Algae

Algae are a large group of living things that make their own food from sunlight. They are not the same as land plants. Algae can be very small, like tiny cells called microalgae, or very big, like seaweeds that can grow up to 50 metres long. Most algae live in water, especially in the ocean, but some live in freshwater. They can float in the water or stick to surfaces.

Algae do not all come from one common ancestor, so they are polyphyletic. They look different and some have special parts called chloroplasts that came from cyanobacteria. Most algae are single-celled and do not have roots, leaves, or stems. They are important because they make food from sunlight in water.

Algae are useful for people. For many years, people in East Asia have farmed seaweed to eat. Today, algae are also used to feed animals, help clean up pollution, make fuels, and help with medical and science research. They help change sunlight into useful energy and chemicals.

Etymology

The word alga comes from Latin and means "seaweed". We are not sure where the word came from, but it might be related to a Latin word meaning "be cold" or to an older word meaning "binding".

In Ancient Greek, the word for seaweed was φῦκος (phŷkos). This word also referred to a red dye made from seaweed. The study of algae is called phycology.

Description

Algae are many different kinds of living things that make their own food using sunlight, like plants. Unlike plants on land, algae can be very small, like tiny cells floating in water, or very large, like seaweed that can grow up to 50 metres long. They mostly live in water and use a green substance called chlorophyll to turn sunlight into energy.

Algae come in many shapes and sizes. Some are single cells, while others form groups or look like tiny plants with stems and branches. They can be simple, like small round cells, or complex, like the large seaweeds you might see in pictures of oceans. Even though they look different, all algae can make their own food using light.

Classification

Linnaeus was the first scientist to describe groups of algae in the 1700s. He found 14 different kinds, but only four are now true algae. Later scientists, like Samuel Gottlieb Gmelin and W. H. Harvey, helped us learn more about algae by grouping them by their colors.

Today, we know of over 50,000 living types of algae. They are sorted into 15 main groups. These groups are different in shape, the colors they use to make food, and other tiny parts inside their cells. Some algae are very small, with just one cell. Others, like seaweeds, can grow really big — up to 50 meters long!

Distribution and habitat

Algae are found almost everywhere on Earth, from tiny droplets of water to the open ocean. They spread mainly through tiny parts called spores, which can travel through water, wind, or even on other living things. Freshwater algae often move by streams and rivers, while sea algae are carried by ocean currents. Different water temperatures and nutrients create many different homes for algae, making each place unique.

Because of natural barriers like oceans and land, some algae live only in certain areas. For example, some algae are found only around the Pacific or the North Sea. Scientists can sometimes trace how algae move from one place to another, like on ships. However, mapping where all algae live is very hard because there are so many types, and many have not yet been fully studied.

Ecology

Algae are found in water, on land, and even on snow and ice. They grow in shallow oceans, deep waters, and icy places like Greenland and the Italian Alps. Algae are important in water because tiny algae called phytoplankton are the start of food chains for many sea creatures. Sometimes algae grow in very large numbers, called algal blooms. This can change the color of the water and affect other plants and animals.

Some algae live together with other organisms in a helpful way. For example, lichens are made of a fungus and an alga living together. The alga makes food from sunlight, and the fungus gives the alga a safe place to live. In coral reefs, tiny algae called Symbiodinium live inside coral animals, helping them make food and stay healthy. If these algae are lost, the coral can become damaged in a process called coral bleaching.

Evolutionary history

Algae have a long and interesting history. The oldest known algae are tiny blue-green organisms called cyanobacteria. They appeared over 2 billion years ago. These early algae could change sunlight into energy. They filled the Earth's air with oxygen, which changed life forever.

Later, some of these tiny algae were swallowed by other simple cells. This partnership helped both survive better. It led to the many different types of algae we see today, like green, red, and brown algae. Over time, some algae moved into other cells, creating more variety. This process helped shape the world and eventually led to the plants we know today.

Cultivation

Algae can be grown in different ways. One way is in large farms called seaweed farming, where seaweeds are grown in the ocean. Another way is using bioreactors. Bioreactors are special containers that help scientists grow algae in controlled conditions. These methods are important for studying and using algae for many purposes.

Main article: Seaweed farming

Uses

Biofuel

Algae can be used to make fuels that can replace fossil fuels. Algae can produce more material in a year than any other plant. This makes algae a promising source for future energy.

Fertilizer

Further information: Seaweed fertiliser

People have used seaweed for a long time to help plants grow. Today, algae are used in many ways, such as to feed animals and to help soil stay healthy. Large farms grow algae in tanks or ponds, and these algae can help clean water as well.

Food industry

See also: Edible seaweed and Algae powder

Many countries eat algae. For example, China eats over 70 kinds, Japan eats more than 20 kinds, and Ireland uses a type called dulse. Algae can be found in foods like gim from Korea and laverbread from Wales. Some algae, like Chlorella and Spirulina, are rich in healthy fats that are good for the heart.

Gelling agents

Agar, a substance from red algae, is used in labs to grow tiny living things. Alginic acid, taken from brown algae, is used to thicken foods and in medical treatments. It also helps keep flavors in dishes.

Pollution control and bioremediation

Algae can help clean water by eating harmful substances. They can be used to treat wastewater and to catch extra nutrients from farms. This not only cleans the water but also makes the algae grow, which can then be used as fertilizer.

Bioplastics

Algae can be used to make different kinds of plastics, including ones that are better for the environment. Companies are now making products like flip-flops and surfboards from algae-based plastics.

In human culture

The third island on Kunming Lake at Beijing's Summer Palace is called Zaojian Tang Dao. Its name comes from a classical Chinese character that means "algae." The island's name can be translated to "Island of the Algae-Viewing Hall" or "Island of the Hall for Reflecting on Literary Talent."

Additional images

Here is an additional image related to algae:

• Algae bladder