Crocodile

Lovely hand drawn Crocodile, perfect example of evolution to achieve the specific requirements for this habitat. This species heritage goes back to dinosaurs and is still a surviving strongly.

Danger of Bacteria Evolving

            The animal kingdom is made up of many components such as mammals, birds etc. but one of the most forgotten animal families is the amphibians, are ectothermic (cold-blooded) family plays a major role in our ecosystems. Amphibians can be separated into three different categories, frogs and toads, newts and salamanders and caecilians.

            What makes amphibians so special compared to other animals is their unique ability to live on both land and water, also the process which they take growing up, from aquatic larvae which use gills to breathe to developing into terrestrials which use their lungs to breathe oxygen. There are exceptions to this though; some salamanders such as the golden alpine salamander (Salamandra atra) which live only on land their whole lives, or the axolotl (Ambystoma mexicanum) which only ever live in the water. Amphibians can vary in size dependant on their species, they can  be as small as 7.7 millimetres long or be as big as 1.8 metres long.

The global status of our amphibian gets drastically worse every year due to a number of causes. One of the main causes is unknown diseases as well as climate change, habitat loss, invasive species, and pollution and of course human influences. Research carried out on the 5,743 amphibian species shows and highlights decline, extinction and some of the possible causes.

In more recent years the discovery of a particular disease known as Chytridiomycosis, has vastly contributed to our amphibian decline. It has many abilities such as eliminating an entire species of amphibians and its ableness to spread to different locations around the world like wild fire.

The image below highlights where worlds amphibian species can be found, as well as how many different species can be found there. Not too surprisingly, there is a vast amount of blue colours showing no more than six species are in these areas.

The Global Amphibian Assessment (GAA) analysed every known species of amphibian and found that out of 1,856, 32% were threatened with extinction. Then analysing all of the species, a further 43% of the species are currently in decline compared to the less than 1% which had actually increased in population size. Shockingly only 23% of the amphibian species population were stable leaving the last percentage of species as unknown.

Amphibians are vital to our ecology, disturbance in the population dynamics affects everything in that area from big things like other animal population dynamics to smaller things such as plants, trees and rocks.

Amphibians are highly sensitive to any and all environmental changes due to a number of factors such as having sensitive skin (permeable). When things such as disease, climate change, or habitat destruction amphibians are affected not only first but the most.

In this diagram you can see the trend patterns of 936 populations of amphibians and how over the years they have steadily declined and fluctuated.

           

This is another diagram highlighting declines in more detail for both North America and Western Europe.

Chytrid Fungus

One of the world’s biggest amphibian killers at the moment is a fungal disease known as

Chytridiomycosis. Chytrid fungus is disease caused by a particular type of fungus; often found in places with water or high moisture. Research so far suggests that it only affects amphibians. However, although the fungus only directly affects amphibians it causes a chain reaction between predators, prey that echo throughout the whole ecosystem. One of the worlds most affected amphibians is the critically endangered is the mountain chicken.

The disease affects the outer layers of the skin, which contain keratin, this is the layer of skin which is meant to resistant to damage. Chrtridiomycosis makes the skin become tougher and thicker, this makes it difficult to absorb water and salts through the skin which in turn cause not to receive the required amount of oxygen. The final result is death by suffocation. The disease can be recognised by its symptoms;

·         Reddening

·         Discoloured skin

·         Shedding increase

·         Abnormal behaviour

·         Seizures

·         Nocturnal animal becoming diurnal

One of the problems scientists diagnosing the disease is that the symptoms overlap with other amphibian diseases. Fortunately captive kept amphibians can be treated with antifungal treatments and full enclosure disinfection, so far there are no ways of treating wild none captive populations.

In Montserrat and Dominica a Mountain Chicken Recovery Programme was put in place the restore the population of this particular breed of frog. They work with European conservation institutions the country governments to try and prevent the frogs from extinction. They manage to breed, restore and research the frogs in order to prevent further extinction of damage to the ecosystem.

In 2009 when Montserrat discovered that the area was infected by the disease they launched a rescue mission where they removed 50 healthy samples of the mountain chicken frog and placed them into captivity to begin their research and bio-secure breeding programme.

Nationally our own amphibians are in decline, for example the Natter jack toad which lives in a variety of habitats such as coastal dunes, upper saltmarshes and lowland heaths. The chytrid fungus is one of the main causes yet again for the decline but also habitat destruction and the

 naturally changing climate altering out British seasons play a major role.

To preserve the toad action is being taken to preserve the sand dunes by restoring them and creating new habitats such as the yellow-dune habitats. This is when they place new substrates and environmental attributes to replace where the natural habitat has been eroded. They try to prevent beach cleaning operations and prevent the natural process of land formation.

Not only are they maintained and creating the dunes for the Natter jack toads but they are also doing it for the pools. This involves pH maintenance, putting in basins to prevent natural erosions which could remove the pools from the habitat. The creation of pools for the toads encourages breeding and population as they replace the old ones and provide safer and more distribution.

Natural Selection

Natural Selection is one of the key ingredients of constant evolution, followed by mutation, migration, and genetic drift.

Both Charles Darwin and Jean-Baptiste Lamarck proposed different explanations of what natural selection was and how it occurred.

Jean-Baptiste Lamarck's Theory

1. The Giraffe stretches their necks to reach the leaves
2. Eventually the necks of the giraffes grow with use
3. The Giraffes offspring inherit the long neck

Charles Darwin's Theory

1. Giraffes with longer necks can reach more leaves
2. Making them more likely to gain enough nutrition to survive and go onto reproduce
3. The Giraffes offspring inherit the long neck trait

After data gathering and analysis Lamarck was dismissed, Darwin's theory was concluded true.

Further break down of Darwin's theory;

Observation 1- All members of any population often vary in their inherited traits.

Observation 2- Every species is capable of producing more offspring than the environment can naturally support, therefore meaning that some will fail to survive and reproduce.

Inference 1- Organisms with inherited traits are more likely to survive and go onto reproduce, leaving more offspring in the environment compared to others of their species.

Inference 2- The unbalanced ability of specific organisms to survive and reproduce eventually leads to an accumulation of desirable traits in the population occurring over generations.

Key Points

• Wide range in variation
• Variation is caused by the significant number of differences in genes
• The characteristics which are most suited to the environment are more likely to survive and be passed on
• Genes are passed to the offspring

Evolution of the Pentadactyl Limb

What is a Pentadactyl Limb?

It is a limb that has 5 limbs on the hand and foot.

All the bones are symmetrical to the other limbs; such as both hands, both feet as other Pentadactyl animals.

Examples of  Pentadactyl animals are; Whales, Bats, Pre-evolved Horses and most mammals.

A Brief History

Extinct species; that existed 380-360 million years ago (the first known Tetrapods) developed 8 digits when evolving into land mammals.

Over time, the number of digits reduced to an average of 5 digits.

However, in some cases, some animals are born with extra or missing digits. This is due to a mutation.

Which Animals Have Pentadactyl Limbs?

It is most common with humans and other mammals, except whales and dolphins, as they have evolved, their back limbs have reseeded back into their bodies, as they no longer need them. Also, with no external hind legs, it allows them to move easily through the water.

Other mammals have extra digits, such as Pandas, which have  digits.

Mammals, such as Moles appear to have extra digits, however, these are only out-growth bones on their wrist.

Pentadactyl limbs are most common with Tetrapods; 4 limbed creatures.

Other Animals With Pentadactyl Limbs

These are Birds, Dinosaurs, Reptiles and Amphibians. For example, Amphibians such as frogs have 4 digits, and Birds only have 3.

Extinct Tetrapods, Dinosaurs, had 3 toes, and Marine mammals have 5 digits.

Another example is the bat. Their fingers have adapted; elongating to help form the bats wings, while the thumb is used to grip onto trees.

Examples

A)  Mammal Foot

B)  Seal

C)  Mole

D)  Camel

E)  Horse

F)  Cheetah

G)  Bat

H)  Kangaroo

I)  Lemur

J)  Sloth