Biology - Eva Varga

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.

Life 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

Experimental Set Up

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.
Each group should utilize the water quality kit to test the pond water and record the data in their journals.
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).
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.
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

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).
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.

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.

This 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?

The 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.

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

As has become tradition, I love taking my students outside in the spring for a variety of science activities. Our STEM Club ecology focus one year was on soil ecology and I thereby planned a couple of outings to a small lake in a residential neighborhood not far from my home. Despite the proximity to homes, I am always surprised at the diversity of wildlife we are able to observe here.

We parked on the street adjacent to the lake and immediately became aware of a Killdeer nest just a few feet from the road. The two adults loudly began to distract the kids and lure them away from their nest. Despite my efforts and those of the birds, the ever-so-inquisitive boys in my group managed to locate the nest and excitedly proclaim there were eggs! It was difficult to keep the kids away and get focused on soil. Even as class was underway, one wandered quietly back over to sit closely and watch the birds for several minutes.

Killdeer nest on open ground – often in gravel – using a slight depression to hold the eggs. They don’t line it at all and since there is no structure to stand out from its surroundings, a killdeer nest camouflages marvelously into the background. Even their speckled eggs themselves look like stones.

For more information on Killdeer and their unusual behaviors, I encourage you to read The Precocious Killdeer on Birdwatching.com

NestWatch

Upon sharing this discovery with a friend of mine, she introduced us to NestWatch. NestWatch is a nationwide monitoring program designed to track status and trends in the reproductive biology of birds, including when nesting occurs, number of eggs laid, how many eggs hatch, and how many hatchlings survive.

By finding and monitoring bird nests, NestWatch participants help scientists track the breeding success of birds across North America. Participants witness fascinating behaviors of birds at the nest and collect information on the location, habitat, bird species, number of eggs, and number of young.

Participating in NestWatch is easy and just about anyone can do it, although children should always be accompanied by an adult when observing bird nests. Cornell Lab provides a wealth of tutorials and resources to guide you along the way. It is rewarding to know that your observations will be added to those of thousands of other NestWatchers in a continually growing database used by researchers to understand and study birds.

I quickly signed up and recorded our observations. We returned two days later to check on the status of the nest, but were unable to find any sign of the birds. There were no shell fragments or signs of young precocial birds. Despite the uncertainty of our Killdeer nest, we are now excited to find more nests and to share our observations with the scientists at Cornell Lab.

Citizen Science with Cornell Lab

More than 200,000 people contribute to the Cornell Lab’s citizen-science projects each year, gathering data on a vast scale once unimaginable. Scientists use these data to determine how birds are affected by habitat loss, pollution, and disease. They trace bird migration and document long-term changes in bird numbers continentwide. The results have been used to create management guidelines for birds, investigate the effects of acid rain and climate change, and advocate for the protection of declining species.

Using the same login name and password that you create for NestWatch, you can also participate in any of the following citizen-science projects:

Great Backyard Bird Count — http://birdcount.org/
Celebrate Urban Birds — http://celebrateurbanbirds.org/
Project FeederWatch — http://feederwatch.org/
eBird — http://eBird.org/
YardMap — http://yardmap.org/

Get Started Today

Involvement in citizen science projects enables students to make connections with relevant, meaningful, and real experiences with science. In turn, their experiences help facilitate their own investigations as they gain confidence.

There are many citizen science projects today and more become available each year. I encourage you to take time to explore some of the opportunities. I am confidant you will find projects that match your interests.

simple graphic image of tree with text The Nature Book Club

Welcome to the The Nature Book Club Monthly Link Up. Devoted to connecting children to nature, the monthly link up will begin on the 20th day of each month.

We welcome your nature book and activity related links. Read on for more details and for a giveaway!

See all the great posts from The Nature Book Club’s co-hosts in April:

The Nature Book Club is brought to you by these nature loving bloggers which are your co-hosts. Are you following them? If you don’t want to miss anything, be sure to follow each one.

Bird Nest/Eggs nature study pages from Barb at Handbook of Nature Study

Eggs: Nature’s Perfect Package from Erin Dean at the Usual Mayhem

Getting Started with Citizen Science – Nest Watch from Eva Varga

From Egg to Sea Turtle Unit Study & Lapbook from Tina’s Dynamic Homeschool Plus

Eggs Nature Study Free Printable Word Search from Faith and Good Works

Egg Scavenger Hunt with Egg Carton from Katrina at Rule This Roost

Felt Bag Handicraft from Melanie at Wind in a Letterbox

Clay Eggs Project from Emily at Table Life Blog

Online Book Club from Dachelle at Hide the Chocolate

Egg Identification Nature Bingo {Free Printable} from Cassidy at Freshly Planted

Party Rules

Choose an engaging nature book, do a craft or activity, and add your post to our monthly link up.
The link up party goes live at 9:00 a.m. EST on the 20th of each month and stays open until 11:59 p.m. EST on the last day of the month. Hurry to add your links!
You can link up to 3 posts. Please do not link up advertising posts, advertise other link up parties, your store, or non-related blog posts. They will be removed.
By linking up with us, you agree for us to share your images and give you credit of course if we feature your posts.That’s it!
Let’s party.

An InLinkz Link-up

This past week, I shared with you our discoveries while we were in the Galápagos in a five-day series titled, The Islands of the Galápagos. Today, I would like to share with you the wildlife of the Galapagos archipelago, while also showcasing the life zones and ecology of the islands.

Visitors to the islands notice that there are few species on the Galápagos archipelago. The geology of the islands, with the constant volcanic activity, creates a harsh, desert climate with very little rain and high temperatures so that only the higher slopes of the larger islands have enough rain to nourish a luxuriant growth of plants.

This, in turn, results in an environment that is very hostile for most animals that are found on the continent. Most of the islands are low and what little rain they get comes during a short rainy season, with the rest of the year being very dry. The amount of rain varies from one year to the next.

“The natural history of these islands is eminently curious, and well deserves attention… Considering the small size of these islands, we feel the more astonished at the number of their aboriginal beings, and at their confined range…Hence, both in space and time, we seem to be brought somewhat near to that great fact–that mystery of mysteries–the first appearance of new beings on this earth.” ~ Charles Darwin, The Voyage of the Beagle

“Eminently curious” well describes the natural history of the Galápagos, from its sere landscapes to its comical birdlife. For over 400 years this volcanic archipelago has both puzzled and stunned its visitors, and no aspect of the islands is as stunning as its wildlife. The ease of approach to the birds, iguanas, tortoises and other creatures of the Galápagos is due to their isolation from natural predators, a condition that first stirred Charles Darwin in 1835.

Eco-zones of the Galápagos

There are a total of seven zones within the archipelago housing a variety of plant life. Varying amounts of rainfall with altitude, and from island to island, have led to the formation of vegetation zones ranging from desert to lush cloud-forest.

Various plants and animals have adapted over the years to the conditions of the islands and in some cases the condition of the zone. Plantlife (or flora) is normally found in a specific zone and the animal life (fauna) dependent on those plants can be found in the same zone.

Coastal Zone

The lowest life zone on the island is the coastal zone. Those plants here can be divided into the Wet Coastal Zone (or Mangrove Zone) and the Dry Coastal Zone (beaches and high tide areas). Saltbush is found near most shores, where it forms a dense low shrubby tangle.

Mangroves are salt-tolerant trees and shrubs that thrive in shallow and muddy saltwater or brackish waters. In the Galápagos there are 4 varieties of Mangroves including the Black Mangrove, White Mangrove, Red Mangrove, and Button Mangrove.

Here most of our walks in the Galápagos took place — with the scuttle of the bright orange Sally lightfoot crabs underfoot, beneath the gaze and snort of the marine iguanas, to the barking of sea lions and the crashing of the surf off the shore. This is the environment we will remember when we look back on our time spent in the Galápagos.

Lowlands Zone

As an island slopes from the beach to an elevation of about 197 ft (60 m) elevation an arid desert like zone occurs. This region is home to the many Cacti that live in the Galápagos including the Prickly Pear Cactus, Lava Cactus, and Candelabra Cactus .

Vine plants also make their home here; the endemic lava morning glory and endemic passionflower can be found in this zone. At the top of the Arid Lowlands the silvery leafed Palo Santo Tree with its collection of lichens can be seen.

Transitional Zone

Rising up the island, plants become more frequent. In the Transition Zone plants from both the Arid Lowlands and the Upper Moist Zones occur. This zone is home to a variety of small trees or shrubs including the endemic Pega Pega Tree and the endemic Guaybillo, which produces a small white flower that develops into a fruit similar to its cousin the Guava.

“The distribution of the tenants of this archipelago would not be nearly so wonderful, if, for instance, one island had a mocking-thrush, and a second island some other quite distinct genus…. But it is the circumstance, that several of the islands possess their own species of tortoise, mocking-thrush, finches and numerous plants, these species having the same general habits, occupying analogous situations, and obviously filling the same place in the natural economy of this archipelago, that strikes me with wonder….” ~ Charles Darwin, Voyage of the Beagle

Scalesia Zone

The lowest of the “humid” zones, the Scalesia zone is named for the daisy tree that grows between 970-1970 ft (300 – 600 m) elevations. The Scalesia is one of the few trees in the Aster Family and grows to heights 16 – 50 ft (5-15 m) in height. Its trunk and branches are covered with moss and lichens. This area is humid and has the essence of being in a rainforest.

Scalesia Trees have been greatly reduced in numbers since humans arrived in the islands. With them came pigs and goats, which devour the young plants and feed on older plants. People also introduced the Guava, a plant whose dense growth patterns steals nutrients and eventually makes it impossible for competing plants to survive.

Brown Zone

An intermediate zone between the dense Scalesia forest and the Miconia shrubb vegetation, the Brown Zone is an open forest dominated by cat’s law, tournefortia pubescens, and aunistus ellipticus. Trees are heavily draped with epiphytes, mosses, livertorts and ferms, which give this zone a brown appearance during the dry season. However, on the islands with this elevation, this zone has disappeared because of colonization by man.

Miconia Zone

Above the Scalesia Zone at 1950 – 2300 ft (600-700 m) is the humid zone named for the Miconia shrub that once dominated this region. Miconia Robinsoniana grows to heights of 10-13 ft (3-4 m). The yellow or reddish shading on the edges of its leaves easily identify it.

The Miconia is endemic to the Galápagos, but since the arrival of man it has become the most endangered plant in the islands. Introduced cattle have grazed the Miconia into dangerously low levels.

Pampa Zone

On islands with elevations over 3000 ft (900 m ) the highest vegetation zone in the Galápagos can occur, the Fern-Sedge Zone or Pampa Zone . The appearance of this zone depends on the amount of moisture it receives. This region contains no true trees or shrubs. The tall Galápagos Tree Fern and Liverworts are commonly found in this zone.

Wildlife of the Galapagos *

BIRDS

Blue-footed booby (Sula nebouxii) ✓
Red-footed booby (Sula sula)
Nazca booby (Sula dactylatra) ✓
Waved albatross (Diomedia irrorata) ✓
Magnificent frigatebird (Fregata magnificens) ✓
Galapagos penguins (Spheniscus mendiculus) ✓
Lava heron (Butorides sundevalli) ✓
Great blue heron (Ardea herodias) ✓
Yellow-crowned night heron (Nyctanassa violacea)
Striated heron (Butorides striata) ✓
Brown pelican (Pelecanus occidentalis) ✓
Flightless Cormorant (Nannopterum harrisi) ✓
Lava gull (Larus fuligihosus) ✓
Flamingo (Phoenicopterus ruber)
Galapagos hawk (Buteo galapagoensis) ✓
Red-billed tropicbird (Phaethon aetheus) ✓
Storm petrels (Hydrobatidae) ✓
Swallow-tailed gulls (Creagrus furcatus) ✓
Galapagos mockingbird (Nesomimus parvulus) ✓
Cactus ground finch (Geospiza scandens) ✓
Warbler finch (Certhide a olivacea) ✓
Great egret (Ardea alba) ✓
Cattle egret (Bubulcus ibis) ✓
Galapagos rail (Laterallus spilonotus) ✓
Lava gull (Leucophaeus fuliginosus) ✓
Brown noddy (Anous stolidus) ✓
Galápagos dove (Zenaida galapagoensis) ✓
Darwin’s finches (Tanagers) ✓
American yellow warbler ✓
Galapagos pintail duck (Anas bahamensis galapagensis) ✓

REPTILES

Tortoise (Geochelone elephantopus) – fourteen subspecies ✓
Land iguana (Conolophus sp.) – two species ✓
Marine iguanas (Amblyrhynchus sp.) – seven subspecies ✓
Lava lizard (Tropidurus sp.) – seven species ✓
Gecko (Phillodactylus sp.) – seven species
Snake (Dromicus sp.)

MAMMALS

Sea lion (Zalophus californianus wollebacki) ✓
Fur seals (Arctocephalus galapagoensis)
Galápagos rice rat
Hoary bat
Eastern red bat

INVERTEBRATES

The Galápagos islands are also home to innumerable marine invertebrates. This very diverse group includes molluscs (e.g., shells and snails), marine annelids (e.g., segmented worms), echinoderms (e.g., sea urchins, sea stars, and sea cucumbers), cnidarians (e.g., corals and gorgonians), sponges, and many others. Some of the more notable species we observed include:

Sally Lightfoot Crab ✓
Sea Cucumbers ✓
Chocolate Chip Star ✓
Blue Sea Star ✓
Galapagos Carpenter Bee ✓
Large Painted Locust ✓
Galapagos Scorpion ✓

* checkmarks indicate the animals we observed

If you would like to further explore the Galápagos from the comfort of your home or if you are planning to visit yourself, my multidisciplinary unit study, Galápagos Across the Curriculum, provides ample opportunity for kids to explore the diversity and remarkable history of the islands through a variety of hands-on science activities and projects.

Some species of native ladybugs in North America are disappearing. In just the last 20 years these beneficial predators of farm and garden pests have become extremely rare. This rapid decline is of great concern. Recognizing the need to take action, a number of schools in New York State began the Lost Ladybug Project in 2004.

The Lost Ladybug Project is a citizen science project that people of all ages to look for any ladybugs they can find, and then send in pictures of each one. One of the first major discoveries came in 2006 when Jilene (age 11) and Jonathan (age 10) Penhale found a rare ninespotted ladybug near their Virginia home. This was the first ninespotted ladybug seen in the eastern U.S. in 14 years. Their finding confirmed that the species was not extinct and that with enough people working together we can find even these rare species.

With recent funding from the National Science Foundation the Lost Ladybug Project has expanded and now anyone in North America can participate. Both common and rare ladybugs, whether native or introduced, are important to find. They all contribute to understanding where different species of ladybugs can be found and how rare they really are. Once we know where the rare ladybugs can be found, we can try to protect their habitat and save them!

ladybughike We have been participating since 2012 when we first learned of the project. You can read about our earlier discoveries here:

Ladybugs, Ladybugs, Ladybugs (2012)
Hunting the Lost Ladybug (2013)
Identifying Ladybug Species (2015) – coming soon

All About Ladybugs

What do ladybugs eat? A single ladybug larva will eat about 400 medium-size aphids during its development to the pupal stage. Males may eat less but an adult female will eat about 300 medium-size aphids before she lays eggs. She can eat about 75 aphids in a day and may consume more than 5,000 aphids in her lifetime!

Did you know that ladybugs use their antennae to touch, smell, and taste?

What would happen if all the ladybugs were gone? Both adult and larval ladybugs are known primarily as predators of aphids but they also prey on many other soft-bodied insects and insect eggs. Many of these are agricultural pest such as scale insects, mealybugs, spider mites and eggs of the Colorado Potato Beetle and European Corn Borer. A few ladybugs feed on plant and pollen mildews and many ladybugs supplement their meat diet with pollen.

Beetles chew from side to side, not up and down, like people do.

How did ladybugs get their name? The most common legend is that during the middle ages in Europe, swarms of aphids were destroying crops. The farmers prayed to the Virgin Mary for help – and help came in the form of beetles that devoured the plant-destroying pests and saved the crops! The grateful farmers named these insects “Our Lady’s beetles,” a name which had endured to present day.

How long do they live? After a female lays her eggs, they will hatch in between three and ten days, depending on ambient temperature. The larva will live and grow for about a month before it enters the pupal stage, which lasts about 15 days. After the pupal stage, the adult lady beetle will live up to one year.

Why are they so brightly colored? Why do they have spots? The bright colors serve as a warning to indicate to any potential predators of the distasteful repellents the beetle will release if attacked. The spots are part of the bright warning pattern and vary depending upon species.

What eats ladybugs? Lady beetles are not commonly eaten by birds or other vertebrates, who avoid them because they exude a distasteful fluid and commonly play dead to avoid being preyed upon. However, several insects, such as assassin bugs and stink bugs, as well as spiders may commonly kill ladybugs.

How many different species are there in the US? In the world? There have been over 500 species of ladybugs identified in the United States, and over 4500 in the entire world. Only about 70 of these are the cute red, yellow, and black ones we think of most.

Ladybugs can be found all over the world and can move between continents. Introductions of new species can affect natives. What you will be doing as part of the Lost Ladybug Project is sampling the ladybugs in your habitats.

Inquiry Challenge

The degree to which specific ladybug species are associated with particular plant hosts (or their prey) is still an unsolved mystery. This would make a wonderful science fair project for advanced students.

You may also be interested in my Ultimate Guide to Studying Insects. Here you will find links to curriculum and resources for the major insect orders.

If you are interested in participating in the Lost Ladybug Project, visit the website to learn more. There is also an app to enable you a fast way to upload and share images on the go!
ladybugs journal

We’ve always enjoyed taking part in the monthly challenges at Handbook of Nature Study. This month, our selected challenge was Incorporate a Photo. Later in the week, we utilized one of our photos to create a nature journal entry to commemorate our outing.

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.

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.

diagramheart The 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

Guess how many times your heart beats in one minute ( _____ bpm) and record this in your notebook.
Take your pulse and record it in the inactive column as _____ bpm.
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.
Run in place or do jumping jacks for two – three minutes.
Take your pulse and record it in the active column as _____ bpm.
Rest for 5 minutes.
Take your pulse and record it in the recovery column as _____ bpm.

Discussion

Have your pulses returned to normal?
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

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

Discussion

Which type of blood cell represents the largest number? [red cells]
Describe the red blood cells. [disk-shaped, pink]
What is the shape and color of the white blood cells? [shape of cell depends upon the shape of nucleus, which stains blue]
Describe the different shapes of the stand nuclei in the white blood cells. [round, kidney-shaped, horseshoe-shaped, etc.]
What are the solid parts of human blood? [red cells, white cells, platelets]
Why are the centers of human red blood cells light in color? [there are no nuclei]
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]
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.
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