Today in class we talked about the very basic animals that are on our Earth -- Sponges and Cnidarians. We discussed their body structure, how they reproduce, and what cells are important for them to obtain food. Below is the information that was written on the board along with some interesting links about these primitive water creatures.
SPONGES
Sponges have a few things that are important when talking about their body
structure.
- They are invertebrates
- They are asymmetrical (have no symmetry)
- They have no tissue or organs within their bodies
- They have spikes that support their bodies while providing protection against
predators
The cell type that traps food is called the collar cell.
Pores on a sponge allow water and food to travel into the central cavity of the
sponge.
Sponges reproduce both asexually and sexually. Asexual reproduction is called
budding while sexual reproduction is called fertilization.
Here is a cool video displaying some sponges during reproduction
CNIDARIANS
Polyp
Medusa
Body Structure
Cnidarians unlike sponges have two body types - polyp and medusa. Polyp are vase-like structures that are attached to the bottom of the sea floor while the medusa has adapted to life in the ocean and can swim/float around. Medusas looks like an over-turned bowl. Cnidarians are invertebrates and have radial symmetry.
There stinging cells are the cells that trap their food.
Cnidarians reproduce both asexually and sexually. Their life cycle is a bit odd in that a medusa will release sperm and another medusa will release an egg. Once fertilization has occurred, the larva will settle and become a polyp. That polyp will asexually reproduce and pulling apart will occur where many disc-shaped structure break away from the polyp and overtime they mature into an adult medusa.
Here is a video of a Giant Green Anemone (polyp) Feeding at Monterey Bay Aquarium
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