Конспект по биологии на тему Phylum Mollusca

Phylum Molluscs

For Class 7: Animals that build shells- Lesson 1.
Methodology : Hands on experience with shells
Time needed : 40 minutes

Aim : Establish a bond with the natural world especially with ocean dwelling animals. Develop higher order thinking skills from a very young age.

Specific objectives : ( Learning outcomes that can be tested for knowledge)

1. To become familiar with the texture and shape of shells

2. To know the names and at least three features of commonly seen shells such as cowries, cones, moons, clams, whelks, mussels, top-shells, frog-shells etc.

3. (Study and understand the features necessary, to) Acquire knowledge of how molluscs adapt to their environment and of the role of humans in their habitat.

4. Develop the ability to communicate in formal scientific language ( develop specific vocabulary and its usage)

5. To develop observation, drawing and writing skills

6. To kindle and keep alive curiosity for the natural world

Teacher preparation :

This is what you need to keep ready for the class :

1. Different kinds of shells. You will need at least 3 shells per group of 4-5 students.

2. If you do not have shells then use the presentation on shells given in this website. This means you will need an LCD projector. If you do not have an LCD projector then copy the images on a transparency and use an overhead projector.

3. Notebook, pencils, colouring materials(colour pencils, crayons (oil pastels), water colour or charcoal.

4. If you are doing this during monsoon time, then you may collect the little slugs that come out during this season; you may also use garden snails but please remember that these are not molluscs that live in the ocean. They should be used for review to develop higher order thinking skills(HOTS).

Action in class :

1. Divide your class into small groups.( ideal number is 4/5 to a group)

2. Give at least 2 shells to each group.

3. Ask students to observe the shells;Feels its surface, smell it ( but not taste it). Give them 4/5 minutes to observe and talk amongst themselves about the shell.

4. By now the class noise would have reached a certain crescendo due to excitement. Calm them down so that the activity of observation and discussion is not lost in idle chitchat.

5. At the end of 5 minutes ask everyone to draw the shells given to them. This should take them close to 10 minutes.

6. At the end of 10/12 minutes ( keep some extra time for slow students) use the projector to show the parts of a shell. Your projections must show the parts of a univalve(gastropod) and bivalve shell. Ask the students to observe the parts marked on the shell and look for those parts in the shells given to them. The parts you are concentrating for this level would be : Dorsal, ventral and foot for both univalve and bialve shell; apex in the univalve shell and beak for the bivalve. The anterior- posterior concept in these shells can confuse students of this age group and hence to be dealt with only if the teacher is confident of leading a good discussion

7. Ask one student from each group to stand up and point out in her/his shell the parts mentioned. Ask them to give reasons for their answers. Ask :Why are these shells necessary ? How do the animals move?

8. In order to clarify the concept of dorsal and ventral ask the students to point out that part of their body which is dorsal and that part which is ventral. Follow it up by asking how one would know which is dorsal and which is ventral in any animal.

9. If you have time ask students to imitate a frog jumping, an elephant walking, snail crawling, a snake slithering and then question to find out whether they can say which is dorsal and ventral in each of these cases. Follow it up through questioning and discussion that the part that faces the earth ( is towards earth, generally during movement)is ventral and the part that is away from the earth is dorsal.Ask questions related to the muscular foot used for movement. Through questions find out what the students know about the term 'muscular' and 'foot'. It always helps to draw comparison with their own body to understand differences.After they have given their answers, summarise the lesson and the facts learnt so far, in order to clarify the doubts that may be there in the minds of a few students.Summary by you at the end of the class will have the following points :The shells are the houses in which certain soft-bodied animals live. The shell protects them. Each animals builds its own shell.These animals can be seen on land, freshwater and oceans, but the shells that we are studying today are those of animals seen in the oceans.Some of these animals build shells that have two parts and are called Bivlaves and those(animals) that build with one only are called univalve. The word ' valve' is used to describe the 2 portions of a bivalve shell.The tip of the univalve shell is called apex where as the pointed end of the bivalve is called beak.All animals have a dorsal and ventral portion. Similarly the shells also have a dorsal and ventral part. The term dorsal refers to that part of the body that is away from the earth where as the ventral part is the one that is towards the earth. In human body we use the term 'back' for dorsal and 'front' for ventral.Introduce the word 'secretion' as a process by which the animal makes its shell. Explain the word secretion as a process by which any animals makes substances needed for its use. Give saliva as an example of human beings make it.

Explain about shells : Depending on how an animal makes its shell, some may be smooth where as others may be rough; some would have no designs other would have patterns. They also have different colours. The colours are also because of the way the animal secretes substances for making its shell.

These soft bodied animals have a foot that is 'muscular', meaning made up of muscles,no bones; how the foot comes out and how it is used in locomotion. ( Ref to Phylum mollusca for locomotion)

10. Now ask all students to mark the parts in their diagram

11. If your class is for 40 minutes then you stop here and give them some work to do at home. This is a way of assessing how much they have understood.*1

Assessment :

Colour the drawing done in class and answer (select one or two from the questionnaire) the questions

Print out the pencil images of molluscs given and ask them to choose any one.Draw and mark the parts.
Give the questionnaire to assess what and how much they have learnt.
Pencil images for drawing, colouring and marking parts or taking with you if you are going to conduct this as an outdoor class on a beach.

Questionnaire for assessment

I.The sentences given below are incomplete. For each incomplete sentence there are three answers given. One of them is the correct one. Choose the correct answer and complete the sentences. Remember to rewrite the complete sentence.

1. Molluscs need shells to ----
a) protect their soft body
b) because they do not have bones
c) to move in water.
2. In a bivalve shell the beak can be seen on -----
a) the front of the shell
b) left side of the shell
c) dorsal side of the shell

3. In a cockroach the wings are present on the ----
a) dorsal side
b) ventral side
c) near its neck.

II. 1. Why do animals make shells?
2. What do you mean by the term Univalve?
3. what helps animals make colourful shells?