Science Background Information for Teachers
Below is the science background information about ecosystems and plant and animal structures, as well as their function, including adaptations to survive in harsh ecosystems. Use this background to help you effectively teach the science content of the Grade 4 Life Science Module. Refer to the sources and additional resources listed below for more information.
In this module, students learn about the internal and external structural adaptations that animals and plants use to survive and thrive in the following ecosystems:
- Grasslands: In the grassland ecosystem, grass is the dominant vegetation, with few trees and shrubs. Earth's major grasslands include the African savanna, the prairie in the North American Great Plains, and the Steppes of Eurasia. (The Grassland Biome) Grasslands have a wet and dry season. Grazing animals migrate in groups to access water and protect group members from predators. (Grasslands--WWF) Meanwhile, plants have specialized root structures to collect limited water and anchor themselves against strong winds. Fires are important to the grassland as they help recycle nutrients in the soil and reduce competition from woody plants (i.e., shrubs and trees). (Grasslands--National Geographic)
- Desert: Deserts are extremely dry and receive less than 10 inches of rain per year. Deserts are often very hot in the day and very cold at night. The Sahara Desert in northern Africa is the largest and most well-known desert in the world, but the Mojave Desert and Great Basin are deserts found in the western United States. In order to survive in the desert, many animals are nocturnal. They hide underground during the hot day and hunt for food during the cooler night. Some plants survive by storing water in their stems. (Desert) Animals often get their water intake from eating plants and seeds, though many plants are covered in spines or thorns to ward off these threats. (Desert Animal Survival)
- Tundra: Tundras are found in the polar regions of the earth, and are very cold and receive very low precipitation. Like deserts, tundras often receive less than 10 inches of precipitation, mostly in the form of snow. Furthermore, the soil is almost always frozen, a condition known as permafrost. During the Arctic summer, temperatures get high enough to thaw the surface layers of the permafrost. The water that is released finds low and flat areas and makes them very wet. So, despite the desert-like precipitation amounts, some of the tundra is covered with wetlands during the summer (Tundra) In order to survive in this ecosystem, animals often have smaller bodies and shorter limbs, so they require less energy to stay warm. They have thick fur, and in some animals their brown fur changes to white in the winter to better camouflage with snow. (Tundra Animals) Similarly, plants grow close to the ground and are often covered in fine hairs to reduce heat loss. (Plant Adaptations--Missouri Botanical Garden)
Even though these ecosystems are distinct, they share extreme conditions--including limited rainfall and extreme temperature variance.
Most animals have several body systems that help them maintain stability in order to survive, grow, and reproduce. Each of these systems is made of organs that work together to perform its functions. The systems that students study in this module are as follows:
- Musculo-skeletal System: Invertebrates do not have bones; instead, they use muscles to control movement. In vertebrates, this system includes all of the muscles, bones, cartilage, tendons, and ligaments that allow an animal to move. The ability to control and direct movement is one of the most important differences between plants and animals.
- Digestion System: The digestive system is essential for animals to consume and break food down in order to absorb important nutrients. This is important because unlike plants, animals cannot make their own food; they must ingest food. In more complex animals this can include the mouth, stomach, intestines, and anus. Other animals just have a specialized gastric cavity where digestion takes place. In this module, students learn about the beginning of this complex system. They study the specialized structures found in the mouth, including teeth and other mouthparts.
- Nervous System: The nervous system is the control hub of an animal, collecting information from its environment (senses) and coordinating the animal's response. The nervous system includes sensory receptors, nerves, and in more complex vertebrates, a spinal cord and brain. The nervous system allows an animal to do everything from automatically controlling breathing and heartbeat to making memories and learning new things.
- Integumentary System: The integumentary system is the skin and other structures that make up or grow from the outer covering of animals, including fur, feathers, and claws. The main function of the integumentary system is to protect and separate the internal body of an animal from its external environment. Student learning focuses on scales, fur, feathers, and the exoskeleton of invertebrates.
Systems with which students may be familiar but are not covered in this module include: immune system (controls the body's response to illness and pathogens), circulatory system (transports nutrients and oxygen in blood throughout the body), excretory system (eliminates waste, such as in urine, from the body), reproductive system (allows animals to reproduce), and respiratory system (exchanges oxygen and carbon dioxide between the animal and its environment). (Inner Body)
All vascular plants have leaves, stem, veins, and roots (non-vascular plants, such as moss and algae, are not discussed in this module). The parts of a plant can be thought of as a system because all parts must be present and working together in order for the plant to survive. The parts of the plants studied in this module include:
- Leaves: The leaves of a plant have stomata, which are similar to the skin of an animal. The stomata are where the plants absorb carbon dioxide and release oxygen as well as water vapor. Leaves with a large surface area release more water vapor, so a small or slender leaf is advantageous in an ecosystem with limited rainfall. Alternatively, leaves can have a waxy coating to help reduce water loss. Leaves are where food is produced through photosynthesis. In this module, photosynthesis may be named for students, but the process is not explained in depth. Spines are specialized leaves for protection.
- Stem: The stem of a plant provides structure and connects leaves to roots. The stem, as well as the roots and leaves, can also store food and water for the plant for later use.
- Veins: The veins of a plant run from the leaves through the stem and down to the roots. The veins carry water through tubes called xylem and food through tubes called phloem. These terms are not named for students, but the function of veins is discussed.
- Roots: The main jobs of the roots are to anchor the plant and to absorb water. There are two main categories of roots: fibrous and taproots. Students learn both of these terms. Fibrous roots are more like a blanket of roots and resemble the branches of a tree turned upside-down underground. Taproots are made up of one main root that has small root hairs branching off the main taproot.
- Flowers: The flower is a reproductive structure of the plant where pollen is produced. If the plant depends on insects to pollinate it, the flower will have a scent, petals, bright colors, and/or nectar and other features to attract insects. If the plant relies on wind pollination, the flowers will not have these adaptations.
Because grass thrives in the tundra, desert, and grasslands, students use it as a case study in this module. Grass is used to learn the basic structures and adaptations. Students also conduct an investigation comparing how grass and radish plants respond to a variety of environmental pressures in order to determine which plant survives, thrives, or dies in a given habitat. The environmental pressures are grazing, trampling, and drought--and in the grasslands, fire. The relationship between grazers (such as buffalo) and plants is complex. Students consider only one variable, a single grazing or trampling episode, and do not learn the effects of repeated trampling or grazing. Radishes and grasses are from each of the two main flowering plant families: monocots (grass) and dicots (radish). Grass has fibrous roots, an important adaptation for anchoring on windy plains and collecting water close to the surface in areas with little rainfall. Like many dicots, radish plants have taproots. Another difference between grass and radish plants is that grass has a growth tip that is much lower than a radish's. This is what allows grass to grow back when the stem or leaves are broken. In addition, when grass is broken, it stimulates rapid growth. A radish plant does not have that adaptation.
The differences between monocots and dicots can be observed first through their seeds. All seeds contain an embryo (baby plant), cotyledon (food), and seed coat (protection). Monocots have one cotyledon while dicots have two cotyledons. During the seed germination experiment, students observe the two cotyledons of the radish seed develop into the first two leaves whereas grass, with only one cotyledon, will produce only one leaf initially. In this experiment, geotropism is also observed. Geotropism is a function of the roots in which the roots always grow down toward the center of the earth because of gravity, no matter what direction the seed is placed.
For germination to occur, the seed must be under the appropriate conditions, including having enough water, the correct temperature, and space for growth.
Seeds are also adapted for survival through their various structures for dispersal. Seed dispersal occurs because the offspring plant has a better chance for survival if it is not competing with its parent plant for resources such as light, nutrients, and space. Specialized structures allow seeds to be dispersed by wind, water, animal "walk-by," or animal consumption:
- Wind: Structures that are lightweight and designed to catch the wind
- Water: Internal air pockets that allow the seed to float on water, away from the parent plant
- Animal walk-by: Structures include Velcro(r)-type hooks that attach to an animal as it moves past the parent plant
- Animal consumption: Seeds are inside a fruit that is consumed by an animal and then passed through its digestive system unharmed
- Grasslands. Habitats. World Wildlife Federation, 2016. Web. 12 Feb 2016.
- Grasslands. National Geographic. Web. 12 Feb 2016.
- Biomes Group of the Fall 96 Biology 1B class, section 115, at UC Berkeley. Ed. Stephanie Pullen. The Grassland Biome. University of California Museum of Paleontology. University of California, Berkeley. Web. 14 Feb 2016.
- Desert. National Geographic. Web. 11 Aug 2016.
- Desert Animal Survival. DesertUSA.com. DesertUSA.com and Digital West Media, Inc., 2016. Web. 11 Aug 2016.
- Tundra. National Geographic. Web. 11 Aug 2016.
- Tundra Animals. The Animal Spot. Sciennected, 2008. Web 11 Aug 2016.
- Plant Adaptations. Biology of Plants. Missouri Botanical Garden, 2009. Web. 11 Aug 2016.
- Inner Body. HowToMedia, Inc., 2016. Web. 11 Aug 2016.
- Botany: Plant Parts and Functions. Arizona Master Gardener Manual. University of Arizona, 1998. Web. 11 Aug 2016.
- Blair, John, Jesse Nippert, and John Briggs. Grassland Ecology. Springer Science+Business Media: New York, 2014. R.K. Monson (ed.), Ecology and the Environment, The Plant Sciences 8, DOI 10.1007/978-1-4614-7501-9_14
- Speer, B.R. Monocots Versus Dicots. University of California Museum of Paleontology. University of California: Berkeley, 1995. Web. 11 Aug 2016.
- Landschoot, Peter. The Cool-Season Turfgrasses: Basic Structures, Growth and Development. Center for Turfgrass Science. PennState College of Agricultural Sciences, 2016. Web 11 Aug 2016.
- Manske, Llewellyn L., et al. Well-Timed Grazing Can Stimulate Grass Growth and Tiller Development, Rangeland Specialist Says
- Controlling Plant Growth. GCSE Bitesize. BBC, 2014. Web. 11 Aug 2016.
- Kueny, Meredith. Seed Dispersal. Cornell University's Naturalist Outreach. Cornell University, n.d. Web. 11 Aug 2016.