Biology • Year 11 • Module 2 • Lesson 4
Organs, Organ Systems and Hierarchical Organisation
Apply the hierarchy, emergent properties and the organ/tissue distinction to real biological structures, data and scenarios.
1. Identify organ systems from organ lists
Each row below lists the major organs of one organ system. Name the organ system, state its primary function, and add one more organ that belongs to it. 12 marks
| Organs given | Organ system | Primary function | One more organ |
|---|---|---|---|
| Lungs, trachea, bronchi, diaphragm | |||
| Brain, spinal cord, sense organs | |||
| Kidneys, ureters, bladder | |||
| Skin, sweat glands, hair |
2. Interpret data, comparing levels of organisation
The figure below models the relative contractile force produced at three successive levels of the cardiovascular hierarchy: a single cardiomyocyte, a small bundle of cardiac muscle tissue, and the whole heart. 6 marks
Illustrative model of force scaling across hierarchical levels of the cardiovascular system. Not to scale for cell vs bundle.
2.1 Describe the trend in contractile force as you move from a single cell to the tissue bundle to the whole heart. 2 marks
2.2 The force of the whole heart (4800 units) is much greater than 100 times the force of a single cell (100 × 1 = 100 units). Using lesson content, explain why the whole heart produces disproportionately greater force. 2 marks
2.3 Identify the biological concept illustrated by this data and explain why it is central to justifying hierarchical organisation. 2 marks
3. Diagram critique, what’s wrong with this student’s statement?
A Year 11 student writes the following explanation in an exam. There are three biological errors. Identify each error and write the correction. 6 marks
“Organs and tissues are basically the same thing, they’re both just collections of cells. The heart is a tissue because it contains only cardiac muscle cells. When cells group together to form tissues and then organs, no new functions appear, the whole is just the sum of its parts. The cardiovascular system includes just the heart and blood.”
3.1 Error 1: What is wrong?
Correction:
3.2 Error 2: What is wrong?
Correction:
3.3 Error 3: What is wrong?
Correction:
4. Apply to a new scenario, the leaf as a plant organ
A student argues that a leaf is “just a flat piece of tissue, not an organ.” Use your understanding of tissue types and organ definition to evaluate this claim and trace the hierarchy for the shoot system. 5 marks
4.1 Identify three distinct tissue types found in a leaf and state the function of each. 3 marks
4.2 Explain whether the student’s claim is correct, using the structural definition of an organ. 2 marks
Q1, Organ systems from organ lists
Row 1: Organ system = Respiratory system. Primary function = gas exchange (O2 into blood, CO2 out). One more organ = nose (nasal cavity) / pharynx / larynx.
Row 2: Organ system = Nervous system. Primary function = receive, process and respond to stimuli; coordinate all body systems. One more organ = nerves / peripheral ganglia.
Row 3: Organ system = Excretory / Urinary system. Primary function = filter blood; regulate water, salt and pH balance; remove nitrogenous waste. One more organ = urethra.
Row 4: Organ system = Integumentary system. Primary function = protection, thermoregulation, sensory reception. One more organ = nails / sebaceous glands / sensory receptors.
Marking criteria. 1 mark per correct organ system name; 1 mark per accurate primary function; 1 mark per valid additional organ. 3 marks × 4 rows = 12 marks.
Q2.1, Trend description (2 marks)
Contractile force increases dramatically at each higher hierarchical level [1]. The increase from a single cell (1 unit) to the tissue bundle (110 units) is substantial, but the whole heart (4800 units) produces a force far greater than either, with the jump from tissue to organ level being the most dramatic [1].
Q2.2, Why disproportionately greater force (2 marks)
The whole heart integrates not just more cardiac muscle cells but multiple tissue types, including the connective tissue valves that direct flow and the nervous tissue (SA node) that coordinates synchronous contraction across all chambers simultaneously [1]. This synchronisation means every cell contracts at precisely the right time in the right direction, multiplying force far beyond what a simple sum of individual cells could achieve [1].
Q2.3, Concept illustrated (2 marks)
The concept is emergent propertiesnew capabilities that arise from organisation at each level that did not exist at the level below [1]. It is central to justifying the hierarchy because without emergent properties there would be no advantage to having higher levels of organisation; each level must add something new that the level below cannot achieve, and this data shows the force-production advantage that emerges at the organ level [1].
Q3, Diagram critique
3.1 Error 1 (“organs and tissues are basically the same”): Organs and tissues are fundamentally different. Correction: a tissue contains only one type of cell performing a shared function; an organ integrates two or more distinct tissue types, which enables complex, multi-step functions that no single tissue type can perform alone. [1 + 1]
3.2 Error 2 (“the heart is a tissue because it contains only cardiac muscle cells”): The heart is an organ, not a tissue, and it does not contain only one cell type. Correction: the heart contains cardiac muscle tissue, epithelial tissue (lining the chambers), connective tissue (valves, fibrous skeleton) and nervous tissue (SA node, Purkinje fibres), multiple tissue types, therefore it meets the definition of an organ. [1 + 1]
3.3 Error 3 (“no new functions appear” and “cardiovascular system includes just heart and blood”): Two errors are bundled here, accept either. (a) New functions do appear at each level, this is the concept of emergent properties. Correction: at each higher level of organisation, new capabilities emerge that did not exist below; the heart’s ability to pump blood is an emergent property that no individual tissue possesses. (b) The cardiovascular system includes the heart, blood vessels (arteries, capillaries, veins) and blood, the vessels are a critical component omitted from the student’s definition. [1 + 1]
Q4.1, Tissue types in a leaf (3 marks)
Accept any three of: Ground tissue / palisade mesophyll tissuepacked with chloroplasts for photosynthesis [1]; dermal tissue / epidermisforms the outer surface, reduces water loss and contains stomata for gas exchange [1]; vascular tissue (xylem and phloem)xylem delivers water and dissolved minerals; phloem exports sucrose produced by photosynthesis [1].
Q4.2, Is the student’s claim correct? (2 marks)
The claim is incorrect [1]. A leaf integrates at least three distinct tissue types (ground/palisade mesophyll, dermal/epidermal, and vascular), so it meets the structural definition of an organ: two or more tissue types working together to perform a specific function (photosynthesis, gas exchange, and distribution of products). No single tissue type could both photosynthesise and deliver water to every cell within the organ [1].