08th Grade Science Final Study Guide
(by Vasu Jayanthi)
Unit 1: ECOSYSTEMS:
ECOSYSTEM: all the interactions between the biotic (living) and abiotic (non-living) parts of an area
Biology: the study of life
Biometrics: the science of measuring the biological data of any life form (fingerprints, etc.)
Limulus polyphemus: Atlantic Horseshoe Crab
•	Their blood is blue because it contains copper
•	The blood’s reaction to bacteria is quick and effective
•	The blood can be used to detect bacteria and treat certain diseases
•	One of the oldest species and can adapt very easily
•	Humans take the blood but taking the horseshoe crabs from their homes, and the crabs sometimes die during the process
Calidris canutus: Redknot bird
•	The Rufa is a specific population
•	Rufas have one of the longest migration patterns of birds around the world
•	Partway through their journey, they stop at the Delaware Bay and eat horseshoe crab eggs
•	Help humans study bird behavior patterns and endurance of the birds
•	Human experiments disrupt their lives
Lysate: the material released when a cell breaks down
•	Lysates extracted from horseshoe crab blood can be used to treat certain types of cancer and other diseases
Mark and Recapture: A method of measuring large populations of animals by capturing a small part and marking them, then later capturing another part and counting how many have already been marked
Environmental Issues:
•	Resource Use
•	Population Growth
•	Pollution
The main issue relevant to the horseshoe crabs and the redknots is resource use. Since humans use horseshoe crabs as a source of bait and for their blood, they’re rapidly dying. As a result, the redknots, which depend on the horseshoe crab eggs for food, are also dying. 
Interactions:
•	Competition: When two species compete against each other for certain resources
•	Predation: Organisms eating other organisms
•	If there is lots of prey, then there can be more predators. However, if there are too many predators, and not enough prey, the predators will compete against each other for food and eventually die out. With fewer predators, the prey can thrive.
•	Symbiosis: An interaction where at least one of the two species involved benefits 
•	Mutualism: Both species benefit from aiding each other (++)
•	Commensalism: One species benefits and the other isn’t affected (+0)
•	Parasitism: One species benefits (parasite) and the other is harmed (host) (+-)
Dichotomous Key: A method of classification
Atomic Structure: Atoms are made up of protons, neutrons, and electrons
•	Protons: Positively charged particles that have a mass of 1 atomic mass unit
•	Neutrons: Particles without a charge that have a mass of 1 atomic mass unit
•	Electrons: Negatively charged particles with such a small mass that the mass is often ignored when calculating the mass of an atom
•	Nucleus: Composed of a proton, or protons and neutrons
•	Shell: Region surrounding the nucleus, where electrons reside
•	The first shell contains up to 2 electrons, and every shell after that contains up to 8 electrons
•	Isotope: Different masses of an atom due to presence of neutrons
•	Ion: An atom with a specific charge (+ or -)
•	Valence Electrons: The electrons in the outermost shell
•	In order to form molecules, atoms must join by making their electrons form a complete shell.
•	The Lewis Dot Structure shows the number of valence electrons.
Ex.  

First Twenty Elements of the Periodic Table:
Harry Heard LibBey B. CaN OFtNe NaMge All Significant People South of ClArK, California. 
•	
•	Hydrogen (H)
•	Helium (He)
•	Lithium (Li)
•	Beryllium (Be)
•	Boron (B)
•	Carbon (C)
•	Nitrogen (N)
•	Oxygen (O)
•	Fluorine (F)
•	Neon (Ne)
•	Sodium (Na)
•	Magnesium (Mg)
•	Aluminum (Al)
•	Silicon (Si)
•	Phosphorus (P)
•	Sulfur (S)
•	Chlorine (Cl)
•	Argon (Ar)
•	Potassium (K)
•	Calcium (C)

Unit 2: ENERGY:
ENERGY: Something that has the ability to cause change
•	Energy is NOT force!
•	Energy is NOT matter!
•	Energy can be neither created nor destroyed. (Law of Conservation of Energy)
Energy can be transformed through forces.
Energy can be transferred to various mediums.
Kinetic Energy: The energy of movement
•	Speed and mass affect KE
•	KE=1/2m*v2
Gravitational Potential Energy: Has the potential to become kinetic energy; energy in its resting phase
•	Height and mass affect GPE
Heat Energy: Random kinetic energy of the particles that make up a substance or object
•	Also known as thermal energy
•	Friction: The force that changes kinetic energy into heat energy
•	Temperature: The measure of the average random kinetic energy
•	Determined by mass and temperature
•	Heat does NOT rise!
•	Specific Heat: The amount of heat needed to change the temperature of 1 unit of any certain substance by 1°C
•	Calorie: The amount of heat needed to change the temperature of 1 gram of water by 1°C
•	Conduction, convection, radiation
Chemical Energy: Energy caused by chemical reactions
•	Ex. Food getting broken down by stomach acids
•	Energy stored in chemical bonds of molecules
The Particle Model: All matter is made up of particles
Conduction: Heat energy moving through solids
•	Being heated one layer at a time, and the layers transfer energy to the next layers
Convection: Heat energy moving through liquids and gases 
Radiation: Heat energy being transferred through waves

Electromagnetic Spectrum: The name given to the different types of radiation

•	Radio Waves: The longest wavelength, with the lowest frequency and lowest energy, can be used to learn what certain things such as stars are made out of
•	Microwaves: Found in microwaves (like in your kitchen!)
•	Infrared Rays: Emitted by our bodies, which allow Night Vision goggles to detect our bodies in the dark; the way that remote controls work
•	Visible Light Spectrum: The only part of the EM spectrum that the human eye can see
•	Composed of red, orange, yellow, green, blue, indigo, and violet 
•	White light is composed of these colors; together these make white
•	Something that appears to be a certain color absorbs all the color and reflects one color, making it appear a certain way.
•	Ex. A red stop sign absorbs orange, yellow, green, blue, indigo, and violet, but reflects red
•	Ultraviolet Rays: The heat emitted by the sun, that causes skin to burn
•	X-Rays: Can be used by doctors to see bones and teeth
•	Gamma Rays: The shortest wavelength, with the highest frequency and the highest energy (turned Bruce Banner into the Hulk!)

Wave: Organized movement of energy 
•	Mechanical: Requires a medium, such as sound, or a water wave
•	Electromagnetic: Can travel through air and the vacuum of outer space
Frequency: The rate at which a wave travels
Hertz: A unit of frequency, equal to one cycle per second
Longitudinal Waves: A wave where the energy moves parallel to the particles
•	Ex. Sound travels longitudinally 
Infrasonic: Waves of frequency lower than 20 Hz; can’t be detected by humans
Ultrasonic: Waves of frequency higher than 20,000 Hz; can’t be detected by humans
Transverse Wave: A wave where the particles move perpendicularly to the movement of the energy
•	Ex. Light travels in transverse waves

Parts of a (Transverse) Wave: 

Remember: Energy is not made up of particles, but particles can hold energy.
Photon: A massless particle that travels at the speed of light
Laser Beam Diagram:

Photosynthesis: The process by which plants make energy for themselves
•	CO2+Water                                     Oxygen+Glucose
•	Occurs in chloroplasts of plant cells
•	Autotrophy
Reactants: 
(Carbon Dioxide)
(Water)

Products:
(Oxygen)

(Glucose)

Cellular Respiration: The process by which all organisms make energy in their cells
•	Glucose+Oxygen                                   Carbon Dioxide+Water
•	Takes place in the mitochondria of the cell
The Sun: The source of all energy in an ecosystem
Producer: Autotrophs that take their energy directly from the sun, primarily plants, some protists, and few bacteria
Consumer: Rely on other organisms for their food, heterotrophs
•	Herbivores, carnivores, and omnivores
•	Primary consumers (organisms that eat producers)
•	Secondary 
•	Tertiary
•	Quaternary
•	Decomposers: A type of consumer that feeds on dead organisms- mostly fungi and bacteria
Energy Pyramid:

Unit 3: WEATHER:
WEATHER: the condition of the atmosphere at a particular place and time
Climate: the average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area
•	Primarily determined by temperature and precipitation
Climate Region: a large area with similar climate conditions all throughout
Microclimate: a much smaller area where the climate may be different than its general climate region due to factors such as presence of mountains, coastal regions, open space, etc.
Temperature: 
•	Mainly affected by latitude, altitude, distance from large bodies of water, and ocean currents
Precipitation: 
•	Mainly affected by prevailing winds and presence of mountains
•	Precipitation falls on the windward side of the mountains, the side the oncoming wind hits. By the time the air reached the other side of the mountains, it has lost much of its water vapor, so it is cool and dry. The land on the leeward side of the mountains-downwind- is in a rain shadow.
Polar Zone: 66.5 to 90 north, 66.5 to 90 south
Temperate Zone: 23.5 to 66.5 north, 23.5 to 66.5 south
Tropical Zone: 23.5 north to 23.5 south
Ocean Current: A certain direction that seawater flows in a particular area
Diagram of Ocean Currents:

Main Layers of the Atmosphere:
•	Troposphere: 
•	The lowest layer (surface of the Earth)
•	For every 1 km. increase in altitude, the air gets 6.5 degrees C cooler
•	Stratosphere
•	Extends from the end of the troposphere (the tropopause) to about 50 km. above the earth’s surface
•	The upper stratosphere is warmer than lower stratosphere due to the presence of ozone, which helps maintain more heat energy
•	The lower stratosphere is about -60 degrees C
•	Mesosphere
•	The middle layer of the atmosphere
•	Extends from 50km. above the earth’s surface to 80 km.
•	Protects the earth from objects from out of space
•	Shooting stars are meteoroids that burn up as they reach the mesosphere
•	Thermosphere
•	Two layers- ionosphere and exosphere
~ Ionosphere starts at 80km. and ends at 550 km.
~ The Aurora Borealis, or ‘Northern Lights’ occur in the ionosphere
~Exosphere starts at 550km. and extends outwards into space (no defined limit)
•	Very hot, close to 1,800 degrees C
High Pressure Systems: Air moving downward creates high pressure and rotates clockwise. 
•	Clouds don’t form in high pressure (fair weather)
Low Pressure Systems: Air moving upward creates low pressure and rotates counterclockwise
•	Clouds form (contributing to rainy or stormy weather)
Wind: Horizontal movement of air across the earth’s surfaces 
•	Named based on the direction it comes from
•	Ex. Westerlies travel from west to east
Air Mass: A body of air that has certain characteristics all throughout
•	Humidity and temperature are the two main characteristics used for classification
•	Its first name is based on humidity
•	Maritime: Humid (wet) air masses that form over oceans
•	Continental: Drier air masses that form over land
•	Its last name is based on temperature
•	Polar: Cold air masses from the north
•	Tropical: Warmer air masses from the south
•	Ex. A maritime tropical air mass forms over warm ocean water and is moist and warm.
Weather Front: The area where two or more air masses meet and don’t mix; a boundary between two or more air masses
•	There are four types of fronts
•	Cold Front: Fast moving cold air runs into a slow moving warmer air mass; the cooler air slides under the warmer air and pushes the warmer air upward
•	Warm Front: Warm air mass collides with a slow moving cold air mass; warm air is less dense and so moves over the cooler air 
•	Stationary Front: Cold and warm air masses meet, without either air mass being moved by the other
•	Occluded Front: A warm air mass is caught between two cooler air masses and is lifted above them
Air Pressure: the force air exerts on everything else
•	It creates wind
•	It creates clouds
•	It gives clues about what will happen next
•	Air is mostly made up of nitrogen (78%) and oxygen (21%)
•	Air pressure depends on the number of air molecules and how fast they are moving
•	Pressure is greater at lower levels because the air’s molecules are squeezed under the weight of the air above 
•	Millibars are a direct pressure measurement
•	Air pressure decreases as altitude increases
•	Winds are stronger where the high and low pressure systems are close together
How strong winds will be and where they will blow is determined by 3 factors:
•	Pressure Gradient Force (PGF): To forecast winds, meteorologists note the size of the pressure difference and the distance between the high and low pressure areas
•	Friction: As winds blow near the surface of the earth, it rubs against trees, hills, buildings, and other objects that slow it down. There is less friction over water than over land. 
•	Coriolis Effect: If the earth was not spinning, then the wind would blow straight from high pressure to low pressure and die down when the pressures equalize. But the earth is spinning, which is why winds curve as they blow. This curving motion is called the Coriolis Effect. 
Cloud: a visible mass of condensed water vapor floating in the atmosphere, typically high above the ground
•	Fog is a type of cloud!
Clouds are categorized by:
•	Shape 
•	Height
•	What they do
Shape:
•	Cirrus: Thin, wispy
•	Cumulus: Puffy, Billowy
•	Stratus: Flat, sheet-like
Height:
•	Cirro-: High clouds above 20,000 feet above sea level
•	Alto-: Middle level- 6,000 to 20,000 feet above sea level
What They Do
•	Nimbo-, -nimbus: Clouds that bring precipitation

Unit 4: ASTRONOMY:
ASTRONOMY: a branch of science that deals with celestial object, space, and the universe
•	The visible universe is HUGE!
Revolution: Planetary movement around the sun (a planet’s orbit around the sun)
•	It takes Earth 365 ¼  days to make a full revolution
•	Every four years, this ¼ catches up, which adds an extra day (a leap day!) and creates a leap year
Rotation: A planet spinning on its own axis
•	It takes Earth one day, or 24 hours to make one full rotation.
Ecliptic Plane: The plane on which all the planets in our solar system exist, rotate, and revolve
•	The ecliptic plane is traced by the Sun’s path across the sky
Changing of seasons is caused by the tilt of Earth’s axis (23.5°). For half the year, the Northern Hemisphere is directly hit by the sun’s rays, and for half the year, the Southern Hemisphere is directly hit by the sun’s rays. 
Moon Cycle: The moon cycle is independent of Earth’s rotation and revolution
•	Diagram:  

Where are we?