National Standards for Grade 8 - Science (page 2)

Basic

Students performing at the Basic level demonstrate some of the knowledge and reasoning required for understanding the Earth, physical, and life sciences at a level appropriate to grade 8. For example, they can carry out investigations and obtain information from graphs, diagrams, and tables. In addition, they demonstrate some understanding of concepts relating to the solar system and relative motion. Students at this level also have a beginning understanding of cause-and-effect relationships.

Eighth-grade students performing at the Basic level are able to observe, measure, collect, record, and compute data from investigations. They can read simple graphs and tables and are able to make simple data comparisons. These students are able to follow directions and use basic science equipment to perform simple experiments. In addition, they have an emerging ability to design experiments.

Students at this level have some awareness of causal relationships. They recognize the position of planets and their movement around the Sun and know basic weather-related phenomena. These students can explain changes in position and motion such as the movement of a truck in relation to that of a car. They also have an emerging understanding of the interrelationships among plants, animals, and the environment.

Proficient

Students performing at the Proficient level demonstrate much of the knowledge and many of the reasoning abilities essential for understanding the Earth, physical, and life sciences at a level appropriate to grade 8. For example, students can interpret graphic information, design simple investigations, and explain such scientific concepts as energy transfer. Students at this level also show an awareness of environmental issues, especially those addressing energy and pollution.

Eighth-grade students performing at the Proficient level are able to create, interpret, and make predictions from charts, diagrams, and graphs based on information provided to them or from their own investigations. They have the ability to design an experiment and have an emerging understanding of variables and controls. These students are able to read and interpret geographic and topographic maps. In addition, they have an emerging ability to use and understand models, can partially formulate explanations of their understanding of scientific phenomena, and can design plans to solve problems.

Students at this level can begin to identify forms of energy and describe the role of energy transformations in living and nonliving systems. They have knowledge of organization, gravity, and motion within the solar system and can identify some factors that shape the surface of the Earth. These students have some understanding of properties of materials and have an emerging understanding of the particulate nature of matter, especially the effect of temperature on states of matter. They also know that light and sound travel at different speeds and can apply their knowledge of force, speed, and motion. These students demonstrate a developmental understanding of the flow of energy from the Sun through living systems, especially plants. They know that organisms reproduce and that characteristics are inherited from previous generations. These students also understand that organisms are made up of cells and that cells have subcomponents with different functions. In addition, they are able to develop their own classification system based on physical characteristics. These students can list some effects of air and water pollution as well as demonstrate knowledge of the advantages and disadvantages of different energy sources in terms of how they affect the environment and the economy.

Standards for Themes of Science

Themes are the "big ideas" of science that transcend the various scientific disciplines and enable students to consider problems with global implications. To understand the conceptual basis for the themes that have been selected, students must begin to develop an understanding of major ideas by the fourth grade. They should continue to develop their understanding through the 8th grade, and by the 12th grade, they should have the ability to integrate their knowledge and understanding.

Three of the themes are common to all of the documents: Models, Systems, and Patterns of Change.

Models of objects and events in nature can be used to understand complex or abstract phenomena. Models may be first attempts to identify the relevant variables to build evermore useful representations, or they may be highly refined for predictions about the actual phenomenon. Students need to understand the limitations and simplifying assumptions that underlie the many models used in the natural sciences. A model is likely to fit data well only within a limited range of circumstances and to be misleading outside of that range.

Systems are complete, predictable cycles, structures, or processes occurring in natural phenomena, but students should understand that the idea of a system is an artificial construction created by people for certain purposes, for example, to gain a better understanding of the natural world or to design an effective technology. The construct of a system entails identifying and defining its boundaries, identifying its component parts and the interrelations and interconnections among those parts, and identifying the inputs and outputs of the system.

Regardless of the topic around which the Patterns of Change theme is developed, students should be able to recognize patterns of similarity and difference, to perceive how these patterns change over time, to remember common types of patterns, and to transfer their understanding of a familiar pattern of change to a new and unfamiliar situation

Examples of Themes by Grade Level

Systems

Students should understand that systems are artificial constructions created by people for certain purposes, such as gaining a better understanding of the natural world or designing an effective technology.

Understanding the construct of a system entails identifying and defining its boundaries, identifying its component parts, identifying the interrelations and interconnections among the component parts, and identifying the inputs and outputs of the system.

Grade 8

Students should understand that an organism is made up of organ systems that have structure/function adaptations and interconnections among other organ systems.

Interdependence of plants and animals in communities should be understood by grade 8: plants, consumers, decomposers. Students should be able to explain specific examples such as purple loosestrife replacing cattails and the effects of the introduction of rabbits into Australia.

Disease and health should be understood in systems terms. If a part of a system is put out of kilter by disease, for example, the whole system is affected. Taking drugs or smoking by an individual may have an impact on another system (organism); for example, secondary smoke affects children of smoking parents or a fetus may be damaged by drugs. A measles vaccine taken or not taken by an individual affects the whole population of a region or even further, depending on migration patterns. If a specific animal or plant population becomes unhealthy (for example, fish poisoned, raccoons diseased, or species of grass infected by virus), the food chain and, therefore, the rest of the community are affected.

Patterns of Change

Patterns of Change is a particularly valuable theme in the life sciences because a conceptual understanding of patterns of change can be developed in the context of several different levels in the hierarchy of biological organization. At the cellular/organismal level, the primary patterns of change are the growth and development that occur throughout the life of organisms. At the population level, the primary patterns of change are the changes in population growth over relatively short periods of time and the evolutionary changes that occur over longer periods of time. At the community/ecosystem level, the primary patterns of change are those that involve the nonliving and living components of ecosystems during the process of succession. Patterns of change may be linear, or they may be cyclical; for example, many of the patterns of change that occur within cells are related to homeostasis, in which a change leads to feedback reactions that result in a return to conditions that existed before the change. An understanding of cyclical patterns of change can also be developed in the context of ecosystems (nutrient cycles) and organisms (life cycles).

Regardless of the context in which an understanding of the Patterns of Change theme is developed, students should be able to recognize patterns of similarity and difference, to recognize how these patterns change over time, and to transfer their understanding of a familiar pattern of change to a new, unfamiliar situation.

Grade 8

Understanding patterns of change at the organismal level:

• growth, development, and reproduction of the human organism
• homeostasis of body systems

Understanding patterns of change at the population level:

• adaptation and natural selection, including learned and instinctive behavior
• variation and similarity among many different organisms, including humans

Understanding patterns of change at the community/ecosystem level:

• food webs (also part of the systems theme)
• environmental effects of human activity (also part of the systems theme)

More general understandings involve the following knowledge: changes in quantity usually have natural limits, but changes in form in which each form arises from a previous one can produce an unlimited variety; the rate of change may be as interesting as the change itself; and trends can be steady, accelerated, approach a limit gradually, or have a highest or lowest value.

Models

The models theme has been selected because of the importance of enabling students to distinguish the idealizations of models from the phenomena themselves. Students need to understand that a model of the human eye does not represent all aspects of human eyes as they occur in human organisms. The model is a simplification, leaving unrepresented many important variations in human eye structure, yet the simplification has utility in illuminating some features of the eye and enables new questions about the eye to be generated.

Students need to understand the limitations and simplifying assumptions that underlie the varied models used in the natural sciences. For example, beliefs that models are replicas of real objects or events can negate the critical concept of variation that many models do not take into account. Although generalized models, such as a generalized graph of growth in populations, are useful, they are not to be confused with a graph of the growth of a particular organism or population or with a graph of data from a single experiment.

Grade 8

Students should have knowledge of both conceptual and physical models and their uses and limitations. For example, when asked to illustrate their understanding of vertebrate structure and function with models of skeletons of different vertebrates, students need to be aware of variations in real skeletons and the generalized nature of the replicas.

Example Science Content Standards

Grade - Life Science

A. Cells and their functions

1. Cells:

Students can describe their observations of cells under the microscope:

• Students can demonstrate the use of a microscope to examine a tissue, plant, or animal and to differentiate between plant and animal cells (for example, students can look at an animal cell and a plant cell and notice that an animal cell is flexible and a plant cell is not) (Scientific Investigation, Systems);

• Students can look at pond water through a microscope and describe outstanding features/activities of the protista they see (for example, locomotion, nutrition, excretion) (Scientific Investigation).

• Students can observe diatoms and try to distinguish as many features as possible (Scientific Investigation).

• Students can explain, in a general way, the advantages of cellular interdependence versus independence (for example, multicellular animals versus single-celled animals).

• Students can describe, in general terms, the difference between asexual and sexual reproduction in cells and the advantages and disadvantages of each (the stages of mitosis are not to be tested).

B. Organisms

1. Reproduction, growth, and development:

Students can describe growth, development, and reproduction of the human organism:

• Students can identify the age ranges at which human beings go through common stages of development (for example, can recognize their parents; can learn to walk, talk, and socialize; can conceive or give birth) (Conceptual Understanding, Patterns of Change).

• Students can identify the changes human beings undergo at puberty and can explain their functions (Conceptual Understanding, Patterns of Change).

• Students can, in simple terms, describe changes in human embryo development and the effects of environmental influences such as smoking, drugs, disease, and the mother’s diet on the development of the embryo (Conceptual Understanding, Patterns of Change).

2. Life cycles:

Students can identify some major influences on the human life cycle (for example, diet, disease):

• Students can discuss the influence of diet and food availability on human life cycles worldwide (Practical Reasoning, Patterns of Change).

• Students can explain that microorganisms can cause disease and can identify some common diseases caused by microorganisms such as bacteria, viruses, protista (differences between viruses and bacteria are not to be tested) (Conceptual Understanding).

• Students can describe the immune system of animals as helping the animal fight disease and as controlled, in part, by the white blood cells in the body (Conceptual Understanding).

3. Functions and interactions of systems within organisms:

• Students are aware that, although different systems of the body have different functions, the functioning of each system affects other systems (for example, students can describe/identify major organ systems of the human body, state their major functions, and describe some of their interactions):

• Students can describe the primary tissues of the body (for example, blood, lymph, muscle) and relate the special characteristics of each to its function (Conceptual Understanding, Systems).

• Students can distinguish cells from other structures under the microscope (for example, between an onion cell and a salt crystal) (Scientific Investigation, Systems).

Students can describe how two or more organs of the body work together to perform a function (for example, the heart and lungs working together in respiration) (Conceptual Understanding, Systems).

Students demonstrate an understanding of the functions and interactions of organ systems to maintain a stable internal environment that can resist disturbances from within or without (homeostasis).