Arthropods are characterized by their jointed exoskeleton and limbs, and segmented bodies. They include insects, arachnids, crustaceans, and extinct groups like trilobites. The largest phylum of animals, arthropods have adapted to nearly all environments. Their success is due to traits like their tough exoskeleton, segmented body, and jointed legs adapted to many modes of life.

2. An arthropod is
an invertebrate animal having
an exoskeleton (external skele
ton), a segmented body, and
jointed appendages.
Arthropods are members of
the phylum Arthropoda (fro
m Greek árthron, "joint", and
pous (gen. podos), i.e. "foot"
or "leg", which together mean
"jointed leg"), and include
the insects, arachnids,
and crustaceans.

3. Arthropods
are invertebrates with segmented
bodies and jointed limbs. The
limbs form part of
an exoskeleton, which is mainly
made of α-chitin, a derivative
of glucose. One other group of
animals, the tetrapods, has
jointed limbs, but tetrapods
are vertebrates and therefore
have endoskeletons.

4. Phylum called Arthropoda
(arthropods)
is the largest and most successful
of the animal phyla. All arthropods
have segmented bodies divided
into
a head, jointed legs and abdomen.

5. Arthropods are characterized by
their jointed limbs and cuticles,
which are mainly made of α-
chitin; the cuticles of crustaceans
are
also biomineralized with calcium
carbonate. The rigid cuticle
inhibits growth, so arthropods
replace it periodically
by moulting.

6. They are important members of
marine, freshwater, land and
air ecosystems, and are one of
only two major animal groups
that have adapted to life in dry
environments; the other
is amniotes, whose living
members
are reptiles, birds and mammals
.

7. Head
_______________________
Thorax
_______________________
Abdomen

8. = Body
= Coxa (base)
= Gill branch
// = Gill filaments
= Leg branch
Structure of
a biramous appendage[13]

9. Basic arthropod body structure
= heart
= gut
= brain, nerve cord, ganglia
O= eye

10. Arthropod bodies are also segmented
internally, and the nervous, muscular,
circulatory, and excretory systems
have repeated components.
Arthropods come from a lineage of
animals that have a coelom, a
membrane-lined cavity between the
gut and the body wall that
accommodates the internal organs.

11. Arthropods have open circulatory
systems, although most have a few
short, open-ended arteries.
The heart is typically a muscular tube
that runs just under the back and for
most of the length of the hemocoel.

12. Arthropods have a wide variety of
respiratory systems. Small species
often do not have any, since their
high ratio of surface area to volume
enables simple diffusion through the
body surface to supply enough
oxygen.

13. Living arthropods have paired main nerve cords
running along their bodies below the gut, and
in each segment the cords form a pair
of ganglia from
which sensory and motor nerves run to other
parts of the segment.
The brain is in the head, encircling and
mainly above the esophagus. It consists of the
fused ganglia of the acron and one or two of
the foremost segments that form the head.

14. The stiff cuticles of arthropods would block out
information about the outside world, except
that they are penetrated by many sensors or
connections from sensors to the nervous
system.
Head of a wasp with three ocelli (centre), and compound eyes at the left and right

15. Their vision relies on various
combinations of compound eyes and
pigment-pit ocelli: in most species
the ocelli can only detect the
direction from which light is coming,
and the compound eyes are the main
source of information, but the main
eyes of spiders are ocelli that can
form images and, in a few cases, can
swivel to track prey.

16. Chemical sensors provide equivalents
of taste and smell, often by means of
setae. Pressure sensors often take the
form of membranes that function
as eardrums, but are connected directly to
nerves rather than to auditory ossicles.
The antennae of most hexapods include
sensor packages that monitor humidity,
moisture and temperature

17. Compsobuthus werneri female with young (white)

18. A few arthropods, such as barnacles,
are hermaphroditic, that is, each can
have the organs of both sexes.
However, individuals of most species
remain of one sex all their lives.
A few species
of insects and crustaceans can
reproduce by parthenogenesis.

19. Aquatic arthropods may breed by external
fertilization, internal fertilization, where
the ova remain in the female's body and
the sperm must somehow be inserted
All known terrestrial arthropods use internal
fertilization, as unprotected sperm and ova
would not survive long in these environments.
On the other hand, many
male terrestrial arthropods
produce spermatophores, waterproof packets of
sperm, which the females take into their bodies.

20. The nauplius larva of a prawn
Most arthropods lay eggs, but scorpions
are viviparous: they produce live young after
the eggs have hatched inside the mother, and
are noted for prolonged maternal care.

22. The segmented bodies are
arranged into regions, called
tagmata (e.g., head, thorax,
abdomen).
The paired appendages (e.g.,
legs, antennae) are jointed.
They posses a chitinous
exoskeletion that must be shed
during growth.

23. A hard outer body covering
called an exoskeleton.
They have bilateral symmetry.
The nervous system is dorsal
(belly) and the circulatory
system is open and ventral
(back)
Specialized mouth parts.
Segmented body

24. EXOSKELETON SPECIALIZED
MOUTH PARTS
JOINTED LEGS COMPOUND
EYES
SEGMENTED
BODY

27. The major Classes of living arthropods
are as follows with one example each:
Class Arachnida - spiders
Class Crustacea - crabs
Class Diplopoda - millipedes
Class Chilopoda - centipede
Class Insecta or Hexopoda - insects
Class trilobites are an extinct group of
arthropod

28. Trilobites (meaning "three
lobes") are a well-known
fossil group
of extinct marine arthropo
ds that form
the class Trilobita.
Trilobites form one of the
earliest known groups of
arthropods.
Kainops invius,
early Devonian
Paradoxides sp.,
late Cambrian

29. Class trilobites are an extinct group of
arthropods that lived in the seas of the world
for about 380 Mya (million years ago), from
the Precambrian 610 Mya to around the end of
the Permian 230 Mya.
Trilobites finally disappeared in the mass
extinction at the end of
the Permian about 250 million years ago. The
trilobites were among the most successful of
all early animals, roaming the oceans for over
270 million years.[2]

30. Trilobites had many life styles;
some moved over the sea-
bed as predators, scavengers or filter
feeders and some swam, feeding
on plankton.
Most life styles expected of modern marine
arthropods are seen in trilobites, with the
possible exception of parasitism (where
there are still scientific debates).

32. Class Arachnida (uh-
rak�-nid-uh), spiders,
ticks, mites, scorpions
and others.
This is a diverse class
which belongs to a
subphylum of the
Arthropoda known as
the Chelicerata.

33. Chelicerata are characterized as having
two distinct body regions, a
cephlothorax and an abdomen.
Chelicerates have six pairs of
appendages, the first two pairs being
mouthparts and the following four
pairs being legs.
They do not have antennae.

34. The first pair of mouthparts are the
chelicerae (sing., chelicera).
They are three-segmented and pincher-
like.
The second pair of mouthparts are the
six-segmented pedipalps.
They may appear leg-like (spiders) or
claw-like (scorpions).

36. CHILOPODA
• Class Chilopoda (chi-lo-po�-da),
the centipedes.�
• Two tagmata (head and trunk)
• One pair of antennae with 14 or more
segments
• One pair of legs per trunk segment

37. • Mouthparts: one pair of mandibles and two
pairs of maxillae
• Appendages on the first trunk segment are
clawlike poison jaws or fangs with which
centipedes paralyze their prey.
• The class name refers to the lip- like
appearance of the fused bases of these
appendages.
• Eyes may be present or absent.

38. • Centipedes are elongate and flattened.� They
are usually found in somewhat protected
places, such as in leaf litter, in the soil, under
bark, or in rotten logs.
• One species is commonly found in houses and
other buildings.

39. • Centipedes are predatory and feed on insects,
spiders, and other small animals.�� The
larger centipedes can bite humans, but the
bite is not serious and is no more painful that
the sting of a bee or wasp.� The common
small centipedes of Nebraska are harmless to
man. Overall, centipedes are beneficial natural
enemies of insects.

41. DIPLOPODA
• Class Diplopoda (dip-low-po�-da),
the millipedes.�
• Two tagmata (head and trunk)���
• One pair of antennae, usually having seven
segments��

42. • Two pairs of legs on most trunk segments (30
or more pairs total)
• Mouthparts: one pair of mandibles, and one
pair of maxillae
• Eyes are usually present

43. Millipedes are usually cylindrical (sometimes
slightly flattened).� Except for the first three
trunk segments, each segment has two pairs
of short legs.� Millipedes are found in damp
places such as the soil, leaf litter, or under logs
and stones.

44. Most millipedes are beneficial scavengers of
decaying plant material.� A few attack living
plants and are sometimes pests.� Even fewer
are predacious.
Millipedes do not bite man, but many give off a
foul-smelling fluid containing hydrogen
cyanide which can be strong enough to kill
insects placed in a jar with a millipede

46. INSECTA
• Class Insecta (in�- sec-ta), the insects.��
•
• Three tagmata (head, thorax and
abdomen)�
• One pair of
antennae���������������
������������������
• Three pairs of
legs�����������������
�������������������

47. • May have wings, either one or two pairs
• Insects are the most abundant life form now
known to science.� Around 1,000,000
species have been described and
named.� That is more than all the other
known animals put together.

48. The subphylum Hexapoda (from the Greek for six
legs) constitutes the largest (in terms of number
of species) grouping of arthropods and includes
the insects as well as three much smaller groups
of wingless arthropods: Collembola, Protura,
and Diplura (all of these were once considered
insects). The Collembola (orspringtails) are very
abundant in terrestrial
environments. Hexapods are named for their
most distinctive feature: a consolidated thorax
with three pairs of legs. Most other arthropods
have more than three pairs of legs.