Chapter 19 and 20

II. Connections
1. Sympatric Speciation is a speciation model that occurs within the home range of an already existing species, or in other words without the presence of a physical barrier. This is caused by polyploidy, in which individuals inherit three or more sets of chromosomes of their species due to the failure of mircotubules to attach to chromosome kinetechores during mitosis or meiosis. With the extra chromosomes, the offspring are unable to mate with their parent species but can reproduce asexually or with another polyploid individual, resulting in the creation another species of organisms.

2. Endosymbiosis is a theory for the origin of organelles such as the mitochondria and chloroplasts that claims that heterotroph cells consumed autotroph cells due to their ability to engage in aerobic respiration, but since they nefused to digest them, the consumed cells remained and lived out their lives in the host cell. Each cell in this interaction is benefited, classifying it as a symbiotic relationship. The reason for heterotrophs preying on aerobic prokaryote cells was due to the alteration of atmospheric gases by the emergence of photosynthesis, for they introduced free oxygen, therefore allowing eukaryotic cells to evolve from prokaryotes.

3. Adaptive radiation is a type of speciation that is characterized by a burst of divergences from a single lineage that results in a entirely new species. This occurs either when a lineage uptakes a vacant adaptive zone (set of  niches) or competes with other resident species well enough to force them adopt another niche. This latter incident refers to character displacement, which is a phenomenon in where a species will adopt a new niche if its original one conflicted with that of another species, relating to Gause's principle in that no two species can share the same niche.

4. Proto-cells comprise the transitional forms between simple organic compounds and the first living cells. They are self- replicating membrane-bound sacs that have systems of enzymes and other agents of metabolism. It is believed that their ability to self-replicate arose with the spontaneous assembly of RNA subunits due to an increase in temperature, and the formation of an enclosed membrane due to the moistening of protein chains.

III. Essentials
1. Prezygotic Mechanisms
    -Mechanical Isolation: A species's body parts are not physically compatible to another species for the purpose of mating, or pollinating

    -Temporal Isolation:When specific timing for reproduction differs between populations, those populations cannot interbreed

    -Behavioral Isolation: Since certain species of organisms include courtship displays in their reproductive process, species that are not pre-wired to perform or recognize a particular courtship display will not be able to interbreed with a similarly related species that is pre-wired to do such.

    -Gamete Morality: Gametes of different species are incompatible, so no fertilization occurs

Postzygotic Mechanisms
    - Hybrid Inviability: Hybrid embryos die early or the new individuals die before they can reproduce

    - Hybrid Sterilty: Hybrid individuals are unable to produce functional gametes


2. The gradual model of speciation, known as "gradualism", holds that speciation occurs as a result of slight morphological changes of individuals throughout a relatively long span of time. On the contrary the punctuated model of speciation, or “punctuated equilibrium”, claims that most morphological changes occur in a smaller, more brief geologic period, due to factors such as directional selection, genetic drift, the founder effect, and bottlenecks, for such accelerate the rate of speciation.

3. In the attempt the prove the hypothesis formed by chemical processes, Stanley Miller placed water, methane, hydrogen, and ammonia in a reaction chamber. Then he disrupted the mixture by circulating it and zapping it with sparks, to simulate lightning strikes. Amino acids and other small organic compounds were present in the chemical mixture a week later, therefore affirming the hypothesis.

4. A critical example that supports the endosymbiosis theory is the chance discovery of Jeon Kwang in 1966, in where his culture of amoebas was infected by rod-shaped bacteria cells, which caused some cells to die, while the the others, which were smaller, just grew more slowly. After 5 years of maintaining the infected culture, the infected amoebas were producing additional bacteria cells while thriving. When exposed to antibiotics, only the bacteria and non-infected cells perished, not the amoebas. Evidence then showed that infected cells became unable to manufacture a specific enzyme, so instead they depended on their invader bacterium to synthesize it, therefore exemplifying a endosymbiotic relationship.

5. The cladogram is on the cards we turn in for the chapters…

Chapters 17 and 18

II Connections
1. During Prophase I of meiosis, the two duplicated homologous chromosome pairs are temporarily attached to one another at the chaism. While connected, the two homologous chromosomes can exchange genetic material at their junction points, which is called crossing over. Thus, due to this event, variation in genes are produced for the eventual offspring, influencing the whole population's allele frequency, or relative abundance of alleles of a specific gene among individuals of a population. Specifically, moving a population from a specific allele frequency state called genetic equilibrium, due to the new diversity in alleles brought on by events such as crossing over.

2. Analogous structures are different responses of different body parts to similar challenges, such as the common challenge of flight faced by bats, birds, and flies that had a part in  influencing their development of various wing structures. In terms of natural selection, the selective progression of traits favorable to a certain environment due to competition, both analogous structures and natural selection occur as a result of the nature of the environment.

3. A Gene pool is a complete set of unique alleles in a given population, for the individuals of a population inherit the same number and kind of genes from their parents. if a population of organisms were to experience a bottleneck or drastic reduction in population size due to various environmental pressures, the gene pool of that population will be relatively less diverse than before. Since a reduction in population size occurs, there are only few individuals left to reproduce and pass on their own genes, and renew the population size, which is why diversity of the gene pool is less.

4. Balanced polymorphism is the persistence of two or more alleles at relatively high frequencies within a population. This allele frequency is maintained in certain populations under certain conditions, for if the predators of a specific population develop a search image, variation in exterior aspects of the prey would more favorable for survival under this circumstance. Therefore, balanced polymorphism is sustained because of the benefits of being heterozygous or phenotypically varied.

III. Essentials
1. -Natural populations, by nature are able to increase in size over time, due to their inherent reproductive capacity
    - Population size is checked from consistently growing due to the exhaustibilty of limited resources
    - Conclusion: Eventually, competition will arise between individuals since there are
    - Individuals  share a common gene pool with respects to its population
    - Genetic Variation within a population begins with alleles, or slightly different forms of genes that result from mutations
    - Conclusion: Certain traits prove more able to secure survival than counterpart traits of different alleles, and so the alleles that encode for the more fit traits will become more frequent in the population of that environment over time.
    - Conclusion: Natural Selection is the result of the trait variation of a population, due to certain environmental factors, that in all could produce evolution of that population.

2. 1.Chemical, molecular evolution that resulted in the origin of life 4,600 million years ago
    2. Accumulation of oxygen in the atmosphere that produced eukaryotic cells
    3. Breakup of Gondwana and Pangea that created environmental differences and initiated mass extinction
    4. Recurrent Ice Ages that caused mass extinctions
    5. Major Crustal movements that created various biomes and therefore diversity of life

3. "Individuals don't evolve, populations do", is the accurate view of evolution, for natural selection and other types of evolution result from changes in the DNA of an individual, so no organism can evolve itself because no individual can alter their own DNA. Rather organisms evolve as a result of the changes of a parent's DNA, and if these changes do not hinder the survivability of the resultant offspring than that new allele could be passed on, thereby evolving the population(micro evolution)

4. Phenotypic variation is generated by a number of factors, such as genetic mutations in where the base sequence of DNA is alter slightly, not to change survivability or reproduction. A second source would be crossing over during prophase I of meiosis because it creates numerous unique gene combinations in the produced gamete. Also, independent assortment of homologous chromosomes during meiosis I, mixes orientation of maternal and paternal chromosomes and also helps create genetically varied gametes. Furthermore, fertilization of two gametes from two different individuals, combines alleles of two random gametes, explaining why phenotypic expression of traits also vary between siblings. Lastly, chromosome mutations, or alterations in the structure of chromosomes, results in the loss, duplication, or repositioning of genes.

5. p²(AA) + 2pq(Aa) + q²(aa) = 1.0

p and q are the frequencies of the dominant and recessive alleles (A, a), respectively.  

Conditions: 1. No mutation exists
                  2.The population is infinitely large
                  3..The population is isolated from ll other populations of the species
                  4. Mating is random
                  5. All individuals survive and produce the same number of offspring