Transcript Biology\Sponges & Cnidarians

Kingdom Animalia:
Sponges & Cnidarians
Learning Target Objectives (I can …):
•List characteristics of animals (especially
invertebrates), including their type of symmetry.
•Distinguish between the 3 germ layers and the
structures that develop from them.
•Differentiate between and describe sponge and
cnidarian structures (anatomy) and physiology
(function).
•Compare and contrast sexual and asexual
reproduction in both sponges and cnidarians.
•Give examples of polyp and medusa body forms.
Vocabulary:
Invertebrates * symmetry (spherical, bilateral, radial) *
anterior * posterior * dorsal * ventral * cephalization *
germ layers (ectoderm, mesoderm, endoderm) * sponges *
pores * sessile * osculum * spicules * collar cells *
filter feeding * amebocytes * spongin * budding *
gemmules * regeneration * larva * hermaphrodites *
cnidocytes * coelenterates * radial symmetry * scyphozoa
* anthozoa * hydrozoa * nematocysts * planula * cilia *
basal disks * meiosis
Kingdom Animalia
-all heterotrophic
- all multicellular
- all have a similar embryonic period
- all eukaryotic
- no cell walls
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Invertebrates = animals with NO backbone (95 - 97% of all
animals are invertebrates.)
Some of these are identified by shape (including symmetry).
Symmetry – how body parts are arranged around a point or
central axis
Types of Symmetry:
1) spherical symmetry – ball shaped (may be hollow). Any plane passing
through the center makes similar halves.
2) bilateral symmetry – can be divided in half along 1 line/plane making
each half appear the mirror image of the other.
3) radial symmetry – any plane through its central axis makes mirror
image halves. Ex: cylinders
- most common in animals the don’t move around much or at all Ex:
hydra
Bilaterally symmetrical animals have:
Anterior end – front end or “head” end
Posterior end – hind end or “rear” end
Dorsal surface – top of upper surface
Ventral surface – bottom surface
When nerve tissue and sensory organs are concentrated at
the anterior end, it’s called cephalization.
Most multicellular organisms have a germ layer which
develops & specializes into 3 layers:
1) ectoderm – becomes the outer body covering
2) mesoderm – middle layer, may form inner body linings
(mesentery) and muscles
3) endoderm – innermost layer, forms the gut lining
Phylum Porifera (pore bearer) – Sponges
- pores = holes
- once (sometimes still) used as sponges
- sessile – attach themselves to a surface and don’t move (don’t
relocate). Much like a plant.
This means food has to come to the sponge.
- aquatic (live in water)
Sponge Structure & Function:
- hollow, sac-like body closed at the bottom
- osculum – fairly large opening at the top of the body
- have ectoderm (pinnacoderm) & endoderm and a jellylike substance
(mesoglea) which sometimes contains spicules (spikes) for support &
protection
- No true mesoderm
- collar cells (choanocytes) with flagella
These collar cells line the inside of the body tube. Their
movement draws water & food particles through the small
pores, into the central chamber, and out the osculum.
Food is filtered out by the collar cells. This is called filter
feeding.
Sponges eat mostly bacteria, small algae, and protozoans.
Amebocytes – cells that move like an ameba while carrying
food particles to and waste particles away from other body
cells. (Wastes leave through the osculum.)
Spongin – hard substance that gives sponges a simple
skeleton for support. This is what remains after the sponge
dies. This is what was used as a “sponge” in homes.
Porifera (Sponge) Reproduction
Asexual:
Budding – small growths, “buds,” begin and break off into new
sponges.
Gemmules – special “buds” of food filled amoebocytes that can survive
in harsh environments that may kill the adult sponge. (Dormant stage)
Regeneration – the re-growth of an organism or of its parts into a
complete organism. (Each piece of a cut up sponge can re-grow.)
Sexual:
Sperm enters the pores and is carried by the amoebocytes to an egg.
This forms an immature larva form with flagella so it can swim to a new
location, attach to something, and mature.
Some sponges are hermaphrodites, that means they produce BOTH
eggs & sperm. This does NOT mean they can be self-fertile!
Phylum Cnidaria:
- all live in water, most in salt water
- characterized by cnidocytes, (stinging cells)
- coelenterates (have a hollow gut)
- also have tentacles
Some examples include: sea anemones, corals, jellyfish,
hydra
Cnidarian Body Forms:
Polyp – vase shaped, sessile (doesn’t move),
attach to rocks, etc., mouth points upward.
Medusa – free-swimming, umbrella shape,
mouth points downward
Cnidarian Body Structure:
A) 2 tissue layers:
1) endoderm – inner layer
2) ectoderm – outer layer
(The mesoglea – is a jellylike material between the 2 tissue
layers)
B) tentacles – long, arm-like structures with coiled stingers
inside the cnidocytes (which kill large prey)
The tentacles draw food into the mouth. Waste materials also
exit through the mouth.
* All cnidarians have tentacles surrounding their mouth.
* Cnidarians have radial symmetry.
3 Classes of Cnidarians:
1) Scyphozoa – spend most of life cycle as medusae (Ex:
jellyfish)
2) Anthozoa – live only as polyps (Ex: anemones & coral)
3) Hydrozoa – include organisms that are either medusae or
polyps or alternate between the two.
---------------------------------1) Class Scyphozoa: “cup animals”
- medusa is dominant form
- jellyfish
- nematocysts (coiled stingers) within cnidocytes may contain
deadly poison (Ex: “sea wasp” jellyfish off Australia’s coast)
Jellyfish Reproduction:
Sexual reproduction occurs in the medusa form. Male
jellyfish release sperm and females release eggs into the
water. Fertilization results in a planula that anchors to the
seafloor, etc. (after a short “swim” using cilia). This becomes
a polyp which asexually buds into stacks of medusae which
soon separate and become free swimming.
(Medusa reproduces sexually. Polyp reproduces asexually.)
2) Class Anthozoa: “flower animals”
- polyp form
- includes sea anemones and corals
- basal disks attach polyps to rocks, etc.
Coral:
- live in huge colonies of small polyps
- produce calcium shells that cement together. These remain
behind and form a base for more coral after the polyp dies.
- only live in warm, shallow water
- have symbiotic relationship with algae. Algae lives in coral
cells providing oxygen to coral.
Anemone:
- no shells
- eat fish, etc.
- symbiotic relationship with clown fish
- larger than coral polyps
3) Class Hydrozoa:
- polyps that can move by: a) releasing bubbles at the basal
disk & then floating off, or by b) bending end over end in
somersaults.
- have a nerve net located in the mesoglea
Hydra Reproduction:
- usually asexual “budding” in warm weather
- sexual reproduction in cold, fall weather. Eggs and sperm
are produced by meiosis in ovaries and testes.
The zygote forms a hard cover that protects it
Until spring when it develops into a polyp.
- some are hermaphroditic (both male &
Female reproductive structures)