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
- Ill post a few sample questions
- Ill 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!