Unit 2 Test

Today is October 16th. The day of Unit 2 test. This test is mainly about the modern theory of evolution, evidence of evolution, natural selection, Hardy-Weinberg law of genetic equilibrium, and labs that we have done in class. The format of the test is 30 multiple choices and one free response.

After taking this test, I truly comprehend that knowledge is cumulative. We can not forget about previous concepts while learning new things. I need to work more on connecting these concepts together and constantly reviewing them. Moreover, labs are important. Not only labs themselves, (like purposes, procedures and etc.) but also the background information of labs (AKA the reading section for each lab's handout). These reading sections contain critical information of labs that will help us to understand the concepts more. All in all, for future study, I should connect concepts, constantly review and carefully read each lab's handout.

Population Genetics and Evolution

For today's class, we learnt about the Hardy-Weinberg law of genetic equilibrium and we studied the relationship between evolution and changes in allele frequency by using our class to represent a sample population. 

During this lab, we used the class as a population, the allele frequency of a gene controlling the ability to tast the chemical PTC could be estimated. If the person could tatse the bitterness, then the person is evidence of the presence of a dominant allele in eitherr the homozygous condition (AA)  or the heterzygous condition (Aa). If the person could not taste the chemical, then the person is evidence of the presence of homozygous recessive alleles (aa).

p= the frequency of the chemical tasting allele in the population

q= the frequency of the nontasting chemical allele 

phenotype= physical trait 

p^2 +2pq+q^2 = 1 (Population) 

p+q= 1 (frequency) 

p^2= AA

2pq= Aa

q^2= aa   

Hardy and Weinberg stated that if 5 conditions are met, the population's allele and genotype frequencies will remain constant from generation to generation, meaning maintaining equilibrium. 

These conditions are: 

1. The breeding population is large. The effect of chance on changes in allele frequencies is thereby greatly reduced. 

2. Mating is random. Individuals show no mating preference for a particular phenotype. 

3. There is no mutation of the alleles. No alteration in the DNA sequence of alleles. 

4. No differential migration occurs. No immigration or emigration. 

5. There is no selection. All genotypes have an equal chance of surviving and reproducing. 

Parents' Day!

The preparation for Parents' Day was to read three articles about natural selection in humans. These articles articulate  natural selection in humans from three different aspects: averageness, symmetry and masculinity. On Parents' Day, we did an interesting activity with our parents. We all observed pairs of person that have slight changes in facial features and determined which one appeared more attractive within that partucular group. Based on our data, we could state that we all agreed that women are more attractive to men who have more feminine features. Moreover, in general, we all think that a person with more feminine features is not only considered as attractive, but also considered as genuine and welcoming. Nevertheless, during ovulation, women are more attracted to men with masculine features; since, men with masculine features appear to be able to father healthy offspring.

Missing Link --- Q1 Paleo project

Here is our Website:
http://linfei2015.wix.com/avemsecundo
Created by Jasmine Yang and Linfei Liu

Why are they different?

For today's class, we did an interesting activity. The whole class divided into groups of two. Each group had a bag of shells. These shells were all collected from the same sea area. Task for each group was to differentiate these shells by various characters, such as patterns, colors and so on. For first round, Jasmine and I put shells into different groups based on their patterns.Whether the lines on the shells were vertical or horizontal. For second round, we differentiated the shells by colors. Some of them were whitish pink, some of them were dull brown. For the last round, we divided the shells into different groups based on size.

Furthermore, we realized that about 70% of these shells had holes on them. These holes indicated that animals lived inside the shells were attacked by other organisms outside of the shells, which could use their tongues as drills to dig holes on the shells. Thus, the shells were empty. Nonetheless, difference in shells was not an evidence of evolution. It was more like a result of mutation. Based on different environment, physical appearances of shells would alter. Due to mutation, shells were able to pass down thes genes that helped them to survive and reproduce.

For further learning, we did a lab by comparing what percentage of salt in water would affect the growth of brane shrimp eggs.

Vertical line pattern

Spiral

Bigger size

MORE SHELLS! 

 

Survival of the sickest I --- Fava Beans

Chapter 4 of Survival of the sickest is about fava beans. Despite fava beans are type of food, they can be lethal to some people. The beans contain two sugar-related compounds called vicine and convicine. These produce free radicals (un-paired electrons) and some people that eat fava beans experience where the hydrogen peroxide formed from the vicine and convicine attack the red blood cells and break them down. Therefore, fava beans are deadly to people with favism.

Favism is a hereditary disease. This means it is passed on through the genes from a parent to the child. It leads to a form of anaemia. As it is linked to the X chromosome, most people who suffer from it are males. Females are less common than males because of XX chromosome. Favism is also known as G6PD, glucose-6-phosphate dehydrogenase deficiency. People with G6PD have a different circulation of sugar in their body. More red blood cells in their bodies will be destroyed because of G6PD.

Besides fava beans, this chapter also explains about plants in terms of their defense systems and birth control. For defense, plants are good at being toxic. For example, every spicy pepper has something in it called capsaicin. This is what makes it spicy; however, it is also considered poison. To avoid poison, people develop their ability to taste bitterness in order to avoid these poisons in plants. Keep in mind, not everything we eat is good for us. It might be dangerous to our healths, such as fava beans and celery.

Here is a mind map for Chapter 4: 

Summary of Ch. 4 

The Devil---Fava Beans

glucose-6-phosphate dehydrogenase

Red cell burst 

Evolution --- Quiz

Evidence of Evolution Quiz 

1. The following picture presents one of the evidences for evolution, which is the fossil record. The comparison between these fossils shows us that present-day species have morphological features of species in the past. These features further prove that present-day species have been modified from ancestral form. Fossil record is an important evidence for evolution. Even though fossil record is incomplete, fossils can show many evolutionary changes. Some of these changes are gradual, such as the following picture. The picture shows revolutionary changes of species from terrestrial to aquatic.Besides fossil record, homology is also an important evidence for evolution. In this case, limb is the homologous structure between Mesonychid, Ambulocetus, Rodhocetus, and Basilosaurus. Despite Mesonychid lives on land and Basilosaurus lives in water, this picture clearly presents the gradually evolutionary change from the limbs of Mesonychid to the fins of Basilosaurus. 

2. Marsupials begun from North America.  

3. Dragonflies, birds and bats all have the ability to fly. Between birds and bats, limbs under their wings are homologous. This homologous structure proves that they are descendants from a common ancestor. Although dragonflies have legs, they do not have limbs under their wings.This difference of dragonflies' underlying structure indicates that dragonflies are evolved from different ancestral structure. However, dragonflies do contain many similarities of birds and bats. They are all able to fly, and they all have light, broad surfaces. These organisms present convergent evolution. 

4.  During the Common Descent Lab, we are able to link species together by examing the amino acid sequence in the protein, Cytochrome C. Gens are made of DNA and are inherited from parent to offsprings. Some DNA sequences code for the amino acid sequence of proteins. Therefore, by comparing the amino acid sequences, we are able to make a cladogram to show the relationships between species. With the help of cladogram, we are able to see the evolutionary changes between species. For example, the difference between amino acid sequences of cow's and horse's is only, which indicates that cows and horses might be evolved from a common ancestor. This is the reason why the Common Descent Lab shows DNA as evidence of evolution. 

5. As mentioned in Inner Fish, Dr, Shubin found a perfect transitional organism between fish and amphibians, Tiktaalik. In order to prove that Tiktaaklik is the missing link between fish and amphibians, Dr. Shubin proved himself by applying homology. Homology is the study of similar body structures. These similarities imply that single ancestral species branch into many closely related cpecies. For Tiktaalik, the most amazing thing is that instead of having fins on the sides, it has short forearms that enable it to do push-ups. These forearms are similar to the limbs of amphibians. By comparing these homologous structures, we could define Tiktaalik as the perfect transitional organism between fish and amphibians.