Lower Invertebrate: Introduction to

Animals

Whats an Animal?

So lets think about this for a second, what really makes an animal an animal?

What differentiates it from a plant, fungi or bacteria?

Are there any grey areas?

Pollination http://www.youtube.com/watch?v=MQiszdkOwuU&feature=related

Moving Art http://www.youtube.com/watch?v=xQXaap6owZE&feature=fvsr

Animal Characteristics Animals are characteristically multicellular heterotrophs

(INGESTION). This process of obtaining food requires the most the most thought, behaviors, responses and techniques. This makes animals more comlex.

whose cells lack cell walls. At some point during their lives, animals are capable of movement (motile). In the most commonly encountered animals, this stage is the adult, although some animals (corals) have sessile (nonmobile) adult phases and mobile juvenile forms.

Animals developed external or internal skeletons to provide support, skin to prevent or lessen water loss, muscles that allowed them to move in search of food, brains and nervous systems for integration of stimuli, and internal digestive systems.

Phylogenetic Tree of Animals

Over the next three chapters we will fly through 9 different phylum of animals in increasing complexities of body plans and life cycles.

Body Break.

Major divisions in the animal kingdom are based on body plans.

Most bodies display some level of symmetry.

Most well known show BILATERAL SYMMETRY, which is where you have a left and right half.

Animals like starfish show more than one plane of symmetry display RADIAL SYMMETRY

Most basic show an asymmetrical body plan

Bilateral vs. Radial

Direction Anterior (Head),

Posterior (Anus).

Dorsal (top), Ventral (bottom).

Lateral (left/right)

RADIAL:

Oral (where openings are located)

Aboral (opposite)

Radial Continued

Lack Cephalization: Aggregation of nerve cells in one region which would define a head.

What are some other examples of organisms that display radial symmetry?

Body Plans: Digestion

Most animals have a body plan best described as a "tube-within-a-tube”or ONE WAY SYSTEM.

This plan calls for two openings: one for food to enter the body (mouth), one for wastes to leave the body (anus). Animals with this plan are more efficient at digesting and absorbing their food than animals with the sac-like body plan.

The one way system plan allows specialization of parts along the tube.

The sac-like body plan has only one opening for both food intake and waste removal. Sac-like body plan animals do not have tissue specialization or development of organs

Refresher of additional terms:

Sessile: no movement: some aquatic animals. Passive feeders

Motile: ability to move and search for food.

Gametes: are sperm (male) and ova (female)

Gametes are haploid (N) half the genetic material, they come together to form Zygotes which are diploid (2N)

Asexual reproduction is rare in animals and only in lower forms.

Vocab Continued Polymorphism: (many forms) possessing more than one

distinct body form (like caterpillars and butterflies) during a life cycle. Often these alternating forms bear little resemblance to each other.

Metamorphism: the process where an organism changes body structures. Many insects undergo this process.

Broadcasters: simple aquatic animals shed gametes into the water like plants do with pollen. Based on timing and location.

hermaphroditic: less motile animals, possess both male and female reproductive organs. Do not self fertilize, released at different times to ensure cross fertilization.

Vid break

Tadpole Trials: http://video.nationalgeographic.com/video/player/animals/amphibians-animals/frogs-and-toads/frog_greentree_lifecycle.html

Phylum Porifera

Sponges: simplest animals.

Generally considered radially symmetrical or asymmetrical

Sessile

Hermaphroditic

Lacking cephalization

Doesn’t sound like much of an animal does it?

General Info: Feeding

Normally anchored in warm ocean water, survive by passing water through their body cavity.

Porifera literally means ‘pore bearing’ or having pores. So they must play a role right?

Pores are INCURRENT OPENINGS: passages ways for water, gases and nutrients to enter the internal cavity.

Openings are formed by PORE CELLS called POROCYTES.

structure

continued

Pore cells can regulate their size to control water flow. Kind of like stoma in a sense.

Water exits the sponge through the EXCURRENT OPENING or OSCULUM.

How does the water ‘flow?’

COLLAR CELLS: line internal cavity and create currents by the movement of flagella.

Cells lining the cavity extract food and oxygen and dispose of cellular wastes

General Info: Structure

Internal skeleton is created by specialized cells called: AMOEBOCYTES.

Secrete salts like calcium carbonate or silicon dioxide to form SPICULES.

Softer ‘bath sponges’ produce SPONGEON FIBRES which are soft and flexible.

Sponge Skeleton Caption: Natural sponge.

Coloured scanning electron micrograph (SEM) showing the branching structure of the body of a natural sponge (phylum porifera). Sponges are primitive aquatic animals that filter food from the water. Their bodies are supported by an internal skeleton of calcium or silicon based spicules (spines), and fibres of the protein spongin. Magnification: x62 when printed 10

centimetres wide.

Reproduction Sponges have a lot of reproductive options:

They are hermaphrodites meaning the have both male and female reproductive organs.

Sperm are produced by Amoebocytes cells.

No self fertilization: BROADCASTERS.

Capable of REGENERATION: chop them off and they grow back.

Asexual Reproduction: GEMMULES spore like structures formed during poor conditions. Sent out with spent water.

Gemmules

Gemmules are internal buds found in sponges that are the result of asexual reproduction, and are a response to a hostile environment.

They are resistant to desiccation (drying out), freezing, and anoxia (lack of oxygen) and can lie around for long periods of time.

These are similar to a bacterium's endospore. Gemmules are made up of amoebocytes surrounded by a layer of spicules and can survive conditions that would kill adult sponges. When the environment becomes less hostile, the gemmule resumes growing.

Final Thoughts

Even though sponges are an animal, they lack true tissues.

They do however have specialized cells.

Cells function individually without intercellular communication.

http://www.youtube.com/watch?v=RmPTM965-1c

http://www.youtube.com/watch?v=BW05vMziy2o&feature=related

Big Q’s

What are the benefits and disadvantages of each type of reproduction for a sponge?

Broadcasting (sexual), Sessile & hermaphroditic, Gemmules (asexual) and regeneration

Would you classify a sponge as more of a plant or more of an animal. Why?

Which seedless or seed plant does it remind you of? What connections do they share?

Summary Table

Cnidarians

Radial Symmetry: Members includes

Hydra

Jellyfish

Portuguese man-o-war

Sea anemones

All united by special cells called nematocysts.

Nematocysts

These are specialized stinging cells, and they’re really fast!

When something in the environment (food) triggers the barb extending from the surface of the nematocyst, the cell collapses and shoots out a protein filament designed to harpoon its prey.

Filaments has a chemical anesthetic which paralyses the food to be ingested.

Nematocysts http://www.youtube.com/watch?v=-Tp38DUjUnM&feature=related

Toxins Jellyfish toxins include a poorly understood array of complex

chemicals.   Many have negative effects on cell membranes and cause them to rupture.  This may, for example, lead to the breaking up of red blood cells, certainly not a desirable response to a sting.  Other toxins have disruptive effects on the action of nerve and muscle cell membranes and impair their normal function.  Throw in toxins that degrade collagen, break down proteins and lipids, and disrupt cellular influx of ions like calcium, and you can see why jellyfish mean business.  

    So behold the amazing nematocyst.  Although small in stature, the combined efforts of multitudes of these microscopic workhorses is sufficient to subdue creatures that seemingly should have no problem against a delicate gelatinous blob.  Nematocysts are one more reason to admire our gelatinous friends, and they are key to the success that jellyfish and their cnidarian relatives have had in conquering all marine habitats.

Video Break

http://www.youtube.com/watch?v=AjM-WOeM3uA

Jellyfish invasion http://www.youtube.com/watch?v=eyCigZ_bsTM&feature=related

Sessile Body Forms

All cnidarians have a sac-like body form

Some are sessile (these are termed POLYPS)

Generally have an elongated body ending in a mouth surrounded by feeding tentacles.

Nematocysts are found on the tentacles.

Motile Forms

When a cnidarian is motile, it is termed a MEDUSA

Very much like an inverted polyp.

Has a bell shaped digestive cavity.

Capable of changing the shape of its bell to propel itself through the water.

Body Walls

Body walls of both forms are constructed out of two tissue layers held apart by a third gel-like layer called the MESOGLEA

It acts as the creatures' structural support in water, as they lack bones or cartilage, endo- or exoskeletons, or similar means of support. Because mesoglea is a gel with such a high water content, these creatures tend to collapse on land

ENDODERM: inner layer specialized to digest prey using enzymes. Surrounds the GASTROVASCULAR CAVITY which acts as the stomach.

ECTODERM: outer layer. Offers some protection from environment but also contains the nematocysts.

More about the Mesoglea

The most interesting layer…debatable.

Random jumble of different cell types

Some cells are nerve like since they conduct messages

Form a NERVE NET since they do not from a centralized system.

Other cells in the Mesoglea become reproductive cells. M&F, remember they’re hermaphrodites.

These cells allow the Cnidarians to respond to their environment. (Ever poked an anemone?)

Class: Hydrozoa

Unity of Tissue, but not shapes

Cnidarians: Extremely diverse in body forms

We’ll Discuss Three Classes of Cnidarians:

Hydrozoans: Generally Sessile Polyps

They are broadcasters, and reproduce asexually by budding.

Portuguese Man-o-War are a well known example

http://www.youtube.com/watch?v=lem0RAVzVCM

Turtle food: http://www.youtube.com/watch?v=Iap6XiO-Wv0&feature=related

Portuguese Man-of-War

Although a member of the phylum Cnidaria, the Portuguese man-of-war is not a "true" jellyfish. These animals consist of a complex colony of individual members, including a float, modified feeding polyps and reproductive medusae.

Physalia typically inhabit the warm waters of the tropics, subtropics and Gulf Stream. Propelled by wind and ocean currents, they sometimes drift into nearshore waters of South Carolina. Though they infrequently visit our coast, swimmers should learn to identify these highly venomous creatures.

The gas-filled float of the man-of-war is purple-blue and can reach lengths of 10 inches. Under the float, tentacles equipped with thousands of nematocysts hang from the feeding polyps extending as much as 30 to 60 feet.

The man-of-war can inflict extremely painful stings. Symptoms include severe shooting pain described as a shock-like sensation, and intense joint and muscle pain. Pain may be accompanied by headaches, shock, collapse, faintness, hysteria, chills, fever, nausea and vomiting.

Class: Scyphozoa

Schyphozoans

Motile with a a medusa body from for most of their lives.

Usually called Jellyfish.

Grouped together because of their POLYMORPHIC life cycles.

Adults are typically male or female.

Gametes are released into the water where fertilization occurs.

Resulting ZYGOTE develops into a larvae which attaches to a surface and becomes a polyp.

Life Cycle of a Cnidarian

Class: Anthozoa

Class Anthozoa

Primarily Sessile Polyps

Have more complex tissues than Schyphozoans and Hydrozoans

Both colonial and solitary examples

Included anemones and coral forming species.

Not Polymorphic.

http://www.youtube.com/watch?v=zkVo-H7bfxs&feature=related

Videos Killer Jelly

http://www.youtube.com/watch?v=NbpB5F9CcLc&feature=related

Box Jellyfish

http://www.youtube.com/watch?v=b6GuAaW9f58

Jelly Fish Life cycle: http://www.youtube.com/watch?v=Id53jmsdxfQ&feature=related

GELATO FISH! http://www.youtube.com/watch?v=ct9KyLmnu0I

Review http://www.brsd.org/education/components/scrapbook/default.php?sectiondetailid=2348