1.1
Meiosis I
The first meiotic division: diploid → haploid
Prophase I: Chromosomes condense, nuclear membrane dissolves, homologous chromosomes join and occurs crossing over.
Metaphase-I: the homologous chromosomes align in the middle of the cell. Spindle fibers from the centrosomes connect to the chromosomes.
Anaphase -I: Spindle fibers contract and split the homologous chromosomes, moving them to opposite poles of the cell.
Telophase -I: Chromosomes decondense; cell divides to form two haploid cells.
1.2 Meiosis II
The second division: separates sister chromatids (these chromatids may not be identical due to crossing over in prophase I)
Prophase II: Chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before)
Metaphase-II: the chromosomes align in the middle of the cell. Spindle fibers from the centrosomes connect to the chromosomes (at the centromere)
Anaphase-II: Spindle fibers contract and split the sister chromatids, and moves them to opposite poles of the cell.
Telophase-II: Chromosomes decondense,cells divides again to form another 2 haploid daughter cells. Final: 4 new cells.
2. The differences:
Mitosis:
- has 1 division per cycle
- one cell produces 2 new cells
- the genetic information in the mother-cell and the daughter-cells are the same. ( the number of chromosomes is also the same)
- it occurs in somatic cells
Meiosis:
- two divisions per cycle
- one cell when divides produces 4 new cells
- the new cells have different genetic information. mixes the genetic material from the parent cells
- the number of chromosomes of the daughter cells is half of the mother's.
3. Prokaryotic organisms don't divide through mitosis, they use a different process called binary fission. Only eukaryotic organisms, or those whose cells have a defined nuclei, undergo mitosis. Bacteria, for example, are prokaryotic organisms that use binary fission.
4.
It can't occur. Cross over is the exchange of DNA between homologous chromosomes. That will result in recombinant chromosomes during sexual reproduction. It can't occur on different chromosomes because they don't code for the same genes.
5. There are a lot of different theories about that, but it's mostly believed that meiosis must evolve before sexual reproduction. That's because The cell replicates their information first and then divides. Plus the cell does that even though it didn't recombine DNA with another organism (sexual reproduction).
Archaea I think this is the right choice
The most probable future changes in the global climate are:
- Global warming;
If the levels of CO2 and methane increase enough in the atmosphere to be able to intensify the Greenhouse effect, than some portion of the ice on the planet will melt because of the rising temperatures, thus lifting up the sea level, creating more unpredictable weather with larger and stronger storms, but also making the mainland much drier. This would be a scenario if the continents are arranged like they are now, but if there isn't a sufficient mass of land on and around the poles, than all of the ice will melt and the sea levels will rise so much that the planet will come in the ''water planet'' scenario, and it will have wet tropical climate pretty much everywhere on the planet.
- Ice Age;
If there's a disruption in the warm ocean streams and some of them disappear, or the levels of nitrogen or oxygen increase in the atmosphere, the Earth will start to cool off, thus coming to a situation of an Ice Age. In this kind of situation, there will be large ice sheets on and around the poles that are stretching much further towards the lower latitudes, as well as mountains all over the world that are covered in snow and shaped by glaciers.
Answer:
The presence of similar <u>fossils(B)</u><u> </u> and <u>rock formations(C)</u> on several different continents supports the theory of Continental Drift.
Explanation:
Alfred Wegener observed fossils of organisms that were not supposed to have survived in the climate of where they were found. Other key findings is that he found fossils of organisms that were found in one continent and the same fossils found on another continent whose edges seem to fit together.
He also observed rock formations or stratas of mountain ranges in one continent seem to fit together with another continent.
<u>Added note:</u>
Even if Alfred Wegener had these evidences to present, his theory of Continental Drift was rejected mainly because he could not explain the mechanism of how the super continent (Pangaea) split.
I believe it is behavioural isolation. When there are changes within a certain species, e.g. new birdcalls are formed in certain individuals in a species, "traditional" birds may not like such mating calls and only choose to mate with the more common birdcalls from majority of the birds. There are also some birds that may like the new birdcalls, and choose to mate with birds with those birdcalls. They become genetically isolated as they continue such behavior. Eventually, through genetic drift and other mutations, different species form from a single specie.
Hope this helps! :)
