What is Living? Classifying Life

• Biology is the science of life forms and living processes.

What is Living?

• Living organisms grow, reproduce, sense and respond to the environment, maintain homeostasis, and metabolize.
• Growth involves an increase in mass and number of cells.
• Reproduction is the production of new organisms, either sexually or asexually.
• Metabolism involves the sum total of all chemical reactions that occur within a living organism.
• Consciousness (awareness of surroundings) is a defining property of living organisms.
• Living organisms exhibit self-replication, self-organization, response to stimuli, and emergence.

Diversity in the Living World

• Biodiversity refers to the variety of living organisms present on Earth.
• Nomenclature is the system of naming organisms with a unique scientific name.
• Identification is the process of characterizing organisms.
• Classification is the arrangement of organisms into groups or categories based on similarities and differences.
• Systematics is the study of diversity of organisms and their evolutionary relationships.

Taxonomic Categories

• Taxonomy involves classifying organisms into different ranks.
• Species is the basic unit of classification, representing a group of similar individuals that can interbreed.
• Genus is a group of related species.
• Family is a group of related genera.
• Order is a group of related families.
• Class is a group of related orders.
• Phylum (for animals) / Division (for plants) is a group of related classes.
• Kingdom is the highest level of classification, grouping together related phyla/divisions.

Taxonomic Aids

• Taxonomic keys are tools used for identification based on contrasting characters.
• Specimens are preserved in museums and herbaria.
• Herbaria are repositories of preserved plant specimens.
• Botanical gardens are collections of living plants for reference and study.
• Zoological parks (zoos) are places where wild animals are kept in protected environments.

The Living World - Three Domains of Life

• Living world is divided into three domains: Bacteria, Archaea, and Eukarya.
• These domains were created based on differences in ribosomal RNA structure.
• Bacteria and Archaea are prokaryotes, while Eukarya includes eukaryotes.

Biological Classification

• Whittaker proposed five kingdom classification: Monera, Protista, Fungi, Plantae, and Animalia.

Kingdom Monera

• Monera includes prokaryotic organisms (bacteria, archaea, cyanobacteria).
• Bacteria are classified based on their shape: coccus (spherical), bacillus (rod-shaped), vibrio (comma-shaped), and spirillum (spiral).
• Bacteria can be autotrophic (synthesize their own food) or heterotrophic (obtain food from other sources).
• Archaea are found in extreme environments (e.g., hot springs, salty areas).
• Mycoplasma lack a cell wall.

Kingdom Protista

• Protista includes unicellular eukaryotic organisms.
• Protists can be autotrophic or heterotrophic.
• Protists include:
  • Chrysophytes (diatoms and golden algae)
  • Dinoflagellates
  • Euglenoids
  • Slime molds
  • Protozoans

Kingdom Fungi

• Fungi are eukaryotic, heterotrophic organisms.
• Most fungi are multicellular.
• Fungi have cell walls made of chitin.
• Fungi can be saprophytic (feed on dead organic matter) or parasitic (obtain nutrients from living organisms).
• Fungi include:
  • Phycomycetes
  • Ascomycetes
  • Basidiomycetes
  • Deuteromycetes

Kingdom Plantae

• Plantae includes eukaryotic, multicellular, photosynthetic organisms (plants).
• Plant cells have cell walls made of cellulose.
• Plants include:
  • Algae
  • Bryophytes
  • Pteridophytes
  • Gymnosperms
  • Angiosperms

Kingdom Animalia

• Animalia includes eukaryotic, multicellular, heterotrophic organisms (animals).
• Animals lack cell walls.
• Animals exhibit diverse modes of nutrition, reproduction and locomotion.

Viruses

• Viruses are non-cellular organisms.
• Viruses consist of a protein coat (capsid) and genetic material (DNA or RNA).
• Viruses are inert outside a host cell but replicate inside a host cell.
• Viroids are infectious RNA particles, lacking a protein coat.
• Prions are infectious proteins that cause neurological diseases.

Plant Kingdom - Algae

• Algae are chlorophyll-bearing, simple, thalloid, autotrophic, and aquatic organisms.
• Algae are classified into:
  • Chlorophyceae (green algae)
  • Phaeophyceae (brown algae)
  • Rhodophyceae (red algae)

Plant Kingdom - Bryophytes

• Bryophytes are plants that live in moist habitats and are often called amphibians of the plant kingdom.
• Bryophytes lack true roots, stems, and leaves.
• Bryophytes include:
  • Liverworts
  • Mosses

Plant Kingdom - Pteridophytes

• Pteridophytes are vascular plants with true roots, stems, and leaves.
• Pteridophytes require water for fertilization.
• Pteridophytes include:
  • Ferns
  • Horsetails

Plant Kingdom - Gymnosperms

• Gymnosperms are seed-bearing plants with naked seeds (seeds not enclosed in an ovary).
• Gymnosperms include:
  • Conifers (e.g., pines, firs)
  • Cycads

Plant Kingdom - Angiosperms

• Angiosperms are flowering plants with seeds enclosed in fruits.
• Angiosperms are the most diverse group of plants.
• Angiosperms are divided into:
  • Dicotyledons (two cotyledons)
  • Monocotyledons (one cotyledon)

Animal Kingdom - Basis of Classification

• Animals are classified based on:
  • Levels of organization (cellular, tissue, organ, organ system)
  • Symmetry (asymmetry, radial symmetry, bilateral symmetry)
  • Diploblastic or triploblastic organization
  • Coelom (acoelomate, pseudocoelomate, coelomate)
  • Segmentation (metamerism)
  • Notochord

Animal Kingdom - Non-chordates

• Animals without a notochord:
  • Porifera (sponges)
  • Coelenterata (cnidarians)
  • Ctenophora (comb jellies)
  • Platyhelminthes (flatworms)
  • Aschelminthes (roundworms)
  • Annelida (segmented worms)
  • Arthropoda (insects, spiders, crustaceans)
  • Mollusca (snails, clams, squids)
  • Echinodermata (starfish, sea urchins)
  • Hemichordata

Animal Kingdom - Chordates

• Animals with a notochord.
• Chordates have:
  • Notochord
  • Dorsal hollow nerve cord
  • Pharyngeal gill slits
  • Post-anal tail
• Chordates include:
  • Urochordata
  • Cephalochordata
  • Vertebrata (fish, amphibians, reptiles, birds, mammals)

Morphology of Flowering Plants

• Morphology is the study of the form and features of different plant parts.
• Root:
  • Types of root systems: tap root and fibrous root.
  • Functions: absorption of water and minerals, anchorage, storage.
  • Modifications: storage, nitrogen fixation, support.
• Stem:
  • Functions: support, conduction, storage.
  • Modifications: storage, protection, vegetative propagation.
• Leaf:
  • Parts: leaf base, petiole, lamina.
  • Venation: reticulate and parallel.
  • Types: simple and compound.
  • Phyllotaxy: alternate, opposite, whorled.
  • Modifications: food storage, protection, support.
• Inflorescence:
  • Arrangement of flowers on a floral axis: racemose and cymose.
• Flower:
  • Parts: calyx, corolla, androecium, gynoecium.
  • Symmetry: actinomorphic and zygomorphic.
  • Ovary position: hypogynous, perigynous, epigynous.
  • Aestivation: valvate, twisted, imbricate, vexillary.
• Fruit:
  • Developed from the ovary.
  • Types: simple, aggregate, composite.
• Seed:
  • Parts: seed coat, cotyledons, embryo axis.
  • Dicot and monocot seeds.
• Floral Formula and Floral Diagram:
  • Symbolic representation of flower characteristics.

Anatomy of Flowering Plants

• Anatomy is the study of the internal structure of plants.
• Tissues:
  • Meristematic tissues: apical, lateral, intercalary.
  • Permanent tissues: simple (parenchyma, collenchyma, sclerenchyma) and complex (xylem, phloem).
• Tissue System:
  • Epidermal tissue system: epidermis, stomata, epidermal appendages.
  • Ground tissue system: parenchyma, collenchyma, sclerenchyma.
  • Vascular tissue system: xylem and phloem.
• Anatomy of Dicotyledonous and Monocotyledonous Plants:
  • Root: differences in arrangement of vascular bundles and presence/absence of pith.
  • Stem: differences in arrangement of vascular bundles and presence/absence of cambium.
  • Leaf: differences in mesophyll tissue (dorsiventral vs. isobilateral).
• Secondary Growth:
  • Formation of vascular cambium and cork cambium.
  • Heartwood and sapwood.

Cell: The Unit of Life

• Cell theory states: all living organisms are composed of cells and cell is the basic unit of life.
• Cell Structure:
  • Prokaryotic cells: lack a membrane-bound nucleus and organelles.
    • Cell envelope: glycocalyx, cell wall, plasma membrane.
    • Cytoplasm: genetic material (nucleoid), ribosomes, inclusions.
    • Appendages: flagella, pili, fimbriae.
  • Eukaryotic cells: have a membrane-bound nucleus and organelles.
    • Cell wall (in plant cells).
    • Cell membrane.
    • Cytoplasm: organelles (endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, plastids, ribosomes).
    • Nucleus: nuclear membrane, nucleolus, chromatin.
• Cell Organelles:
  • Endoplasmic Reticulum (ER): smooth ER and rough ER (RER).
  • Golgi Apparatus: packaging and secretion.
  • Lysosomes: digestive enzymes.
  • Vacuoles: storage, turgor pressure.
  • Mitochondria: ATP production (cellular respiration).
  • Plastids: chloroplasts (photosynthesis), chromoplasts, leucoplasts.
  • Ribosomes: protein synthesis.
• Cytoskeleton:
  • Microtubules, microfilaments, intermediate filaments.
  • Functions: cell shape, motility.
• Cilia and Flagella:
  • Hair-like structures for movement.
• Centrosome and Centrioles:
  • Cell division.
• Nucleus:
  • Control center of the cell.
  • Nuclear membrane, nucleolus, chromatin.
• Biomolecules:
  • Nucleic Acids: DNA and RNA.

Biomolecules

• Biomolecules are organic molecules that are essential for life.
• Carbohydrates:
  • Monosaccharides, disaccharides, polysaccharides.
  • Functions: energy source, structural components.
• Lipids:
  • Fats, oils, phospholipids, steroids.
  • Functions: energy storage, insulation, cell membrane structure, hormones.
• Proteins:
  • Amino acids, polypeptide chains, protein structure (primary, secondary, tertiary, quaternary).
  • Functions: enzymes, structural components, hormones, antibodies.
• Nucleic Acids:
  • DNA and RNA.
  • Nucleotides, structure of DNA (double helix), structure of RNA.
  • Functions: genetic information, protein synthesis.
• Enzymes:
  • Biological catalysts.
  • Active site, enzyme-substrate complex, factors affecting enzyme activity.
  • Cofactors, coenzymes.

Cell Cycle and Cell Division

• Cell cycle: sequence of events by which a cell duplicates its genome, synthesizes other cell constituents, and divides into two daughter cells.
• Phases of Cell Cycle:
  • G1 phase (gap 1): cell growth and metabolism.
  • S phase (synthesis): DNA replication.
  • G2 phase (gap 2): preparation for cell division.
  • M phase (mitosis): cell division.
• Mitosis:
  • Prophase, metaphase, anaphase, telophase.
  • Results in two identical daughter cells.
• Meiosis:
  • Meiosis I: prophase I, metaphase I, anaphase I, telophase I.
  • Meiosis II: prophase II, metaphase II, anaphase II, telophase II.
  • Results in four haploid daughter cells.
  • Crossing over and genetic recombination occur during prophase I.
• Significance of Mitosis and Meiosis:
  • Mitosis: growth and repair.
  • Meiosis: sexual reproduction and genetic variation.