Slugs, Snails, Turtles...

 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>.

From DNA to RNA to Sentence(A)

TAA GCA AGC AGT GGC TTA AGT TTC AAA TTG TCT


HAPPY DECODING!!

Malthus' Ideas>Darwin's Ideas>Natural Selection Theory

1.      Select one of the five individuals listed above who you would argue had the most influence over Darwin’s development of his theory of Natural selection. This could be a positive or a negative influence.

I believe that Thomas Malthus (1766-1834) had the most influence over Darwin’s development of this theory of Natural selection. Malthus wrote An Essay on the Principle of Population, which talked about human population growth. Malthus believed that “in nature, animal populations increase in numbers when resources are plentiful and/or there aren’t many predators. This tendency for populations to increase in size is constantly being held in check by the availability of resources…” (34). Darwin added on to this hypothesis and applied Malthus’ principle too all organisms, in turn creating his theory of Natural selection.

2.      Briefly (but completely) describe the contribution this individual made to the scientific community. You must provide one link to an online source of information besides your textbook. No Wikipedia sources! ( 10 pts)

Thomas Malthus influenced both Darwin and Alfred Russel Wallace in their discoveries of natural selection. He wrote a journal explaining the principle of population and its effects on human evolution.

“Malthus' most well-known work 'An Essay on the Principle of Population' was published in 1798, although he was the author of many pamphlets and other longer tracts including 'An Inquiry into the Nature and Progress of Rent' (1815) and 'Principles of Political Economy' (1820). He argued that increases in population would eventually diminish the ability of the world to feed itself and based this conclusion on the thesis that populations expand in such a way as to overtake the development of sufficient land for crops” (http://www.bbc.co.uk/history/historic_figures/malthus_thomas.shtml).

Even though Malthus influenced Darwin and Wallace in their ideas about Natural Selection, he was often criticized for his ideas and hypothesis’. Malthus’ ideas began to get recognized again more toward the 20^th century.

3.      From the bullet point list above (under “How does evolution work?”), identify the point (or points) most directly affected by this individual’s work and thoroughly explain how this point was influenced by your selected individual. Again, this could be a positive effect, meaning Darwin built upon the knowledge this information provided, or a negative effect, meaning that Darwin demonstrated that this individual’s idea(s) were incorrect and the mechanism of natural selection was an alternative explanation. (10 pts)

Thomas Malthus’s work mostly focused on human population rather than organisms or animals, however, the main idea from the bullet points is similar to Malthus’ ideas. The second bullet point on the list says “What is preventing organisms from reproducing at their potential? Something is keeping those rabbits from producing all those bunnies. Baby rabbits are costly to the parent to produce. The parent needs time, shelter, food, water and protection from predators. These needs are called “resources”.” Malthus pointed out that animal population increases when resources are plentiful in his journal An Essay on the Principle of Population. Other bullet points on the list such as: Resources are limited, Who gets better access to these limited resources?, and If the environment changes, the traits that are helpful or adaptive to that environment are intertwined with Malthus’ (second) bullet point in regards to resources and reproducing, but they don’t directly relate to Malthus’ ideas and theories. Like I stated in earlier answers Malthus was a main influence in helping Darwin come up with his theory of Natural Selection and Malthus’ main idea was that population can increase if resources were available; just like the bullet points state.

4. Could Darwin have developed his theory of natural selection without the influence and ideas of this individual? Explain. (10 pts)

Darwin’s theory of Natural Selection is an extended more in-depth idea of Malthus’ principles; so no I don’t think that Darwin could have developed his theory of Natural Selection without the influence of Malthus’ work. In reality, I am sure that Darwin could have come up with the similar ideas throughout time, but since Malthus already created his theories, it just benefited Darwin in his discoveries.

5.      How did the attitude of the church affect Darwin and his eventual publication of his book On the Origin of Species? (10pts)

Darwin waited a long time before he published his beliefs, hypothesis, and theories on evolution. He had multiple opportunities to publish his book On the Origin of Species, but he was always hesitant because he was afraid that he would be shunned for his beliefs, since they didn’t follow the churches ideas. The church believed in creationism, while Darwin believed in evolution. The church played a large part in society so when Darwin, as well as other scientists, came out with their theories on evolution; they were looked down upon.

Krystal Morrice

February 7th 2013