1. Ch Arthropods
Phylum: Arthropoda
Means “jointed legs”
75% of all animals belong to this phylum
Insects, lobsters, crabs, spiders, millipedes, & centipedes

2. Characteristics of Arthropods
1. Appendages – legs, antennae
2 appendages per segment
2. Open circulatory system
3. Digestive system
4. Ventral nervous system
5. Exoskeleton – protection & desiccation
Made of chitin

3. What is molting?
Shedding of the exoskeleton
Why do animals molt?
Every time an animal molts it enlarges or grows

4. What are some advantages & disadvantages of molting?
Protection, prevents desiccation
Must molt to grow, vulnerable after it molts

5. Crustacea subphylum
Crayfish, lobsters, crab, sow bugs, daphnia.
Mainly aquatic
Crayfish Characteristics
2 main body parts
1. Cephalothorax – head & thorax
2. Abdomen – 7 segments
Last segment is the telson

7. Appendages of the Crayfish
1. Chelipeds – pinchers
2. Antennules – smaller (inside)
3. Antenna – larger (outside)
4. Walking legs – 4 along the thorax
5. Swimmerets – along the abdomen
6. Uropod – outside the telson

8. Digestive & Excretory Systems
First the crayfish tears the food with their maxillae & maxillipeds.
They chew their food with their mandibles
The food passes through the esophagus to the stomach.

9. The digestive glands absorb nutrients, then the undigested material enters the intestine, and then exits the anus.
Green glands are also used in the excretory system to remove waste; much like kidneys.

10. Circulatory & Respiratory Systems
Open Circulatory System
Dorsal heart that pumps blood to the body cavity to bath the organs. It is then pumped to the gills.
What do the gills do?
Large surface area for gas exchange
The gills are attached to each walking leg

11. Nervous System
Ventral nerve cord
Brain
Sense receptors  antennules, antennae, & compound eyes
A compound eye has many lenses
Do you have a compound eye?

12. Usually mate in the fall
Reproductive System
Usually mate in the fall
The male uses its swimmerets to transfer sperm to the female, where she keeps the sperm until spring.
The eggs are then fertilized and kept along the female’s swimmerets until they hatch.

13. Chelicerae - subphylum
Class: Arachnida
Spiders, mites, scorpions
Many use stingers or fangs with poison.
How do spiders catch their prey?
with webs or “trap doors”
Scorpions hunt at night and hide during the day.

14. Only a few scorpions are poisonous to kill humans
Mites and ticks are the most abundant in this class.
Ticks are parasitic and some carry diseases.
Lyme’s disease
Rocky mountain spotted fever.
Spider mites can damage and wipe out fruit trees or other trees.

15. Structure of a spider
2 segments
1. Cephalothorax
2. Abdomen
Chelicerae – hollow fangs
Pedipaps – aid in chewing
8 legs & eyes
Spiracles – openings for respiration

16. Book lung – air sacs in the abdomen for respiration.
Malpighian tubules – kidney-like excretory system. Removes wastes.
Spinnerets – spins silk for webs
Can also be used as silk balloons to fly away in young spiders.
Black widow & Brown Recluse
2 poisonous spiders in Kansas

17. Uniramia - subphylum
2 classes
1. Diplopoda – millipedes
Means “thousand feet”
2 pair of legs per segment
2. Chilopoda – centipedes
Means “hundred feet”
1 pair of legs per segment
Some are poisonous