BSsqans-lect15-16 moll

BSsqans-lect15-16 moll - BIS 1B (Winter 2008) Study...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
BIS 1B (Winter 2008) Study question answers: Mollusca Lectures 15 and 16 1. Using what you know about surface area to volume ratios and about countercurrent exchangers, explain why your fingers get colder than your palms on cold days. What does this question have to do with mollusks? Fingers have a much higher surface to volume ratio than does the palm of the hand, thus loose heat more rapidly. Counter current heat exchange in the parallel arteries and veins of the fingers tends to heat the cold venous blood and cool the arterial blood flowing in the fingers. Thus, blood returning to the palm is warmer than it would have been in the fingers. Mollusks use a similar counter current system across their ctenidial gills for more efficient respiration. 2. There is a debate among zoologists about the relationship between annelids and mollusks. Can you summarize the arguments for and against a relationship? Some primitive molluscs have serially repeated gills and other repeated internal structures that resemble the metamerism seen in annelids. Molluscs often have a trochophore larva also seen in marine annelids. Alternatively serial repetition of structure is molluscs is superficial and other nonmetameric marine protostomes have trochophore larvae. Thus molluscs may have diverged from the main protostome lineage before the advent of metamerism and annelids. This is hard to tell because molluscan ancestors were probably soft bodied and left few fossils 3. What is the difference between hermaphroditism and parthenogenesis? What are some possible advantages and disadvantages of each mode of reproduction? (Hint: think in terms of both population numbers and genetic variance.) Hermaphrodites are individuals that possess female and male sexual organs, where as parthenogenesis is unisexual reproduction by females not fertilized by males. The hermaphrodite advantage is that any two individuals in the population can copulate and produce recombinant progeny, but two different individuals may
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/15/2008 for the course BIS 1b taught by Professor Kimsey during the Spring '08 term at UC Davis.

Page1 / 4

BSsqans-lect15-16 moll - BIS 1B (Winter 2008) Study...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online