1. Animals 2 Echinoderms and Chordates
Chapter 31

2. Body Plan Formation
Distinguished on the basis of how the openings into the gut are formed.
Initially only a single opening into the digestive tract, the blastopore which develops into mouth or anus.
Protostomes
blastopore becomes the mouth and a new opening forms the anus.
Molluscs, Annelids, and Arthropods
Deuterostomes
blastopore forms the anus, and a new opening forms for the mouth.
Echinoderms and Chordates

3. Phylum Echinodermata: Characteristics
All saltwater aquatic organisms
Endoskeleton of spiny plates
Spines protrude through skin
Many have radial symmetry
Larval stage often bilaterally symmetrical
Very diverse group
Sea lilies- class Crinoidea
Sea cucumbers-class Holothuroidea
Brittle stars-class Ophithuroidea
Sea urchins and sand dollars- class Echinoidea
Sea stars- class Asteroidea

4. Echinoderm diversity
Fig. 31.1

5. Echinoderms: Class Asteroidea
Sea stars
Found along shorelines on rocky surfaces
Body Structure
5-armed body
Mouth on underside
Oral Surface
On oral surface, each arm has an ambulacral groove surrounded by tube feet
Anus on upper side
Aboral Surface (def’n: away from mouth)
Each arm has a coelomic cavity with digestive glands and gonads

6. Echinoderms: Class Asteroidea
Structures project through skin
Spines for protection
Pedicelleriae around base of each spine, keep body surface free of debris
Skin gills-extensions of skin for gas exchange

7. Echinoderms: Class Asteroidea cont’d.
Feeding
Opens bivalve prey with its tube feet
Cardiac stomach extends out through open shell and releases enzymes
Digested food taken in and digestion completed in pyloric stomach
Intestine is very short and terminates at anus on upper surface
Nervous system-no central brain
Central nerve ring gives off branches to each arm
Eyespot at tip of each arm

8. Echinoderms: Class Asteroidea cont’d.
Locomotion:
Water vascular system controls movement of tube feet
Water enters through madreporite on aboral side
Madreporite leads into stone canals, and these lead into radial canals in each arm
Water is pumped into tube feet by the ampulla which lie along ambulacral groove on each arm
Suction is created by each small foot

9. Echinoderms: Class Asteroidea cont’d.
Reproduction is both sexual and asexual
A body fragment, if large enough, can regenerate an entire animal
Gonads produce gametes, at fertilization a dipleura larva is produced
Bilateral symmetry in larva

10. Sea star anatomy and behavior
Fig. 31.2

11. Phylum Chordata: Development
Common features of Chordates:
Notocord-dorsal rod for support
In all Vertebrates this becomes the spinal column
Dorsal tubular nerve cord
Contains a canal filled with fluid
In vertebrates it is protected by the spinal column
Pharyngeal pouches
Only present in embryonic development in most vertebrates
Become gills in invertebrate chordates, fishes, and some amphibian larvae
In terrestrial vertebrates they are modified for other purposes
Humans-auditory tubes, tonsils, thymus and parathyroid glands
Post-anal tail

12. Chordates: Evolutionary Trends
Invertebrate chordates
Tunicates and lancelets
Vertebrate chordates
Fishes
Cartilaginous fish-first to develop jaws
Some early bony fish had lungs
Amphibians
first to have jointed appendages and invade land
Reptiles, birds, mammals
Terrestrial adaptations for reproduction
Reptiles, birds- amniotic egg for development outside the body
Mammals- placenta and internal development

13. Evolutionary tree of chordates
Fig. 31.4

14. Chordates: Invertebrates
Subphylum Urochordata
Tunicates-the sea squirts
Larva is bilaterally symmetrical and has 4 chordate characteristics
Adults are sessile, thick-walled, sac-like organisms
The only chordate characteristics in the adults are pharynx and gill slits
Have an outer tunic and 2 siphons which can squirt water
Live in ocean and are filter-feeders
Possibly a tunicate larva became sexually mature and gave rise to a fish-like vertebrate?

15. Anatomy of a tunicate
Fig. 31.5

16. Chordates: Invertebrate cont’d.
Subphylum Cephalochordata
Lancelets
Knife-shaped bodies a few centimeters long
Live in shallow coastal waters
Retain all 4 chordate characteristics as an adult
Segmentation is present
Muscles are segmentally arranged
Nerve cord has branches

17. Habitat and anatomy of a lancelet, Branchiostoma
Fig. 31.6

18. Phylum Cordata: Subphylum Vertebrata
Overview
Have 4 chordate characteristics at some point in life
Distinguishing features
Living endoskeleton of cartilage or bone
Closed circulatory system with pumping heart
Paired appendages
Efficient respiration and excretion of wastes
High degree of cephalization with well-developed sense organs

19. Vertebrates: Fish Overview
3 groups of fishes: jawless, cartilaginous, bony
First jaws and lungs
Cartilaginous and bony have true jaws with teeth
Evolved from first pair of gill arches
2nd pair of gill arches form support structures for jaws
Jaws allow predatory way of life
Adapted to life in water
Sperm and eggs released into water, fertilization external
Zygote develops into swimming larval form
Independent from adult for support
Develops into adult
All fish are ectothermic- body temperature matches the environment

20. Vertebrates Fish cont’d
Superclass Agnatha - Jawless fish
Cylindrical body shape with smooth, scaleless skin
No jaws, no paired fins
Hagfish-scavengers
Lampreys- parasitic
Mouth modified to form a sucker
Attach to other fish
Water moves in and out of gills directly and not through mouth as in other fish

21. Vertebrates: Fish cont’d
Class Chondriicthyes -Cartilaginous fish
Endoskeleton of cartilage
Sharks, skates, rays
Dermal placoid scales-gives body surface a “sandpaper- like” feel
Gills open, lack operculum (gill flap)
Efficient predators
Can sense electrical currents in water which indicate presence of prey
Lateral line system-sense pressure created by prey nearby
Well-developed sense of smell- sharks can detect 1 drop of blood in 25 gallons of water!

22. Vertebrates: Fish cont’d
Class Osteichthyes - Bony fishes
most numerous and diverse of all vertebrates
Ray-finned fish-paired fins supported by bony rays; have jaws and skeletons of bone
Swim bladder- buoyancy organ
Streamlined body shape
Skin covered by bony epidermal scales
Water pumped across gills by an operculum
Enters through mouth, exits across gills
Blood pumped by heart with non-divided 2 chambered heart
Lobe-finned fish-fleshy appendages could be adapted for locomotion on land
Most had lungs

23. Jawed fishes
Fig. 31.8

24. Vertebrates: Class Amphibia
Organisms: Salamanders, frogs, toads, newts
Body Structure:
Tetrapods, jointed appendages, ectothermic
Eyelids keep eyes moist, ears, larynx for vocalization
Larger brain than in fish

25. Vertebrates: Class Amphibia cont’d
Circulation and Respiration
Small lungs present in adults; gas exchange also occurs across moist skin
3-chambered heart-2 atria and a ventricle
Rt atrium receives deoxygenated blood from body
L atrium receives oxygenated blood from lungs
Blood mixes in ventricle
Metamorphic life cycle
larval stages in water, adults on land
Reproduction generally occurs in water

26. Frog metamorphosis
Fig. 31.9

27. Vertebrates: Class Reptilia
Organisms: turtles, tortoises, snakes, lizards
Extinct reptiles
Include mammal-like reptiles and dinosaurs
Evidence suggests birds are “feathered dinosaurs”
A common reptilian ancestor most likely gave rise to modern reptiles, birds, and mammals
Body Plans:
Most are tetrapods; ectothermic
can regulate temperature through behavior (ex: basking)
Rib cage to protect organs and expands to inflate lungs
Dry skin covered with protective scales

28. Vertebrates: Class Reptilia cont’d
Reproduction:
Amniote egg covered with leathery shell
Circulation
3-chambered heart (division between ventricles incomplete) in most; true 4 chambered heart in some
Nervous System
Well-developed sense organs: snakes have tongue modified as sense organ

29. The tongue as a sense organ
Fig

30. The reptilian egg allows reproduction on land
Fig

31. Vertebrates: Class Aves
Birds, feathers are modified scales; legs of birds have scales
Locomotion
Forelimbs modified for flight-wings
Sternum has keel for attachment of large muscles
Cardiovascular
4-chambered heart- more efficient oxygen delivery
Endothermic-regulate body temperature above ambient
System of air sacs and one-way air flow through respiratory tract- increased efficiency of gas exchange

32. Vertebrates: Class Aves cont’d
Nervous System
Well-developed with sense organs
Navigational senses
Reproduction
Amniote egg with a hard shell
Ritualized courtship,
young require parental care
Cloaca- common urogenital opening

33. Bird anatomy and physiology
Fig

34. Vertebrates: Class Aves cont’d
Classification
Based on beak and foot types
Also on habitat and behavior to a lesser degree
Birds of prey
long talons, notched beaks
Shorebirds
long, slender bills and long, stilt-like legs
Woodpeckers
sharp, chisel-like bills, grasping feet
Waterfowl
webbed toes and broad, scooping bills
Penguins
wings modified as paddles
Songbirds
perching feet

35. Bird beaks
Fig

36. Comparing Circulation
Fig

37. Vertebrates: Class Mammalia
Endothermic, maintain relatively constant internal temperature
Hair provides insulation to preserve body heat
Mammary glands allow care for young without having to leave them
Cardiovascular System
Efficient supplies muscles that generate heat
4-chambered heart
2 separate circuits for oxygenated and deoxygenated blood
Classified into 3 groups based on reproduction
Internal development in most with birth of live young

38. Class Mammalia: Monotremes
Egg-laying mammals
lay a hard-shelled egg
Representative Organisms:
Spiny anteater and duck-billed platypus
Both found in Australia
Have a cloaca like birds
Both males and females have modified sweat glands and secrete milk onto body surface
Babies lick up the milk

39. Class Mammalia: Marsupials
Development
Begins within female’s body
Born very immature completed within a pouch
Young continue development attached to nipples of mammary glands within the pouch
Representative organisms:
Virginia opposum is the only marsupial species north of Mexico
Many species in Australia
Evolved with no competition from placentals
Allowed rise of many marsupial species

40. Monotremes and marsupials
Fig

41. Class Mammalia: Placentals
Vast majority of living mammals
Extra-embryonic membranes within eggs evolved to form placental membranes

42. Class Mammalia: Placentals cont’d
Adaptations for active life on land:
Response to environment:
Well-developed brain and sense organs
Limbs that allow rapid movement
Efficient circulation and respiration:
Lungs expanded by rib cage and a diaphragm
4-chambered heart

43. Class Mammalia: Placentals cont’d
Adaptations for active life on land: cont’d
Endothermic
Internal body temperature is constant
allows optimum nerve and enzyme functions
Hair- insulates body
Differentiated teeth
incisors, canines, premolars, molars
Shape and size of teeth may determine type of food eaten

44. Class Mammalia: Placentals cont’d
Classification
Based on
methods of obtaining food
mode of locomotion;
Examples:
Order Chiroptera
bats; wings supported by digits for flight
Order Perissodactyla
horses; long, hoofed legs for speed
Order Cetacea
whales; paddle-like forelimbs

45. Placental mammals
Fig

46. Class Mammalia: Placentals Primates cont’d
Adaptations to arboreal life
Mobile limbs; hands and feet with 5 digits
Opposable thumbs for grasping
Eyes to be placed at the front of the head
Accurate distance vision
Color vision, high acuity
Large, complex brain
Smallest in prosimians and largest in humans
Cerebral cortex is highly folded for surface area in humans
Olfactory lobe becomes progressively smaller up the scale, while visual areas get larger

47. Class Mammalia: Placentals Primates cont’d
Adaptations to arboreal life cont’d
Give birth generally to one offspring at a time
Extended period of juvenile dependency, learned behaviours
2 suborders
Prosimians
lemurs, tarsiers
Anthropods
monkeys, apes, humans

48. Human evolution Evolutionary tree
Figure 31.16
Shows all primates share a common ancestor
Other types of primates diverged from human line over time
Prosimians were first
African apes were the last
Last common ancestor lived approximately 7 million years ago

49. Human evolution cont’d
Evolutionary tree cont’d
Darwin
suggested a common ancestry.
NOT that we evolved FROM apes
We can’t have evolved from something that’s still here!
Molecular data
used to determine time of divergence
Molecular clock- estimates regular rate of mutations
Mutations, or differences, accumulate at a fairly regular rate

50. Human evolution cont’d
Family Hominidae
Hominids
exhibit anatomy suitable for standing and walking erect (bipedalism)
Bipedalism made food gathering easier
Believed to have evolved approximately 6 million years ago

51. Human evolution: Hominids cont’d
Australopithecenes
Evolved in Africa 4 million years ago
2 forms- gracile and robust
Southern Africa
Australopithecus africanus- gracile form
Australopithecus robustus- robust form
Differed due to diet
Eastern Africa
Australopithicus afaransis- “Lucy”; gracile form
Believed to be ancestral to the robustus forms found here
Indicate evolution may have been mosaic
Occurred at different rates or times for different parts
ape-like above the waist
human-like below the waste

52. Australopithecus afaransis
Fig

53. Human evolution: Hominids cont’d
Evolution of early Homo
Genus exhibits
brain size of 600 cc or larger
jaws and teeth resemble humans
tool use is evident
Homo habilis- dated between 2 and 1.9 m.y.a.
Brain size as large as 772 cc; enlarged speech areas
Speech may have led to cooperative hunting
Smaller cheek teeth indicates an omnivorous diet
Findings indicate tool use
Crude tools made of stone
Culture- encompasses behavior and products
Hunter and gatherers may have eaten together and shared food

54. Human evolution
Fig

55. Human evolution: Hominids cont’d
Evolution of early Homo cont’d
Homo erectus
Dated between 1.9 and .3 m.y.a
Larger brain (1000 cc) and flatter face than H. habilis
Taller than previous species
Nose protruded-adapted for hot, dry climate
Striding gait like modern humans
First appeared in Africa and then migrated into Asia and Europe
Used fire, and made more sophisticated tools
Axes, cleavers
Indications of “home base” locations where social interactions occurred, children were raised

56. Homo erectus
Fig

57. Human evolution: Hominids cont’d
Evolution of modern humans
Homo sapiens
2 hypotheses
Multiregional continuity hypothesis
Evolution to modern humans occurred in similar ways in several different places
If true, each region should show a continuity of its own anatomical characteristics
Suggests that there should be genetic differences between groups

58. Human evolution: Hominids cont’d
Out-of-Africa hypothesis
H. sapiens evolved from H. erectus in Africa and then migrated out to other areas
Suggests we all are genetically similar
Studies of mitochondrial DNA suggest the Out-of- Africa hypothesis is more likely

59. Evolution of modern humans
Fig

60. Human evolution: Hominids cont’d
Neanderthals
Massive brow ridges, protruding nose, jaws, and teeth
Low, sloping foreheads
Larger brain than H. sapiens,
Suspect increased brain size needed to control the large musculature
Culturally advanced
used tools, cooked their food, buried their dead with flowers, may have had a religion
According to the Out-of Africa hypothesis, Neanderthals were displaced by modern humans

61. Neanderthals
Fig

62. Human evolution: Hominids cont’d
Cro-Magnons
Oldest fossils to be designated H. sapiens
Modern appearance, made compound tools, were the first to hunt with knives and spears
Hunted cooperatively
May have been the first to have language
Culture included art- sculpture and painting

63. Cro-Magnons
Fig