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Chapter 26: Sponges and Cnidarians
26-1 Introduction to the Animal Kingdom
What makes animals different
from the previous organisms we
have covered so far this year?
26-1 Introduction to the Animal Kingdom
The Animal Kingdom
• Multicellular
• Eukaryotic
• Heterotrophs
• Cells lack
cell walls
• 95% are
invertebrates
26-1 Introduction to
the Animal Kingdom
26-1 Introduction to the Animal Kingdom
26-1 Introduction to the Animal Kingdom
What Animals Do to Survive
• Feeding
• Response
• Respiration
• Movement
• Circulation
• Reproduction
• Excretion
26-1 Introduction to the Animal Kingdom
1. Feeding
• Modes of ingestion of nutrients
Carnivores
Detrivores
Herbivores
26-1 Introduction to the Animal Kingdom
2. Respiration
• Taking in oxygen, releasing carbon dioxide
Lungs
Gills
Skin
26-1 Introduction to the Animal Kingdom
3. Circulation
• Movement of materials in the body
Heart Pump
Diffusion
26-1 Introduction to the Animal Kingdom
4. Excretion
• Removal of nitrogen waste out of body to
maintain homeostasis
Diffusion
Kidney
26-1 Introduction to the Animal Kingdom
5. Response
• Responding to outside stimuli using nerve cells
26-1 Introduction to the Animal Kingdom
6. Movement
• Attached to a single spot or motile
26-1 Introduction to the Animal Kingdom
7. Reproduction
26-1 Introduction to the Animal Kingdom
Trends in Animal Evolution
Though there are differences in whether an
animal has a backbone or not, there are
some common trends:
1. Cell Specialization
2. Body Symmetry
3. Cephalization
4. Body Cavity Formation
26-1 Introduction to the Animal Kingdom
1. Cell Specialization
• Animal cells have evolved to carry out
specific functions:
26-1 Introduction to the Animal Kingdom
1. Cell Specialization
•
Reasons why cell specialization is
important:
•
Allows for animals to perform many different
functions
•
Causes a greater efficiency in survival
26-1 Introduction to the Animal Kingdom
Early Embryonic Development
•
Animals that reproduce sexually begin life
after fertilization as a zygote (fertilized egg)
•
Zygote undergoes a series of divisions
•
Blastula forms (simple ball of cells)
•
Blastula fold in on itself forming blastopore
•
Blastopore leads into a central tube
26-1 Introduction to the Animal Kingdom
Early Embryonic Development
26-1 Introduction to the Animal Kingdom
Protostome Animals
mouth forms from
blastopore
(most invertebrates)
Deuterostome Animals
anus forms from
blastopore
(echinoderms and
vertebrates
26-1 Introduction to the Animal Kingdom
Early Embryonic Development
Cells differentiate into 3 germ layers
•
Endoderm
inner
•
Mesoderm
middle
•
Ectoderm
outer
26-1 Introduction to the Animal Kingdom
Early Embryonic Development
26-1 Introduction to the Animal Kingdom
2. Body Symmetry
• Ability to divide a body into 2 equal halves
26-1 Introduction to the Animal Kingdom
2. Body Symmetry
• Planes of symmetry: Dorsovental Axis
(Sagittal Plane)
• Cuts the body
into right and left
sides
26-1 Introduction to the Animal Kingdom
2. Body Symmetry
• Planes of symmetry: Transverse Axis
•Produces a “crosssection” of the body
• Divides the body
into “Anterior” and
“Posterior” regions
26-1 Introduction to the Animal Kingdom
2. Body Symmetry
• Regions of the body:
Dorsal:
Upper
Posterior:
Rear End
Anterior:
Front
Ventral:
Lower
26-1 Introduction to the Animal Kingdom
Trends of Evolution
There are two more characteristics that most
animals share in addition to “Cell
Specialization” and “Body Symmetry”
3. Cephalization
4. Body Cavity Formation
26-1 Introduction to the Animal Kingdom
3. Cephalization
Refers to the
characteristic that
more sense organs and
nerve cells are located
at the anterior part of
the body than
anywhere else
26-1 Introduction to the Animal Kingdom
3. Cephalization
Allows animals to
respond quicker and in
more complex ways to
stimuli
26-1 Introduction to the Animal Kingdom
4. Body Cavity Formation
Body cavity is a fluidfilled space that
contains the organs
26-1 Introduction to the Animal Kingdom
4. Body Cavity Formation
This allows space for
internal organs to keep
their shape and to
grow properly
26-1 Introduction to the Animal Kingdom
Evolutionary Relationships
26-2 SPONGES
26-2 Sponges
Sponges
• Phylum Porifera
• Have tiny openings, or pores,
over their bodies
• Sessile: they live their entire life
attached to a single spot
• They are animals. Why…?
all
26-2 Sponges
Sponges are Animals
• Multicellular
• Heterotrophic
• No cell walls
• Contain a few
specialized cells
Click Picture To Watch a 3 Minute
Sponge From and Function Video
26-2 Sponges
Form and Function in Sponges
• Have nothing resembling a
mouth or gut
• Have no tissues or organ
systems
• Simple functions are carried
out by a few specialized cells
26-2 Sponges
Asymmetrical
• Have no front or back ends,
no left and right sides
• A large, cylindrical water
pump
• The body forms a wall
around a large central cavity
through which water flows
continually
26-2 Sponges
26-2 Sponges
Specialized Cells
• Choanocytes
– Specialized cells that use flagella to move a
steady current of water through the sponge
• Osculum
– Water leaves through the large
hole at the top of the sponge
26-2 Sponges
Choanocytes
• Specialized cells that
use flagella to move a
steady current of water
through the sponge
• Filters several thousand
liters/day
26-2 Sponges
Osculum
• A large hole at the top of
the sponge, through which
water exits
• The movement of water
provides a simple
mechanism for feeding,
respiration, circulation and
excretion
26-2 Sponges
• spicule
Specialized Cells
– is a spike-shaped structure made of chalklike
calcium carbonate or glasslike silica
• archaeocytes
– are specialized cells that move around within
the walls of the sponge and make spicules.
• spongin
– network of flexible protein fibers that make up
the internal skeleton of a sponge.
26-2 Sponges
Simple Skeleton
• Spicule: a spike-shaped
structure made of
chalk-like calcium
carbonate or glasslike
silica in hard sponges
• Archaeocytes:
specialized cells that
make spicules
26-2 Sponges
26-2 Sponges
Sponge Feeding
• Filter feeders
Click Picture To Watch a 5 Minute
Sponge Filter Feeding Video
• Sift microscopic
food from the water
• Particles are engulfed by
choanocytes that line the body cavity
26-2 Sponges
Respiration, Circulation, & Excretion
• Rely on the movement of water through their bodies
to carry out body functions
• As water moves through the cavity:
• Oxygen dissolved in the water diffuses into the
surrounding cells
• Carbon dioxide and other wastes, diffuse into the
water and are carried away
26-2 Sponges
Response
• No nervous system
• Many sponges protect
themselves by producing
toxins that make them
unpalatable or poisonous
to potential predators
26-2 Sponges
Reproduction
Click Picture To Watch A 2 Minute
Sponge Reproduction Video
• Sexually or asexually
• A single spore forms
both eggs and sperm;
usually at different
times
26-2 Sponges
Sexual Reproduction
• Internal fertilization:
Eggs are fertilized inside
the sponge’s body
• Sperm are released from
one sponge and carried
by currents to the pores
of another sponge
26-2 Sponges
Asexual Reproduction
• Budding
• Gemmules: groups of
archaeocytes surrounded
by spicules
26-2 Sponges
Ecology of Sponges
• Ideal habitats for marine animals such as snails,
sea stars, sea cucumbers, and shrimp
• Mutually beneficial relationships with bacteria,
algae and plant-like protists
– Many are green due to these organisms living in
their tissues
26-2 Sponges
Ecology of Sponges
• Attached to the seafloor and may receive
little sunlight
• Some have spicules that look like crossshaped antennae
• Like a lens or magnifying glass, they focus
and direct incoming sunlight
26-3 CNIDARIANS
26-3 Cnidarians
Cnidarians
• Phylum Cnidaria
• Hydras, jellies,
sea anemones, and corals
• Soft-bodied
• Carnivorous
• Stinging tentacles arranged in circles around their mouths
• Simplest animals to have body symmetry and specialized cells
26-3 Cnidarians
Cnidocytes
• Stinging cells that
are located on their
tentacles
• Used for defense
and to capture prey
26-3 Cnidarians
Nematocyst
• A poison-filled, stinging
structure that contains a
tightly coiled dart
• Found within cnidocytes
26-3 Cnidarians
Click Picture To Watch a 2 Minute Feeding Anemone Video
26-3 Cnidarians
Click Picture To Watch a 3 Minute Stinging Jellyfish Video
26-3 Cnidarians
Form and Function in Cnidarians
• Only a few cells thick
• Simple body systems
• Most of their responses to the environment
are carried out by specialized cells and
tissues
26-3 Cnidarians
Radially Symmetrical
• Central mouth
surrounded by
numerous tentacles
that extend outward
from the body
• Life cycles includes
a polyp and a
medusa stage
26-3 Cnidarians
Body Plan
• Polyp: cylindrical
body with arm-like
tentacles; mouth
points upward
• Medusa: motile, bellshaped body; mouth
on the bottom
26-3 Cnidarians
Phylum Cnidarian
Epidermis
Mesoglea
Gastroderm
Tentacles
Mesoglea
Gastrovascular cavity
Mouth/anus
Mouth/anus
Gastrovascular
cavity
Tentacles
Medusa
Polyp
26-3 Cnidarians
Feeding
• Polyps and medusas have a body wall that
surrounds an internal space: the
gastrovascular cavity
• Gastrovascular cavity: a digestive chamber
with one opening
– Food enters and wastes leave the body
26-3 Cnidarians
Respiration, Circulation, & Excretion
• Following digestion, nutrients are usually
transported throughout the body by
diffusion
• Respire and
eliminate wastes
by diffusion
through body walls
26-3 Cnidarians
Response
• Specialized sensory cells are used to gather
information from the environment
• Nerve net: loosely organized network of nerve cells
that together allow cnidarians to detect stimuli
– Distributed uniformly throughout the body in most species
– In some species it is concentrated around the mouth or in
rings around the body
26-3 Cnidarians
26-3 Cnidarians
Response
• Statocysts: groups of
sensory cells that help
determine the direction
of gravity
• Ocelli: eyespots made
of cells that detect light
26-3 Cnidarians
Movement
• Hydrostatic skeleton: a layer of circular
muscles and a layer of longitudinal muscles
that enable cnidarians to move
26-3 Cnidarians
Reproduction: Sexually and Asexually
• Polyps can reproduce asexually by budding
• External sexual reproduction
– The sexes are separate-each individual is either
male or female
– Both egg and sperm are released into the water
26-3 Cnidarians
26-3 Cnidarians
26-3 Cnidarians
26-3 Cnidarians
Groups of Cnidarians
• Jellies (formerly jellyfishes)
• Hydras and their relatives
• Sea anemones
• Corals
26-3 Cnidarians
26-3 Cnidarians
Groups of Cnidarians
• Class Scyphozoa: “cup animal”
– Jellyfish
26-3 Cnidarians
Classes of Cnidarians
Class Scyphozoa
• Spend most of their lives as medusa
• The polyp form is limited to a larva stage
26-3 Cnidarians
Classes of Cnidarians
Class Scyphozoa
• The largest jellyfish ever found is 4 meters
in diameter with tentacles more than 30
meters in length
• Most species are harmless, many can cause
servere allergic reactions/even kill people
26-3 Cnidarians
26-3 Cnidarians
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Groups of Cnidarians
• Class Hydrozoa: Hydras; Portuguese Man of
War
26-3 Cnidarians
Classes of Cnidarians Class Hydrozoa
• The polyps of most hydrozoans grow in
branching colonies that sometimes extend
more than a meter.
• Within a colony, the polyps are specialized to
perform different functions.
• EX: One polyp forms a balloon-like float
keeps the entire colony afloat
• Portuguese Man of War
that
26-3 Cnidarians
Classes of Cnidarians
Class Hydrozoa
• Most common in freshwater hydrozoan is a
hydra
• Lack medusa stage (solitary polyp)
• Reproduce sexually (producing eggs and
sperm in the body wall)
and asexually (budding)
• a few species
are hermaphroditic
Click Picture To Watch a 2 Minute Hydra Budding Video
26-3 Cnidarians
26-3 Cnidarians
Groups of Cnidarians
• Class Anthozoa: “flower animal”
– Sea Anemones and Corals
26-3 Cnidarians
Classes of Cnidarians
Class Anthozoa
• Grow only as polyps / no medusa stage
• Central body that is surrounded by tentacles
• Many species are colonial (composed of
many individual polyps)
26-3 Cnidarians
Classes of Cnidarians
Class Anthozoa
• Corals and sea anemones reproduce
sexually by producing free swimming
larvae
• The free swimming larvae attach to rocks
and then form polyps
• Also can reproduce by budding
26-3 Cnidarians
Classes of Cnidarians
Class Anthozoa
• Forming Coral Reefs
– Formed when hard coral from layers of
skeleton (CaCO3)
– Algae forms a sybiotic relationship with coral
26-3 Cnidarians
Click Picture To Watch a 1 Minute Coral Budding Video
26-3 Cnidarians
26-3 Cnidarians
Ecology of Corals
• The worldwide distribution is determined by:
– Temperature
– Water depth
– Light intensity
Click Picture To Watch a 5 Minute Coral Spawn Video
• Many suffer from human activity
• Coral bleaching has become common
• Global warming may add to the problem