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Flashcards in Evolution Deck (67)

A collection of four animal specimens is observed and a dichotomous key is applied. Which specimen is an arthropod?

1. Non-segmented body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . go to 2 Segmented body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . go to 3 2. Body is not symmetrical . . . . . . . . . . . . . . . . . . . . . . . . .  specimen A Body is symmetrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   specimen B 3. Jointed appendages present . . . . . . . . . . . . . . . . . . . . . specimen C Jointed appendages absent . . . . . . . . . . . . . . . . . . . . . . . .specimen D

A. Specimen A

B. Specimen B

C. Specimen C

D. Specimen D

C. Specimen C


Which of the following represent homologous features?

A. Wings in birds and insects

B. The appendix in humans and horses

C. Fins in fish and wings in birds

D. The striped coat of the zebra and the tiger 

 B. The appendix in humans and horses


What is the mechanism of natural selection?

A. Any individuals in a population can be selected entirely by chance.

B. After a change in the environment a species will evolve adaptations to the new conditions.

C. If an adaptation to the environment is useful, an individual will develop it and pass it on to its offspring.

D. Variations amongst individuals of a population are selected by a changing environment.

 D. Variations amongst individuals of a population are selected by a changing environment.


Which of the organisms A–D, identified by the key below, represents an Annelid?

1. Shows bilateral symmetry                       go to 2

Does not show bilateral symmetry            Cnidaria

2. Has a segmented body                           go to 3

Does not have a segmented body             go to 4

3. Has jointed legs                                        A

   Does not have jointed legs                       B

4. Has a shell                                                 C

 Does not have a shell                                   D



To which group do sponges belong?

A. Cnidaria

B. Filicinophyta

C. Porifera

D. Mollusca

C. Porifera


Which process tends to reduce variety within a population?

A. Natural selection

B. Random fertilization

C. Independent assortment

D. Crossing over

A. Natural Selection


Describe how natural selection leads to evolution. [6]

populations produce more offspring than can survive; individuals show variation; limited resources; create a struggle for survival/competition; survival of the fittest / some are better suited to the environment and survive; variation/characteristic must be heritable; best fitted individuals survive to reproduce; advantageous variation/characteristic/allele passed on; over time advantageous variation/characteristic/allele increases in the population; [


What is evolution?
A.    A measure of the relative survival and reproductive success of an individual
B.    A cumulative change in the genetically controlled characteristics of a population
C.    A physical change during an organism’s life that is inherited by its offspring
D.    A random change in the proportions of alleles from generation to generation 

B.    A cumulative change in the genetically controlled characteristics of a population


Explain how natural selection can lead to evolution using antibiotic resistance in bacteria as an example.

members of a population of the same species show variation;
some organisms are more likely to survive due to selective
advantage / survival of the fittest;
some organisms have a reproductive advantage;
these variations may be genetically controlled/heritable;
these genes are most likely to be passed on to offspring;
this can change the characteristic of the population;
bacteria can normally be killed with antibiotics;
antibiotics impose a selection pressure;
if a few bacteria have natural resistance to the antibiotic
they will survive;
if the resistance is heritable they will pass it on to their offspring;
they will reproduce/evolve to form bacterial colonies resistant
to the antibiotic;
example of organism selected by use of antibiotic;
(e.g. MRSA bacteria / resistant TB bacteria)


There are many animals living on Earth today that belong to the same phylum as the trilobites, but there are no living trilobites. Deduce, with a reason, the phylum to which Triarthus belonged.

jointed legs/limbs/appendages/(hard) exoskeleton;


Outline the evidence for evolution provided by fossils.

fossils show changes over time (in organisms);
fossilized organisms are different from existing ones;
(yet) share features with existing organisms / homologous structures;
suggest common ancestry;
show intermediate stages in evolution of groups / missing link fossils;


Some trilobites swam in clear, shallow water and had very large eyes. Suggest how species with large eyes could evolve from species with smaller eyes.

natural selection;
over time/generations;
range/variation in size of eye (in the trilobite population);
individuals with larger eyes are more likely to survive;
example of selective advantage of large eyes e.g. can see predators /
find food;
surviving individuals reproduce and pass on their genes/large eyes
to offspring;


Define the term clade.

a group of related organisms sharing a common ancestor / a
group of organisms containing an ancestor and all of its


Distinguish between analogous and homologous structures, giving an example of each.

homologous structures evolved from a common ancestor while
analogous structures did not;
example of homologous and example of analogous; (both needed)    2
    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


Distinguish between transient polymorphism and balanced polymorphism.

transient when one allele gradually replaces another /
directional selection;
balanced when allele frequencies do not change / no/stabilizing


State an example of transient polymorphism.

e.g. gradual increase in darker peppered moths due to
environmental change/industrial melanism


Describe an example of a barrier between gene pools.

name of type of barrier;
description;    2
    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.



Outline how variations in DNA can indicate phylogeny.

variation due to random mutations / count numbers of difference
in base sequence;
can be used as evolutionary clock / estimate time since divergence/
amount of variation indicates how closely species are related/linked;
differences can indicate ancestry/sequence in which groups diverged;


Which of the following are used as evidence for evolution?
I.    Homologous structures
II.    Selective breeding of domesticated animals
III.    Overproduction of offspring
A.    I and II only
B.    I and III only
C.    II and III only
D.    I, II and III

A.    I and II only


Compare convergent and divergent evolution.

oth explain similar structures in different organisms;
Convergent evolution

different ancestor

converge to produce similar solutions/analogous structures

e.g.wings in insects and birds

species appearance becomes more similar over time

unrelated species look similar but are genetically different
Divergent evolution
common ancestor;

diverge to suit different functions/homologous structures;

e.g.vertebrate limb structure;

species appearance becomes more different over time;

species look different but are closely related genetically;


Outline the process of adaptive radiation.


varied members of a single species occupy a variety of niches / migration
of a species to an area with a variety of niches;
natural selection/selection pressure will be different in various niches
causing adaptation of groups to the varied niches;
results in many species from one ancestral species;
reproductive isolation enhances adaptive radiation;
adaptive radiation results in speciation;


There has been a change of thinking; moving from gradualism to punctuated equilibrium demonstrates the changing nature of science. Discuss these two ideas about the pace of evolution.

in gradualism evolution occurs at a constant pace;
fossil records of gradual change with intermediate forms support
this theory;
evolution of modern horse/another suitable example seems to
support this view;
in punctuated equilibrium evolution proceeds rapidly for short
periods of time intermittent with long periods of little change/stability;
gaps in the fossil record/lack of intermediate forms support the idea of
punctuated equilibrium;
strata in the fossil record with appearance of many new species following
a mass extinction supports the idea of punctuated equilibrium;


Outline the evidence provided by DNA for the common ancestry of living organisms.

all living organisms use DNA as genetic/hereditary material;
genetic code is (almost) universal;
idea that mutations accumulate gradually in DNA;


The cladogram below shows the classification of species A to D. Deduce how similar species A is to species B, C and D.


A is most similar to B;
A is equally similar to C and D;
A is least similar to both C and D;


Suggest two reasons for using cladograms for the classification of organisms.

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


Outline ideas about the pace of evolution according to gradualism and punctuated equilibrium.

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;


Which of the following will promote variation in a species?
I.    Meiosis
II.    Fertilization
III.    Natural selection
A.    I only
B.    II only
C.    I and II only
D.    I, II and III


C.    I and II only


Why has antibiotic resistance evolved in bacteria?
A.    All bacteria reproduce very quickly.
B.    Bacteria exposed to antibiotics developed a resistance to them.
C.    Varieties of bacteria resistant to antibiotics reproduce faster than non-resistant varieties.
D.    Bacteria showing resistance to antibiotics survive after antibiotics are used.

D.    Bacteria showing resistance to antibiotics survive after antibiotics are used.


Explain how punctuated equilibrium affects the pace of evolution.


periods of stability/little evolution/stasis, followed by periods of sudden
major change/lot of evolution/rapid speciation;
in periods of stability organisms become well-adapted to environment;
natural selection acts to maintain characteristics;
equilibrium punctuated by rapid environmental change;
such as volcanic eruption / meteor impact / change in sea level;
directional selection leads to rapid evolution;


Describe transient polymorphism.


two alleles in a gene pool/polymorphic;
one allele gradually replacing another;
due to strong selection pressure;
example; (e.g. melanic moths/industrial melanism)


Define the terms allele frequency and gene pool.
Allele frequency: ........................................................................................................
Gene pool: ...................................................................................................................


allele frequency: measurement of how often an allele appears (i.e. A or a);
gene pool: total sum of all the genetic information available for reproduction
    within the population;



State one assumption made when the Hardy–Weinberg equation is used.


large population;
random mating;
no migration / immigration / emigration;
no mutations;
no natural selection;


Outline how variations in specific molecules can lead to phylogeny.

phylogeny is the evolutionary line of descent;
the greater the differences, the longer the time span since the two species
had a common ancestor;
variation can be due to mutations;
mutations are chance events so caution must be taken when interpreting


Outline the value of classifying organisms.

organization of data helps to identify organisms;
suggests evolutionary links;
suggests the closeness of a relationship the more similar the
characteristics are;
allows prediction of characteristics shared by members of a group;


Define the term gene pool.

all the genes in an (interbreeding) population


Compare allopatric speciation and sympatric speciation.

both involve the formation of new species;
by the isolation of its genetic pool (in both cases);
both provide conditions for natural selection;
sympatric in same geographical area, allopatric in different;
sympatric could be reproductive/behavioural isolation while allopatric
physical isolation;
example of each; (e.g. allopatric speciation of Galapagos finches and
sympatric speciation due to polyploidy)



What is the mechanism of natural selection?
A.    Any individuals in a population can be selected entirely by chance.
B.    After a change in the environment a species will evolve adaptations to the new conditions.
C.    If an adaptation to the environment is useful, an individual will develop it and pass it on to its offspring.
D.    Variations amongst individuals of a population are selected by a changing environment.


D.    Variations amongst individuals of a population are selected by a changing environment.



Outline allopatric and sympatric speciation.

speciation is the formation of a new species by the splitting of an
existing species;
allopatric speciation caused by geographical separation;
sympatric speciation occurring within the same habitat caused
by different niches / caused by courtship/feeding differences/
behavioural differences;
both processes lead to isolation of sub-populations;
isolation favours certain genetic variations (within a species);
over time this leads to genetic barriers/speciation;



Outline the pace of evolution as implied in the theory of punctuated equilibrium.


long stable periods / little change;
short periods of sudden/rapid evolution;
e.g. volcanic evolution/meteor impact causing sudden climatic/
environmental changes / other valid examples;


Using examples, distinguish between analogous characteristics and homologous characteristics.

analogous: [2 max]
similar structures but different (evolutionary) origins / different basic
structure but same function;
e.g. vertebrate and invertebrate eyes / insect and human legs;
Accept any other valid example.
    homologous: [2 max]
structures are of similar origin / same basic structure but different functions;
e.g. pentadactyl limbs in vertebrates;
Accept any other valid example.


Albinism, a lack of pigmentation in skin and hair, is caused by a recessive allele.
Albinism occurs in North America in approximately one in 20 000 persons. Explain how the Hardy-Weinberg equation is applied in this example.


    predicts frequencies of dominant and recessive alleles of a given gene;
homozygous for each allele and heterozygous;
frequency of dominant allele = p, recessive/albino allele = q;
total frequency of both alleles = 1 or p + q = 1;
random mating, probability of receiving two dominant alleles is p × p or p2;
probability of receiving two recessive alleles is q ×q or q2;
expected frequency of heterozygous genotype is 2pq;
p2 + 2pq + q2 = 1;
assumes no mutations / large population / random mating / no selective
pressure / no immigration nor emigration;
explains why recessive alleles do not disappear over several generations;
q2 =   or q = 0.007 (frequency of recessive);
p = 1 – 0.007 or 0.993;
frequency of dominant p2 = 0.986 or 98.6%;
frequency of heterozygotes 2pq = 0.014 or 1.4%;
Accept values with more significant figures.


Charles Darwin used domesticated animals to provide evidence for evolution by natural selection.
What is this evidence?
A.    Differences between breeds show that selection can cause species to change.
B.    The ancestors of domesticated animals can be found in the fossil record.
C.    Some domesticated animals die because the environment cannot support them all.
D.    Variation in domesticated animals is due to sexual reproduction.


A.    Differences between breeds show that selection can cause species to change.


Compare sympatric speciation and allopatric speciation.


both involve reproductive isolation / separation of gene pools;
sympatric is speciation due to isolation of populations living in the
same geographic area whereas allopatric is speciation due to
geographic isolation;


State one species in the genus Australopithecus.
(ii)    For this species, state the geographical distribution and approximately how many years ago it lived.


e.g. A. afarensis / A. africanus / A. garhi
Award [0] if species name has a capital letter.    1
(ii)    Award [1] for a value within date range and [1] for
geographic distribution.
date range
geographic distribution
A. afarensis
3.9 to 2.9 mya;
eastern Africa;
A. africanus
2 to 3 mya;
southern Africa;
A. garhi
2 to 3 mya;
eastern Africa;


Discuss the concept of punctuated equilibrium.

long periods of stability;
environmental change / sudden change;
leads to rapid speciation/evolution;
helps to explain absence of intermediate forms;
competing theory is gradualism;


Define analogous characteristics using one example to illustrate your answer.


analogous structure similar in appearance/function but with different
evolutionary history e.g. wing of bat and wing of bird;


Which process has the greatest effect in determining which members of a population are most likely to survive until reproductive age?
A.    Evolution
B.    Natural selection
C.    Meiosis
D.    Hybridization


B.    Natural selection


Outline the evidence for evolution provided by homologous structures.

comparative anatomy of groups of animals or plants shows certain
structural features are basically similar;
homologous structures are those that are similar in shape in different types
of organisms;
structural similarities imply a common ancestry;
(homologous structures) used in different ways;
    example is pentadactyl limb in vertebrates / modification of ovary wall or
pericarp to aid seed dispersal / other suitable example;
    adapted to different mode of locomotion in particular environment / 
example of two differences such as bat’s wing and human hand;
illustrates adaptive radiation since basic plan adapted to different niches;
the more exclusive the shared homologies the closer two organisms are related;
certain homologous structures in some species with no apparent function such as
human appendix (homologous with functional appendix in herbivores);


Define sympatric speciation.


the formation of new species by populations that inhabit the same or
overlapping geographic regions


Describe two examples of barriers between gene pools.


a population colonizes a new habitat that involves unique selection
pressures / becomes geographically isolated;
eg Darwin’s finches;
eg some variants of wheat;


Discuss gradualism and punctuated equilibrium.


gradualism: slow, continuous change over a long period of time;
gradual accumulation of (neutral) mutations / variations;
punctuated equilibrium: long periods of stability followed by sudden changes;
fossil record supports this;
natural selection can be intense and can cause rapid change / evolution;
rapid evolution due to major environmental changes / volcanic eruptions / 
meteor impact / other example;
only advantageous alleles ultimately survive;
some mutations had no morphological effects so not visible in the fossil record;
rate of evolution could have fluctuated over time;    


Explain how natural selection leads to evolution.

parents produce more offspring than required to keep numbers constant;
more are produced than the environment can support;
example of an environmental condition;
these offspring show variation;
some are better adapted than others to the environment;
these tend to survive to breed themselves;
characteristics are inheritable;
so the new generation has these characters too;
this leads to changes in the population as a whole;
these changes constitute evolution;


Two different trees have been classified as Pinus pinea and Pinus nigra. Which of the following statements is correct?
A.    Both trees belong to the same class but a different genus.
B.    Both trees belong to the same family and same genus.
C.    The species name of both trees is Pinus.
D.    The family names are pinea and nigra.


B.    Both trees belong to the same family and same genus.


A poodle and a chihuahua are both dogs and classified as Canis familiaris. What conclusion can be made?
A.    They belong to the same genus but not the same species.
B.    They are the same species but not the same genus.
C.    They are different species but can interbreed.
D.    They belong to the same genus and are the same species.


D.    They belong to the same genus and are the same species.


Which phylum does the plant below belong to?

A.    Angiospermophyta
B.    Bryophyta
C.    Coniferophyta
D.    Filicinophyta


D.    Filicinophyta



Plants are a diverse group of eukaryotic organisms. Describe the different characteristics of the bryophyta, filicinophyta, coniferophyta and angiospermophyta.

At least one characteristic from each group is needed for maximum
bryophyta have no roots / only have rhizoids;
bryophyta have simple leaves/stems / only a thallus;
bryophyta produce spores in capsule;
byrophyta are nonvascular;
bryophyte exhibit (pronounced) alternation of generations / a
significant gametophyte generation;
    filicinophyta have roots, stems and leaves;
filicinophyta (often) have divided/pinnate leaves;
filicinophyta produce spores in sporangia/spores on the undersides of leaves;
filicinophyta exhibit alternation of generations;
filicinophyta have primitive vascular tissue / no true xylem and phloem;
    coniferophyta have woody stems;
coniferophyta (often) have narrow leaves/needles/scales;
coniferophyta produce seeds in cones/unenclosed seeds;
    angiospermophyta have flowers;
angiospermophyta have ovules in ovaries;
angiospermophyta produce seeds (with hard coats) in fruits;    


Explain how sexual reproduction can eventually lead to evolution in offspring.

offspring vary in traits;
variation results from sexual reproduction;
independent assortment of alleles (during meiosis of spermatogenesis/
oogenesis) contributes to variation;
meiosis is the cellular process that produces gametes;
crossing over (during meiosis) increases variation;
fertilization (combination of different genomes) contributes to variation;
more offspring may be produced than the environment can hold;
struggle for existence can occur;
offspring whose traits best adapt them to environment will survive/survival
of fittest;
change in environment will lead to survivors with new/different traits;
correct use of term natural selection/selective pressure;
variation is heritable / over time more offspring born with new trait;
change in gene pool;
when entire population (of a species) exhibits new trait, evolution
has occurred;    


Using simple external recognition features, distinguish between the plant phyla bryophyta and angiospermophyta.


nonvascular/unspecialized tissue/no veins

small/height up to 7 cm

exist as organized masses of cells / “leafy” appearance

reproductive structures / capsules appear on stalks

microscopic spores

sometimes hair-like extensions below growing surface/rhizoids

vascular/specialized tissue/veins;

tall/ height up to 100 m;

contain water-conducting cells (tissue)/food-conducting tissue/support tissue;

have flowers;

covered seeds/fruits;



An animal has radial symmetry, a sac-like body with only one opening and tentacles with stinging structures. To which phylum does this animal belong?
A.    Annelida
B.    Cnidaria
C.    Mollusca
D.    Porifera


B.    Cnidaria


Which of the following is a characteristic of platyhelminthes?
A.    Many pairs of legs
B.    Flat body
C.    Hard exoskeleton
D.    Presence of cnidocytes


B.    Flat body


What features distinguish Platyhelminthes from Annelida?


Platyhelminthes don't have segmented bodies while Annelida's do


hich taxa do Zerynthia rumina and Zerynthia polyxena share?
A.    They share the same class but not the same family.
B.    They share the same species but not the same class.
C.    They share the same class but not the same genus.
D.    They share the same family but not the same species.


D.    They share the same family but not the same species.


Ants, bees and wasps are classified in the same order. What can be deduced about these animals?
A.    They are classified in the same class.
B.    They are classified in different phyla.
C.    They are classified in the same family.
D.    They are classified in different kingdoms.


A.    They are classified in the same class.


Pseudolarix amabilis produces seeds but not flowers. Physcomitrella patens has leaves but not roots.
To which groups do they belong?


Pseudolarix amabilis are coniferophyta while Physcomitrella patens are bryophyta


In the hierarchy of taxa, what is in a family?
A.    A group of classes
B.    A group of genera
C.    A group of orders
D.    A group of phyla


B.    A group of genera


Identify which phyla of plants fit each of the brief descriptions below.
(i)    Evergreen woody plant; leaves are shaped like needles; seed-producing with reproductive structures in cones.
Phylum:    ....................................................................................................
(ii)    Underground stem that bears roots and leaves called fronds; spores develop in spore cases called sporangia located on the underside of fronds.
Phylum:    ....................................................................................................


coniferophyta    1
(ii)    filicinophyta


Which phylum does an animal belong to, if it has stinging tentacles and a mouth, but no anus?
A.    Annelida
B.    Cnidaria
C.    Porifera
D.    Platyhelminthes


B.    Cnidaria

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