ASU BIO320
FUNDAMENTALS OF
ECOLOGY EXAM 3
PRACTICE
Question 1: In a four-level food chain of grass -> grasshopper -> lizard -> hawk, which organism is the secondary consumer?
Choices:
1) Grass 2) Grasshopper 3) Lizard 4) Hawk
Correct Answer: Lizard
Explanation: The grasshopper is the primary consumer because it eats the producer. The lizard eats the primary consumer, so it is the secondary consumer; the hawk is the tertiary consumer.Page 1
Question 2: A predator population increases its per-capita prey consumption as
prey density rises, but consumption eventually levels o� because handling time limits feeding. Which functional response best describes this pattern?
Choices:
1) Type II 2) Type III 3) Density-independent response 4) Type I
Correct Answer: Type II
Explanation: A Type II functional response rises quickly with prey density and then saturates because predators become limited by handling and processing time.
Question 3: A coastal predator is removed experimentally. Its herbivorous prey
becomes more abundant, and algal biomass subsequently declines. Which interpretation best �ts these results?
Choices:
1) Primary succession 2) A bottom-up nutrient cascade 3) Competitive release among algae only 4) A top-down trophic cascade
Correct Answer: A top-down trophic cascade
Explanation: Removing the predator releases herbivores from predation. More herbivory then reduces algal biomass, which is a classic top-down trophic cascade.Page 2
Question 4: A plant exposed to leaf-chewing insects increases production of
defensive chemicals only after damage occurs. This response is best described as which type of defense?
Choices:
1) Constitutive defense 2) Induced defense 3) Apparent competition 4) Resource partitioning
Correct Answer: Induced defense
Explanation: An induced defense is activated or strengthened after herbivore attack.Constitutive defenses are maintained before damage occurs.
Question 5: For species 1 in a Lotka-Volterra competition model, K1 = 100 and
alpha12 = 0.5. If species 2 is held at N2 = 80, at what N1 does species 1 have zero net population growth?
Choices:
1) 60 2) 40 3) 80 4) 20
Correct Answer: 60
Explanation: Species 1 has zero growth when N1 + alpha12N2 = K1. Therefore N1 + 0.5 = 100, so N1 = 60.Page 3