16 Questions
What is the consistent finding about Porifera (sponges)?
They constitute a monophyletic group
Which group of animals branched off the tree before the origin of animals with bilateral symmetry?
Cnidarians
What has been a significant change in phylogeny due to molecular data?
The phylogeny of protostomes
What is the current debate regarding Ctenophores?
Their position in the animal tree of life
Why is the state of the coelom not a reliable character to infer phylogenetic relationships?
Because it has evolved many times
What is a characteristic of Lophotrochozoans?
They grow by gradual addition of mass to the body
What is a characteristic of Ecdysozoans?
They molt (undergo ecdysis)
What is a characteristic of all deuterostomes?
They have a coelom
What is the main difference between Deuterostomes and Protostomes?
Deuterostomes have fewer phyla and species than Protostomes
What is the characteristic of Echinoderms?
They are invertebrate marine animals
What is the name of the Kingdom that includes animals with true tissues?
Kingdom Eumetazoa
What is the name of the Phylum that includes Sponges?
Phylum Porifera
What is the characteristic of Sponges' growth forms?
Some Sponges have a fixed shape and size, while others can grow up to 2 m in diameter
What is the characteristic of Sponges' movement?
Larval Sponges are free-swimming, but adult Sponges are sessile
What is the characteristic of Sponges' cells?
Sponges have multiple cell types but no organized tissue
What is the structure of Sponges?
A gelatinous noncellular layer surrounded by two cell layers
Study Notes
Phylogeny of Animals
- Porifera (sponges) form a monophyletic group, meaning they consist of all descendants from one common ancestor.
- Cnidarians (hydras, sea jellies, and corals) branch off the tree before the origin of animals with bilateral symmetry (Bilateria).
Annelids and Arthropods
- Annelids (worms) and arthropods (spiders) are in separate clades (Lophotrochozoa and Ecdysozoa) despite both exhibiting segmentation.
Ctenophores and Chaetognatha
- The position of Ctenophores (sea walnuts) is currently debated.
- Whether Chaetognatha (marine worms) is a protostome or a deuterostome is unclear.
Phylogeny of Deuterostomes and Protostomes
- Deuterostomes have coeloms; protostomes are variable.
- Protostomes are divided into two clades: Lophotrochozoans (grow by gradual addition of mass) and Ecdysozoans (animals that molt, including arthropods).
Deuterostome Divisions
- Deuterostomes consist of fewer phyla and species than protostomes.
- They are more uniform in many ways, despite great differences in appearance.
- Deuterostomes include echinoderms (invertebrate marine animals) and chordates (mammals, fish, reptiles, and amphibians).
Kingdom Animalia (Metazoa)
- Kingdom Animalia is divided into two branches: Parazoa and Eumetazoa.
- Parazoa includes animals lacking tissues and organs, such as sponges.
- Eumetazoa includes animals with true tissues, organs, and organ systems.
Phylum Porifera (Sponges)
- Sponges are marine animals, with 26,000 species, and 150 freshwater species.
- Most sponges lack symmetry, have various growth forms, and some are capable of movement.
Sponge Characteristics
- Sponges have a "vaselike" shape with three functional layers of cells.
- They consist of a gelatinous noncellular layer (mesohyl) between two cell layers.
- Sponges are multicellular but lack organized tissue.
Learn about the evolutionary relationships between different animal groups, including Porifera, Eumetazoa, cnidarians, and Bilateria.
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