HOW TO: Disect a Frog

Frog (Amphibia)

Background

Frogs are found on every continent except Antarctica. They are able to live in a wide range of environments. Since frogs are amphibians, they are able to live on both land and sea. They have a preference for environments such as: creeks, ponds, swamps etc. As larvae, frogs are able to breathe through their gills in water. As adults on land, they breath with their lungs and through their skin by cutaneous gas exchange. Frogs are carnivorous, which means that they eat meat—insects such as flies, mosquitoes, moths, and dragonflies. 

FUN FACT: One gram of the toxin produced by the skin of the golden poison dart frog could kill 100,000 people.

External Anatomy 

Tympanic membrane— eardrum of the frog that receives sound 

Glottis— opening from the mouth into the respiratory system 

External nares— nose of the frog that helps air go in and out

Nictating membrane— transparent part of frog's lower eyelid that cleans and protects it

Internal Anatomy 

Esophagus— connects the mouth of the frog to the stomach

Gall bladder— sac that stores the bile

Liver— secretes the bile and processes digested food

Large Intestine— stores undigested food

Cloaca— products of the frogs digestive and urogenital system pass through this organ when going out of the body

Fat bodies— fat that is in the body cavities of the frog that are needed for hibernation and mating

Incision Guide

Dissection Procedure 

HOW TO: Dissect and Earthworm

Earthworm (Oligochaeta)

Background

Earthworms can be found all over the world, the ones that live under the ground get their nutrients from the dirt. The reason that earthworms come to the surface of the Earth when it rains is because the earthworm breathes through its skin and its skin has to stay moist, so when the earthworm is placed in a position with water it thrives. Earthworms eat dirt, they eat things such as dead leaves and roots found in the soil. They also eat small living bacteria that is found in the soil. Earthworms do not have ears or eyes, they have one side of their body that is more sensitive to light than the other. 

External Anatomy 

Clitellum— synthesizes a reproductive sac of mucus

Septum— the structure within segments that connects the skin and internal organs

Anterior end— end where the mouth is located

Posterior end— end where the anus is located

Male Genital Pore— opening where sperm from worm is ejected during mating

Internal Anatomy 

Pharynx— sucks the food into the worm

Seminal Vesicle— stores the sperm of the worm

Gizzard— grinds the food for the worm

Dorsal blood vessel— carries the blood to the anterior end

Ventral blood vessel— carries the blood to the posterior end 

Crop— temporarily stores the food

Aortic arches— pump the blood

Incision Guide

Dissection Procedure

 

HOW TO: Dissect a Fish

Fish [Yellow Perch] (Osteichthyes)

Background

The Yellow Perch is a ray-finned fish, the ray shaped fins help the perch to move quickly through the water. The Yellow Perch lives in ponds, lakes, and streams. They require fresh water and lots of vegetation/plants. They feed on algae and plankton but, when they get older they feed on small aquatic insects. Larger perch feed on insects, crayfish, snails, mussels, leeches, fish eggs, and worms or even smaller yellow perch. Being a fish, the perch breathes through the gills on the sides of it's body. Female perch lay eggs (up to 40,000) and multiple males fertilize them. The eggs can swell up to a point where a strand of them would be over eight feet long. 

External Anatomy 

Mouth - composed of the maxilla (upper jaw) and mandible (lower jaw), is used for eating
External nares - nostrils that open/lead to the olfactory sacs
Eyes - the yellow perch as lateral eyes and no eyelids
Gills - behind operculum, used for breathing underwater
Lateral line - detects movements and pressure changes in water
Fins - dorsal (on top of the fish), caudal (end of tail), anal (ventral end of tail), pectoral (lateral, paired), pelvic (below pectoral), all work together for swimming, steering, and maintaining equilibrium
Anus - opening used to discharge waste

Internal Anatomy 

Swim bladder - sac filled with oxygen, nitrogen, and carbon dioxide. Adjusts the gravity of the fish in different depths of water. Also secretes and absorbs gases.

Olfactory lobes - smell section of the brain

Optic lobes - thin, posterior to cerebrum, vision section of the brain

Medulla - enlargement where the spinal chord and brain meet

Incision Guide

Dissection Procedure 

HOW TO: Dissect a Crayfish

Crayfish (Malacostraca)

Background

Crayfish are found in all bodies of fresh water such streams, rivers, lakes, and ponds. The place where crayfish are typical found in Northern Virginia. Crayfish are omnivorous and can eat just about anything. According to this website, if you have a pet crayfish you could even feed it cat food and hot-dogs and it would still be happy. They breathe through gills and can live outside of water as long as their gills are wet. Crayfish are able to live up to 20-30 years. 

External Anatomy 

Anntenule - an anntena-like appendage with receptors for touch, taste, and equilibrium

Uropod - anterior flipper that propels the crayfish through the water

Cheliped - claw used to capture food and provide defense

Telson - flat triangular section of the tail, used for swimming

Walking legs - enable the crayfish to walk slowly

Swimmerts - organs that create water currents and functions in reproduction

Internal Anatomy 

Green Gland - removes chemical waste from the blood

Mandibular intestine - carries waste

Ganglia - bundle of nerve cells

Stomach - has chitinous teeth which grind food to a paste

Oviduct - passageway for eggs

Incision Guide

Dissection Procedure 

HOW TO: Dissect a Starfish

Starfish (Sea Star)

Background

These invertebrates reside in all parts of the ocean, including the Atlantic Ocean to the Indian Ocean. Starfish primarily feed on clams, oysters, sand dollars, mollusks and mussels. Starfish are able to breathe through their feet. Their feet are made of a very thin tissue in which gases can move easily. Ironically, starfish are not actually fish. They do not have gills, fins, or scales like fish do. They move with their feet while fish propel themselves through the water.

External Anatomy

Aboral Surface— side of the starfish without a mouth ("top")

Oral Surface— side of starfish with mouth ("bottom")

Eyespot— lies underneath the skin, can detect light and dark

Central Disc— center of the starfish from which the arms start from, contains the madreporite, mouth, and anus

Madreporite— used to filter water into the water vascular system of the echinoderms

Ambulacral Groove— contains the feet on the oral side and used to open up shells for food

Internal Anatomy 

Digestive glands— break down food by the use of enzymes and connected to the stomach

Ring Cartal— carries water from the stone canal to the radial canal, connects the two canals

Ossicles— forms part of the exoskeleton and provides protection and strength

Gonads— reproductive organs (ovaries or testes) that are used with reproduction by producing egg or sperm

Lateral (Radial) Canal— runs the length of the starfish arm and is part of the water vascular system

Ampulla— fills up with water and then releases water to feet

Incision Guide

Dissection Procedure

 

HOW TO: Dissect a Grasshopper

Grasshopper (Romalea)

Background

Grasshoppers are widespread in the United States, they are most prominent in the fall months. Found in areas with grasses, vacant lots, and gardens. Grasshoppers are herbivores so they manly feed on grasses. Grasshoppers have holes on their abdomens and thorax called spiracles. They have an exchange of oxygen and carbon dioxide between their tissues (called tracheal breathing). In the early stages of a grasshopper's life, they do not have wings. However, as they mature, they develop wings. They are visible as small pads at the end of the thorax. 

External Anatomy

Head

Antennae - located on the head above the mouth.  Is used like a human's nose, but senses odors, touch, humidity, vibration, wind velocity, and wind direction.

Compound eyes - (2) can see shape, color, movement and distance.

Simple eyes - can only detect light intensity

Thorax

Legs - There are both walking and leaping legs.  The four walking legs are located toward the front of the thorax, and the two leaping legs are located toward the back.

Abdomen 

Ovipositer (females) - Where tube is located to deliver eggs

Spiracles - used to breathe

Internal Anatomy 

Dorsal Blood Vessel - heart

Tracheae - network of air tubes

Ganglia - bundle of nerve cells

Crop - stores food

Gizzard - grinds food with chittinous plates

Intestine - transports waste through the digestive system from the ind gut to the rectum

Malpighian Tubules - removes chemical waste from the blood

Rectum - passageway for digested waste from the intestine to the anus

Incision Guide

Dissection Procedure

HOW TO: Dissect a Clam

Clam (Bivalvia or Pelecypoda)

Background

Tend to inhabit shallow waters, there is over 15,000 different living species and 500 live in fresh water while the rest live in salt water. Clams are filter feeders, they pump water through their bodies to capture microscopic organisms such as plankton. The clam breaths through gills, the gills are used for both breathing and feeding the clam. The clam sticks the ends of its siphons out of the shell and food and oxygen come in one end and out the other. Clams move by the use of their foot, the foot allows the clam to move from side to side when necessary. Below is a video of a clam using its foot in order to move on land:

External Anatomy

Umbo— oldest part of the clam, where the clam, highest part of the shell

Growth Lines— shows the age of the clam

Hinge Ligament— hinges the valves together and allows them to open and close, important part

Internal Anatomy

Stomach— separates water from the food, starts digestive process 

Gill— filters oxygen from the water in order for the clam to breathe

Mantle— cover for the clam that helps with growth, respiration, and shell color

Axe foot— allows the clam to burrow and move around, axe shaped

Incision Guide

Dissection Procedure