CHESAPEAKE BAY FOOD WEB
Based on the food web shown, which of the following is true about the feeding relationships?
- A. Bivalves have no natural predators in the Chesapeake Bay ecosystem.
- B. Wading birds are herbivores that eat aquatic vegetation.
- C. Phytoplankton are producers that convert light energy into organic matter.
- D. Sea ducks are primary consumers that eat only bald eagles.
Correct Answer & Rationale
Correct Answer: C
In the food web, phytoplankton are classified as producers because they perform photosynthesis, converting light energy into organic matter. This foundational role supports the entire ecosystem. Option A is incorrect; bivalves often have predators, such as certain fish and birds, that feed on them. Option B misclassifies wading birds, which are carnivores that primarily feed on small fish and invertebrates, not herbivores. Option D is misleading, as sea ducks are primary consumers but do not exclusively eat bald eagles; they primarily consume aquatic plants and invertebrates. Thus, option C accurately reflects the role of phytoplankton in the ecosystem.
In the food web, phytoplankton are classified as producers because they perform photosynthesis, converting light energy into organic matter. This foundational role supports the entire ecosystem. Option A is incorrect; bivalves often have predators, such as certain fish and birds, that feed on them. Option B misclassifies wading birds, which are carnivores that primarily feed on small fish and invertebrates, not herbivores. Option D is misleading, as sea ducks are primary consumers but do not exclusively eat bald eagles; they primarily consume aquatic plants and invertebrates. Thus, option C accurately reflects the role of phytoplankton in the ecosystem.
Other Related Questions
Which of the following is always true of a chemical change?
- A. Color, shape, or texture is altered.
- B. Mass is increased.
- C. A new substance is formed.
- D. Gas or vapor is generated.
Correct Answer & Rationale
Correct Answer: C
A chemical change always results in the formation of a new substance, which is a fundamental characteristic distinguishing it from physical changes. Option A is incorrect because while color, shape, or texture may change, these alterations do not confirm a chemical change unless a new substance is produced. Option B is misleading; mass is conserved in chemical reactions, so it does not necessarily increase. Option D, while often true (as gases can be produced), is not universally applicable; some reactions do not produce gas. Hence, the formation of a new substance is the definitive indicator of a chemical change.
A chemical change always results in the formation of a new substance, which is a fundamental characteristic distinguishing it from physical changes. Option A is incorrect because while color, shape, or texture may change, these alterations do not confirm a chemical change unless a new substance is produced. Option B is misleading; mass is conserved in chemical reactions, so it does not necessarily increase. Option D, while often true (as gases can be produced), is not universally applicable; some reactions do not produce gas. Hence, the formation of a new substance is the definitive indicator of a chemical change.
Which TWO of the following statements about the universe are true?
- A. The universe is expanding.
- B. The Milky Way galaxy contains most of the stars in the universe.
- C. A star's size, temperature, and composition typically remain constant throughout its life cycle.
- D. A black hole is usually detected by the intense visible light it emits.
Correct Answer & Rationale
Correct Answer: A
Option A accurately reflects current astronomical understanding, as evidence shows the universe is expanding due to the redshift of distant galaxies. Option B is incorrect; while the Milky Way is large, it contains only a small fraction of the universe's stars, which are spread across billions of galaxies. Option C is misleading; stars undergo significant changes in size, temperature, and composition throughout their life cycles, particularly during phases like red giant or supernova. Option D is also false; black holes do not emit visible light; they are detected through their gravitational effects and the radiation from material falling into them.
Option A accurately reflects current astronomical understanding, as evidence shows the universe is expanding due to the redshift of distant galaxies. Option B is incorrect; while the Milky Way is large, it contains only a small fraction of the universe's stars, which are spread across billions of galaxies. Option C is misleading; stars undergo significant changes in size, temperature, and composition throughout their life cycles, particularly during phases like red giant or supernova. Option D is also false; black holes do not emit visible light; they are detected through their gravitational effects and the radiation from material falling into them.
Which of the following is a true statement about sodium chloride (NaCl)?
- A. It is a gas at room temperature.
- B. It is a compound formed from two elements.
- C. It is a mixture formed from two different compounds.
- D. It is an element that is unstable and reactive.
Correct Answer & Rationale
Correct Answer: B
Sodium chloride (NaCl) is indeed a compound formed from two elements: sodium (Na) and chlorine (Cl), which combine in a fixed ratio through ionic bonding. Option A is incorrect; NaCl is a solid at room temperature, not a gas. Option C misrepresents NaCl as a mixture, but it is a pure compound, not formed from different compounds. Option D inaccurately describes NaCl as an element; it is a stable compound, not unstable or reactive under normal conditions. Thus, option B accurately reflects the nature of sodium chloride.
Sodium chloride (NaCl) is indeed a compound formed from two elements: sodium (Na) and chlorine (Cl), which combine in a fixed ratio through ionic bonding. Option A is incorrect; NaCl is a solid at room temperature, not a gas. Option C misrepresents NaCl as a mixture, but it is a pure compound, not formed from different compounds. Option D inaccurately describes NaCl as an element; it is a stable compound, not unstable or reactive under normal conditions. Thus, option B accurately reflects the nature of sodium chloride.
Which of the following was the dependent variable in this investigation?
- A. The wingspan
- B. The flight distance
- C. The stopwatch
- D. The tape measure
Correct Answer & Rationale
Correct Answer: B
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.