BIOLOGY OF CORAL REEFS Chapter 2 Objectives Diversity of Life on Coral Reefs How does species diversity on coral reefs compare with that of other ecosystems Life on coral reefs is more diverse than in any other ecosystem on Earth How is information about the many tens of thousands of species that live on reefs organized so we can readily retrieve it Information is facilitated by international agreement on a hierarchical system of categories based on evolutionary relationships among organisms In this nomenclatural system the fundamental evolutionary unit is the species commonly defined as a group of organisms capable of reproducing with eachother Similar species descended from a common ancestor are grouped together in a genus Every species known is uniquely designated by a two part scientific name consisting of the genus and the species Genera plural of genus are grouped with other closely related genera into families which are grouped into orders Related orders are grouped together into classes which are grouped with related classes into phyla for animals or divisions for plants Phyla or divisions are grouped together into kingdoms or domains What characteristics contribute to the most fundamental division of life into prokaryotes and eukaryotes All cells fit into two categories prokaryotes and eukaryotes Prokaryote cells are very small and very simple They have circular DNA molecules and no membranes organizing different functions within each cell they are the earliest forms of life Prokaryotes do not form multi cellular organisms Divided into two domains Bacteria and Archaea Eukaryote cells are much larger and more complex Every eukaryote cell contains organelles miniature versions of our organ systems All eukaryotes are included in one domain Eukaryota which is divided into four kingdoms One kingdom includes only single celled organisms protists and the other three the multicellular organisms fungi plants animals What is the importance of the Cyanobacteria to coral reefs Cyanobacteria or photosynthetic organisms that contribute to primary production generation of sugars and oxygen by photosynthesis How are the 4 kingdoms of eukaryotes distinguished from each other One kingdom includes only single celled organisms protists and the other three multicellular organisms fungi plants animals Protists consist of a single cell Plantae Multicellular plants that are set apart from animals by their ability to manufacture their own food using basic materials such as energy carbon dioxide and water Animalia Multicellular animals that are unable to manufacture their own food by photosynthesis What are the important differences among the photosynthetic eukaryotic organisms division Dinoflagellida in the kingdom Protista and all divisions in the kingdom Plantae in where they live in the sea and how they acquire nutrients Dinoflagellates protists thrive in warm waters some live suspended in seawater while others live as zooxanthellae in cnidarian and sponge tissues Chlorophyta the green algae tends to live in shallow water in order to absorb redlight wavelengths to gain energy for photosynthesis Rhodophyta the red algae collect energy from green violet and blue wavelengths which penetrate deeper in the water than red wavelengths Red algae therefore live much deeper than green algae Phaephyta the brown algae inhabit cold nutrient rich water Magnoliophyta the flowering plants vast majority live on land generally rooted in the ground so that they can soak up nutrients Fertilization in these flowering plants results in seeds which serves as its food supply What are the chief distinguishing characteristics of each of the 6 phyla of invertebrate animals and the phylum with both invertebrate and vertebrate animals that are conspicuously represented on coral reefs e g symmetry appendages skeletons or other structural support and adaptations for acquiring food And what variations on their basic body plan have evolved in each of these phyla Porifera sponges filled with a variety of cells that are able to move freely thoughout the body and specialize into different kinds of cells as needed The surface is perforated by many tiny holes through which water enters as well as large holes through which the water leaves Unique in ability to filter out very tiny particles including bacteria and so they play the role of cleaning the water column Food is captured and digested by individual cells as they have no digestive system or any other organized system One of the most successful groups on coral reefs in number of species Produce potent defensive chemicals Cnidaria sea anemones corals jellyfish fire corals hydroids All cnidarians have a simple design involving a mouth ringed with tentacles that opens into a sac like gut Stun subdue prey using tentacles Annelida segmented worms wide variety of feeding and lifestyles among segmented worms Some worms roam freely with great jaws for sawing algae others live head down in the mud continuously swallowing sediments others slither through mud capturing prey with fangs and still others cement themselves to corals and use fans of feathery appendages to filter food from the water Some species of worm evade predators by hiding in tubes while others bristle worms are covered with toxin filled bristles Mollusca clams oysters scallops snails squids octopuses All molluscs share soft body mass and a muscular foot Many but not all molluscs have protective shells Molluscs that do not have protective shells use other methods for protection Sea slugs for example produce toxic chemicals similar to acid Others such as squids cuttlefish and octopuses use speed to avoid predators Arthropoda crabs lobsters shrimps barnacles have jointed legs and external skeletons Many of these crustaceans rely on hiding to avoid predators Echinodermata sea urchins starfish sea lilies sea cucumbers brittle stars different from all other groups in having pentaradial symmetry meaning each individual can be divided like a pie into five equal portions All members of this phylum have hard calcareous plates embedded in their skins imparting different degrees of rigity to the animals All echinoderms move and grasp the bottom and prey with tiny transparent extensions with suction disks on the ends called tube feet Each ehinoderm group feeds in a unique way Chordata sea squirts fish turtles birds mammals Members of this phylum vary greatly sea squirts use toxic chemicals to protect themselves from predators
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