Arthropods
Arthropods are a class under invertebrates animals,Arthropods has around 1.2 million type
of species(does not include the species already extinct),which is 80% of the species in the
whole animal kingdom,except for ​Trilobitomorpha,which is already extinct,​Arthropods can be
divided into 4 classes(​Chelicerata​,​Crustacea​,​Myriapoda​ and ​Insecta​)some characteristics
about them are like body divided into segment,jointed legs and though exoskeleton.
Trilobitomorpha
Is the origin species of Arthropods that already extinct,though Fossil,our human discover
around 4000 different types of fossil for Trilobitomorpha,and we also know that they all live
in the shallow sea area
Chelicerata
A main type of Arthropods,some examples like horseshoe crabs,​Scorpion,spiders and
mites.and it has many type(​Merostomata,Arachnida and Pycnogonida)
Merostomate and Pycnogonida lives in water,don’t have too much to talk about it
Arachnids​ are the main group in Chelicerata it is the second largest type in the whole
Arthropods,around 60000 types,some common one like Scorpion.spider and mit,main
characteristics are 2 segments,4 pair of legs,No antennae,simple eyes,the early arachnids
are also lives in water,arachnids start to move to land at Devonian,now,most of Arachnids
are on land,and some of them evolved some organ for attacks and defenses like Venom
gland and silk gland.
Crustacea
Crustacea has around 30000 different species,characteristics are like 2 segment(very less
has 3)cephalothorax and abdomen,5 or more pairs of limbs,compound eyes and 2 pairs of
antennae.eg.crab lobster and otter
Crustacea mostly live in the ocean,very little has invaded to leak and somewhere have
water,and crustacea is also a main part of the food web in water.and very little amount of
them can get on land,but still have to be in a damp environment eg.Crab
Myriapoda
Basically centipedes and millipedes, characteristics are like many segments,for centipedes,1
leg per segment and two legs per segment for millipedes,simple eyes and on pair of
antennae
Both centipedes and millipedes need a damp environment to survive,so they usually where
found underground
Insecta
The largest group of the whole animal kingdom,both the type and number of species, there
are about one million types of insects that we know,and there are more waiting for people to
discover,the old name of Insecta is Hexapoda,which means there are 6 legs for
insects,some other characteristics like 3 segment,normally there will be two pairs of
wings,and there will be 1 pair of antenna(very less have none antenna),some special place
about insects is that because the outshall of Insecta is kind of thick,so it will stable the
largest size of insects,if insects want to break the shell,they will have to go through the
process of peeling,a life of insects have to go through about 5 - 15 times of peeling,it
depends on the type of insects,we also know that snake will peel off their skin,but the
difference is that insects peel skiing for growth,but snakes peel skin just because is one of
the Physiological phenomenon