The sea urchin Diadema antillarum is a major grazer (herbivore) on Caribbean cor
ID: 47469 • Letter: T
Question
The sea urchin Diadema antillarum is a major grazer (herbivore) on Caribbean coral reefs. In the early 1980s, urchin populations throughout the region were infected with a disease that caused 95-99% mortality in many locales. Scientists hypothesized that the loss of urchins could have significant effects on the structure of local coral reef communities (including corals, algae, and associated invertebrates and fish). In the 1990s, they re-sampled a number of different coral reefs on the north coast of Jamaica that had previously been sampled in the 1970s. Consider the following figure:
What does each open circle on the graph represent?
Percent algal cover
Percent coral cover
A reef sampled in the 1970s
A reef sampled in the 1990s
What does each solid circle on the graph represent?
Percent algal cover
Percent coral cover
A reef sampled in the 1970s
A reef sampled in the 1990s
What is/are the independent variable(s)?
Percent algal cover
Percent coral cover
Percent algal and coral cover
Time
The variable ?time? in this study is
Numerical and continuous
Numerical and discrete
Categorical and nominal
Categorical and ordinal
The variable ?percent coral cover? in this study is
Numerical and continuous
Numerical and discrete
Categorical and nominal
Categorical and ordinal
How did coral reef communities change after the urchin die-off?
From algal- to coral-dominated
From coral- to algal-dominated
Did not change
Cannont be determined
100 1990s Jamaican Coral Reefs 60 1970s C o 1970s 0 20 40 680 100 Percent coral cover 0Explanation / Answer
1. reef sampled in 1970.
2. reef sampled in 1990.
3. percent algal and coral cover.
4. numerical and discrete.
5. numerical and discrete
6 from algal to coral dominated