small shovel(s) or trowel(s)
  • 1-liter plastic freezer bags
  • Plastic jars
  • Magnifying glasses
  • Permanent marker
  • Journals
  • Map of school grounds, town, or county (geographically and by elevation)

Procedure

1. Preparation :: Take note of locations that the students would be interested in taking samples from. Be sure to have a variety of locations:

  • Garden or flower bed
  • Wooded area
  • Near a parking lot
  • Near a sidewalk
  • Turf (grassy area)

Have a table in the classroom or other open space ready for observing soils. If students will be drying soil, you’ll need a place where soils can be left for several days
Have students draw a map of the school grounds.

2. Digging Soil :: At each selected area, have students:

  • Observe location and vegetation
  • Describe location and vegetation orally
  • Write about location and vegetation in journals
  • Use trowel or shovel to collect several clumps of soil
  • Place soil in freezer bags

3. Observations :: Place soil samples on table or other open space. Divide students into groups and distribute one soil sample bag per group. Observe characteristics of the soil
which may include:

  • Gravel
  • Rocks
  • Sand
  • Earthworms
  • Ants
  • Other soil creatures
  • Color
  • Moisture
  • Texture

4. Record observations by location on chart (sample below). Predict from chart which soils might be best for growing crops.

STEM Club: Soils Are Alive @EvaVarga.net

Extension Activities

  • Develop an inquiry project to further investigate your prediction in step 4.
  • Choose a soil organism and write an expository paragraph (include: name, appearance, role, supporting details, and conclusion).
  • Think of three animals that live in the soil and the homes they build. Students draw a soil community that includes small creatures, creatures above the soil, and plants.
  • Create an informative poster to illustrate the soil food webs (include at least five trophic levels).

You can learn more about the activities we undertook in STEM Club here:

Soil Ecology Activities for Middle School

Cycles and Ecosystems {Free Printable}

Rain Gardens & Composting

Soils Support Agriculture: Ideas to Integrate Writing

Let’s Get Dirty: Soil Horizons & Particle Size

Let’s Get Dirty: Life in the Mud

 

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) @EvaVarga.net

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) @EvaVarga.net

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) @EvaVarga.net

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?

Materials

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

Procedure

  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) @EvaVarga.net
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.

Conclusions

  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.

Homeostasis

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

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.

STEM Club: The Circulatory System

The Circulatory System consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart, which is only about the size of a closed fist. Even at rest, the average heart easily pumps over 5 liters of blood throughout the body every minute.

circulatorysystem

 

The Heart

The heart, blood, and blood vessels are responsible for distributing the life-giving substances – oxygen and nutrients – throughout the body. Circulation begins with the heart. The heart is a large muscle that squeezes itself about once every second, sending blood flowing throughout the body’s network of blood vessels.

diagramheartThe hollow, muscular heart organ is divided into two sides or pumps. The left side sends blood to the aorta (the large blood vessel that leaves the heart) and through arteries, smaller arterioles, and capillaries (the smallest blood vessels in the body) to all the cells in the body. This blood transports oxygen to the cells and picks up carbon dioxide in return.

On the return trip, the blood travels in smaller veins (blood vessels that carry blood back to the heart) that connect to larger veins and eventually to the vena cava, the large vein that leads to the right side of the heart. The right side of the heart pumps the blood up to the lungs (via the pulmonary vein), where it takes in a new supply of oxygen and releases carbon dioxide. The blood then makes a quick trip back to the left side of the heart and the cycle begins again.

You hear two sounds during every heartbeat that goes something like this:     lub-DUB        lub-DUB        lub-DUB

Lub is the sound of the tricuspid and mitral heart valves shutting (on the top chambers). Then a pause as the top chambers relax. Dub is the sound of the semilunar heart valves closing. These valves shut off the big vessels leaving the heart. Then a longer pause.

The left side of the heart muscle is a bigger and stronger pump because it must push blood through the entire body. It takes about 23 seconds for the heart to circulate blood through the body.

In STEM Club, I first had the kids sketch a diagram of a heart in their notebooks and trace the route of blood flow through each chamber. When this was complete, we moved to the kitchen.

I had purchased a cow heart from a local butcher and intended to observe each of the heart chambers with my students. My goal was to identify the aorta, vena cava, left and right atriums, and left and right ventricles and thereby visualize the flow of blood through each.

We were able to do this to some extent, but weren’t completely successful because it was not whole. It had been cut in several places and it was difficult to discern one chamber from another as a result.

How Does Exercise Affect Your Pulse? – Group Inquiry Lab

When you feel your pulse, you are feeling blood as it is forced through an artery by the beating of your heart. Arteries are blood vessels that carry blood away from the heart. This pulse is the rate at which your heart beats.

Since the physical condition of an individual affects his heartbeat, pulse tests can be used to measure physical fitness.

Materials

  • Stopwatch
  • Data chart or notebook with the following columns:  Student Name / Inactive Pulse / Active Pulse / Recovery Pulse

Procedure

  1. Guess how many times your heart beats in one minute ( _____ bpm) and record this in your notebook.
  2. Take your pulse and record it in the inactive column as _____ bpm.
  3. Record another’s pulse. If you are doing this in a co-op or small group setting, gather the results from everyone for a larger data set.
  4. Run in place or do jumping jacks for two – three minutes.
  5. Take your pulse and record it in the active column as _____ bpm.
  6. Rest for 5 minutes.
  7. Take your pulse and record it in the recovery column as _____ bpm.

Discussion

  1. Have your pulses returned to normal?
  2. Compare your recovery rate to that of your peers.

Observing Blood

The average person’s body contains about 5 liters of blood. Blood is a tissue containing plasma, red and white blood cells, and cells called platelets. Fifty-five percent of blood is plasma which is ninety percent water, nutrients, oxygen and minerals. Forty-four percent of blood is made up of red blood cells. White blood cells and platelets make up about one percent.
diagramblood

  • Red Blood Cells are the disc-shaped cells in the plasma that carry oxygen. They are concave on both sides and do not have a nucleus. There are about 5 million in one cubic millimeter of blood. They get their color from an iron-containing protein called hemoglobin, which carries oxygen to the tissues. Red blood cells are made in the marrow of certain bones.
  • White Blood Cells fight infection. They are produced in bone marrow, lymph nodes, and in the spleen. They have a nucleus. There are about 7 thousand white blood cells per cubic millimeter of blood. There are about 7oo red blood cells for every one white blood cell. They fight infection by surrounding and engulfing the microbes that cause infection. Pus is composed largely of dead white blood cells.
  • Platelets stick to the walls of injured blood vessels and start the process of blood clotting.  This helps prevents blood from escaping. They release a chemical substance whenever there is an injury. This substance (along with other chemicals in the blood) form a mass of fibers that form the clot. Made in the marrow of bone, there are approximately 300,000 platelets per cubic millimeter of blood.

Materials

  • Prepared slides
  • Microscope with a minimum of 100x
  • Alternatively, you may use images found online

Procedure

  1. Observe the prepared slides under a microscope and make a drawing of each type of blood cell.
  2. Create a data table in your notebook with the following columns:  Blood Cell Type / Description / Number of Cells in Field of View
  3. Record your observations.
  4. Include a sketch of each blood cell type.

Discussion

  1. Which type of blood cell represents the largest number? [red cells]
  2. Describe the red blood cells. [disk-shaped, pink]
  3. What is the shape and color of the white blood cells? [shape of cell depends upon the shape of nucleus, which stains blue]
  4. Describe the different shapes of the stand nuclei in the white blood cells. [round, kidney-shaped, horseshoe-shaped, etc.]
  5. What are the solid parts of human blood? [red cells, white cells, platelets]
  6. Why are the centers of human red blood cells light in color? [there are no nuclei]
  7. How do red and white blood cells differ? [white blood cells are larger, have nuclei, are irregular shape, and are fewer in number than red blood cells]
  8. What do platelets do? [help clot the blood]

Bring it Home

  • Sketch the heart muscle in your notebook and label the major parts.
  • Design a test to show how your pulse rate varies with different exercise.
  • Write a story from the perspective of a blood cell as it journeys throughout the body.
  • Research the different blood types: A, B, AB, and O. Write a report detailing what you learned and include the following terms: antigens, antibody, and transfusion.
  • Donate blood at your local American Red Cross
  • Observe the veins, arteries, and capillaries on the underside of your tongue and below your eye. [thick blue lines = veins, thick pink lines = arteries, and thin lines = capillaries]
  • Design an test to determine whether a person’s body temperature remains constant all day.
  • Enjoy these Brain Pop videos: