WebLessons: Teaching Social Studies and Science with Online Lessons

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Core Curriculum

Biology Lessons

Secondary

Ecology

• Principles of Ecology...All forms of life exhibit interdependence. Ecology is the study of the relationship between living organisms and their environment. Ecologists explore the distribution and abundance of organisms and relationships between organisms and non-living factors such as the air, water, and soil in their environment. This lesson will explore the connections between organisms in detail, such as the relationship between respiration and photosynthesis, both on the molecular level and as they impact activity within food chains. Additionally, the lesson will trace the energy flow through a food chain or food web. As you explore various ecosystems, you will come to see them as complex systems of non-living factors and living organisms that together form one of the basic units in nature.

• Communities and Biomes...What do a drop of water found in a pond and the Amazon rain forest have in common? The answer is they are both biological communities. Biological communities are places where food webs exist and there is a natural flow of resources including energy and minerals. Biomes and communities work in tandem. Each community has members who are capable of adapting to the environment and interacting with other members. As you work through this lesson, you will discover more about the relationship between biomes and communities, the members of each community, and what questions you might ask when studying a community.

• Biological Diversity and Conservation...Life can be found in every corner of this planet. Biodiversity is the fragile web of life that inter-connects all living organisms. In one way or another, from insects and flowers to humans, even though we live in different habitats and biomes, we are inter-connected. Nature loves diversity! Most ecosystems and biomes are populated with a great variety of diverse species. Great biodiversity is a sign of a healthy environment. Humans are a part of nature. It is our interaction with the rest of nature that is where conservation interfaces with the study of biodiversity. As environmental conditions have deteriorated in biological communities across the globe, individual species are threatened. Environmental degradation causes a loss in biodiversity which ultimately can impact our quality of life. Consider how we depend upon various species on the planet. Whether it is an animal we utilize directly as a food source, or a flower that can be used to produce an antibiotic, biodiversity and conservation are current and relevant issues. In this lesson, you will explore just that, biodiversity and conservation issues.

The Life of a Cell

• The Chemistry of Life and Energy in a Cell...All living things are made up of cells. Some living things are only made up of a single cell; therefore it is necessary for a cell to be able to accomplish all of the activities required to sustain life. Indeed cells are able to do this because of specialized structures found there. These structures are called organelles. We will focus on the organelles mitochondria and the chloroplasts in this lesson. These structures are responsible for respiration and photosynthesis respectively. In the course of accomplishing these processes, certain compounds are required and produced, in particular, sugar. Sugar, like other compounds important in the functioning of living things, is an organic compound.

• Cell Cycle and Transport...Throughout its life cycle, different materials must be transported into and within the cell in order for the cell to grow, repair itself, and reproduce. Materials must move across the cell membrane to have access into and out of the cell. Remember that the cell membrane is semi-permeable, some things can move easily across it, while others require energy in order to move across. The materials that enter the cell help enable it to complete those activities required to sustain life. The cell cycle is made up of stages the cell goes through as it prepares and accomplishes reproduction.

Genetics

• Mendel and Meiosis...All of your traits, from how tall you are to the color of your eyes, have been passed on to you by your parents. Gregor Mendel was the first person to establish the patterns of heredity. He developed several principles that describe how traits are passed along. His work has been constantly updated, particularly since microscopes have enabled scientists to see what is going on at the cellular level. Scientists have also discovered the process of meiosis, in which a cell divides and the resulting cells have half the genetic material or DNA That genetic information is then passed on to offspring. These processes follow several distinct “laws” that originated with Gregor Mendel’s work.

• Patterns of Heredity and Human Genetics...Whose eyes do you have? Do you have your mother’s, father’s, or grandmother’s eyes? Your traits including eyes, skin, and hair color have been passed along from generation to generation. Proteins determine these traits, and many others. The codes for proteins are found in the DNA. A person’s DNA comes from their parents. In addition to these traits, susceptibility to diseases can be traced through your DNA. For instance, a single gene causes some diseases, such as cystic fibrosis; other genes can help to trigger the onset of a disease, such as diabetes. In this lesson you will learn about how the DNA codes are translated into proteins and how sometimes problems arise in the process, leading to mutations.

• Genetic Technology...Genetic technology is currently being used in fields as diverse as forensics and agriculture. The knowledge gained from the research in these areas is enabling farmers to produce food more cheaply and solving crimes with as little evidence as a single strand of hair. Indeed, DNA technology has moved outside of laboratories into our own living rooms as television shows present the forensics behind criminal investigations. But how is this accomplished? This lesson will give you an introduction to some of the methods that are changing everything from the food you eat to your susceptibility to disease. These methods are all based on analyzing DNA, a tiny molecule found in the cells of all living things, a tiny molecule that is different in every living thing.

Change Through Time

• The History of Life...Earth has a long and rich history of life existing on the planet. Most paleontologists, scientists who study ancient life, believe life has existed on Earth for about 3.8 billion years. Considering Earth’s age is placed at 4.5 billion years, that means that life has been here since shortly after the planet cooled, solidified, and the oceans formed. What changes have occurred since its first appearance? Life has evolved from simple to complex and has its origins in water. Today, we use geologic time as a way of identifying periods in the past where various forms of life existed or were dominant. This lesson will introduce the “cosmic clock” and various stages of life on Earth, how scientists date fossils (and we do not mean going for dinner and a movie!). The lesson will also provide a detailed study of humans and how early human migration patterns led to the diversity found within the human species today.

• The History of Life-CLONED...Earth has a long and rich history of life existing on the planet. Most paleontologists, scientists who study ancient life, believe life has existed on Earth for about 3.8 billion years. Considering Earth’s age is placed at 4.5 billion years, that means that life has been here since shortly after the planet cooled, solidified, and the oceans formed. What changes have occurred since its first appearance? Life has evolved from simple to complex and has its origins in water. Today, we use geologic time as a way of identifying periods in the past where various forms of life existed or were dominant. This lesson will introduce the “cosmic clock” and various stages of life on Earth, how scientists date fossils (and we do not mean going for dinner and a movie!). The lesson will also provide a detailed study of humans and how early human migration patterns led to the diversity found within the human species today.

• The Theory of Evolution...Evolution has been a controversial but well supported theory since its first proposal in the 19th century by Charles Darwin. This lesson will enable you to clarify what evolution is (and what it is not), what scientists are sure of and what they have formed hypotheses to explain. You will see where natural selection factors in with evolution. Understanding evolution can help us to answer big questions such as how did humans get here and are we related to other life forms in any way. By the end of this lesson you should have clear answers to these questions and more.

Viruses, Bacteria, Protists, and Fungi

• Viruses and Bacteria...We often associate viruses and bacteria with winter colds and flu, food spoilage, vaccines, and antibiotics. However, because bacteria can produce enzymes necessary to break down organic compounds, beneficial bacteria inhabit our digestive tract, enhance agricultural fertilizer, help make yogurt, and pickle sauerkraut. Similarly, some viruses are used to introduce desirable genes into cells in efforts to treat disease in plants and animals. Bacteria are single cell microorganisms that lack distinct nuclei or organized cell structure. Viruses are strands of nucleic acids (DNA or RNA) surrounded by a protective protein coat that can only replicate by infecting a host cell. Scientists continue to argue whether or not viruses are truly life forms or merely inanimate pieces of genetic code. Scientific observations suggest that plants, animals, and bacteria share a common ancestor. Indeed, fossil records of bacteria date back to 3.5 billion years ago, one billion years after the theorized formation of the Earth and 2 billion years before the oldest dated animal fossils. Viruses, however, are not present in the fossil record, raising many questions concerning their role throughout the history of life.

• Protists and Fungi...Have you ever spent an afternoon tossing stones into a pond or creek? Did you ever wonder how many lives you might have affected with each toss? A small sample of pond water may contain hundreds of microscopic organisms. Some examples include gem-like diatoms, slimy strands of algae, shoe-shaped paramecium, and whip-propelled flagellates -- all members of Kingdom Protista. Amphibious organisms in Kingdom Fungi may also be present, trapped in tiny air-bubbles or attached to rotting leaves. Protists and fungi are single-cell and multi-cell organisms. Some are tiny, such as the amoeba and Penicillium fungus; others are large, such as giant ocean kelp and underground mushrooms. Protists and fungi differ from bacteria, plants, and animals based on of their cell structure and behavior. These living things share our world and provide sources of food and medicine, but can also be parasites harmful to animals and plants.

Plants

• Plant Reproduction...If you take walks or hikes often you have probably encountered a bird’s nest, egg shells, animal dens, or insect egg cases. These things are all evidence of animal reproduction, but have you ever wondered how plants make new plants? Not all plants reproduce in the same way. Plants are divided into different groups based on their structures, whether or not they form seeds, and how those seeds are enclosed. The first plants to grow on land had to solve some interesting problems if their populations were going to be able to grow further away from a body of water. Some plants need help from animals in order to grow their populations, and they have special features that attract their helpers. Humans have developed many different techniques over the years for the purposes of agriculture, and newer techniques are happening at the molecular level. Learning about how plants reproduce can give you a new perspective the next time you go outside and it may help you choose the foods you eat!

Invertebrates

• Sponges, Cnidarians, Flatworms, Roundworms, Mollusks...The living things we study in biology have special features that make them different from one another. Biologists can use these features to determine whether or not different species are closely related to each other. Today we begin a detailed study of some of the members of the Kingdom Animalia. Remember that the level below kingdom is phylum, and we will study the characteristics of five different phyla today. As you meet representatives from each group, it is important to remember both how members from different phyla are alike and how they are different. Some of the living things you study in this lesson will not look much like animals at all, yet you will see that outside appearances are only part of the story. Biologists have a variety of exciting methods for studying different animals that were not available to some famous scientists of the past, such as Charles Darwin. In modern biology, we not only study the parts of animals we can see, we also use biochemistry to study the molecules that make up each of their cells. We can show relationships among different living things by using a special diagram called a phylogenetic tree.

• Segmented Worms, Arthropods, Echinoderms and Invertebrate Chordates...Today’s lesson focuses on four animal phyla. Phylum Annelida, the segmented worms, includes earthworms that probably live in your backyard, and leeches. Leeches are creatures that you do not want to encounter while wading in the creek; however, you can find them helping people inside doctor’s offices! Phylum Arthropoda is a vast phylum; you probably encounter at least one member of this group every day; it might be a spider web in the corner of your bathroom or a butterfly that landed on your windowsill. We often think of some of these creatures as pests; however, some are very important to the survival of other animals. Phylum Echinodermata members are best viewed while snorkeling in the ocean. A starfish may not look very threatening to you, but you are not its prey! Our final phylum includes humans, but for this lesson, we will focus on the members that do not have a backbone; they develop a soft structure that can be thought of as a “pre-backbone.” As we meet some interesting members of these invertebrate phyla, try to remember to compare them to each other as you go through the lesson. Some of them may not seem very appealing to look at, but a world where all living things looked alike would not be near as exciting.

Vertebrates

• Fish, Amphibians, and Reptiles...Five hundred million years ago, the Earth experienced a dramatic increase in the diversity of life. This Cambrian Explosion resulted in the creation of most of the phyla still in existence today, including primitive vertebrates. True vertebrates such as fish and sharks evolved 480 million years ago (mya) during the Ordovician Period. The first land vertebrates arrived during the Devonian Period 420 mya. Ancestors of modern fish, amphibians, and reptiles hold clues to how animals may have adapted from life in the water to life on land. Amphibians are creatures that, like fish, require wet environments, breathing through their skin. Unlike fish, however, amphibians have arms and legs, allowing them to move through shallow waters onto land. Reptiles have adapted to life entirely on land, having dry protective skin and amniotic eggs. Reptiles populated the land, avoiding predators at sea. Further adaptation resulted in the evolution of dinosaurs, reptile in appearance yet possessing bird-like features. The domination of the dinosaurs during the Mesozoic Era (248-65 mya) ended with sudden mass extinction, followed by the dominance of birds and mammals. The Earth is home to a vast diversity of modern fish, amphibians, and reptiles. Unfortunately, human pollution and land-use change is causing devastating destruction of ecosystems, threatening the extinction of many of these species. Indeed, the suggestion that we are in the midst of a Sixth Mass Extinction warns humanity of the critical necessity to preserve animal diversity.

• Animal Behavior...Conclusive evidence that birds and reptiles share a common ancestor emerged in the 1990s with the discovery of feathered dinosaurs. Like reptiles, birds are vertebrates that lay amniotic eggs. Their feathers, low weight, and ability to fly differentiate birds from other members of the Animal Kingdom. Mammals also descend from reptiles, mammal-like reptiles being the dominant land vertebrates during the Permian Period. After the Permian Extinction, however, their populations severely declined. True mammals, rodent-like and nocturnal, first appeared in the Triassic Period. Because mammals did not suffer the same demise as dinosaurs during the late Cretaceous Extinction, they were able to proliferate and diversify, quickly populating the ecological niches vacated by the dinosaurs. Large mammals such as the mammoth and mastodon died out during the late Pleistocene Extinction, perhaps from over-hunting by human settlers. Today, there are approximately 5500 species of mammals living on Earth. Like birds, mammals are warm-blooded vertebrates. Mammals are unique, however, in that most give birth to live young and nourish them with milk. Humans are mammals. Our strength as a species results from walking upright on two legs and having highly developed brains.

The Human Body

• The Musculoskeletal System...The skeletal and muscular systems work together to allow movement to occur in your body. In order for you to move any of your bones, a muscle must be there to pull that bone. For instance, in order to straighten your leg, muscles must pull on the bones of your lower leg to allow it to move to a straight position. The seamless working of these two systems allows for the great complexity of movements in our body – from throwing a ball to writing your name. This lesson will teach you about the structure and functions of both the skeletal and muscular systems and how they work together.

• Digestive and Endocrine Systems...What happens to your food after you put it in your mouth? This lesson will describe how the body breaks down the food we eat. From the time you put food into your mouth, until the waste products are released from the body, your digestive organs and the special chemicals found within them are working to break down the food and take in those materials that are important to the functioning of the body. Additionally, you will learn about how the body regulates itself to maintain a proper balance of substances, like sugar, that are important for the proper functioning of our bodies. This regulation of our body’s functions, including our hunger, is controlled by the endocrine glands.

• The Nervous System...The nervous system is responsible for controlling and coordinating the activity of the muscles and organs, it receives input from the senses and determines the appropriate action, and is responsible for our thoughts, memories, and dreams. Indeed, the very word “brain” generally refers, not only to an organ of the nervous system, but to something that controls other things. The spinal cord and nerves are also a part of the nervous system; these function to transmit messages between the brain and other parts of the body. In this lesson you will learn how the nervous system accomplishes these various functions that allow us not only to respond to our environment, but also to survive.

• Respiratory, Circulatory, and Excretory Systems...Everything that you do, from running a race, to sleeping, requires energy. We must breathe in oxygen in order to get the required energy from the food we eat. Once the oxygen has entered our bodies, it must be carried the cells where the energy is needed. Finally, the waste products of respiration and other metabolic activities need to be released. This lesson will teach you about the systems that accomplish this, the respiratory, circulatory, and excretory systems. Respectively, these systems are responsible for the intake and release of air, transporting materials around your body, and the elimination of wastes. These systems do not work independently of one another, but rely upon one another to accomplish their functions.

• Reproduction and Development...The reproduction of species is a complex and wonderful process. Many parts work in tandem to support new life until it is ready to leave the shelter of the female body and emerge into the world. We will start with the male and female reproductive organs. These organs are specially designed to enable the reproduction of the species. The male reproductive system is designed to create, store, and release sperm into the female’s body. Within the body are the prostate gland and epididymides, vasa deferentia, seminal vesicles, seminal fluid, the prostate glands, and Cowper’s glands. Outside the body are the penis and scrotum. The female reproductive system is designed to generate, store, and release eggs. The female reproductive system consists of those organs, which enable a woman to produce eggs, nourish the fertilized egg, and to give birth. The female organs are made up of the vulva, the vagina, the uterus (or womb), the fallopian tubes, ovaries, and breasts. One egg is fertilized by one sperm at conception. The lesson will move from the reproductive organs through to the development of a new human.

• Immunity from Disease...Have you ever had a cut that has become infected to the point where you could see a white discharge, or pus? Then you have seen the immune system in action. That white discharge contains, among other things, white blood cells. These cells are busy fighting the infection. White blood cells are only one of the components of our immune system. The immune system is like our own private army ready and willing to fight any foreign matter that enters our bodies. This lesson will teach you about some of the threats to our health, such as bacteria, as well as the ways in which our body works to defend itself against such organisms.

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