Why was an algae cell included along with the plant and animal cells? Use complete sentences.

Explanation:

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)

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.