since a Lychen is a symbiotic partnership between a Fungi and Algae:

The Algae is capable of living through photosynthesis and the Fungi somehow is parasitic to the Algae. However, I'm not sure how Algae benefits from this symbiotic relationship.

As human beings for example, we are symbiotic with trees in that trees breathe out Oxygen converted from the Carbon Dioxide we breathe out along with all mammals that breathe. So, trees are somewhat necessary for humans to have enough fresh Oxygen to breathe all over the planet. I think this is one of the many reasons why people who live away from trees in places like big cities have so many health problems. However, walking or jogging around a grove of trees making fresh oxygen for you to breathe will often help not only your physical health but mental health as well for a variety of reasons.

So, obviously I have a lot to learn regarding Lychen because I'm only recently learning about it. For example, before this I vaguely realized that Fungi included Mushrooms and Yeasts but wasn't entirely sure about the yeasts. I recently learned that Yeasts are also a type of Fungi and that Athletes foot and Jock Itch (pretty much the same thing in different places) are a yeast which is also in the fungi Family.

So, I'm slowly learning as it becomes useful or interesting to me more about Fungi and Lychens which are somewhat related.

Also, recently I talked with a friend who is an 83 year old still practicing lawyer who considers himself to be a lychenologist. So, maybe I will ask him some questions about all this the next time I see him. 

I was able to find the answer I was looking for online by asking the following question: "How does the algae benefit in a symbiotic relationship regarding Lichen?"

Here is the answer I received:

begin quote:

In a symbiotic relationship, two organisms function in a way that is mutually beneficial. Because the algae derive nutrients through photosynthesis, and the fungi protect the algae from drying out, lichen can live and grow in extremely barren areas.Feb 27, 2023

Lichen, Algae, and Moss on Trees

end quote.

Also, I just learned that Lichens are  non-destructive in other words they do not hasten the death of Trees and plants. I also learned that 6% of the earth's surface is covered with Lichens which I found interesting.

They live primarily by the Algae part of the lychen's photsynthesis. The Fungi part of the lychen symbiosis keeps the Algae part moist so the lichen symbiosis can live in really dry parts of the world for example, on Rocks and boulders and still survive from photosynthesis. (light from the sun).