Is alge considered a plant

Answer 1

Algae is a plant ... in the past they were all considered to share a common ancestor ( monophyletic ) so were all grouped in the Plant kingdom ... today they are thought to have different ancestors ( polyphyletic ) and are placed in several different divisions within the Plant kingdom while unicellular and colonial algae are placed in separate kingdom Protista ( these would not be plants since they are not multicellular despite the fact they are photosynthetic ).

Keep in mind there are bacteria capable of photosynthesis but these are all placed in the kingdom Monera which contains the bacteria and "Blue Green Algae" ... due primarily to there cell structure ( they are prokaryotic and not eukaryotic like members of the Plant kingdom ... and they are also single celled organisms amongst other differences )

It's also interesting that Fungi also were once placed in the plant Kingdom but now are placed in the Kingdom Fungi.

Good Day ...