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?

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

• Respiration

• Circulation

• Excretion

• Response

• Movement

• Reproduction

26-1 Introduction to the Animal Kingdom

1. Feeding

• Modes of ingestion of nutrients

Carnivores

Herbivores

Detrivores

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

26-1 Introduction to the Animal Kingdom

Protostome Animals mouth forms from

blastopore (most invertebrates)

Deuterostome Animals anus forms from

blastopore (echinoderms and

vertebrates

Early Embryonic Development

26-1 Introduction to the Animal Kingdom

• Endoderm inner

• Mesoderm middle

• Ectoderm outer

Cells differentiate into 3 germ layers

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 “cross-section” 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:

Anterior: Front

Posterior: Rear End

Ventral: Lower

Dorsal: Upper

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

Body cavity is a fluid-filled space that contains the organs

4. Body Cavity Formation

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 Relationships26-1 Introduction to the Animal Kingdom

26-2 SPONGES

Sponges• Phylum Porifera

• Have tiny openings, or pores, all over their bodies

• Sessile: they live their entire life attached to a single spot

• They are animals. Why…?

26-2 Sponges

Sponges are Animals

• Multicellular

• Heterotrophic

• No cell walls

• Contain a few specialized cells

26-2 Sponges

Click Picture To Watch a 3 Minute Sponge From and Function Video

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

Specialized Cells• spicule

– 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

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Sponge Feeding

• Filter feeders

• Sift microscopic food from the water

• Particles are engulfed by choanocytes that line the body cavity

26-2 Sponges

Click Picture To Watch a 5 Minute Sponge Filter Feeding Video

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

• Sexually or asexually

• A single spore forms both eggs and sperm; usually at different times

26-2 Sponges

Click Picture To Watch A 2 Minute Sponge Reproduction Video

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

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Asexual Reproduction

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• Budding

• Gemmules: groups of archaeocytes surrounded by spicules

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 cross-shaped antennae

• Like a lens or magnifying glass, they focus and direct incoming sunlight

26-2 Sponges

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

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Nematocyst

• A poison-filled, stinging structure that contains a tightly coiled dart

• Found within cnidocytes

26-3 Cnidarians

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

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, bell-shaped body; mouth on the bottom

26-3 Cnidarians

Epidermis

Mesoglea

Gastroderm

Mesoglea

Gastrovascular cavity

Mouth/anus

Tentacles

Tentacles

Mouth/anus

Gastrovascularcavity

Polyp

Medusa

Phylum Cnidarian26-3 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

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Groups of Cnidarians

• Jellies (formerly jellyfishes)

• Hydras and their relatives

• Sea anemones

• Corals

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• Class Scyphozoa: “cup animal”– Jellyfish

26-3 Cnidarians

Groups of Cnidarians

• Spend most of their lives as medusa

• The polyp form is limited to a larva stage

Classes of Cnidarians Class Scyphozoa

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• 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

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Classes of Cnidarians Class Scyphozoa

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26-3 Cnidarians

• Class Hydrozoa: Hydras; Portuguese Man of War

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Groups of Cnidarians

• 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 that keeps the entire colony afloat

• Portuguese Man of War

Classes of Cnidarians Class Hydrozoa

26-3 Cnidarians

• 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

Classes of Cnidarians Class Hydrozoa

26-3 Cnidarians

Click Picture To Watch a 2 Minute Hydra Budding Video

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• Class Anthozoa: “flower animal”– Sea Anemones and Corals

26-3 Cnidarians

Groups of Cnidarians

• Grow only as polyps / no medusa stage

• Central body that is surrounded by tentacles

• Many species are colonial (composed of many individual polyps)

Classes of Cnidarians Class Anthozoa

26-3 Cnidarians

• 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

Classes of Cnidarians Class Anthozoa

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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

Ecology of Corals• The worldwide distribution is determined by:

– Temperature

– Water depth

– Light intensity

• Many suffer from human activity• Coral bleaching has become common • Global warming may add to the problem

26-3 Cnidarians

Click Picture To Watch a 5 Minute Coral Spawn Video