Lesson 2 • Seeds and leaves

Within a classroom there are often students who raise their hands and offer ideas readily, as well as those who are less confident to share their ideas. The think, pair, share strategy can encourage more students to get involved because it allows thinking time and removes fear of being wrong, as students can offer ideas they have agreed upon with their partner.

In the strategy:

1. Students are prompted with a question, topic, claim or idea.
2. They are given time to think, typically between 10 and 20 seconds. The time can be extended for complex questions or topics.
3. Students pair up with someone near them to discuss their answers and ideas.
4. Invite students to share with the class, starting with "(Student's name) and I discussed/thought/talked about..."

You can also add the step ‘square’ where pairs team up with another pair to discuss further before sharing. This can be helpful to expose students to a wider range of ideas and vocabulary.

To germinate, the red kidney bean absorbs moisture, which activates enzymes within the seed. These enzymes break down complex molecules within the bean, such as starches and proteins, into simpler forms that the growing plant can use for energy and growth. The absorbed moisture softens the seed coat and triggers the germination process.

Preparation: soaking the bean overnight speeds up the germination process, and ensures more of the moisture in the resealable plastic bag is available during growth over the coming weeks.

Radicle emergence: the seed coat softens further, and it may split open. This allows the emerging root (radicle) to penetrate the seed coat and grow downwards. The radicle looks like a white thread; it anchors the seedling in place and absorbs water and nutrients from the soil.

Shoot growth: Simultaneously, the shoot begins to grow upward as a single stem. If our bean was planted in soil it would break through the soil’s surface at this point. The emerging shoot consists of the embryonic stem and leaves, encased in protective coverings called cotyledons.

Photosynthesis: As the shoot grows and the cotyledons are exposed to sunlight, they begin to carry out photosynthesis. This process converts light energy into chemical energy, providing the seedling with the energy it needs for further growth and development.

Establishment of seedling: As the seedling continues to grow, it develops true leaves and becomes increasingly independent of the stored nutrients within the seed. It establishes itself as a mature plant capable of producing its own food through photosynthesis.

Throughout this process, environmental factors such as temperature, moisture, and light play crucial roles in regulating germination. Additionally, the genetic makeup of the seed determines the timing and success of germination.

These questions have been designed to support students to make predictions about the growth of their seeds. In science, making accurate predictions relies on past observations of patterns. In this instance, the plausibility of students’ predictions, or if they are able to make a prediction, will depend upon their prior experiences with seed germination.

Exploration of the schoolgrounds… can lead to knowledge and understanding of concepts about the living world, and to the development of science skills… Schoolground investigations can also lead to attitudinal development in regards to animals and their habitat, such as greater valuing and sense of responsibility towards animals and their environment, as well as a development of interest in detail of animal structure and behaviour, and interactions between animals and plants. 

Skamp, K. & Preston, C. (2021). Teaching Primary Science Constructively 7th edition. South Melbourne: Cengage Learning Australia.

Throughout this teaching sequence, we encourage students to progress from random hunting, showing minimal regard for animals, to directed hunting, showing concern for larger plants and animals and recognising the similarities and differences.  

More details of these two developmental stages are described below.

Random hunting

• Recognises that many plants and animals coexist but does not think they interact in any significant way
• Carries out simple observations to answer simple questions, sorts animals according to simple criteria
• Sees animals as interesting play objects, sees plants as inhibiting hunting activity, shows minimal regard for animals

 Directed hunting/collecting of particular animals or types of animals

• Explains that the environment supports a diversity of animals with different characteristics
• Recognises patterns in animal behaviour
• Groups data concerning diversity of animals in simple block-and-column format
• Makes a record of observations using simple drawings
• Shows interest in the variety of invertebrates
• Shows concern for the welfare of larger animals
• Asks the names of invertebrates rather than how or why questions

In the Crackle and crunch investigation, students sort leaves into groups according to their colour and the sound they make.

Leaves may fall from trees and bushes/shrubs for various reasons, including natural cycles, disease, strong wind or rain, or by human influence. Fallen leaves that appear green detached from the tree when they were still 'living'. They retain moisture and therefore will not make a loud sound when 'crunched' up. The longer a green leaf has been disconnected from the branch, trunk and roots the drier it will become, as it is not able to draw in any further moisture. As the leaf turns yellow through to brown it will make an increasingly loud sound when 'crunched' up.

Leaves might also change colour whilst still on the tree, falling off when the leaf stem softens or dries out enough for them to detach. This will happen most noticeably with deciduous trees.

Deciduous trees lose their leaves cyclically, typically as they are preparing for the cold, winter months, or to prepare for the lack of water during the dry season. These trees become dormant as they break down and reabsorb the green chlorophyll in the leaves, allowing the already present yellow and red pigments to become visible before the leaves eventually dry out and fall off.

There are only a few Australian native trees that are truly deciduous including the red cedar (Toona ciliata), white cedar (Melia azedarach) and boab (Adansonia gregorii) trees. These trees lose some or all of their leaves in the dry season to reduce water evaporation when there is little rainfall. In contrast, the Tasmanian beech or Fagus (Nothofus gunnii) drops all of its leaves after a colourful autumn season. There are also many imported species of deciduous trees and shrubs planted in schools, parks and gardens across Australia.

The leaves of evergreen trees will also change colour whilst still attached to the tree before eventually falling off. However this does not typically happen all at once, but rather occurs sporadically all year round, often as branches grow and become too thick to support leaves.

It is not necessary for students in Foundation to understand these distinctions. They may, however, be helpful in determining the type of leaves that will be most readily available to students during different times of year, and where they might be found. During this investigation simply focusing on how the leaves on some trees change colour as they dry out will support students when they do the leaf rubbings.

In the Leaf rubbings investigation, students might notice a difference between the rubbings created by freshly fallen leaves and those that have been on the ground for longer.

The venation (vein-like structures) of the leaf hold its structure longer than the rest of the leaf. As a leaf dries out, the venation will become more prominent and noticeable. This is particularly interesting with larger leaves, which will have a large network of veins for students to observe. The venation will be different for each tree species. Some leaves have a single 'vein' running along the centre that disperses smaller veins to the edges of the leaf. Other leaves (like maple leaves) have a series of larger veins moving to key parts of the leaf. Discussing why larger leaves have more veins, and sorting leaves by size is an explicit way to get students thinking about why the size and shape of leaves are important, even if they don't consider this aspect in great detail at this stage.

There are multiple ways to sort the leaves based on their observable features. Understanding your students’ mathematical capability will help to guide any decisions you make when adapting the leaf sorting activities (Crackle and crunch and Leaf rubbings) to your students’ needs, and provide guidance on when support for students may be required.

In Foundation, students “collect, sort and compare data represented by objects in response to given investigative questions that relate to familiar situations” (AC9MFST01).

In Year 1, students "make, compare and classify familiar shapes; recognise familiar shapes and objects in the environment, identifying the similarities and differences between them" (AC9M1SP01).

In the leaf sorting activities, the sorting students might be expected to do crosses between these content descriptions.

Consider what support your students might need, if any, in order to sort leaves by size (big leaves vs. small leaves), by shape (leaves with smooth edges vs. leaves with bumpy edges), or by colour (green vs. yellow vs. brown leaves).