Characteristics of Life: Nutrition, Photosynthesis, Respiration

Features of Living Things

• Nutrition: Processes by which living things obtain matter and energy.
  • Autotrophs: Organisms that transform inorganic matter into organic matter, such as plants and bacteria. Two types of autotrophic nutrition exist:
    • Photosynthesis (using light)
    • Chemosynthesis (using chemicals)
  • Heterotrophs: Organisms that obtain matter from organic compounds, such as animals and fungi. Two types of heterotrophic nutrition exist, depending on the:
    • Presence of oxygen: Cellular respiration (aerobic)
    • Absence of oxygen: Fermentation (anaerobic)
• Interaction: The capacity of living beings to interact with their environment.
• Reproduction: The process by which living beings produce descendants, leading to the perpetuation of life.
  • Asexual: Descendants arise from a single parent and are genetically identical to each other and their progenitor.
  • Sexual: Descendants arise from the union of reproductive cells (gametes) from two individuals.

Photosynthesis

The process by which organisms extract energy from the sun to transform atmospheric carbon dioxide (CO2), minerals, and water into glucose, releasing energy and oxygen as waste products.

CO2 + H2O --- Sunlight ---> Glucose + O2 + Energy

• Cyanobacteria: Prokaryotic cells.
• Algae and Plants: Eukaryotic plant cells.

Photosynthesis occurs in chloroplasts.

It plays an important role in the evolution of Earth's atmosphere.

Carbon dioxide, incorporated into glucose, can be used by other living beings.

Chemosynthesis

Organisms that perform chemosynthesis inhabit the soil, where sunlight does not reach, such as the seabed.

Cellular Respiration

A set of chemical reactions designed to convert glucose into CO2 and water using oxygen, releasing energy.

Glucose + O2 ---> CO2 + H2O + Energy (Aerobic Respiration)

Fermentations

• Alcoholic Fermentation: Used in the production of wine, beer, and bread.
• Lactic Fermentation: Converts milk into lactic acid.
• Acetic Fermentation: Transforms ethanol from alcoholic fermentation into vinegar.

Functions of Interaction

• Responses that cause movements are called taxis:
  • Phototaxis or phototropism: Reaction to light (negative in roots, positive in stems).
  • Geotaxis or geotropism: Response to gravity (positive geotaxis in roots, negative geotaxis in stems).
  • Thermotaxis or thermotropism: Reaction to temperature (e.g., sperm in the fallopian tube).
  • Chemotaxis or chemotropism: Response to a chemical substance (e.g., plant roots growing towards water).
• Passive Response: Latency

Receptors and Sense Organs

Multicellular organisms:

• Mechanoreceptors: Detect pressure.
• Chemoreceptors: Perceive chemical substances.
• Photoreceptors: Detect changes in light.
• Thermoreceptors: Perceive temperature differences.
• Pain Receptors: Located throughout the body.
• Magnetoreceptors: Detect variations in magnetic fields (e.g., in birds).

Special Senses:

• Sight: Photoreceptors in the cones (detect color) and rods (detect different light intensities) of the eyes.
• Touch: Mechanoreceptors, thermoreceptors, and pain receptors in the skin.
• Taste: Chemoreceptors located on the tongue detect flavors.
• Hearing: Detect sound waves from the environment. Sound receptors.
• Smell: Chemoreceptors in the nose detect gaseous substances.