Plantae, Animalia And Viruses: Overview, Genetic Material, Concepts

In biological classification, there are three fundamental groups that are key to understanding the diversity and function of life on earth: The first three domains are Plantae, Animalia and Viruses. Plantae is a higher plant kingdom containing chlorophyll cells that are responsible for oxygen and gross equilibrium. Animalia contains those heterotrophic organisms that have many organ systems necessary for interdependence within the environment and those significant in human life.

This Story also Contains

1. Kingdom Plantae
2. Characteristics of Plantae
3. Classification Of Plantae
4. Kingdom Animalia
5. Characteristics of Animalia
6. Classification Of Animalia
7. Viruses
8. Characteristics Of Viruses
9. Classification Of Viruses
10. Virus Life Cycle

Viruses can neither be classified under the definition of an organism, but are heavily implicated in disease mechanisms, genetics, and evolution. A review of the previous classifications will be useful to comprehend the laws of biology, the interaction of living organisms with their environment, and its influence on human health. A general overview of these classifications, their implication in scientific study and the organisation to disclose their characteristics, changes, and processes in later sections of this article is given.

Kingdom Plantae

Kingdom Plantae comprises all multicellular, photosynthetic, eukaryotic organisms, also known as plants. These organisms are characterised by having chlorophyll in chloroplasts and cellulose cell walls through which photosynthesis can be utilised as a source of energy using sunlight. These organisms in this kingdom keep the environment in balance by the excretion of oxygen and serve as the source of most food chains. Kingdom Plantae encompasses a diverse range of forms from the unicellular algae to the higher flowering plants and is commonly grouped into divisions like algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

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Characteristics of Plantae

Members of the Kingdom Plantae are living things that are present on both land and produce their food with sunlight, water, and carbon dioxide by the process of photosynthesis. They have fixed positions and grow all their life. They possess various parts, such as roots, stems, and leaves, that aid them in surviving in their environment. The basic characteristics are discussed below:

• They have a green pigment known as chlorophyll that is utilised for food production.
• They have cells that contain a hard substance for their cell wall called cellulose.
• They have tissues to transport water and food in the body.
• They grow from seeds or spores and keep on growing even after reaching maturity.
• They never move from location to location as they are non-motile.

Classification Of Plantae

Plants in the Kingdom Plantae are classified into several major groups based on their evolutionary relationships and distinguishing characteristics. All of them are discussed below in the table:

Kingdom Animalia

Kingdom Animalia includes all multicelled, eukaryotic heterotrophic organisms, thus relying on other organisms for nutrition. Animals lack cell walls, thus are not rigid and have the capacity to develop special tissues and organs. Animals are capable of movement at some stage in their life and have complex digestion, reproduction, and nervous control systems. Animals are sexually reproductive and have an enormous variety of body structures from simple sponges to complex mammals. Animals consist of millions of species and are crucial in ecosystems as consumers, pollinators, decomposers, etc.

Characteristics of Animalia

The basic characteristics of the Kingdom Animalia are discussed below:

Heterotrophic nutrition: Organisms in the Kingdom Animalia are heterotrophic. This means that they get their food from other organic materials. They depend on the absorption of food rather than manufacturing food from inorganic compounds through the process of photosynthesis.

Cell structure: Animal cells do not possess cell walls, which makes them versatile in their shape and size of the shape. It has highly developed cells grouped into tissues, organs and organ systems performing given activities like digestion, circulation, etc or coordinating nervous systems.

Reproduction: Most animals are known to reproduce both sexually and asexually. Sexual reproduction entails the formation of new organisms by the combination of gametes. These are sperm and egg cells, and the practice occurs due to specially adapted reproductive organs. Some species exhibit the process of asexual reproduction through budding, fragmentation or asexual reproduction as in the case of parthenogenesis.

Development stages: Animal embryos go through embryonic development, and they go through a series of developmental stages, including fertilisation, cleavage, gastrulation and organogenesis. This occurrence results in the creation of specialised tissues, organs, and body structures in the developing organism.

Classification Of Animalia

Animalia is divided into two categories based on their structure. These are :

• Invertebrates: These animals do not possess a vertebral column or backbone. These are the largest group of the animal family, and their members include Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, and Echinodermata.
• Vertebrates: These animals have well-developed skeletons provided by the vertebral column, which includes the vertebrae. Those belong to the phylum Chordata. It has a dorsal nerve cord, notochord (or spine in vertebrates), and pharyngeal slits. Classification of vertebrates is as follows: fish, amphibians, reptiles, birds and mammals. The further classification is discussed below:

Viruses

Viruses are a micro infectious agent that fall somewhere between living and nonliving objects. It is unable to grow, reproduce, or perform metabolic processes by itself and needs to find a living host cell to replicate itself. Viruses consist of genetic material, either DNA or RNA with in a protein coating, and occasionally an outer lipid coat. They infect a variety of organisms, ranging from animals, plants, fungi, to even bacteria (bacteriophages). Although best known to cause sicknesses such as flu, COVID-19, and HIV, viruses are also employed in scientific research, vaccines, and gene therapy.

Characteristics Of Viruses

Viruses are small infectious particles that are not cell-borne and cannot grow or replicate on their own. They must infect the body of a living host, i.e., a human, animal, plant, or even a bacterium, to replicate. Viruses do not survive outside a host. Viruses consist of genetic material, either DNA or RNA, covered by a protein coat. Viruses are responsible for causing numerous diseases, but are also employed in genetic studies and vaccine production. Some of the common characteristics are discussed in detail below:

• Viruses have no cell structure like that of living things.
• They can reproduce only inside host organism cells.
• A virus consists of a core of RNA or DNA and a protein shell called a capsid.
• Some viruses have a second outer layer known as an envelope. They do not perform functions such as respiration, digestion, or excretion

Classification Of Viruses

The classification of viruses is done based on the genetic material they carry. These are:

DNA Viruses: These viruses have their genetic material in the form of deoxyribonucleic acid, or DNA for short. Some of the examples of DNA viruses are herpesviruses, adenoviruses and poxviruses. DNA viruses replicate their genomes with the help of enzymes of the host cell and can become integrated with the host genome (e.g., retroviruses).

RNA Viruses: Some viruses contain RNA as their genetic material. These types of viruses are called RNA viruses. They are also subdivided into positive-sense RNA viruses-which are easily translated into proteins, negative-sense RNA viruses-require RNA polymerase to synthesise mRNA and retroviruses-which use reverse transcriptase to synthesise DNA. Examples include Influenza viruses such as A and B, Hepatitis C viruses, and HIV.

Types of hosts

There are basically three types of hosts. All of them are discussed below:

Virus Life Cycle

Viruses have a life cycle which outlines how they replicate and move within the host cells. These are discussed below in the table:

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