Biological Systems and Organization

Hierarchy of Biological systems

• The organization of life is structured into increasingly complex levels, according to Raven/Berg, Environment, 3/e:
  • Atoms
  • Molecule
  • Cell
  • Tissue
  • Organ
  • Body system
  • Organism
  • Population
  • Community
  • Ecosystem
  • Biosphere

Unicellular vs. Multicellular Organisms

• All living organisms are composed of cells.
• Unicellular Organisms: These consist of a single cell that performs all necessary functions for life. An example includes bacteria.
• Multicellular Organisms: These are composed of many cells working together.
• Specialization in Multicellularity:
  • Complex organisms survive because their cells undergo specialization.
  • Specialized cells perform specific individual functions instead of all functions.
  • These cells must interact and coordinate with all other cells within the organism to maintain life.

Cell Requirements and Functional Challenges

• To function effectively, cells require:
  • Delivery of nutrients and oxygen ($O_2$).
  • Removal of waste products.
  • Regulation of temperature ($temp$) and $pH$ levels.
• Challenges of scale: Delivering these requirements is difficult in large organisms because they are made up of too many cells for direct exchange with the environment to be efficient.

Plant Organization and Classification

• Vascular Plants: These contain specialized vascular tissue consisting of xylem and phloem. Examples include:
  • Angiosperms
  • Gymnosperms
  • Ferns (pterophytes)
• Non-vascular Plants: These do not contain xylem or phloem. They rely on simplified tissues to function. Examples include:
  • Mosses
  • Liverworts

Plant Cell and Tissue Types

• Dermal Tissues:
  • Epidermis: A single layer of cells forming the outside of the plant. It secretes a wax called the cuticle for protection and to reduce water loss.
  • Stomata: Specialized structures found between guard cells (specialized epidermal cells). They facilitate gaseous exchange and transpiration.
• Ground Tissues: These make up the majority of the plant body.
  • Parenchyma: Responsible for photosynthesis and various metabolic functions.
  • Collenchyma: Provides structural support.
  • Sclerenchyma: Provides strength and rigid support.
• Vascular Tissues: These run through the ground tissue in vascular plants.
  • Xylem: Responsible for the transport of water and mineral salts.
  • Phloem: Responsible for the transport of sugars and nutrients.

Plant Organs and Systems

• Vascular Plant Organs:
  • Leaves: The primary site for gaseous exchange and photosynthesis.
  • Flowers: The organs of reproduction.
  • Fruits: Structures that protect seeds and aid in seed dispersal.
  • Stems: Provide support for the leaves and transport materials.
  • Roots: Anchor the plant into the substrate and absorb water.
• The Root System: Located underground, it absorbs water and nutrients from the soil while providing support and structure.
• The Shoot System (Angiosperms):
  • Reproductive sections: Flowers and fruit.
  • Non-reproductive sections: Leaves and stems.

Animal Cellular and Tissue Organization

• Complex animals contain hundreds of different cell types, each specialized for a function.
• Common animal cell types: Skin cells, muscle cells, blood cells, nerve cells, and fat cells.
• The Four Major Animal Tissues:
  • Epithelial Tissue: Comprises external and internal layers of the body; functions include protection, secretion, and absorption.
  • Shapes: Squamous, Cuboidal, Columnar.
  • Arrangements: Simple, Stratified, Pseudostratified.
  • Examples: Simple squamous epithelium, Stratified cuboidal epithelium, Pseudostratified columnar epithelium.
  • Muscle Tissue:
  • Skeletal Muscle: Attached to the skeleton; responsible for voluntary movement.
  • Cardiac Muscle: Heart muscle responsible for pumping blood; involuntary.
  • Smooth Muscle: Found in organs such as the uterus, esophagus, stomach, small intestine, and blood vessels; involuntary.
  • Nervous Tissue: Transmits electrical signals. It is made of neurons and is found in the brain and spinal cord.
  • Structure of a typical neuron: Dendrites, Nucleus, Cell Body, Axon, Axon Terminals, Node of Ranvier, Schwann's Cells, Myelin Sheath.
  • Connective Tissue: Connects and supports other tissues and organs. Examples include blood, bone (osseous tissue), cartilage (hyaline cartilage), adipose (fat), areolar connective tissue, and fibrous connective tissue.

Major Animal Organ Systems

• Digestive System: Breaks down and processes food; eliminates undigested food waste via egestion. (Stomach, liver, pancreas, intestines).
• Excretory System: Removes waste from blood via excretion; assists in water balance control. (Kidneys, bladder, lungs).
• Endocrine System: Production and secretion of hormones to regulate bodily processes. (Hypothalamus, pituitary, thyroid, thymus, adrenal).
• Skeletal System: Provides internal structure and support; works with the muscular system for movement. (Bones, joints, cartilage).
• Muscular System: Responsible for contractions (skeletal, cardiac, and others); enables movement with the skeletal system. (Skeletal muscles, cardiac muscles, tendons).
• Integumentary System: Protects internal structures from the external environment. (Skin, hair, nails, subcutaneous fat).
• Nervous System: Detects and processes sensory information to activate responses.
• Immune System: Defends against infection; includes the lymphatic system for lymph fluid transport.
• Respiratory System: Delivers oxygen to the blood and removes carbon dioxide ($CO_2$) via respiration. (Lungs).
• Blood Circulatory System: Delivers oxygen and nutrients to tissues via blood transport.
• Reproductive System: Coordinates action for reproduction. In males, it regulates sperm and hormone production. In females, it regulates egg production, hormones, ovulation, and offspring nurturing.

Questions and Discussion

• Question 1: Cells are organized into tissues, organs, and systems to:

  • A) perform functions that cannot be carried out by single cells.
  • B) allow for cells to exchange oxygen and carbon dioxide directly between one another.
  • [Answer: A]

• Question 2: The two organ systems of vascular plants are:

  • A) stem and leaf systems.
  • B) root and shoot systems.
  • [Answer: B]

• Question 3 (Matching Plant Organs):

  • Flowers: undergo fertilization in the presence of pollen to produce seeds.
  • Leaves: site of photosynthesis.
  • Stems: provide support and also stores and transports nutrients and water.
  • Roots: absorb water and nutrients from ground soil.
  • Fruit: protects developing seeds and aids seed dispersal.

• Question 4 (Fill in the blanks):

  • Epithelial tissue consists of tightly packed cells that line the internal and external surfaces of an organism.
  • Skeletal, cardiac, and smooth are all types of muscle tissue.
  • Neurons are the cells found in nervous tissue.
  • Connective tissue connects the different tissue types and structures of the body.

• Question 5: Which are major systems of the human body? (Select all that apply):

  • I: integumentary system (Yes)
  • II: reproductive system (Yes)
  • III: intestinal system (No - part of digestive)
  • IV: nervous system (Yes)
  • V: brain system (No - part of nervous)

• Question 6 (Matching Animal Systems):

  • Immune system: protects the body against infection.
  • Excretory system: removes waste substances from the body.
  • Endocrine system: produces and secretes hormones around the body.
  • Respiratory system: delivers oxygen to the blood and removes carbon dioxide from the body.
  • Blood circulatory system: delivers oxygen and nutrients to body tissues.

• Question 7 (Fill in the blanks):

  • The digestive system is responsible for breaking down foods and absorbing their nutrients. Animals often consume fruit, a plant organ that contains seeds. Plants have roots that absorb water from the soil, and along with stems provide support to the plant, helping it stand upright. Similarly, animals such as humans contain a skeletal system that works in tandem with the muscular system to provide support and enable movement.