Humans, animals, and plants are living organisms. They all breathe, grow, move, eat, reproduce, and are made of cells. In this lesson, we are going to learn about plants as living things, because the importance they have for the Earth and other living things, animals, and humans are huge. They play a critical role in life on Earth.
In this lesson we are going to learn:
Plants are living organisms. They have the characteristics of living things: plants are made of cells, they grow, eat, move, reproduce, and breathe (respire). Trees, grasses, and flowers are some of the plants that surround us. Other plants are herbs, ferns, mosses, shrubs. They are everywhere around us. They can be outside in nature, or we can plant them in our homes. Plants can be on land or in water. They can be of different sizes, big or very small. Plants are of different colors, white, red, purple, any color you imagine, but the most common color of plants is green. Plants can be of different shapes. But what they all have the same is their basic needs, they all need water, air, sunlight, and nutrients.
Plants can be flowering (that have flowers), like daisies, magnolias, tulips, and non-flowering (that have no flowers), like mosses and ferns. Also, there are plants that make seeds, and plants that don't make seeds.
Parts (organs) of plants include:
Each plant organ has a unique and specialized task in the life of the plant.
- Root, leaf, and stem are all vegetative structures.
- Flower, seed, and fruit make up reproductive structures.
There are many different plants and we can also find some without this “classic” structure.
Plants make their own food. The process of making food by itself is called Photosynthesis. For that process, they need the sun, carbon dioxide, and water. They take the sunlight from the sun, water from the soil with the help of their roots, and carbon dioxide from the air. With the help of the energy of the sunlight, they convert the water and the carbon dioxide into sugar and oxygen. They take the sugar as food for growth and release oxygen in the air. Oxygen is the most important gas that other living things, humans, and animals need in order to stay alive.
Carbon dioxide (CO 2) is a heavy colorless gas, which has carbon and oxygen atoms.
Oxygen (O) is one of the main elements of air and the most common element on Earth. It is necessary for the survival of people and animals.
Yes, plants most definitely can move. They do not move just like humans, or animals, but they show movements. They need to move in order to catch the sunlight, grow, or feed. Usually, they move towards the sunlight. One most known flower that always turns towards the Sun is the sunflower.
Also, plants might show movement in response to some touch. Do you know that there is a tree that folds its leaves when touched or disturbed? It is called The mimosa tree.
Plants are made of cells. Cells are the basic building block of all living organisms. But a plant can not be made of just one cell. There must be more than one cell. There are various types of plant cells, each with different functions. Plant cells have special organelles called chloroplasts, which create sugars via photosynthesis. They also have a cell wall that provides structural support.
Plants grow from seed. Inside a plant's seed, there is an embryo, which has a root, stem, and leaves. The seed should be planted into the ground. Then it will go through a process of growing called germination. Germination happens inside the seed. In order for an embryo to start growing, it needs the right combination of soil, water, and sun. After germination, the embryo will sprout. It will pop out of the seed. The roots will grow into the soil. Roots will absorb water and nutrients from the soil, and the stem will show up. Then the leaves will grow. At that moment the plant is ready to make its food. Most plants continue to grow throughout their lives. Like other multicellular organisms (organisms that are made of more than one cell), plants grow through a combination of cell growth and cell division.
Some plants don't produce flowers and seeds. Such examples are ferns and mosses, and these are called non-flowering plants. They produce spores instead of seeds. Spores are small organisms or single-cell beings that are able to grow into new organisms under the right conditions. Spore plants have a different life cycle. A parent plant sends out tiny spores containing special sets of chromosomes. These spores do not contain an embryo or food stores.
Plants do not breathe in the strictest sense of the word. Plants respire. They give out carbon dioxide and absorb oxygen from the air that surrounds them. Their tissues respire, but not in the same way humans or animals do. But do not confuse, they also take the carbon dioxide from the air, and release oxygen, but with the process of photosynthesis, not the process of respiration.
Plant reproduction is the process by which plants generate new individuals, or offspring. Plants can reproduce in two ways because reproduction can be of two types. The first way of reproduction is when one cell splits into two and will give two identical cells. That type is called asexual reproduction. This will result in plants genetically identical to the parent plants and each other. The other type of reproduction is when two cells will combine and will create a living cell. That type is called sexual reproduction. This will result in offspring genetically different from the parent or parents.
When talking about the reproduction of plants, the most common term which is connected to it is pollination. Pollen is a fine powder made up of microspores produced by male plants. Pollination occurs in flowering plants. Reproduction in flowering plants begins with the process of pollination, the transfer of pollen from the anther to the stigma on the same flower or to the stigma of another flower on the same plant, or from the anther on one plant to the stigma of another plant. Animals, insects, and wind are of big help in the process of pollination.
We know that plants provide oxygen for humans and animals. But they are also important because they are a source of food for them too.
Animals eat plants to survive. Plants have some mechanisms to protect them from being eaten by animals. One strategy they use is that they developed physical parts that can protect them. An example is thorns. Another way of protection is that they have some chemicals inside them, that can make animals itchy or sick, like the stinging nettles.
Humans eat plants too, and they play an important role in humans' diets. They are very healthy. Plants provide humans with nutrients, fibers, vitamins, water, and minerals.
Did you know that you can eat different parts of different plants from the seed to the root to the stem, and even leaves and flowers? Let's see what plant parts do you eat when you eat certain common fruits and vegetables:
| Fruits | Leaves | Roots | Seeds |
|
|
|
|
|
| Apple | Cabbage | Carrot | Wheat |
|
|
|
|
|
| Grape | Basil | Potato | Almond |
|
|
|
|
|
| Pear | Lettuce | Beetroot | Rice |
Students activity: Continue the above table, adding more edible parts of plants in each column.
Plants are very important, because:
