• National Science Education Standards - Content Topics, and Rationale

NSES Content Standard

• Physical Science 6-8

• Matter

  Substances have characteristic properties such as density, boiling point, and solubility, which are independent of the amount of the sample. A mixture of substances can often be separated into the original substances by using one or more of these characteristic properties.

  Substances react chemically in characteristic ways with other substances to form new substances (compounds) with different characteristic properties. In chemical reactions the total mass is conserved. Substances are often placed in categories or groups if they react in similar ways, for example metals.

  Chemical elements do not break down by normal laboratory reactions such as heating, electric current, or reaction with acids. There are more than 100 known elements which combine in a multitude of ways to produce compounds, which account for the living and non living substances that we encounter.

NSES Content Standard

• Physical Science 6-8

• Motions And Forces

  The motion of an object can be described by its position, direction of motion, and speed. This motion can be represented on a graph.

  An object that is not being subjected to a force will continue to move at a constant speed and in a straight line.

  If more than one force acts on an object, then the forces can reinforce or cancel one another, depending on their direction and magnitude. Unbalanced forces will cause changes in the speed and/or direction of an object's motion.

NSES Content Standard

• Physical Science 6-8

• Tranformations Of Energy

  Energy exists in many forms, including heat, light, chemical, nuclear, mechanical and electrical. Energy can be transformed from one form to another.

  Heat energy moves in predictable ways, flowing from warmer objects to cooler ones until both objects are at the same temperature.

  Light interacts with matter by transmission (including refraction), absorption, or scattering (including reflection). To see an object, light from that object -- emitted by or scattered from it -- must enter the eye.

  Electrical circuits provide a means of converting electrical energy into heat, light, sound, chemical or other forms of energy.

  The sun is a major source of energy for changes on the Earth's surface. The sun's energy arrives as light with a range of wavelengths, consisting mainly of visible light with significant amounts of infrared and ultraviolet radiation.

NSES Content Standard

• Life Science 6-8

• Living Systems

  Living systems at all levels of organization demonstrate complementarity of structure and function. Important levels of organization for structure and function include cells, organs, organ systems, whole organisms, and ecosystems.

  All organisms are composed of cells, the fundamental unit of life. Most organisms are single cells; other organisms, including humans, are multicellular.

  Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to power the work that cells do and to make the materials that a cell or an organism needs.

  Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are in turn grouped together to form larger functional units, called organs. Each type of cell, tissue, and organ has a distinct structure and set of functions that serve the organism as a whole. The human organism has systems for digestion, respiration, reproduction, circulation, excretion, movement, control and coordination, and for protection from disease.

  Disease represents a breakdown in structures or functions of an organism. Some diseases are the result of intrinsic failures of the system. Others are the result of infection by other organisms.

NSES Content Standard

• Life Science 6-8

• Reproduction And Heredity

  Reproduction is a characteristic of all living systems; since no individual organism lives forever, it is essential to the continuation of species. Some organisms reproduce asexually. Other organisms reproduce sexually.

  In many species, including humans, females produce eggs and males produce sperm. An egg and sperm unite beginning the development of a new individual. This new individual has an equal contribution of information from its mother (via the egg) and its father (via the sperm). Sexually produced offspring are never identical to either of their parents.

  Each organism requires a set of instructions for specifying its traits. Heredity is the passage of these instructions from one generation to another.

  Hereditary information is contained in genes, located in the chromosomes of each cell. Each gene carries a single unit of information, and an inherited trait of an individual can be determined by either one or many genes. A human cell contains many thousands of different genes.

  The characteristics of an organism can be described in terms of a combination of traits. Some traits are inherited and others result from interactions with the environment.

NSES Content Standard

• Life Science 6-8

• Regulation And Behavior

  All organisms must be able to obtain and use resources, grow, reproduce, and maintain a relatively stable internal environment while living in a constantly changing external environment.

  Regulation of an organism's internal environment involves sensing external changes in the environmental and changing physiological activities to keep within the range required to survive.

  Behavior is one kind of response an organism may make to an internal or environmental stimulus. A behavioral response requires coordination and communication at many levels including cells, organ systems, and whole organisms. Behavioral response is a set of actions determined in part by heredity and in part from past experience.

  An organism's behavior has evolved through adaptation to its environment. How organisms move, obtain food, reproduce, and respond to danger, all are based on the organism's evolutionary history.

NSES Content Standard

• Life Science 6-8

• Populations And Ecosystems

  Populations consist of all individuals of a species that occur together at a given place. All of the populations living together and the physical factors with which they interact compose an ecosystem.

  Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some micro-organisms are producers--they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.

  For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is converted by producers into stored chemical energy through photosynthesis, It then passes from organism to organism in food webs.

  The number of organisms an ecosystem can support depends on the resources available and abiotic factors such as quantity of light and water, range of temperatures, and the soil composition. Given adequate biotic and abiotic resources and no disease or predators, populations, including humans, increase at very rapid (exponential) rates. Limitations of resources and other factors such as predation and climate limit the growth of populations in specific niches in the ecosystem.

NSES Content Standard

• Life Science 6-8

• Diversity And Adaptations Of Organisms

  There are millions of species of animals, plants, and micro-organisms living today that differ from those that lived in the remote past. Each species lives in a specific and fairly uniform environment.

  Although different species look very different, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

  Biological evolution accounts for a diversity of species developed through gradual processes over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhances reproductive success in a particular environment.

  Extinction of a species occurs when the environment changes and the adaptive characteristics of a species do not enable it to survive in competition with its neighbors. Fossils indicate that many organisms that lived long ago are now extinct. Extinction of species is common. Most of the species that have lived on the Earth no longer exist.

NSES Content Standard

• Earth and Space Science 6-8

• Structure Of The Earth

  The solid Earth is layered with a thin brittle crust, hot convecting mantle, and dense metallic core.

  Crustal plates on the scale of continents and oceans constantly move at rates of centimeters per year in response to movements in the mantle. Major geological events, such as earthquakes, volcanoes, and mountain building, result from these plate motions.

  Land forms are the result of a combination of constructive and destructive forces. Constructive forces include crustal deforamtion, volcanoes, and deposition of sediment, while destructive forces include weathering and erosion.

  Changes in the solid Earth can be described as the rock cycle. Old rocks at the Earth's surface weather, forming sediments that are buried, then compacted, heated, and often recrystallized into new rock. Eventually, these new rocks may be brought to the surface by the forces that drive plate motions, and the rock cycle continues.

  Soil consists of weathered rocks, decomposed organic material from dead plants, animals, and bacteria. Soils are often found in layers, with each having a different chemical composition ant texture.

  Water, which covers the majority of the Earth's surface, circulates through the crust, oceans, and atmosphere in what is known as the water cycle. Water evaporates from the Earth's surface, rises and cools as it moves to higher elevations, condenses as rain or snow, and falls to the surface where it collects in lakes, oceans, soil and in rocks underground.

  Water is a solvent. As it passes through the water cycle it dissolves mineral sand gases and carries them to the oceans.

  The atmosphere is a mixture of oxygen, nitrogen, and trace gases that include water vapor The atmosphere has different properties at different elevations.

  Clouds, formed by the condensation of water vapor, affect weather and climate. Some do so by reflecting much of the sunlight that reaches Earth from the sun, while others hold heat energy emitted from the Earth's surface.

  Global patterns of atmospheric movement influence local weather. Oceans have a major effect on climate, because water in the oceans hold a large amount of heat.

  Living have played many roles in the Earth system, including affecting the composition of the atmosphere and contributing to the weathering of rocks.

NSES Content Standard

• Earth and Space Science 6-8

• Earth's History

  The Earth processes we see today, including erosion, movement of crustal plates, and changes in atmospheric composition, are similar to those that occurred in the past. Earth history is also influenced by occasional catastrophes, such as the impact of an asteroid or comet.

  Fossils provide important evidence of how life and environmental conditions have changed.

NSES Content Standard

• Earth and Space Science 6-8

• The Solar System

  The Earth is the third planet from the sun in a system that includes the moon, the sun, eight other planets and their moons, and smaller objects such as asteroids and comets. The sun, an average star, is the central and largest body in the solar system.

  Most objects in the solar system are in regular and predictable motion. These motions explain such phenomena as the day, the year, phases of the moon, and eclipses.

  Gravity is the force that keeps planets in orbit around the sun and governs the rest of the motion in the solar system. Gravity alone holds us to the Earth's surface and explains the phenomena of the tides.

  The sun is the major sources of energy for phenomena on the Earth's surface, such as growth of plants, winds, ocean currents, and the water cycle. Seasons result from variations in the amount of the sun's energy hitting the surface, due to the tilt of the Earth's rotation axis.

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