1. Arthropods and Echinoderms
Biology I: Chapter 28

2. ARTHROPODS

4. Arthropods Phylum Arthropoda Insects, crabs, centipedes, spiders
Segmented body
Tough exoskeleton made of chitin
Jointed appendages

5. Evolution of Arthropods
Fewer body segments
Highly specialized appendages for feeding, movement and other functions

6. Form and Function in Arthropods
Complex organ systems; some only found only in this phylum
Tracheal tubes (respiration)
Open circulatory system
Excrete wastes through saclike tubules

7. Feeding
Herbivores, carnivores, omnivores, bloodsuckers, filter feeders, detritivores, and parasites
Mouthparts have evolved to allow them to eat anything imaginable
Pincers or fangs to sickle- shaped jaws that can cut through the tissues of captured prey

8. Respiration: Terrestrial Arthropods
Tracheal tube: one of many branching, air- filled tubes that extend throughout the body
Spiracle: small opening located along the side of the body through which air enters and leaves the body
Book lung: organ that has layers of respiratory tissue stacked like the pages of a book: used to exchange gases

9. Respiration: Aquatic Arthropods
Respire through feather-like gills (i.e. lobster and crabs)
The horseshoe crab respires through organs: book gills

10. Circulation Open circulatory system
Well-developed heart pumps blood through arteries that branch and enter the tissues
Blood leaves the blood vessels and moves through sinuses, or cavities
The blood recollects in a large sinus surrounding the heart
It reenters the heart and is again pumped throughout the body

11. Excretion Terrestrial Arthropods
Malpighian tubules: sac-like organ that extracts wastes from the blood and adds them to feces that move through the gut
Aquatic Arthropods
Diffusion moves cellular wastes from the arthropod’s body into the surrounding water

12. Response Well-developed nervous system Brain
Sophisticated sense organs, (i.e. eyes and taste receptors)

13. Movement
Well-developed groups of muscles that are coordinated and controlled by the nervous system
Allows arthropods to beat their wings against the air to fly, push their legs against the ground to walk, or beat their flippers against the water to swim

14. Reproduction Terrestrial Arthropods Internal fertilization
Sperm or sperm packet
Aquatic Arthropods
Internal or external fertilization

15. Growth and Development in Arthropods
Molting
As the time for molting approaches, skin glands digest the inner part of the exoskeleton and other glands secrete a new skeleton
The animal pulls itself out of the remains of the original skeleton…this can take several hours
The new exoskeleton is soft and the animal is vulnerable to predators

16. Groups of Arthropods
Classified based on the number and structure of their body segments and appendages-particularly their mouthparts
Crustaceans
Spiders and their relatives
Insects and their relatives

17. Crustaceans 2 pairs of branched antennae 2-3 body sections
Mandibles: chewing mouthparts
Primarily aquatic
Examples: Crabs, shrimps, lobsters, crayfishes, and barnacles
Range in size from small terrestrial pill bugs to spider crabs that have masses around 20 kg

18. Crustaceans
Cephalothorax: region of a crustacean formed by the fusion of the head with the thorax
Thorax: body part of crustacean that lies just behind the head and houses most of the internal organs
Abdomen: posterior part of an arthropod’s body

19. Crustaceans
Carapace: the part of the exoskeleton that covers the cephalothorax
Mandible: mouthpart adapted for biting and grinding food
Cheliped: one of the first pair of legs of decapods (five pairs of legs: crayfishes, lobsters and crabs)
Swimmerets: flipper-like appendages used by decapods for swimming

20. Spiders and Their Relatives
Chelicerates
Mouthparts: chelicerae
2 body sections
4 pairs of walking legs
Horseshoe crabs, spiders, ticks, and scorpions

21. Horseshoe Crabs The oldest living arthropods
First appeared more than mya and have changed little since that time
Not true crabs at all! Anatomy is closer to that of spiders
Chelicerae, five pairs of walking legs, a long spike- like tail used for movement

22. Arachnids: Spiders The largest group of arachnids
Spin webs of a strong, flexible protein called silk
Do not have jaws for chewing: must liquefy food to swallow it

23. Arachnids: Spiders
Chelicerae: pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey
Pedipalps: pair of mouthparts in chelicerates that are usually modified to grab prey
Spinneret: organ in spiders that contains silk glands

24. Arachnids: Mites and Ticks
Small arachnids that are usually parasitic
Chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood or plant fluids
Mouthparts are so strong that if you try to pull off a tick the cephalothorax may separate from the abdomen and remain in your skin

25. Arachnids: Scorpions Widespread in warm areas around the world
Have pedipalps that are enlarged into claws
The long, segmented abdomen of a scorpion carries a venomous stinger that can kill or paralyze prey
Chew their prey using their chelicerae

26. Insects and Their Relatives
Uniramians have jaws, one pair of antennae, and unbranched appendages
A group that contains more species than any other group of animals living today
Wide variety of forms and lifestyles
Centipedes
Millipedes

28. Insects Have a body divided into three parts:
Head
Thorax
Abdomen
Three pairs of legs are attached to the thorax
Like all arthropods, insects have a segmented body, exoskeleton, and jointed appendages

29. Responses to Stimuli
Multiple of sense organs are used to respond to stimuli
Compound eyes
Chemical receptors for taste and smell on their mouthparts
Well-developed ears that hear sounds far above the human range

30. Adaptations for Feeding
Three pairs of appendages that are used as mouthparts, including a pair of mandibles
Adaptations for feeding are not restricted to their mouthparts
Many produce saliva containing digestive enzymes that help break down food

31. Movement and Flight 3 pairs of legs
Used for walking, jumping, flying, capturing and holding prey, etc.
The evolution of flight has allowed insects to disperse long distances and to colonize a wide variety of habitats

32. Metamorphosis
Incomplete metamorphosis: type of insect development characterized by a similar appearance throughout all stages of the life cycle
Nymph: immature form that lacks functional sex organs and other adult structures

33. Metamorphosis
Complete metamorphosis: type of insect development in which the larvae look and act nothing like their parents and also feed in completely different ways
Pupa: stage of metamorphosis in which an insect changes from a larva into an adult

34. Insects and Humans Many insects are known for their negative effects
Termites destroy wood structures, moths eat their way through wool clothing, etc.
Despite their association with destruction and disease, insects contribute to agriculture by pollinating 1/3 of the food that you eat
Produce commercially valuable silk, wax and honey

35. Insect Communication
Communicate using sound, visual, chemical, and other types of signals
Much of the communication involves finding a mate
Pheromones: specific chemical messengers that affect the behavior of development of other individuals of the same species

36. Insect Societies
Ants, bees, termites, and some of their relatives form complex associations called societies
Society: a group of closely related animals of the same species that work together for the benefit of the whole group
Caste: group of individual insects specialized to perform particular tasks, or roles

37. ECHINODERMS

39. Echinoderms Phylum Echinodermata Live only in the sea Spiny skin
Water vascular system
Tube feet: suction-cuplike structures
Endoskeleton: internal skeleton; hardened plates of calcium carbonate
Five-part radial symmetry

40. Form and Function in Echinoderms
The water vascular system, which is filled with fluid, carries out many essential body functions in echinoderms including respiration, circulation, and movement
Madreporite: sieve-like structure through which the water vascular system of an echinoderm opens to the outside

41. Feeding Several methods of feeding
Sea urchins use five-part jaw-like structures to scrape algae from rocks
Sea lilies use tube feet to capture floating plankton
Sea stars feed on mollusks by pushing the stomach out through the mouth

42. Respiration and Circulation
Other than the water vascular system, echinoderms have few adaptations to carry out respiration or circulation
In most species, the thin-walled tissue of the tube feet provides the main surface for respiration

43. Excretion Solid wastes are released as feces through the anus
Nitrogen-containing cellular wastes are excreted primarily in the form of ammonia
It is passed through the tube feet and skin gills

44. Response Do not have a highly developed nervous system
Most have a nerve ring that surrounds the mouth and radial nerves that connect the ring with the body sections
Most have scattered sensory cells that detect light, gravity, and chemicals released by potential prey

45. Movement
Most move by tube feet and thin layers of muscle fibers attached to their endoskeleton
Mobility is determined by the kind of endoskeleton

46. Reproduction Reproduce by external fertilization
The sexes are separate in most sea star species

47. Groups of Echinoderms 7000 species Sea urchins and sand dollars
Brittle stars
Sea cucumbers
Sea stars
Sea lilies and feather stars

48. Ecology of Echinoderms
Common in a variety of marine habitats
A rise or fall of echinoderms can cause major changes to populations of other marine organisms
Sea urchins control the distribution of algae and other forms of marine life
Sea stars are important carnivores that control the numbers of other organisms such as clams and corals