Biological Classification Basis: Overview, Importance, Types and FAQ

What is Biological Classification?

Biological classification is the way by which we categorize living organisms based on their similarities in terms of structure and genetics. This system brings order to the many forms of life found on the planet. The early classifiers like Aristotle and Linnaeus were keen on physical features which paved the way for the more modern taxonomic classification of today. The modern classification does not just consider the physical resemblance but also their genetic relationships and evolutionary history that would enable scientists to understand all these connections and diversity.

History of Biological Classification

The history of biological classification is as follows:

Aristotle: Earlier, living organisms were divided into two kingdoms: Animalia and Plantae. The kingdom Plantae included all those species that can produce their own food from inorganic substances. These are the ones known to be autotrophs.

Carl Linnaeus: Systema Naturae propounded the existing taxonomic system with categorized hierarchies and binomial nomenclature for the naming of species.

Ernst Haeckel: In 1866, taxonomist Ernst Haeckel expanded on this system by inventing a third kingdom, Protista, to house such species as Euglena and also include bacteria. Fungi remained under Plantae in this stage.

Robert Whittaker: The classification evolved further through the improvement of the system designed by Robert Whittaker in 1967 into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. The latter was then further developed by Margulis and Schwartz in 1988 as being divided into prokaryotes and eukaryotes.

Basis of Biological Classification

The following key characteristics formed the Biological classification basis:

Morphological Characteristics

• Morphological characteristics form the external features of organisms, which include shape, size and colour:

• Early taxonomy relied on these visible characteristics in the arrangement of similar species.

For example

• Plants: Compared based on broad leaves and needle-shaped leaves.

• Animals: Limbs used for specific functions, such as wings to fly or legs to walk.

Anatomical and Physiological Characteristics

It considers structure as well as function within the organisms with an emphasis on organs, tissues, and cells required for survival.

Homologous Structures: Organs that share a common evolutionary origin, though they often function for different purposes.

Example: The forelimb in mammals.

Analogous Structures: Organs that perform similar functions, but the fundamental structures do not match.

Example: Wings of birds and wings of bees.

Genetic and Molecular Basis

DNA Sequencing: By using next-generation sequencing, scientists are capable of determining exact genetic sequences.

SNPs: These are single nucleotide polymorphisms that aid in genetic trait mapping and analyzing differences within populations.

Evolutionary Relationships: Genetic analysis provides an essential tool to be able to know how species are related and how they have come to evolve through time.

Phylogenetic Trees and Cladograms: These diagrams depict the evolutionary relationships of species illustrating where species diverge over time.

Embryological Evidence

Developmental Stages: Having similarities in embryonic development stages, such as cleavage and gastrulation, across different species testifies to the theory of evolution and indicates common ancestry.

Comparison Across Species: Embryos from different animals exhibit similarities that testify to the theory of evolution that those organisms share a common ancestor but adapt to their environment.

Key Characteristics for Biological Classification

Some key characteristics of biological classification basis are:

Cellular structure: Organisms are made up of cells. In some, it is unicellular, for instance, bacteria while others are multicellular, for example, plants and animals.

Nutrition: Organisms produce food differently. While plants synthesize food through photosynthesis, animals draw energy by feeding on it.

Body Plan and Organisation: The body parts among plants and animals are different which gives way to sub-classifications because of specific features.

Reproductive Mechanisms: Organisms either reproduce sexually or asexually, which decides how they should be classified.

Genetic Information: Genetic makeup and sequence of DNA prove essential in determining relationships among different species.

Adaptation: Specific changes that help organisms to survive in different environments like desert or aquatic adaptation also can work as classification criteria.

Stages of Life Cycles: The relative development stages of the organisms help in the classification.

Significance of Biological Classification

Organisation of Knowledge: Biological classification is intended to systematise a vast diversity of living organisms in such a way that they can be well analyzed and understood.

Identification and Naming: It helps one identify and correctly name organisms thereby cutting on confusion in scientific communication.

Facilitates Research: Proper classification promotes more communication, information sharing, and elaboration of other persons' work on research topics concerning ecology, genetics, and medicine.

Conservation: The naming of organisms plus their classification helps biologists in knowing the species and ecosystems which may require preservation and most importantly, those endangered.

Tool for education: Biological classification is one of the most important educational tools that students utilise to understand complex biology while building better skills in life sciences.

Tips, Tricks & Strategies

Here are some tricks to study biological classification basis for exams:

For Basis of Classification

"Mighty Animals Generate Embryos"

• Morphological characteristics (shape, size, colour)

• Anatomical and physiological characteristics (internal structures)

• Genetic and molecular basis (DNA, genetic markers)

• Embryological evidence (developmental stages)

Visual Aids: Use diagrams and charts that represent relationships and characteristics among different groups of organisms.

Flashcards: Create flashcards with each characteristic and test yourself.

Basis of Biological Classification NEET MCQs

Q1. The level of organization of organisms according to the five kingdom classification is:

1. Cellularity

2. Mode of Nutrition

3. Prokaryotic or Eukaryotic

4. All of the above

Correct answer: 4) All of the above

Explanation:

The level of organization in the five-kingdom classification is based on key factors such as cellularity (unicellular or multicellular), mode of nutrition (autotrophs or heterotrophs), and whether the organisms are prokaryotic (lacking a true nucleus) or eukaryotic (possessing a true nucleus). Organisms are classified into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. The classification helps in understanding the complexity and characteristics of life forms, from simple unicellular organisms to complex multicellular organisms. It also reflects the diversity in metabolic processes, from photosynthesis in plants to ingestion in animals. The level of organization in the five kingdom classification is:

1. Cellularity( unicellular,muiticellular)

2. Mode of nutrition ( autotrophs, heterotrophs)

3. Prokaryotic or Eukaryotic

Hence, the correct answer is option 4) All of the above

Q2. Phylogenetic system of classification is based on :

1. Morphological features

2. Chemical constituents

3. Floral characters

4. Evolutionary relationships

Correct answer: 4) Evolutionary relationships

Explanation:

The phylogenetic tree depicts the relationships between species based on their shared ancestors. The phylogenetic tree depicts the relationships between species based on their shared ancestors, illustrating evolutionary history. Each branching point, or node, represents a common ancestor, while the branches show the divergence of species over time. This tree helps in understanding how different species are related to each other and can be used to trace the lineage of various traits or characteristics. Phylogenetic trees are constructed using molecular data, such as DNA sequences, to determine the degree of relatedness among species.

Hence, the correct answer is option 4) Evolutionary relationships

Q3. How many kingdoms in Whittaker’s classification system involves organisms with only heterotrophic nutrition?

1. 2

2. 4

3. 3

4. 1

Correct answer: 1) 2

Explanation:

Kingdom fungi and Animalia are strictly heterotrophic in nutrition. Both fungi and animals rely on external sources of organic material for nourishment, as they cannot produce their food through photosynthesis. Fungi absorb nutrients from decaying organic matter through a process known as external digestion, while animals ingest and digest food internally. Fungi obtain their food by secreting enzymes into their environment, breaking down complex substances, and absorbing the simpler molecules. Animals, on the other hand, consume and digest food in a digestive system, breaking it down into usable nutrients.

Hence, the correct answer is option 1) 2.

Also Read:

• MCQs on Classification Systems

• Taxonomy Hierarchy

• Taxonomical Aids

FAQs on Basis of Biological Classification

What is biological classification?

Biological classification is the method of classifying and naming organisms into categories on the basis of similarities and differences. This helps biologists study organisms systematically and understand their evolutionary relationships.

What is the basis of biological classification?

The basis of classification has changed over time. Initially, external morphology (size, color, shape) was used. Later, anatomical features, modes of reproduction, and physiology were considered. In modern times, molecular characters such as DNA, RNA, proteins, and evolutionary history are taken as the most reliable basis for classification.

What are homologous and analogous organs with examples?

Homologous structures display similarities in form but they have different functions. Thereby suggesting that they share a common evolutionary ancestry. For example, the morphological similarities in human arm bones, cat legs, whale flippers and bat wings all reflect their common vertebrate ancestry.

Analogous structures are an example of convergent evolution. In this, unrelated species adapt similar organs to address similar challenges. For example, the wings of bats, birds, and insects are analogous organs structurally different but functionally similar.

Why is classification important?

• It makes the study of millions of organisms easier and systematic.

• It helps in correct identification and naming of organisms.

• It shows the evolutionary and genetic relationships between groups.

• It is useful in fields like medicine, agriculture, forestry, and environmental conservation.

• It avoids confusion among scientists and uses a universal naming system.

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