1. Week 7: Deuterostomes

2. Echinoderms- sea stars and sea urchins
Four phyla:
Echinoderms- sea stars and sea urchins
Hemichordata- “acorn worms” burrow in marine sands or muds
Xenoturbellida- one genus, only two species- worm-like
Chordata- include the vertebrates (have backbones)- fish, sharks, amphibians, mammals, and reptiles
Focus on echinoderms and chordates 2

3. Review: Protostomes vs. Deuterostomes
Similarities:
Bilaterally symmetric
Triploblastic
Coelomates
Differences:
Initial pore development (anus first in deuterostomes)
Process of coelom formation in embryonic stages
When the embryo is developing, there are three tissue layers- ectoderm (skin, nervous system, teeth, hair, nails, linings of mucous membranes), mesoderm (muscles, red blood cells), and endoderm (GI tract, respiratory tract, urinary system, auditory system, endocrine glands, endocrine organs)
Human abdominal cavity- surrounds digestive tract, vital organs– important for protection, movement, etc. 3

4. Scientific Method: Important Questions
What are the big patterns?
What processes led to that pattern?
Physiological mechanisms
Developmental processes
Understanding evolutionary history
Adaptive significance
Why should we care?

5. Echinoderms- sea stars and sea urchins
Four phyla:
Echinoderms- sea stars and sea urchins
Hemichordata- “acorn worms” burrow in marine sands or muds
Xenoturbellida- one genus, only two species- worm-like
Chordata- include the vertebrates (have backbones)- fish, sharks, amphibians, mammals, and reptiles
Focus on echinoderms and chordates 5

6. Echinoderms (“spiny skin”)
Sea stars, sea urchins, sea cucumbers
7,000 species, found at any depth in the ocean; very abundant, especially deep in the ocean
Able to regenerate lost tissues- like limbs
Actually radially symmetric 6

7. Echinoderms
Bilaterians (larvae are bilaterally symmetric, but adults have five-sided radial symmetry)
Endoskeletons = hard structures made from CaCO3 inside epidermal tissue, protection and support
Three major synapomorphies to be familiar with. 7

8. Echinoderms Water vascular system= branching, fluid-filled tubes
Controls the tube feet (movement and feeding) 8

9. Echinoderms- sea stars and sea urchins
Four phyla:
Echinoderms- sea stars and sea urchins
Hemichordata- “acorn worms” burrow in marine sands or muds
Xenoturbellida- one genus, only two species- worm-like
Chordata- include the vertebrates (have backbones)- fish, sharks, amphibians, mammals, and reptiles
Focus on echinoderms and chordates 9

10. Hemichordata “Acorn worms” Sister to the echinoderms
Marine animals, some are called “acorn worms”, usually live in burrows 10

11. Echinoderms- sea stars and sea urchins
Four phyla:
Echinoderms- sea stars and sea urchins
Hemichordata- “acorn worms” burrow in marine sands or muds
Xenoturbellida- one genus, only two species- worm-like
Chordata- include the vertebrates (have backbones)- fish, sharks, amphibians, mammals, and reptiles
Focus on echinoderms and chordates 11

12. Xenoturbellida
Marine, worm-like
Only one genus, two species 12

13. Echinoderms- sea stars and sea urchins
Four phyla:
Echinoderms- sea stars and sea urchins
Hemichordata- “acorn worms” burrow in marine sands or muds
Xenoturbellida- one genus, only two species- worm-like
Chordata- include the vertebrates (have backbones)- fish, sharks, amphibians, mammals, and reptiles
Focus on echinoderms and chordates 13

14. Chordata
Sea squirt
>65,000 species, most diverse of the deuterostomes
Includes vertebrates but also cephalochordates and urochordates 14

15. Chordate Synapomorphies
Pharyngeal gill slits
Dorsal hollow nerve cord
Notochord
Muscular, post-anal tail
Pharyngeal gill slits- slits that open into the throat, found in developing human embryo (in vertebrates they’re pharyngeal pouches– can develop into gills in marine fish) 15

16. Chordate Synapomorphies
Pharyngeal gill slits
Dorsal hollow nerve cord
Notochord
Muscular, post-anal tail
Pharyngeal gill slits- slits that open into the throat, found in developing human embryo
Dorsal hollow nerve cord- runs the length of the body, composed of projections from neurons; a hollow tube; in humans (and all vertebrates) it was modified into the brain and spinal cord
Notochord- stiff, supportive, flexible rod that runs the length of the body (ventral to the nerve cord), support for the body and movement, but in vertebrates it disappears after embryo development- it still helps organize the body plan during embryo development
Like our tailbone 16

18. Cephalochordates (lancelets)
“Fish-like,” burrow in sand, suspension feed
Muscle contractions on either side of notochord help with movement 18

20. Urochordates (sea squirts)
Pharyngeal gill slits help with feeding and gas exchange
Nerve cord, notochord, and tail help with swimming

24. Vertebrates
Brain and spinal cord (the dorsal hollow nerve cord)– nerve cells that run from brain to posterior of body
Pharyngeal pouches in embryos
Notochord only in embryos, replaced with vertebrae (important segmentation)

25. Chordates: Vertebrates
Pharyngeal gill slits
Dorsal hollow nerve cord
Notochord
Muscular, post-anal tail
Vertebrates:
Pharyngeal pouches, not slits
Spinal cord, not dorsal hollow nerve cord
*Vertebrae, not notochord
Pharyngeal gill slits- slits that open into the throat, found in developing human embryo (in vertebrates they’re pharyngeal pouches– can develop into gills in marine fish) 25

26. Vertebrates: Major Synapomorphies
Vertebrae (column of cartilaginous or bony structures; protects spinal cord)
Cranium (bony, cartilaginous, or fibrous case enclosing the brain; protects brain and eyes)

27. Key innovations 480 mya: Bony exoskeleton 440 mya: Jaws
420 mya: Bony endoskeleton
365 mya: Limbs for moving on land (tetrapods)
340 mya: Amniotic egg
Jaws- important for being able to actually bite food
Tetrapods- include mammals, reptiles, and amphibians
Amniotic egg- egg that has membranes surrounding a food supply, water supply, and waste repository– in the mammals and reptiles 27

28. Question 1
What synapomorphy distinguishes animals as a monophyletic group, distinct from choanoflagellates?
Multicellularity
Movement via hydrostatic skeleton
Growth by molting
Ingestive feeding

29. Question 1
What synapomorphy distinguishes animals as a monophyletic group, distinct from choanoflagellates?
Multicellularity
Movement via hydrostatic skeleton
Growth by molting
Ingestive feeding

30. Question 2
Which of the following patterns in animal evolution is correct?
All tripoblasts have a coelom
All tripoblasts evolved from a common ancestor that had a coelom
Sponges have epithelial tissues that line an enclosed fluid-filled cavity
Bilateral symmetry and cephalization evolved once

31. Question 2
Which of the following patterns in animal evolution is correct?
All tripoblasts have a coelom
All tripoblasts evolved from a common ancestor that had a coelom
Sponges have epithelial tissues that line an enclosed fluid-filled cavity
Bilateral symmetry and cephalization evolved once

32. Question 3
Which of the following patterns in animal evolution is correct?
Segmentation evolved once
Coelom was lost or reduced in many lineages
Sponges lack true tissue and are asymmetrical
Radial symmetry evolved once

33. Question 3
Which of the following patterns in animal evolution is correct?
Segmentation evolved once
Coelom was lost or reduced in many lineages
Sponges lack true tissue and are asymmetrical
Radial symmetry evolved once

34. Question 4 In a “tube within a tube” what is the interior tube?
Ectoderm
Mesoderm
The coelom
The gut

35. Question 4 In a “tube within a tube” what is the interior tube?
Ectoderm
Mesoderm
The coelom
The gut

36. Question 5 What is the diagnostic trait(s) of vertebrates?
Vertebrae and cranium
Jaws and spinal cord
Endoskeleton constructed of bone
Endoskeleton of reinforced cartilage

37. Question 5 What is the diagnostic trait(s) of vertebrates?
Vertebrae and cranium
Jaws and spinal cord
Endoskeleton constructed of bone
Endoskeleton of reinforced cartilage

38. Question 6 Which lineages make up the living amniota?
Reptiles and mammals
Viviparous fishes
Frogs, toads, salamanders, and caecilians
Hagfish, lampreys, and cartilaginous fishes

39. Question 6 Which lineages make up the living amniota?
Reptiles and mammals
Viviparous fishes
Frogs, toads, salamanders, and caecilians
Hagfish, lampreys, and cartilaginous fishes

40. Question 7
True or false?
Vertebrates were able to harvest food by biting before jaws evolved.
The hypothesis that tetrapod limbs evolved from fish fins has been supported by molecular evidence.

41. Question 7
True or false?
Vertebrates were able to harvest food by biting before jaws evolved. False
The hypothesis that tetrapod limbs evolved from fish fins has been supported by molecular evidence. True