1.
(a)
(b)
(c)
simple molecules must polymerize/assemble into polymers;
origin of self-replicating molecules / formation of self-replicating
molecules;
simple molecules must become isolated from the surroundings/enclosed
in membranes;
2 max
in water as organic reactions are aqueous;
warm conditions/pools near geothermal vents/volcanic pools
allow high reaction rates;
evaporation of water allows organic (precursor) molecules to
become more concentrated;
high temperatures not desirable as organic molecules become
unstable;
clay minerals/metal ions may act as catalysts / clay forms a
matrix for monomers to attach;
2 max
early atmosphere was oxygen free;
some prokaryotes could carry out chemosynthesis;
cyanobacteria (and other varieties) developed the ability to
photosynthesize;
used water as hydrogen source so released oxygen;
oxygen began to accumulate in the atmosphere;
more photosynthesis than respiration;
2 max
[6]
2.
eukaryotes evolved from prokaryotes;
mitochondria/chloroplasts evolved from (independent) prokaryotic cells;
taken in by larger (heterotrophic) cell by endocytosis;
theory supported by characteristics of chloroplasts/mitochondria;
[2 max] for mitochondria/chloroplast characteristics:
mitochondria/chloroplasts have naked DNA;
mitochondria/chloroplasts divide/carry out fission;
mitochondria/chloroplasts have 70S ribosomes / synthezise own proteins;
mitochondria/chloroplasts have double membranes;
cristae similar to mesosomes / thylakoid have similar structures in prokaryotes;
but theory cannot be falsified as it predicts something occurring in the past;
theory does not explain the origins of cilia/flagella/linear chromosomes/meiosis;
weaker evidence that cilia/flagella evolved from attached bacteria/spirochetes;
6 max
[6]
3.
(a)
the non-living synthesis of simple organic molecules/amino acids from
inorganic molecules;
the assembly of these molecules into polymers/polypeptides;
(b)
the origin of self-replicating molecules that made inheritance possible;
the packaging of these molecules into membranes with an internal
chemistry different from their surroundings;
2 max
self-replicating and catalytic activities of RNA;
short sequences of RNA have been able to duplicate/copy other RNA
molecules accurately;
RNA enzyme/ribozyme (able to synthesize other molecules);
3-dimensional structure of ribosome catalytic sites (for peptide formation)
are composed of RNA;
able to store information in sequence of (4) nucleotides (similar to DNA);
2 max
[4]
4.
(a)
(b)
(c)
synthesis of simple organic molecules/nucleotides/amino acids;
assembly of these molecules into polymers/DNA/protein;
origin of self-regulating molecules that made inheritance possible;
packaging of molecules into membranes (with internal chemistry
different from surroundings);
gradualism is the slow change from one form to another / stable conditions
lead to low levels of natural selection making it a long, gradual process;
punctuated equilibrium implies long periods without much change and
short periods of fast changes / mass extinction promotes rapid
change/new species;
(i)
(ii)
a group including an ancestral species and all the descendents from
that species / a group of organisms that evolved from a
common ancestor
2 max
2
1
all four organisms have vertebrae;
shark is the oldest/furthest from human/other examples
of relationships between the four organisms;
human only one with all four characteristics;
appearance of legs separated others from shark;
appearance of mammary glands, separated kangaroo and human from
bullfrog;
appearance of placenta, separated human from kangaroo;
both kangaroo and human are mammals;
3 max
[8]
5.
(a)
11
1
(b)
Ile and Glu (both needed to award the mark)
1
(c)
(d)
(e)
share 17 (out of 29) amino acids in common / more amino acids
similar than different;
both have Mn in the enzyme (as cofactor);
greatest difference between them is from amino acid 18 to 22;
mitochondrial has Gly (position 12) while E. coli (Mn) never has Gly;
Leu is most common amino acid in both appearing four times / other
valid comparison;
2 max
divergent (evolution) as the cytoplasmic dismutase shows a greater
number of differences (than the other three enzymes);
divergent as convergent (evolution) implies existence of analogous
structures and there are none here;
1 max
endosymbiotic theory states bacteria were engulfed by organisms to
become mitochondria;
sequence comparison between mitochondrial and bacterial dismutase
supports this hypothesis;
more similarity in the amino acid sequence between mitochondrial
and bacterial dismutase than between mitochondrial and cytoplasmic
dismutase;
2 max
[7]
6.
(a)
(b)
non-living synthesis of simple organic molecules;
from mixture of any three of methane, ammonia, water vapour
and hydrogen;
assembly of these organic molecules into polymers;
the origin of self-replicating molecules that made inheritance possible;
the packaging of these molecules into membranes with an internal
chemistry different from their surroundings;
binary fission of cell;
3 max
endosymbiosis theory states that eukaryotes are formed from prokaryotes;
symbiosis is an association between two or more species;
mitochondria of eukaryotes evolved from aerobic bacteria;
chloroplasts evolved from primitive autotrophic prokaryotes;
taken into larger heterotrophic cells by endocytosis;
eukaryotes formed membranes that could contain the prokaryotes;
mitochondria/chloroplasts have DNA/RNA similar to prokaryotes;
mitochondria/chloroplasts have double membrane;
3 max
[6]
7.
(a)
RNA can replicate;
can act as a catalyst;
can code for information;
2 max
(b)
simulated conditions of pre-biotic earth (in closed container);
water vapour;
mixture of ammonia, methane, hydrogen / reducing atmosphere;
sparks/electric (discharge to simulate lightning);
condenser / cooling of mixture;
obtained amino acids;
3 max
[5]
8.
(a)
(b)
non-living synthesis of simple organic molecules;
assembly of (simple organic) molecules into polymers;
origin of self-replicating molecules that made inheritance possible;
packaging of molecules into membranes with an internal chemistry
different from their surroundings;
1 max
initial atmosphere contained no free oxygen / anaerobic bacteria perhaps
the first organisms on Earth;
some prokaryotes were chloroplast-like/photosynthetic/cyanobacteria;
oxygen is by-product of photosynthesis/oxygen produced by
photolysis of water;
2 max
[3]
9.
(a)
(b)
(under the hypothesized conditions) on the pre-biotic Earth, simple
organic molecules could have been created
smaller/70S ribosomes in mitochondria/chloroplasts (as in prokaryotes);
circular DNA in mitochondria/chloroplasts (as in prokaryotes);
mitochondria/chloroplasts have double membrane;
similar size/shape of mitochondria/chloroplasts to prokaryotes;
1
2 max
[3]
10.
(a)
(b)
autocatalytic / can function as an enzyme;
can function as genetic material;
can (self)replicate;
2 max
Award [1] for any two of the following:
CH4 / H2 / NH3 / H2O
1 max
Accept symbol, chemical formulae or words.
(c)
describes the origin of eukaryotic cells;
endosymbionts live within larger host cells;
eukaryotic cells contain mitochondria and / or chloroplasts;
mitochondria and chloroplasts have evolved from independent free living
organisms (bacteria);
these organisms were taken into a larger heterotrophic cell by endocytosis;
not digested but cells were kept alive and continued to carry out aerobic
respiration and photosynthesis;
4 max
[7]