COMPARISON BETWEEN PORIFERA AND CNIDARIA. Colwyn Sleep

Transcription

1 COMPARISON BETWEEN PORIFERA AND CNIDARIA Colwyn Sleep

2 INTRODUCTION Porifera Cnidaria Porifera and Cnidaria are organisms which share similar characteristics with one another. -They are both multicellular, they consist of many cells working together. They are both eukaryotic, they have DNA in the form of chromosomes contained within a distinct nucleus. -They are both heterotrophic, they ingest other organic material. -They also can both be found in similar marine environments (with the exception of a few freshwater species.)

3 GENERAL CHARACTERISTICS Porifera Sponges, or The Pore Bearers are among the oldest multicellular species, with fossils dating back over 600 million years ago. They are made up of over 9000 different species and can range in size from 0.5cm tall to 2m tall. Cnidaria This phylum includes animals such as coral, jellyfish, coral, and hydroids. The name Cnidae refers to their stinging nettles Cnidaria are classified as a more complex phylum than porifera.

4 SHAPE CHARACTERISTICS Porifera are asymmetrical meaning there is no symmetry in their body structure. This is due to the fact that they have no true mesoderm or a body plan. Cnidarians are either vase shaped or bell shaped and have radial symmetry (producing two equal parts if cut longitudinally) Cnidarians range in size from as small as a 0.5cm tall bell up to a 2.4 m diameter with tentacles ranging upwards of 50 meters.

5 NERVOUS SYSTEM Porifera do not have any form of nervous system but their individual cells have the ability to sense and react to stimuli in the environment. Cnidaria have simple nervous system called a nerve net. These nerve cells react to the presence of food and danger for the purposes of feeding and protection.

6 MOVEMENT Porifera are only motile in their laval form. The mature form is sessile (non-moving) which is one of the main reasons for these animals being originally classified as plants. Although they lack a true muscular system, cnidarians are able to move using specialized cells that can contract and relax (eg. in the tentacles)

7 RESPIRATION METHOD AND STRUCTURES Porifera do not have a true respiratory system. Gas exchanges directly between cells and water by diffusion (O2 diffuses into and CO2 out of cells). Water enters via tiny pores called ostia, incurrent. Water exits via a massive pore, osculum, excurrent. Cnidaria do not have a true respiratory system. Gas exchanges directly between cells and water by diffusion (O2 diffuses into and CO2 out of cells) both across epidermis and gastrovascular tissues

8 EXCRETION METHOD AND STRUCTURES Porifera do not have a true excretory system. They have specialized cells, amebocytes, which help remove waste from other cells in the sponge, or cells release waste directly to water. Wastes are then carried away out of the osculum by water currents. Water enter via ostia, incurrent. Water exits via osculum, excurrent. Cnidaria do not have a true excretory system. Their waste diffuses from cells into gastrovascular cavity and is then released through the mouth

9 FEEDING METHOD AND STRUCTURES Porifera are filter-feeders meaning their food enters with water and they filter the food out. Water enters via tiny pores, ostia, incurrent. Water exits via massive pore,osculum, excurrent. Collar cells (choanocytes) engulf and digest the food. Many Cnidarians are carnivorous predators. They capture small animals using their nematocysts (stinging cells). They then use their tentacles to push food through their mouth into their gastrovascular cavity

10 DIGESTION METHODS AND STUCTURES Digestion in sponges occurs when the flagella of choanocytes draws water through the holes in the body wall, then expels it through the osculum. Here, specialized collar cells trap food particles and digest them, or pass them on to an ameboid-like cell for digestion and circulation Cnidarians do not have a true digestive system. Food enters their gastrovascular cavity via mouth and extracellular digestion enzymes are secreted into their gastrovascular cavity. Cells lining the cavity absorb the digested nutrients and smaller food particles.

11 REPRODUCTION Asexual and sexual reproduction both occur in sponges. Asexual reproduction occurs by fragmentation or budding. In fragmentation, a piece breaks off and forms a separate animal. In budding, the animal reproduces by growing a second sponge from the side of the parent that eventually detaches. In sexual reproduction, an egg and sperm combine to form a flagellated zygote which swims to a new location. Reproduction in cnidarians takes place sexually or asexually by budding.

12 LIFE CYCLE The first stage of life for a porifera is as a free swimming larvae. Once attached to a solid object such as a rock, the larvae can grow into a young, and eventually mature sponge. Cnidarians alternate between medusa and polyp forms in their life cycle.

13 SURPRISING FACTS -Porifera skeletons were once used as a washing sponge before synthetic sponges became common. -The bath sponge actually received its name from the animal. -Sponge Reefs were thought to be abundant during the Jurassic period 200 million years ago. -One cubic centimetre of sponge can filter more than 20L water per day -Cnidarians have a single external opening that serves as both the mouth and the anus -Cnidarians such as the Box Jellyfish are among the most deadly creatures on earth. The Box jellyfish sting will cause death in a matter of minutes.

14 BIBLIOGRAPHY