What Living
Living organisms are defined by a set of characteristics that distinguish them from non-living entities. These characteristics include:
· Cellular Organization: All living things are composed of cells, which are the basic units of life.
· Metabolism: Living organisms undergo various biochemical processes to convert food into energy, involving both anabolic (building up) and catabolic (breaking down) reactions.
· Growth and Development: Organisms grow and develop according to specific instructions coded in their genes.
· Reproduction: Living entities have the ability to reproduce, either sexually or asexually, ensuring the continuation of their species.
· Response to Stimuli: Living organisms can respond to environmental changes or stimuli, which is crucial for survival.
· Homeostasis: They maintain a stable internal environment despite external changes.
· Adaptation: Over time, living organisms evolve and adapt to their environments through natural selection.
2. Biodiversity
Biodiversity, or biological diversity, refers to the variety of life on Earth at all its levels, including genetic diversity, species diversity, and ecosystem diversity. It encompasses:
· Genetic Diversity: Variability in genes within a species, which allows populations to adapt to changing environments.
· Species Diversity: The variety of species within a particular habitat or ecosystem. High species diversity often indicates a healthy ecosystem.
· Ecosystem Diversity: The range of different ecosystems found within a region, including forests, wetlands, grasslands, and deserts.
Importance of Biodiversity
Biodiversity is crucial for several reasons:
· Ecological Balance: It supports processes like pollination, seed dispersal, nutrient cycling, and soil formation.
· Economic Value: Biodiversity provides resources for food, medicine, and materials. For example, many pharmaceuticals are derived from plant compounds.
· Cultural Significance: Many cultures derive spiritual and aesthetic values from biodiversity; certain species hold cultural importance in various traditions.
3. Need for Classification
Classification is essential in biology for several reasons:
· Organization of Knowledge: It helps scientists organize and categorize the vast diversity of life forms based on shared characteristics.
· Identification: Classification aids in identifying organisms accurately and understanding their relationships with one another.
· Communication: A standardized classification system allows scientists worldwide to communicate effectively about species without confusion.
4. Taxonomy & Systematics
Taxonomy is the science of naming, describing, and classifying organisms. It involves:
· Hierarchical Classification: Organisms are classified into a hierarchy that includes domains, kingdoms, phyla (or divisions), classes, orders, families, genera, and species.
· Systematics: This field studies the evolutionary relationships among organisms. It combines taxonomy with phylogenetics (the study of evolutionary history).
5. Concept of Species and
Taxonomical Hierarchy
A species is defined as a group of organisms that can interbreed and produce fertile offspring under natural conditions. The concept emphasizes reproductive isolation from other groups.
Taxonomical Hierarchy
The taxonomical hierarchy organizes life forms into ranked categories:
1. Domain: The highest rank; includes Archaea, Bacteria, and Eukarya.
2. Kingdom: Groups organisms based on fundamental traits (e.g., Animalia for animals).
3. Phylum/Division: Groups based on major body plans or organizational features.
4. Class: Further subdivides phyla into groups with more specific characteristics.
5. Order: Groups families that share common traits.
6. Family: Groups related genera.
7. Genus: A group of closely related species.
8. Species: The most specific level; individuals that can breed together.
6. Binomial Nomenclature
Binomial nomenclature is the formal system of naming species using two Latin words:
· The first word denotes the genus (capitalized).
· The second word denotes the specific epithet (not capitalized).
For example, in Homo sapiens:
· Homo is the genus.
· sapiens is the specific epithet.
This system was developed by Carl Linnaeus and provides a universal naming convention that reduces confusion caused by common names across different languages and regions.
These notes provide an overview of fundamental biological concepts related to living organisms, biodiversity, classification needs, taxonomy, species concepts, and naming conventions essential for understanding ecology and environmental science.
Biological Classification
1. Five Kingdom Classification
The five-kingdom classification was proposed by Robert Whittaker in 1969. It categorizes all living organisms into five distinct kingdoms based on characteristics such as cell structure, mode of nutrition, reproduction, and phylogenetic relationships.
The Five Kingdoms
1. Monera
o Includes prokaryotic unicellular organisms like bacteria and cyanobacteria.
o Characteristics:
§ No membrane-bound organelles (e.g., nucleus, mitochondria).
§ Cell wall made of peptidoglycan (murein).
§ Nutrition: Autotrophic (photosynthesis/chemosynthesis) or heterotrophic.
o Examples: Escherichia coli (E. coli), Anabaena.
2. Protista
o Eukaryotic unicellular or simple multicellular organisms.
o Characteristics:
§ Membrane-bound organelles present.
§ Found in aquatic or moist environments.
§ Nutrition: Autotrophic (e.g., algae) or heterotrophic (e.g., protozoa).
o Examples: Amoeba, Paramecium, Plasmodium.
3. Fungi
o Eukaryotic organisms with a chitinous cell wall.
o Characteristics:
§ Multicellular (except yeast).
§ Heterotrophic (saprophytic or parasitic).
§ Reproduce via spores.
o Examples: Mushrooms, molds, yeast.
4. Plantae
o Eukaryotic multicellular autotrophs.
o Characteristics:
§ Cell wall made of cellulose.
§ Contain chlorophyll for photosynthesis.
§ Reproduce sexually and asexually.
o Examples: Trees, flowering plants, algae.
5. Animalia
o Eukaryotic multicellular heterotrophs.
o Characteristics:
§ No cell wall.
§ Exhibit locomotion at some stage of life.
§ Complex organ systems present.
o Examples: Humans, birds, insects.
Advantages of Five Kingdom
Classification
· Separates prokaryotes (Monera) from eukaryotes.
· Distinguishes autotrophs from heterotrophs.
· Places fungi in a separate kingdom due to their unique mode of nutrition.
Limitations
· Does not include acellular organisms like viruses and viroids.
2. Salient Features and
Classification of Monera
Characteristics
· Prokaryotic unicellular organisms.
· Cell wall made of peptidoglycan (except in Archaebacteria).
· Lack membrane-bound organelles and nucleus; DNA is circular and naked.
· Reproduction is primarily asexual through binary fission or budding.
Classification
1. Archaebacteria:
o Extremophiles that live in harsh environments (e.g., high salt, temperature).
o Examples: Methanogens, halophiles.
2. Eubacteria:
o True bacteria with diverse metabolic capabilities.
o Examples: Escherichia coli, Streptococcus.
3. Cyanobacteria:
o Photosynthetic bacteria also known as blue-green algae.
o Examples: Anabaena, Nostoc.
3. Salient Features and
Classification of Protista
Characteristics
· Eukaryotic unicellular or simple multicellular organisms.
· Found in aquatic or moist environments.
· Show diverse modes of nutrition: autotrophic (e.g., algae), heterotrophic (e.g., protozoa), or mixotrophic (e.g., Euglena).
Classification
1. Chrysophytes:
o Golden algae and diatoms; autotrophic and photosynthetic.
o Example: Diatoms.
2. Dinoflagellates:
o Marine plankton with two flagella; some are bioluminescent.
o Example: Gonyaulax.
3. Euglenoids:
o Mixotrophic; autotrophic in light, heterotrophic in darkness.
o Example: Euglena.
4. Protozoa:
o Animal-like protists; heterotrophic and motile.
o Example: Amoeba, Paramecium.
5. Slime Molds:
o Fungus-like protists; feed on decaying organic matter.
o Example: Plasmodial slime molds.
4. Salient Features and
Classification of Fungi
Characteristics
· Eukaryotic organisms with a chitinous cell wall.
· Heterotrophic nutrition through saprophytism, parasitism, or symbiosis.
· Reproduce via spores; both sexual and asexual reproduction occur.
Classification
1. Zygomycetes:
o Produce zygospores during sexual reproduction.
o Example: Rhizopus (bread mold).
2. Ascomycetes:
o Sac fungi; produce ascospores in sac-like structures called asci.
o Example: Yeast (Saccharomyces), Penicillium.
3. Basidiomycetes:
o Club fungi; produce basidiospores on club-shaped basidia.
o Example: Mushrooms (Agaricus).
4. Deuteromycetes:
o Imperfect fungi; sexual reproduction is absent or unknown.
o Example: Alternaria.
5. Lichens
Lichens are symbiotic associations between fungi and algae/cyanobacteria:
Features
· Fungi provide protection and absorb nutrients from the environment.
· Algae/cyanobacteria perform photosynthesis to supply food to the fungus.
Types of Lichens
1. Crustose – Flat and crust-like (e.g., on rocks).
2. Foliose – Leaf-like structures.
3. Fruticose – Shrub-like bodies.
Importance
· Bioindicators of air pollution due to their sensitivity to sulfur dioxide levels.
· Used in dyes, medicines, and food for animals like reindeer.
6. Viruses and Viroids
Viruses
· Acellular entities consisting of genetic material (DNA/RNA) surrounded by a protein coat (capsid).
· Obligate intracellular parasites – can only replicate inside host cells.
Structure
1. Genetic Material – DNA or RNA (single-stranded or double-stranded).
2. Capsid – Protein shell protecting the genetic material; composed of capsomeres.
3. Envelope – Some viruses have an outer lipid envelope derived from the host cell membrane.
Examples
· DNA Virus: Adenovirus (common cold).
· RNA Virus: HIV (Human Immunodeficiency Virus).
Viroids
· Smallest known infectious agents composed solely of circular RNA molecules without a protein coat.
· Cause diseases in plants by interfering with normal gene expression.
Example
· Potato spindle tuber disease caused by viroids.
These detailed notes provide comprehensive coverage of the key topics related to biological classification for academic preparation!
Detailed Notes on Plant Classification:
Algae, Bryophytes, Pteridophytes, and Gymnosperms
1. Algae
Algae are simple, autotrophic, thalloid organisms that are primarily aquatic. They belong to the kingdom Plantae but lack true roots, stems, and leaves.
Salient Features
· Habitat: Found in freshwater, marine water, or moist terrestrial environments.
· Structure: Thalloid body without vascular tissues; can be unicellular (e.g., Chlamydomonas) or multicellular (e.g., Ulva).
· Nutrition: Autotrophic; contain chlorophyll for photosynthesis.
· Reproduction: Asexual (fragmentation, spores) and sexual (fusion of gametes).
· Economic Importance:
o Source of food (e.g., Porphyra).
o Produce oxygen during photosynthesis.
o Used in industries for agar extraction (Gelidium, Gracilaria).
Classification of Algae
1. Chlorophyceae (Green Algae):
o Contain chlorophyll a and b.
o Store food as starch.
o Example: Chlamydomonas, Spirogyra.
2. Phaeophyceae (Brown Algae):
o Contain chlorophyll a, c, and fucoxanthin.
o Store food as laminarin and mannitol.
o Example: Laminaria, Fucus.
3. Rhodophyceae (Red Algae):
o Contain chlorophyll a, d, and phycoerythrin.
o Store food as floridean starch.
o Example: Polysiphonia, Gelidium.
2. Bryophytes
Bryophytes are non-vascular plants that are often referred to as "amphibians of the plant kingdom" because they require water for reproduction.
Salient Features
· Habitat: Moist and shady terrestrial environments.
· Structure: Lack true roots, stems, and leaves; possess rhizoids for anchorage.
· Reproduction:
o Dominant gametophyte stage; sporophyte is dependent on the gametophyte.
o Require water for fertilization (motile sperms).
· Economic Importance:
o Soil formation and prevention of soil erosion (Sphagnum moss used as peat).
Classification of Bryophytes
1. Liverworts:
o Flattened thalloid bodies or leafy structures.
o Example: Marchantia, Riccia.
2. Mosses:
o Leafy gametophytes with spirally arranged leaves.
o Example: Funaria, Polytrichum.
3. Pteridophytes
Pteridophytes are vascular plants with well-differentiated roots, stems, and leaves but reproduce via spores instead of seeds.
Salient Features
· Habitat: Prefer damp, shady places; some are aquatic (Azolla).
· Structure:
o Possess vascular tissues (xylem and phloem).
o Sporophyte is the dominant phase.
· Reproduction:
o Spore-producing plants with alternation of generations.
o Water is required for fertilization.
· Economic Importance:
o Used as ornamental plants (Adiantum).
o Nitrogen-fixing ability in symbiosis (Azolla-Anabaena).
Classification of Pteridophytes
1. Lycopsida (Club Mosses):
o Small plants with microphyllous leaves.
o Example: Selaginella, Lycopodium.
2. Sphenopsida (Horsetails):
o Jointed stems with silica deposits.
o Example: Equisetum.
3. Pteropsida (Ferns):
o Large fronds with sori on the underside of leaves.
o Example: Adiantum, Dryopteris.
4. Gymnosperms
Gymnosperms are seed-producing plants where seeds are not enclosed within fruits ("naked seeds"). They are mostly woody trees or shrubs.
Salient Features
· Habitat: Mostly terrestrial; adapted to cold climates with needle-like leaves to reduce water loss.
· Structure:
o Well-developed vascular tissues but lack companion cells in phloem.
o Dominant sporophyte phase; gametophyte is reduced and dependent on sporophyte.
· Reproduction:
o Seeds are produced but not enclosed in fruits.
o Pollination is mostly wind-mediated (anemophilous).
· Economic Importance:
o Timber production (Pinus, Cedrus).
o Resin extraction (Pinus), ornamental plants (Cycas).
Classification of Gymnosperms
1. Cycadophyta (Cycads):
o Palm-like appearance with unbranched stems.
o Dioecious plants with large cones.
o Example: Cycas, Zamia.
2. Coniferophyta (Conifers):
o Needle-shaped leaves; mostly evergreen trees or shrubs.
o Example: Pinus, Cedrus.
3. Gnetophyta:
o Advanced gymnosperms with features similar to angiosperms (e.g., vessels in xylem).
o Example: Gnetum, Ephedra.
Summary Table
|
Group |
Salient
Features |
Examples |
|
Algae |
Aquatic autotrophs; thalloid body; photosynthetic pigments
vary by group |
Chlamydomonas, Ulva |
|
Bryophytes |
Non-vascular; dominant gametophyte phase; require water
for reproduction |
Marchantia, Funaria |
|
Pteridophytes |
Vascular plants; spore-producing; dominant sporophyte
phase |
Selaginella, Adiantum |
|
Gymnosperms |
Seed-producing without fruits; needle-like leaves; wind
pollination |
Pinus, Cycas |
Animal Classification: Non-Chordates and
Chordates
1. Non-Chordates
Non-chordates are animals without a notochord (a flexible rod-like structure). They include a wide range of invertebrates classified into different phyla based on their body structure, symmetry, and other features.
Salient Features of Non-Chordates
· Lack a notochord at any stage of life.
· Exhibit various levels of body organization: cellular, tissue, or organ-system level.
· Can have radial or bilateral symmetry.
· Reproduction is mostly sexual, with external fertilization being common.
· Circulatory systems can be open or absent.
Classification of Non-Chordates (Up
to Phyla Level)
1. Phylum Porifera (Sponges):
o Simplest multicellular animals with a cellular level of organization.
o Body has pores (ostia) for water flow; internal skeleton made of spicules or spongin.
o Example: Sycon, Spongilla.
2. Phylum Coelenterata (Cnidaria):
o Radially symmetrical, diploblastic animals with a tissue-level organization.
o Possess cnidoblasts (stinging cells) for defense and capturing prey.
o Example: Hydra, Jellyfish (Aurelia).
3. Phylum Ctenophora (Comb Jellies):
o Marine, radially symmetrical animals with eight rows of ciliary comb plates for locomotion.
o Bioluminescent and diploblastic.
o Example: Pleurobrachia, Ctenoplana.
4. Phylum Platyhelminthes (Flatworms):
o Bilaterally symmetrical, triploblastic, acoelomate animals.
o Parasitic or free-living; exhibit organ-level organization.
o Example: Planaria, Taenia (tapeworm).
5. Phylum Aschelminthes (Nematoda):
o Bilaterally symmetrical, triploblastic, pseudocoelomate animals.
o Cylindrical body covered by a tough cuticle; parasitic or free-living.
o Example: Ascaris (roundworm), Wuchereria.
6. Phylum Annelida:
o Bilaterally symmetrical, triploblastic, coelomate animals with segmented bodies.
o Closed circulatory system; locomotion via setae or parapodia.
o Example: Earthworm (Lumbricus), Leech (Hirudinaria).
7. Phylum Arthropoda:
o Largest phylum; bilaterally symmetrical, triploblastic, coelomate animals with jointed appendages and exoskeleton made of chitin.
o Open circulatory system; highly diverse group.
o Example: Prawn, Butterfly.
8. Phylum Mollusca:
o Soft-bodied, bilaterally symmetrical coelomates with a calcareous shell and muscular foot for locomotion.
o Open circulatory system; respiration through gills or lungs.
o Example: Pila (apple snail), Octopus.
9. Phylum Echinodermata:
o Marine animals with radial symmetry in adults and bilateral symmetry in larvae; triploblastic and coelomate.
o Water vascular system aids in locomotion and feeding.
o Example: Starfish (Asterias), Sea urchin.
10. Phylum Hemichordata:
o Worm-like marine animals with a rudimentary notochord-like structure called stomochord.
o Bilaterally symmetrical and coelomate with open circulatory systems.
o Example: Balanoglossus, Saccoglossus.
2. Chordates
Chordates are characterized by the presence of a notochord at some stage during development. They also possess a dorsal hollow nerve cord and pharyngeal gill slits.
Salient Features of Chordates
· Bilaterally symmetrical, triploblastic, coelomate animals with an organ-system level of organization.
· Presence of notochord at least during embryonic development.
· Closed circulatory system and post-anal tail present in most members.
Classification of Chordates
1. Subphylum Urochordata (Tunicata):
o Marine animals with a notochord present only in the larval tail stage; adults are sessile and covered by a tunic-like covering.
o Example: Ascidians, Doliolum.
2. Subphylum Cephalochordata:
o Marine animals with a notochord extending throughout the body length in both larval and adult stages; exhibit fish-like body structure.
o Example: Amphioxus (Branchiostoma).
3. Subphylum Vertebrata:
o Notochord is replaced by the vertebral column in adults; possess a well-developed brain and paired appendages for locomotion.
Classification of Vertebrates (Up to
Classes Level)
1. Class Pisces (Fishes):
o Aquatic animals with gills for respiration and fins for movement; cold-blooded with streamlined bodies.
o Skeleton may be cartilaginous (Shark) or bony (Rohu).
o Examples: Dogfish (Scoliodon), Rohu (Labeo rohita).
2. Class Amphibia:
o Cold-blooded animals that live both on land and water; moist skin aids in cutaneous respiration along with lungs or gills.
o Lay eggs in water; external fertilization is common.
o Examples: Frog (Rana), Salamander (Ambystoma).
3. Class Reptilia:
o Cold-blooded terrestrial animals with dry scaly skin; breathe through lungs and lay shelled eggs on land.
o Examples: Snake (Naja), Tortoise (Testudo).
4. Class Aves (Birds):
o Warm-blooded animals adapted for flight; forelimbs modified into wings and body covered with feathers.
o Lay hard-shelled eggs; possess beaks instead of teeth.
o Examples: Pigeon (Columba), Crow (Corvus).
5. Class Mammalia:
o Warm-blooded vertebrates with mammary glands for feeding young ones; body covered by hair or fur.
o Give birth to live young ones (except monotremes like platypus).
o Examples: Human (Homo sapiens), Tiger (Panthera tigris).
Summary Table
|
Group |
Salient
Features |
Examples |
|
Non-Chordates |
Lack notochord; radial/bilateral symmetry; open/absent
circulatory system |
Earthworm, Starfish |
|
Urochordata |
Marine; notochord only in larval tail |
Ascidians, Doliolum |
|
Cephalochordata |
Fish-like marine animals; notochord throughout life |
Amphioxus |
|
Pisces |
Aquatic vertebrates with fins and gills |
Dogfish, Rohu |
|
Amphibia |
Moist skin; live on land and water |
Frog, Salamander |
|
Reptilia |
Scaly skin; cold-blooded |
Snake, Tortoise |
|
Aves |
Warm-blooded birds adapted for flight |
Pigeon, Crow |
|
Mammalia |
Warm-blooded mammals with mammary glands |
Human, Tiger |
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