DBQ on p. 136 – February 4, 2013
1) Compare the DNA content of the bog mosses.
The S. aongstroemii, S. balticum, S. fibriatum, S. teres, S. tundrae, and S. warnstorfii all have 19 chromosomes and masses ranging from 0.42 to 0.48 DNA/pg.
2) Suggest a reason for six of the species of bog moss on the Svalbard islands all having the same number of chromosomes in their nuclei.
A reason why the six species of bog moss on the Svalbard islands all had the same number of chromosomes could be because they all live in the same environment.
3) S. arcticum and S. olafii probably arose as new species when meiosis failed to occur in one their ancestors. a) Deduce the chromosome number of nuclei in their leaf cells. Give two reasons for your answer.
The chromosomes number of nuclei in their leaf cells is 38 because if meiosis failed to occur then there would be twice as many chromosomes and also because the mass of the DNA for those two species is approximately double the masses of the other species (with 19 chromosomes). b) Suggest a disadvantage to S. arcticum and S. olafii of having more DNA than other bog mosses.
A disadvantage could be that there would be increased chances of a mutation occurring because there are more possibilities for error.
4) It is unusual for plants and animals to have an odd number of chromosomes in their nuclei. Explain how mosses can have odd numbers of chromosomes in their leaf cells.
Mosses can have odd numbers of chromosomes in their leaf cells because they have a haploid number of chromosomes.

DBQ on p. 134 – February 4, 2013
1) Outline five similarities between the life cycle of a moss and of a human.
Both involve bitosis, meiosis, and fertilization. Both also have eggs, sperm, and zygotes.
2) Distinguish between the life cycles of a moss and a human by giving five differences.
The human life cycle has a male and female but moss doesn’t. Human cycles are two cycles (female and male) that meet together but moss is just one cycle. Meiosis happens twice in the human cycle but only once in the moss cycle, and mitosis happens four times in the moss cycle but only twice in the human cycle. Moss plants have a haploid number of chromosomes whereas humans have a diploid number.

DBQ on p. 145 – January 30, 2013
1) There are many different chromosome numbers in the table, but some numbers are missing, for example, 5, 7, 11, 13. Explain why none of the species has 13 chromosomes.
None of the species have 13 chromosomes because in the body cells of most eukaryotes there are two chromosomes of each type.
2) Discuss, using the data in the table, the hypothesis that the more complex an organism is, the more chromosomes it has.
The data shown in the table seems to support this hypothesis up to a certain point because in general, larger mammals have more chromosomes than insects. It’s assumed that larger mammals are more complex than insects, so this makes sense.
However, there are exceptions because organisms that are thought to be the most intelligent (i.e. modern humans and chimpanzees) have fewer chromosomes than those that aren’t considered to be as intelligent (i.e. domestic sheep and goats).
3) Explain why the size of the genome of a species cannot be deduced from the number of chromosomes.
The number of chromosomes doesn’t reveal the size of the whole of the genetic information of an organism.
4) Suggest, using the data in Table 3, a change in chromosome structure that may have occurred during human evolution.
Humans may have lost some of their chromosomes.