Krystal Morrice
Anthropology Blog Post
21 February 2013
Week 3: Analogy/Homology Blog Post-
1.
a. There are
several different types of species that portray homologous traits. After doing
some research the two different species that portray homologous traits that I
choose are a snail and a slug. A slug is a soft bodied creature that creates mucus
when they move about. A snail has the same features that a slug has, except
snails have a hard exterior shell.
b. Both and
slugs are similar in the fact that they both have the soft bodies with a slime
like mucus that they leave behind while moving around. They both have a
muscular contraption on the bottom side of their bodies that helps them move
along the ground. The differences in the bodies, however, is that the slug is just
a soft bodied creature, while the snail has the soft body but with a hard
exterior shell. The question asked is which came first? Did their bodies
eventually grow through evolution to help protect their soft bodies? Or did the
slugs eventually shed a shell through evolution to help get through smaller
areas or for some other reason? I will reveal the answer researchers came to.
c. Any type of
slug like creature. I am not sure if they really were a common ancestor, but I
would say a tad pole would be a common ancestor from the water and a worm would
be an ancestor of land.
d. 
2.
a. Like the
example given, I chose three different species. Two that had similar homozygous
traits and two (one of the same species and a different one) with analogous
traits. The two analogous species are a snail and a turtle. Both are soft
bodied animals with a hard exterior shell that protects them from predators as
well as environmental factors. These two species have similar features, but
they are not made from common ancestors. A snail is the slimy soft bodied small
creature known as a mollusk while a turtle is a soft bodied creature known as a
reptile. Both have hard shells that are on top of their bodies.
b. The similar
analogous trait that both of these species share are their “shell”; the hard
exterior casing on the top of each creature. Both species can shrink inside of
their shell which helps protect them from any outside threats. The different between
the snail and the turtle are the fact that a snail is a long slimy critter,
similar to a worm, while a turtle is more similar to a lizard type animal with
its two arms, two legs, and head.
c. It is
definitely possible that the ancestor of both the snail and the turtle (if you
go far back enough) had a hard exterior shell. If I were to guess, without
doing research, I would say that their ancestors originally did not have a
shell and over time they grew a shell to protect their soft bodies from any environmental
or outside threats. But after doing some research via the internet, scientific
research shows that the snail came first, meaning that the slug came from
evolution. The snail shed its shell through evolution and eventually was called
a slug, due to the slimy mucus it lets off while moving around (shell-less). This
could one day be the same for turtles, or, the fact that turtles have similar
shell-less ancestors; crocodiles.
d. 
Works
Cited
"Gastropoda
- slugs and snails." CSIRO Ecosystem Sciences. N.p., n.d. Web. 22
Feb. 2013. <http://www.ento.csiro.au/education/allies/gastropoda.html>.
"Slug -
Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia.
N.p., n.d. Web. 22 Feb. 2013. <http://en.wikipedia.org/wiki/Slug>.
"Snails
Ship Out on Scrambled Eggs - ScienceNOW." Science/AAAS | News - Up to
the minute news and features from Science.. N.p., n.d. Web. 22 Feb. 2013.
<http://news.sciencemag.org/sciencenow/2011/10/snails-ship-out-on-scrambled-eggs.html?ref=hp>.
ones, newer, and
if one knows how many scutes are produced in a year.. "Turtle - Wikipedia,
the free encyclopedia." Wikipedia, the free encyclopedia. N.p.,
n.d. Web. 22 Feb. 2013. <http://en.wikipedia.org/wiki/Turtle>.
Wow. Honestly, I have always wondered what the differences were between a snail and a slug. As a child, i actually thought that slugs were snails who out grew their shells. I'd never thought about it from an evolutionary stand point though. Great choice.
ReplyDeleteI also liked your comparison of the snail and the turtle. I've actually never realized their similarities. Very interesting post.
I enjoyed your writing style. Missing images?
ReplyDeleteWhen we compare homologous traits, we are comparing two existing and related traits. The snail shell/slug comparison doesn't satisfy this requirement as we are comparing a trait that does exist to a trait that doesn't. This is highlighting a unique derived trait in the snail (the shell) and ancestral form in the slug (no shell). By the way, you said you would reveal which came first, and you never did!
A tadpole is the embryonic form of the frog, which is an amphibian. They could not be ancestral to moluscs like the slug and snail.
Good comparison between the turtle and the snail. That is an excellent example of analogous traits. You have to go back pretty far to find the common ancestor to these two creatures, but the key is that the turtle evolved its shell as a derived trait unique to turtle and tortoise species. They didn't inherit it from much earlier amphibian ancestors (or earlier). So that means this arose from parallel evolution.
Krystal, your our post was very enlightening and interesting. Like Danielle, I have always assumed that slugs were simply snails without their shells; I knew that they were both extremely similar but I didn't know that both the snail and the slug were two separate creatures. Your analysis of both the snail, slug and turtle was something I never would have thought of and thought that it was a very informative. I gained a better understanding of the topics of both analogous and homologous traits through your post. Very well done.
ReplyDelete