Some species even starve to death as their main source of food goes extinct. Rich biodiversity thus helps in the process of food chain. We eat different kinds of fruits, vegetables, meats, fishes and other things as they satisfy different nutritional needs for the proper functioning of our body. The decline in the variety of plants and animals would mean the decline in the variety of food we eat and this is likely to result in nutritional deficiencies.
Trees and plants inhale carbon dioxide and other harmful gases from the atmosphere and exhale the life giving oxygen. Some plants and trees have a greater ability to purify the air and keep the atmosphere clean. The decline in the number and types of trees and plants can impact the quality of air negatively. Many insects, organisms and microorganisms such as earthworms, fungi and bacteria work on different levels and make the soil fertile and maintain its health. Healthy and fertile soil is certainly better for the cultivation of crops.
Loss of such species can thus be a great loss for us. Many species of trees and plants are used to derive different medicines to cure various diseases. Many plants serving medicinal purposes have gone extinct in the past and many others are likely to go extinct even before the scientists discover their utility. Thus, the richness of biodiversity is essential for the survival of living beings on Earth.
The Future of Biodiversity in India Essay
This issue must be taken up seriously and stern measures must be taken to conserve biodiversity. The need for conservation of biodiversity has been stressed upon numerous times as it is of utmost importance for the survival of the mankind and other living beings on Earth. In addition to emphasizing upon the importance and need to protect and conserve biodiversity, it is essential to share the methods to conserve it.
One of the reasons why biodiversity is declining is because of the growing human population. Trees are being cut and animals are being harmed at a large scale in order to satiate various human needs. The greater the population the higher the needs which would result in further exploitation of flora and fauna and decline in biodiversity.
The first and foremost thing that needs to be done for the conservation of biodiversity is to control human population and allow other species of plants and animals to thrive on our planet. The growing pollution is causing harm to our beautiful planet. The temperature is rising and subsequently causing global warming. The changing climate, deteriorating air quality and the growing amount of pollution on land and in water bodies is leading to different types of diseases in many species and has also caused the extinction of several of them. Many species of flora and fauna are unable to withstand these changes in the atmosphere and it becomes extremely difficult for them to survive.
It is essential to cut down on the activities leading to pollution in order to lower it. Forests are a habitat for different varieties of flora and fauna. Deforestation has been one of the main reasons for the extinction of numerous wild creatures as well as various beautiful plants. The loss of habitat makes wild animals vulnerable. They are unable to survive in the new environment.
While some struggle for survival by shifting to other places others are unable to adapt to new surroundings and die. It is imperative for us to avoid wastage of any kind. Most of the things we use are derived from natural resources. From the electricity we consume, to the fuel we use, from the clothes we wear to the paper we write on, everything has been prepared directly or indirectly from the natural resources. We need to understand that natural resources are not only essential for us but are also vital for the survival of other species. We must thus utilise only as much as we require so that these remain available in abundance in the nature for future use.
Apart from this, one of the best methods to conserve biodiversity is by spreading awareness. People need to be sensitized about the issue so that they act responsibly and contribute towards conserving biodiversity. The government can do so at a bigger level while we can spread awareness by word of mouth and through social media.
Conservation of biodiversity is extremely important to maintain a healthy environment and ensure a comfortable life for future generations. There are many ways in which we can conserve it. We must all contribute our bit towards conserving the same. There are a number of ways in which the richness of biodiversity helps in maintaining the ecological system and serves us. Different kind of foods available fulfils different nutritional needs, plants clean the air, many organisms keep the soil health in check and survival of different species is possible due to the process of food chain.
These are some of the examples to show the importance of conserving biodiversity on Earth. The continual decline in biodiversity has become a cause of concern world over. Many regions in the world have seen a major dip in the biodiversity owing to the changes in climate and increasing pollution levels.
This has had a big impact on the other species living in those areas. Biodiversity is declining world over. Research shows that numerous varieties of animals go extinct each year largely due to human activities. Apart from these many species of plants and trees including Lepidodendron, Araucaria Mirabilis, Wood Cycad and Kokia Cookei have gone extinct and many others are endangered. If we continue to lose different species of flora and fauna at this speed, our survival will become extremely difficult on Earth. This is because every species of plant and animal either big or small, contributes towards the maintenance of the ecological balance in its own unique way.
Loss of these can have a huge impact on the environment as well as other living beings. For instance, we depend on different kind of plants and animals as they serve as a source of food for us. They satisfy different nutritional needs. Trees provide wood and other raw material that are used to craft numerous things that are vital for us. Similarly, different kinds of herbs are used for preparing medicines. Likewise, different species of insects and animals contribute in their own way in making the environment fit for living. If this richness of diversity is not maintained we shall lose out on many things and it will make our life difficult.
This is why it is extremely important to conserve biodiversity. We as general public can help in the conservation of biodiversity by avoiding wastage of the natural resources. They are the largest non-colonial animals to swim with the help of cilia hairs or combs. The phylum has about known species with a wide range of body forms.
Sizes range from a few millimeters to 1. Cydippids are egg-shaped with their cilia arranged in eight radial comb rows, and deploy retractable tentacles for capturing prey. The benthic platyctenids are generally combless and flat. The coastal beroids have gaping mouths and lack tentacles. Most adult ctenophores prey on microscopic larvae and rotifers and small crustaceans but beroids prey on other ctenophores. Group of small benthic creeping comb jellies streaming tentacles and living symbiotically on a starfish.
The beroid ctenophore, mouth gaping at left, preys on other ctenophores. The sea walnut has a transient anus which forms only when it needs to defecate . Light diffracting along the comb rows of a cydippid, left tentacle deployed, right retracted. Deep-sea ctenophore trailing tentacles studded with tentilla sub-tentacles.
Early writers combined ctenophores with cnidarians. Ctenophores resemble cnidarians in relying on water flow through the body cavity for both digestion and respiration, as well as in having a decentralized nerve net rather than a brain. Also like cnidarians, the bodies of ctenophores consist of a mass of jelly, with one layer of cells on the outside and another lining the internal cavity. In ctenophores, however, these layers are two cells deep, while those in cnidarians are only a single cell deep.
While cnidarians exhibit radial symmetry , ctenophores have two anal canals which exhibit biradial symmetry half-turn rotational symmetry. Placozoa from Greek for flat animals have the simplest structure of all animals. They are a basal form of free-living non-parasitic multicellular organism. The first species was discovered in , the classical Trichoplax adhaerens. Like the amoebae they superficially resemble, they continually change their external shape.
In addition, spherical phases occasionally form which may facilitate movement. Trichoplax lacks tissues and organs. There is no manifest body symmetry, so it is not possible to distinguish anterior from posterior or left from right. It is made up of a few thousand cells of six types in three distinct layers. Cnidarians from Greek for nettle are distinguished by the presence of stinging cells , specialized cells that they use mainly for capturing prey.
Cnidarians include corals , sea anemones , jellyfish and hydrozoans. They form a phylum containing over 10,  species of animals found exclusively in aquatic mainly marine environments. Their bodies consist of mesoglea , a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. They have two basic body forms: swimming medusae and sessile polyps , both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration.
Fossils of cnidarians that do not build mineralized structures are rare.
Scientists currently think cnidarians, ctenophores and bilaterians are more closely related to calcareous sponges than these are to other sponges , and that anthozoans are the evolutionary "aunts" or "sisters" of other cnidarians, and the most closely related to bilaterians. Cnidarians are the simplest animals in which the cells are organised into tissues. Sea anemones are common in tidepools. Close up of polyps on the surface of a coral , waving their tentacles. If an island sinks below the sea, coral growth can keep up with rising water and form an atoll.
The mantle of the red paper lantern jellyfish crumples and expands like a paper lantern . The Portuguese man o' war is a colonial siphonophore. Marrus orthocanna another colonial siphonophore, assembled from two types of zooids. Porpita porpita consists of a colony of hydroids . Lion's mane jellyfish , largest known jellyfish . Turritopsis dohrnii achieves biological immortality by transferring its cells back to childhood  . The sea wasp is the most lethal jellyfish in the world . Some of the earliest bilaterians were wormlike, and a bilaterian body can be conceptualized as a cylinder with a gut running between two openings, the mouth and the anus.
Around the gut it has an internal body cavity, a coelom or pseudocoelom. Having a front end means that this part of the body encounters stimuli, such as food, favouring cephalisation , the development of a head with sense organs and a mouth. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells.
However, there are exceptions to each of these characteristics; for example, adult echinoderms are radially symmetric unlike their larvae , and certain parasitic worms have extremely simplified body structures. The original bilaterian may have been a bottom dwelling worm with a single body opening. Protostomes from Greek for first mouth are a superphylum of animals. It is a sister clade of the deuterostomes from Greek for second mouth , with which it forms the Nephrozoa clade.
Protostomes are distinguished from deuterostomes by the way their embryos develop. In protostomes the first opening that develops becomes the mouth , while in deuterostomes it becomes the anus. Scalidophora penis worms and mud dragons. Worms Old English for serpents form a number of phylums. Different groups of marine worms are related only distantly, so they are found in several different phyla such as the Annelida segmented worms , Chaetognatha arrow worms , Phoronida horseshoe worms , and Hemichordata.
All worms, apart from the Hemichordata, are protostomes. The Hemichordata are deuterostomes and are discussed in their own section below. The typical body plan of a worm involves long cylindrical tube-like bodies and no limbs. Marine worms vary in size from microscopic to over 1 metre 3. Many of these worms have specialized tentacles used for exchanging oxygen and carbon dioxide and also may be used for reproduction.
Some marine worms are tube worms , such as the giant tube worm which lives in waters near underwater volcanoes and can withstand temperatures up to 90 degrees Celsius. Platyhelminthes flatworms form another worm phylum which includes a class of parasitic tapeworms. Nematodes roundworms constitute a further worm phylum with tubular digestive systems and an opening at both ends. It has been estimated another million remain undescribed.
They are found in every part of the earth's lithosphere , from the top of mountains to the bottom of oceanic trenches. Giant tube worms cluster around hydrothermal vents. Nematodes are ubiquitous pseudocoelomates which can parasite marine plants and animals. Bloodworms are typically found on the bottom of shallow marine waters. Molluscs Latin for soft form a phylum with about 85, extant recognized species. They are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The mollusc phylum is divided into 9 or 10 taxonomic classes.
These classes include gastropods , bivalves and cephalopods , as well as other lesser-known but distinctive classes. Gastropods with protective shells are referred to as snails , whereas gastropods without protective shells are referred to as slugs. Gastropods are by far the most numerous molluscs in terms of species. There are about 8, marine bivalves species including brackish water and estuarine species. A deep sea ocean quahog clam has been reported as having lived years  making it the longest recorded life of all animals apart from colonial animals, or near-colonial animals like sponges.
Marine gastropods are sea snails or sea slugs. This nudibranch is a sea slug. Molluscs usually have eyes. Bordering the edge of the mantle of a scallop , a bivalve mollusc, can be over simple eyes. Common mussel , another bivalve. Cephalopods include octopus , squid and cuttlefish. About living species of marine cephalopods have been identified,  and an estimated 11, extinct taxa have been described. The nautilus is a living fossil little changed since it evolved million years ago as one of the first cephalopods.
Reconstruction of an ammonite , a highly successful early cephalopod that appeared mya. Cephalopods, like this cuttlefish , use their mantle cavity for jet propulsion. Colossal squid , largest of all invertebrates . Molluscs have such diverse shapes that many textbooks base their descriptions of molluscan anatomy on a generalized or hypothetical ancestral mollusc. This generalized mollusc is unsegmented and bilaterally symmetrical with an underside consisting of a single muscular foot.
Beyond that it has three further key features. Firstly, it has a muscular cloak called a mantle covering its viscera and containing a significant cavity used for breathing and excretion. A shell secreted by the mantle covers the upper surface. Secondly apart from bivalves it has a rasping tongue called a radula used for feeding.
Thirdly, it has a nervous system including a complex digestive system using microscopic, muscle-powered hairs called cilia to exude mucus. The generalized mollusc has two paired nerve cords three in bivalves. The brain , in species that have one, encircles the esophagus. Most molluscs have eyes and all have sensors detecting chemicals, vibrations, and touch. Arthropods Greek for jointed feet have an exoskeleton external skeleton , a segmented body, and jointed appendages paired appendages. They form a phylum which includes insects , arachnids , myriapods , and crustaceans.
Arthropods are characterized by their jointed limbs and cuticle made of chitin , often mineralised with calcium carbonate. The arthropod body plan consists of segments , each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting.
Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments. The evolutionary ancestry of arthropods dates back to the Cambrian period and is generally regarded as monophyletic. However, basal relationships of arthropods with extinct phyla such as lobopodians have recently been debated. Fossil trilobite. Trilobites first appeared about Ma. They were highly successful and were found everywhere in the ocean for Ma.
The Anomalocaris "abnormal shrimp" was one of the first apex predators and first appeared about Ma. The largest known arthropod, the sea scorpion Jaekelopterus rhenaniae , has been found in estuarine strata from about Ma. It was up to 2. Horseshoe crabs are living fossils , essentially unchanged for Ma. Extant marine arthropods range in size from the microscopic crustacean Stygotantulus to the Japanese spider crab. Arthropods' primary internal cavity is a hemocoel , which accommodates their internal organs , and through which their haemolymph - analogue of blood - circulates; they have open circulatory systems.
Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus.
The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong. Many crustaceans are very small, like this tiny amphipod , and make up a significant part of the ocean's zooplankton. The Japanese spider crab has the longest leg span of any arthropod, reaching 5. The Tasmanian giant crab is long-lived and slow-growing, making it vulnerable to overfishing.
Mantis shrimp have the most advanced eyes in the animal kingdom,  and smash prey by swinging their club-like raptorial claws. Arthropod vision relies on various combinations of compound eyes and pigment-pit ocelli : in most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae bristles that project through their cuticles.
Arthropod methods of reproduction are diverse: terrestrial species use some form of internal fertilization while marine species lay eggs using either internal or external fertilization. Arthropod hatchlings vary from miniature adults to grubs that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form.
In deuterostomes the first opening that develops in the growing embryo becomes the anus , while in protostomes it becomes the mouth. Deuterostomes form a superphylum of animals and are the sister clade of the protostomes. The Saccorhytus mouth may have functioned also as its anus. Echinoderms Greek for spiny skin is a phylum which contains only marine invertebrates. The phylum contains about living species ,  making it the second-largest grouping of deuterostomes , after the chordates. Adult echinoderms are recognizable by their radial symmetry usually five-point and include starfish , sea urchins , sand dollars , and sea cucumbers , as well as the sea lilies.
They are unique among animals in having bilateral symmetry at the larval stage, but fivefold symmetry pentamerism , a special type of radial symmetry as adults. Echinoderms are important both biologically and geologically. Biologically, there are few other groupings so abundant in the biotic desert of the deep sea , as well as shallower oceans. Most echinoderms are able to regenerate tissue, organs, limbs, and reproduce asexually ; in some cases, they can undergo complete regeneration from a single limb.
Geologically, the value of echinoderms is in their ossified skeletons , which are major contributors to many limestone formations, and can provide valuable clues as to the geological environment. They were the most used species in regenerative research in the 19th and 20th centuries. Echinoderm literally means "spiny skin", as this water melon sea urchin illustrates. The ochre sea star was the first keystone predator to be studied. They limit mussels which can overwhelm intertidal communities. Sea cucumbers filter feed on plankton and suspended solids.
The sea pig , a deep water sea cucumber, is the only echinoderm that uses legged locomotion. It is held by some scientists that the radiation of echinoderms was responsible for the Mesozoic Marine Revolution. Aside from the hard-to-classify Arkarua a Precambrian animal with echinoderm-like pentamerous radial symmetry , the first definitive members of the phylum appeared near the start of the Cambrian.
Hemichordates form a sister phylum to the echinoderms. They are solitary worm-shaped organisms rarely seen by humans because of their lifestyle. They include two main groups, the acorn worms and the Pterobranchia. Pterobranchia form a class containing about 30 species of small worm-shaped animals that live in secreted tubes on the ocean floor.
Acorn worms form a class containing about species that generally live in U-shaped burrows on the seabed, from the shoreline to a depth of metres. The worms lie there with the proboscis sticking out of one opening in the burrow, subsisting as deposit feeders or suspension feeders. It is supposed the ancestors of acorn worms used to live in tubes like their relatives, the Pterobranchia, but eventually started to live a safer and more sheltered existence in sediment burrows.
Acorn worms are more highly specialised and advanced than other worm-like organisms. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have gill-like structures they use for breathing, similar to the gills of fish. Therefore, acorn worms are sometimes said to be a link between classical invertebrates and vertebrates. Acorn worms continually form new gill slits as they grow in size, and some older individuals have more than a hundred on each side. Each slit consists of a branchial chamber opening to the pharynx through a U-shaped cleft. Cilia push water through the slits, maintaining a constant flow, just as in fish.
The three-section body plan of the acorn worm is no longer present in the vertebrates, except in the anatomy of the frontal neural tube, later developed into a brain divided into three parts. This means some of the original anatomy of the early chordate ancestors is still present in vertebrates even if it is not always visible. One theory is the three-part body originated from an early common ancestor of the deuterostomes, and maybe even from a common bilateral ancestor of both deuterostomes and protostomes.
Studies have shown the gene expression in the embryo share three of the same signaling centers that shape the brains of all vertebrates, but instead of taking part in the formation of their neural system,  they are controlling the development of the different body regions. The chordate phylum has three subphylums, one of which is the vertebrates see below. The other two subphylums are marine invertebrates: the tunicates salps and sea squirts and the cephalochordates such as lancelets.
Invertebrate chordates are close relatives to vertebrates. In particular, there has been discussion about how closely some extinct marine species, such as Pikaiidae , Palaeospondylus , Zhongxiniscus and Vetulicolia , might relate ancestrally to vertebrates. The lancelet , a small translucent fish-like cephalochordate , is the closest living invertebrate relative of the vertebrates.
Tunicates, like these fluorescent-colored sea squirts , may provide clues to vertebrate and therefore human ancestry. Pyrosomes are free-floating bioluminescent tunicates made up of hundreds of individuals. Vertebrates Latin for joints of the spine are a subphylum of chordates. They are chordates that have a vertebral column backbone. The vertebral column provides the central support structure for an internal skeleton which gives shape, support, and protection to the body and can provide a means of anchoring fins or limbs to the body.
The vertebral column also serves to house and protect the spinal cord that lies within the vertebral column. Marine vertebrates can be divided into marine fish and marine tetrapods. Fish typically breathe by extracting oxygen from water through gills and have a skin protected by scales and mucous.
They use fins to propel and stabilise themselves in the water, and usually have a two-chambered heart and eyes well adapted to seeing underwater, as well as other sensory systems. Over 33, species of fish have been described as of ,  of which about 20, are marine fish. Early fish had no jaws. Most went extinct, but two groups survived: hagfish and lampreys. Hagfish form a class of about 20 species of eel -shaped, slime -producing marine fish. They are the only known living animals that have a skull but no vertebral column. Lampreys form a superclass containing 38 known extant species of jawless fish.
Although they are well known for boring into the flesh of other fish to suck their blood ,  only 18 species of lampreys are actually parasitic. Living hagfish remain similar to hagfish from around million years ago. Others consider them a sister group of vertebrates in the common taxon of craniata. Hagfish are the only known living animals with a skull but no vertebral column. Lampreys are often parasitic and have a toothed, funnel-like sucking mouth.
The extinct Pteraspidomorphi , ancestral to jawed vertebrates. Pteraspidomorphi is an extinct class of early jawless fish ancestral to jawed vertebrates. The few characteristics they share with the latter are now considered as primitive for all vertebrates. Around the start of the Devonian , fish started appearing with a deep remodelling of the vertebrate skull that resulted in a jaw. The appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in vertebrate history".
Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct during the Triassic period. Jawed fish fall into two main groups: fish with bony internal skeletons and fish with cartilaginous internal skeletons. Cartilaginous fish, such as sharks and rays , have jaws and skeletons made of cartilage rather than bone. Megalodon is an extinct species of shark that lived about 28 to 1. It looked much like a stocky version of the great white shark , but was much larger with fossil lengths reaching Cartilaginous fishes may have evolved from spiny sharks.
The manta ray , largest ray in the world, has been targeted by fisheries and is now vulnerable. Sawfish are rays with long rostrums resembling a saw. All are now endangered or critically endangered . The extinct megalodon resembled a giant great white shark. The Greenland shark lives longer than any other vertebrate. The largest extant fish, the whale shark , is now a vulnerable species. Bony fish have jaws and skeletons made of bone rather than cartilage. Bony fish also have hard, bony plates called operculum which help them respire and protect their gills, and they often possess a swim bladder which they use for better control of their buoyancy.
Bony fish can be further divided into those with lobe fins and those with ray fins. The approximate dates in the phylogenetic tree are from Near et al. Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. It has the combination of both ray-finned and lobe-finned features, although analysis of the totality of its features place it closer to lobe-finned fish. Apart from the coelacanths and the lungfishes, lobe-finned fishes are now extinct. The remaining bony fish have ray fins. These are made of webs of skin supported by bony or horny spines rays which can be erected to control the fin stiffness.
This enables them to grab prey and draw it into their mouth. Their skeletal structure has evolved towards greater lightness.
Long and Short Essay on Conservation of Biodiversity in English
While teleost bones are well calcified , they are constructed from a scaffolding of struts, rather than the dense cancellous bones of holostean fish. Teleosts are found in almost all marine habitats. Mandarin dragonet. A tetrapod Greek for four feet is a vertebrate with limbs feet. Tetrapods evolved from ancient lobe-finned fishes about million years ago during the Devonian Period when their earliest ancestors emerged from the sea and adapted to living on land. Marine tetrapods are tetrapods that returned from land back to the sea again.
The first returns to the ocean may have occurred as early as the Carboniferous Period  whereas other returns occurred as recently as the Cenozoic , as in cetaceans, pinnipeds ,  and several modern amphibians. They mostly require fresh water to reproduce. A few inhabit brackish water, but there are no true marine amphibians. Reptiles Late Latin for creeping or crawling do not have an aquatic larval stage, and in this way are unlike amphibians. As amniotes , reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land.
Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals , with some providing initial care for their hatchlings. Some reptiles are more closely related to birds than other reptiles, and many scientists prefer to make Reptilia a monophyletic group which includes the birds.
Currently, of the approximately 12, extant reptile species and sub-species, only about of are classed as marine reptiles. Except for some sea snakes, most extant marine reptiles are oviparous and need to return to land to lay their eggs. Apart from sea turtles, the species usually spend most of their lives on or near land rather than in the ocean. Sea snakes generally prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries.
The ancient Ichthyosaurus communis independently evolved flippers similar to dolphins. Some extinct marine reptiles, such as ichthyosaurs , evolved to be viviparous and had no requirement to return to land. Ichthyosaurs resembled dolphins. They first appeared about million years ago and disappeared about 90 million years ago. The terrestrial ancestor of the ichthyosaur had no features already on its back or tail that might have helped along the evolutionary process. Yet the ichthyosaur developed a dorsal and tail fin which improved its ability to swim. During the Mesozoic many groups of reptiles became adapted to life in the seas, including ichthyosaurs , plesiosaurs , mosasaurs , nothosaurs , placodonts , sea turtles , thalattosaurs and thalattosuchians.
Marine reptiles were less numerous after mass extinction at the end of the Cretaceous. Marine birds are adapted to life within the marine environment. They are often called seabirds. While marine birds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution , as the same environmental problems and feeding niches have resulted in similar adaptations.
Examples include albatross , penguins , gannets , and auks. In general, marine birds live longer, breed later and have fewer young than terrestrial birds do, but they invest a great deal of time in their young. Most species nest in colonies , which can vary in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations , crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even feed on each other. Marine birds can be highly pelagic , coastal, or in some cases spend a part of the year away from the sea entirely.
Some marine birds plummet from heights, plunging through the water leaving vapour-like trails, similar to that of fighter planes. They have air sacs under their skin in their face and chest which act like bubble-wrap , cushioning the impact with the water. European herring gull attack herring schools from above.
The first marine birds evolved in the Cretaceous period , and modern marine bird families emerged in the Paleogene. Mammals from Latin for breast are characterised by the presence of mammary glands which in females produce milk for feeding nursing their young. There are about living and recently extinct marine mammal species such as seals , dolphins , whales , manatees , sea otters and polar bears.
Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating , breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living.
Their diet varies considerably as well: some may eat zooplankton ; others may eat fish, squid, shellfish, and sea-grass; and a few may eat other mammals. In a process of convergent evolution , marine mammals, especially cetaceans redeveloped their body plan to parallel the streamlined fusiform body plan of pelagic fish. Front legs became flippers and back legs disappeared, a dorsal fin reappeared and the tail morphed into a powerful horizontal fluke.
This body plan is an adaptation to being an active predator in a high drag environment. A parallel convergence occurred with the now extinct marine reptile ichthyosaur. Endangered blue whale , largest animal ever . Bottlenose dolphin , highest encephalization of any animal after humans . Dugong grazing on seagrass. Primary producers are the autotroph organisms that make their own food instead of eating other organisms.
This means primary producers become the starting point in the food chain for heterotroph organisms that do eat other organisms. Some marine primary producers are specialised bacteria and archaea which are chemotrophs , making their own food by gathering around hydrothermal vents and cold seeps and using chemosynthesis.
However most marine primary production comes from organisms which use photosynthesis on the carbon dioxide dissolved in the water. This process uses energy from sunlight to convert water and carbon dioxide  : — into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells.
Reefing the benefits
The principal marine primary producers are cyanobacteria , algae and marine plants. The oxygen released as a by-product of photosynthesis is needed by nearly all living things to carry out cellular respiration. In addition, primary producers are influential in the global carbon and water cycles. They stabilize coastal areas and can provide habitats for marine animals.
List of Important Coastal and Marine Biodiversity Areas (ICMBAs) in India
The term division has been traditionally used instead of phylum when discussing primary producers, but the International Code of Nomenclature for algae, fungi, and plants now accepts both terms as equivalents. Cyanobacteria are a phylum division of bacteria which range from unicellular to filamentous and include colonial species. They are found almost everywhere on earth: in damp soil, in both freshwater and marine environments, and even on Antarctic rocks. The first primary producers that used photosynthesis were oceanic cyanobacteria about 2.
Because oxygen was toxic to most life on Earth at the time, this led to the near-extinction of oxygen-intolerant organisms , a dramatic change which redirected the evolution of the major animal and plant species. Originally, biologists thought cyanobacteria was algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria is a bacteria, and hence is not even in the same Kingdom as algae.
Most authorities exclude all prokaryotes , and hence cyanobacteria from the definition of algae. Algae is an informal term for a widespread and diverse group of photosynthetic protists which are not necessarily closely related and are thus polyphyletic. Marine algae can be divided into six groups:. Unlike higher plants, algae lack roots, stems, or leaves. They can be classified by size as microalgae or macroalgae. Microalgae are the microscopic types of algae, not visible to the naked eye. They are mostly unicellular species which exist as individuals or in chains or groups, though some are multicellular.
Microalgae are important components of the marine protists discussed above , as well as the phytoplankton discussed below. They are very diverse. It has been estimated there are ,, species of which about 50, species have been described. They are specially adapted to an environment dominated by viscous forces. Chlamydomonas globosa , a unicellular green alga with two flagella just visible at bottom left. Chlorella vulgaris , a common green microalgae , in endosymbiosis with a ciliate . Macroalgae are the larger, multicellular and more visible types of algae, commonly called seaweeds.
Seaweeds usually grow in shallow coastal waters where they are anchored to the seafloor by a holdfast. Seaweed that becomes adrift can wash up on beaches. Like microalgae, macroalgae seaweeds are technically marine protists since they are not true plants. A seaweed is a macroscopic form of red or brown or green algae.
Sargassum seaweed is a planktonic brown alga with air bladders that help it float. Sargassum fish are camouflaged to live among drifting Sargassum seaweed. The unicellular bubble algae lives in tidal zones. The unicellular mermaid's wineglass are mushroom-shaped algae that grow up to 10 cm high. Killer algae are single-celled organisms, but look like ferns and grow stalks up to 80 cm long.
Unicellular organisms are usually microscopic, less than one tenth of a millimeter long. There are exceptions. Mermaid's wineglass , a genus of subtropical green algae , is single-celled but remarkably large and complex in form with a single large nucleus, making it a model organism for studying cell biology. Selective breeding in aquariums to produce hardier strains resulted in an accidental release into the Mediterranean where it has become an invasive species known colloquially as killer algae.
Back in the Silurian , some phytoplankton evolved into red , brown and green algae. These algae then invaded the land and started evolving into the land plants we know today. Later, in the Cretaceous , some of these land plants returned to the sea as mangroves and seagrasses. Marine plants can be found in intertidal zones and shallow waters, such as seagrasses like eelgrass and turtle grass , Thalassia. These plants have adapted to the high salinity of the ocean environment. Plant life can also flourish in the brackish waters of estuaries , where mangroves or cordgrass or beach grass beach grass might grow.
Sea dragons camouflaged to look like floating seaweed live in kelp forests and seagrass meadows . Mangroves and seagrasses provide important nursery habitats for marine life, acting as hiding and foraging places for larval and juvenile forms of larger fish and invertebrates. Plankton from Greek for wanderers are a diverse group of organisms that live in the water column of large bodies of water but cannot swim against a current.
As a result, they wander or drift with the currents. They are a crucial source of food for many marine animals, from forage fish to whales. Plankton can be divided into a plant-like component and an animal component. Phytoplankton are the plant-like components of the plankton community "phyto" comes from the Greek for plant. They are autotrophic self-feeding , meaning they generate their own food and do not need to consume other organisms.
Phytoplankton consist mainly of microscopic photosynthetic eukaryotes which inhabit the upper sunlit layer in all oceans. They need sunlight so they can photosynthesize. Most phytoplankton are single-celled algae, but other phytoplankton are bacteria and some are protists. They form the base of the primary production that drives the ocean food web , and account for half of the current global primary production, more than the terrestrial forests.
Diatoms are one of the most common types of phytoplankton. The cyanobacterium Prochlorococcus accounts for much of the ocean's primary production. Green cyanobacteria scum washed up on a rock in California. Gyrodinium , one of the few naked dinoflagellates which lack armour. Zoochlorellae green living inside the ciliate Stichotricha secunda. The coccolithophore Emiliania huxleyi. Algae bloom of Emiliania huxleyi off the southern coast of England.
Guinardia delicatula , a diatom responsible for algal blooms in the North Sea and the English Channel .
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Zooplankton are the animal component of the planktonic community "zoo" comes from the Greek for animal. They are heterotrophic other-feeding , meaning they cannot produce their own own food and must consume instead other plants or animals as food. In particular, this means they eat phytoplankton. Zooplankton are generally larger than phytoplankton, mostly still microscopic but some can be seen with the naked eye.
Many protozoans single-celled protists that prey on other microscopic life are zooplankton, including zooflagellates , foraminiferans , radiolarians and some dinoflagellates. Other dinoflagellates are mixotrophic and could also be classified as phytoplankton; the distinction between plants and animals often breaks down in very small organisms. Other zooplankton include pelagic cnidarians , ctenophores , molluscs , arthropods and tunicates , as well as planktonic arrow worms and bristle worms.
Nassellarian radiolarian. Group of planktic foraminiferans. Copepods eat phytoplankton.
This one is carrying eggs. Venus girdle , a ctenophore. Tomopteris , a planktonic segmented worm with unusual yellow bioluminescence . Many marine animals begin life as zooplankton in the form of eggs or larvae, before they develop into adults. These are meroplanktic , that is, they are planktonic for only part of their life. Dinoflagellates are often mixotrophic or live in symbiosis with other organisms.
Euglena mutabilis , a photosynthetic flagellate. Noctiluca scintillans , a bioluminescence dinoflagellate. Some dinoflagellates are bioluminescent. At night, ocean water can light up internally and sparkle with blue light because of these dinoflagellates. The luminescence, sometimes called the phosphorescence of the sea , occurs as brief 0. Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base.
In particular, the biomass of consumers copepods, krill, shrimp, forage fish is larger than the biomass of primary producers. This happens because the ocean's primary producers are tiny phytoplankton which are r-strategists that grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, terrestrial primary producers, such as forests, are K-strategists that grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production.
Because of this inversion, it is the zooplankton that make up most of the marine animal biomass. As primary consumers , they are the crucial link between the primary producers mainly phytoplankton and the rest of the marine food web secondary consumers. If phytoplankton dies before it is eaten, it descends through the euphotic zone as part of the marine snow and settles into the depths of sea. In researchers found whales carry nutrients from the depths of the ocean back to the surface using a process they called the whale pump.
There whales defecate a liquid rich in nitrogen and iron. Instead of sinking, the liquid stays at the surface where phytoplankton consume it. In the Gulf of Maine the whale pump provides more nitrogen than the rivers. Sediments at the bottom of the ocean have two main origins, terrigenous and biogenous. Much smaller amounts of precipitated minerals and meteoric dust can also be present. Ooze , in the context of a marine sediment, does not refer to the consistency of the sediment but to its biological origin.
The term ooze was originally used by John Murray , the "father of modern oceanography", who proposed the term radiolarian ooze for the silica deposits of radiolarian shells brought to the surface during the Challenger Expedition. Diatoms, major components of marine plankton, also have silica skeletons called frustules. Coccolithophores have plates or scales made with calcium carbonate called coccoliths. A diatom microfossil from 40 million years ago. Diatomaceous earth is a soft, siliceous , sedimentary rock made up of microfossils in the form of the frustules shells of single cell diatoms click to magnify.
Shells tests , usually made of calcium carbonate, from a foraminiferal ooze on the deep ocean floor. Marine carbon cycle . Marine silicon cycle. In a team of microbiologists led by Edward DeLong made a crucial discovery in the understanding of the marine carbon and energy cycles. They discovered a gene in several species of bacteria   responsible for production of the protein rhodopsin , previously unheard of in the domain Bacteria.
These proteins found in the cell membranes are capable of converting light energy to biochemical energy due to a change in configuration of the rhodopsin molecule as sunlight strikes it, causing the pumping of a proton from inside out and a subsequent inflow that generates the energy. Overfishing is occurring in one third of world fish stocks, according to a report by the Food and Agriculture Organization of the United Nations. Ocean acidification is the increasing acidification of the oceans, caused by the uptake of carbon dioxide from the atmosphere.
When carbon dioxide dissolves in water it forms hydrogen and carbonate ions. This in turn increases the acidity of the ocean and makes survival increasingly harder for shellfish and other marine organisms that depend on calcium carbonate to form their shells. Marine pollution results from the entry into the ocean of industrial , agricultural, and residential wastes. Nutrient pollution is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrates or phosphates , stimulate algae growth.
Toxic chemicals can adhere to tiny particles which are then taken up by plankton and benthic animals , most of which are either deposit feeders or filter feeders. In this way, toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner which depletes oxygen, causing estuaries to become anoxic. Pesticides and toxic metals are similarly incorporated into marine food webs, harming the biological health of marine life.
Many animal feeds have a high fish meal or fish hydrolysate content.