Preliminary Biology Modules 1–4

Cell Theory

Principle stating that all living things are made of cells, cells are the basic units of structure and function, and all cells arise from pre-existing cells.

Subcellular Components

Structures within a cell, such as organelles, that are not considered alive by themselves.

Prokaryote

A simple, nucleus-lacking cell type (Archaea or Bacteria) with no membrane-bound organelles and division by binary fission.

Eukaryote

Complex cell type (plants, fungi, protists, animals) possessing a nucleus, membrane-bound organelles, and division by mitosis.

Binary Fission

Asexual reproductive process in prokaryotes where one cell divides into two genetically identical cells.

Nucleoid

Region in a prokaryotic cell where the large loop of DNA is located.

Mitosis

Eukaryotic cell division producing two genetically identical daughter cells for growth or repair.

Cytoplasm

Semi-fluid cell interior containing dissolved substances and organelles; supports shape and protects components.

Nuclear Membrane

Double membrane with pores that separates the nucleus from the cytoplasm and regulates molecular passage.

Nucleus

Organelle that stores DNA, coordinates growth and reproduction, and produces ribosomes.

Ribosome

Organelle composed of RNA and protein that assembles amino acids into proteins; free in cytoplasm or bound to rough ER.

Chloroplast

Plant organelle where photosynthesis occurs; contains green pigment chlorophyll.

Golgi Apparatus

Stacked membranes that sort, modify and package proteins for secretion or use within the cell.

Lysosome

Membrane-bound vesicle containing digestive enzymes that break down waste and cellular debris.

Mitochondria

‘Powerhouse’ organelle that produces ATP, supplying about 90 % of cellular energy (used by plants mainly at night).

Cytoskeleton

Network of microfilaments and microtubules that supports cell shape and enables movement.

Centriole

Paired organelles in animal cells that organise the mitotic spindle during cell division.

Cell Wall

Rigid outer layer in plants providing structure, support and protection outside the cell membrane.

Cell (Plasma) Membrane

Flexible, selectively permeable phospholipid bilayer that encloses the cell and regulates transport of substances.

Fluid Mosaic Model

Description of cell membrane as a dynamic phospholipid bilayer with embedded proteins, cholesterol and carbohydrates.

Membrane Proteins

Proteins that perform various functions in the cell membrane, including transport, reception, and recognition, and adhesion.

Rough Endoplasmic Reticulum

ER studded with ribosomes; folds, modifies and dispatches proteins.

Smooth Endoplasmic Reticulum

ER without ribosomes; synthesises lipids, steroids, detoxifies chemicals and stores calcium.

Vacuole

Membrane sac, large in plant cells, for storage of water, solutes and waste; helps maintain turgor pressure.

Light Microscope

Optical instrument using visible light and glass lenses to magnify specimens up to ∼1500× (400× in school labs). Can be used to view living specimens.

Transmission Electron Microscope (TEM)

Electron microscope where electrons pass through thin specimens to create high-resolution 2-D images (up to 1.5 million×). Only dead specimens can be viewed.

Scanning Electron Microscope (SEM)

Electron microscope that scans a surface with electrons to produce detailed 3-D images, resolution ∼10 nm. Only dead specimens can be viewed.

Fluorescent Microscope

Microscope that excites fluorescently labelled samples with intense light to produce bright, often 3-D images.

Diffusion

Passive movement of molecules from a region of higher to lower concentration until equilibrium is reached.

Simple Diffusion

Direct diffusion of small or lipid-soluble molecules across a semipermeable membrane without proteins.

Facilitated Diffusion

Passive transport of specific solutes across a membrane via carrier or channel proteins.

Osmosis

Diffusion of water across a selectively permeable membrane from low solute concentration to high solute concentration, facilitated by specialised protein channels called aquaporins, which increase water permeability.

Isotonic Solution

External solution with equal solute concentration to the cell; water moves in and out at equal rates.

Hypotonic Solution

External solution with lower solute concentration than the cell; water enters and the cell swells.

Hypertonic Solution

External solution with higher solute concentration than the cell; water exits and the cell shrinks.

Endocytosis

Active process where the cell membrane engulfs material to form a vesicle that brings substances inside.

Exocytosis

Active process where vesicles fuse with the plasma membrane to release contents outside the cell.

Surface Area–to-Volume Ratio

Measure comparing external area to internal volume; higher ratios improve exchange of materials with environment.

Enzyme

Biological catalyst (globular protein) that speeds up reactions by lowering activation energy and is reusable.

Active Site

Specific region on an enzyme where a substrate binds and reaction occurs.

Substrate

Reactant molecule upon which an enzyme acts.

Lock and Key Model

Model where the enzyme acts as the lock and the substrate acts as the key.

Induced Fit Model

Theory that enzyme changes shape slightly to fit substrate precisely, facilitating catalysis.

Carbohydrate

Organic molecule of C, H and O; serves as energy source, storage or structural component (e.g., cellulose).

Lipid

Hydrophobic organic molecule used for energy storage, membrane structure and hormone production.

Protein

Polymer of amino acids with structural, enzymatic, transport and regulatory roles in cells.

DNA

Deoxyribonucleic acid; hereditary molecule carrying genetic information that controls cell activities.

RNA

Ribonucleic acid; nucleic acid that assists in protein synthesis (mRNA, tRNA, rRNA).

Photosynthesis

Process where chloroplasts convert carbon dioxide and water into glucose and oxygen using light energy.

Cellular Respiration

Process where mitochondria break down glucose to generate energy (ATP), transforming glucose and oxygen into carbon dioxide, water, and energy.

Aerobic Respiration

Oxygen-requiring breakdown of glucose to carbon dioxide, water and ATP via many enzyme-catalysed steps.

Anaerobic Respiration

Energy-releasing process that occurs without oxygen, e.g., alcohol fermentation in yeast.

Unicellular Organism

Living organism composed of a single cell that performs all life processes.

Colonial Organism

Group of identical or similar cells living together that can often survive independently.

Multicellular Organism

Organism made of many specialised, interdependent eukaryotic cells performing collective life processes.

Stem Cell

Undifferentiated cell capable of self-renewal and differentiation into specialised cell types.

Embryonic Stem Cell

Pluripotent stem cell from early embryo able to become nearly any cell type.

Adult Stem Cell

Multipotent stem cell in mature tissues that replenishes dying cells and repairs damage.

Differentiation

Process by which unspecialised cells become specialised in structure and function.

Epithelial Tissue

Animal tissue forming protective coverings and linings of body surfaces and cavities.

Connective Tissue

Animal tissue that supports, binds and protects other tissues and organs (e.g., bone, blood).

Nervous Tissue

Animal tissue specialised for communication via electrical impulses (neurons and supporting glia).

Muscle Tissue

Animal tissue capable of contraction; includes skeletal, cardiac and smooth types.

Meristematic Tissue

Plant tissue of actively dividing cells in roots and shoots responsible for growth.

Dermal Tissue

Outer protective plant tissue that waterproofs, guards and controls gas exchange.

Vascular Tissue

Plant transport tissue consisting of xylem and phloem.

Ground Tissue

Plant tissue filling spaces between dermal and vascular tissues; functions in storage, support and photosynthesis.

Autotroph

Organism that produces its own organic compounds from inorganic substances.

Photoautotroph

Autotroph that uses light energy for carbon fixation (e.g., green plants).

Chemoautotroph

Autotroph that derives energy from chemical reactions with inorganic molecules.

Heterotroph

Organism that obtains organic nutrients by consuming other organisms.

Xylem

Plant vascular tissue that transports water and minerals upward from roots and provides structural support. Contains no living cell contents.

Phloem

Plant vascular tissue of sieve tubes and companion cells that transports sugars and other products of photosynthesis through translocation. Contains living cell contents.

Root Hair Cell

Elongated epidermal cell increasing root surface area for water and mineral absorption.

Stomata

Pores in leaf epidermis flanked by guard cells, regulating gas exchange and water loss.

Lenticel

Porous tissue in bark allowing gas exchange between internal tissues and atmosphere.

Cuticle (plant)

Waxy outer layer of leaves and young stems that reduces water loss and protects against environmental stresses.

Open Circulatory System

System where hemolymph is not always confined to vessels and bathes organs directly within a hemocoel.

Closed Circulatory System

System where blood remains inside vessels at all times and is pumped under pressure by a heart.

Artery

Thick-walled, elastic vessel carrying oxygenated blood away from the heart (except pulmonary artery).

Vein

Thinner-walled vessel carrying deoxygenated blood toward the heart and containing valves to prevent backflow.

Capillary

Microscopic blood vessel with a single-cell wall allowing exchange of substances between blood and tissues.

Red Blood Cell

Erythrocyte; biconcave, nucleus-lacking cell containing haemoglobin for oxygen transport.

White Blood Cell

Leukocyte; immune cell involved in body defence, larger and nucleated.

Platelet

Thrombocyte; cell fragment that initiates blood clotting by releasing thromboplastin.

Plasma

Liquid component of blood (∼90 % water) that transports cells, proteins, nutrients, gases, wastes and hormones.

Ecosystem

Community of living organisms interacting with each other and their physical environment.

Abiotic Factor

Non-living physical or chemical element of an ecosystem (e.g., temperature, water, soil).

Biotic Factor

Living component of an ecosystem affecting other organisms (e.g., competition, predation).

Selection Pressure

Environmental factor that influences reproductive success and drives natural selection.

Abundance

Number of individuals of a species in a given area.

Distribution

Geographic area where a species is found.

Transect

Line or narrow strip across a habitat used to record organism distribution.

Quadrat

Square frame used to sample and estimate abundance of slow-moving or stationary organisms.

Structural Adaptation

Physical feature of an organism that enhances survival (e.g., waxy eucalyptus leaves).

Physiological Adaptation

Internal functional adjustment enhancing survival (e.g., penguin fat metabolism for insulation).

Behavioral Adaptation

Action or habit that improves survival (e.g., pufferfish inflating to deter predators).

Natural Selection

Process where individuals with favourable heritable traits survive and reproduce more successfully.

Convergent Evolution

Independent evolution of similar traits in distantly related species due to similar selection pressures.

Divergent Evolution

Accumulation of differences from a common ancestor leading to new species adapted to varied environments.