The Bilateria or bilaterians, or triploblasts, are animals with bilateral symmetry, i.e., they have a head ("anterior") and a tail ("posterior") as well as a back ("dorsal") and a belly ("ventral"); therefore they also have a left side and a right side. In contrast, radially symmetrical animals like jellyfish have a topside and a downside, but no identifiable front or back. 

The bilateria are a major group of animals, including the majority of phyla but not sponges, cnidarians, placozoans and ctenophores. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm. Nearly all are bilaterally symmetrical, or approximately so; the most notable exception is the echinoderms, which achieve near-radial symmetry as adults, but are bilaterally symmetrical as larvae. 

Except for a few phyla (i.e. flatworms and gnathostomulids), bilaterians have complete digestive tracts with a separate mouth and anus. Some bilaterians lack body cavities (acoelomates, i.e. Platyhelminthes, Gastrotricha and Gnathostomulida), while others display primary body cavities (deriving from the blastocoel, as pseudocoel) or secondary cavities (that appear "de novo", for example the coelom). 

The hypothetical most recent common ancestor of all bilateria is termed the "Urbilaterian". The nature of the first bilaterian is a matter of debate. One side suggests that acoelomates gave rise to the other groups (planuloid-aceloid hypothesis by Graff, Metchnikoff, Hyman, or ), while the other poses that the first bilaterian was a coelomate organism and the main acoelomate phyla (flatworms and gastrotrichs) have lost body cavities secondarily (the Archicoelomata hypothesis and its variations such as the Gastrea by Haeckel or Sedgwick, the Bilaterosgastrea by Gösta Jägersten , or the Trochaea by Nielsen).

Based on the article and the following list of answers, write a list of questions.

1. The bilateria
2. Yes
3. No
4. bilaterians,
5. triploblasts
6. posterior
7. ventral
8. Yes
9. anterior
10. yes
11. bilateral embryos
12. Three
13. endoderm, mesoderm, and ectoderm
14. the "Urbilaterian".
15. Yes
16. jellyfish
17. a topside and a downside
18. flatworms and gnathostomulids
19. No
20. Not all

Numbered questions:
1. what is this article about?
2. are they considered animals?
3. are sponges part of them?
4. what else are they called?
5. or?
6. what is the scientific name for the tail?
7. what about belly?
8. do they have a head?
9. what is the other word for head?
10. do all of them have a separate mouth and anus?
11. what has germ layers?
12. how many layers?
13. please name them
14. what is the most recent ancestor called?
15. is there anything that doesn't have a front or back?
16. what?
17. what do they have?
18. give me examples of phyla please.
19. do they have a digestive tract?
20. are all the bilateria bilaterally symmetrical?