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Flashcards in Evolution Deck (67)
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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)

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