Biology Classification of Living Organisms

Classification of Living Organisms

• Organisms are categorized into unicellular and multicellular types.
• Unicellular organisms consist of a single cell, examples are Bacteria, Viruses, Amoeba, Paramecium, and Yeast.
• Multicellular organisms are composed of multiple cells.
• Multicellular organisms are further divided into prokaryotic and eukaryotic cells.
• Prokaryotic cells lack a nucleus and membrane-bound organelles, an example is Bacteria.
• Eukaryotic cells have a nucleus and membrane-bound organelles, further divided into animal and plant cells.

Cellular Structure

• Cytoplasm is a jelly-like substance inside the cell.
• Cytoskeleton provides structural support and aids in the movement within the cell.
• Plasma membrane is a semi-permeable barrier that separates the cell's interior from its surroundings.
• Endoplasmic reticulum is a network of membranes involved in protein synthesis and transport.
• Golgi apparatus processes and packages proteins.
• Mitochondria are the powerhouses of the cell and are responsible for energy production.
• Ribosomes synthesize proteins.
• Lysosomes are involved in intracellular digestion.
• Peroxisomes break down fatty acids and other molecules.
• Nucleus contains the cell's genetic material (DNA).
• Centrioles are involved in cell division.

Cell Division: Mitosis and Meiosis

• Mitosis creates identical diploid cells for growth and repair.
• The starting cell for mitosis is diploid (2n).
• Mitosis involves Interphase, Prophase, Metaphase, Anaphase, and Telophase.
• Meiosis creates haploid gametes (sex cells) for sexual reproduction.
• The starting cell for meiosis is diploid (2n).
• Meiosis involves two rounds of division.
• Meiosis I includes Interphase, Prophase I, Metaphase I, Anaphase I, and Telophase I.
• Meiosis II includes Prophase II, Metaphase II, Anaphase II, and Telophase II.
• The result of meiosis is four haploid (n) cells.

Prokaryotic and Eukaryotic Cells

• Eukaryotic Cells:
  • Contain a nucleus, mitochondria, golgi apparatus, endoplasmic reticulum (ER), lysosomes, peroxisomes, and ribosomes.
• Prokaryotic Cells:
  • Classified based on the thickness of the cell wall and shape.
  • Contain a capsule, cell membrane, ribosomes, DNA or RNA, and flagella.

Symbiotic Associations and Pathogens

• Symbiotic associations are close relationships between two organisms where both benefit.
• Some microorganisms can cause disease, these are called pathogens.

Chloroplasts

• Chloroplasts are organelles found only in plant cells.

Questions regarding Bacteria, Cytology, and Viruses

• Question 1: Are All Bacteria Harmful?
  • Answer: No, there are beneficial bacteria, like Archea.
• Question 2: Cytology vs.Histology
  • Answer: Cytology examines cells, while histology examines tissues.
• Question 3: Can Viruses Survive Independently?
  • Answer: No, viruses cannot survive independently.