Invertebrates: Arthropods (Crustaceans), Echinodermata, Hemichordata, Chordata

SUPERCLASS CRUSTACEANS DEFINING FEATURES: Head bears five pairs of appendages, including two pairs of antennae.  The development includes a triangular larval form, the Nauplius  The head and thorax are almost always fused into a cephalothorax, and is covered with a calcified carapace. In some species, the carapace bears an anterior projection called the rostrum  THE DEUTEROSTOMES: during … Continue reading Invertebrates: Arthropods (Crustaceans), Echinodermata, Hemichordata, Chordata


Invertebrates: Molluscs, Arthropods

Review: bilateralism more often than not correlates with cephalization MOLLUSCS DEFINING FEATURES: the ventral (the abdominal) body wall muscles develop into a locomotory or clinging foot; the dorsal epithelium  (dorsal meaning 'upper' or referring to the back of an animal) forms a mantle, which secretes calcareous spicules or one or more shells; have a cuticular … Continue reading Invertebrates: Molluscs, Arthropods

The invertebrates: Ctenophores, Mesozoans, Platyhelminths, Annelids

THE CTENOPHORES; comb jellies: TRIPLOBLASTIC Triploblastic The ctenophores have four openings instead of just one - and undigested wastes are discharged through these anal pores They also have a mouth on top of the other four openings. Ctenophores live in the open sea They move by cilia, which are in rows which remind one of … Continue reading The invertebrates: Ctenophores, Mesozoans, Platyhelminths, Annelids

The invertebrates: PORIFERA AND CNIDARIA

About classification: Synapomorphies: shared characters derived from a common ancestor in which the characters originated. The cladist is interested only in homologous characters that are not present in any earlier ancestors; only evolutionary novelties are used to construct cladistic classifications and to infer evolutionary relationships A cladogram shows the least complex, or in other words … Continue reading The invertebrates: PORIFERA AND CNIDARIA

ANIMALS: Invertebrates Introduction notes

Interestingly, no new invertebrate phylum-level body plans have arisen in 600 million years, despite substantial radiation Many invertebrates are aquatic. Water is a good habitat because fertilization can occur in water, as the gametes will not dehydrate gas exchange can be accomplished directly across the general body surface, and body surface moisture does not need … Continue reading ANIMALS: Invertebrates Introduction notes