Chapter 19 & 20

1. Sympatric speciation & Microtubules

Sympatric speciation is when new species form within one environment without any geographical barriers getting in the way. One way that sympatric speciation can occur is through polyploidy (when an organism inherits three or more sets of every chromosome) and this happens through the nondisjunction of chromosomes during mitosis or meiosis. Nondisjunction is when spindle fibers, which are composed of microtubules, don’t attach correctly to a chromosome which causes the chromosome to defectively separate.

2. Endosymbiosis & Atmospheric Gases

Endosymbiosis is when an organism of one species lives out its life inside another host species, and the interaction benefits one or both of them. Chloroplast and mitochondria were formed through endosymbiosis. Chloroplasts are used for photosynthesis and photosynthesis uses Co2  and produces O2 and O2 is an atmospheric gas.

3. Adaptive Radiation & Character Displacement

Adaptive radiation occurs when many species emerge from one common ancestor and this occurs through character displacement. Character displacement is when only the individuals that have the best traits are able to survive and reproduce and therefore pass on their traits while the weaker individuals die and eventually become completely extinct. In character displacement, the allele frequencies change and this causes evolution.

4. Proto-cells & Uracil

Proto-cells are the transitional forms between simple organic compounds and the first living cells. These cells consist of membrane bound sacs which contain enzymes and systems of metabolism. Protocells are self-replicating meaning that they had DNA and RNA protein systems and in RNA there is uracil, a nucleotide base, which differs from RNA and DNA.

1.Prezygotic and Postzygotic isolation mechanisms:

Prezygotic

- Mechanical Isolation: physical incompatibilities which deter them from mating

- Temporal Isolation: Cannot mate because the timing of reproduction is different

- Behavioral Isolation: Courtship displays are ignored because they are not recognized

- Ecological Isolation: There are geographical separation which prevents them to mate

-Gamete morality: Gametes are incompatible, so no fertilization.

Postzygotic

-Hyprid inviability: Hybrid emboryo die early before they can reproduce

-  Hybrid sterility: Hybrid individuals can’t make functional gametes.

2. Compare and Contrast Gradualism and Punctuated Equilibrium:

Gradualism is when speciation occurs slowly through small changes over a long period of time while punctuated equilibrium is when that speciation occurs abruptly through directional selection, genetic drift, bottlenecks, and the founder effect.

3. Miller’s Experiment:

Water, methane, hydrogen, and ammonia are put into a reaction chamber and zapped with sparks which caused simulating lighting striking on earth. Then in a week, amino acids and other organic compounds formed inside the reaction chamber, which led to Miller suggesting that this was what occurred billions of years ago, defining chemical evolution.

4. Endosymbiosis:

- The mitochondria resembles bacteria in size and structure.

- Chloroplasts resembles the cunobacteria

- The amoeba’s were become symbiotic when they were infected by bacteria and led them to rely on bacteria to create an essential enzyme.

5. Cladogram

totals: kangaroo- 5

lamprey -1

rhesus monkey- 6

bullfrog-3

human-7

Snapping turtle-4

tuna-2