ReCharde Johnson
Professor
Grymes
NCLC
120
Learning Log 5: Déjà
vu: How and Why Evolution Repeats
itself
Synopsis
We can tell that Howler monkeys developed trichromatic color
vision independently from “old world” monkeys by looking and the differences
between the two duplicated genes. After a duplication event, because of the
steady beat of mutation, each copy of a gene will accumulate changes. The older
the duplication event, the greater the divergence will be between the texts of
the two sister genes. In all
Convergent evolution is the appearance of apparently similar
structures in organisms of different lines of descent. In all sorts of animals,
we see similar traits that evolved as independent inventions. The flippers of
penguins, seals, and dolphins all serve a similar purpose in swimming, but each
group of animals evolved from different ancestors that didn’t have flippers. The
wings of pterosaurs, birds, and bats also evolved convergently, there wings
differ in architecture, with different parts of the forelimb contributing the
major portion of the wing surface in each group of animals. This is significant
because this shows how different species can possess similar traits.
Albinism in cave fish is most easily explained by the
relaxation of natural selection on body color, since the cave fish dwell in
dark caves there isn’t a need for color, because it’s impossible to see what
color any animal is. Relaxation of natural selection refers to the lack of need
for a specific trait because it doesn’t play any role in reproduction or
survival.
First, in the fish evolutionary tree, the Antarctic and
Plus, the two antifreezes are produced by
entirely different processes. The Antarctic fish, repeats of threonine-alanine
or threonine-proline-alanine are encoded in multiple tracts, which are spacers
are positions where the protein is processed into smaller antifreeze peptides.
In the Artic fish, the spacers have an entirely different sequence and are
processed by a different enzyme. So, while antifreeze peptides are incredibly
similar, they are produced from proteins with different internal spacers that
must have had different origins. The antifreezes are analogues, not homologues.
Similar conditions that exist in different orders, families,
and species cause evolution to repeat itself. The repeated evolution of traits
is a product of both chance and necessity, the probability of equivalent
mutations and the similarity of the conditions of selection.
For any new mutation there are three possible fates, it may
be actively preserved, actively rejected, or may be neutral and ignored by
selection. Under natural selection conditions and the conditions of selection
upon the traits they affect is each fate realized.
7. From the section Chance: “identical or equivalent mutations will
arise repeatedly by chance,”
explain somewhat carefully just where the number 750 years comes from. That is explain how one can estimate
that about once in 750 years a
herring gull chick will be born able to see UV light.
According to long-term population surveys, many species
consist of 1 million to more than 20 million individuals. With annual
reproduction, a plentiful species like a herring gull will produce at least 1
million offspring in a year. Divide this into the rate of one mutation per 750
million birds; the result is that the serine-to-cysteine switch will arise once
every 750 years.
8. From the section Selection: “their fate…will be determined by the
conditions of selections upon the traits
they affect,” explain why the mutations at basses 270, 260, and 269 all coded for either violet vision or UV
vision in a large number of species
of birds. That is, of the possible mutations starting with AGC [what are those 9?], why is it that
the 2 of the 9 mutations that produce either
violet or UV vision are what we see but the other 7 are not seen?
AGT serine, AGA arginine, AGG arginine, ACC threonine, ATC
isoleucine, AAC asparagines, TGC crysteine, GGC glycine, CGC arginine. The only
explanation for the selective occurrence of cryseine and serine (UV and Violet
vision) is natural and sexual selection. Repeated evolution of crysteine at
this position occurs because similar conditions, favoring the capability,
favoring the capability of UV vision, have existed and do exist in different
order, families and species of birds.
This is an evolutionary
advantage because it allows different species to be able to adjust to different
habitats; if the same mutations were always favored than some species would die
out because they wouldn’t be able to use them in their habitats. For example,
color vision in cave fish isn’t a favored mutation because there is no need to
see in color in deep dark caves.
Take
Away Idea
From
chapter six there were many ideas that you could take away, but one idea sticks
out more than the rest. Given sufficient time, identical or equivalent
mutations will arise repeatedly by chance and their fate will be determined by
the conditions of selection upon the traits the affect.
Most
challenging concept
The
most challenging concept in this chapter was the mutations of bases 270, 269,
and 268. I don’t understand how there are all these mutations in birds opsin
genes but they usually see in violet range. The author didn’t fully explain
this point in my opinion.
A
seminar question
What
makes antifreezes analogues and not homologues?
Competency
Throughout the chapter the communication
competency has been clearly displayed. First, the author communicates
effectively throughout the whole chapter, especially while explaining how the
howler monkeys where able to gain trichromatic vision. Also, throughout the
chapter, the author used good scientific language to get his points across, but
he also explained the scientific language for anyone who was scientifically
challenged so they wouldn’t be lost. Lastly, the author displayed the
communication competency by strategically organizing the different sections so
the chapter flowed; this made the chapter easier to read and kept me
interested.
Also, the strategic problem solving
competency was displayed throughout this chapter. First, the author displays
the strategic problem solving competency by defining his problem, one of the
problems in the chapter was how the howler monkey got color vision. Also, the
author suggested different ways that the monkey could have gained color vision
but then he told us how the monkey actually was able to gain color vision.
Lastly, the author displays the strategic problem solving competency by
explaining the process of how the monkeys went from having dichromatic to
trichromatic.
Connection
The idea of convergent evolution relates a
lot to everyday humans. Just like in animals different people can share
different traits but belong to different racial, class, or religious groups,
for example my friend Beth is a Caucasian female but we share some of the same
physical characterizes such as eye color and hair color. Although, my roommate
is Muslim, he and I share some of the same hobbies.
Vocabulary
Convergent evolution—the appearance of
apparently similar structures in organisms of different lines of descent
Ribonuclease—any of the class of enzymes
that catalyze the hydrolysis of RNA.
Neurotoxin—a neurotoxic substance, as
rattlesnake venom or the poison of a black widow spider.
Key
Concepts
Different species containing
similar traits or structures.
Mutations fates are determined
by the conditions of selection upon the traits they affect.
Identical or equivalent
mutations will arise repeatedly by chance