Those who are in need of information on arthropods

1. AP Biology
Invertebrate: Annelida
 Segmented worms
 earthworms, leeches
 segments
 increase mobility
 redundancy in body sections
 bilaterally symmetrical
 true coelem
fan worm leech

2. Phylum Annelida
Characteristics
• Protostomia, coelomates.
• Metamerism (= unspecialized
segmentation).

3. Annelida - Systems
• Integument - epidermis is one cell layer with mucous
gland that secrete a moist cuticle.
• Skeletal - hydrostatic (using coelom).
• Muscle - longitudinal and circular muscles.
• Each segments muscles are independent of the other
segments.
• Digestive - complete, complex, with typhlosole for
absorption and chloragogen cells acting as digestive
gland and excretory cells.

4. Annelida - Systems
• Excretory - a pair of nephridia per segment.
• Respiratory - through skin, some through parapodia;
tubeworms have gills.
• Circulatory - closed system (5 hearts), use hemoglobin as
oxygen carrier.
• Nervous - dorsal brain; ventral, double, solid nerve cord,
with ganglia in each segment.
• Endocrine - hormones secreted by nervous system.
• Reproductive -
• Dioecious in Polychaeta; no special organs, posterior
end becomes gonads.
• Monoecious in Oligochaeta and Hirudinea; Clitellium.

5. Annelid Body Plan
Setae

6. Class Polychaeta
• Class: Class Polychaeta (mostly Marine)
• Have many setae/bristles.
• Highly specialised head regions.
i Antennae.
ii Sensory palps.
iii Feeding appendages.
• Paired extensions of body (parapodia).
• Often tube-dwelling.
• Burrow into substrate and secrete mucus
materials.

7. Class Polychaeta

9. Class Oligochaeta

10. Class Oligochaeta
• Lack parapodia and have few setae.
• Lack the distinctive head region of polychaetes and
have no eyes.
• Scavengers that consume soil that contains organic
matter.
• The ingested soil moves into a storage chamber
called the crop, then to an area called the gizzard,
where grinding action breaks down the soil
particles.
• Undigested material passes out the anus in a form
called castings, which are prized as soil fertilizer.

11. Oligochaete Reproduction

12. Class Hirudinea
• Most live in fresh bodies of water, but some live among moist
vegetation.
• Dorso-ventrally flattened.
• Suckers found on both ends.
• Unlike other annelids, its segments are not separated internally.
• Leeches lack both setae and parapodia.
• Most are predators or scavengers (detritus feeders).
• Very few are parasites.
• They secrete anticoagulants, hirudin, to keep blood from
clotting and anesthetic that prevents the host from feeling their
presence.

13. Class Hirudinea - Anatomy

14. Importance of Annelids
• Earthworms eat decomposing organic material
and dig tunnels in the soil aerating the soil.
• They act as decomposers and as fertilizers too.
• Leeches suck blood and are parasitic but
medicinally this has been used in blood-letting
and reconstructive surgery of severed digits and
plastic surgery.
• The water based annelids bio-monitor the
marine environment.

15. Phylum Arthropoda

16. AP Biology
Invertebrate: Arthropoda
 Spiders, insects, crustaceans
 most successful animal phylum
 bilaterally symmetrical
 segmented
 specialized segments
 allows jointed appendages
 exoskeleton
 chitin (carbohydrate)
+ protein

17. AP Biology
Arthropod groups
insects
6 legs, 3 body parts
crustaceans
gills, 2 pairs antennae
crab, lobster, barnacles,
shrimp
arachnids
8 legs, 2 body parts
spiders, ticks, scorpions

18. Phylum Arthropoda
• includes spiders, scorpions, horseshoe crabs,
centipedes, crustaceans, insects.
• The largest and most diverse animal phylum.

19. Phylum Arthropoda
• Almost 2/3 of all species that have been
described are arthropods.
• There may be as many as 30,000,000 species
of insects alone.
• Abundant in all habitats, but dominate in
terrestrial habitats.
• Most arthropods are small, but a few may be
as large as 3.6 m.

20. Phylum Arthropoda
• Economical, environmental and health
importance:
• Pollination.
• Food source.
• Pests.
• Disease vectors.

21. Phylum Arthropoda
Taxonomy of Arthropods
• Arthropods divided into three
subphyla - based on appendages:
1. Chelicerata:
• first appendages are for feeding –
(chelicerae -fangs of spiders,
feeding appendages of horseshoe
crabs).
2. Mandibulata: Crustacea and
Uniramia (Tracheata):
• first appendages are antennae, first
feeding appendages are called
mandibles.
3. Trilobita:
• Extinct.

22. 22
Phylum Arthropoda - Alternate
Classification
1. Subphylum Trilobita
• extinct trilobites
2. Subphylum Chelicerata
• horseshoe crabs, spiders, ticks, mites, and some
extinct groups
3. Subphylum Myriapoda
• centipedes, millipedes
4. Subphylum Crustacea
• crabs, lobsters, shrimps, barnacles
5. Subphylum Hexapoda
• Insects

23. Chelicerates and Mandibulates

24. Mandibulates: Crustaceans and
Uniramians
• Mandibulates are divided into two major groups -
Crustaceans and Uniramians (Tracheata) - based on
appendages.
• Crustaceans have biramous (branched) appendages.
• Uniramians (insects, millipedes, centipedes) have
uniramous (unbranched) appendages.

25. Key Innovations of arthropods
• Jointed appendages - Arthropod (jointed feet).
• Jointed appendages are specialised for different functions:
legs, mouthparts, antennae.
• Joints in appendages make them highly functional for
walking, and grasping.
• Antennae are sensory - sounds and chemicals.
• Mouth parts specialised for different food sources.
• Exoskeleton, segmental body with specialisation of
body regions.

26. Arthropods – Breathing mechanisms
• Terrestrial Uniramians and some Chelicerates have trachea.
• Trachea are branched tubules that allow air to diffuse into the
body
• Smaller tracheoles bring air to individual cells.
• Air entry controlled through external spiracles and closing of
spiracles conserves water.
• Flow is mostly passive - muscular movements can increase
flow.
• Limits body size because all cells must be able receive oxygen.

27. Arthropod – Skeletal Support System
• Rigid exoskeleton, made of chitin and protein helps
to protect organism against predators.
• Reduces desiccation (water loss) - allows life in dry
environments.
• Skeleton functions as attachment for muscles.
• Exoskeleton limits arthropods maximum size
although chitin is tough, it is brittle and cannot
support great weight without increasing its thickness
greatly.
• Exoskeleton must be shed in order for increase in size.

28. Arthropod - Moulting
• Growth requires periodic moulting - liability.
• New exoskeleton grows beneath old one
separated by a fluid that dissolves
components of old skeleton.
• Old skeleton cracks open and is shed.
• New skeleton is soft and must be expanded to
full size.
• Hardens with exposure to air or water.

29. Arthropods - Segmentation
• Segmental body plan clear in all forms.
• Segments fused to form specialised body regions.
• Insect: head, thorax, abdomen.
• Crustacean: cephalothorax, abdomen.

30. Arthropods - Eyes
• Ocelli are simple eyes with single lenses.
• Sometimes occur together with compound eyes.
• Function in distinguishing light and dark.
• Compound eyes: composed of many ommatidia.
• Each ommatidium receives its own image.
• it is connected to a nerve cell - entire image is integrated
in the brain.

31. Arthropod – Digestive system
• Gut is tubular and extends from mouth to
anus - with specialization: - crop, stomach
(midgut), hindgut, intestine, rectum.

32. Arthropod Circulatory system
• Circulatory system is open.
• Heart extends through thorax and abdomen.
• Contraction sends blood forward and
relaxation draws blood from tissues.
• One-way valves in heart allows blood to flow
forward only.
• Blood from anterior end flows through tissues
to posterior end.

33. Arthropods – Respiratory system
• Crustaceans have feathery gills under
carapace.
• Chelicerates have book gills and book lungs -
series of plates with thin respiratory
epithelium.

34. An efficient system that conserves water
- a good adaptation for terrestrial life
Arthropods - Excretion
• Several forms of excretory systems.
• Terrestrial Uniramians have Malpighian tubules.
• Slender tubular projections off the digestive tract at the junction of
the midgut and hindgut.
• Water and solutes pass through walls of tubules, nitrogenous
wastes are precipitated as uric acid.
• Fluid with waste is emptied into hindgut and eliminated.
• Most water and valuable solutes reabsorbed by hindgut.

35. Arthropods – Nervous System
• Double chain of ganglia runs along ventral surface.
• Three fused pairs of dorsal ganglia form the brain.
• Ventral ganglia control local activity of body regions.
• Many activities continue with brain removed.
• Some activities begin spontaneously when head is
removed.

36. Subphylum Chelicerata
Three Classes of Chelicerates
• Class Arachnida - spiders, scorpions, ticks
• Class Merostomata - horseshoe crabs
• Class Pycnogonida - sea spiders

37. Class Arachnida
• Spiders, daddy longlegs, scorpions, mites & ticks.
• All have a pair of chelicerae, pair of pedipalps, four pairs of
legs.
• Chelicerae are first appendages, fangs with poison glands.
• Pedipalps are next, similar to legs - rarely used for locomotion
often used for catching and handling prey.
• may also chew with basal portion.
• may function as copulatory organs or sensory organs.
• Scorpion pincers are pedipalps.

38. Class Arachnida
• Most are carnivorous, some mites are herbivorous.
• Most ingest only liquified foods, digestion begins externally.
• Most are terrestrial, direct transfer of sperm for reproduction.
• Respire with trachea, book lungs or both.

39. Class Merostomata
Horseshoe Crabs e.g.: Limulus sp, common on North Atlantic
coasts.
• Ancient group - Limulus fossils date to 220 million years old.
• Live in deep water, migrate to shallow coastal waters to
mate.
• Feed at night on molluscs and annelids.
• Shell-like carapace over cephalothorax protects most body
parts.
• Possess four pairs of walking legs, chelicerae and pedipalps.
• Respire via five pairs of book gills.

40. Class Pycnogonida
Sea Spiders.
• Common in marine habitats, especially
in cool waters.
• Rarely observed because of small size.
• Not closely related to spiders.
• Adults are parasites or predators on
other animals.
• Have sucking proboscis with terminal
mouth.
• Body consists mostly of cephalothorax,
no well-defined head.
• Possess four to six pairs of legs.
• Males exhibit parental care of young,
carry eggs on legs.

41. Subphylum Mandibulata
Class Crustacea – Crustaceans.
• Includes shrimp, crabs, crawfish, lobsters,
pillbugs, copepods, brine shrimp and
barnacles.
• Have biramous (two branch) appendages.
• Have two pairs of antennae.
• 3 pairs of feeding appendages.
• Larger forms have feathery gills near base of
legs.

42. Class Crustacea
• Have legs on thorax and abdomen like millipedes and
centipedes.
• Unlike insects crustaceans have two pairs of
antennae.
• Many have compound eyes.
• Have tactile (touch sensitive) hairs over whole body.
• Excretion of nitrogen wastes occurs mostly across
surface of cuticle.
• Variety of sexual styles and care of young.

43. Crustacean Diversity
• Decapod ("ten-footed") Crustaceans -
• includes lobsters, shrimp, crabs, crawfish.
• Exoskeleton reinforced with calcium carbonate.
• Anterior segments fused into cephalothorax, covered by
carapace.
• Crushing pincers common, used to obtain food and in
defence.
• Swimmerets used in reproduction and locomotion.
• Snapping of telson and uropods causes forceful, rapid
movement to the rear.

44. Crustacean Diversity
• Terrestrial forms - pillbugs, sowbugs, isopods.
• Amphipods are both terrestrial and aquatic.
Planktonic crustaceans:
• Subclass: Copepods (Copepoda).
• Subclass: Water fleas (Cladocera).
• Subclass: Ostracods (Ostracoda).
• Fairy shrimp and brine shrimp (Anostracoda).

45. Subphylum Uniramia
Uniramia (or Tracheata) - has three classes:
• Class Chilopoda – centipedes.
• Class Diplopoda – millipedes.
• Class Insecta – insects.
• Well adapted to terrestrial life.
• Respire with trachea.
• Malpighian tubules for excretion.
• Waxy cuticle on exoskeleton.

46. Classes Chilopoda and Diplopoda
Centipedes and Millipedes - both have head
tagmata followed by numerous repeating
segments - each with paired appendages.
• Centipedes (hundred legs) - have one pair of
legs per segment.
• Millipedes (thousand legs) - have two pairs of
legs per segment.

47. Class Chilopoda and Diplopoda
• Centipedes - carnivorous, most eat insects.
• Appendages of first body segment are poisonous
fangs.
• Millipedes - most are herbivorous.
• Can roll bodies into a flat coil.
• May secrete defensive fluids and cyanide gas.
• Reproduction similar in both groups.
• Sexes separate, fertilization is internal, copulate to
transfer sperm, all species lay eggs.
• Juveniles are similar to adults in appearance.

48. Class Insecta
Class Insecta – Insects.
• Largest group of organisms on earth - with
great diversity.
• Especially numerous in the tropics.

51. Class Insecta
• Most are terrestrial but many are aquatic in
freshwater.
• Have three body segments: Head, thorax,
abdomen.
• Have three pairs of legs, all attached to thorax.
• Have one pair of antennae.
• May have one or two pairs of wings.
• Sexes separate with internal fertilisation.
• Wings arise as sack-like outgrowths.
• Wings are solid except for veins.

52. Class Insecta
• Digestive tract is tubular and slightly coiled
digestion occurs within stomach or midgut.
• Excretion by Malpighian tubules.
• Respiration via trachea that extend
throughout body.
• Spiracles can be closed by muscles to retard
water loss.

53. Class Insecta
• Possess wide variety of sensory systems - in addition
to eyes.
• Sensory hairs located all over bodies especially on
legs and antennae.
• Sounds detected by tympanum.
• Sensory hairs may also detect sound waves.
• Produce sounds which may be inaudible to humans.
• Chemicals (pheromones) are also used to
communicate.

54. Class Insecta - Development
• Most insects hatch from laid eggs - rarely develop
within mother.
• After hatching young insects undergo development
through a series of instars.
• Often the larva is very different from the adult and
undergoes metamorphosis to become adult.
• Development is either through simple
metamorphosis or incomplete metamorphosis.

55. Class Insecta
Incomplete metamorphosis (Hemimetabolous
development).

56. Class Insecta
Complete metamorphosis (Holometabolous
development)