Interdependence of Living Systems

A farmer digs a small pond in a pasture. The farmer adds young individuals from two species of algae-eating fish to the pond and plants some reeds around the edges of the pond. The farmer wants the pond to be a sustainable ecosystem.

Which of the following would be most helpful in increasing the pond ecosystem's sustainability?

• Decreasing the number of plant species around the edges of the pond

• Introducing older fish of the same species into the population of algae-eating fish

• Having a greater diversity of living organisms in the pond

• Adding gravel between the water and where the reeds are planted

Answer explanation

An ecosystem with higher biodiversity is more likely to survive weather disturbances, disease, and climate change. A wide variety of species results in genetic diversity.

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The food webs below model relationships among the organisms in two ecosystems.

Which ecosystem would be more likely to survive if a disease killed the grasses?

• The forest ecosystem, because most of the animals can eat other organisms

• The grassland ecosystem, because several predators compete for food

• The forest ecosystem, because it has three top predators

• The grassland ecosystem, because it has many herbivores

Answer explanation

The forest ecosystem is more likely to survive because there are other plant species besides grass for the ecosystem to survive off of.

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Which table correctly describes the functions of the cell structures listed?

• 
• 
• 
• 

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Three cousins have a similar appearance but different face shapes.

Which of these cell components are most involved in determining the basic shape of each girl's face?

• Genes, chromosomes, and nucleus

• Cytoplasm, chloroplasts, and genes

• Vacuoles, nucleus, and chromosomes

• chromosomes, chloroplasts, and vacuoles

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The African savanna is a grassland scattered with shrubs and small trees. Some of the organisms that live in the savanna are shown.

Which two types of organisms have a producer-consumer relationship in this African savanna?

• Zebras and hyenas

• Hyenas and cheetahs

• Trees and elephants

• Fungi and dung beetles

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Sea anemones and clown fish live together in the ocean. Which statement best describes one way sea anemones depend on clown fish for an abiotic factor in an ecosystem?

• Clown fish protect sea anemones from predator fish

• Clown fish decrease competition among sea anemones

• Clown fish consume the remains of organisms paralyzed by sea anemones

• Clown fish move water near sea anemones when dissolved oxygen levels are low

Immediately after a forest fire, the primary consumers in the area will compete most for which biotic factor?

• Food

• Space

• Oxygen

• Sunlight

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Whitetip reef sharks spend most of the day lying on the ocean floor. While remaining still, these shark pump water across their gills.

The movement of water across their gills is necessary for--

• staying cool

• accessing food

• obtaining oxygen

• avoiding predators

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The strangler fig is a vine that starts out as a seed in the tree canopy of the rain forest. It drops its roots down from the canopy to the forest floor.

By sprouting in the rain-forest canopy, the strangler fig seedling is exposed to more--

• sunlight

• soil

• nutrients

• consumers

Answer explanation

The forest's canopy blocks sunlight from reaching the forest's floor. Since the strangler fig sprouts at the top of the canopy, it has access to significantly more sunlight than it would if it sprouted elsewhere.

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The Prairies Region and the Cross Timbers are located in north-central Texas. The graph shows information about eating habits of white-tailed deer in these regions.

A Cross-Timbers rancher is concerned about competition between the ranch animals and the deer. Based on the graph, which ranch animals compete for the most food with white-tailed deer?

• Cattle that eat grass and feed

• Goats that eat weeds and shrubs

• Turkeys that eat seeds and fruit

• Hogs that eat fruits, seed, and feed

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