II. Connections
1. Sympatric Speciation & Microtubules: Sympatric speciation is when a species may form within a home range of an existing species, in the absence of a physical barrier. Reproductive isolation is key for speciation to occur. Reproductive isolation maight happen within a few generations through polyploidy. Polyploids originate through spontaneous induced hybridization between closely related species or doubling of the chromosome number. Homologous chromosomes failed to separate at meiosis, when the microtubule spindle fibers did not pull apart the chromosomes, and it produced fertile polyploids.
2. Endosymbiosis & Atmospheric Gases: Endosymbiosis is a theory that states a symbiont species lives out its life inside a host species, and the interaction benefits one or both of them. By this theory, eukaryotic cells evolved after the noncyclic pathway of photosynthesis emerged and permanently changed the atmosphere. BY 2.1 billion years ago, certain prokaryotic cells had adapted to the concentration of some atmospheric gases, such as oxygen, and were already engaged in aerobic respiration. The ancestors of eukaryotic cells preyed upon some aerobic bacteria and were parasitized by others. At that time, endsymbiotic interections began.
3. Adaptive Radiation & Character Displacement: An adaptive radiation is a urst of divergences from a single lineage that leads to many new species. It requires adaptive zones, or a set of niches that come to be filled by a group of usually related species. Either the lineage enters a vacant adaptive zone or it competes with the resident species will enough to displace them. Sometimes as a result of this competition, a species will develop morphological differences to reduce the competition. This is known as character displacement.
4. Proto-cells & Uracil: Proto-cells were transitional forms between simple organic compounds and the first living cells. These were no more than membrane-bound sacs that contained systems of enzymes and other agents of metabolism, and that were self-replicating. It all started with spontaneous formations of lipids, carbohydrates, amino acids, proteins, and nucleotides under abiotic conditions. Then, the formation of lipid spheres and protein RNA systems appeared. Because the one difference between RNA and DNA is a single -functional group of uracil, the RNA thus evolved into DNA, using RNA to create enzymes and proteins. Proto-cells emerged and the living cells.
III. Few Essentials
1. Prezygotic and Postzygotic Reproductive Isolation Mechanisms
- Mechanical Isolation: individuals can't make or pollinate because of physical incompatibilities
- Temporal Isolation: Individuals of different species reproduce at different times
- Behavioral isolation: Individuals of different species ignore or don't get the required cues for sex
- Ecological Isolation: Individuals of a different species live in different places and never meet up
- Gamete Mortality: Gametes of different species are incompatible, so no fertilization
- Hybrid Inviability: Hybrid embryos die early or the new individuals die before they can reproduce
- Hybrid Sterility: Hybrid individuals can't make functional gametes
2. The gradual model of speciation holds that species originate by slight morphological changes over time spans. The model fits with many fossil sequences. The sequence reflects gradual morphological change. The punctuation model of speciation offers a different explanation for patterns of speciation. Most morphological changes are said to evolve in a relatively brief geologic period, within the tens to hundreds of thousands of years when populations are starting to diverge. Directional selection, genetic drift, the founder effect, bottlenecks, or some combination of them favor rapid speciation.
3. Stanley Miller was the first to test the hypothesis that the simple compounds that now serve as the building blocks of life can form by chemical processes. He put water, methane, hydrogen, and ammonia in a reaction chamber. He kept circulating the mixture and zapping it with sparks to stimulate lightning. In less than a week, amino acids and other small organic compounds had formed in the chemical brew.
4. Evidence to support emdosymbiosis
- rod-shaped bacterium infected culture of amoeba discoides
- cells grew slowly and became vulnerable to starving to death
- five years later, infected amoebas were harboring many bacterial cells, yet all thriving
- infection-free cells got a nucles from an infected cell
- more than 90% survived when a few bacteria were included with transplant
- infected amoebas had lost their ability to synthesize an essential enzyme
- depended on bacterium to make it for them
- mitochondria resemble bacteria in size and structure
- chloroplasts resemble cyanobacteria
5. on separate sheet of paper
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