Monday, August 27, 2012

Animals In Armour - The Successful Trilobite

Armoured Arthropods - The Successful Trilobite

Insects are regarded as the most diverse of all the animal classes on planet Earth. To date something like 1,000,000 different species have been recognised and it has been estimated that there may actually be 30 million different species of insect around today. These numbers are truly astronomical, especially when some older colleagues remember estimates for the total biodiversity for all animal species on this planet being put at around 2 million species as recently as the mid 1970s. To palaeontologists, one part of the Arthropoda is extremely important to them, the humble Trilobite may not have that many museum exhibits dedicated to it, but the importance of this segmented, extinct, marine creature should not be underestimated. The Trilobite is one of the most fascinating and important of all the creatures known from the study of natural history.
A Remarkable Phylum - Arthropoda
However, the class Insecta makes up just part of a remarkable phylum - the Arthropoda, a phylum that can be traced back to the Cambrian geological period and in all likelihood these animals and their ancestors made up a great portion of the life that existed during the Cryptozoic, that vast eon of time, otherwise known as the Precambrian when there was life on Earth but it has left few traces in the fossil record.
A Wide Variety of Body Plans and Shapes
Arthropods have evolved to fill a vast array of environmental niches, with types of Arthropod found in most habitats - in water and on land. Crustaceans, such as crabs, lobsters, barnacles and shrimps, along with all insects, scorpions, mites, spiders and millipedes are all members of this phylum. A number of extinct types of Arthropod are represented in the fossil record. The most important extinct group are the Trilobites. These armoured animals evolved in the early Cambrian and survived until the end of the Palaeozoic. As a class, Trilobita finally died out around 250 million years ago, at the end of the Permian period, when approximately 90% of all life forms became extinct.
Trilobite fossils have been found all over the world, in Africa, Europe, the Americas, Antarctica and in Asia. Many young fossil fans start their own fossil collection with a Trilobite fossil that they have found.
Ten Orders of Trilobite
Ten orders of Trilobita are recognised at present, although the taxonomic classification and phylogeny of Trilobites is frequently reviewed and debated. Despite the extensive fossil record of these animals, (their exoskeletons are partly comprised of calcite and this coupled with their marine existence gives them a high potential for preservation as fossils), there are still gaps in our knowledge regarding the evolutionary relationship between different orders.
Approximately, 20,000 species of Trilobite are known, they are regarded as the standard bearer for the entire fossil record represented by Palaeozoic strata, although as a group the Trilobita were at their most diverse and abundant in the early Palaeozoic. All but one order of Trilobites were extinct by the end of the Devonian, and by the end of Permian only two families of Trilobite remained with a number of other families dying out in the mid Permian. Changes in climate, rising sea levels and the evolution of efficient predators such as sharks have all been put forward as theories to explain the demise of the Trilobite.
They were certainly a remarkable and highly diverse group of animals and their importance in biostratigraphic processes as well as the assistance of their fossils in the relative dating of strata should not be underestimated.
Everything Dinosaur is a company run by parents, teachers and real dinosaur experts. It specialises in developing educational dinosaur toys, models, clothing and games and strives to help young people learn more about science through their fascination with prehistoric animals. Many of the items featured on the Everything Dinosaur website Everything Dinosaur have been designed and tested by teachers.
Our aim is to help young people learn more about Earth sciences through their fascination with fossils. With something like 900 products on line including dinosaur party supplies, Everything Dinosaur has built up a strong reputation assisting parents and teachers.

Monday, August 20, 2012

Why Palaeontologists Love Ammonites

The Loveable Ammonite - Why Palaeontologists Love Ammonites

Surrounded by various dinosaur fossils such as bones, pieces of eggshell, gastroliths (stomach stones) and even some fossilised Sauropod poo (coprolite), in a museum, it is easy to get carried away with dinosaurs and the study of dinosaur fossils. However, over the entire fossil record, dinosaurs are not that significant in terms of their role in helping to determine the age of the order of deposition of strata. Other groups of fossils are much more significant to both geologists and palaeontologists. Perhaps it is time to reflect on the importance of Ammonites to scientists.
Ammonites Mesozoic Cephalopods
Ammonites are a large group of Mesozoic cephalopods, close relatives of squid, cuttlefish and the octopus, these are the animals that lived in flat-sided, coiled, planispiral shells (most Ammonites had these type of shells). Originating in the late Silurian, most likely from more simple, straight shelled molluscs, the Bactritoids these animals survived numerous mass extinction events and became one of the most abundant life forms in Mesozoic marine environments, along with their close cousins the Belemnites.
Ancient Marine Invertebrates
The Bactritoids (orthoconic shelled animals - means straight shells), originated sometime in the Devonian Period and persisted until the early Triassic. As well as being considered the ancestors of the Ammonites and Belemnites they are believed to be the ancestors of the soft-bodied cephalopods still around today (coleoids such as squid, octopus and cuttlefish).
Ammonites diversified during the Mesozoic and there were hundreds of different species. Their shells (made of aragonite, a form of calcium carbonate), are readily preserved under the appropriate conditions and this is why we have such an extensive fossil record of this particular Sub-Class of Cephalopods.
Common Fossils
As fossils of these creatures are very common they are important to palaeontologists and geologists as they can help identify the relative ages of different rock strata. Their diversity and rapid evolution into many forms help scientists to work out the order in which sediment strata was laid down, in this way the relative age of rocks can be calculated in relation to each other. Ammonite fossils provide a biological "key" with which palaeontologists can date the deposition of strata, in fact many layers and sequences of rocks are named after the Ammonite fossils they contain. This process of using fossils to help identify the age of deposits is known as biostratigraphy. Due to the abundance of Ammonite fossils and their world-wide distribution, rock sequences many thousands of miles apart can be dated using this method. The particular Ammonite fossils associated with each layer of rock are called "zonal fossils". Dinosaur fossils in contrast, do not make good zonal fossils. They are very rare, usually found as incomplete and not laid down in a marine environment only very occasionally can dinosaur remains be considered as potential zonal fossils - the Hypsilophodon bed on the Isle of Wight being a possible example.
Mass Extinction Event at the End of the Cretaceous
Towards the end of the Cretaceous the Ammonites as a group began to decline. The fossil record shows that there were fewer and fewer genera (although some evolved into very bizarre and ornate forms in the late Cretaceous). The group went extinct along with the Belemnites at approximately the same time as the dinosaurs. Why this particular group died out, yet the similar looking Nautilus survived is unclear. There are two species of Nautilus around today, indeed, our studies of these animals have helped fill in the gaps in our knowledge about Ammonites. One theory as to why the Nautilus survived whilst the Ammonites died out is that on close examination the shell of Nautiloids are thicker than that of Ammonites. Modern day Nautilus live in relatively deep water, Ammonites seem to have been a creature of shallow seas. The thicker shells of the Nautiloids are able to withstand the greater water pressure at depth.
Destruction of the Marine Environment
If the marine environment had been subjected to a prolonged period of darkness (dust in the atmosphere from a meteorite impact for example), then the photosynthesising plankton would have died off and this would have broken up the food chain. The deeper living Nautiloids may have been better able to cope than the surface dependent Ammonites. Also, such environmental impacts would have severely disrupted the breeding cycles and destroyed much of the larval stage populations. This too could have contributed to the Ammonite extinction. In addition, if large ammonites of carbon dioxide sulphur hydroxide had been deposited in the seas, this would have led to extensive acidification of shallow, marine environments and this may have prevented the Ammonites from being able to form their shells properly - again helping to reduce the population of these animals. These factors along with the rapidly evolving new Teleost fish (modern fish) which may have predated on Ammonites and the competition from other cephalopods may have resulted in the extinction of this very important, and once diverse animal group.
Everything Dinosaur is a company run by parents, teachers and real dinosaur experts. It specialises in developing educational dinosaur toys, models, clothing and games and strives to help young people learn more about science through their fascination with prehistoric animals. Many of the items featured on the Everything Dinosaur website Everything Dinosaur have been designed and tested by the teachers and real dinosaur experts in the company.
Our aim is to help young people learn more about Earth sciences through their fascination with dinosaurs and other prehistoric animals. Team members are happy to provide advice and support supplying free quizzes, drawing materials, puzzles, games even recipes for dinosaur themed biscuits and birthday cakes. With something like 600 products on line including dinosaur party supplies, Everything Dinosaur has built up a strong reputation assisting parents and fellow teachers.

Sunday, August 12, 2012

Lion - The Most Social Animal Out of All Cats

Lions are the second largest living cats today. Though they were spread all over the world at one time, they are limited to Sub Saharan Africa and a few areas of Asia today. Even the available population of these animals is endangered due to loss of their habitat as a result of human activities. During the past two decades alone the population of these majestic animals has come down by 30 to 50%.
In the wild a lion may live 10 to 15 years. Generally, a male will live only around 10 years as they often get injured fighting with other males. In captivity there have been occasions where they have lived up to 20 years. They normally live in grasslands and savannas. However, they could be found in forests also. They are highly social animals. A pride of lions consists of a few females that are related and a few males. They live together and hunt as a pack. It is the females that do the hunting.
Lion is the tallest of cats being at least 5.5 inches taller than a tiger. However, a lion is not as strong as a tiger. Color of these animals varies from light brown to reddish. They are animals that have distinctive differences between the males and the females of the species. The male lion has a shaggy main and the female doesn't have one. Even the roles of the males and the females in the pride are different. It is the females that do the hunting.
When it comes to the lifestyle of lions it is noticed that they either live in groups that are called prides and confine to certain territories or roam the jungles as lone animals. This second type of animals is called nomads. While the lionesses do the hunting the lions look after the territory. When the cubs are born they are nursed by the mothers. Once the males grow up they are abandoned by mothers. These grown up cubs that become adult males become nomads.
Though lions are carnivorous animals they are not able to run fast for long distances. Therefore, they need to close on a prey stealthily until they come as close as 30 meters to the prey. Once they close on a heard of animals they select the closest animal and chase after it. Often they surround the animal on a few sides to make it easy to catch the prey. It is the hunters that eat the flesh of the prey first.

Sunday, August 5, 2012

What Fish Should I Use in My Aquaponics System?

If you are familiar with aquaponics, then you may be asking the question, "What Fish are the best for my system?" Good question. The answer depends on what you are planning to do with the fish, and how big your system is. There are several key environmental factors that will drive what fish you should raise for your aquaponics system. They are:
• Must be capable of reproducing in captivity
• Must have well-known requirements as far as how they are raised
• Must be adaptable to having other species in the tank
• Must grow fairly quickly and to a large size
• Must readily adapt to artificial feed sources
• Must be tolerant of crowding and high density conditions (living in a tank)
• Must have high survival or low mortality rates when raised in a contained environment
• Should be resistant to disease and parasite infestations
• Should not be cannibalistic or territorial because that would cause obvious problems in the tank
• Should be easy to acquire on the market as eggs, fingerlings, or adults
• If you are going to sell the fish, they should have a high market demand
• Should product a good amount of feces.
• If you are going to sell them, they should be good as a food source.
These limitations drive out a select list of fish that make the good aquaculture resource. The best fish to use in your tank are:
Small Home System:
• Goldfish 
• Carp

Medium System
• Tilapia 
• Channel Catfish 
• Arctic Char

Goldfish and Carp are the easiest to use in your tank because you can find them in any pet store. Because they are so common, and are purchased as pets, they are easy to take care of. Just ask your local pet store owner about the water temperature they need, and the food pellets that they eat. They are obviously not going to be eaten by most of us, so you won't have to worry about replenishing them.
Tilapia is a warm water freshwater fish. If you have eaten in any local restaurant, you have probably seen Tilapia on the menu. Its flesh is white, moist and mild flavoured. Purchased as fingerlings, they are ideal for aquaculture because they are very fast growing. As a warm water fish, you will have extra costs from heating the tank. As far as what they eat, they are omnivorous, eating a variety of plants and animals. With Tilapia, you will be able to raise fish to eat, while at the same time growing plants to eat.
Channel Catfish are another common fish used in Aquaponics. Less of a delicacy than the Tilapia, the catfish is still a unique dish served in restaurants. Catfish are more commonly raised because of their versatility. They are less susceptible to temperature changes than Tilapia. They can handle cold water growing well below 70 degrees, and will keep growing when the water temp is hotter. They are very fast growing. To feed the channel catfish, you will need a protein pellet mixture. They will also eat live food such as molluscs, insect larvae, and worms. The resulting meat of harvested aquaculture raised catfish is tender and good tasting and lacking in that "muddy" flavour that you might find in a catfish caught in the wild.
Arctic Char are a unique cold water, freshwater fish. They have qualities of a salmon, and also that of a trout, and because of this, they are a sought after fish by many a chef. They are typically fed nutrient dense dry pellets. In the winter, in the cold arctic, they gather close together in the open pockets in the ice making them accustomed to very close quarters. This makes them used to living in close quarters, and ideal for aquaculture.