Download 7th grade Science Semester Review

7th grade Science Semester Review - Webb
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Speed = distance/time
Density = mass/volume
7.5 (A) – Photosynthesis
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Radiant energy (Sun) is required for photosynthesis to occur.
Photosynthesis = 6H₂O + 6CO → 6O₂ + C₆H₁₂O₆
There are:
 6 water molecules
 6 carbon dioxide molecules
 6 oxygen molecules
 1 glucose molecule
7.5 (B) – Cycling of Matter
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Humus is a nitrogen-rich layer of matter in the soil that provides nourishment for plants.
Bacteria breaks down nitrogen-rich matter in humus and releases the nitrogen back into the atmosphere.
(nitrogen cycle)
Decomposers, bacteria specifically, are involved in the process of decay and release nitrogen back into
the atmosphere.
Carbon is an essential component of all life because:
1. All living organisms contain carbon; and
2. It makes up close to ½ of the biomass of all living things.
Carbon can be found in the atmosphere, lithosphere, and in water.
Biomass is the biological material, such as plant and animal waste, that is converted into a usable or
renewable energy source.
Carbon can return to the atmosphere through respiration (breathing) of plants and animals or through the
burning of fossil fuels or forest fires.
Carbon can return to the soil through the decay of once living organisms.
Key process that occur in the water cycle:
1. Condensation
2. Evaporation
3. Precipitation
Transpiration is where water moves from the ground into the roots of the plants, then moves to the main
part of the plant and through the leaves. Finally, it moves out of the leaves and into the atmosphere.
7.5 (C) – Energy Flow Through Living Systems
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A food chain is the path of energy from one organism to another in an ecosystem.
The arrows in a food chain indicate the flow of energy from one organism to another.
Organisms get the energy they need to survive and thrive from the Sun or from eating other organisms.
Producers are organisms, such as plants that use radiant energy (Sun), carbon dioxide (CO₂), and water
from the soil to ‘produce’ its own food.
Primary consumers – herbivores (eat plants)
Secondary consumers – carnivores (eat other consumers)
Decomposers – break down dead organisms (plants or animals); they get their energy from the cells of
the organisms and turn the remains into nutrients that are released into the soil.
A food chain shows one possible flow of energy for an organism
A food web shows the energy flow and relationships of organisms within an ecosystem.
An energy pyramid shows how the amount of energy decreases as it flows from producers to consumers.
7.6 (A) – Organic Compounds
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Organic compounds must contain carbon (C) to be identified as organic.
In addition to carbon (C), hydrogen (H), nitrogen (N), sulfur (S), phosphorus (P) and oxygen (O) are
usually found in organic compounds.
4. biotic
Organic Compounds:
 Inorganic Compounds:
1. Composes (makes up) matter;
2. Necessary to live;
1. Composes (makes up) matter;
3. Must contain carbon (C) which
2. Necessary to live;
comes from living or once living
3. Does not contain carbon (C); and
matter; and
4. Abiotic
Organic compounds come from living things.
7.7 (A) – Work
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Work is the use of force to move an object a measurable distance.
Work = force x distance
The unit of measurement for work is (J) joules.
For work to be done, the object must move.
The amount of force decreases when you use a simple machine to move an object. The amount of work
being done stays the same.
7.7 (C) – Forces in Everyday Life
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Gravity is a force that pulls.
Gravity and wind are the two forces that act on plants
Turgor pressure is a force within the plant.
Turgor pressure is a force due to water in the cell that pushes outward on the cell wall, allowing plants to
stand up straight.
When a plant has low turgor pressure, the cells will collapse and shrivel causing the plant to wilt.
A seedling’s force must be greater than the force of gravity for it to emerge through the soil.
7.8 (B) – Changes in Texas Land
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Erosion is caused by glaciers when they pluck rocks from the mountains and carry them long distances
down the valleys.
 Alpine glaciers form in the mountains and carve out deep U-shaped glacial valleys
 Continental glaciers form as large sheets of ice and spread out over significant portions of a land
mass.
Definition
Weathering
Destructive forces that
change the rock
Erosion
Rock or soil is moved to
another location
Type or Agents
Chemical or Mechanical
Running water, ice, or
wind
Deposition
Sediments settle in a
different location due to
gravity
Wind, ice, or water
7.8 (C) – Watershed
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Many sources of surface water and groundwater are directly connected.
Contaminates make it groundwater through surface water or through precipitation that soaks through to
the groundwater.
7.10 (A)(B)(C) – Ecosystems and Environments
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Biodiversity is the number of different species of plants animals in an area.
Sustainability is the ability of an area to maintain itself in the face of outside factors.
Succession is the series of predictable changes that occur in a community over time.
Freshwater: Bodies of water with less than 1% salt concentration such as lakes, ponds, rivers, and
streams. The climate can vary dependent upon the region but would include a time of moderate
temperatures. Ponds and lakes typically have seasonal temperature variations; summer temperatures
range from 4C near the bottom to 22C at the surface, and winter temperatures range from the same 4 at
the bottom to a surface temperature of 0C. The types of organisms could include algae, fish, aquatic
plants, insects, clams, crustaceans, amphibians, turtles, snakes, and aquatic birds such as ducks.
Marine: This biome includes bodies of water with a salt content above 1% such as oceans, coral reefs,
and estuaries. The climate and types of organisms depend upon which type of marine environment is
studied. Estuaries, for example, have algae, seaweed, marsh grasses, mangrove trees (in the tropics),
worms, oysters, crabs, waterfowl, and fish.
Forest: There are three types of forest biomes based on the latitudes which can dictate the climate:
tropical, temperate, and taiga (or boreal). Tropical rain forests have a tropical climate with little variation
year round. The temperature varies between 20C to 25C during rainy and dry seasons. The soil is
typically nutrient poor and very acidic. The biodiversity is high, having as many as 100 different tree
species in a square kilometer. There are many different species of animals as well, including various
types of birds, bats, small mammals, and insects.
Grassland: This biome is dominated by grasses and small shrubs instead of trees. There are two types of
grasslands: savannas and temperate grasslands. Savannas are found in tropical, warm, hot climates and
has an annual rainfall of 50 to 127 cm per year. The rainfall typically occurs during half the year and is
followed by six months of drought during which wild fires are common. Savannas often have thin, clay-
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rich soils. Typical organisms include a few dominant grasses (depending on the soil type); grazing
mammals, such as giraffes, zebras, buffalo, and elephants; their predators, such as lions, leopards, and
hyenas); and other organisms, such as kangaroos, mice, moles, gophers, ground squirrels, snakes,
worms, termites, and beetles.
Desert: This biome is defined as an area with less than 50 cm of rainfall a year. Deserts can be found in
cold or hot climates. The soils are very nutrient rich. Organisms in this biome are adapted to survive
without much water. Plants are typically ground-hugging and are able to store water in the stems, such
as cactus. Other plants commonly found in the desert include yuccas, ocotillo, turpentine bush, prickly
pears, false mesquite, sotol, ephedras, agaves and brittlebush. Animals are usually nocturnal, such as
kangaroo rats. Other common organisms include spiders, reptiles, and birds.
Tundra: This is the coldest of all biomes. There are two types: arctic and alpine. The soils have poor
drainage and are very low in nutrients. Rainfall is comparable to a desert. There is a very short growing
season and a low diversity of organisms. There are no trees, and the plants are very low-growing, such
as lichens, mosses, low shrubs, sedges, liverworts, and grasses. Other organisms include mammals, such
as lemmings, voles, caribou, arctic hares, squirrels, arctic foxes, wolves, polar bears, mosquitoes, black
flies, and arctic bumble bees.
7.11 (B)(C) and 7.12 (A) – Adaptations of Species
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A trait is a characteristic or quality of an organism that is genetically inherited from one generation to
the next.
The purpose of a trait is to better enable each organism to survive.
An adaptation is the process by which a population becomes better suited to its habitat.
Selective breeding is a form of artificial selection whereby deliberate breeding results in desired traits in
plants or animals.
7.14 (B) – Reproduction
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Diverse offspring are created from sexual reproduction.
Diverse offspring receive DNA from two parents, giving them a unique set of traits.
Offspring created from asexual reproduction all have the exact same DNA and the exact same traits.