Characteristics of Life

What is Biology?

  • Biology is the study of all living things, referred to as organisms.

    • Organisms include:

      • Bacteria

      • Protists

      • Fungi

      • Plants

      • Animals

Common Characteristics of Living Things

  1. Basic Unit is the Cell

  2. Reproduction

  3. Universal Genetic Code (DNA)

  4. Growth & Development

  5. Obtain & Use Materials & Energy

  6. Response to Environment

  7. Maintain Stable Internal Environment (Homeostasis)

  8. Evolve as a Group - Living things change over time.

Characteristics of Organisms

  • All organisms are composed of cells.

Facts About Cells

  • Cells are the smallest living unit of an organism.

  • All cells contain living material called cytoplasm.

  • Surrounded by a cell membrane that controls what enters and leaves the cell.

  • Cells are complex and highly organized.

  • Contain organelles which perform different functions (e.g. chloroplasts in plants synthesize sugars).

Types of Cells

  • Prokaryotes:

    • Simplest cells.

    • Lack a nucleus and membrane-bound organelles.

    • Example: Bacteria.

  • Eukaryotes:

    • More complex cells with a nucleus and membrane-bound organelles.

    • Examples: Plants, animals, protists, fungi.

Organismal Structure

  • Unicellular Organisms: Composed of one cell.

  • Multicellular Organisms: Composed of many specialized cells.

Reproduction in Organisms

  • Organisms reproduce to pass on genetic traits.

  • Two Types of Reproduction:

    • Sexual Reproduction:

      • Involves two parents.

      • Egg fertilized by sperm to produce a zygote.

      • Offspring differ from parents.

    • Asexual Reproduction:

      • Involves a single organism or cell.

      • Cell division leads to identical offspring.

Genetic Code

  • DNA (Deoxyribonucleic acid): Carries genetic code for all organisms.

  • All organisms have DNA that codes for proteins essential for cellular function.

Growth and Development of Organisms

  • Organisms grow by producing more cells and enlarging existing cells.

  • Development occurs as organisms mature into adults.

Food and Energy Requirements

  • Autotrophs: Make their own food.

    • Photoautotrophs: Use sunlight (photosynthesis).

    • Chemoautotrophs: Use chemicals (chemosynthesis).

  • Heterotrophs: Cannot make their own food; they consume other organisms.

    • Cellular Respiration: Process of releasing chemical energy from food.

    • Types of heterotrophs:

      • Herbivores (eat plants)

      • Carnivores (eat meat)

      • Omnivores (eat both plants and animals).

Metabolism

  • Sum of all chemical reactions in an organism (catabolism + anabolism).

  • All metabolic processes require energy, with sunlight being the ultimate energy source for life on Earth.

Response to Stimuli

  • Organisms respond to environmental stimuli (temperature, water, food, etc.) to survive and reproduce.

Homeostasis

  • Maintaining a stable internal environment within the ranges required for life, including conditions like pH, temperature, and water balance.

Evolution of Living Things

  • Groups of organisms, not individuals, evolve over time to adapt to changing environments.

  • Fossil records provide evidence of changes in groups of organisms.

Levels of Biological Organization

  • Levels:

    • Atoms

    • Molecules

    • Organelles

    • Cells – where life begins

    • Tissues

    • Organs

    • Organ Systems

    • Organism

    • Population

    • Community

    • Ecosystem

    • Biosphere