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Chapter 2- The Diving Environment The Diving Environment 49 Diving in the vicinity of dams is also discouraged because strong currents can literally grab and hold you underwater. You could also be swept through an overflow channel. BIOLOGICAL ASPECTS One of the most interesting aspects of the diving environment is the wide variety of living plants and animals that can be seen. Your diving will be more enjoyable if you know more about the aquatic life you encounter. Identification One of the primary divisions of animals and plants is the phylum. Each phylum is divided into a number of classes, which are further divided into orders, and the orders into families. Each family contains still smaller groups, each of which is called a genus. Finally, the genus is followed by one or more species. An organism’s scientific name actually describes the life form and consists of the genus and species which is usually derived from either Latin or Greek. Classifications are keyed externally to such features as color, scales, shape, skeleton, etc. Ecological Overview Ecology is the scientific study of organisms in relation to their environments. Animals and plants occupy certain regions within a major environment, such as the ocean or a specific sea. The precise “micro-environment” of a species is called its habitat. Within any habitat there are different species each with their own feeding habits and reproductive rates. The position each species occupies in its habitat is called its niche. Niches of various species are determined by physical factors as well as relationships to other species in the same habitat. Thus, the niches of species in a habitat are adjusted to each other and form an integrated community. You might notice a number of species of fish living in the same kelp forest or coral reef. They have separate niches based on what they eat (prey), when they feed, and what type of space they occupy. Communities react to the non-living parts of the environment, and vice-versa, to form a balanced ecosystem. An example of a balanced ecosystem is a coral reef. Coral polyps secrete carbonates (limestone), which are bound together by calcareous algae. When man alters such a natural environment by fishing, hunting, anchoring, or polluting; this initial disturbance of the animals and plants may eventually disturb the entire ecosystem and eventually alter or destroy it. Oceanic Life Zones There are four basic plant and animal life zones in the ocean: • Intertidal or littoral - Plants and animals in the region between high and low tides are adapted to withstand water loss, temperature extremes, and strong water movement. • Planktonic - Drifting and floating forms that are at the mercy of the wind and current. Many animals have planktonic stages in their life cycles. The most common “plants” in the oceans are the phytoplankton, which are algae that use sunlight to produce carbohydrates. They represent the basic food source for all life in the oceans. • Nektonic - These are free-swimming forms, including fish, which rely on speed and streamlining for their survival. Some live at a constant depth in one area, while others prefer the open seas. Fish may live in schools for greater chance of survival. • Benthic - These are bottom-dwelling organisms such as clams, anemones, and seastars. They can live on all types of bottoms, including rock, sand, or mud. Marine and Fresh Water Plants In contrast to land plants such as grasses, shrubs, and trees; most underwater plants lack a root system, do not require strong, woody limbs for support, and do not need a network of vessels to carry water to other parts of


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