Plant and animal response (5.1.5)
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Delivery guides are designed to represent a body of knowledge about teaching a particular topic and contain:
- Content: A clear outline of the content covered by the delivery guide;
- Thinking Conceptually: Expert guidance on the key concepts involved, common difficulties students may have, approaches to teaching that can help students understand these concepts and how this topic links conceptually to other areas of the subject;
- Thinking Contextually: A range of suggested teaching activities using a variety of themes so that different activities can be selected which best suit particular classes, learning styles or teaching approaches.
|Content (from A-level)
The content from the specification that is covered by this delivery guide is:
|(a)||(i) the types of plant responses
(ii) practical investigations into phototropism and geotropism
|To include the response to abiotic stress and herbivory e.g. chemical defences (such as tannins, alkaloids and pheromones), folding in response to touch (Mimosa pudica)|
the range of tropisms in plants.
|(b)||the roles of plant hormones||To include the role of hormones in leaf loss in deciduous plants, seed germination and stomatal closure.|
|(c)||the experimental evidence for the role of auxins in the control of apical dominance||HSW5|
|(d)||the experimental evidence for the role of gibberellin in the control of stem elongation and seed germination||HSW5|
|(e)||practical investigations into the effect of plant hormones on growth||An opportunity for serial dilution.
An opportunity to use standard deviation to measure the spread of a set of data.
M0.2, M1.1, M1.2, M1.3, M1.4, M1.6, M1.9, M1.10, M3.1, M3.2
|(f)||the commercial use of plant hormones||To include the use of hormones to control ripening, the use of rooting powders and hormonal weed killers.
|(g)||the organisation of the mammalian nervous system||To include the structural organisation of the nervous system into the central and peripheral systems
the functional organisation into the somatic and autonomic nervous systems.
|(h)||the structure of the human brain and the functions of its parts||To include the gross structure of the human brain
the functions of the cerebrum, cerebellum, medulla oblongata, hypothalamus and pituitary gland.
|(i)||reflex actions||To include knee jerk reflex and blinking reflex, with reference to the survival value of reflex actions.
M0.1, M0.2, M1.1, M1.2, M1.3, M1.6
|(j)||the coordination of responses by the nervous and endocrine systems||To include the ‘fight or flight’ response to environmental stimuli in mammals
the action of hormones in cell signalling (studied in outline only) with reference to adrenaline (first messenger), activation of adenylyl cyclase, and cyclic AMP (second messenger).
|(k)||the effects of hormones and nervous mechanisms on heart rate||An opportunity to monitor physiological functions, for example with pulse rate measurements before, during and after exercise or sensors to record electrical activity in the heart.
An opportunity to use standard deviation to measure the spread of a set of data and/or Student’s t-test to compare means of data values of two sets of data.
M0.1, M0.2, M0.3, M1.1, M1.2, M1.3, M1.6, M1.10, M3.1
|(l)||(i) the structure of mammalian muscle and the mechanism of muscular contraction
(ii) the examination of stained sections or photomicrographs of skeletal muscle.
|To include the structural and functional differences between skeletal, involuntary and cardiac muscle
the action of neuromuscular junctions
the sliding filament model of muscular contraction and the role of ATP, and how the supply of ATP is maintained in muscles by creatine phosphate.
An opportunity to monitor muscle contraction and fatigue using sensors to record electrical activity.
PAG1, PAG10, PAG11
Plant Growth, Development & Response to the Environment (Sumanas Inc)
Animation showing plant responses and roles of plant hormones, useful for a class introduction to plant responses and hormones. There are interactive tasks at intervals so the animation could also be used for individual study, e.g. as part of a VLE package of activities. The ‘Go To’ button can be used to navigate backwards or forwards through the topics to select a certain topic area.
Overview of Plant Defences Against Pathogens and Herbivores (American Phytopathological Society)
Summary article reviewing plant defences for use by the teacher in preparing lesson or by able students as a research resource. It covers physical defences (e.g. hairs, thorns) and chemical defences mentioned on the syllabus including tannins, alkaloids and volatile organic compounds that repel herbivores or attract predators, as well as other plant secondary metabolites with a role in plant defence.
Video of sensitive plant reacting to touch (see resource). This 4 minute video was filmed in the wild with a soundtrack of birds and insects, and shows the response of the plant to a grasshopper trying to feed on the plant as well as to human touch. The footage is displayed with copyright permission from the BBC Natural History Unit.
Fact sheet on the South American species Mimosa pudica including plant description, distribution and status as an invasive weed in Africa (see resource). Seismonasty (response to touch) in other mimosa species is described, and related sleep movements in other legumes. This species is sometimes on sale in garden centres and arouses great interest from students if a live specimen can be procured. Banging the pot down on the bench causes all the leaves to collapse simultaneously.
Falling of Autumn Leaves (see How plants work resource).
This is an up to date description of role of ethylene in leaf abscission for use as an individual study resource for students.
Neuroscience for Kids
Excellent factual website on all aspects of the nervous system (see resource). It can be used for individual study if a worksheet for students to complete is designed to match the learning outcomes targeted. The opening page covers the divisions of the nervous system, the main areas of the brain, and a link to the ‘Brain Fly-Through Game’. Click on ‘explore’ on the left for a list of topics to research, e.g. Brain Basics, The Spinal Cord, The Autonomic Nervous System plus interactive word search puzzle.
The Nervous System
The first 6 minutes of this 12 minute video summary of the nervous system deals with the structural and functional organisation of the nervous system in a pacey and memorable way (see resource). Some link to function of neurones (5.1.3b)
Two-Neuron Knee Jerk Reflex Arc
Knee jerk reflex animation and interactive labelling and word-matching exercises ideal for individual use within a class setting, or on the whiteboard for group learning (see resource).
The Fight or Flight Response
Video animation explaining the fight or flight response at the molecular level (see resource). The signalling molecule described is adrenaline, but students need to make the connection that noradrenaline from neurones of the sympathetic nervous system has the same effect but is secreted at the target organ, rather than travelling in the bloodstream.
Nervous and Hormonal Control of Heart Rate
Powerpoint summarising nervous and hormonal control of heart rate (see resource).
Big Guns: The Muscular System
13 minute video summary of what muscles are and how they work, presented in an engaging, down-to-earth fashion (see resource). A cooked chicken breast is used to introduce the tissue organisation of muscle. The presentation features colourful animated graphics. A table of contents at the end allows students to return to specific topics to revise them.
Approaches to teaching the content
The concept of plant hormones can be introduced by comparing them with animal hormones, and highlighting the lack of nervous communication in most plants. Reference to rapid changes in potential difference over cell membranes in Venus Fly Trap (Dionaea muscipula) tends to pique student interest in how plants respond, as the response is quick, but it can be explained that this is an interesting exception to how most plants coordinate response. The question of why plants generally only need to respond slowly can be explored. The presence of cell walls mostly prevents movement other than by growing in one direction or another, and growth is a slow process which as in animals is best orchestrated by chemical messengers.
One conceptual area to stress is the similarity of cell signalling in animals and plants, e.g. complementary fit between plant hormone molecules and their receptors, and subsequent effects on transcription of genes (e.g. GA switches on the gene for amylase in germinating seeds by binding to the GA intracellular receptor, which causes the removal of the DELLA inhibitor from the PIF transcription factor, so PIF can now bind to the promoter of the amylase gene.) The biochemical details of how plant hormones operate are now being elucidated.
Common misconceptions or difficulties students may have
Many students find the study of plants boring, so plants with a rapid hinge mechanism like Mimosa pudica or Dionaea help to capture interest. Getting students to create their own time-lapse video material and to consider why plants respond slowly, both as a result of the limitation of cell walls and in the context of some plants’ great longevity, may help to dispel this attitude.
In the work on animal physiology students may have difficulty conceptualising the switch in scale from molecule-level events (e.g. neuromuscular junction, action of G protein and adenylyl cyclase) to whole-organism physiology (e.g. control of heart rate).
Conceptual links to other areas of the specification – useful ways to approach this topic to set students up for topics later in the course
2.1.1 (a), (g) Knowledge of plant cell structure can be related to the plant physiology level to appreciate the reason why the scope and speed of plant responses is less dramatic than in animals. The specialised structure of neurones can be used to revise 2.1.1 (a), (g) and (j) (transport of neurotransmitters and synaptic knob proteins down axon from cell body via cytoskeleton, and maintenance of cell shape).
2.1.2 The chemical nature of plant hormones and adrenaline and their receptors can be considered. (m), (n) and (o) can be revisited when teaching muscle (actin and myosin, troponin, tropomyosin, etc).
2.1.3 (c) cAMP can be related to nucleotide structure. The effect of plant hormones on stimulating transcription of genes (g) and translation to produce proteins is exemplified by GA stimulating amylase synthesis in germinating seeds.
2.1.5 Students can consider whether the different plant hormones and adrenaline are lipid-soluble or not and whether their receptors are intracellular or positioned on the cell surface membrane. The mechanisms of movement of plant hormones, to include diffusion, can also be mentioned.
2.1.6 Cytokinins stimulate cell division, so understanding of the cell cycle and mitosis can be revisited and tested at this point. (j) can be related to use of stem cells in research into ameliorating brain diseases such as Alzheimer’s and Parkinson’s.
3.1.1 (c) ABA controls opening and closing of stomata, picking up on the transpiration and plant gas exchange learning outcome.
3.1.2 (f) – (h) provides the background for understanding control of heart rate by the brain, autonomic nervous system and hormones.
4.1.1 (a) Plant pathogens may target plant hormone signalling pathways to disrupt or evade the plant’s defensive systems, Ethylene, salicylic acid and jasmonates play a central role in plant defence with the other plant hormones playing a supporting role (see review article below).
5.1.1 (a) – (c) (cell signalling, homeostasis) is relevant background to 5.1.5 (g)-(l) (animal responses), as are 5.1.3 and 5.1.4. The current section places therse elements in a variety of synoptic contexts, where links need to be made between the actions of the separate systems and principles.
5.2.2 (a) respiration provides the energy for animal responses, including transmission of action potentials, synthesis of hormones and receptors, and contraction of muscle.
6.1.1 (a) Mutations causing dwarfism in plants are related to GA deficiency, e.g. Mendel’s peas, also 6.1.2 (b).
6.1.1 (b) The mechanism by which GA switches on amylase production in germinating seeds is a good example of eukaryotic transcriptional control.
6.2.1 (b) (i) The Murashige and Skoog medium used for plant tissue culture was co-invented by Folke Skoog who also worked on apical dominance. Tissue culture plantlets are moved to media containing different ratios of plant hormones to induce shoot and root formation.
A 6 minute lecture video summarising the actions of the 5 main plant hormones, which may provide a useful summary for class use (see resource). There is a short introductory advertising video for the Brightstorm American educational website first.
Introduction to Phytohormones (see resource)
2011 overview of the traditional plant hormones (auxin, cytokinins, gibberellins, ethylene and abscisic acid) and their roles and some newly-discovered ones (brassinosteroids, strigolactones, jasmonates and salicylates). Useful for the teacher to update knowledge as this field is developing rapidly.
Disease Resistance: Role of Plant Hormones
An academic review article on the role of plant hormones in defending plants against infection, which might be of interest to teachers (see resource).
1934 Skoog and Thimann paper detailing experiments showing apical dominance (see resource).
This list of multiple choice questions on plant hormones can be used to create revision cards, bingo games, quizzes and checklists.
Students can check recall and understanding of nervous system organisation by using this drag and drop matching activity (see resource). Click on activities B and C on the left to revise brain anatomy.
Card game designed for learning outcome (j) equivalent for the previous F215 specification (see resource).
2 minute video animation showing intracellular signalling cascade triggered by binding of adrenaline (known as epinephrine in the USA) to its cell surface membrane receptor (see resource). This is followed by a quiz to test conceptual understanding and recall.
Flashcards for identifying micrographs of different types of muscle tissue.
Short video animation showing events at the neuromuscular junction, plus test quiz (see resource).
The action of plant hormones can be explored in the context of lab experiments on live plants, with suggestions provided below. The main problem is that the experiments run over a period of a week or two and students tend to lose focus and interest between lessons. Setting up a webcam or video camera to film the experiments and editing the footage to produce a time lapse effect so that the effect of the experimental conditions on the seedlings can be seen in the space of a minute or two, would enhance this activity and allow students to use their creative and technical IT skills, PAG10.
Contexts for reinforcing and extending understanding of animal nervous and hormonal responses include functional MRI studies, brain stimulation and muscle with reference to sports physiology. Ideas for practical work on the knee jerk reflex, pulse rate and muscle fatigue with reference to space travel are included.
Simple tropism practicals using radish, cress or white mustard seedlings on damp cotton wool in petri dishes, including dishes stuck to the wall to see negative geotropism of shoots and positive geotropism of roots (see resource). This could be used as an introduction to the topic. Student sheets, teacher’s notes and links to related resources are available.
A level development of the geotropism practical (see resource). White mustard seeds are germinated in agar plates. The growing roots can be examined under the microscope while still in agar and measured using an eyepiece graticule calibrated with a stage micrometer. Measurements at time intervals could be used to generate tables and graphs, and these could be used to calculate rate of growth of the roots. The dishes can be manipulated to cause changes in direction of root growth.
A microscopy practical to investigate stomatal opening and closing, to accompany teaching of role of ABA in stomatal closure. The teacher’s notes provide details of a supplier of ABA and suggest adapting the practical to investigate the effect of ABA on stomata of Asiatic Dayflower, Commelina communis (see resource).
This article reviews the use of functional MRI (magnetic resonance Imaging) of the brain to detect brain activity in patients in vegetative states and even to communicate with these patients (see resource). It provides a springboard for discussion of ethical issues about treatment of stroke patients and those in a coma, end of life decisions and for probing what it means to be conscious.
This What is fMRI resource (see resource link) explains what fMRI is, how it works and what it can be used for. This information may be required to provide the technical background for the findings described in Neuroscience: The Mind reader (above).
When students are confident with the roles of key structures in the brain and the way different functions map to different areas of the cortex, they might find this article interesting (see resource) to stimulate a discussion of whether they think this techniques is likely to be effective in boosting problem-solving and maths skills, and whether it is safe or should be regulated in some way.
Informative audio explanation (see Knee Jerk Reflex video) accompanied by speeded up line drawings to explain the context and purpose as well as the proprioception mechanism of the knee jerk reflex.
Protocol for carrying out a class investigation into the effect of exercise on pulse rate. The notes give plenty of ideas for testing other factors that influence heart rate, such as the effects of caffeine and just thinking about exercise and stressful events (see resource). Students might like to come up with their own experiments, devising a series of images or video clips that are frightening or relaxing to see the effects on viewers’ heart rates. Results can be processed to develop maths skills, e.g. finding the mean, bar charts (comparing class mean heart rate under two discontinuous situations such as with or without caffeine) or graphs (pulse rate against time measured by datalogging equipment or a wearable heart rate monitor) and testing statistical significance of any differences found.
Pulse rate experiments can be updated using date logging equipment such as a pulse oximeter. The 'Calculating heart rate' resource gives details for constructing a similar piece of apparatus for detecting changes in blood flow through an ear lobe or index finger, with sample results and teaching notes.
The Lesson on muscle fatigue resource covers a range of activities including simple experiments using elastic bands to measure muscle fatigue and lots of references to how astronauts muscles are affected by low gravity in space, as an example of an unusual context in which to teach and understand muscle.
Introduction to slow and fast twitch muscle fibres, effects on aerobic and anaerobic training and relation to different types of sporting activity, with links for further research (see resource). Likely to be of interest to students with a keen interest in sport and sports physiology.
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