The main feature of algae plants is 1. Single cell and multicellular structures are relatively simple, and there is no differentiation of roots, leaves, stems and other organs.
2. Cells all contain chloroplasts, which can carry out photosynthesis.
Most people live in water.
Algae reproduce in three ways, namely vegetative reproduction (by cell division or rupture), asexual reproduction (by releasing zoospores or other spores) or sexual reproduction. Among them, sexual reproduction is rarely used and generally occurs in difficult times (at the end of the growing season or under unfavorable environmental conditions).
There are many methods of vegetative propagation, including special vegetative branches, such as those of Haematococcus, which grow into new individuals independently after landing; There are propagation methods that rely on false roots, such as seaweed; Others rely on discoid larvae to spend summer or winter. Asexual reproduction mainly depends on zoospores, which generally have 1 ~ 4 flagella, chloroplasts and eye spots, have no cell wall and have the ability to swim freely; There are also many spores that cannot swim because of lack of flagella, such as endospores of Cyanophyta, tetraspores of Rhodophyta and sclerenchyma of Chlorophyta.
Sexual reproduction depends on gametes, which can be homozygous or heterozygous. Homogamy is that gametes with the same shape and size approach each other and fuse to form a thick-walled zygote, while heterogamy is that gametes with different sizes or even shapes fuse to form a zygote. Egg mating is a kind of heterozygosity. Its female cells are large and generally can't swim, while its male cells are small and have two flagella, so they can swim freely. The eggs of red algae are particularly special. Egg sac is called fruit cell and is a bottle-shaped structure. The egg is at the bottom of the bottle, and the bottleneck is the fertilized silk. However, the sperm in the seminal vesicle can't swim, but will drift with the flow. When it meets the fertilized silk, it sticks to it, and the sperm breaks out of the capsule and enters the fruit cell along the fertilized silk to combine with the egg to form a zygote. The latter immediately developed into diploid fruit sporophyte and parasitized on female individuals. Fruit sporophytes mature to produce fruit spores, which develop into independent sporophytes.