Organisation of Living Things

Comprehensive vocabulary flashcards covering the organisation of cells, hierarchical structures, plant and animal nutrient/gas requirements, and transport systems based on biology lecture notes.

Unicellular Organisms

Organisms consisting of only one cell that is responsible for all functions necessary to sustain life, usually having a high $SA:V$ ratio.

Colonial Organisms

Groups of individual organisms that live collectively in a cooperative manner but can often survive on their own.

Obligate colony

A type of colony where individual members cannot survive on their own.

Facultative colony

A type of colony where individual members are able to survive independently.

Multicellular Organisms

Complex organisms consisting of many differentiated cell types specialized for particular functions and organized into tissues, organs, and systems.

Differentiation

The process by which a less specialised cell changes to become a specialised type of cell.

Specialisation

The specific function of a cell, which is determined by its physiology and cellular structures.

Embryonic stem cells

Undifferentiated cells in an embryo that can become any cell type and develop systems or create tissue.

Organelles

Subunits of a cell that perform specific metabolic functions, such as the nucleus, ribosome, mitochondria, and chloroplast.

Tissues

A group of specialised cells working together to perform a specific function, such as muscle, nervous, or xylem tissue.

Organs

Groups of tissues arranged to perform large-scale functions, such as the heart in animals or the leaf in plants.

Organ Systems

A group of organs working together to perform a specific function, such as the circulatory or digestive systems.

Vascular plants

Plants that possess specialized vascular tissue (xylem and phloem) for the transport of substances throughout the organism.

Root system

The typically underground part of a plant consisting of tap roots, lateral roots, and root hairs, responsible for absorption, anchorage, and storage.

Tap root

A primary root that grows straight downwards, giving rise to lateral roots and often serving to store food.

Apical meristem

Plant tissue that undergoes rapid mitosis to produce new cells and growth, typically found in roots, tips, and shoots.

Xylem

Vascular tissue composed of dead, hollow, lignin-reinforced cells that transport water and minerals from the roots to the leaves.

Phloem

Living vascular tissue that transports glucose and other sugars from the leaves to the rest of the plant.

Cuticle

A waxy, waterproof layer secreted by the leaf epidermis to prevent water loss.

Palisade mesophyll

Densely packed, elongated photosynthetic cells located towards the top of a leaf to maximise light exposure.

Spongy mesophyll

Loosely packed photosynthetic cells with air spaces, located between the palisade cells and lower epidermis to allow gas diffusion.

Stomata

Small pores in the plant epidermis, surrounded by guard cells, that serve as the site for gaseous exchange.

Lenticels

Raised circular or elongated structures on woody stems or fruit skins that allow for the uptake of oxygen and release of carbon dioxide.

Breathing

The mechanical, often involuntary, process of ventilating gas exchange surfaces at the organ level.

Respiration

The biochemical process occurring at the cellular level involving the exchange of gases during cellular metabolism.

Alveoli

Microscopic air sacs in mammalian lungs with thin, moist walls that provide a large surface area for gas exchange with capillaries.

Avian parabronchi

The gas exchange organ in birds that uses tiny air capillaries and counter-current blood flow to maximize oxygen intake.

Tracheae and Tracheoles

A system of air-filled tubes in insects that open to the atmosphere via spiracles to exchange gases directly with tissues.

Epiglottis

A flap of tissue that covers the trachea during eating or drinking to prevent food from entering the respiratory tract.

Diaphragm

A large, dome-shaped muscle below the lungs that contracts to create a vacuum for inhalation and relaxes for exhalation.

Joseph Priestly

The scientist who in 1772 found that a sprig of mint could 'revive' air for a candle or a mouse in a closed environment.

Frederick Blackman

The scientist who discovered the two stages of photosynthesis in 1905 (light-dependent and light-independent).

Mechanical Digestion

The physical breakdown of food into smaller pieces to increase surface area, such as chewing or stomach churning.

Chemical Digestion

The process of using enzymes, such as protease and amylase, to break down food into smaller chemical subunits.

Chyme

A mixture of semi-digested food and gastric juices formed in the stomach.

Villi

Tiny folds in the walls of the small intestine that increase surface area for the absorption of nutrients into the bloodstream.

Transpiration-Cohesion-Tension theory

The theory explaining water movement in xylem as a result of evaporation from leaves (transpiration), hydrogen bonding (cohesion), and suction (tension).

Source-Sink Theory

Also known as translocation, it describes the movement of sugars in phloem from production sites (sources) to storage or use sites (sinks) using energy.

Systemic Circulation

The pathway of the circulatory system that pumps oxygenated blood from the heart to the body and returns deoxygenated blood to the heart.

Pulmonary Circulation

The pathway of blood from the heart to the lungs for oxygenation and back to the heart.

Arteries

Thick-walled blood vessels with muscular and elastic tissue that carry blood under high pressure away from the heart.

Veins

Thin-walled blood vessels with large lumens and valves that carry blood under low pressure back toward the heart.

Capillaries

The most numerous and smallest blood vessels, with walls only one cell thick to facilitate the efficient diffusion of gases and nutrients.

Plasma

The fluid component of blood, making up approximately $55\%$ of its volume, consisting of $90\%$ water and various dissolved proteins, salts, and nutrients.

Red Blood Cells (erythrocytes)

Bioconcave discs roughly $7 \text{-} 8\,\mu m$ in diameter that contain haemoglobin to transport oxygen around the body.

White Blood Cells (leukocytes)

Cells of the immune system that protect the body from infection by engulfing pathogens through phagocytosis.

Platelets (thrombocytes)

Cell fragments made in bone marrow that work with fibrinogen to facilitate blood clotting (thrombosis).

Open Circulatory System

A system where haemolymph flows freely around the body cavity, bathing tissues directly, common in invertebrates like insects.

Closed Circulatory System

A system where blood is enclosed within vessels and pumped at high pressure, common in vertebrates like mammals.

Haemolymph

The transport fluid in open circulatory systems, consisting of a mix of blood and extracellular fluid without red blood cells.