NOVEMBER 2012
SCIENCE LESSON PLAN
SUBJECT SCIENCE
CLASS PIONEER
PERIOD/TIME 2 Periods/80 minutes
THEME Systems
TOPIC Plant system
LEARNING OBJECTIVES The theme introduces pupils to:
 A system is a whole consisting of parts that work together to perform
a function.
 Natural and man-made systems.
LEARNING OUTCOMES Students are able to:
 Identify parts of plants and state their functions.
 Show curiosity in exploring the surrounding plants and question
what they find.
INSTRUCTIONAL MATERIAL
 Introduction: National Geographic video, laptop, LCD projector, set
of speakers.
 Main Lesson : Science textbook.
 Conclusion : NGX Pioneer magazine, NGX Pioneer digital magazine.
SKILLS AND PROCESSES Observing and comparing.
ETHICS AND VALUES Curiosity and objectivity.
Introduction (10 minutes)
Prepare a set of speakers for the lesson. Have the students view a National Geographic video on plants found at the
link:
http://video.nationalgeographic.com/video/kids/green-kids/plants-kids/
Then ask the class:
The video shows the importance of plants.
What would the world be like if there were no plants on Earth?
How do you think plants are able to get as much sunlight as possible during the day?
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Introduce the topic of the lesson:
In today’s lesson, we will learn about leaves and their functions.
Main Lesson (50 minutes)
The sun is at the centre of our solar system and it is the only star in our galaxy. The diameter of the sun can hold more than
100 Earths! The sun is actually a huge mass of burning gases. About 75% of the sun’s mass is hydrogen and the rest is mostly
helium, with some amounts of oxygen, neon, carbon and iron. The sun is our main source of energy, providing light and heat
which are essential for living things to thrive on Earth.
Functions of Plant Leaves
Leaves come in various shapes, sizes, colours and texture but they all have several important functions: producing food which
sustains all other life on earth, storing food on a short-term or long-term basis and regulating the amount of oxygen and
carbon dioxide in the air.
The main purpose of leaves is to photosynthesize. Because of this, leaves are often referred to as the ‘food factory’ of the plant.
During photosynthesis, the raw materials carbon dioxide and water combine to form glucose and oxygen in the presence of
light energy. Light energy from the sun is absorbed by the green pigment chlorophyll in the leaves. Carbon dioxide enters the
plant through tiny openings called stomata present in the leaves. The stoma consists of a pore surrounded by a pair of
sausage-shaped cells called guard cells. The stomata regulate the gases that enter and leave the plant by opening or closing the
pores.
Transpiration refers to the process whereby water, in the form of water vapour, escapes the plant through the stomata in the
leaves. The transpiration pull refers to water being drawn up from the roots to the leaves through the system of xylem tubes
found in the stem of the plant. Transpiration also helps to cool the plant because part of the heat energy in the plant is being
used to convert liquid water to water vapour.
Leaves are also used as storage organs, either temporarily or long-term. During the day, the rate of photosynthesis is high and
a lot of glucose is produced in the leaves. Glucose is converted into starch and stored in the chloroplasts. At night, the starch is
converted back into glucose for energy or transported to other parts of the plant for storage.
Leaf adaptations
Typically, leaves are found above the ground, and are flat and thin, which maximize the surface area exposed to sunlight.
However, there are leaves that have special adaptations that make them different from the leaves we usually see. The leaves of
the aloe vera plant are succulent and fleshy because the plant stores water in its leaves. The conifers, mostly woody trees that
are evergreen, like the fir tree and pine tree, have long, thin and needle-shaped leaves.
The leaf of an angiosperm (flowering plant) consists of a petiole (leaf stalk), lamina (leaf blade), stipules and veins. The great
variety of leaves that we see around us is due to the climate and geography in which the plants grow in. Plants that live in
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areas with little sunlight generally have large, broad leaves while those in deserts have small, needle-like leaves. The desert
plant jojoba has leaves that are small and waxy to reduce water loss. Cacti in the desert have small, needle-like leaves to
reduce water loss as well as to deter desert animals from eating them. The mother’s tongue, which is an African succulent
plant, has a special adaptation which helps it avoid being eaten by herbivores. Its copper-coloured leaves make it appear to be
diseased or dead so that animals would avoid it.
Leaf parts
Leaves have a network of veins made up of strands of xylem and phloem. These veins help to transport important substances
to and from the leaves to the stems. Veins are visible and the pattern formed by the veins is called the venation. Venation can
be described as parallel or reticulate. Veins that do not subdivide and run parallel to each other have parallel venation while
those that branch out have reticulate venation.
There are many ways to classify leaves. Leaves can be classified as simple or compound. Simple leaves consist of a single blade
while compound leaves have a blade that subdivides into many smaller ones. Leaves can be classified according to the edge
(or margin). Entire leaves have smooth, even margin. Serrate leaves have jagged, saw-like edge. Sinuate leaves have deep,
wave-like edge while lobed leaves have divisions that do not reach the centre of the leaves.
Importance of plants
Scientists at University of Birmingham and Lancaster believe that growing plants on the streets can help reduce air pollution
by as much as 30%. With this in mind, London has constructed its first green wall to help reduce its air pollution. The
Mermaid event centre in Blackfriars has a 200-square-metre wall made up of 15 varieties of plants that can help reduce the air
pollution from nearby roads.
Conclusion (20 minutes)
Have the students read the article ‘Neighbours in Space’ from the National Geographic Explorer Pioneer magazine. Divide the
class into groups of four. Get students to go on a leaf walk to collect various types of fallen leaves from the neighbourhood. The
students should pay close attention to the edge or venation of the leaves while collecting them. When they return to class,
students can proceed to create leaf prints using poster paint or crayons on the space provided in their National Geographic
Explorer Pioneer worksheet.
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