Reminder ...

• Lecture exam in ~ two weeks (March 9)
• Format:
  • 5 multiple choice (may be 0-5 correct answers) = 25 points
  • 2 short essay @ 15 points = 30 points
  • 10 fill in blanks (one or more words, short phrases) = 20 points
  • 5 short answer @ 5 points = 25 points
• I’ll post a few sample questions
• I’ll be in the Union from 1:15-3:00 on March 7
• Errors in readings
• Text Figure 2-9: Cnidarian should not have mesoderm
• Lab manual preface #2. Should start "By 540 mya ..."

SAMPLE TEST QUESTIONS:

• Example of a "multiple choice" question (0-5 correct answers) (5 @ 5 points each)
• Circle A B C D E
• 1. Multicellular animals evolved and diversified into the major lineages (phyla) seen today:
  A. Somewhere between a million and 500,000 years ago.
  B. Somewhere between a billion and 500 million years ago.
  C. Following the greatest mass extinction of all time at the end of the Paleozoic.
  D. Probably from a colonial flagellate ancestor.
  E. Before they developed hard shells that are well represented in the fossil record.
• Answers B, D, E are correct

SAMPLE TEST QUESTIONS:

• Example of a "short essay" question (2 @ 15 points each)
• Describe what a zooxanthella is and what the relationship of a zooxanthella to a coral is, including where the zooxanthella lives and how the coral and zooxanthella each benefit or are harmed.
• Answer that would get full credit:
• A zooxanthella is a symbiotic dinoflagellate that lives inside the cells of a coral. The zooxanthellae releases organic compounds that coral uses for food and enhances calcification [or skeletal growth] of the coral. The coral provides N and P as waste products which the zooxanthella can use, and protects the dinoflagellate from grazing.

SAMPLE TEST QUESTIONS:

• Example of a "fill in the blank" question (10 @ 2 points each)
• A large proportion of the world's described species belong to what group? ________________.
• Correct answers:
• insects, arthropods, or protostomes

SAMPLE TEST QUESTIONS:

• Example of a "short answer" question (5 @ 5 points each)
• How are boring organisms (no pun intended) related to the development of high species diversity on the world's coral reefs?
• Correct answer:
• They provide 3-dimensional microenvironments that favor small organisms with rapid evolution.

Grades and Clades

Triploblastic body plans

• Evolution of body plans very complex
• Three major grades of organization
• Acoelomates - no cavity present, solid layer of mesoderm
• Pseudocoelomates - Cavity present between endoderm and mesoderm; from blastocoel
• Eucoelomates - Cavity present within mesoderm
• All three plans found in Protostomes
• All Deuterostomes are Eucoelomates

Pseudocoelomates = "Aschelminthes"

• May be polyphyletic
• Fluid filled cavity not surrounded by mesoderm (endoderm one side, mesoderm other side)
• Numerous phyla, including:
• Phylum Rotifera
• Phylum Nematoda

"Pseudocoelomate" body plan

• Pseudocoelom
• Remnant of Blastocoel

"Pseudocoelomate" body plan

• Fluid filled body cavity
• Advantages
• Hydrostatic skeleton
• Easier internal transport
• Storage of materials
• Gamete maturation site
• Enlargement of organs
• Disadvantages
• Internal organs not well supported
• No muscles on digestive tract
• Little interaction between mesoderm and endoderm

Phylum Rotifera

• Abundant in fresh water
• Characteristics
• Corona
• Muscular Mastax
• Usually parthenogenetic
• Sexual reproduction rare

Phylum Nematoda

• Extremely successful
• Can be free-living or parasitic
• Includes C. elegans
• Important in medicine (pinworms, intestinal roundworms, filarial worms=elephantiasis), agriculture (root worms, other pests), and ecological systems

Nematode characteristics

• Cylindrical, tapered
• Flexible cuticle (chitin, must molt to grow)
• Chitinous jaws (for holding on)
• Relative lack of cilia, flagella
• No circular muscles in body wall, only longitudinal
• Dioecious (separate sexes), internal fertilization
• Especially parasites: egg machines

Adaptations for Parasitism

(e.g., some classes Platyhelminthes, Nematoda)

• Very high reproductive potential
• asexual
• sexual
• Often flat, thin, long
• Structures for holding on to host
• hooks
• suckers
• jaws
• May have sophisticated means of finding new hosts, deceiving hosts once in, defense against host protective mechanisms

"Eucoelomates"

• Polyphyletic
• Two Major Groups
• Protostomes
• Deuterostomes
• Both very successful

"Eucoelomate" body plan

• True coelom
• Surrounded by mesoderm
• Advantages. Same as pseudocoelom, plus:
• Better interaction of mesoderm, endoderm
• Better support of organs
• More efficient digestion (mesoderm around gut)

Eucoelomate Protostomes

• Monophyletic
• Three main phyla
• Mollusks
• Annelids
• Arthropods
• Numerous smaller phyla

Deuterostomes (all eucoelomate)

• Monophyletic
• Three main phyla
• Echinodermata
• Hemichordata
• Chordata

Relationships of the Bilateria - review

EXAM I GOES TO HERE!