SafekipediaPlants are eukaryotic organisms that make up the kingdom Plantae. Most plants are photosynthetic, which means they get their energy from sunlight. They use a green pigment called chlorophyll in their chloroplasts to make sugars from carbon dioxide and water. There are some exceptions, like parasitic plants, which get their energy from other plants or fungi instead. Most plants are multicellular, but there are some green algae that are not.
Historically, the plant kingdom included all living things that were not animals, but definitions have changed over time. Today, plants are defined as the clade Viridiplantae, which includes green algae and land plants such as hornworts, liverworts, mosses, lycophytes, ferns, conifers, gymnosperms, and flowering plants. There are about 380,000 known species of plants, and most of them produce seeds.
Plants come in many sizes, from single cells to very tall trees. They play a vital role in Earth's ecosystems by providing oxygen and serving as a food source for many other organisms. Humans rely on plants for food, such as grain, fruit, and vegetables, as well as for building materials, ornaments, writing materials, and medicines. The scientific 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 separated plants from animals. Later, Linnaeus helped create the way we classify living things today, keeping 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 vary in size, but they all share the basic idea of being plants that can 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 about 382,000 known species of plants, and most of them can produce seeds. Plants come in all sizes, from tiny single-celled organisms to very tall trees like the Sequoia sempervirens.
Plants first appeared on land around 450 million years ago. Over time, they developed features like roots, leaves, and wood. By the time of the Carboniferous period, around 300 million years ago, large forests of different plant types grew in swampy areas. Later, flowering plants evolved and became very common, spreading quickly during the time of the dinosaurs.
| 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, strong walls made of cellulose, and chloroplasts that help them 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, leaves to catch sunlight, and 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! Some plants can also grow without sunlight by taking food from other plants.
Plants grow and fix themselves by changing with their environment. They need the right temperature, water, light, and nutrients to grow well. If conditions get too cold or dry, some plants can protect themselves. Plants can also fix tiny mistakes in their DNA when they happen.
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, like how a cutting from a plant can grow into a new one.
Ecology
Plants are found almost everywhere on Earth. They live in many different places, called biomes, such as 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, a process called photosynthesis. This process also fills the air with oxygen, which most animals need to live. Plants are the main source of food for many animals and are the base 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, materials for building and clothing, and even help make some fuels. For food, we grow crops like rice, wheat, and potatoes. 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 even rubber. Some plants are grown just for their beauty, like flowers in gardens or trees in parks.
Images
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