...................................................
Porifera: Sea Sponges - Origins
FIRST BLOOD: ORIGINS
Generally recognise that the Sea Sponges are the first creatures on Planet Earth after over 4 Billion Yrs of Evolution. They are our primival ancestors as shown by genetic sequencing, lying at the bottom of the Animal Tree.
But it has no muscles, limbs, nervous system or brain. It is but a loose assemblage of Cells and has no definitive shapes but 9000 species have been identified. It lives on the Ocean Floor from the frigid waters of the Poles to the warm Tropics and in freshwater pools.
Sponges may be soft collagens of silica or rigid with calcite spicules embedded in their body. It may be described as a living filtering machine, sucking in water and filtering of food particles (usually bacteria). They are asexual creatures.
Watch the following Clips in sequence to get a better understanding of our evolutionary ancestor, The Porifera
General Introduction
Clip 2 Sponges: You Take My Breath Away
Clip 3 Sponges: A Living Filtering Machine
Cnidaria - Corals, Jellyfish, Stingers
Sea Fan
...............................................................................
A Lithographic Plate by Haeckel (1900) on Art Forms of Nature showing many species of Sea Anemone
Portuguese Man of War
All Cnidaria have specialised cells called Nematocysts ( like a poisonous harpoon) used for capturing prey. May be swimming medusae or sessile polyps. Have a single body cavity for respiration and digestion. Simple net like nervous system. Mostly carnivorous otherwise filter feeders.
Generally produce colonies acting like one single creature. Cnidaria have existed 580 million years ago. There are some 11,000 species identified and counting.
Have a complex life cycle and can reproduce sexually and asexually. Has a distinct larval stage which is planktonic.
Comprise of sea anemones, corals, jellyfish, hydras, sea whips, sea fan and sea pansies (mainly marine)
Clip 1: Learn How the Cnidarians First Evolved
....................................................................
Clip 4: Learn How the JellyFish evolved
Flatworms: Platyhelminthes
Bilaterally symetrical and triploblastic ( 3 fundamental cell layers). Have no body cavity other than the gut and lack an anus. The same pharyngeal opening both takes in food and expel waste.
Breathe by diffusion and have complex life cylces.
Terrestrial faltworm are parasitic while marine flatworms (some 4500 species) are free living.
These were the first Hunters of the Ancient World
...........................................................
Clip 2: Watch How Flatworms Mate
Subscribe to:
Posts (Atom)
.jpg)
