Hey,

The process involving growth and development leading to different morphological and cytological changes is referred as Life Cycle.

Algae basically comprises of five different types of Life Cycle,

- Haplontic Life Cycle:

Gametophyte (n) ---->Gametes-(n)---> Fusion of Gametes to form Zygote (2n)-----> Meiosis in Zygote to form Haploid Zoospores (n).

- Diplontic Life Cycle:

Gametes (n) -----> Zygote (2n)----->  Mitosis in Zygote to form Sporophyte ( 2n)

-Haplo- Diplontic Life Cycle:

Gametes (n) -----> Zygote (2n) -----> Mitosis to form Sporophyte-(2n) ---> Meiosis in Sporophyte to form Zoospores ( n).

- Haplobiontic Live Cycle:

Gametes(n) ---> Zygote-(2n)-->Meioisis in Zygote to form Carposporophyte(n) ----> Carpospores(n).

- Haplo-diplontic Life Cycle:

Gametophyte (n) -> Gametes(n) -> Fusion to form Zygote (2n) -> Mitosis to form Carposporophyte( 2n) -> Carpospores( 2n) -> Tertrasporophyte( 2n) -> Meiosis to form Tetraspore (n).

Above are the fives stages in the life cycle of algae.

note: 'n' represents haploid nature

'2n' represents diploid nature.

Hope that helps.

Thank you