FROG WEEK

FROG WEEK

What I will be learning:

The classification, anatomy, and habits of frogs.

Information to succeed at frog dissection.

Why I will be learning it:

Though frogs are amphibians they have a lot in common with us. They have many similar organs and processes. 

We can learn a lot about amphibians and about human beings from being able to look inside a frog.

How I will know I learned it:

I will be able to discuss the classification of frogs, some of their habits and habitats, as well as their anatomy.

I will be prepared to come to class in the future and dissect a frog, maximizing what I learn from the experience.

 

NAMING THINGS

All organisms are organized into a classification system based on:

PHYLOGENY-the study of the evolutionary history and relationships among or within groups of organisms. …in other words- which organisms they come from.

Taxonomy-is the science/study of classification

We are not closely related to Frogs…..But we have many organs and processes in common.  We can learn a lot from a frog. 

All living things are classified into Domains, Kingdoms, Phylum, Class, Order, Family, Genus, Species.  Human Beings are classified in the chart below:

How closely related are humans and frogs?  Look at the chart below:

AMPHIBIAN-means “Double Life”

Amphibians are small vertebrates that need water or moisture to survive.

This includes frogs, toads, salamanders and newts.

They have glands on their skin that produce proteins that help transport water, oxygen, and carbon dioxide through the skin. Some even produce a poison to hurt predators.  They are often brightly colored to warn predators away. 

Frogs reproduce sexually.  Egg fertilization happens outside the body, when the male and female release eggs and semen at the same time. The eggs need moisture to develop and the parents abandon the eggs as soon as they are fertilized.  They hatch in days or weeks, becoming tadpoles.

 

FROG LIFE CYCLE:

Can lay between one and 30,000 eggs, and may not care for the eggs after laying them.

There are lots of exceptions- some do care

for their eggs, and even carry them around    

 

Metamorphosis- drastic changes in habits and body structure

SKIN- Smooth and scaleless

• Glands for secretion
• Some have poisonous secretions.  Dart frogs don’t make the poison- it comes from the

Centipedes they eat

• Chromatophores- camouflage some frogs by light reflection, others use bright coloration
• Respiratory organs and blood vessels next to the skin exchange CO2 and O2

Respiration- Use four Methods to obtain Oxygen

• Gills- as a tadpole
• Lungs- internal organs for the exchange of gasses
• Mouth- lining of mouth and throat have blood vessels for gas exchange
• Skin- frogs can breath and drink through their skin. When frogs hibernate they depend on this.  Some even have a special "drink" patch of skin on their bellies.

Circulatory System:

AMPHIBIANS have a 3 chambered heart

-Two Atria and one Ventricle

- Oxygenated blood enters the left atrium

-Deoxygenated blood enters the right atrium

-Both atria empty at the same time into the ventricle and mix together

Reproduction:

The Male frog has a larger thumb than the female, with a dark patch on the thumb pad…indicating he is male- this is used to grasp on to the female and hold himself close to fertilize the eggs as they come out of the female frog. The large thumb pad is also called the “nuptial” pad. 

The position is called amplexus and may last several days.  It stimulates the female frog to release eggs, which the male frog ejects his sperm directly over to fertilize.  

The eggs are covered in a protective jelly.  When exposed to water, this can swell to many times its orginal size, making it difficult for predators to get to the egg.

Some frogs leave their eggs on their own..and predators may get them.  Other male and female frogs protect their eggs, some even carrying them on their back or in a pouch. Generally, the kind that don’t protect their eggs have more eggs as a reproductive strategy. Some frogs even sit on their eggs.  

AMPHIBIANS ARE ECTOTHERMIC:

Ectothermic- their body temperature and activity changes with the surrounding temperatures

HIBERNATION- Burrow into the mud of a stream and wait out the cold weather

-their heartbeat and circulation slow

-some produce antifreeze material in their blood to keep tissues from freezing

-need little food during this time- use fat stores

-Oxygen diffuses through the skin

 

     

 

ESTIVATION:

A Summer hibernation where amphibians escape the heat by burrowing into the mud and hiding in a cool place.

THE DIFFERENCE BETWEEN FROGS AND TOADS:

Frogs have smooth, shiny skin that dries easily. They live near water. Toads have dry, warty skin, enter water only to mate, and have shorter hind legs than frogs.  

 

ANATOMY AND PHYSIOLOGY OF A FROG:

EXTERNAL:

-Eyes Bulging and on top of head, to see when just barely poked up out of the water.

-The frogs back is covered in irregular markings, spots or colors, for either camouflage or for warning predators.  The belly is generally not colored as predators are usually coming from above.  

-Cloaca- is the opening at the rear of the frog for urine, feces and reproduction

-Large Bulging Eyes with Nictitating Membrane- folded -Transparent membrane (Third eyelid)- keeps the eye moist and protected. 

-Nostrils- enter into the mouth--this all allows the frog to breath while just having the top of its head out of the water.

-Tympanic Membrane vibrates with sound like our eardrum.

-Forelegs have 4 digits-with a specially designed male thumb for grasping females.  Hind legs have strong muscles for jumping, fins for swimming, and 5 digits.

-This all allows the frog to breath while just having the top of its head out of the water.

- Thin mucus covered skin, allows for respiration in water, protection outside of water, and slippery for predators

EATING AND THE MOUTH OF A FROG

A large mouth designed to capture insects 

A large sticky tongue attached to the floor of the mouth at the front- flips out quickly and catches prey. It has a sticky mucus that helps catch prey.  A frog can stick its tongue out and draw it back in  .07 seconds, and the prey experience about 12 G’s of force when being dragged into a frog's mouth. 

Frogs blink when they swallow.  The eyes are pressed into the mouth cavity to help crush the food and force it down the gullet

 

Openings Inside the Mouth

-Nostril openings at the front roof of mouth

- Eustachiun tubes- unite the ear cavity with the mouth at the back corners

-Gullet- passage to the digestive tract at the back of the throat

-Glottis- small swelling parted by a slender opening- leads to lungs

-Vocal Sacs- in the floor of the mouth in males- passes air through these openings into the sacs when it “croaks” to increase volume of sound.

Teeth- Maxillary-TWO sets of inconspicuous teeth in UPPER JAW

-Vomerine Teeth- two teeth between the internal nostril openings in the roof of the mouth- assist frog in grasping prey, no for chewing- vestigial

For more information on frog anatomy try out this idssection video: https://www.youtube.com/watch?v=3X0tTUjscGI

FROGS HAVE NO LOWER TEETH