What is/are the threat(s) to coral reefs?

Which of the following structures does this organism possess?  

While wading in the ocean, you look down into the water and notice an umbrella-shaped, translucent animal. It swims by pulsing its body, and long tentacles trail behind it. One of them brushes your leg. Ouch! You feel a burning sensation where it touched you.   To what phylum does this creature probably belong?

This fin labeled is a ______________________ fin.

Intracellular digestion is ___________________________ and is found in  ___________.

The structure labeled is part of the

This dogfish shark pup was nourished by a yolk sac, but not a placenta in the mother’s body.  Therefore, this species is  

These organisms are

Which of the following characteristics do chondrichthyes (sharks, skates and rays) and osteichthyes (bony fish) share?

This organism is an adult tunicate. How can this organism be classified in the Phylum Chordata, given its relatively simple body plan?