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

Definition

In biological classification, three fundamental categories are pivotal in understanding the diversity and functioning of life on Earth: The three domains include Plantae, Animalia and Viruses. Plantae is a kingdom that consists of complex plant-like organisms with chlorophyll-containing cells involved in oxygen manufacture and maintenance of gross equilibrium. Animalia is composed of heterotrophic organisms, those with many organ systems necessary for interdependence with the environment and those significant in human lives. Viruses do not fit into the definition of an organism; however, they are important in disease processes, genetics, and evolution. It is significant to study the previous categories to understand the principles of biology, relations between living organisms and the environment, as well as the effects on human well-being. An introduction to these classifications, their roles in scientific studies and the structure to unveil their attributes, modifications, and functions in succeeding sections of this article is offered.

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Kingdom Plantae

The characteristics of the kingdom Plantae are listed below-

Characteristics of Plantae

Autotrophic nutrition:

Species under Kingdom Plantae are chiefly self-sustainable and synthesize their food using light energy through the process of photosynthesis. They have chloroplasts, which contain chlorophylls and other pigments that attract light energy.

Cell structure:

The plant cells are distinguished by having a rigid cell wall made mostly of cellulose which plays the role of the protector and frame of the cell. They are also autotrophs and undergo photosynthesis through chloroplasts found in the cells which assist in the change of light energy to chemical energy.

Reproduction:

Sexual as well as asexual reproduction occurs in plants. Meiosis is the process of sexual reproduction through the formation of gametes; eggs and sperm. Fertilization is the process where sperm fertilizes an egg, or in plants, it is the formation of a zygote which works to grow a brand new plant. One of the forms of reproduction is asexual reproduction, which plays a variety of techniques including fragmentation, budding and production of structures like bulbs or runners.

Life cycle and alternation of generations:

In their life cycle, plants show a process known as alternation of generations in which the plants seem to switch between haploid or gametophyte and diploid or sporophyte generations. The gametophyte undergoes mitosis to manufacture gametes, on the other hand, the sporophyte undergoes meiosis to produce spores. Germination of spores takes place to form the gametophytes which in a way is the end of the life cycle.

Classification Of Plantae

Plants in Kingdom Plantae are classified into several major groups based on their evolutionary relationships and distinguishing characteristics:

Bryophytes

Characteristics: Bryophytes are those plants which have no vascular tissue means plants which have no specialised tissue structure for the conduction of water and Mineral nutrients. These are the mosses, liverworts and hornworts, and they mainly grow in wet places.

Reproduction: Bryophytes reproduce by spores; the gametophyte stage is dominant in the life cycle of plants belonging to this division.

Pteridophytes

Characteristics: Pteridophytes are nonflowering plants that include plants characterized by vascular tissue and reproduce through spores. They are ferns and horsetails and have developed root, stem and leaves (frond) structures.

Reproduction: Brittle fern-like vascular plants also have a large and dominant sporophyte generation and spores are formed in a special organ known as sporangia which lie on the underside of the fronds.

Gymnosperms

Characteristics: Gymnosperms are seeds producing plants that have their seeds laid open or, naked on the surface. These are conifers such as pines spruces and cycads.

Reproduction: Conifers or Gymnosperms produce neither flowers, nor they have cones or any other organs from which seeds grow. They are generalised to different climates and many of them are of an evergreen type.

Angiosperms

Characteristics: Angiosperms are large groups of flowering plants in which seeds are contained within a fruit. They come in all shapes and sizes and are ranked from the smallest plants, which are herbs, to the largest plants, which are trees.

Reproduction: Angiosperms have flowers involved in sexual reproduction since this is involved in the production of seeds which have animals such as insects, birds, and mammals. They control the earth's space and are essential in food production and other ecosystem services.

Kingdom Animalia

The Kingdom Animalia is described below-

Characteristics of Animalia

Heterotrophic nutrition:

Organisms in 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 they go through a series of developmental stages including fertilization, cleavage, gastrulation and organogenesis. This occurrence results in the creation of specialized tissues, organs, and body structures in the developing organism.

Classification Of Animalia

Invertebrates vs Vertebrates

Invertebrates: These animals do not possess a vertebral column or backbone. These are the largest group of the animal family and its 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.

Major phyla

• Porifera: This group of animals is comparatively unsophisticated and inhabits the ocean and seas being small animals with a porous body structure possessing special cells for water filtration and nutrition.

• Cnidaria: Jellyfish, corals, and sea anemones possessing radial symmetry, body appendages containing stinging cells known as cnidocytes, and a central digestive chamber called the gastrovascular cavity.

• Platyhelminthes: Flatworms are animals belonging to the phylum Platyhelminthes; they are soft-bodied animals belonging to the group bilaterians but being at the simplest level of organ-systems complexing. It is subdivided into free-living and parasitic ones.

• Nematoda: The roundworms are non-segmented, tubular and possess a pseudo coelom cavity and a definite mouth and anus. They are present in various environments as either end-independent individuals or as parasites.

• Annelida: Worms with an internal body cavity, or coelom: these are earthworms and leeches. They show compartmentation both from the exterior and the interior, with consequently organs and systems.

• Arthropoda: It is the biggest phylum and it encompasses bugs, spiders, lobster, and other kinds of life forms. These animals have a tough external covering known as the exoskeleton, which consists of chitin, and their body is divided and their appendages are jointed.

• Mollusca: Tend to be animals of soft and fleshy body structure, and muscular foot and mantle; have a shell that is usually made of calcium carbonate. Cephalopods comprise snails, clams, squids, and octopuses distinguishing how they feed and live.

• Echinodermata: Adult marine invertebrates having a body plan with pentaradial symmetry, having a water vascular system, tube feet and a calcium carbonate endoskeleton. Some of the species that are included are the starfish, the sea urchins and sea cucumbers.

• Chordata: Animals which have a notochord in at least one phase of their development, for instance, a spine in vertebrates. Comprises fish, amphibians, reptiles, birds, and mammals as well as non-vertebrates like tunicates and lancelets.

Viruses

Viruses are described below-

Characteristics Of Viruses

Non-cellular structure

A virus is a submicroscopic agent, made up of a nucleic acid core of DNA or RNA surrounded by a protein shell known as the capsid. Some viruses also may have an outer lipid envelope which arises from the host cells’ membrane.

Dependence on host cells for replication

Most Viruses cannot self-replicate, thus they need host cells to make more of it in what we call replication. They enter animal cells and parasite the host’s existing resources and equipment to produce multiple copies of the virus and new virus particles.

Structure

Capsid:

The viral casing made of protein is known as capsid and this covers the viral nucleic acids. Icosahedral, helical, complexes etc It play a key role in virus stability and its interaction with host cells.

Genetic Material:

A virus may have DNA or RNA, single or double, line or circular and either has a single sense or stranded. It contains the information related to the replica and infection of the virus.

Classification Of Viruses

DNA vs RNA viruses

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 synthesize an mRNA and retroviruses-which use reverse transcriptase to synthesize DNA. Examples include Influenza viruses such as A and B, Hepatitis C viruses, and HIV viruses.

Types of hosts

Bacteriophages (Phages): Bacteriophages that are responsible for infecting bacteria. Bacteriophages are large and composed of two parts and can either destroy the host cell or become permanent inhabitants of the nucleus of the host cell.

Plant Viruses: Plant pathogens; Viruses which affect plants and lead to diseases that affect farming and crop growing. Some examples of the bare viruses include the Tobacco mosaic virus (TMV), and Potato virus Y (PVY).

Animal Viruses: Viral pathogens that occur in animals, particularly in mammals. Animal viruses affect almost all aspects of health ranging from flu to AIDS (HIV) and COVID-19 (SARS-CoV-2).

Virus Life Cycle

Viruses have a life cycle which outlines how they replicate and move within the host cells:

Lytic cycle

• Attachment: This virus can bind itself to receptors on the membrane of the host cell.

• Entry: Depending on the specific virus the genetic material of the virus enters into the host cell by injecting it with either DNA or RNA.

• Replication and Transcription: Rather than being killed, the material gets into the host cell and makes the cell learn to divide as it replicates the viral genes.

• Assembly: New viral components are synthesized and accumulated for the assembly of new virus particles Several new viral components are created and contribute to the formation.

• Release: This results in the lysis of the host cell and out of them emerges new virions that can spread the disease in the whole body.

Lysogenic cycle

• Attachment and Entry: Like the lytic cycle the virus binds to the host cell and injects its material into the cell.

• Integration: Rather than directly making a copy of itself and giving rise to new virgins, the viral genome becomes encapsidated within a bacterial host cell chromosome as prophage or animal host cell chromosome as provirus.

• Replication with Host Genome: E. G the integrated viral DNA is synthesized simultaneously with host DNA during cell division and it does not harm the host at this stage.

• Induction: In some cases, for example under stress or when they perceive certain signals in their environment, the provirus can change its form of functioning to the lytic cycle and begin replication and formation of new viruses.

Examples of viruses (HIV, Influenza, COVID-19)

• HIV (Human Immunodeficiency Virus): IProvokes and kills lymphocytes resulting in the acquired immunodeficiency syndrome (AIDS).

• Influenza Virus: Their work is to cause seasonal flu, which has respiratory manifestations.

• COVID-19 (SARS-CoV-2): Causing the current coronavirus disease or COVID-19, it affects the respiratory tract and may present with symptoms right from a cold up to severe manifestations.

Comparative Analysis

Plantae and Animalia vs Viruses