VCE Biology Notes: Functioning Systems

U1AOS2 Functioning Systems

Key Concepts

Specialization and organization of plant cells into tissues for specific functions in vascular plants, including intake, movement, and loss of water.
Specialization and organization of animal cells into tissues, organs, and systems with specific functions: digestive, endocrine, and excretory.

Unicellular vs. Multicellular Organisms

Feature	Unicellular Organisms	Multicellular Organisms
Cell Number	Single cell	Many specialized cells
Life Processes	Perform all life processes in one cell	Cells work together to perform life functions
Reproduction	Mostly asexual (e.g., binary fission)	Mostly sexual (some asexual)
Examples	Bacteria, Amoeba, Paramecium	Humans, Plants, Fungi

Multicellularity Requirements

For an organism to be considered truly multicellular:

Its cells (except reproductive cells) must have the same DNA.
Its cells must be connected and must communicate and cooperate to function as a single organism.
It must have different cells that are specialized and responsible for specific functions (one of which must be reproduction).
Its cells must be dependent on each other for survival.

Advantages of Multicellularity

Energy efficiency through specialization of cells
Longer lifespan due to division of labor and efficiency
Genetic diversity from sexual reproduction enhances adaptability
Better resilience to environmental changes and cell damage
Larger size possible, allowing more complex body structures
Greater mobility due to specialized limbs
Complex responses to external stimuli enabled by organized systems

Disadvantages of Multicellularity

Higher energy demands to maintain many cells
Cell dependence—individual cells can't survive on their own
Reproductive complexity, often requiring mates or partners
Slower evolution due to longer generation times

Levels of Organization

Cell: Basic unit of life
Tissue: Group of similar, specialized cells working together to perform a specific function
Organ: Two or more tissues that work together to carry out specialized tasks
System: Group of organs working together to perform vital functions
Organism: A complete living being capable of carrying out all life processes

Vascular vs. Non-Vascular Plants

Vascular Plants: (90%) have a transport system.
Non-vascular Plants: (10%) do not have a transport system; they use osmosis and diffusion to move substances from cell to cell, must be small and in moist environments, and don’t have roots.

Vascular Plants

A plant that has tissue for conducting water and minerals throughout the plant.

Xylem vessels
Phloem vessels

Plant Systems

Plants have two main systems:

The root system
The shoot system

Plant Systems Details

Roots: Usually underground, absorb water and nutrients from the soil, and provide support and structure.
Shoots: Above ground, responsible for gas exchange and photosynthesis.

Plant Organs

Organ	Function
Leaves	Sites of gas exchange and responsible for photosynthesis. Organized to increase sunlight exposure.
Flowers	The sexual reproductive organs of flowering plants (angiosperms). Following fertilization of male and female gametes (contained in pollen), seeds develop, and the ovary of a flower grows into a fruit.
Fruits	Grown from a flower post-fertilization. Protect seeds and are often specialized to attract animals that aid with seed dispersal.
Stems	Support the leaves, flowers, and fruits, as well as transport water and nutrients between the roots and shoots.
Roots	Absorption and storage of water and nutrients from the soil. Responsible for anchoring the plant to the ground and providing structural support.

Plant Anatomy

Flower
Leaf
Stalk
Apical Bud
Stem
Soil
Fruit

Meristematic Tissue

A group of undifferentiated cells.
Found at the root tips and shoot tips of plants.
Cells are constantly dividing (mitosis) to produce new cells (growing).

Vascular Tissue

Classifies vascular plants.
Continuous closed pathways around the plant.
Arranged in vascular bundles, which help give plants structure and transport nutrients.
Grouped into 2 main types:
- Xylem
- Phloem

Xylem Tissue

Tubes that transport water and minerals such as potassium, nitrogen, and phosphorus in one direction from the roots to the leaves of a plant.
Dead tissue; the nucleus and mitochondria disintegrate.

Phloem Tissue

Tubes that transport sugars and other nutrients around a plant in both directions.
Living tissue made of living cells.

Xylem vs. Phloem

Feature	Phloem	Xylem
Function	Transportation of food and nutrients from leaves to storage organs and growing parts of the plant.	Water and dissolved mineral transport from roots to aerial parts of the plant.
Structure	Tubular with soft-walled cells	Tubular with hard-walled cells
Location	Roots, stems, and leaves	Roots, stems, and leaves
Additional Functions	Forms vascular bundles with xylem	Forms vascular bundles with phloem and gives mechanical strength to the plant due to the presence of lignified cells.
Nature of Tissue	Living tissue	Non-living tissue at maturity
Movement	Bidirectional	Unidirectional (up the plant’s stem)

Dermal Tissue

Forms outer layer (“skin”) of the plant.
Also called epidermal tissue.
Main Function: Protection.
Secondary Function:
- Root hairs are extensions of root epidermis (absorb water).
- Epidermis of leaves and stems have a waxy cuticle (prevent water loss).

Ground Tissue

Makes up the majority of plant tissue.
Carries out a range of functions:
- Photosynthesis
- Storage of food
- Storage of waste

Plant Tissues Summary

Vascular Tissue
- Xylem
- Phloem
Ground Tissue
Dermal Tissue (Epidermis)

Plant Cells

Cell Type	Function
Parenchyma cells	The major cells of plants, responsible for photosynthesis and other metabolic activity.
Sclerenchyma cells	Provide support to the plant.
Collenchyma cells	Provide support to the plant.
Xylem cells	Cells of the xylem are responsible for the transport of water and minerals from the roots to the leaves of the plant.
Phloem cells	Cells of the phloem are responsible for the transport of sugars and other nutrients throughout the plant.