8th Grade MCAS Science Prep

Plant vs. Animal Cells

• Plant cells have a square/rectangular shape, while animal cells are irregularly shaped or round.
• Plant cells possess cell walls, a feature absent in animal cells.
• Both plant and animal cells have cell membranes and an endoplasmic reticulum.
• In plant cells, the nucleus is located on the side, whereas in animal cells, it's in the middle.
• Mitochondria are present in both cell types, but plant cells have fewer.
• Cilia are mostly found in animal cells and are absent in plant cells.
• Plant cells have a few large vacuoles, while animal cells have many small ones.
• Chloroplasts are present in plant cells for photosynthesis, which makes them green, but absent in animal cells.
• Both plant and animal cells contain cytoplasm, the gelatinous liquid filling the cell.

Endoplasmic Reticulum

• The endoplasmic reticulum builds proteins, stores calcium, and breaks down fats.

Vacuoles

• Vacuoles function in storage, waste management, and giving structural support.

Mitochondria

• During cellular respiration, mitochondria create energy and are known as the powerhouse of the cell.

Photosynthesis

• The formula for photosynthesis is 6CO2 + 6H2O → C6H12O6 + 6O2.

Cellular Respiration

• Cellular respiration converts the chemical energy, into a usable form of energy called ATP.

Species Relationships

• Symbiotic (Mutualism): Both species benefit.
• Parasitism: One species benefits, while the other is harmed.
• Commensalism: One species benefits, while the other is unaffected.

Elements, Compounds, and Mixtures

• Elements are found on the periodic table and consist of only one type of atom.
• Compounds are formed from one or more types of elements from the periodic table in fixed combinations and can be fused together.
• Mixtures do not have fixed combinations of elements; the elements are simply mixed without chemical bonding.

Equinoxes

• During both fall and spring equinoxes, both hemispheres receive the same amount of daylight.
• The spring equinox occurs in March, and the fall equinox happens in September.
• The equator always receives 12 hours of sunlight.

Solstices

• The summer solstice occurs when the northern hemisphere has the most sunlight.
• The winter solstice occurs when the northern hemisphere has the least sunlight.

Moon Cycle

• The Moon exhibits different appearances as it revolves around the Earth due to varying amounts of sunlight reflecting off its surface.
• A new moon occurs when the moon is between the Earth and the sun, facing its dark side towards Earth.
• By day 4, a sliver of the moon becomes visible, known as the waxing crescent.
• Around day 7, the moon reaches its first quarter, revealing half of its surface.
• By day 10, roughly three-quarters of the moon is visible, entering the waxing gibbous phase.
• After about two weeks, the moon is in full moon phase, fully lit by the sun.

Eclipses

• A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting a shadow on Earth. The Moon's shadow isn’t very big, so only a small portion of places on Earth will be able to view this.
• A total eclipse happens at a New Moon when the Moon passes between Earth and Sun.
• A lunar eclipse happens when Earth gets in the way of the Sun’s light and casts its shadow on the Moon.
• Total lunar eclipses make the moon appear red, also known as a Blood Moon, which can happen at a full moon.
• Eclipses only occur during a full moon.

Shadow Components

• Umbra: The dark, inner shadow.
• Penumbra: The outer, lighter shadow.

Types of Eclipses

• Total Eclipse: The entire disk of the sun or moon is obscured.
• Partial Eclipse: Only part of the sun/moon is obscured.
• Penumbral Eclipse: The blocking celestial body casts only a light shadow on the other.

Airmasses

• Airmass – A large body of air with relatively uniform thermal and moisture characteristics.
• Airmasses are usually named for both their moisture and thermal characteristics (maritime tropical, continental polar, etc).
• High sea level pressure is often associated with cold airmasses and maritime airmasses in the summer.
• Low sea level pressure is often associated with hot airmasses and maritime airmasses in the winter.

Fronts

• Front – A boundary between different airmasses.
• Air mass usually lifts over another along a front, resulting in the formation of clouds and precipitation.
• Fronts are classified based on; Thermal and moisture characteristics of the airmasses, direction of movement of the airmasses, and whether the front is in contact with the surface or is only found aloft.

Cold Fronts

• Cold front – A front that separates warm and cold masses and the cold air is advancing and lifting the warm air.
• Thunderstorms on leading edge of front with; warm, moist, conditionally unstable airmass.
• Warm, moist stable airmass has; widespread clouds, light precipitation along front.
• No clouds or precipitation with; warm, dry stable airmass.

Warm Fronts

• Warm front – A boundary where the cold air is retreating and the warm air is advancing.
• Air is cool ahead of the warm front.
• As a warm front approaches; you will first notice high thin clouds ahead of the front, the clouds will become lower, get thicker, and light precipitation may begin to fall, and the clouds will be very low and thick and the precipitation will be at its heaviest.
• Once the warm front passes the skies will clear and the temperature will warm.
• Thunderstorms along and ahead of front with a; warm, moist conditionally unstable airmass.
• Warm, moist stable air has; widespread clouds and light precipitation along and ahead of front.

Stationary Fronts

• Stationary front – A boundary that separates cold and masses, where neither air mass is advancing nor retreating
• In a stationary front the air on the cold side flows parallel to the front.
• When warm air flows nearly parallel to front; thunderstorm, precipitation on leading edge of front
• When warm air flows toward, and up and over cold air; widespread clouds and light precipitation over cold air side of front.

Occluded Fronts

• Occluded front – A boundary between cold and colder airmasses with warm air aloft
• All occlusions cause warm air to be lofted above cold air.
• As a cold occluded front passes; the temperature changes from cold to colder, and clouds are widespread.
• As a warm occluded front passes; the temperature changes from colder to cold, and clouds are widespread.

Layers of Earth

• Crust: The outermost layer, with two types: oceanic and continental.
• Upper Mantle: Solid upper part of the mantle directly beneath the crust.
• Lithosphere: Includes both types of crust and the upper mantle.
• Mantle: Slowly moving layer under the crust made of iron and magnesium and controls crust movement based on convection currents.
• Outer Core: Liquid and very hot.
• Inner Core: Solid due to high pressure, very hot, and very dense, made of iron and nickel.

Plate Boundaries

• At an oceanic/oceanic plate boundary the older plate undergoes subduction creating a trench.
• Divergent plate boundaries create mid-ocean ridges. The rock near the middle of the ocean is younger, and the rock closer to the continents is older.
• Continental/continental plate boundaries can crumple to form mountains, be convergent (one plate goes over the other), or be transform (plates rub against each other, causing earthquakes).

Definitions

• Subduction: The sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.
• Convergent: When one tectonic plate moves over another.
• Transform: When two plates rub against each other.
• Divergent: When two tectonic plates move away from each other.