1. A
study was undertaken of the evolution of two species of wasps, one the parasite of the other. The parasite
queen, Vespula squamosa, kills the host queen, Vespula maculifrons, and takes over her role in the colony. Data
was compiled for 13 colonies
of V. squamosa and 37 colonies
of V. maculifrons to analyse the
genetic structure of the two
species.
Each point on the graphs
represents the genetic distance
and geographic distance
between a pair of colonies. The
genetic distance indicates the
number of differences in
specific DNA markers between
a pair of colonies. The results
are shown below.
(a) i. Determine the greatest
genetic distance between any
pair of colonies of V.
squamosa. [1]
(a) ii. Identify the
greatest
geographic distance between
any pair of colonies of
V. maculifrons. [1]
(b) Describe the relationship between the geographic distance and genetic distance in the two species. [1}
(c) Compare the two species in terms of genetic distance between the pairs of colonies. [2]
(d) Data
collected on eight specific alleles in the two species indicated that each species was in Hardy–Weinberg
equilibrium. Evaluate all the data regarding possible evolutionary changes within the two species. [2]
2. Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution [6].
3. (a) i. Distinguish between transient polymorphism and balanced polymorphism. [2]
(a) ii. State an example of transient polymorphism [1]
(b) Describe an example of a barrier between gene pools. [2]
(c) Outline how variations in DNA can indicate phylogeny. [2]
4. (a) Define the term clade. [1]
(b) Suggest two reasons for using cladograms for the classification of organisms. [2]
(c) Distinguish between analogous and homologous structures, giving an example of each. [2]
(d) The table below lists five animals along with four morphological characteristics. A plus sign (+) indicates
that the animal has this
characteristic while a minus
sign (-) indicates that the
characteristic is absent.
Based on the features, a
student constructed a
cladogram. State the names of
the organisms missing in the
following cladogram. [2]
(e) Describe the major anatomical features that define humans as primates. [2]
3. Discuss the endosymbiotic theory for the origin of eukaryotes. [6]
Markscheme:
1.
2. few
hominid fossils have been found/not often found/are very rare;
most hominids/organisms not preserved/decompose;
only teeth and bones remain / soft tissues do not fossilize;
require certain conditions for preservation/dry/anaerobic/quickly covered/frozen; earlier cultures did not bury
the dead / remains were scavenged/dispersed;
acids break down/dissolve teeth/bones;
many missing links/fossils of intermediate stages;
difficult to get conclusive evidence / difficult to falsify theories; theories change radically with one/few
discoveries;
3. (a) i. transient
when one allele gradually replaces another / directional selection; balanced when allele
frequencies do not change / no/stabilizing selection;
(ii) e.g. gradual increase in darker peppered moths due to environmental change/ industrial melanism
Accept any other valid example.
(b) name of type of barrier; description;
e.g. behavioural isolation;
different courtship behaviour so no mating between two populations;
Accept only the first type of barrier in the answer. Accept geographical separation, hybrid infertility, difference
in chromosome number or breeding time.
(c) variation due to random mutations / count numbers of difference in base sequence;
can be used as evolutionary clock / estimate time since divergence/separation;
amount of variation indicates how closely species are related/linked;
differences can indicate ancestry/sequence in which groups diverged;
4. (a) a group of
related organisms sharing a common ancestor / a group of organisms containing an ancestor and
all of its descendants / OWTTE
(b) methods used to prepare cladograms use a different approach from traditional classification/taxonomy;
show ancestral relationships;
reflect how recently two groups shared a common ancestry;
cladograms are (objective/accurate because they are usually) based on molecular differences;
they should be considered as a good complement to traditional classification;
(c) homologous structures evolved from a common ancestor while analogous structures did not;
example of homologous and example of analogous; (both needed)
e.g. an example of homologous is pentadactyl limb in mammals and birds / mouth parts in house fly and
mosquito/other valid example and an example of analogous is eye in vertebrates and squid/octopus / wings of
insect and bat / jointed legs of vertebrates and insects/other valid example
(d)
(e) opposable
thumbs (enable grabbing);
flat fingernails (instead of claws/for scratching); forward-facing eyes for stereoscopic vision;
rotatable shoulder joints (for tree-climbing adaptation);
skull modified for upright posture;
large brain to body/skull ratio enables higher levels of thinking;
3. 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;