Integrated Science Chapter 1: Introduction to Science and Living Systems

Introduction to Life and the Seven Characteristics of Living Things

• The Scope of Biology: Biology is defined as the study of living things. This include all animals and plants. While some organisms are obviously living due to visible actions (e.g., a cat playing with a ball or a pigeon flying), others, such as plants, require closer observation as they do not perform these specific actions.

• Criteria for Life: For an entity to be classified as living, it must display all seven characteristics of living things simultaneously.

• Ambiguous Non-Living Things: Some non-living objects may exhibit one or two biological characteristics, but not all seven.

  • Movement: Machines like washing machines move.

  • Feeding/Fueling: Cars require petrol (feeding) to operate and move.

  • Growth: Ice crystals forming on a window can grow in size if environmental conditions are favorable.

• Classification of Non-Living Things: Non-living matter, such as sand, wood, and glass, is divided into two distinct categories:

  1. Never Living: Substances that were never part of a biological organism, such as stones and gold.

  2. Once Living: Substances derived from organisms that were once alive.

     • Coal: Formed millions of years ago when trees died and sank into soft ground when the Earth was heavily forested.

     • Paper: Manufactured from trees.

     • Jam: Produced from the fruit of plants.

Detailed Breakdown of the Seven Characteristics of Living Things

• Feeding (Nutrition): All living organisms must take in substances from their environment. This is necessary to obtain energy, facilitate growth, and maintain overall health.

• Movement:

  • Internal Movement: All living things have the capacity to move substances from one part of the body to another.

  • External Movement (Locomotion): Many organisms can move from one location to another via methods such as walking, flying, or swimming.

• Breathing or Respiration: This involves the exchange of gases with the environment. In animals, this typically involves taking in oxygen and breathing out carbon dioxide.

• Excretion: The process of removing waste products from the body. If these wastes remain, they can become poisonous.

  • Human Examples: Humans produce urine (liquid waste) and excrete waste gases during respiration.

• Growth: Organisms utilize energy gained from feeding to become larger and more complex over time.

• Sensitivity: The ability to react to environmental changes. Common stimuli include touch, light, heat, cold, and sound.

• Reproduction: The production of offspring to ensure the continuation of the species.

  • Humans: Produce babies.

  • Cats: Produce kittens.

  • Pigeons: Lay eggs.

  • Plants: Produce seeds that germinate and grow into new individual plants.

Unicellular Organisms (Micro-organisms)

• General Characteristics: Unicellular organisms consist of a single cell that performs all life processes required by multicellular organisms. They are generally invisible to the naked eye and require a microscope for observation. Even in colonies (e.g., bacteria), each individual cell remains a complete living unit.

• Examples: Bacteria, various protists, and certain fungi.

• Nutrition in Unicellular Organisms:

  • Most aquatic unicellular organisms must move to find food, often consuming other organisms.

  • Plant-like Protists and Bacteria: Capable of producing their own food through the process of photosynthesis.

  • Fungi and Bacteria: May interact with one another to secure nutrients.

• Case Study: Paramecia:

  • Found in aquatic environments.

  • Feeds on bacteria and algae.

  • Mechanism: Covered in cilia that beat in unison to create water currents, pulling the organism toward food.

  • Ingestion: An oral groove uses cilia to draw food into a cavity, which then forms a food vacuole.

  • Digestion: Nutrients diffuse across the vacuole membrane into the cytoplasm. Waste is expelled through an anal pore.

• Case Study: Amoeba:

  • An animal-like protist that uses phagocytosis to feed.

  • Mechanism: It extends pseudopods (false feet) to surround food material, creating a food vacuole.

  • Digestion: Chemicals are released into the vacuole to break down food; particles then diffuse into the cytoplasm.

Movement, Locomotion, and Gas Exchange

• Movement vs. Locomotion:

  • Movement: Refers to a change in the form or shape of the organism. This is achieved via pseudopods. In multicellular organisms, white blood cells use pseudopods to engulf invaders via phagocytosis.

  • Locomotion: Refers to a change in the organism's physical position. This is achieved using cilia or flagella to create currents in watery environments.

• Respiration and Gas Exchange:

  • Most organisms require oxygen to release energy from food, producing carbon dioxide as a byproduct.

  • Diffusion: In unicellular organisms, oxygen diffuses into the cell, and carbon dioxide diffuses out once internal concentrations exceed external levels.

  • Anaerobic Life: Some microbes (certain bacteria and fungi) survive without oxygen. Yeast is a primary example of a unicellular fungus capable of surviving without oxygen.

• Sensing the Environment:

  • Unicellular organisms lack complex sensory organs (eyes, ears) but use other methods.

  • Chemical Detection: Some bacteria detect substances like sugar and move toward them.

  • Light Detection: Photosynthetic protists like Euglena utilize special sensors to detect light.

Multicellular Organisms and Cell Specialization

• Scale and Complexity: Multicellular organisms consist of many specialized cells.

  • Example: The Douglas fir tree can reach heights of $76\,m$ and diameters of nearly $3\,m$.

• The Process of Development:

  • All multicellular organisms begin as a single cell.

  • As cells divide, they remain close together, and the total number of cells determines the organism's size.

• Cellular Differentiation: This is the process where cells undergo changes to develop unique characteristics and specific functions early in development.

• Specialization: Groups of cells specialize to perform one task efficiently, rather than every cell performing every job.

  • Community Analogy: Similar to a city where a mechanic repairs cars and a doctor treats the sick, specialized cells ensure the organism is more efficient.

  • Biological Examples: The heart is specialized for pumping blood but cannot digest food.

• Specific Examples of Specialization:

  • Hydra: Possesses specialized tentacles for catching food and different cells for digestion.

  • Goose: Features wings for flight and webbed feet for swimming.

  • Muscle Cells: Specialized, differentiated cells that contract to facilitate movement.

  • Other Differentiated Cells: Skin cells, fat cells, and nerve cells.

Organic and Inorganic Compounds

• Defining Organic in Chemistry: In a chemical context, "organic" refers to compounds containing carbon. This differs from the agricultural use of the word.

• Core Differences:

  • Organic Compounds: Always contain Carbon ($C$). Nearly all contain Carbon-Hydrogen bonds ($C-H$).

  • Inorganic Compounds: Most do not contain carbon. Those that do typically lack $C-H$ bonds.

• Examples of Organic Compounds:

  • Nucleic acids (DNA)

  • Fats

  • Sugars: Table sugar or sucrose ($C_{12}H_{22}O_{11}$)

  • Proteins and Enzymes

  • Hydrocarbon fuels

  • Benzene ($C_6H_6$)

  • Methane ($CH_4$)

  • Ethanol (grain alcohol) ($C_2H_6O$)

• Examples of Inorganic Compounds:

  • Table salt or sodium chloride ($NaCl$)

  • Carbon dioxide ($CO_2$)

  • Diamond (pure carbon)

  • Silver

  • Sulfur

• Exceptions (Organic Compounds without C-H bonds):

  • Carbon tetrachloride ($CCl_4$)

  • Urea ($CO(NH_2)_2$)

• Organic Compounds and Life: While most organic compounds are produced by living things, they can form through other processes. On Pluto, solar radiation provides the energy required to create organic compounds from inorganic carbon precursors, which does not necessarily imply the presence of life.