Fossil graptolites are tiny, typically glossy, pencil-like lines on rock surfaces, and their name originates from the Greek for "writing in the rocks." These fossils date back about 500 million years.
Their bodies were flat, with a ribbon-like shape, usually up to 1 millimeter wide and 10 centimeters long. The ends of the fossils were often pointed or blunt. There were several types of graptolites, distinguished by differences in body structure and size. Some were very small, only a few hundred microns long, while others reached lengths of more than a centimeter.
They lived in vast numbers in all parts of the world where there was water with soft bottom conditions suitable for their growth. Most likely, they contributed significantly to the evolution of life on Earth as they preyed on other organisms that got caught in their net-like bodies.
In modern times, graptolites are used in scientific studies to determine how ancient environments may have looked. The ribs of some graptolites can be seen in the British Museum's fossil collection.
You can learn more about this group of animals from Graptolite.com. This site provides information about these fossils that is not always apparent in textbooks.
Graptolites were almost certainly suspension feeders. They would have fed by removing plankton and other food particles from the water. They presumably utilized small hairs (cilia) linked to tentacles to catch food, just like their surviving cousins (animals called pterobranchs). Because they are preserved in the same way as fossils, we know that they must have been covered with a shell. This shell would have been strong but light, similar to the shells used today by hermit crabs. The shell would have contained holes or openings called ooecia through which the animal could breathe.
Graptolites lived in colonies. It has been suggested that these colonies were made up of thousands of individuals, but this is probably an overestimation. What is known for sure is that they were packed together tightly, probably forming large mats or beds within the sediment. It is possible that there might have been some kind of chemical signal that allowed members of different colonies to recognize each other and not attack one another. In any case, it seems clear that graptolites were very social animals.
Graptolites were undoubtedly diverse in shape and size. Some species were quite large, measuring over 2 inches (5 cm) long and half an inch (1.5 cm) wide. However, most were much smaller. Some species may even have been microscopic. Modern analogues include the ciliate protozoa.
Perlite is a white granular substance that is lightweight. It has the appearance and feel of polystyrene but is really formed of expanded volcanic glass that has been heated to 1000 degrees Celsius till it 'pops' (like popcorn) to many times its original size. It is lightweight, sanitary, and simple to use, as well as long-lasting. Perlite is used in gardening and horticulture for filling soil and cinder blocks, among other things.
Perlite can be bought in bulk quantities from specialty potting companies or garden centers. It is available in sizes ranging from powder to large boulders. This article will focus on using perlite as an additive to potted plants.
When adding perlite to your plant containers, try to avoid packing it in too densely or it may cause your compost to become soggy over time. A layer of 3 inches is sufficient for most container plants.
There are two types of perlite: 100% pure and blended. Pure perlite is white, while blended perlite is grayish-white. Both have the exact same properties so there is no need to choose one type over the other.
Perlite is non-toxic and makes good growing medium because it allows air and water to reach the roots of the plant without being blocked by it. The light weight also helps plants grow faster since they do not struggle to breathe when placed in perlite.