A panspermia / cosmozoan / extra-terrestrial origin of life 1
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| 1. (a) panspermia / cosmozoan / extra-terrestrial origin of life 1
(b) all (12) amino acids present in both samples; the levels of five of the amino acids are the same / both possess equal quantities of glycine/alanine/norvaline/isovaline/aspartic acid / etc.; meteorite contains less sarcosine/N-ethylglycine/-amino-N-butyric acid; meteorite contains more valine/proline/-aminoisobutyric acid/ pipecolic acid pipecolic acid is lowest in both samples / glycine and alanine highest in both; 3 max (c) inter-stellar material / the Earth's reducing atmosphere could have been a source of the first organic molecules; the Murchison meteorite could approximate the chemistry of the pre-biotic Earth / lends support to the Miller experiment / the processes in the experiment replicates those in nature; somewhere in outer space conditions may resemble pre-biotic Earth / a reducing atmosphere; 1 max [5] 2. RNA self-replicates RNA self-replication has been shown experimentally; RNA thought to have served as first genes not DNA; because DNA RNA protein mechanism too complicated to evolve all at once; it can act as an enzyme / called a ribozyme / RNA has catalytic properties; (recently discovered that) RNA can catalyze formation of more RNA (e.g. rRNA / tRNA / mRNA); RNA can bind amino acids for formation of peptide linkages; and form enzymes to help RNA replicate; RNA can also be transcribed into DNA (using reverse transcriptase); [6] 3. D [1] 4. (a) some families have become extinct; 1 (b) Lipotidae; 1 (c) (mitochondrial) DNA;
(d) river dolphins did not evolve from the same ancestor; river dolphins evolved in similar environments; river dolphins were exposed to the same selection pressures; river dolphins adapted in the same ways; river dolphins show convergent evolution; 3 max (e) radioisotopes in the rocks where the fossils are found / in fossils; (absolute) dates are obtained by radioisotopic dating of rocks where fossil toothed whales are found; comparisons of molecular sequences / DNA / proteins; (absolute) dates can be estimated from differences due to mutations in living toothed whales / molecular sequences; position of fossils in the rocks; (relative) dates may be obtained by comparing the positions of the fossil toothed whales relative to one another; 2 max [8] 5. gene/genetic mutations; chromosome mutations; recombination during meiosis / crossing over during prophase I; random alignment of homologues during meiosis/metaphase I / independent assortment; random mating in the population / random fertilization; environmental changes; Do not give a mark for mutation alone. "Random" must be qualified for mating or fertilization. [3] 6. (a) order Primate, family Hominidae 1 (b) genetic evolution is dependent on/controlled by genes; cultural evolution is learned/taught / language dependent; genetic evolution is limited by the genetic composition/genotypes of the populations; e.g. of human genetic evolution (such as increase in cranial capacity); cultural evolution allows much more rapid evolution; e.g. of human cultural evolution (such as tool making); 4 max [5] 7. Must include both for full marks. transient polymorphism: e.g. industrial melanism / peppered moths / any valid example; selection of different alleles depends on environmental changes / selection pressures / temporary presence of certain genotypes; balanced polymorphism: e.g. sickle cell anemia / any valid example; heterozygous advantage in malaria as more fit / heterozygotes maintained in a population due to adaptive value; [4] 8. (a) Award [1] for the comparison of both groups. the Polypodium (species) are (completely) isolated in different parts of the continent and the Pleopeltis (species) much closer together / physically overlapping / share same habitats; Polypodium grows in more northerly / temperate locations; 1 max (b) (i) Polypodium as it has lower similarity/genetic identity values / Pleopeltis has higher similarity/genetic identity values; 1 Reason required to achieve [1]. (ii) Pl. polylepis and Pl. conzattii; 1 (c) geographic / ecological isolation / isolated by distance / by glacial periods / climatic changes; reproductive or genetic separation of gene pools (led to speciation) / adaptive radiation; 1 max (d) Award [1] for Polypodium and [1] for a reason. Polypodium; as more genetic difference between all three species than between the species of Pleopeltis; takes time to accumulate mutations / genetic changes; distance may have facilitated the process of reproduction isolation; 2 max [6] |