Marine Zoology Cheat Sheet

The core ideas of Marine Zoology distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/marine-zoology/cheatsheet

Quick Reference

Marine Food Webs

The complex networks of feeding relationships in ocean ecosystems, beginning with primary producers such as phytoplankton and passing energy through successive trophic levels to herbivorous zooplankton, small fish, larger predators, and apex predators.

Osmoregulation

The physiological process by which marine animals maintain the balance of water and dissolved salts in their body fluids despite living in a hypertonic (saltwater) or variable-salinity environment.

Bioluminescence

The production and emission of light by living organisms through chemical reactions, most commonly involving the substrate luciferin and the enzyme luciferase. It is widespread among deep-sea marine animals.

Coral Reef Ecology

The study of the biological communities associated with coral reefs, which are calcium carbonate structures built primarily by colonial scleractinian corals harboring photosynthetic zooxanthellae. Coral reefs support roughly 25 percent of all marine species.

Pelagic Zonation

The vertical division of the open ocean water column into distinct depth zones, each characterized by different levels of light, temperature, and pressure: epipelagic (0-200 m), mesopelagic (200-1,000 m), bathypelagic (1,000-4,000 m), abyssopelagic (4,000-6,000 m), and hadopelagic (below 6,000 m).

Marine Mammal Echolocation

The biological sonar used by toothed whales (odontocetes) and some pinnipeds to navigate and locate prey by emitting high-frequency clicks and interpreting the returning echoes.

Benthic Communities

Assemblages of organisms that live on or in the ocean floor (the benthos), including sessile filter feeders, burrowing infauna, and mobile epifauna. Benthic habitats range from intertidal mudflats to hydrothermal vents.

Larval Dispersal and Settlement

The process by which many marine invertebrates and fishes reproduce by releasing planktonic larvae that drift with ocean currents before metamorphosing and settling into adult habitats, a strategy that allows colonization of new areas.

Trophic Cascades

Indirect ecological effects that ripple through a food web when the population of a top predator changes, causing reciprocal shifts in the abundance of organisms at lower trophic levels.

Ocean Acidification

The ongoing decrease in ocean pH caused by the absorption of atmospheric carbon dioxide, which reacts with seawater to form carbonic acid. This reduces the availability of carbonate ions needed by many marine animals to build shells and skeletons.

Key Terms at a Glance

Abyssal Plain:The vast, flat area of the deep ocean floor, typically between 3,000 and 6,000 meters depth, characterized by fine sediment and low biodiversity compared to other benthic habitats.

Baleen:Keratinous plates that hang from the upper jaw of mysticete whales, used to filter small prey such as krill and small fish from large volumes of seawater.

Benthic:Relating to the bottom of a body of water or the organisms that live on or in the seafloor substrate.

Bioluminescence:The production and emission of light by a living organism through a chemical reaction, typically involving luciferin and luciferase.

Bycatch:Non-target species unintentionally caught during commercial fishing operations, including marine mammals, sea turtles, seabirds, and juvenile fish.

Cetacean:Any member of the order Cetacea, the group of fully aquatic marine mammals that includes whales, dolphins, and porpoises.

Chemosynthesis:The biological process by which organisms produce organic molecules using chemical energy from inorganic compounds such as hydrogen sulfide, rather than sunlight.

Chromatophore:A pigment-containing cell in cephalopods and other marine animals that can expand or contract to rapidly change skin color and pattern for camouflage or communication.

Cnidocyte:A specialized stinging cell unique to cnidarians (jellyfish, corals, anemones) that contains a nematocyst used for prey capture and defense.

Coral Bleaching:The loss of symbiotic zooxanthellae from coral tissue due to environmental stress (especially elevated temperatures), causing the coral to turn white and potentially die.

Echolocation:A biological sonar system used by toothed whales to navigate and detect prey by emitting sound pulses and interpreting the returning echoes.

Elasmobranch:A subclass of cartilaginous fishes including sharks, rays, and skates, characterized by cartilaginous skeletons, multiple gill slits, and dermal denticles.

Epipelagic Zone:The uppermost layer of the open ocean (0-200 m), also called the sunlit or photic zone, where sufficient light penetrates for photosynthesis.

Eutrophication:Excessive nutrient enrichment of a water body, often from agricultural runoff, leading to algal blooms, oxygen depletion, and dead zones harmful to marine animals.

Filter Feeding:A feeding strategy in which animals strain food particles from water, used by organisms ranging from sponges and bivalves to baleen whales and whale sharks.

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