Unit 8 RETEST

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

• Food

• Space

• Oxygen

• Sunlight

Plants that live on the floors of densely populated forests must compete for sunlight. Which type of leaves are most likely found on plants that are best suited to living on the floor of a dense forest?

• Leaves that are needle-shaped

• Leaves that are smallest

• Leaves that store the greatest amount of water

• Leaves with the greatest amount of surface area

Three different species of plants that live in the desert are shown.

• found deep underground, and species X absorbs water near the soil surface

• found deep underground, and species X absorbs water found deep underground

• near the soil surface, and species Y absorbs water near the soil surface

• near the soil surface, and species Y absorbs water found deep underground

• Carnivores and producers

• Herbivores and carnivores

• Producers and decomposers

• Decomposers and herbivores

Some areas of an ocean are known as dead zones. These zones form when excess organic material decomposes. This increased decomposition uses up the oxygen from the water.

Which human activity is most affected by the increasing number of dead zones in the ocean?

• Commercial shipping, because dead zones change the course of ocean currents

• Offshore oil drilling, because water in dead zones is toxic

• Commercial fishing, because fish cannot survive without oxygen

• Sand mining, because oxygen is not available to form the sands on ocean beaches

A student observes several species of plants growing in a drainage ditch. Some species have short roots, while others have long roots. During periods of heavy rain, the ditch fills with fast-moving water, which uproots more plants that have short roots than long roots.

Which short-term effect will most likely result from a year with more heavy rain than normal?

• Most plants in the ditch will be plants with long roots.

• Most plants in the ditch will be plants with short roots.

• There will be no change in the numbers of plants with long roots and short roots.

• There will be an equal number of plants in the ditch with long roots and short roots.

A group of scientists studied some trees in a pine forest. In the densely forested areas, the trees were within 1 m of each other. The scientists observed that these trees had dead branches near the ground. They measured the height above the ground at which the first living branches were found on different-sized trees in the forest. Then they repeated this procedure on the same kind of trees in an open meadow. This graph summarizes the scientists’ data.

• Pine trees in a dense forest can grow taller than pine trees in an open meadow.

• Pine trees in a dense forest compete for sunlight with the surrounding trees.

• Pine trees in a dense forest are part of a less-complex food web than pine trees in an open meadow.

• Pine trees in a dense forest have more living branches than pine trees in an open meadow.

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

The movement of water across their gills is necessary for —

• staying cool

• accessing food

• obtaining oxygen

• avoiding predators

Four students were asked to create a graph representing a typical predator–prey relationship. Which graph shows a situation in which the number of predators in a population depends on the number of prey?

• 
• 
• 
• 

Black walnut trees produce a nontoxic chemical that becomes highly toxic when it is exposed to air or soil. How does this chemical help black walnut trees compete with plants growing nearby?

• By attracting herbivores to the other plants

• By suppressing the growth of the other plants

• By increasing the photosynthesis rates in the other plants

• By limiting the amount of water available to the other plants