Ana səhifə

A panspermia / cosmozoan / extra-terrestrial origin of life 1

Yüklə 29.5 Kb.
ölçüsü29.5 Kb.
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

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);

3. D

4. (a) some families have become extinct; 1

(b) Lipotidae; 1

(c) (mitochondrial) DNA;
amino acid sequences / proteins; 1 max

(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

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.

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

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;

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.

as more genetic difference between all three species than between the species of
takes time to accumulate mutations / genetic changes;
distance may have facilitated the process of reproduction isolation; 2 max


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2016
rəhbərliyinə müraciət