Animals Chapter 2
Sponges, Cnidarians, and Worms
Sections 1 and 2
Definitions
• Nerves – carry signals throughout the
body
• Ganglia – groups of nerves bundled
together. Animals can have a brain and
ganglia or just have ganglia depending on
how advanced the animal is
• Gut – pouch lined with digestive enzymes
• Coelom – cavity that allows organs such as
the gut, heart etc to work without
interference from body movement
Sponges
• Phylum Porifera
• 1st animals on earth
Coelom
Ganglion
Symmetry
Phylum Porifera
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Simplest of all animals
Asymmetrical
No head, nervous system, gut or coelom
Spicules are needle-like splinters that make up
the skeleton
• If cells are separated, they can come back
together
• Both asexual and sexual reproduction
Sponge Anatomy
• Pores - used to pump water into
sponge
• Collar Cells – filters particles of food
from water and digests them
• Osculum – hole at the top of the
sponge
Anatomy of a Sponge
Cnidarians
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Jellyfish
Hydra
Sea anenome
corals
Phylum Cnidaria
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Radial symmetry
Complex tissues
Gut
Nerve net and nerve ring in medusa form
If cells get separated, they come back together
Tentacles – covered with nematocysts
Nematocysts – stinging cells
Sexual and asexual reproduction
Body Forms
• Medusa – free
swimming, mushroom
shaped
• Polyp – vase shaped,
attached to a surface
• Most spend life as
polyps but some are
born polyps and turn
into medusas
Worms
• Three different phyla
– Platyhelminthes – aka flatworms
– Nematoda – aka roundworms
– Annelida – aka segmented worms
Flatworms Platyhelmenthes
• Planaria
• Flukes
• Tapeworms
Characteristics
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Bilateral symmetry
Nervous system
Ganglia acts as a brain
Sensory lobes to detect light and food
Planaria have a gut
Fluke and tapeworms are parasites and
have no gut
Reproduction of Fluke
Reproduction of
Tapeworms
• Sexual
• Can go from uncooked meat to human
Roundworms - Nematoda
Roundworm
• Pseudocoelom – tube within a tube
• Bilateral symmetry
• Can pick up through the soles of
feet, through dirty hands, through
some foods
Segmented Worms Annelida
• Includes earthworms, bristle worms
and leeches
• Can live in water or on land
Earthworms, Bristle
Worms, Leeches
Earthworms – aerate soil (makes
tunnels) to allow water and air in,
break down organic matter into
elements that can be used
Bristle Worms – all live in water
Leeches – can be scavengers, predators
or parasites, and can be used in
medicine
Next…
• Earthworm dissection
• Earthworm questions powerpoint
Mollusks
• Phylum Mollusca
• Soft bodied usually with a shell or
shells
• Three classes:
• Gastropods – snails and slugs
• Bivalves – 2 shells- clams, mussels,
etc.
• Cephalopods – squid and octopus
Similarities Between
Mollusks
Feeding
• Different depending on species:
• Gastropods have a radula which is
like a really rough tongue and scraps
algae, leaves etc.
• Bivalves filter feed
• Cephalopods use tentacles to grab
prey
Circulatory System
• Most mollusks have an open system
• Open system - A simple heart pumps
blood into sinuses
• Cephalopods have a closed system
• Closed system – blood is circulated
through a closed loop
Brains
• Most mollusks have ganglia spread
throughout their body
• Cephalopods have a brain where all of
the ganglia are connected
Next
• Squid Dissection