Suggested Teaching Sequence F
Section 10 Sensitivity, Response and Coordination
To survive, an organism must be able to respond to changes in its external and internal environments. This necessitates having mechanisms for detecting such changes and producing appropriate responses.
How sense organs detect environmental stimuli and pass the sensation into the nervous system is discussed with particular reference to the mammalian skin, eye and ear. The communicative roles played by the nervous and hormonal systems in bringing about appropriate responses for the well being of the animal should be discussed. This section closes with the response of flowering plants to the environment and the roles of phytohormones in regulating growth, differentiation and various tropisms.
Studies on the transmission of nerve impulse should also be linked to the Initiation of muscle contractions (Section 9). Knowledge of hormonal coordination prepares students for an understanding of the actions of hormones in Homeostasis (Section 11), and the Control of the menstrual cycle, Growth and Development (Section 12).
Learning objectives Possible learning and teaching activities Expected learning outcomes
Students should learn Students should be able to
10.1 Detection of environmental conditions in mammals
10.1.1 The skin
that the skin can detect various external stimuli.
Carry out an investigation on the detection of external stimuli by the skin.
state the sensory functions of the skin.
10.1.2 The eye
the mechanism of vision: functions of rods and cones, colour vision, visual sensitivity and visual acuity.
Explore students’ prior knowledge on the structure of the eye.
Dissect a mammalian eye to study its structure.
state and compare the functions of rods and cones.
explain the mechanism of colour vision.
compare the visual sensitivity and acuity of the rods and cones.
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Learning objectives Possible learning and teaching activities Expected learning outcomes
Students should learn Students should be able to
10.1.3 The ear
the structure of the ear.
the mechanism of hearing: the role of the organ of Corti, perception of sounds of different pitches and intensities.
Use model or audiovisual materials to show the structure of the ear.
Use audiovisual materials / prepared slides / photomicrographs to show the structure of the organ of Corti.
Ask students what they know about the hearing range of different mammals. Discuss how human can communicate with dogs using whistles.
Ask student to discuss how different mammals use sound, e.g. long-distance communication in whales, ultrasonic echo location in bats.
explain the roles of various parts of the ear in hearing.
the role of sacculus and utriculus in detecting the position of the head.
the role of ampulla in detecting the direction of head movement and rate of change of the position of the head.
Use audiovisual materials / prepared slides / photomicrographs to show the structure of the ampulla.
Use model or audiovisual materials to show the functioning of the sacculus, utriculus and ampulla.
explain the roles of various parts of the ear in detecting of body movement and posture.
Ask students to design and perform an investigation to find out whether hearing range decreases with age.
10.2 Nervous coordination in mammals
10.2.1 Neurone and transmission of nerve impulse
the structure and functions of different types of neurones.
Examine prepared slides or electron micrographs of neurone to study its typical structures.
state the structure and functions of the neurones.
state that the neurone is a highly specialised cell type.
nerve impulse: generation and transmission of nerve impulse; the role of Na+ and K+ ions;
production of resting and action potentials;
all-or-nothing nature of the action potential;
concept of threshold without mentioning the refractory period.
Use audiovisual materials to show the conduction of nerve impulse.
state the nature of nerve impulse.
describe the mechanism of generation and conduction of nerve impulse.
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Learning objectives Possible learning and teaching activities Expected learning outcomes
Students should learn Students should be able to
the factors affecting the rate of transmission of nerve impulses.
list the factors affecting the rate of transmission of nerve impulses.
explain the factors affecting the rate of transmission of nerve impulses.
the synaptic transmission between neurones and at neuromuscular junction without mentioning the role of calcium, spatial summation and temporal summation. [Refer to Section 9.]
Examine an electron micrograph of a synapse to study its structure.
Use audiovisual materials to show the chemical transmission at the synapse.
Ask students to search for information on how drugs affect the functioning of the synapses.
Ask students to discuss the biological principle of nerve gas as biochemical weapon.
describe the mechanism of synaptic transmission.
10.2.2 Central nervous system
the organisation of the nervous system into the central nervous system and the peripheral nervous system.
the gross structure of the human brain. Use model to illustrate the gross structure of the human brain.
Use model or diagram to illustrate the median vertical section of the human brain.
develop an appreciation of the complex organisation of the nervous system.
identify the various parts of the human brain.
the structure of the spinal cord.
the functions of the cerebrum, hypothalamus, cerebellum, medulla and spinal cord.
Examine prepared slide of T.S. mammalian spinal cord.
identify the various parts of the spinal cord.
state the functions of various parts of the central nervous system.
10.2.3 Autonomic nervous system
the control of involuntary activities by the sympathetic and parasympathetic nervous systems with reference to their antagonistic actions.
state the role of the autonomous nervous system.
describe the antagonistic actions of the sympathetic and parasympathetic nervous systems.
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Learning objectives Possible learning and teaching activities Expected learning outcomes
Students should learn Students should be able to
10.2.4 Reflex action and voluntary action
the functioning of a spinal reflex and the types of neurones involved.
the significance of spinal and cranial reflexes.
about the different nature of conditioned reflex and voluntary action.
Search for information on the significance of various reflexes, and their adaptive values, in a newborn.
Discuss the importance of reflex action,
conditioned reflex and voluntary action in everyday life.
explain the functioning of a spinal reflex and the types of neurones involved.
state the significance of spinal and cranial reflexes.
cite examples of reflex action, conditional reflex and voluntary action.
compare the nature of reflex action, conditioned reflex and voluntary action.
outline the importance of reflex action, conditioned reflex and voluntary action in everyday life.
10.3 Hormonal coordination in mammals
the nature of hormonal coordination.
the differences between nervous and hormonal coordination.
Use any hormone (e.g. insulin) as an example to illustrate the action and characteristics of hormonal coordination.
describe the nature of hormonal coordination.
compare the nature of nervous coordination and hormonal coordination.
explain the difference between the nature of nervous coordination and hormonal coordination.
the control of endocrine activity:
(1) the nervous system (e.g. adrenaline secretion under stress, oxytocin secretion in lactation);
Use flow charts to illustrate the various control mechanisms of endocrine activity.
describe the different mechanisms that control endocrine activity.
(2) the concentration of hormones (e.g.
hormonal control in menstrual cycle [Refer to Section 12.1.2.1]; and the negative feedback mechanism in thyroxine secretion); and
(3) other substances in the blood (e.g. the effects of blood glucose level on insulin and glucagon secretion).
relate the principle of negative feedback mechanism to homeostasis.
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Learning objectives Possible learning and teaching activities Expected learning outcomes
Students should learn Students should be able to
10.4 Response to the environment in flowering plants
10.4.1 Tropism
the responses of shoots to light and gravity; the responses of roots to gravity and water, including the role of auxins in phototropism and geotropism. [Refer to Section 9.4.]
Conduct demonstrations of geotropism and phototropism to show the region of perception and region of response.
state the regions of perception to light and gravity, and explain the growth responses in terms of auxins.
the experimental evidence on the region of perception and region of response in phototropism and geotropism.
Study the experiments performed by Darwin, Boysen-Jensen and Went on coleoptiles.
evaluate the design and conclusions of experiments that lead to the formulation of a mechanism for tropic movements in flowering plants.
10.4.2 Photoperiodism
the types of photoperiodic responses in flowering.
the significance of photoperiodism in control of flowering.
Search for information on examples of long-day plant, short-day plant and day-neutral plant.
describe the phenomenon of photoperiodism in flowering.
develop an awareness of the commercial applications and implications of photoperiodism in the control of flowering.
10.4.3 Phytohormones
phytohormones as biological substances to regulate growth and differentiation, e.g. auxins, gibberellins and ethylene (ethene).
state the roles of phytohormones in regulating growth, differentiation and various tropisms.
the applications of phytohormones in agriculture and horticulture.
Search for information on the applications of phytohormones.
suggest how phytohormones can be used in agriculture and horticulture.
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