Lesson Plan For Primary School Science

Like all arthropods, German cockroach has a skeletal system on the outside of the body. According to Book Rags Website, the skeletal system is the framework of hard, articulated structures that provide physical support, attachment for muscles, and protection for the bodies of animals. It helps to support each organism and its limb in order to save from harm the internal organs. The attachment of muscle on skeletal system is essential to give functions in locomotion. Without this system, organisms would not move.

Lacking of internal skeletons, German cockroach wears its 'bone' on the outside in the form of an exoskeleton. This lifeless shell is placed atop the epidermis. “Exoskeleton is a chitin shell secreted by the mantle, a thin sheet of epithelial tissue that extends from the body wall.” (Boloman, Berg & Martin, 2005) It consists of three layers. The outermost layer is cuticle. “The cuticle is made up of a number of very thin laminations of chitin, arranged so that the fibers in each lamination run perpendicular to those above and below it, forming a cross-hatched pattern that gives great structural strength while allowing for flexibility”. (Starr, C., Evers & Starr, L., 2007) Everything that is visible on the outside of a cockroach which include the wings, skin, legs, and hairs. They are made of a single unbroken layer of cuticle.



The cuticle layer does not have cell on it. It is dead and unable to grow. The cuticle layer is made up of two parts. The waterproof epicuticle is placed in the outer part. It contains no chitin and is highly resistant to water solvents. Beneath this is the much thicker procuticle. It can be divided into two distinct layers. An outer exocuticle is laid below the epicuticle. An inner endocuticle which consists of a large number of layers of protein and chitin and chitin fibres laid down in a laminated pattern. Beneath the cuticle layer is the epidermis, which is made up of a layer of living cells that secrete the chitin making up the outer cuticle. Beneath this is the basal membrane that separates the epidermis from the internal body fluids and organs.



“Exoskeletons restrict the growth of the animal, thus it must shed its exoskeleton (or molt) to form a new one that has room for growth.” (Huber& Maler, 1990) In order to undergo the growth process, the exoskeleton of cockroaches will be molted periodically. When the cockroach is ready to molt, the exoskeleton will split down the back and force it to climb out from the old cuticle. “The exoskeleton of a newly molted roach is white and soft, and is incapable of supporting the cockroach weight--the roach depends on its blood pressure to keep the soft cuticle from collapsing.” (Raven & Johnson, 1998) It takes six or seven molts for a newly hatched cockroach to reach sexual maturity. Once it reaches the adult stage, it will not molt again. Unlike most insects, which have a waxy coating on their exoskeleton to prevent dehydration, the thin layer of grease that cover the cockroach makes itself looks dirty. However, in reality, cockroaches are clean animals and put a lot of good effort to keep their cuticle clean of foreign matter.

“Through the attachment of muscles to the part of exoskeleton, cockroach is allowed to receive some forces as the contraction of muscle occurs.” (Hickman, C. P., Robert, L.S., Larson, A., I’Anson, H. & Eisenhour, D. J., 2006) The joint of the muscles to the rigid chitin exoskeleton enable cockroach to move. These muscles usually occur in pairs that operate to each other such as the flexor and extensor muscle which control forward and backward movement. Both of the muscles are attached to the same points of its exoskeleton to ensure the each movement can be coordinated. The extensor tibiae muscle which causes the leg to extend, and the flexor tibiae muscle which causes the leg to flex. These muscles pull on tendons which are attached to the tibia on either side of the joint pivot. These tendons can be seen by removing the cuticle from one side of the leg in the joint region




Instead of this, the link of the muscle and skeletal system also allows cockroach to fly. The antagonistic movement of elevator and depressors muscle causes its wing to beat.


Cockroach becomes one of the insect that affects our quality of life. “Spray is natural or synthetic substances used by man to control pest organisms by disrupting some part of cockroaches’ life processes.” (Octopus, B., 2007) Literally, the term pesticide means to "kill pests." Spray contains chemicals that called acetylcholinesterase. Acetyl choline (ACh) is the nerve transmitter substance released by motor neurones to stimulate muscle contraction. The muscles relax (stops contracting) when the ACh is removed from the neuromuscular junction (NMJ) by the action of acetylcholinesterase. By inhibiting the cholinesterase the cockroach can no longer break down ACh in the NMJ and so its muscles lock up in a state of tetany (continuous contraction). It makes moving and flying impossible. Through controlling the muscle contraction within the skeletal system by chemical substance, cockroach can be easily killed. However, the chemical that released brings obvious disadvantage to our environment where it contributes a lot in air pollution.

Instead of this, many insects eat their cast cuticle (exuviae) after moulting. “Exuviate eating constitutes a meal, so the animal recycles its nitrogen content. Nitrogenous compounds (protein and chitin) are major components of the cuticle. The frequency of the behaviour decreased in newly emerged adults and varied between the sexes, males eating their exuviae less frequently than females.” (Mira, A., 2000) This may be due to the extra nitrogen endowment which females need for reproduction. Alex Mira stated that that over 58% of the nitrogen presents in the exuviae was recycled through the analysis of the frass produced after exuviae meals. This demonstrated that cockroaches digested nitrogenous compounds contained in the cuticle. Therefore, for those cockroaches which have approached directly to the spray may leave some of the chemical substance on their exoskeleton. They can be killed if eating their “skin” after molting due to the toxin substances left behind.

Learning objective
Understanding the properties of materials

Learning outcomes
At the end of this lesson, pupils should be able to:
1. identify various properties of certain material.
2. record the result of experiment into table.
3. answer the worksheet correctly.

Prior knowledge
Pupils studied about some things float and some things sink in Year 1. In Year 2, pupils learned to make a complete circuit when they learnt about batteries. Pupils studied the ability of some materials to absorb water in Year 3. They have also learn about different types of materials can absorb different amount of water and also the importance of these materials ability to absorb water. Besides, they have also studied the conductors and non-conductors of electricity. They have also learnt about the term “Stretch” in the topic “spring”.

Phase/Duration	Content	Teaching and Learning Activities	Remarks/ Resources
Introduction/ Engage (5 minutes)	• Short quiz • Identified the materials of the object that they get and do prediction on its properties. (complete Worksheet 1)	1. Teachers have done the group division before the lesson by distributing a small piece of paper with name list of group members and different post for each member. For example, group leader, secretary, speaker, 1/2 keepers (in charge of materials of that group). 2. Teacher gives a brief explanation on the meaning of properties using the PowerPoint. 3. Teacher does a short quiz by displaying the questions on the PowerPoint. 4. The questions are: (a) Give one example of object that made of metal, wood, glass, rubber and plastic. [Expected answers –metal (metal ruler), wood (chair), glass (spectacle), rubber (balloon), plastic (plastic bag).] 5. Teacher distributes one different object and a worksheet (Worksheet 1) to each group while another teacher giving the pupils instruction by asking them to do prediction on the various properties of the object that given with their group members. Then, pupils need to record their prediction on the worksheet.	Process skills: 1. Prediction Resources: LCD Projector, Laptop, Worksheet 1.
Development Explore (10 Minutes)	• Do experiment • Completing Worksheet 2	1. Teacher distributes all the materials needed for the experiment and Worksheet 2 to each group. 2. Teacher gives pupils instruction of the experiment along with the PowerPoint show. 3. Pupils need to test their prediction on various properties (conduct electricity, absorb water, can be stretched and allow light to pass through.) of the object and other equipments given by the teacher. 4. Each group need to record their observation on Worksheet 2. Meanwhile, the teachers distribute each group 4 cards with the pictures of the objects they test with.	Process skills: 1. Experimenting 2. Observing Resources: Bulbs, wires, batteries, rubber bands, torches, glass crucibles, metal spoons, plastic sheets, wooden chopsticks, Worksheet 2, picture cards, colour water, tissue paper, LCD Projector, Laptop. References: Book: Science Year 4 Text Book Websites: •wikibooks •nyise •chemsoc the properties of material(green colour)
Explain (6 Minutes)	•Do presentation •Completing the table (on mahjong paper) by pasting pictures. •Discussion	1.A “Speaker” of each group will come out and tell his peers about their group discoveries. 2.Meanwhile, another member will also come out and paste the picture cards on the big table on the blackboard according to its properties. 3.Afterward, each group needs to pass up their Worksheet 1 and 2. 4.Teacher will discuss with the pupils on their conclusion.	Process skills: 1. Classification. 2. Communicate Resources: Mahjong paper (table), blue tag
Elaborate (6 Minutes)	• Questioning activities	1. Teacher show children a picture of a car (the window of a car) and make discussion with them by asking some questions (show the pictures and questions using PowerPoint). Questions: (a) Suggest/ Say out one suitable material to make the window of the car. [Expected answer: Glass] (b) What will happen if the material you suggested absorbs water and cannot allows light to pass through? [Expected answer: we will get wet, we cannot see the situation outside the car] (c) Can you use this material to make spectacle? Give a reason. [Expected answer: Yes, because it allows light to pass through.] 2. Teacher jot down students responses on the green board in form of mind-map.	Process skills: 1. Communicate Resources: LCD Projector, Laptop References: • dfes.gov.uk
Closure/Evaluate (3 Minutes)	• Repeating key concepts. • Do Worksheet 3	1. All the pupils need to clean up and the “keeper” from each group needs to return all the materials to the teacher. 2. Teacher ends the lesson by repeating the key concepts for today topic (properties of materials) 3. Each pupil needs to answer the worksheet (Worksheet 3) distribute by teacher and hand up in the next lesson.	Resources: Worksheet 3