Monday, September 24, 2007

Evidence of Evolution by Natural Selection (cont.)

Evidence of Evolution by Natural Selection

Homologous Structures:

Homologous structures are bones with similar structures and similar developments but different functions. They have different niches, or jobs due to variations in the population that accumulated over time and served as adaptions.

In the picture above, there is a homologous structure in all six individuals most likely because they all have a common ancestor and over time have evolved from their ancestor to carry out different functions.

Comparative Embryology:

Comparative embryology is the similar development of embryos in closely related species.

At different stages of development, there are similar structures that exist in vertebrate embryos. In the individuals above, there is a gill pouch present in each vertebrate. However, that does not mean that humans have gills because we don't. It is really thyroid glands, not gills that is in humans. Comparative embryology shows species with similar ancestors.

Molecular Record:

Molecular record is comparing DNA and protein structures. All organisms have the genetic codes DNA and RNA. The sequences are more similar in species that are closely related than those that are distantly related.

The further apart species are, the more protein structure changes. DNA changes as protein structure changes because of agents such as mutation.

"Family Trees":

Closely related species branched off from the same ancestor and share same line of descent. This was also one of Darwin's theories.

Testable Hypotheses
Peppered Moths:
In the year 1848, 5% of the population was dark colored moths while 95% was light colored.
In the year 1895, 98% was dark colored while 2% was light colored.
In the year 1995, 19% was dark colored while 81% was light colored.

What was the reason for the changes in the number of dark and light colored moths?
  • In the early 1800s, England was not so industrialized yet and pollution was still low. The trees had light colored bark so the light colored moths had a better advantage and a better survival rate than dark colored ones.
  • In the late 1800s, England started to become more industrialized and factories increases. These factories caused trees to become soot coated, the bark was darker. The dark colored moths were then camouflaged and survived more than light colored ones.
  • Then in the mid 1900s, the air started to become cleaner due to clean air laws. Trees began to have lgiht colored barks and once again light colored moths increased in the population.

Industrial melanism- melanin is the brown color in all organisms.

Genome Sequencing:

Are humans closely related to monkeys???

Genome sequencing shows us the evolution of humans and how we share a common ancestor with apes.

Orangutans, gorillas, and chimpanzees have 48 chromosomes while humans have only 46. So where's the missing chromosomes?

In order to prove that humans are related to apes then humans must have a fused chromosome, 23 pairs. A chromosome must be found that is in the middle and another one that is inactived.

Well that is exactly what was found in humans. Chromosome 2 shows the fusion that took place. In chromosome 2, there are telomeres at the ends and two that have fused together in the middle. One inactive centromere also exists in chromosome 2.

Here is proof that apes and humans really are related.

Need any more proof???

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