As plants because they are autotrophic in their mode of nutrition.,They have photosynthetic organelle which can be used to synthesise their food by themselves.Thus they contain membrane bound chloroplast,the photosynthetic organelle peculiar to plants .They also contain mitochondria and nucleus which are all present in green plants.
In addition some algae undergo asexual reproduction which is peculiar to green plants.They are different due to lack of complexity of tissues e.g xylem,phloem present in plants etc.
They are similar to animals because they contain membrane bound organelles of mitochondrial,nucleus .These are the characteristic feature of Eukaryotas They are also capable of sexual reproduction ,and locomotion with the aid of flagella.(Chlamydomonas)
