2026 Earth Science and Environmental Pollution Complete Practice Exam

A mutualistic relationship exists here: both partners benefit. Zooxanthellae are photosynthetic algae living in coral tissues; they supply the coral with sugars and other nutrients produced through photosynthesis, fueling coral growth and reef-building. In return, the coral provides a protected habitat and access to waste products like carbon dioxide and nitrogen compounds that the algae use for growth. This energy-sharing arrangement is especially important in nutrient-poor tropical waters. If the relationship were parasitic, the algae would harm the coral; if it were commensal, the coral wouldn’t gain a benefit; and if it were predatory, one organism would exploit the other.