Transcript porifera and cnidaria

PORIFERA AND
CNIDARIA: THE
SIMPLEST
INVERTEBRATES
What characteristics do all
invertebrates have in common?
the
1) They don't have a
backbone.
spinal column or
2) Some, like worms or jellyfish, have no
skeleton. Others, like insects or spiders, have an
external skeleton or exoskeleton.
Invertebrates include 95% of all animal species.
The most important groups of invertebrates are:
- Porifera: Sponges.
- Cnidaria: Jellyfish, Corals, Sea Anemones and Hydras.
- Worms.
- Molluscs: Squids, Mussels, Oysters, Slugs, Snails...
- Arthropods: Lobsters, Crabs, Centipedes, Scolopendras,
Spiders, Scorpions, Butterflies, Ants, Bees, Wasps...
- Echinoderms: Sea Urchins, Starfish, Sea Cucumbers...
PORIFERA
Sponges belong to this group.
They live in the sea.
Sponges do not move around; they are attached to the sea bed.
PORIFERA: BODY
- Their body shape is like a sac.
- Their bodies are full of pores and channels, so water circulates in and
out of them.
- They feed by filtration: water enters through the central cavity,
deposits nutrients, and leaves through a hole called the osculum. The
nutrients are trapped by choanocytes, special cells with flagella wich
line the interior of the sponge.
Choanocyte
Water
exits
Osculum
Central
cavity
Pores and
channels
Water
enters
PORIFERA: FUNCTIONS
Sponges do not have distinct circulatory, respiratory, digestive, and
excretory systems. Instead, the water flow system supports all these
functions.
They can reproduce both asexually (by budding) and sexually (most
of them are hermaphrodites).
Sponges have the capacity to regenerate damaged or lost parts, and
even a complete adult from fragments.
CNIDARIA
Jellyfish, corals, sea anemones and hydras belong to this group.
Jellyfish
Coral
Sea anemone
Hydra
Most of them live in the sea, except hydras, which live in fresh water.
They can both live alone or in colonies.
Jellyfish can float; corals and sea anemones live fixed to the sea bed.
CNIDARIA: BODY
They have radial symmetry.
They have a soft body, with only one opening, the mouth/anus, which
is surrounded by tentacles.
Their tentacles have a lot of cnidocytes, venomous cells which allow
them to catch prey and defend themselves from predators. This is
responsible for the stings delivered by jellyfish.
They also have a gastrovascular cavity, something like a stomach,
connected to the mouth/anus.
Cnidarians have two forms:
- Polyps: They are approximately cylindrical in shape (like a sac). The
mouth and the tentacles are at the upper end of their body. They live
attached to the substrate.
- Jellyfish: Their body shape is like an umbrella. The mouth and the
tentacles are located on the lower surface. They float.
CNIDARIA:
FUNCTIONS.
- Nutrition: Cnidaria are carnivorous: they use their tentacles to capture
prey.
- Interaction: They respond to various types of stimulus, such as odors.
Jellyfish also can detect the direction from which light is coming and so
their own position.
- Reproduction: Polyps reproduce asexually by budding. Jellyfish
reproduce sexually. Sometimes, cnidaria have a complex life cycle with
both polyp and medusa stages
CAN YOU DESCRIBE THE FOLLOWING LIVING BEINGS?
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