Green algae

Green algae are a group of plants that have chlorophyll and make their own food through photosynthesis. You can find them in many places, like freshwater, oceans, and even on land. There are about 22,000 types of green algae, and they come in many shapes and sizes—from very tiny single cells to large seaweeds you can see with your eyes.

Many green algae live most of their lives as single cells, but some form groups, long threads, or even big, multicellular plants. Some other small creatures, like certain types of dinoflagellates, euglenids, and flatworms, rely on green algae to help them make food.

Green algae also have special partnerships with fungi, forming what we call lichens. In these partnerships, the green algae make food through photosynthesis, while the fungi give them protection and support. Without the algae, the fungi usually cannot survive on their own.

Cellular structure

Green algae have special parts called chloroplasts that contain chlorophyll a and b. These give them their bright green color. They also have other colorful substances like beta carotene and xanthophylls. Their cells are surrounded by walls made of cellulose. They store energy as starch.

These algae also have structures called mitochondria that help them make energy. Some green algae can move using tiny hair-like structures called flagella. These are anchored by a network of tiny tubes known as microtubules. Different types of green algae divide in different ways, but they all have these basic parts that help them grow and live.

Origins

Photosynthetic eukaryotes began when a cell absorbed a tiny, plant-like organism called a cyanobacterium. This tiny organism lived inside the cell and changed over time to become a special part of the cell known as the plastid. This important event led to the creation of three groups of plant-like organisms: the (green) plants, the red algae, and the glaucophytes.

Evolution and classification

Green algae are a group of plants. They, together with land plants, form a green plant clade called Viridiplantae (or Chlorobionta).

They belong to a larger group called Primoplantae. This group also includes red algae and glaucophyte algae.

Green plants divided into two main groups long ago. One group is the Chlorophyta. This group has many common green algae. The other group is the Streptophyta. This group includes charophytes and land plants. Scientists study these groups to learn about plant evolution.

Reproduction

Green algae are simple, plant-like organisms that can make their own food using sunlight. They have different ways of reproducing.

Some green algae switch between two forms during their life cycle. These forms can look the same or different.

In some green algae, small cells join together to create a new organism.

When certain thread-like green algae reproduce, they form bridges between cells and leave empty walls behind. Scientists can see this under a microscope.

Some green algae, like Volvox, live in groups. They can produce special chemicals that help them know when to reproduce.

Physiology

Green algae help scientists learn about cells. They show how cells control water and salt. They teach us how cell membranes let things pass through. They also help us understand how cells keep their shape and deal with changes in salt levels. Researchers study green algae to learn how cells move things inside them and send electrical signals.