Scientists have found many trilobite fossils three pairs of legs a segmented body including a head thorax and abdomen and one pair of antennae Most adult insects also have wings BEFORE BUGS Half a billion years ago there were no insects Planet Earth looked very different On land there were no animals Nothing flew in the sky No trees flowers or grass grew But in the ocean life was abundant Algae floated on the ocean surface providing food for the marine life below Strange creatures called trilobites looked like giant pill bugs They lurked on the muddy seafloor
in the shallow water alongside sea snails starfish and sea urchins Massive eurypterids or sea scorpions grew up to six feet 2 m long and terrorized the sea Eurypterids hunted for prey by grabbing it with their powerful claws They were the top of the food chain in a world where there were no vertebrates animals with backbones to compete with The period of life on Earth when these animals evolved beginning approximately 541 million years ago MYA is called the Cambrian explosion Prior to the explosion there were no animals with legs or eyes There were no predators Primitive multicelled organisms floated through the water passively absorbing nutrients Scientists studying oxygen levels in prehistoric rocks believe there may have been a small increase CAMBRIAN EXPLOSION Life on Earth began 3.8 billion years ago when the first molecules capable of replication developed But it wasn't until the Cambrian explosion 541 MYA that life took off It's described as an explosion because many new species of animals evolved in a relatively short period of time But despite its name this evolution didn't happen in a flash The Cambrian explosion lasted ten million years Because many fossils have been discovered from this period of time scientists believe there was an evolutionary explosion Before this period the fossil record was sparse Fossils found in the Burgess Shale a fossil deposit in what is now British Columbia Canada from 505 MYA show creatures recognizable as arthropods and worms So a rapid period of evolution must have occurred by then The Burgess Shale used to be 670 feet 200 m underwater The deposit formed 515 MYA when underwater mudslides swept creatures over a cliff and instantly buried them creating fossils As well as preserving hard shelled arthropods the rapid burial preserved soft bodied creatures that usually decomposed
in available oxygen This caused more predators to evolve so their prey also had to evolve quickly to adapt and survive in a world where they could be hunted and eaten Scientists believe most of the animals alive on Earth today descend from the creatures that evolved during the Cambrian explosion ARTHROPODS MOVE TO LAND Trilobites and sea scorpions are classified as part of a group of animals called arthropods Scientists split up the known animal kingdom into groups called phyla The animals in the Arthropoda phylum have segmented bodies jointed legs and hard exoskeletons that protect them like armor The Arthropoda phylum is further split into several different groups called classes Crustaceans such as crabs and lobsters make up one class Spiders are in the Arachnida class And insects make up the Insecta class Within each class are different orders For instance the order Lepidoptera within the insect class contains all the butterflies and moths Approximately 500 MYA the first plants made their way onto land Algae started to grow on shores taking root and becoming rigid enough to stand upright and collect more sunlight Algae continued to develop into green mosses ferns and horsetails These early plants provided homes and food for the first creatures that also moved from water to land The early land
CLASSIFICATION Honey Bee Apis mellifera DOMAIN Eukaryota This domain includes plants animals and fungi These organisms are grouped together because their cells each have a nucleus a cell structure that contains the DNA KINGDOM Animalia All animals including mammals and insects are in this group PHYLUM Arthropoda Organisms in this phylum have an exoskeleton and segmented bodies CLASS Insecta This class contains insects whose bodies have three segments the head thorax and abdomen They also have three pairs of legs that they use for walking ORDER Hymenoptera This order contains insects including ants bees saw flies and wasps FAMILY Apidae Bees make up this family GENUS Apis This family contains nine bee species that may all at times be called honey bees SPECIES mellifera Honey bees are the only domestic species of bee They are the only Taxonomic classification is the science of identifying living things grouping them together and naming them When this is done each organism is assigned a place in eight different categories ranging from domain the most general category to species the most specific category When the scientific name of an animal is given it includes the genus which is capitalized and the species which is not Honey bees are Apis mellifera Scientific names are often abbreviated after first use A. mellifera 9
