Breeding Bunnies

1.     My hypothesis stated the gene pool of the bunny population would shift and eventually the dominant genes would be the only one present.

2.     The results of the lab confirm my hypothesis, since at the end of five generations; the dominant allele was the only one remaining.

3.     At the beginning of the lab, the number of alleles for the dominant characteristic equaled the number of alleles for the recessive characteristic. In five generations, all the bunnies with recessive alleles died, leaving only the bunnies with the alleles of the dominant characteristic.

4.     Since the initial number for each allele was equal, the gene frequency of both dominant and recessive alleles was 0.5. In the next two generations, the frequency of the dominant allele increased by 0.2, meaning that the gene frequency for the recessive allele decreased by 0.2. In the fifth generation the gene frequency of the dominant allele was 1 while the other 0.

5.      Emigration and immigration affect the gene frequency of F and f  by decreasing and increasing respectively the number of alleles and therefore affecting the rate of the shift. Once there is a great amount of emigration, the size of the population decreases, and the number of alleles also chances, hence the gene pool shift occurs in a fast manner. If there is immigration, the population increases and these new members add to the gene pool, decreasing the rate of the shift. This may be simulated in the activity by adding beans (which represent alleles) and removing beans from the sample.

6.     The same trend occurred to the other group’s sample, but instead of having the dominant allele as the only one remaining, they had the recessive allele. This was due to the different circumstances in which the bunnies live in. In my activity, since they lived higher up in the mountain, the ones with thick fur (represented by FF) survived better since it was colder, whereas the other bunnies lived at the bottom where it is warmer and do not need thick fur, represented by ff.

7.     The results of this simulation are an example of evolution because of the shift in the gene pool. Since the bunnies migrated, they had to adapt to the new climate in order to survive. By that the alleles which were best suited for each new environment were the ones that remained after several generations, now differentiating the bunnies from the top of the mountain, to the ones at the bottom.

Brazilian Population

  Brazil's population age structure has been constantly
changing throughout the past years. As seen in the first figure, the population in 1990 formed almost a perfect pyramid with a high number of children and a very small percentage of the population being older than 60 years old. The second figure, already shows a significant change with and increase of people belonging to the working/reproductive section and the population older than 60 years old. This demographic change indicates both a decrease in child mortality and an increase in life expectancy.
  The third figure, Brazil's demographic pyramid in 2010 does not change much in shape, though the younger population is decreasing slightly while the older population is constantly increasing. Brazil is therefore in a period where the working group is high and there is a smaller dependency ratio.
  If the population continues to grow in this manner, the aging population will grow significantly while the school-age population will decrease significantly, affecting Brazil's economy and governmental expenditures such as social security and health care programs. Despite the population will continue to grow, though at a slower rate.

Leaves

     Other than adding to the aesthetics of plants and trees, leaves are essential for the process of photosynthesis,  hence necessary for survival. Being thin and flat, maximizes the surface area exposed to light and increases the absorption of carbon dioxide. The rate of absorption of carbon dioxide is controlled by organelles called stomata. Stomata are microscopic pores found on the epidermis of plants. They are boarded by guard cells which regulate the opening and closing of the stoma.

     The leaves in my tree have most of its stomata in the lower epidermis. It has a great number of stomata (297 per millimeter squared) and this allows more carbon dioxide and oxygen to enter the leaf. To prevent water loss due to so many pores, the leaf has a very waxy coat.

 

Adaptation and Survival

The plant I have adopted is a tree. The first great adaptation of trees is that they contain a trunk made of wood. Wood, which is a tough fiber, is used as support, allowing the plant to grow bigger and heavier. My tree's trunk is surrounded by a very thick bark that allows its survival in this environment. It's environment is the cerrado, characterized by the dry climate and due to this region is constantly prone to forest fires. The thick bark prevents the fire from burning the entire tree, and once the fire is over, the burnt bark falls off and a new thick bark is formed. 

Another property that is essential for the tree to survive in this region is it's long roots that must reach groundwater located deep into the soil. Without this groundwater, this plant would not be able to receive water since of the low precipitation rate in Brasilia. In order to conserve better the limited amount of water this plant receives, it has waxy leaves. 

What is perhaps the single most important adaptation of this tree, is the presence of seeds. Seeds can wisthand dryness and therefore they may remain dormant for sometime. And the seed dispersal contributes to the conservation of this species since it can be spread to several environments where they may eventually adapt.

My Adopted Plant

    The plant I have decided to adopt in my senior year of EAB is perhaps one of the oldest trees in school. The buildings have changed and an auditorium has been added, but this tree continues there. It is the first thing one sees when crosses the front gate and it is also responsible for providing a pleasant shade when one wants to sit outside of the classroom. Its common and scientific name are still unknown.
    What makes this tree so special is its trunk; it is very rough and contains cracks troughout. Other than this, it is covered by lichens. The lichens, which are made of algae and fungus is responsible for exchanging gases and other resources with the tree, thus having a mutualist relationship. Mutualism is a type of symbiosis where two organisms benefit from each other. Another interesting aspect about this tree is that since it is located next to another tree, it's branches are pointing toward places other than the branches of its neighboring tree. This occurs in order for the tree to have most of it's leaves exposed to the sun, and this essential for the process of photosynthesis.
   The roots are not visible but since the level of the ground around it is bumpy, the roots are probably thicks, fibrous and long. This is a common characteristic for plants in this region of Brazil, the cerrado, which is characterized by a dry climate and little precipitation. The leaves are smooth, thin, green and the veins are parallel indicating this is a monocotyledonous angiosperm.
    In the next nine months there won't be much change in growth or in the number of branches. It is probable though that seed dispersal will be visible and the tree will lose part of its leaves. This plant is not in its natural habitat, for it is located in the middle of a school with plants very close to it, something that is not very common in the cerrado where the trees are scarce and separated.

Science is a puzzle

As children we love playing with puzzles. We start with puzzles that only have ten pieces and as we complete the easier ones we try harder ones reaching up to 1,000 pieces. It may take days to finish it, but stubborn as children may be, they will not give up until it is finished. Science is also a puzzle, but without a determined amount of pieces and therefore proves to be the hardest puzzle to solve. Science involves everything humans know to exist and because of this vast area of study, this puzzle will never be completely solved. Instead, each new discovery, each new theory and each new invention add a piece to the puzzle and help create a better picture of the world we live in.

Why IB bio?

Biology is fascinating; in school it may be considered a world of its own and yet it is actually everywhere. When studying biology, one studies the environment in which he or she lives in, the history of evolution, genetics and human own physiology. Therefore it is only through biology that one can really understand his or her nature and identity. Other than being intrigued with what is studied in this class, IB biology is the perfect subject to perform several labs. Since we are required to do sixty hours of labs in this class, we have enough opportunity to experiment what has already been tested and create our own experiments.  These are some of the reasons why I chose biology as part of my IB diploma.