Grade Level Concepts
8.1.a: The motion of an object can be described by its position, direction of motion and speed.
8.1.a.1: An object is said to be in motion when its position changes in relation to a point of reference. An object’s motion can be described and represented graphically according to its position, direction of motion, and speed.
8.1.a.2: Speed describes the change in an object’s position over a period of time, and is measured in units such as meters per second or miles per hour. Velocity takes into account an object’s speed and the direction of its motion.
8.1.a.3: Average speed takes into account the different speeds at which an object moves over a period of time. Average speed is calculated by dividing the total distance traveled by the change in time, regardless of any changes in motion or direction during its travel.
8.1.a.4: Motion of objects can be represented on a distance vs. time line graph, with distance traveled as the vertical (“y”) axis and time as the horizontal (“x”) axis. The slope (steepness) at any point of this line depends on the instantaneous speed of the moving object. A straight horizontal line indicates an object at rest.
8.1.b: An unbalanced force acting on an object changes its speed and/or direction of motion.
8.1.b.1: For an object’s motion to change, a force must be applied over a distance. The change in motion due to this force is acceleration. Acceleration describes the change in an object’s velocity over time.
8.1.c: Objects moving in circles must experience force acting toward the center.
8.1.c.2: Without a net center-pulling (centripetal) force, objects will continue to move in a straight line in a constant direction.
8.1.c.3: Objects in orbit around a larger body maintain their orbits due to the center-pulling gravitational pull of the larger body.
8.2.a: Heredity is the passage of genetic information from one generation to another.
8.2.a.5: Most multicellular organisms reproduce by sexual reproduction, in which new cells are produced by the combination of two germ cells (gametes). During meiosis, matching chromosomes in each pair separate from each other so that each germ cell contains only half of the chromosomes of the original cell.
8.2.a.10: A segment of DNA that holds the information for a specific trait is called a gene. Each chromosome in a pair carries the same genes in the same place, but there are different versions of each gene.
8.2.b: Some of the characteristics of an organism are inherited and some result from interactions with the environment.
8.2.b.2: Most human traits are inherited from parents, but some are the result of environmental conditions. For example, eating and exercising habits may affect the body mass and shape of individuals in the same family.
8.3.a: Gravity is the force that governs the motions of objects in the solar system.
8.3.a.1: Earth is part of a system of celestial bodies that are grouped together around a central star, the Sun. This system includes objects of different masses and composition such as planets, moons, asteroids, minor planets, and comets. These objects move in predictable paths determined by gravity.
8.3.a.2: Gravity is a force of attraction between two objects. The strength of gravitational force depends on the total mass of the two objects and the distance between them. The greater the total mass, the greater the force of gravity. The greater the distance between two objects, the less the force of gravity.
8.3.a.3: The difference between an object’s mass and its weight is explained by gravity. Mass is the measure of the amount of matter in an object; weight is the force of gravity between an object and the celestial body it is on. Bodies in the solar system have different masses; therefore the same object has a different weight on each celestial body.
8.3.a.4: Objects in the solar system are held in their predictable paths by the center-pulling gravitational attraction of the very massive sun. The interaction of the center-pulling force of gravity with a moving object’s inertia (tendency to keep moving) keeps a less massive object (e.g., a planet, an asteroid or a moon) in circular motion (revolution) around a more massive object.
8.3.b: The motion of the earth and moon relative to the sun causes daily, monthly and yearly cycles on the earth.
8.3.b.1: Earth rotates around an axis or rotation, a line going through the center of the earth from the north pole to the south pole. The tilt of Earth’s axis relative to its orbital path, combined with the spherical shape of the earth, cause differences in the amount and intensity of the sun’s light striking different latitudes of the earth.
8.3.b.2: Earth experiences seasons in northern and southern hemispheres due to the tilt of the earth on its axis and the resulting angle of the sunlight striking Earth’s surface at different points along its 365-day revolution period. Earth’s tilt causes seasonal differences in the height of the perceived path of the sun and the number of hours of sunlight. Seasons are not related to a change in distance between the earth and the sun, since that distance changes very little. Planets without a tilt of axis will experience no seasons in spite of the revolution.
8.3.b.5: Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon, the sun and the rotation of the earth. The times and amplitude of the tides at the coast are influenced, in part, by the alignment of the sun and moon.
Correlation last revised: 1/22/2020