Thursday, 29 March 2012

Bullfrog Video


This video explains the eating habits of a bullfrog. There's a lot of pretty strange stuff that they eat. 

The Poison Dart Frog

Although the poison dart frog is small at about 2.5 cm it packs a powerful blow. It doesn't weigh much either, measuring in at about 28 grams, but it is considered to be one of the most toxic species on earth. To give you an idea of just how poisonous they are: a golden poison dart frog is toxic enough to kill 20,000 mice. The reason for the bright colours of blue, red, green, yellow or orange is actually to warn any predators. their vibrant colours scream at predators: don't eat me, I'm poisonous.

It is reckoned that these frogs get their toxicity from eating insects that have in turn eaten poisonous plants. It is thought this because poison dart frogs that are raised in captivity are not poisonous because they haven't eaten any poisonous insects.

As you would expect, the poison dart frog captures its prey like any other frog. It shoots out a long, sticky tongue which captures the frog's prey. These frogs eat insects such as: fruit flies, small beetles, termites and ants.

The poison dart frog lives in the rain forests of South and Central America. They love the conditions of the rain forests. It's about 27° Celsius, the temperature these frogs thrives on. There is plenty of light and vegetation which gives the right amount of sunlight and shade.


Thursday, 8 March 2012

Frogs: Anatomy

Frogs have a very unique anatomical structure. One example of their special anatomy is their long, sticky tongue which is their way of capturing food. Their tongue is more important than you think, because their teeth are very weak and pretty useless for food capturing purposes. Their legs are also highly specialised for leaping and jumping both high and far distances.

Frogs have a very particular way of breathing. Their skin is porous skin which allows oxygen from the water to go straight into their blood stream. They also have a pair of lungs to allow them to breath outside water.

Unlike humans frogs only have three valves in their hearts. They have two atria and one ventricle. The valves in their hearts are called spiral valves. These control the direction of the flow of blood, to stop oxygenated blood mix with the de-oxygenated blood.

A frog has the ability to hear very high pitched sounds through their ears, but, they can also hear low pitched sounds through their skin.

The frog's sense of sight and smell are very developed. A frog's eyes can detect predators and prey because they protrude very far from the frog's head. By chemical signals, the frog uses their sense of smell to detect possible food sources.




Friday, 2 March 2012

Tadpole

http://en.wikipedia.org/wiki/File:Kaulquappen_Tadpole_3.JPG

Life Cycle of a Frog: Tadpoles

A frog's life starts off with an egg. A female frog lays thousands of these eggs into water in a jelly-like coating. Frogs lay these eggs in clusters whereas toads lay eggs in long chains.

These eggs (frog and toad) are highly susceptible to attack from predators, so as a result of evolution frogs have developed a number of ways to protect their eggs. A common way to ensure survival is synchronised reproduction, which means frogs will breed at the same time. Although there are thousands of eggs produced from each frog the majority do not survive due to predator attack. Another more drastic measure is the effort of the cane toad. The cane toad lays poisonous eggs to try reducing predator attack. 

When the eggs hatch, life is continued on in the form of tadpoles. These have a ovular shaped head with a long flat tail. The tadpoles are very basic organisms. they have no eyelids and their skeleton is made of cartilage. They have external gills but develop internal gills later on in life. Some species of frog develop inside the egg and hatch as small frogs. Most of the time tadpoles are herbivorous and feed of algae in the water. Some species, however, are carnivorous and feed of small insects. The later the tadpoles develop legs, the more likely they are to survive, as tadpoles that develop quickly are often eaten.

Predators of the tadpole include fish, newts, beetles and birds. The tadpole stage of a frog may only last a week, but it could also last as long as a year.

At the end of the tadpole stage, the tadpole undergoes a change. The change itself only lasts about twenty four hours. During this change, the tadpole develops into adulthood. These changes include:

The legs are formed from the disappearance of the external gills. The jaws change into predator jaws from small filter feeding jaws. The digestive systems are formed. The eyes enlarge and eyelids are formed. A nervous system is formed and the eardrums develop.

The tail will still remain for a while, but once it has been absorbed by the frogs body, the frog can leave the water for the first time.