Notes of Lessons: Biology, Class III

[We have thought that it might be of use to our readers (in their own families) to publish from month to month during the current year, Notes of Lessons prepared by students of the House of Education for the pupils of the Practising School. We should like to say, however, that such a Lesson is never given as a tour de force, but is always an illustration or an expansion of some part of the children’s regular studies (in the Parents’ Review School), some passage in one or other of their school books.—Ed.]

Subject: Natural History • Group: Science • Class III • Time: 30 Minutes

By Dorothy Cooke
The Parents’ Review, 1914, p. 636

Objects of the Lesson

I. To teach the girls what causes leaves in Autumn and Winter to change colour.

II. To teach them why and how leaves fall off in the Autumn.

III. To increase their knowledge of the Laws of Nature.

IV. To appeal to their imagination and their reasoning power.

Steps in Lesson

Step I.—Ask the girls what question occurs to them when they see the beautiful Autumn tints of the leaves. “What causes leaves to change colour in the Autumn?” Also what question occurs to them when they see the bare trees in Autumn and Winter. “Why do leaves fall off?” “By what means does a tree shed its leaves?”

Step II.—Explain to the girls how leaves change colour—withdrawal of chlorophyll—(chloros-green; phullor-leaf), from the leaf and the forming of Anthocyanin in its place, this gives the leaf that lovely crimson and red colour. In Beech and Oak trees the leaves are brown because of the tannin in them. Question them on this step.

Step III.—Draw from the girls the three functions of the leaf; respiration, transpiration, assimilation.

Step IV.—Explain the causes of the fall of the leaf.

(a) Frost, which hardens the ground so that the roots cannot obtain any moisture.

(b) Winds and snow, which would break off the leaves and thus leave wounds, so that the tree sap would run out.

(d) Also that the leaves, when decayed, enrich the soil at the roots of the tree. Narration.

Step V.—Explain to them “how leaves fall off.” Layer of cork cells forms between the twig and the leaf-stalk, thus cutting off from the leaf all food supply. A paragraph on the “separation layer” to be read by the girls. Explain briefly what is meant by “vascular bundles,” the little channels which carry the food into all parts of the tree, into each leaf. Narration.

Step VI.—Read to them a few lines from Longfellow on the beauty of Autumn tints, to help them to see the points of beauty in the change of the leaf as well as the scientific points.