Rich Variety of Life: Millions of plants and animals have been identified and described. A large number of organisms remain unknown. Organisms vary in size, color, habitat, physiology, and morphology. Need for Classification: The diversity of organisms necessitates defining characteristics for study. Biologists have established rules and principles for:...
Historical Perspective on Classification Primitive Classification: Early classification was instinctive and based on utility (food, shelter, clothing). Lacked scientific criteria. Aristotle’s Contribution: Used morphological characters for classification: Plants: Trees, shrubs, and herbs. Animals: Those with red blood and those without. Two-Kingdom System: Introduced by Linnaeus. Divided organisms into: Plantae:...
Kingdom Monera Bacteria: Sole members of Kingdom Monera. Most abundant microorganisms on Earth. Ubiquitous (found almost everywhere): Soil Extreme habitats (hot springs, deserts, snow, deep oceans) On/in other organisms as parasites Bacterial Shapes: Coccus (cocci): Spherical Bacillus (bacilli): Rod-shaped Vibrium (vibrio): Comma-shaped Spirillum (spirilla): Spiral Characteristics: Simple structure, but...
Archaebacteria:Â A unique group of bacteria adapted to survive in extreme environments. Key Characteristics: Extremophiles:Â Thrive in harsh conditions where most other life forms cannot survive. Distinct Cell Wall:Â Different cell wall structure compared to other bacteria, enabling their survival in extreme environments. Types of Archaebacteria: Halophiles:Â Live in extremely salty environments (e.g.,...
Overview: Metaphase is the second stage of mitosis, beginning with the disintegration of the nuclear envelope. By this stage, the condensation of chromosomes is complete, and they are fully visible under a microscope. This stage is where the morphology of chromosomes is most easily studied. Key Events in Metaphase:...
Overview: Anaphase is the stage in mitosis where the sister chromatids (now called daughter chromosomes) separate and begin moving toward opposite poles of the cell. Key Events in Anaphase: Separation of Chromatids: At the onset of anaphase, the centromeres of each chromosome split, and the sister chromatids separate. The...
Living vs. Non-living: The presence of cells is what differentiates living organisms from non-living things. Cells: The basic unit of life, responsible for structure and function in all living organisms. Unicellular organisms: Made up of a single cell. Examples: Bacteria, Amoeba Capable of independent existence. Carry out all essential...
Overview: Telophase is the concluding stage of nuclear division (karyokinesis) in mitosis. It involves the reorganization and restoration of the nuclear structures at each pole of the cell. Key Events in Telophase: Chromosome Decondensation: Chromosomes that have reached their respective poles decondense and lose their distinct structure. Chromatin material...
Comprehensive Notes on Cell Theory Key Contributions to Cell Theory Matthias Schleiden (1838): German botanist. Studied plants and observed that all plants are composed of different types of cells forming tissues. Theodore Schwann (1839): British zoologist. Studied animal cells and identified the presence of a thin outer layer, now...
Overview: Cytokinesis is the process of cytoplasmic division that follows karyokinesis (nuclear division) to form two daughter cells. It completes the process of cell division by segregating the cytoplasm into two distinct cells. Key Features of Cytokinesis: In Animal Cells: Mechanism: Achieved through the formation of a furrow in...