Explain the similarities and differences between algae and plants?

Diffrences
plants have complex transportation systems (xylem) to transport water it goes from a source (water) to a sink (leaves) and algae doesn't have connective tissue instead all the cells absorb water directly from the source

plants have numerous ways to reproduce and such as forming seeds or asexually while algae tends to have more primitive and less numerous ways to reproduce. 

plants are multi-cellular organisms while algae can be multi-cellular and uni-cellular or even colonial

they occupy different kingdoms plant: plantae and algae: protista 

many algae can move through water via many mechanisms such as tails like flagella to swim through water 

Similarities 
both plants and algae tend to be non-locomotive they can both have root like structures to support themselves

they are both Eukaryota cells as they have cells with many components 

they are both autotrophic (make their ow food) can both photosynthesise by the absorption of sunlight 

they can both be found in many environment and in a large variety of biomes 
 
hope that helps 

Algae can be unicellular, colonial, or multicellular. However, plants are multicellular. Hodstafs, stapes, and blades are what composed the algae and plants, on the other hand, are composed of roots, leaves, trunk, stem, etc. Plants are also generally found in land while the algae are usually in water. These two may seemingly appear similar. 

In the air and in the lower fre ah water