Properties of complex organisms

Types of Life

• Unicellular organisms consist of a single cell performing all life processes (e.g., Amoebas, Bacteria).
• Multicellular organisms are composed of many specialized cells (e.g., Animals, plants, fungi, insects).

Properties of Complex Organisms

• Complex organisms exhibit reception, metabolism, and reproduction, and are highly organized.
• Reception is the ability to sense and respond to internal and external stimuli, which our bodies respond to.
• Specialized cells or organs act as receptors to detect changes in temperature, light, chemicals, pressure, and sound; examples include eyes (photoreceptors), tastebuds (chemoreceptors), and skin (mechanoreceptors and thermoreceptors).
• Homeostasis is the maintenance of stable internal physical and chemical conditions, crucial for optimal functioning.
• Reception is vital for maintaining homeostasis, such as sweating to cool down when feeling too hot.

Metabolism

• Metabolism is the sum of all chemical reactions in an organism, including building up and breaking down substances.
• Cellular respiration (using oxygen), hormone synthesis, waste removal, and medications targeting metabolic pathways exemplify metabolic processes.
• Metabolizing is how materials are used and waste is eliminated through biochemical reactions.
• Anabolism involves building complex molecules from simple ones, requiring energy (e.g., building muscle from amino acids).
• Catabolism involves breaking down complex molecules into simpler ones, releasing energy (e.g., digestion of food).

Reproduction

• Asexual reproduction involves a single organism producing identical offspring (e.g., bacteria dividing, plants forming runners).
• Fission is a type of asexual reproduction where an organism splits into two or more identical copies.
• Budding occurs when a new organism grows as an offshoot of the parent (e.g., hydra, some plants).
• Fragmentation occurs when an organism breaks into pieces, each developing into a new individual (e.g., starfish, worms).
• Sexual reproduction involves two parents contributing genetic material, creating offspring with combined traits (e.g., most animals, including humans).

Advantages of Asexual and Sexual Reproduction

• Both types of reproduction ensure the continuation of a species.
• Asexual reproduction is easier, rapid in favorable conditions, doesn't require a mate, and results in offspring well-adapted to stable environments.
• Sexual reproduction increases genetic diversity, enhancing adaptability and survival, and makes individuals unique.

Organization in Living Organisms

• Living organisms have a hierarchical organization, from cells to complex systems.
• This allows for specialization and division of labor, promoting efficiency and maintaining stability.
• Larger organisms have more cells, a greater surface area to volume ratio, and need more specialized organization.
• The hierarchy of organization includes cells forming tissues, tissues forming organs, and organs forming organ systems.
• Specialization is allowed through this organization.

Abiotic and Biotic Elements

• Abiotic refers to non-living things or those that have never been alive, environmental factors such as air and water quality.
• Biotic refers to living organisms or things that were once living, including the human body and disease-causing organisms.

Matter vs. Life

• Matter is the substance of everything, but not all matter constitutes life.
• A specific organization of matter with reception, metabolism, reproduction, and organization is required for life.
• Distinct vocabulary must be used to describe living and nonliving things with vocabulary such as growth and movement.
• For example, rocks grow through accretion while organisms grow from cell division.
• Rivers move through gravity and land slope while animals use energy to power muscles.

Tissues

• Tissues are groups of similar cells working together for a specific function (e.g., muscle, epithelial, connective, nerve).
• Tissues undergo constant change, renewal, and adaptation.
• Epithelium lacks blood vessels, is tough and resilient on the outside, providing a defense against disease internally while protecting internal organs and acting as barriers.
• Single-layer (simple) and multi-layered (stratified) and shapes such as squamous, cuboidal, and columnar exists
• Epithelium receives nutrients via diffusion. Connective tissues vary in shape and structure by supporting, protecting, and binding tissues.
• Variability exists such as dense tissue forming structures like bones; less dense tissue forming cartilage; and very sparse tissue forming fluid like blood. The denser the tissue, the more opaque.

Blood

• Blood consists of plasma, red blood cells, white blood cells, and platelets.

• Blood transports oxygen and nutrients to the lungs and tissues.

• Muscle tissue typically occurs in bundled, fibrous strands that are protein-based, with ability to expand, contract, and revert back to its original state.

• Skeletal muscles are striated and provide selective contractility throughout the body, whereas smooth muscles are are involuntary, elastic, non-striated, and found in blood vessels and intestines.

• Cardiac unique to the heart, capable of rhythmic contractions that pump blood.

• Nerve tissues the most complex, and cannot be replaced if damaged is non-regenerative; damage is irreversible to the central nervous system.

• The brain is the most complex organ.

• The body is hierarchical; independent tissues work cooperatively to fulfill functions.

Blood Vessels

• Four tissue types comprise blood vessels: blood (connective), smooth muscle (inside the vessel), nerve tissue (inside the vessel), and epithelial tissue (endothelial wall, inside lining).

Organ Systems

• Each system in the human body has a specific function coordinated through its organs.
• Each organ is made of tissues, which are made of cells. There are 11 main systems:
  • The respiratory system (nose, mouth, trachea, lungs, bronchi, diaphragm, alveoli) exchanges gases.
  • The digestive system (mouth, esophagus, stomach, pancreas, gallbladder, liver, intestines, rectum) is catabolic, ingests/digests/absorbs nutrients, and eliminates waste.
  • The circulatory system (heart, veins, arteries, blood) transports oxygen and nutrients throughout the body.
  • The skeletal system (bones, cartilage) supports the body, protects organs, and enables movement.
  • The nervous system (brain, spinal cord, nerves) controls body functions and sends signals using electricity.
  • The integumentary system (skin, accessory structures, glands) covers, protects, and helps control temperature.
  • The excretory system (kidneys, ureters, urinary bladder, urethra, skin) filters waste from blood and maintains water/electrolyte levels.
  • The immune system (lymph, lymph nodes, white blood cells, spleen) destroys/removes microbes and viruses.
  • The muscular system (skeletal, smooth, cardiac) moves and controls the movement of materials.
  • The endocrine system (glands like hypothalamus, thyroid, pituitary gland, pancreas) relays chemical messages essential for physiological processes.
  • The reproductive system (ovaries, oviducts, uterus, testes, seminal vesicles) manufactures cells for reproduction.