arthropods. insects, spiders, crabs, and lobsters are all arthropods, so there are a lot of...
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ARTHROPODS
Insects, spiders, crabs, and lobsters are all arthropods, so there are a lot of arthropods on Earth. The earliest arthropods on Earth developed about 550 million years ago.
History
Their ancestors were a kind of worm that was divided
into segments, probably distantly related to annelid
worms. These worms probably had two antennae on
their heads, and a pair of eyes. They probably had
several head segments, at least one body segment
with several pairs of legs, and a tail segment.
Then these worms developed hard exoskeletons and became the arthropods. This hard shell protected them and helped them to survive. But their shells don't grow along with them, and so all arthropods have to shed their shell as they get bigger and grow a new one. Because of this most arthropods don't get very big.
Most of them are tiny insects or spiders, although some crabs and lobsters can weigh up to about twenty pounds.
Around 350 million years ago, some of the insects living on land began to fly, like modern flies or dragonflies or grasshoppers. When flowering plants appeared, about 200 million years ago, some arthropods, like bees, evolved to eat their pollen, and the bees and the flowers worked out a relationship that is good for both the bees and the flowers, where the bees help the flowers to reproduce.
Classification
Arthropods are divided into four main groups: Insects
Spiders
Crustacreans
Millipeds
Arthropods are a very diverse group, but they share some basic characteristics:
All arthropods have jointed legs and a head and segmented body parts called the thorax and abdomen.
An arthropod’s body is covered by a shell or a hard outer skin called an exoskeleton. It is made of a material called chitin.
Importance of Arthropods
Life on Earth would end very quickly without arthropods. Arthropods are great recyclers and decomposers and they are a super food source. They also help pollinate the plants that provide food and keep the air and water clean.
Crustaceans
A crustacean is an arthropod that has a hard, exoskeleton, two pairs of antennae, and a mouth for crunching and grinding.
Crustaceans can re-grow certain parts of their body.
Most crustaceans live in water and get oxygen from the water through gills.
Centipedes & Millipedes
Centipedes: Have one pair of legs in each segment Are carnivores and eat other animals To capture its prey, centipedes poison their
prey with their claws Centipedes are found in wet places like
under rocks and in the soil
Millipedes Have two pairs of legs for each segment Eat plants When scared, they roll up into a small ball
to protect itself Do NOT have claws Live in wet places such as under rocks and
in the soil
Spiders
Spider, ticks, scorpions, and mites ALL have 8 legs Their bodies are divided into a HEAD
region, CHEST, and STOMACH
Spiders
Most spiders eat bugs (insects), while some can eat very small vertebrates such as hummingbirds
Spiders make webs of silk. Silk is a thread material that is made in a spider’s stomach.
Spiders
Spiders can catch their prey in a few ways:
By trapping them in webs
Hide from their prey and them jump out
and catch their prey
Bite the prey and poison it
Insects
There are more insects in the world than there are total animal species all together
Insect bodies are divided into 3 parts: HEAD, CHEST and STOMACH
Insects have 6 legs
Insects go through METAPHORESIS
Insect Defense
Insects can protect themselves using stingers, or camouflage