Description
Purpose
To introduce you to principles of taxonomy as you look at morphological characteristics of sea shells and construct an evolutionary tree.
Directions
- Go to the link http://media.hhmi.org/biointeractive/click/shells_online/index.html and work through the lab sorting sea shells based on morphological characteristics to study evolutionary relationships.
- Please take notes for your laboratory report. You will add an introduction later. Write a short note describing each step of identifying and selecting snails as you work through the lab. Please take a screen shot of the final drawing showing the evolutionary relationship of all snails listed.
Please answer the following questions:
- Why was the scallop among the snails? (HINT: Watch "Dr. Olivera discusses major molluscan groups")
- What additional tests could be used to examine evolutionary relationships among molluscs (snail species)? (HINT: Watch "Dr. Olivera discusses how to classify shells")
- How was the name of different cone snail specied decided? (HINT: Watch the video "Dr. Olivera discusses species names")
- Where are cone snails found and what are their feeding habits? (HINT: Click on snail images on the final evolutionary tree for more information about species).
- Describe the evolutionary history of snails (Molluscs). In which eon, era and period did the first snails evolve? (HINT: Textbook, chapter 15.3)
- The laboratory report will have a title page (APA format), and an introduction. Summarize the life history of cone snails. List your steps to classify the snails under methods, post the final picture of snail specis under results and discuss limits of morphological classification in the discussion section of the lab report. Suggest additional tests which may clarify cone shell taxonomy. You should also have a reference section, with the textbook and web page listed in APA format.
- Please review the grading rubric for the assignment for additional details and grade criteria. Also use the "How to write a lab report" links in the Grading Rubrics folder for futhur guidance.
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Morphological characteristics of sea shells and construct an evolutionary tree.
Introduction
Mollusca is one of the most diverse groups of animals on the planet that includes familiar
organisms such as snails, octopuses, squid, clams, scallops, oysters, and chitons. Mollusca also
includes some lesser known groups like the monoplacophorans, a group once thought to be extinct
for millions of years until one was found in 1952 in the deep ocean off the coast of Costa Rica.
Molluscs are a clade of organisms that all have soft bodies which typically have a "head" and a
"foot" region. Their bodies are covered by a hard exoskeleton, as in the shells of snails and clams
or the plates of chitons.
These creatures have been significant to humans throughout history. They act as a source of food,
jewelry, tools, and even pets on the Pacific coast of California, Native Americans consumed large
quantities of abalone and especially owl limpets. Species whose members once numbered in the
millions, now teeter on the verge of extinction. For example, fewer than 100 white abalone remain
after several million individuals were captured and sold as meat in the 1970s.
Besides having yummy soft parts,...