Science 6: Bi-Weekly Assessment #2

What effect does lack of food, disease, and predators have on a population?

• They can limit the growth of the population.

• They increase the mutations in a population.

• They increase the rate of population growth.

• They prevent a population from becoming extinct.

Answer explanation

If there is not enough food, it will cause the population to decrease by limiting the growth of the population.

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The diagram below shows an aquatic food web that demonstrates how the organisms in the ocean get the food and energy they need to survive. What would most likely happen to the sea otters if all the crabs died out?

• The sea otters would start eating sharks.

• The sea otters would have more sea stars to eat.

• The sea otters would eat more kelp and algae.

• The sea otters would starve.

Answer explanation

If the crabs die, there will be more sea stars and therefore more food for the sea otters.

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What happens if a wolf pack's habitat decreases in size?

• The number of animals the wolf pack preys upon will decrease.

• More wolves will migrate into the area.

• The number of wolves the habitat can support will decrease.

• Wolves are omnivores and will begin to eat more plants than animals.

Answer explanation

If the wolf habitat decreases in size (where it lives), then the habitat will not be able to support the same number of wolfs. The habitats support will decrease.

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If the producers in a food chain disappear, -

• herbivores disappear too.

• energy can be transferred from one consumer to another.

• energy can be transferred from herbivores to carnivores.

• consumers take the producers' place.

Answer explanation

The producer is the plant. If the plants disappeared. so would the grasshoppers. Grasshoppers are herbivores because they only eat plants.

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The graph below shows the population sizes of predator and prey species in an ecosystem over approximately ninety years. If this prey population decreases, then the predator population will —

• grow

• remain the same

• increase

• decrease

Answer explanation

The predator and prey relationship is directly proportional to each other. If one decrease, so will the other.

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A squid that lives in the ocean near Hawaii has a special organ in its body to help it hide from predators. Bacteria live in this organ and produce light that shines downward. The squid can change the brightness of this light so that it matches the light from the moon and the stars. This helps hide the squid from predators below because predators think the light is coming from the moon and stars. The bacteria do not hurt the squid; they are actually helping it. The bacteria are helped in return with food and a safe environment in which to live. This kind of relationship is known as —

• symbiosis

• photosynthesis

• integration

• competition

Answer explanation

Symbiosis is the close relationship between two organisms. There are 3 types of Symbiosis: mutualism, commensalism, and parasitism.

Crocodiles often allow plovers (small birds) to enter their mouths to pick bits of food from between their teeth. Both the crocodiles and the plovers benefit.

• saprophytism

• commensalism

• mutualism

• parasitism

Answer explanation

Mutualism is a symbiotic relationship that benefits both organisms. The crocodile and the plovers benefit each other.

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When does competition occur between members of different species?

• When the species are the same size

• When one species migrates to a new niche

• When a new niche becomes available

• When the species share the same niche

Answer explanation

Competition is when two species compete for the same resources. These organism will have the same niche (role in the ecosystem).

Given the aquatic food chain below:

In the diagram shown, which of the following is represented?

• Water evaporating

• Energy being transferred

• Metamorphosis

• Marine life cycle

Answer explanation

The arrows in a food chain shows the direction the energy flow.

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A mole had just finished eating three sow bugs when a sharp-eyed owl caught and ate the mole. The sow bugs had been eating old grass clippings. Which of these diagrams best represents a food chain for the feeding pattern described?

• Grass → Bugs → Mole → Owl

• Bugs → Mole → Owl

• Owl → Mole → Bugs → Grass

• Owl → Mole → Bugs

Answer explanation

The arrows shows how the energy is being transferred in the food chain. The energy goes from the grass, to the bugs, to the mole, and to the owl.

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