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Almost all aquatic animals reproduce in water, either oviparously or viviparously, and many species routinely migrate between different water bodies during their life cycle. Some animals have fully aquatic life stages (typically as eggs and larvae), while as adults they become terrestrial or semi-aquatic after undergoing metamorphosis.
Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton. The earliest animal fossils may belong to the genus Dickinsonia, [183] 571 million to 541 million years ago. [184]
Wading and bottom-feeding animals (e.g. moose and manatee) need to be heavier than water in order to keep contact with the floor or to stay submerged, surface-living animals (e.g. otters) need the opposite, and free-swimming animals living in open waters (e.g. dolphins) need to be neutrally buoyant in order to be able to swim up and down the ...
Animals are multicellular eukaryotes, [note 1] and are distinguished from plants, algae, and fungi by lacking cell walls. [1] Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton.
Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea.Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy.
More elaborate exhibits contain deep pools that can be viewed underwater with rock-mimicking cement as haul-out areas. The most common pinniped species kept in captivity is the California sea lion as it is abundant and easy to train. [153] These animals are used to perform tricks and entertain visitors. [154]
Sea turtles are largely solitary animals, though some do form large, though often loosely connected groups during nesting season. Although only seven turtle species are truly marine, many more dwell in brackish waters. [1] [6] Sea snakes: the most abundant of the marine reptiles, there are over 60 different species of sea snakes.
The types of marine pollution can be grouped as pollution from marine debris, plastic pollution, including microplastics, ocean acidification, nutrient pollution, toxins and underwater noise. Plastic pollution in the ocean is a type of marine pollution by plastics , ranging in size from large original material such as bottles and bags, down to ...