Survival of animals in nature

Introduction: It is very necessary and interesting to know that each and every living organism in the world are trying to survive or in the process of survival from the very beginning. Those animals which can survive best in the different types of changed environmental conditions can survive and adapt in nature. Such animals are considered to be successful animals of nature. On the other hand there are some animals which can not survive or adapt in the different types of the changed environmental conditions can no more survive in nature. For example Dinosaurs of the mesozoic era.
Why were dinosaurs wiped out in nature? Dinosaurs were the animals of mesozoic era in the history of earth. Formerly, they were dominating all the other animals of nature by their huge body which was more than a ton of body weight. But they had the less developed brain than the mammals. Suddenly the environment was changed in nature and all the herbivorous food source was destroyed.Dinosaurs which were dependent in the herbivorous food could not change the food habit from the herbivorous to the carnivorous type. Only those animals who could change their food habit survived in nature and the others which could not adjust their food habit from the herbivorous to carnivorous were destroyed in nature. This phenomena is known as the "survival of fittest."
What is natural selection? Natural selection is also one of the important phenomena in nature. It is one of the point of the theory of evolution of Charles Darwin which is popularly known as "Darwinism". According to the point "the natural selection", Nature helps those animals which help themselves. In other words, nature selects only those animals which are fittest in the survival process of nature. But those animals who could not change to adapt and survive in the different types of the changed environmental conditions are no more selected by natural in the list of new species.
Advantage of natural selection. the phenomena of natural selection is the important element of Darwin's theory which acts positively in the process of organic evolution or the gradual development of living organisms in nature.It gives strong evidence in favour of the fact that organic evolution has taken place in the earth and it is still an ongoing process.

Adaptation in aquatic vertebrate animals

Introduction: Adaptation is defined as the structural and physiological modification in the body of the living organisms in order to adjust themselves in the particular environment. Aquatic environment is the habitat which consists the large or smaller water bodies like sea,lakes, ponds, rivers ponds,streams and even the ditches and the pools.
Which animals are the aquatic vertebrates? Aquatic vertebrate animals are the vertebrate animals with back bone in their body and aquatic means living in any type of water body.Fishes, amphibians, reptiles, and mammals are the classes of which some of the animals of each group are adapted or adjusted to live in the aquatic habitat. Not all the animals of each group are adapted in water but only few of them are adapted to live in water bodies. For example, Fishes, amphibians, some reptiles, some birds and some mammals are adapted to live in water.
Adaptational features of the aquatic adapted animals : Animals which are adapted in aquatic habitat usually show the following  adaptational features:
- They have streamlined body shape which helps them to minimise water resistance which makes them to live easily in in water.
- Respiratory organs are gills or nostrils . But in perfectly adapted forms gills are the respiratory organs which help to take in dissolved oxygen from water and give out carbondioxide. Nostrils or the nose openings in the aquatic adapted vertebrates other than the fishes in which the position of nostrils is jfound at the or near the top of the head which makes them to take in oxygen from the air by frequently coming up to the surface of water.

- Locomotory organs are fins in the perfectly adapted forms like fishes but in other aquatic forms fins are not found but fin-like structures called flippers and paddle are found which help them to move easily in aquatic habitat.
- Modification  is also found in the toes in some aqsuatic animals. A thin fold of skin called web is developed between the toes for e.g. in ducks and frogs. Presence of helps them a lot to increase the surface area for swimming.
- Modification in the skin or under the skin is also found. For example, whales have the thick layer of fat under the surface of their skin which helps them in temperature regulation so that they can survive easily even in the extreme cold temperature of the winter season.

Some particulars about dogs, cats and pigs

Dogs are men's best friends: Dogs are the animals which are intelligent, good and use to show the basic obdience. They can learn to sit, lie down and fetch. They can even read their owner's intentions. They can at least find food in response to non-verbal cues,which is a type of understanding that scientists think may be akin to the human ability to understand some one else's point of view.
Cat's are adaptable: Cats are the carnivorous animals of phylum chordata of class mammalia. According to the report given by the cat owners ,they have trained their pet cats to sit down, roll over and jump through hoops. Cats learn the tricks by observation and imitation. But training cats is harder than dogs. But does that mean that they are less intelligent? Not necessarily. Cat experts say they are solitary animals which are motivated by the need to survive. This has allowed them to adapt a variety of domestic environment for at least 9,500 years.
Pigs: Pigs are also the chordates which belong to the class mammalia and the order primate. They are the smartest , cleanest domestic animals known more so than cats and dogs according to some experts..But pigs don't have sweat glands. So they roll around in the mud to stay cool.A sign of their cleverness came from  experiments. Pigs were trained  to move a curser on a video  screen with their snouts and used the curser to distinguish between scribbles they knew and those they were seeing for the first time. They learned the task as quickly as chimpanzees.

Lizards in the animal world

Introduction:Lizards are the vertebrate animals which have got a welll - developed vertebral column in their dorsal side of the body. They are more developed than fishes and amphibians but less developed then the aves and mammals.
Systematic position: Lizards are included under phylum chordata and class reptilia. Their order is lacertilia. There are two different orders in reptilia, one is lacertilia and another is ophidia. Lacertilia order includes lizards which are with two pairs of limbs. Order ophidia includes the snakes which are limbless lizard
Where do they live? They are terrestrial in habitat i.e. they live on dry terrestrial land. They are completely adapted to live  in dry terrestrial habitat. They have the stream - lined body with horney and dry skin. They have well-developed claws. They are also known as the first amniotic animals because of the presence of the amniotic cavity inside their body. Amniotic fluid present inside the amniotic cavity  helps them to float in the embryonic stage so  that they are not affected by dessication and drying and any dry condition of the environment.
How are lizards different from the snakes? Lizards are different from the snakes in habing two pairs of limbs, and hering capacity where as snakes are limbless and totally deaf reptiles without any ear.

STAR FISH, THE MACROINVERTEBRATE OF SEA

Introduction: Echinoderms are the latest group of macroinvertebrate animals which live exclusively in marine habitat. They are not found in any type of inland water. They have the spiny structures in the outer surface of their body or skin. So they are known as "echinoddermata". Several animals are included under this group like starfish, seacucumber, holothuria etc Among them starfish is very familiar to us. Actually starfish is not the fish. To be a fish the animal must be included under the phylum chordata in which all the animals having the vertebral column are included. But its very funny that starfish sontains neither the vertebral column nor it is a true fish. But still it is popularly known as "starfih." Zoology is a very funny subject although it is a biological study of animals. for example, naming of starfish is not based on any reasonable facts.
Why it is named starfish although its not actually a true fish? It is very interesting question to ask why starfish is named as is. Of course , all the fishes use to live in water. Starfish also lives in water like a fish. Its body is shaped like a star in the sky. So, there are two reasons behind the naming
of starfish. One is it lives in water all the time. And the another reason is that it has the shape like that of the star of sky. So, it is known as starfish.
What is  particular about starfish?  Starfish consists of certain characters which makes it special in the animal world. It consists of a unique system in its body which is not seen in any other groups of animals in the animal world. This is the special type of vascular system in which water circulates in its body. This system is known as "water vascular system". This system is scientifically known as ambulacral system. Another unique structure of its body is the presence of tub e like feet in the body which are called tube feet. They are the legs or locomotary organs of starfish which help in the movement.

MOLLUSCA, THE SHELLED INVERTEBRATES OF ANIMAL WORLD

 Introduction :Animal world consist of a particular group of animals which have their body covering made of of shell which is made up of calcium carbonate. Having been composed of calcium carbonate the shell is very hard in texture and give protection to the whole internal vital organs of the body.Inside the shell the various organs of the body are found in compact form concentrated in a mass  and this mass of all the internal visceral organs is known as "visceral mass". The body of these animals consists of the following parts which are anterior head, ventral muscular foot and visceral mass.

Why are they called the macroinvertebrates?: As the molloscs are the invertebrates with comparatively large sized body in comparison to all the other invertevrates from protozoa to arthropoda, they are called macro - invertebrates. Invertebrate animals with large sized body are a little bit different from micro invertebrates in the sense that they have more devveloped systems and structures in the body. Their digestive system, respiratory system,circulatory system,excretory system an reproductive systems  and  nervous systems are all well-developed  than the microinvertebrates.So they are considered to be one step forward in the developmental step according to the Naturalists.

Economic importance of macroinvertebrates including the animals of phylum mollusca: Molluscs and the other macro invertebrates are economically very important animals of nature. They use to live in aquatic and semiaquatic habitat. They always live in association with other animals and plants of nature along with the nonliving components like water, soil temperature, light and dissolved nutrients.
Molluscs help to filter the impure water and purify it. Molluscs use to eat the various dissolved and decayed vegetable materials of the inhabiting water turning the water clear and transparent. So, they are said to be helpful in water purification in the various types of inland waters like rivers, lakes, ponds, streams and pools.

Earth worms in the animal world

       Earthworms   Earthworms are the animals in the animal world which have the elongated cylindrical body with pointed anterior ends but blunt posterior ends. They have metamerically segmented body i.e. whole the body is segmented in such a way that external segmentation is continuous with the internal segmentation and each segment is true and complete. Such segments are annules or rings. Earthworms are also the invertebrate animals without any back bone i.e. vertebral column. These animals use to live in the moist places of the earth and have elongated worm like body, so they are known as earthrorms.
Earthworms as the friends of farmers: Earthworms are the animals which contribute a lot to the farmers in being the animals which help them to make the soil loose and perforated. They also discharge their wastes inside the soil. wastes discharged by earthworms is very rich in organic substances and large amount of humus i.e. the very fertile part of soil enriched with decayed vegetable materials. Moreover , such soil is also very rich in oxygen content. Nitrogen fixing bacteria prefer to live in such type of soil which help to increase the fertility of soil a lot by fixing nitrogen in the soil.
Earthworms as the laboratory animals: Earthworms are very popular as the laboratory animals. They are among the cheap animals and easy to collect from the land. They are supplied in the laboratory to be used for scientific experiments. They are very helpful to be used for experiments in scientific research.
Use of earthworms in medical treatment:  Earthworms are used as the animals whcih are use din the medical treatment of several types of diseases. For example, they are used in the treatment of jaundice, bladder disease, plague etc. Poder prepared by dried earthworms is very useful in the treatment of malnutrition.