8th Grade: Unit 1 Study Guide Answers

Unit 1 Interactions of Living Things

Unit Pretest

1. B	5. C	9. C
2. B	6. C	10. D
3. C	7. C
4. D	8. A

A is incorrect because fish are living and therefore, they are a biotic factor.

B is correct because sand not living, and therefore, it is an abiotic factor.

C is incorrect because snails are living and therefore, they are a biotic factor.

D is incorrect because plants are living and therefore, they are a biotic factor.

A is incorrect because a niche is the interaction of more than one population.

B is correct because the role of a species includes how it uses its habitat within the community and how it interacts with other species.

C is incorrect because a niche includes habitat as well as interactions with other species.

D is incorrect because a niche includes interactions with other species as well as with other re-sources in the habitat.

A is incorrect because if the spider also eats part of the flower, this would harm the flower.

B is incorrect because this relationship would be commensalism, because the orchid is not affected.

C is correct because if the spider eats insects that would harm the flower, this would help the flower. Both benefit, and this would be mutualism.

D is incorrect because this would be harmful to the plant if the insects the spider captures were prevented from pollinating, so the relationship is not mutualism.

A is incorrect because crabs can escape by moving into the water, so they would not benefit by blending in with the grass.

B is incorrect because if the sandpiper blended in with the grass, it could still be spotted by the grasshoppers against the sky when the sandpiper is in the air.

C is incorrect because palm trees are not preyed upon by any predators and do not need camouflage.

D is correct because the grasshopper lives in the sand-dune grasses and would become harder for the sandpiper to spot if it blended in with the grass.

A is incorrect because to be a community, populations must also interact.

B is incorrect because a community consists of more than one type of species.

C is correct because a community includes all populations that not only live in the same area or habitat, but also interact.

D is incorrect because to be a community, the populations must interact.

A is incorrect because plants obtain some nutrients from soil, but soil is not used by the plant to make food.

B is incorrect because oxygen is a product of photosynthesis, not a reactant used in photosynthesis.

C is correct because water and carbon dioxide are the chemical materials that plants use to make food.

D is incorrect because nitrogen and phosphorus are plant nutrients, but the plant does not use these materials to make food.

A is incorrect because many consumers eat only producers or other consumers.

B is incorrect because many primary consumers obtain energy from plants without the help of decomposers.

C is correct because decomposers break down waste materials and allow resources to cycle back into the system.

D is incorrect because decomposers do not extract energy from sunlight. They return energy to the system by breaking down dead and decaying material.

A is correct because cooperation involves individuals working together for the good of the group.

B is incorrect because a lion’s color is an adaptation that helps it survive rather than a behavior.

C is incorrect because lions don’t work together to determine their diet. Cooperation occurs when individuals work in a way that benefits them all.

D is incorrect because the organization of a pride describes social hierarchy rather than cooperation.

A is incorrect because cod are a food source for seals, so a decrease in cod population would affect the seals’ food supply.

B is incorrect because a reduction in the cod population would make the shrimp population in-crease because a predator is removed from the food web.

C is correct because there is no food chain in this web that contains both cod and baleen whales, so a change in the cod population will not directly affect the baleen whales.

D is incorrect because both seals and squid are food sources for toothed whales, so a decrease in cod population would affect their food supplies.

A is incorrect because if there were no births, the population size would not be increasing.

B is incorrect because the size of the population would be constant if the rates were equal.

C is incorrect because a faster death rate would lead to a decrease in the size of the population.

D is correct because elephants are being added to the population faster than they are being re-moved.

Lesson 1 Quiz

1. D	4. B
2. C	5. D
3. D

A is incorrect because ecology includes interactions of organisms with each other as well as with their environment.

B is incorrect because ecology includes the study of biotic factors as well as the abiotic factors of weather and climate.

C is incorrect because reproducing and producing offspring is the study of biology and genetics.

D is correct because ecology includes studying the relationships between organisms as well as interactions with their overall environment.

A is incorrect because biotic factors alone are not enough to meet the needs of a population.

B is incorrect because abiotic factors alone are not enough to meet the needs of a population.

C is correct because the combination of abiotic and biotic factors meets the needs of a population in a habitat.

D is incorrect because other populations cannot meet all the needs of any population.

A is incorrect because a desert would not be covered in so much vegetation.

B is incorrect because a tundra is covered in frozen soil rather than lush vegetation.

C is incorrect because a tropical rain forest would contain more trees.

D is correct because the plants and animals shown in this image are most likely found in a tem-perate grassland.

A is incorrect because wind is an abiotic factor.

B is correct because trees are a biotic factor, so leaves are also a biotic factor.

C is incorrect because rocks are an abiotic factor.

D is incorrect because light from the sun is an abiotic factor.

A is incorrect because a species is more than closely related organisms. The organisms must also reproduce.

B is incorrect because many different kinds of species can live in the same habitat.

C is incorrect because different kinds of species can interact.

D is correct because closely related organisms that mate and reproduce to produce offspring that can also reproduce make up a species.

Lesson 2 Quiz

1. A	4. A
2. B	5. D
3. C

A is correct because mushrooms are fungi, which are decomposers that break down dead plant material.

B is incorrect because the flowering plant is a producer.

C is incorrect because the honey bee is a primary consumer.

D is incorrect because the turtle is a primary or secondary consumer.

A is incorrect because a cat is a carnivore.

B is correct because horses eat only plant materials.

C is incorrect because humans are omnivores.

D is incorrect because vultures are scavengers.

A is incorrect because a frog is a secondary consumer. It feeds on insects that eat plants.

B is incorrect because a redwood tree is a producer.

C is correct because the shark eats seals and large fish that are secondary consumers, making it a tertiary consumer.

D is incorrect because fungi are decomposers.

A is correct because one global web begins on land and the other begins in water.

B is incorrect because both types of food webs include tertiary consumers.

C is incorrect because food webs describe a particular ecosystem regardless of the presence of migratory animals.

D is incorrect because food webs describe a particular ecosystem regardless of the extent of the web.

A is incorrect because organisms that consume other organisms for energy are consumers.

B is incorrect because organisms that obtain energy from decaying matter are decomposers.

C is incorrect because soil, air, and water do not provide energy to organisms.

D is correct because producers use the energy of sunlight to manufacture food.

Lesson 3 Quiz

1. A	4. A
2. A	5. C
3. C

A is correct because predators feed on organisms in an ecosystem, and act as biotic limiting fac-tors.

B is incorrect because a drought occurs when a region receives less rain than normal. Rain is an abiotic factor.

C is incorrect because unusual weather, such as a hurricane, is an abiotic factor.

D is incorrect because the amount of living space is an abiotic factor.

A is correct because more individuals will be added to the population than are lost.

B is incorrect because individuals leave a population when the emigrate to a different location.

C is incorrect because predators will remove some of the squirrels from its population.

D is incorrect because the loss of individuals in a forest fire will cause a decrease in the size of the population.

A is incorrect because a limiting factor is an environmental factor that limits the growth of a population; in the first year of the study, the rabbit population grew steadily.

B is incorrect because a limiting factor is an environmental factor that limits the growth of a population; in the second year of the study, the rabbit population grew rapidly.

C is correct because a limiting factor is an environmental factor that limits the growth of a population; in the third year of the study, the rabbit population abruptly stopped increasing and de-creased, suggesting the rabbit population had grown too large to be supported by the resources in this environment.

D is incorrect because a limiting factor is an environmental factor that limits the growth of a population; in the fourth year of the study, the rabbit population remained constant, suggesting the population had reached a sustainable size, given the resources in this environment.

A is correct because individuals in a termite population each have a different role that serves the colony in some way. Soldiers protect the colony. The role of other individuals is to gather food.

B is incorrect because organisms without a social hierarchy might also communicate.

C is incorrect because mistletoe acts as a parasite, which is a not a level within a social hierarchy.

D is incorrect because color is an adaptation. All frogs within a population will have color.

A is incorrect because new crops might serve as food for some of the eagles’ prey.

B is incorrect because more land would give organisms on the island more space to live. This might result in an increase in populations.

C is correct because flooding the island would eliminate some populations of organisms, includ-ing organisms on which the eagles rely for food. This would lead to a large, sudden drop in the eagle population.

D is incorrect because food is a limiting factor. More food would lead to a population increase rather than a crash.

Lesson 4 Quiz

1. D	4. D
2. C	5. C
3. A

A is incorrect because, although a tree’s seeds may blow away from it, they can also land right next to another tree.

B is incorrect because it does not explain trees growing far apart from one another.

C is incorrect because it does not explain trees growing far apart from one another.

D is correct because it explains why trees do not grow right next to one another. Their roots have to spread out and thus compete with other trees for soil and water. Trees also compete for sunlight, so they need enough space for their leaves to receive as much sunlight as possible.

A is incorrect because it does not describe any particular symbiotic relationship.

B is incorrect because it does not describe the relationship of the anemone with any other organ-isms.

C is correct because the hermit crab benefits from the protection of the anemone’s sting, and the anemone benefits from being able to move around more quickly by riding on the crab’s shell.

D is incorrect because it does not describe the benefits that either organism receives from the hermit crab moving the anemone to its new shell.

A is correct because a predator, by definition, eats some other organism.

B is incorrect because some predators may participate in symbiosis, but this is not directly related to predation.

C is incorrect because an organism that is eaten by another describes prey, not predator.

D is incorrect because a parasite may benefit at the expense of another organism, but not eat that organism.

A is incorrect because no parasitic relationship is shown in the diagram.

B is incorrect because coyotes and hawks are both predators; neither preys on the other.

C is incorrect because no organism is shown that preys on coyotes or hawks.

D is correct because coyotes and hawks are both predators of rabbits and mice, so they compete for the same food.

A is incorrect because this is predation: the bird is prey for the cat, which is a predator.

B is incorrect because this is a form of mutualism: the bird gets nourishment from the berries, and the plant reproduces when its seeds are spread.

C is correct because the bird benefits, but the tree is neither helped nor harmed by the bird building a nest in a hole that was already there. This is an example of commensalism.

D is incorrect because this is predation: the bird kills the shellfish for food.

Unit Test B

Key Concepts

1. B	5. B	9. C
2. B	6. D	10. D
3. D	7. B	11. C
4. B	8. A	12. A

A is incorrect because many organisms move through the ecosystem, so the food web does not show location.

B is correct because the web shows the feeding relationships, which are also the flow of energy.

C is incorrect because producers and consumers vary greatly in size.

D is incorrect because producers and consumers vary greatly in complexity.

A is incorrect because the carrying capacity is the maximum number of individuals of a particular species that the environment can support. It will increase or decreases as resources change.

B is correct because the carrying capacity depends on the available resources in the environ-ment. Because of the drought, resources such as grass were removed from the environment.

C is incorrect because the carrying capacity changes when the environment changes following an event such as a drought.

D is incorrect because animals are consumers that depend on plants as a food source. The ani-mals cannot flourish without the plants.

A is incorrect because an ecosystem includes all the organisms as well as the nonliving things in a given area.

B is incorrect because an ecosystem includes all the organisms, as well as the nonliving things in a given area.

C is incorrect because an ecosystem includes all the organisms, as well as the nonliving things in a given area.

D is correct because an ecosystem includes all the organisms, as well as the nonliving things in a given area.

A is incorrect because carnivores do not produce their own energy.

B is correct because carnivores eat meat whereas herbivores eat plants.

C is incorrect because carnivores often have to kill their prey before they eat it.

D is incorrect because all consumers obtain energy by eating food.

A is incorrect because the structure of the plant is different from its niche.

B is correct because part of the plant’s role in its ecosystem is to produce food through photo-synthesis.

C is incorrect because a niche is the role of a species in its community.

D is incorrect because reproduction is important to the survival of the species of sunflower plants, but niche refers to how the plant interacts with other species.

A is incorrect because the population cycles shown in the graph are correlated to each other, so there is likely a relationship between the two animals.

B is incorrect because if the two animals competed over the same resources, the relationship between their populations would be a much more direct inverse correlation.

C is incorrect because whatever relationship there is between the two animals, both are clearly affected since their population cycles are correlated to each other.

D is correct because the correlated population cycles between the animals show that they have a relationship in which both animals are affected.

A is incorrect because different examples of a biome may consist of different kinds of ecosystems.

B is correct because a biome is a large region characterized by climate conditions and plants and animal communities, and an ecosystem includes all the living and non-living things in a given area; therefore, a biome may contain many ecosystems.

C is incorrect because an ecosystem includes all the living and non-living things in a given area, whether that area is as large as a forest or as small as a rotting log.

D is incorrect because a biome is a large region characterized by climate conditions and plants and animal communities, and an ecosystem includes all the living and non-living things in a given area; therefore, a biome may contain many ecosystems.

A is correct because the plover gets food, and the crocodile gets its hide cleaned, so both organ-isms benefit. This relationship is called mutualism.

B is incorrect because neither of the organisms involved is harmed in this relationship, so parasitism does not occur.

C is incorrect because neither the crocodile nor the plover preys on the other.

D is incorrect because in commensalism, only one participant benefits while the other is unaffected. In the relationship described, both participants benefit.

A is incorrect because individuals of the same species are more likely to compete for a mate.

B is incorrect because individuals of the same species are more likely to compete for a limited resource.

C is correct because cooperation occurs when individuals work in a way that benefits them all; killing a larger animal for food would benefit each predator in the group.

D is incorrect because prey animals are more likely to join in defense against a common predator.

A is incorrect because most decomposers are fungi or bacteria, and not all consumers are types of animals.

B is incorrect because many decomposers, such as bacteria, are capable of moving in search of food.

C is incorrect because both decomposers and consumers can obtain energy from plant and ani-mal sources.

D is correct because decomposers break down waste materials that consumers cannot use for energy.

A is incorrect because owls are at the top of the food chain, so they are tertiary consumers.

B is incorrect because toads eat beetles, so they are secondary consumers.

C is correct because beetles eat plants, so they are primary consumers.

D is incorrect because plants are producers.

A is correct because competition occurs when organisms try to use the same limited resource; although the air does contain resources for birds, it is not limited in the way that food, water, and space are limited.

B is incorrect because competition occurs when organisms try to use the same limited resource, such as food, water, and space.

C is incorrect because competition occurs when organisms try to use the same limited resource, such as food, water, and space.

D is incorrect because competition occurs when organisms try to use the same limited resource, such as food, water, and space.

Critical Thinking

13.

explanation of prey and predators as limiting factors (e.g., A limiting factor is an environmental factor that limits the growth of a population. Prey acts as a limiting factor because the number of prey or-ganisms determines whether predator organisms have enough food
to eat. Predators act as limiting factors because they remove individuals from a population;)
prediction of population growth based on a lack of limiting factors (e.g., Without a limit on prey and predators, the population of brown tree snakes was able to grow. As a result, the population would have experienced fast growth; etc.)

Extended Response

14.

description of food chain (e.g., A food chain represents the flow of energy and matter from producers to consumers in an ecosystem;)
summary of the food chain (e.g., The food chain would start with the grass plant, followed by the grasshopper, followed by the shrew, followed by the owl;)
name the producer (e.g., The grass plant is the producer. It converts the energy of sunlight into en-ergy stored in food;)
name the tertiary consumer (e.g., The owl is the tertiary consumer. It eats the shrew that ate the grasshopper that fed on the plant;)