SafekipediaPlants are living things that belong to the group called Plantae. Most plants make their own food using energy from sunlight. They use a green substance named chlorophyll to turn carbon dioxide and water into sugar. Some plants, called parasitic plants, get food from other plants or from fungi. Most plants are made of many cells, but there are tiny plants called green algae that are just one cell.
Long ago, the word “plants” included anything that wasn’t an animal. But scientists now have a better way to group them. Today, plants are part of a group called Viridiplantae. This group includes green algae and land plants such as liverworts, mosses, ferns, conifers, and flowering plants. There are about 380,000 known types, or species, of plants. Most of these plants make seeds.
Plants range in size from very tiny to very tall. They are important for Earth because they give us oxygen and are a food source for many animals. People depend on plants for food like grain, fruit, and vegetables. We also use plants to make buildings, decorations, things to write with, and medicines. The study of plants is called botany.
Definition
Plants are living things that make their own food using sunlight. Long ago, people like Aristotle and Theophrastus studied them and learned that plants are different from animals. Later, Linnaeus helped us sort living things into groups, putting plants in their own group called the plant kingdom.
When we talk about plants, we usually mean one of four groups of organisms. These groups are different sizes, but they all make their own food from sunlight.
Further information: Kingdom (biology) § History
| Name(s) | Scope | Organisation | Description |
|---|---|---|---|
| Land plants, also known as Embryophyta | Plantae sensu strictissimo | Multicellular | Plants in the strictest sense include liverworts, hornworts, mosses, and vascular plants, as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969, Plantae Margulis, 1971). |
| Green plants, also known as Viridiplantae, Viridiphyta, Chlorobionta or Chloroplastida | Plantae sensu stricto | Some unicellular, some multicellular | Plants in a strict sense include the green algae, and land plants that emerged within them, including stoneworts. The relationships between plant groups are still being worked out, and the names given to them vary considerably. The clade Viridiplantae encompasses a group of organisms that have cellulose in their cell walls, possess chlorophylls a and b and have plastids bound by only two membranes that are capable of photosynthesis and of storing starch. This clade is the main subject of this article (e.g., Plantae Copeland, 1956). |
| Archaeplastida, also known as Plastida or Primoplantae | Plantae sensu lato | Some unicellular, some multicellular | Plants in a broad sense comprise the green plants listed above plus the red algae (Rhodophyta) and the glaucophyte algae (Glaucophyta) that store Floridean starch outside the plastids, in the cytoplasm. This clade includes all of the organisms that eons ago acquired their primary chloroplasts directly by engulfing cyanobacteria (e.g., Plantae Cavalier-Smith, 1981). |
| Old definitions of plant (obsolete) | Plantae sensu amplo | Some unicellular, some multicellular | Plants in the widest sense included the unrelated groups of algae, fungi and bacteria on older, obsolete classifications (e.g. Plantae or Vegetabilia Linnaeus 1751, Plantae Haeckel 1866, Metaphyta Haeckel, 1894, Plantae Whittaker, 1969). |
Evolution
There are many kinds of species of plants. Most plants can make seeds. Plants come in many sizes. Some are very small single-celled organisms. Others are very tall trees, like the Sequoia sempervirens.
Plants first grew on land about 450 million years ago. Over time, they grew with roots, leaves, and wood. Long ago, during the Carboniferous period, big forests grew in wet places. Later, flowers appeared and became common, even when dinosaurs lived.
| Informal group | Division name (Phylum) | Common name | No. of living species |
|---|---|---|---|
| Green algae | Chlorophyta | Green algae (chlorophytes) | 3800–4300 |
| Charophyta | Green algae (e.g. desmids & stoneworts) | 2800–6000 | |
| Bryophytes (mosses, hornworts, and liverworts) | Marchantiophyta | Liverworts | 6000–8000 |
| Anthocerotophyta | Hornworts | 100–200 | |
| Bryophyta | Mosses | 12000 | |
| Pteridophytes (ferns and allies) | Lycopodiophyta | Clubmosses | 1200 |
| Polypodiophyta | Ferns, whisk ferns & horsetails | 11000 | |
| Spermatophytes (seed plants) | Cycadophyta | Cycads | 160 |
| Ginkgophyta | Ginkgo | 1 | |
| Pinophyta | Conifers | 630 | |
| Gnetophyta | Gnetophytes | 70 | |
| Angiospermae | Flowering plants | 258650 |
Physiology
Plants have special parts that help them live and grow. Their cells have a big space filled with water called a vacuole. They also have strong walls made of cellulose. Inside the cells are chloroplasts that help the plant make food from sunlight. These chloroplasts came from tiny sea creatures called cyanobacteria that lived inside plant cells long ago.
Most plants are made of many cells that work together. They have roots to take in water, stems to hold them up, and leaves to catch sunlight. Some plants also have flowers to make new plants. Plants use a process called photosynthesis to turn sunlight, water, and carbon dioxide into food and oxygen. This oxygen is what we breathe!
Plants need the right temperature, water, light, and nutrients to grow well. If it gets too cold or dry, some plants can protect themselves.
When it’s time to make new plants, they can do this in two ways. Some plants make flowers with parts that create tiny seeds. Others can grow new plants from pieces of themselves.
Ecology
Plants grow almost everywhere on Earth. They live in many places, like grasslands, savannas, and tropical rainforests. Only a few tough plants, like mosses and lichens, can survive in Antarctica.
Plants are very important because they make their own food using sunlight. This process is called photosynthesis. It also puts oxygen into the air, which most animals need to live. Plants are a main food source for many animals and are the start of most food chains. They make up most of the living material on Earth.
Importance to humans
Main article: Human uses of plants
Plants are very important to humans. They give us food, medicine, and materials for building and clothing. We grow crops like rice, wheat, and potatoes for food. We also get oils from plants and enjoy drinks like coffee and tea.
Plants also help us in other ways. They provide medicines, like aspirin and quinine. We use plants to make things like paper, clothes, and rubber. Some plants are grown just for their beauty, like flowers in gardens or trees in parks.
Images
This article is a child-friendly adaptation of the Wikipedia article on Plant, available under CC BY-SA 4.0.
Images from Wikimedia Commons. Tap any image to view credits and license.