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SPONGES AND
CNIDARIANS
BIOLOGY 112
SPONGES
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Phylum Porifera
Multicellular and heterotrophic
No cell wall and few specialized cells
Live their entire life attached to a surface
They eat by sifting microscopic food in water
• Choanocytes are specialized structures that help move
water through their body cavity
• Water enters through pores and leaves through the osculum
(a large hole at the top of the cavity)
GETTING EVERYTHING IT NEEDS
• Digestion is
intracellular
• Takes place inside
the cells
• Not only is food
provided using this
sifting action but
also everything for
respiration,
circulation and
excretion
SPONGES AND REPRODUCTION
• Reproduce sexually and asexually
• Sexually
• Eggs are fertilized internally
• Zygote develops into a larva
• Larva is the immature stage of the organism that looks
different from the adult
• They are motile
• Carried by the ocean to the floor and grow into an adult
sponge
• Asexually
• By budding
CNIDARIANS
• Phylum Cnidaria
• Soft-bodied carnivores that have stinging tentacles
arranged in circles around their mouth
• Simplest animals that have body symmetry and
specialized tissues
• Exhibit radial symmetry
• Central mouth with several tentacles
TWO DISTINCT LIFE STAGES
• Polyp
• Cylindrical body with
arm-like tentacles and
usually do not move
• Lives attached to the
surface with its mouth
pointing upward
• Medusa
• Bell-shaped body with
a mouth at the bottom
• Free swimming
CNIDARIANS AND DIGESTION
• Possess a gastrovascular cavity
• Digestive chamber with one opening
• Foods and wastes enter and leave this opening
• Nutrients are transported throughout body by
diffusion
• Oxygen and wastes are diffused through the body
walls
CNIDARIANS AND RESPONSE TO
STIMULI
• Gather information
from their
environment using
specialized sensory
cells
• nerve nets
• a network of nerve
cells that together let
cnidarians detect
stimuli
CNIDARIANS AND BODY STRUCTURE
• Possess a
hydrostatic skeleton
• Consists of layers of
circular muscles as
well as longitudinal
muscles that, with
the digestive cavity,
allow it to move
CNIDARIANS AND REPRODUCTION
• Asexual – by budding
• Sexual – external fertilization in water
CLASSIFICATION OF CNIDARIANS
• Jellyfish
• Live mostly as medusas
• Hydras
• Grow in branching colonies
• Ex. Portuguese man-of-war
• Sea Anemones and Corals
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Only have a polyp stage
Colonial
Polyps grow together in large numbers
Secrete an underlying skeleton of calcium carbonate
Form coral reefs
PORTUGUESE MAN-OF-WAR
CORAL REEFS