C. elegans Anatomy
http://www.wormatlas.org
Module 1: Meet the Worm!
C. elegans Anatomy
BABEC 9/24/09
Page 2-45
C. elegans comes in 2 sexes
http://www.wormatlas.org
In a population of C. elegans,
approximately 1 in 500 worms
will be male; the rest will be
hermaphrodites.
The way to tell them apart is to
look at the tail. Hermaphrodites
have a tapered tail; males have
blunt tail shaped somewhat like
a spade.
http://www.wormatlas.org
Module 1: Meet the Worm!
C. elegans Sexes
BABEC 9/24/09
Page 2-46
Cladistics: The Tree(s) of Life
A cladogram is a diagram that shows how organisms are related in terms of their evolutionary development. A cladogram can be thought of as a
family tree for a group of related organisms. Cladistics is a rapidly evolving science. As scientists learn more about the DNA and proteins of living
organisms, they reorganize cladograms such that related organisms are grouped together based on molecular similarity. Bracketed organisms are
most closely related and share the most recent common ancestor. For example, in the Cladogram of Eukaryotes, animals and fungi share a more
recent common ancestor with each other than they do with plants and other eukaryotes.
Protolife
Cladogram of All Living Things
Archaea (halophiles, methanogens, extremophiles)
Eubacteria (true bacteria)
Eukaryotes (plants, animals, fungi, protista)
More Ancient
Cladogram of Metazoa (Animals)
Bilateria (most animals)
Cladogram of Eukaryotes
Cnidaria (jellies, anemones,
Metazoa (animalia)
corals)
Fungi (mushrooms,
Ctenophora (comb jellies)
molds)
Porifera (sponges)
Stramenopiles (diatoms, brown algae)
Alveolates (dinoflagellates, ciliates)
Rhodophyta (red algae)
Plantae (green plants)
More recent
Cladogram of Bilateria
Deuterostomia (echinoderms and vertebrates)
Arthropoda (insects, spiders, crabs)
Onychophora (velvet worms)
Nematoda (roundworms, C. elegans)
Nematomorpha (horsehair worms)
Priapulida (penis worms)
? Rotifera (rotifers)
? Platyhelminthes (flatworms, tapeworms)
Annelida (segmented worms, earthworms, leeches)
Sipuncula (peanut worms)
Mollusca (clams, snails, octopi, mussels, squid)
Notice that Bilateria include several different phyla of animals called worms. C. elegans and other nematodes are worms, but they are different
(genetically and physiologically) from other worms such as the annelids or platyhelminthes. “Worm” tends to be used generically to refer to
animals sharing a “worm-like” shape. The cladogram for Bilateria is abbreviated (some phyla were not included to save space).
Module 1: Meet the Worm!
Cladistics: The Tree(s) of Life
BABEC 9/24/09
Page 2-47