EIGHTH GRADE ESSENTIAL FACTS

INTERDEPENDENCE AMONG LIVING SYSTEMS

1. An ecosystem includes all of the populations that live in an area plus everything that affects them.

2. The lymphatic system is a collection of organs and vessels that return tissue fluid (or lymph) to the blood stream and help the body fight disease.

3. The nervous system is a network of specialized tissue that controls actions and reactions of the body, enabling it to adjust to its environment.  The nervous system includes the brain and spinal cord.

4. The endocrine system is the body’s control system composed of a group of glands that keeps the internal environment of the body stable by producing chemical regulatory substances called hormones.

5. Symbiosis is a close relationship between different species in which one species always benefits.  Example:  a lichen is a symbiotic relationship between a fungus and an alga

6. Commensalism is a symbiotic relationship in which one organism is helped and the other is unaffected (neither harmed or helped).  Example:  barnacles, attached to a whale, benefit from transportation and greater access to food, while the whale is not helped or harmed

7. Mutualism is a symbiotic relationship in which both organisms benefit.  Example:  goby fish and blind shrimp.  A blind shrimp digs a hole for its home.  The goby fish leads the shrimp to food and provides protection by seeing for it.

8. Parasitism is a symbiotic relationship in which one of the organisms is harmed and the other organism benefits.  Example:  tapeworms, living in a dog’s intestines, receive nourishment by taking the nourishment from the dog

FORCES AND MOTION

9. A wave is a disturbance that transfers energy from place to place.

10. The Doppler Effect is the apparent change in the wavelength (or frequency) of a wave as a result of the motion of either the source or receiver of the waves.

11. Buoyant force is the upward force that fluids exert on all matter.

12. A medium is necessary to transmit ocean waves and sound waves, but not necessary to transmit light.

13. A series circuit is a circuit that provides a single path for the current.

14. A parallel circuit is a circuit that provides more than one path for a current from a common point within the circuit.

ATOMS

15. The atomic number of an element is the number of protons in its nucleus.

16. The atomic mass of an element is the number of protons and neutrons in the nucleus.

17. A neutral atom has an equal number of protons and electrons.

18. Protons (+) and neutrons (neutral) are found in the nucleus of an atom. Electrons (-) are found outside the nucleus in the electron cloud.

CHEMICAL AND PHYSICAL PROPERTIES

19. A chemical reaction is the process by which one or more substances change chemically to produce one or more different substances.

20.  Substances that transfer heat easily are called conductors.  (Example:  metal spoon)

21. Substances that do NOT transfer heat easily are called insulators.  (Example:  styrofoam)

22. An element is the simplest pure substance.  There are approximately 120 known elements or types of atoms.

23. The modern periodic table arranges elements according to their atomic numbers.

24. Metals are elements that have a shiny luster, are malleable and ductile, and conduct heat and electricity.

25. Nonmetals are elements that have a dull luster, are brittle, and are poor conductors of heat and electricity.

26. Metalloids are elements that are neither metals nor nonmetals.  They have some properties of metals and some properties of nonmetals.

27. Horizontal rows on the periodic table are called periods.

28. Vertical rows on the periodic table are called groups or families.

29. Combining equal amounts of an acid (a pH < than 7.0) and a base (pH > than 7.0) makes a solution neutral (pH = 7.0).

30. The pH scale is a logarithmic scale from 1-14 with 1 being a strong acid and 10 being a strong base.

MATTER AND ENERGY

31. Specific heat is the amount of thermal energy needed to change the temperature of one kilogram of a substance by one degree Celsius.

32. Temperature is the measure of the average speed of the molecules within a substance.

33. Conduction is the transfer of thermal energy from one substance to another by direct contact.

34. Convection is the transfer of thermal energy through substances due to density changes within the substance.  Example:  Hot air rises because it is less dense than cooler air.

35. Radiation is the transfer of heat as waves through matter or space.

36. The freezing point of water is 0° Celsius, which is 32° Fahrenheit.

37. The boiling point of water is 100° Celsius, which is 212° Fahrenheit.

38. Zero Kelvin (-273 Celsius) is called absolute zero.  This is the total absence of movement on a molecular level and is theoretically impossible.

39. The states of matter are the physical forms in which a substance can exist.  The four states of matter are solid, liquid, gas, and plasma.

40. Melting point (abbreviated m.p.) is the temperature at which a substance changes from a solid to a liquid.

41. Freezing point (abbreviated f.p.) is the temperature at which a substance changes from a liquid to a solid.

42. Boiling point (determined by pressure) is the temperature when a liquid changes into a gas.

43. The Law of Conservation of Energy states that the total quantity of energy in the universe remains constant.  Energy is not lost or gained, only changed from one form to another.

44. An endothermic reaction has occurred when energy is absorbed and the product is cooler.

45. Exothermic reactions give off heat and make the product warmer.

46. Water vapor in the air is called humidity, which is measured with an instrument called a psychrometer.

47. Precipitation can be in the form of rain, sleet, snow, or hail.

48. A front is the boundary between air masses that have different temperatures and humidity.

49. The four types of fronts are cold, warm, stationary, and occluded.

50. The three major cloud types are cirrus, stratus, and cumulus.

GENETICS

51. A dominant allele is an allele whose trait always shows up in the organism when the allele is present.

52. A recessive allele is an allele that is masked when a dominant allele is present.

53. An organism’s genetic makeup, or allele combinations is called the genotype.

54. An organism’s physical appearance or visible traits is called the phenotype.

CYCLES IN EARTH SYSTEMS

55. The water cycle is the continuous movement of water above, on, and below the earth’s surface.

56. Evaporation is the change of water from a liquid to a gas.

57. Condensation is the process by which water vapor changes from a gas to a liquid.

58. The movement of carbon from the nonliving environment into living things and back is called the carbon cycle.

59. The movement of nitrogen from the nonliving environment into living things and back is called the nitrogen cycle.

60. The different appearances of the moon throughout the month are called the lunar phases and are caused by the moon’s orbit around the earth.

61. Tides are the regular rise and fall of the oceans caused by the gravitational pull of the earth, moon, and sun.

62. The three types of rocks are igneous, sedimentary, and metamorphic.

63. Layers of rock are called strata.

64. Sedimentary rock is formed when sediments are deposited, compacted, and cemented.

65. Igneous rock is formed when magma or lava cools, hardens, and crystallizes.

66. Extrusive igneous rocks form above ground by quick cooling.  Intrusive igneous rocks form below ground by slow cooling.

67. Metamorphic rock is formed when rock is changed by great heat and pressure.

68. The rock cycle is the continual changing of rock from one type to another.

CHARACTERISTICS OF UNIVERSE

69. Three types of galaxies are spiral, elliptical, and irregular.

70. Stars are spinning clouds of gases that radiate heat and light through nuclear fusion.  Nuclear fusion squeezes a star’s hydrogen atoms together creating helium atoms, which releases a tremendous amount of energy.

71. Most astronomers believe in the big bang theory, which states that the universe began as a concentrated area of matter and energy that exploded.

72. Stars have a life cycle.  The way a star dies is determined by its mass.  Small and medium sized stars cool to become white dwarfs then eventually burn out to become black dwarfs (dead stars).  As massive and supermassive stars die, they can become black holes or neutron stars.

73. The closest galaxy to our own Milky Way is the Andromeda galaxy, which is a spiral galaxy.  The Andromeda galaxy, also known as M31 in the Messier catalog of celestial objects, is over 2 million light-years from Earth.

74. Distances to stars are so great that they are described by how far light travels in a year.  This distance is called a light year.  Light travels 300,000 kilometers per second (or 186,000 miles per second).  Note that the light year is a unit of distance, not time.

75. The distance from the earth to the sun is called an Astronomical Unit, abbreviated AU.  An AU is approximately 150,000,000 kilometers or 93,000,000 miles.

76. Galaxies are huge collections of billions of stars held together by gravity.

ALTERATIONS OF EARTH SYSTEMS

77. Continental drift is Alfred Wegener’s theory that the continents have drifted apart from one another over time.

78. Sea-floor spreading is the process by which new oceanic lithosphere is formed at the midocean ridges.

79. Three types of tectonic plate boundaries are convergent, divergent, and transform.

80. Uplift is the rising of regions of the earth’s crust to higher elevations.

81. Plate tectonics is the theory that the lithosphere is divided into tectonic plates that move around on top of the asthenosphere.

82. The earth’s plates move because of convection currents in the magma of the earth’s mantle.

83. Faults are cracks in the earth’s crust that move.  The four types of faults are normal, reverse, thrust, and strike-slip.

84. Fossils are the remains, impressions, or traces of past animal or plant life.

85. Index fossils are used to determine the relative age of rock layers.  Example:  Trilobites are used as index fossils because they lived and became extinct during the Paleozoic Era.

86. Relative dating is the process of determining the order of events and the relative age of rocks (older or younger) by examining the position of rocks in the layers.

87. Pangaea is the name given to the large landmass of which all the continents were once joined.

88. The Principal of Uniformitarianism states that the processes that act on the earth today are similar to the processes that acted on the earth in the past.

89. Ozone is made up of three-oxygen atoms (O₃) and is found in the stratosphere.

90. A renewable resource is one that can be used over and over or that has an unlimited supply.

91. A nonrenewable resource is one that cannot be replaced over thousands or millions of years.

92. Conservation is the preservation and wise use of natural resources.

93. A mineral is a naturally occurring, inorganic, solid that has a crystal structure and a definite chemical composition.

94. Minerals can be identified by: color, luster, hardness, streak, density, crystal shape, and cleavage/fracture.

95. On the Mohs Hardness Scale, a diamond is the hardest mineral (10) and talc is the softest mineral (1).

PROCESS SKILLS

96. Volume is the amount of space an object occupies.  Mass is the amount of matter an object contains.

97. Density is the amount of matter in a given volume.  Density = Mass/Volume

98. The S. I. basic unit of:

length-meter

mass-kilogram

volume-liter

temperature-Celsius

99. A hypothesis is a possible explanation or answer to a question.  (an educated guess)

100. The x-axis on a graph is the independent or manipulated variable; these data points are plotted on the horizontal axis.  The y-axis is the dependent or responding variable; these data points are plotted on the vertical axis.