Complete digestive system start appearing from ? ArthropodaAschelminthAnnelidaPlatyhelminth

Breakdown the Problem

1. Identify Groups: Recognize the types of organisms listed: Arthropoda, Aschelminth, Annelida, and Platyhelminth.
2. Focus on Digestive Systems: Investigate which of these groups exhibit a complete digestive system.

Relevant Concepts

1. Incomplete vs. Complete Digestive System: A complete digestive system has two openings (mouth and anus), while an incomplete digestive system has only one (mouth).

Analysis and Detail

1. Arthropoda: They possess a complete digestive system with a distinct mouth and anus and are highly organized.
2. Aschelminth: This group includes pseudocoelomates like nematodes, which also have complete digestive systems.
3. Annelida: They are segmented worms and have a complete digestive system with specialization along the gut.
4. Platyhelminth: Generally known as flatworms, they have an incomplete digestive system with only one opening.

Verify and Summarize

• Among the listed groups, Arthropoda, Aschelminth, and Annelida have complete digestive systems.
• Platyhelminth is the only group mentioned that does not have a complete digestive system, as they possess an incomplete one.

Final Answer

The complete digestive system starts appearing from Arthropoda, Aschelminth, and Annelida.