Tag: #Animal Kingdom

Introduction

Mammals, fish, amphibians, birds, and reptiles are among the five classes into which animals are divided. Each one of them needs the environment to survive, including air, food, water, and shelter. The only vertebrates that live part of their lives in water and part on land are amphibians. As a result, they differ from other animal species. An amphibian is a tiny vertebrate organism that requires water or a moist environment to exist. As amphibian’s body temperatures are influenced by their surroundings and they can thrive in both terrestrial and aquatic habitats, they are also referred to as cold-blooded vertebrates. Frogs, toads, newts, caecilians, and salamanders are amphibians.

Characteristics of Class Amphibia

Body 

• Amphibian bodies are separated into the head, trunk, and tail. Few amphibians just have a head and a tail (frogs). The neck can be absent or present.
• Some amphibians are limbless, while others have two sets of pentadactyl limbs.
• The skin is smooth, moist, scale-free, and abundant with mucous glands.

Sense organs

• Amphibians have two olfactory lobes that are responsible for their ability to smell.
• Eyes are well developed.
• Although they lack an external ear, the tympanum shields their middle ear.

Digestive system

• Amphibians have digestive systems that include the mouth, oesophagus, stomach, and intestine closing in a division called the cloaca.
• Cloaca participates in the digestive, excretory, and reproductive systems.

Circulatory system

• Amphibians have a closed circulatory system.
• They have three-chambered hearts, that are made up of two auricles and one ventricle.
• There are two circulatory paths; one is for the oxygenation of the blood through the lungs and skin and another route is to carry oxygen to the remaining parts of the body.
• However, there is incomplete double circulation because the oxygenated blood obtained in the left atrium and the deoxygenated blood received in the right atrium mix very slightly.

Diet

• Invertebrates like bloodworms, mealworms, earthworms, snails, slugs, locusts, and other creatures are eaten by amphibians. Larger amphibians can also consume small mammals.
• Young frogs require food most days of the week, whereas adult frogs only require it every two to three days.

Excretory system

• Amphibians have mesonephric kidneys during the adult stage and have pronephric kidneys at the larval stage.
• When on land, they expel the majority of their metabolic waste as ammonia (in tail form) and urea (in tailless forms).
• Kidneys are the primary excretory organ of amphibians.

Reproduction

• Amphibians can be fertilized internally (by a salamander) or externally (by most amphibians).
• They attract their mates by making various sounds; for instance, the loud croaking of frogs may be a signal for mates.
• Since the eggs don’t have shells and get dry when kept on land, the eggs must be laid in freshwater.

Classification of Amphibia

Based on their order, amphibians can be divided into three groups they are-

Apoda (Gymnophiona or Caecilia)

• The body is elongated and can be differentiated into the head and trunk. 
• They do not have limbs and hence resemble earthworms.
• They have small dermal scales
• As their eyes are covered by bone or skin, they are known as blind worms.
• They lack tails or may have short tails.
• Internal fertilization takes place.
• Eg-Caecilians

Urodela (Caudata)

• The body is long and differentiated into a head, neck, tail, and four limbs which are of similar length.
• Their skin is smooth and moist.
• Through their skin, they breathe.
• At both the larval and adult stages, they have teeth in their jaws.
• They are incapable of making sounds.
• They undergo fertilization either internally or externally.
• Examples-Newts and Salamanders

Anura (Salientia)

• The body is differentiated into the head and trunk. But both of them are fused.
• They have four limbs that are designed specifically for jumping.
• Their mouth is large.
• At the larval stage, the tail is present and the adult tail is absent.
• Due to the presence of a chemical called magainin, the skin secretions of anurans have a naturally occurring antibiotic effect.
• In anurans, external fertilization takes place.
• Examples: Toads and frogs

Scientific Classification of Amphibia

The scientific classification of amphibians is as follows-

Domain	Eukaryote
Kingdom	Animalia
Phylum	Chordata
Subphylum	Vertebrata
Class	Amphibia
Order	Urodela  Apoda Anura

Summary 

Cold-blooded creatures called amphibians descended from lobe-finned fish. When they are larvae, they can survive in water, but as adults, they must live on land. Frogs, toads, salamanders, newts, and caecilians are some examples of amphibians that are grouped into orders such as  Apoda, Urodela, and Anura. They have different body types. During the younger stage they breathe through the skin(gills) and as they reach adulthood, their lungs develop and they now breathe through both skin and lungs.

Frequently Asked Questions

1. Explain metamorphosis.
Ans: Metamorphosis is the term used to describe the changes an animal undergoes during its life cycle. When a frog egg hatches, a tadpole is released, which first grows rear legs then develops the front legs, and then finally becomes an adult frog.

2. Give the 5 kingdom classification with examples.
Ans: The 5 kingdom of classification was proposed by RH Whittaker in 1969. 

The 5 kingdom classification is-

• Kingdom Monera- it includes the prokaryotes.
• Kingdom Protista- it includes single-celled eukaryotes.
• Kingdom Fungi- it includes various fungi.
• Kingdom Plantae- it includes all types of plants
• Kingdom Animalia- it includes all types of animals.

3. How do amphibians breathe?
Ans: The majority of amphibians can breathe through their skin, which is a thin, permeable organ that is dense with blood vessels. In their larval stage, some aquatic animals, like frogs, have gills that absorb oxygen from the water and expel carbon dioxide as waste.

Introduction

Animals come in a variety of shapes and sizes. Members of this kingdom are Multicellular, eukaryotic animals that have a heterotrophic mode of nutrition and their cells are devoid of cell walls. They are typically motile that move from one place to another. Animals come in a variety of shapes and sizes. 

Classification of Animal kingdoms based on their characteristics

Animal classification is based on various characteristics such as

• Arrangement of cells
• Symmetry
• Coelom or body cavity

Arrangement of cells

All animals are multicellular but the arrangement of cells within them is different. This arrangement of cells is known as the levels of the organization. Based on this animals are classified under

• The cellular level of organization- Animals at this level of organization generate loose clusters of cells. Eg. Sponges.
• Tissue level of organization-Animals under this level has cells that combine to form tissues and all tissues perform various bodily activities.
• Organ level of organization-  Animals with an organ-level organization are those in which tissues with the same functions group together to form an organ.
• Organ system level of organization-Organ system degree of organization is displayed when organs work together to produce an organ system that performs many physiological functions.

Symmetry

• The symmetry of an animal’s body can be used to classify it.
• The body exhibits three different types of symmetry.
• Asymmetry is symmetry where the plane is not divided into two equal halves. It was observed in the phylum Porifera (sponges).
• Radial symmetry is a symmetry that divides a plane passing through the central axis into two halves. This is seen in phylum Coelenterates, Ctenophores, and Echinoderms.
• When a  plane separates the body into two identical left and right halves then such symmetry is known as bilateral symmetry.
• Arthropods and annelids are two examples of animals with bilateral symmetry.

Coelom or body cavity

• The coelom is the space that is found between the body wall and the alimentary canal. Based on body activity organisms are classified as-
• Acoelomates- They do not have a body cavity. Eg- members of Phylum Platyhelminthes.
• Pseudocoelomates–They have a false body cavity. Eg. members of Phylum Aschelminthes.
• Coelomate- They have a true body cavity that is filled with coelomic fluid. This is seen in members from Phylum Annelida to Phylum Chordata.

Phylum belonging to Kingdom Animalia

Phylum Porifera

• They are also known as sponges.
• They are multicellular organisms that are organized at the cellular level.
• They have asymmetrical body shapes and are typically found in marine environments.
• They have a water canal system. Water enters the body through the Ostia (pores) that are lined up on the surface of the body. From here it is conveyed into the spongocoel. Water exists in the body through the osculum.
• The movement of water facilitates gas exchange, food capture, and water excretion.
• Porifera members are Hermaphrodites.
• Common examples are Spongilla and Sycon.

Phylum Cnidaria

• They are aquatic, sessile, free-living, and radially symmetric creatures.
• On their body, tentacles, have stinging capsules called cnidoblast. These cnidoblasts
• are defense mechanisms of the organism and it also helps in anchorage.
• They display tissue-level organization and diploblastic structure.
• They have a single opening mouth on the hypostome and both internal and external digesting systems.
• The basic body forms that Cnidarians displays are the polyp and the Medusa.
• Physalia and Adamsia are two examples.

Phylum Platyhelminthes

• They are called flatworms because of their dorsally flattened bodies.
• They live inside animals, including humans, and are endoparasitic.
• Some of them take nourishment straight from their host.
• They are triploblastic, bilaterally symmetric animals that are organized at the organ level.
• They have no true internal body to accommodate well-developed organs for proper functioning. 
• The development happens throughout several larval stages. Fertilization is internal.
• Taenia and Fasciola are two examples.

Phylum Annelida

• They can have a closed circulatory system and can either be terrestrial or aquatic, parasitic or free-living.
• They exhibit bilateral symmetry and organ-level organization.
• Segments and metameres are found on the body surfaces.
• Circular muscles in their bodies aid in mobility.
• The Annelida species perform sexual reproduction.
• Examples-Nereis and Hirudinaria.

Phylum Arthropoda

• In the Kingdom Animalia, it is the largest phylum that includes insects.
• They show bilateral symmetry and organ-level structure.
• They have joint legs and a tough exoskeleton
• Arthropods have a chitinous layer covering their belly, thorax, and other body parts.
• Through Malpighian tubules, they excrete.
• The development may be direct or indirect, and fertilization is typically internal.
• Eg- Cockroaches, Flies, Bees, etc.

Phylum Mollusca

• They are the second-largest phylum of the kingdom Animalia.
• They have an organ level of organization and may be terrestrial or aquatic.
• They have true bodies, triploblastic organization, and show bilateral symmetry.
• Most molluscs have calcareous shells covering their bodies.
• The head, visceral hump, and muscular foot make up the body.
• Internal fertilization occurs and they show indirect development.
• Examples include Pila and Chaetopleura.

Phylum Echinodermata

• Animals have calcareous skin coverings.
• They exist in aquatic settings that are organized at the organ level.
• While adults have radial symmetry, larval-stage animals have bilateral symmetry.
• They have a water vascular system that aids in breathing, locomotion, and food collection.
• There is no excretory system in them.
• Echinoderms show external fertilization and reproduce through sexual reproduction.
• Asteria and Echinus are examples.

Phylum Protochordata

• These creatures are triploblastic and bilaterally symmetric.
• They have a true body and, at some point in their life cycle, a notochord is present.
• They typically inhabit marine areas.
• Examples are Herdmania and Amphioxus.

Phylum Chordata

• This phylum includes creatures like birds and humans.
• The presence of a notochord is a trait shared by all species in this phylum.
• They have a single, hollow central nervous system that is located dorsally.
• A post-anal tail is present, which aids with movement.
• A pharynx is penetrated by gill slits.
• The phylum is further divided into subphyla Urochordata, Cephalaochordata, and Vertebrata.

Summary 

The largest kingdom that includes all animals is called Kingdom Animalia. Several criteria, including the level of organization, symmetry, coelom, segmentation, and notochords, are used to classify these species. Various phyla such as  Porifera, Cnidaria, Ctenophora, Platyhelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata, and Chordata make up this Kingdom.

Frequently asked question

1. Describe protozoans.
Ans: Protozoans are-

• Microscopic, unicellular, free-living protozoa are present in practically all ecosystems.
• They are typically parasitic and mobile. 
• Digestion of food by these organisms takes place through the process of Osmotrophy, which is the engulfment of food through cell membranes.

2. How are animals classified based on the circulatory system?
Ans: A network of arteries, veins, capillaries, and the Heart together is known as the circulatory system. There are two types of circulatory systems: open and closed systems.

• In an open system, the blood is pumped into a chamber outside the heart known as the hemocoel rather than being constrained to the blood vessels.
• In a closed system, the blood circulates in one direction from the heart to the surrounding vessels and then returns to the heart. In this system, the blood is contained within the blood capillaries.

3. What do diploblastic organization and triploblastic organization mean?
Ans:

• Diploblastic organization – It is the arrangement of cells in two layers, i.e outer ectoderm and inner endoderm. It is seen in Coelenterates 
• Triploblastic organization -It is a  three-layered arrangement of cells, i.e ectoderm, mesoderm, and endoderm. Common examples are Platyhelminthes, chordates, etc.