Earthworm Dissection

Worms are in three phyla: Annelida, Nematoda and Platyhelminthes

Earthworms are in one phyla: Annelida





Annelida- coelum

Nematoda- A cavity between the digestive tract and the body wall. It develops from the blastocoel and is called a pseudocoel

Platyhelminthes- bilateral

Clitellum- The clitellum secretes a mucus which helps keep the worms together when exchanging sperm (copulation). The clitellum eventually slides off and is a cocoon for the new worms.

Oviducts- Where the eggs are stored.

Prostomium- It covers the mouth and is used to dig through the soil.

Seminal Receptacles- Sperm that is received is stored here.

Seminal Vesicles- Sperm is made here.

Setae- Small bristles that help the earthworm move by providing traction.

Nephridium- Removes metabolic wastes.

Crop- After food comes through the esophagus it passes through here. Food can be stored here before it passes through the digestive tract.

Gizzard- Food is ground down in here so it can be digested.

Septa- Thread like structures that hold the skin to the organs and separtate the segments.

http://www.angelfire.com/de2/atoy/rep.htm

http://www.britannica.com/EBchecked/topic/121884/clitellum

http://en.wikipedia.org/wiki/Nephridium

http://www.backyardnature.net/earthwrm.htm
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/Invertebrates.html#Platyhelminthes

Hydra: Phylum Cnideria



The diagram below will help you locate the bud, basal disc and tentacles on this hydra

  Some information is from the red book (Animals without backbones, pg. 81)

http://en.wikipedia.org/wiki/Hydra_(genus)
http://www.madsci.org/posts/archives/2000-11/973856032.Zo.r.html

Morphology- At one end of a hydra is a adhesive foot which is called the basal disc. At the other end is the mouth and one to twelve tentacles (cnidae). Each tentacle has cnidocytes (stinging cells) which containg nematocysts that shoot out a paralysing dart like thread when a little trigger hair (cnidocil) comes in contact with prey. The hydra has two main body layers (epidermis and gastrodermis) that are separated by a gel-like substance (mesoglea). Respiration and excretion occur by diffusion in the epidermis layer.

Habitat- Unpolluted fresh water lakes, streams and ponds in temperate and rainforest areas.

Movement- The simplest movement is by gliding (ameboid movement by basal cells) yet the fastest method looks somewhat like somersaulting. The tentacles attach to the bottom (adhesive thread capsules), the base is "thrown" over, the base attachs to the bottom again, the tentacles release and this whole procedure is repeated.



A Somersaulting Hydra



On this hydra there are 6 tentactles
that help it eat and move.





Eating- The tentacles stretch out and when one comes in contact with prey it paralyses it. The tentacles wrap around the prey and slowly bring it to the mouth. Digestive enzymes are released to break down the food and then phagocytosis occurs to engulf the bits of food.

Land Lubber Grasshopper Dissection

http://www.google.ca/searchhl=en&pwst=1&rlz=1R2GGIE_en&defl=en&q=define:Cephalization&sa=X&ei=4ZwSTeS_OZC-sQOsqtS6Ag&ved=0CBUQkAE

• Grasshoppers are from the phylum Arthropodia and the class Insecta
• Cephalization - over many generations, the nervous tissue becomes concentrated towards one end of an organism. In this case the nervous tissue of a land lubber grasshopper has cephalized toward the anterier end, making sensory organs (eyes and antennae).
•  Eyes ( http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CompoundEye.html , http://en.wikipedia.org/wiki/Simple_eyes_in_invertebrates )

- Two huge compound eyes that have many ommatidia on them (each one is a visual receptor). Each ommatidium consists of a lens (single facet), a crystalline cone, light-sensitive visual cells (arranged in radial pattern and pigment cells (separate the ommatidium). The compound eye is great at detecting movement. The compound eye can also respond to ultraviolet light (we can't see this light).



A diagram of a compound eye. You can slightly see the
ommatidium on the eye in the picture to the left.





Compound eyes and antenanae
are a result of cephalization







.

- Three small simple eyes (dorsal ocelli) that consist of a cornea (lens) and a layer of photoreceptors (rod cells). The ocelli are far more sensitive to light. The diagram below shows where on a grasshopper head the ocelli are located.

• Mouth ( http://en.wikipedia.org/wiki/Insect_mouthparts )

A Diagram of the Grasshopper Mouthparts

- Mandibles - crush, tear, cut and chew food  

- Maxillae - manipulate food during mastication (chewing)

- Maxillary and Labial Palps - sensory receptors for sensing characteristics of food

- Labium - the floor of the mouth, assists chewing

- Hypopharynx - assists swallowing

- Labrum - upper lip

• Thorax ( http://www.biologyjunction.com/grasshopper_dissection.htm , http://wiki.answers.com/Q/Function_of_spiracles_in_grasshopper )

- Two wings - the outer wings protect the flying wings

The Bottom wing is the protecting wing

- Legs - The first two pairs are for walking and the last pair is for jumping. You can see the different legs in the photo below.

 

A jumping leg from a land lubber grasshopper. This is an example of a jointed appendage.

• Abdomen

- Spiracles - used for respiration. Oxygen comes in and is filtered by tracheae, it is distributed among the cells and then carbon dioxide it taken out.

- Difference between male and female - a female grasshopper has a ovipositor. A comparison is shown in the diagram below.



If you compare this picture with the diagram to the right, you can see that our grashopper is a male.

Locomotion and Embryology

How different Invertabrates move

As you work your way up the tree, locomotion gets more complex.
The paragraphs below explain the different animal movements in each phylum.

Arthropoda

http://en.wikipedia.org/wiki/Arthropod

http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=A1ARTA0000336

Arthropods have jointed appendages that they use to sense, walk, feed and mate. They can do this by flexing one body segment after the other (relaxation and contraction of striated muscle fibres). The appendages can be either biramous (branches into two and each branch has a series of segments attached end to end) or uniramous (single series of segments attached end to end).Some examples are crabs, insects, lice, shrimp, spiders and scorpions.

The following photos show how in the phylum Arthropodia, jointed appendages are very complex and they help the organism do many different thing

Mollusca

http://en.wikipedia.org/wiki/Mollusca

The under side of Mollusks consists of a muscular foot which can do different things in different classes. It contains statocysts (balance sensors), it can secrete mucus (lubricant), the foot can suction, it can burrow and it is capable of jet propulsion. Some examples are snails, slugs, octopus, oysters, and squids.

Annelida

http://en.wikipedia.org/wiki/Annelid

There are many ways that annelids move. Some move by peristalsis (waves of contraction and expansion as shown in the video below) and some move by parapodia (kind of like pseudopods). Septa, which separtate body segments, enable the muscles to change the shape of induvidual segements. Other annelids move by whipping movements or cilia. Some examples are earthworms and leeches.

Peristalsis

Nematoda

http://www.earthlife.net/inverts/nematoda.html

Nematodes use a whip-like wriggle to swim. This is callled undulatory propulsion with sinusoidal waves (repetitive oscillation). Some examples are hookworms, pinworms and whipworms.

A movie: Nematoda Locomotion

Echinodermata 

http://www.seasky.org/reeflife/sea2d.html

http://www.mbgnet.net/salt/animals/echinod.htm

All echinoderms have thousands of tiny tube feet or podia on  and many have suction cups on the end. The tube feet are filled with water, and when the organism wants to attach to a surface the water is sucked from the feet. When the organism wants to release it just fills up the feet with water. This is the vascular system. Some examples are sea stars, sea cucumbers and sea urchins.

Platyhelminthes

http://www.discoverlife.org/20/q?search=Platyhelminthes

Platyhelminthes are unsegmented so they have special ways of moving. One way is by using layers of muscles. Another way is by gliding along a slime trail using cilia. An example is a water planaria, as shown below.

Cnideria

http://www.infoplease.com/dk/encyclopedia/cnidarians.html

Some move by contracting their hollow bodies to propel forward (jellyfish). While others move by using tentacles or cilia (hydra).

Porifera

http://answers.ask.com/Science/Biology/how_do_sponges_move

Adult poriferans are sessile which means they dont move yet immature poriferans (larvae) do move. An example is a sponge.

Embryology

http://www.twow.net/ObjText/OtkCbGeRRS04D.htm



The zygote farthest to the right is undergoing Gastulation and
the one next to it is undergoing the formation of a blastula.
You can see these steps more clearly in the diagram below.

Blastula Formation

• After many daughter cells are made they secrete and surround a fluid. The fluid is the blastocoel and the layer of surrounding cells are the blastula.

Gastrulation

• A second layer of cells forms by invagination (half of the first layer turns itself inside out and creates an opening called the blastopore).
• Another opening is made, forming the digestive tract between it and the blastopore.
• Steps after this distinguish the difference between protostomes and deuterostomes.

An example of blastula formation, gastrulation and also radial cleavage



Difference between protostomes and deuterostomes

• Protostomes (mollusks, annelids and arthropods) develop by spiral cleavage (shown below and above) and the first opening is the mouth (blastopore).
• Deuterostomes (echinoderms and chordates) develop by radial cleavage (shown below) and the first opening (blastopore) is the anus.

Animal Cell Research

Animal cell characteristics:

• size- smaller than plant cells
• shape- circular
• cell wall- Animal cells don't have one

Characteristics that all animals share:

• they are all multicellular
• they all have eukaryotic cells
• they are all heterotrophic

The difference between an invertabrate and a vertabrate:

• Vertabrates have a backbone, spinal columns and an endoskeleton,
• Invertabrates don't have a backbone and usually have an exoskeleton