TAKS 8th Grade Science ReviewObjective 5

Earth and Space Systems

Groundwater vs Surface Water

• Groundwater: water that fills the cracks and spaces in underground soil and rock layers such as aquifers. More freshwater is found here than on the surface.

• Surface Water: water found on the surface such as rivers, lakes, oceans.

• Watershed: the land area that supplies water to a river system

How do these to systems feed into each other?

Water Cycle

Nitrogen Cycle

• Nitrogen is necessary for living things because it becomes part of proteins, and part of the material responsible for reproduction and inheritance. Without nitrogen in proteins or in DNA and RNA, no living thing would exist on the Earth.

Nitrogen Cycle

Nitrogen is an element. It is found in living things like plants and animals. It is also an important part of non-living things like the air above and the dirt below.

Atoms of Nitrogen

Nitrogen

Air

Water Soil

Atoms of nitrogen don't just stay in one place. They move slowly between living things, dead things, the air, soil and water. These movements are called the nitrogen cycle.

Nitrogen in the Atmosphere

Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in Earth's atmosphere are made of two nitrogen atoms bonded together (N2).

N2N2

N2

N2

N2

N2N2

N2

N2

N2

N2

N2

N2

N2

However the nitrogen in the atmosphere is not in a form that plants and animals can use.

The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, or by certain types of bacteria.

Plants and Nitrogen

Most plants get the nitrogen they need to grow from the soils or water in which they live.

Animals and Nitrogen

Animals get the nitrogen they need by eating plants or other animals that contain nitrogen.

Recycling Nitrogen

When organisms die, their bodies decompose bringing the nitrogen into soil on land or into ocean water. Bacteria alter the nitrogen into a form that plants are able to use.

People Affect the Nitrogen Cycle

Actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in the land, water, air, and organisms.

Farming and Nitrogen

Use of nitrogen-rich fertilizers can add too much nitrogen in nearby waterways as the fertilizer washes into streams and ponds.

Farming and Nitrogen

Waste associated with livestock also adds large amounts of nitrogen into soil and water. The increased nitrate levels cause plants to grow rapidly until they use up the supply and die.

Farming and Nitrogen

The number of plant-eating animals will increase when the plant supply increases and then the animals are left without any food when the plants die.

Carbon Cycle

Photosynthesis and Respiration are big contributors to the Carbon Cycle!

Objects in the Sky

Objects in the Sky

Objects in the Sky

Objects in the Sky

Objects in the Sky

Lunar Phases

Phases of the Moon

1. New Moon

2. Waxing Crescent

3. First Quarter

4. Waxing Gibbous

5. Full Moon

6. Waning Gibbous

7. Third Quarter

8. Waning Crescent

Rotation and Revolution

Earth’s Orbit

Earth’s Rotation = 24 hours

Earth’s Revolution = 365 days

Seasons and Length of DaySeasons:

The biggest reason is the tilt of the Earth’s axis.

Solstices: “Sun Standing Still”

The Longest Day and the Shortest Day of the Year

Equinox: “Equal Night”

Equal amount of light and dark

Plate Tectonics

Convergent Boundary

Boundaries where plates crash or crunch together

Results?

Divergent Boundary

Boundaries where plates are coming apart

Result?

Transform Boundary

Boundaries where plates slide past each other

Result?

Plate Tectonics• Divergent

Boundary

• Convergent Boundary

• Transform Boundary

Where are the most earthquakes?Where are the most volcanoes?Where are the Himalayas?Where are the Andes?

Weathering

• Weathering - process that breaks down rocks and other substances at the Earth’s surface– Chemical – breaks down rocks through chemical

changes such as water, O2, CO2, living organisms– Physical – breaks down rocks through freezing and

thawing, release of pressure, growth of plants, actions of animals

• Erosion – fragments of soil and rock are broken off and carried away

• Deposition – soil and rock are dropped in a new location

• Sediment – particles of soil and rock

Resources

• Renewable

• Nonrenewable

• Inexhaustible