Professor Middlebrain Notes That Rats in the First 10 Cages

question 94

Multiple Choice

Professor Middlebrain notes that rats in the first 10 cages, which were injected with salt water, are calm. Rats in the last 10 cages, which were injected with distilled water, are aggressive. He concludes that salt decreases aggressiveness. What is wrong with this study?

• A) lack of random assignment
• B) lack of an independent variable
• C) lack of a dependent variable
• D) presence of demand characteristics

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Definitions:

Character Displacement

An evolutionary phenomenon where species that compete for similar resources evolve differences, reducing competition.

Interference Competition

A form of competition where organisms directly interact with each other to access resources, often by physically preventing their rivals from exploiting those resources.

Coevolution

The joint evolution of two closely interacting species; macroevolutionary pattern in which each species is a selective agent for traits of the other.

Intermediate Disturbance Hypothesis

Species richness is greatest in communities in which disturbances are moderate in their magnitude and frequency.