Introduction of aquatic life
Aquatic life are plants, animals, and other organisms that live in the salt water of seas or oceans or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the Earth. Marine organisms, mostly microbes, produce oxygen and sequester carbon. Aquatic life, in part, shapes and protects coastlines, and some marine life even helps create new land (e.g., building coral reefs).
Many life forms originally evolved in marine habitats. By volume, oceans provide about 90% of Earth’s living space. The first vertebrates appeared in the form of fish, which live only in water. Some of these evolved into amphibians, which spend part of their lives in water and part on land. One group of amphibians evolved into reptiles and mammals, and several subsets of each returned to the ocean as sea snakes, sea turtles, seals, manatees, and whales. Plant forms such as kelp and other algae grow in water and form the basis of some underwater ecosystems. Plankton form the general base of the ocean food chain, especially phytoplankton, which are major primary producers.
Aquatic ecosystem
Marine ecosystems
Freshwater ecosystems
Marine ecosystems
Marine ecosystems are the largest of Earth’s aquatic ecosystems and exist in waters with high salinity content. These systems contrast with freshwater ecosystems that have a low salt content. Marine waters cover more than 70% of the Earth’s surface and contribute more than 97% of the Earth’s water supply and more than 90% of the Earth’s habitable space. The average salinity of sea water is 35 parts per thousand of water. Actual salinity varies between different marine ecosystems. Marine ecosystems can be divided into many zones based on water depth and shoreline characteristics. The oceanic zone is the large open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of the substrata below the water, where most invertebrates live. The intertidal zone is the area between high and low tide. Other nearshore (neritic) zones may include mudflats, seagrass beds, mangroves, rocky intertidal systems, salt marshes, coral reefs, and lagoons. In deep water, hydrothermal vents can form when chemical-synthesizing sulfur bacteria form the base of the food web.
Freshwater ecosystems
Freshwater ecosystems are a subset of Earth’s aquatic ecosystems. They include lakes, ponds, rivers, streams, springs, marshes, and wetlands. They are interchangeable with marine ecosystems that have a large salt content. Freshwater habitats can be classified by a variety of factors, including temperature, light penetration, nutrients, and vegetation. There are three basic types of freshwater ecosystems: lentic (slow-moving water, including pools, ponds, and lakes), lotic (fast-moving water, for example streams and rivers), and wetlands (areas where the soil is at least saturated or inundated over time). part). Freshwater ecosystems contain 41% of the world’s known fish species.
Microorganisms
Microorganisms make up about 70% of marine biomass. A microbe is a microscopic organism that is too small to be detected by the naked eye. It can be unicellular or multicellular. Microorganisms are diverse and include all bacteria and archaea, algae, many protozoa such as fungi, and certain microscopic animals such as rotifers. Many macroscopic animals and plants have microscopic juvenile stages. Some microbiologists also classify viruses (and viroids) as microorganisms, but others consider these to be non-living.
Marine viruses
Viruses are small infectious agents that lack their own metabolism and can only replicate in the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. The linear size of a typical virus is about one-hundredth that of a typical bacterium. Many viruses cannot be seen with an optical microscope, so electron microscopes are used instead.
Marine bacteria
Bacteria are a large domain of prokaryotic microorganisms. Usually a few micrometers long, bacteria have a number of shapes, from spheres to rods and spirals. Bacteria are among the first life forms to appear on Earth and are present in many of its habitats. The bacteria inhabit soil, water, acidic hot springs, radioactive waste, and deep parts of the Earth’s crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals.
Origin of animals
The first animals were marine invertebrates, followed by vertebrates. Animals are multicellular eukaryotes distinguishable from plants, algae, and fungi by their lack of cell walls. Marine invertebrates are animals other than vertebrate members of the chordate phylum that inhabit marine environments. Invertebrates do not have a vertebral column. Some have evolved a shell or a hard exoskeleton.
The earliest animal fossils may belong to the genus Dickinsonia, dating from 571 to 541 million years ago. An individual Dickinsonia usually resembles a bilaterally symmetrical ribbed oval. They continued to grow until they were covered in sediment or otherwise killed, spending most of their lives with their bodies firmly anchored to the sediment. Although their taxonomic relationships are currently unknown, their mode of development is consistent with a bilateral relationship.
Vertebrate animals
Vertebrates are a subphylum of chordates. They are chordates that have a vertebral column. The vertebral column provides the central supporting structure for an internal skeleton that gives shape, support, and protection to the body and may provide a means of anchoring fins or limbs to the body. The vertebral column also serves to protect the spinal cord located within the vertebral column.
Marine vertebrates can be divided into
- marine fishes
- marine tetrapods.
Marine fishes
Fish usually breathe by taking in oxygen from the water through gills, and their skin is protected by scales and mucus. They use fins to move and stabilize themselves in water and typically have a two-chambered heart and eyes well adapted for underwater vision as well as other sensory systems. As of 2017, over 33,000 species of fish have been described, of which about 20,000 are marine fish.
Marine tetrapods
A tetrapod is a vertebrate with limbs (feet). Tetrapods evolved from ancient lobe-finned fish about 400 million years ago during the Devonian period, when their earliest ancestors emerged from the sea and adapted to live on land. This change from a body plan for gravity-neutral water breathing and navigation to a body plan with mechanisms for the animal to breathe air without dehydrating and move on land is one of the most profound evolutionary changes known. Tetrapods can be divided into four groups: amphibians, reptiles, birds, and mammals.
Author By :Samindya Rathnaweera