18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton –Various...
Transcript of 18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton –Various...
•18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton
– Various adaptations have made arthropods the most successful animals on Earth
• Jointed appendages adapted for different functions
• Exoskeleton: external skeleton that protects and provides attachment points for muscles
• Distinct groups of segments: head, thorax, abdomen
• Open circulatory system
LE 18-11a
Cephalothorax Abdomen
Head Thorax
Antennae(sensoryreception)
Head
Pincer (defense) Mouthparts (feeding)
Walking legs
Swimmingappendages
– Chelicerates• Horseshoe crabs• Arachnids, such as spiders, scorpions, mites, and
ticks• Most live on land and are carnivores
– Millipedes and centipedes• Have similar segments over most of body• Segments bear two pairs (millipedes) or one pair
(centipedes) of legs
– Crustaceans• Nearly all are aquatic• Include lobsters, crabs, shrimps, barnacles,
small copepods, and krill
•18.12 Insects are the most diverse group of organisms
– Insects have a number of common features• Three-part body consisting of head, thorax, and
abdomen– Head usually has antennae and eyes
• Mouthparts specialized for particular kinds of eating• Three sets of legs• One or two pairs of wings (most, but not all)
LE 18-12a
Head Thorax
Hindwing
Antenna
Eye
Mouthparts
Abdomen
Forewing
•18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement
– Echinoderms, phylum Echinodermata, are slow-moving or sessile marine animals
• Include organisms such as sea stars, sand dollars, and sea urchins
• Adults are radially symmetrical• External bumps or spines are extension of hard
endoskeleton
– The water vascular system is unique to echinoderms
• Network of water-filled canals that branch into tube feet
• Suction cup–like tube feet used for feeding, gas exchange, and locomotion
– Embryonic features such as bilateral symmetry places echinoderms on the same clade as chordates
LE 18-13a
Stomach
Anus
Canals
Tube feet
Spines
LE 18-13b
Tube foot
LE 18-13c
Tube foot
Spine
•18.14 Our own phylum, Chordata, is distinguished by four features
– Four distinctive features appear in the embryos, and often in the adults, of chordates, phylum Chordata:
• A dorsal, hollow nerve cord• A stiff notochord• Pharyngeal slits• A muscular post-anal tail
– The simplest chordates are tunicates and lancelets
• Marine invertebrates that use pharyngeal slits for suspension feeding
• Tunicates: small, saclike; adhere to rocks and reefs; likely represent the deepest branch of the chordate lineage
• Lancelets: small, bladelike; live in marine sands; closest living relatives of the vertebrates
LE 18-15
Ancestral chordate
Head
Lungs or lung derivatives
Vertebral column
Brain
Jaws
Lobed fins
Legs
Amniotic egg
Milk
Mam
mal
s
Rep
tile
s
Am
ph
ibia
ns
Lo
be-
fin
s
Ray
-fin
ned
fis
hes
Sh
arks
, ra
ys
Lam
pre
ys
Hag
fish
es
Lan
cele
ts
Tu
nic
ates
Chordates
Craniates
Vertebrates
Jawed vertebrates
Tetrapods
Amniotes