c7.1 -- Evolution

Question 1

A student concluded that Fig. 9.2 shows that Lord Howe Island was originally colonised
by a species of plant that was a common ancestor for Howea, Laccospadix and
Linospadix. Explain whether or not this conclusion is correct. [2]

Answer 1

1. According to Fig. 9.2, the common ancestor for Howea, Laccospadix and
   Linospadix existed about 11.5 million years ago;
2. From the information given in the question, Lord Howe island was only formed 6.9
   million years ago and so there could not have been a species of plant that colonised Lord Howe island, that was a common ancestor of Howea, Laccospadix
   and Linospadix;

Question 2

With reference to Fig. 9.1, suggest how these two species of palm tree may have evolved
by sympatric speciation. [5]

Answer 2

1. An ancestral* palm grew on Lord Howe Island, an isolated island off the coast of
   Australia, that had two soil types in close proximity to each other - older volcanic soil
   and younger calcareous soils;
2. When the palms that normally grew on volcanic soil started to grow on calcareous soil,
   a flowering time difference arose as a physiological response to growing on a different
   soil type;
3. Thus physiological isolation* prevented interbreeding* and hence disrupted gene
   flow* between the two sub-populations of palms growing in the two types of soil
   although they were in close proximity;
4. This resulted in evolutionary changes occurring independently within each sub-
   population. i.e. different genetic changes from accumulation of mutations*, as well as

changes in allele frequencies through genetic drift* and natural selection* occurred
within each sub-population;
5. There existed variation in the two sub-populations and palms with favourable traits that
were better adapted had a selective advantage to the specific soil conditions and were
selected for, increasing frequency of favourable alleles and survived, reproduced and
passed on their alleles to the next generation;
6. Over hundreds and thousands of successive generations each sub-population
became genetically distinct, reproductively isolated* species, Howea forsteriana and
Howea belmoreana which are unable to interbreed* to form fertile, viable offspring;

Question 3

State the types of evidence that can be used to establish the phylogenetic relationships
between species. [3]

Answer 3

1. DNA, RNA (nucleotide) sequences and amino acids sequences;
2. of homologous genes;
3. or homologous anatomical structures can be used to establish phylogenetic
   relationships between species;
4. from fossils;

Question 4

Suggest how human activity may account for the changes shown in Fig. 11.1. [4]

Answer 4

1. Human activity such as (any one example) increase combustion of fossil fuels for
   electricity/industrial processes, such as in cement works/burning land and vegetation to
   clear land for agriculture etc releases greenhouse gases (GHG) like carbon dioxide and
   methane (any one example)
2. Increase Greenhouse gases (GHG) allow short-wave radiation from the sun to pass
   through to heat the Earth’s surface which radiate out-going long-wave radiation/infra
   red/heat which is absorbed and re-emitted by the GHGs back to the Earth’s surface;
3. This leads to increased trapping of radiation/heat resulting in warmer temperatures at
   higher altitudes
4. Resulting in the melting of glaciers at lower altitudes and more favourable (warmer)
   temperatures at higher altitudes for vegetation to grow.

Question 5

Outline how scientists could obtain and analyse the data needed to deduce Fig. 3.2.
[3]

Answer 5

1. Obtain fresh plant specimen from all the populations of the species and extract
   mitochondrial DNA.
   (FYI: Mitochondrial DNA has faster mutation rate compared to nuclear DNA and
   hence it is useful for comparing individuals within a species that are closely related.)
2. Obtain the DNA sequence of a homologous* gene on the mitochondrial DNA.
3. Quantify the number of differences in the nucleotides (of the gene) between the
   populations.
4. The more closely related the populations, the smaller the numerical genetic
   difference.

Question 6

(b) Suggest how the history of the Criollo population could account for the lower yield
compared to all of the other wild populations. [2]

Answer 6

1. Deliberately crossing genetically similar trees with better-tasting beans is a form
   of artificial selection.
2. Unmasking deleterious recessive alleles that are expressed in the homozygous
   condition results in reduced growth, whereas the wild populations remain
   genetically diverse and deleterious alleles remain hidden in the diploid state.

Question 7

(c) Suggest how knowledge of the genetic diversity and evolutionary history of T. cacao
could be useful in the future. [3]

Answer 7

1. Future challenges could be related to climate change with more extreme
   temperatures and flood or drought conditions.
2. For populations to survive better in extreme conditions, interbreed a population
   with one that is genetically different to introduce new alleles into the population
   that could result in favourable phenotypes
3. Knowledge of the mechanism and rate of evolutionary change of the different
   populations to climate change can allow prediction of adaptability of the
   population to future changes or improves mitigation strategies to protect the
   species.

Question 8

With reference to Fig. 9.1, explain why the Sumatran, Tapanuli and Bornean orangutans
are considered to be separate species. [2]

Answer 8

1. The Sumatran and Bornean orangutans have a larger difference in DNA
   characteristics for variable 2 compared to variable 1 while the Sumatran and Tapanuli
   orangutans have a larger difference in DNA characteristics for variable 1 compared
   to variable 2 and the Bornean and Tapanuli have a larger difference in DNA
   characteristics for both variables 1 and 2;
2. Due to the large differences in DNA characteristics, between all 3 species they are
   likely to have evolved from a common ancestor a very long time ago and accumulated
   many mutations over time and eventually formed different reproductively isolated*
   species that are unable to interbreed to form fertile, viable offspring;

Question 9

Explain how these three species of orangutan may have evolved from a common
ancestor. [3]

Answer 9

1. When sea levels rose at the end of the ice age when ice melted, the ancestors of the
   orangutans became geographically isolated* (A:a reproductive barrier formed).
   Thus the 3 sub-populations of orangutans were prevented from interbreeding and
   gene flow was disrupted*;
2. Different environments/niches presented different selection pressures* and so
   individuals with favourable traits and were best adapted had a selective advantage
   and were selected for;
3. and survived and reproduced and passed on their favourable alleles to their offspring
   which led to an increasing frequency of favourable alleles;
4. As the 3 different sub populations evolved independently of each other, their allele
   frequencies changed as they accumulated different genetic mutations, and were
   subjected to genetic drift and natural selection. Over a long period of time this
   led to reproductive isolation and formation of 3 distinct but closely related
   orangutan species (i.e. macroevolution occurred);

Question 10

Describe the advantages of using molecular methods to classify organisms. [3]

Answer 10

1. Nucleotide data are objective. Molecular character states are unambiguous as A, C,
   G and T are easily recognisable and cannot be confused;
2. Nucleotide data are quantitative. Molecular data are easily converted to numerical
   form and hence are amenable to mathematical and statistical analysis and hence
   computation. Degree of relatedness can be inferred and quantified by calculating
   nucleotide differences between species;
3. Nucleotide data can be used to compare species which are morphologically
   indistinguishable especially if they are very closely related;
4. As changes in nucleotide sequences accumulate over time with clockwork regularity.
   We can estimate the time of speciation of modern to ancient species;

Question 11

Explain how increases in temperature and rainfall could lead to an increase in the number
of cases of viral dengue disease. [2]

Answer 11

Increase in temperature
1. would lead to increased rate of enzyme catalysed reactions in the mosquito
vector Aedes aegypti;
2. leading to faster development rate and decreased length of reproductive cycles
and mosquito population increase and hence greater spread of viral dengue
disease;
Increase in rainfall
1. may lead to more pools of stagnant water ;
2. which female mosquitoes lay eggs in and for the larval and pupal stages of the
mosquito life cycle hence greater spread of viral dengue disease;

Question 12

Suggest and explain how laying an egg at a height of 1 mm above the ground affects
the rate of development of the egg compared to an egg laid at a height of 1 m above
the ground. [3]

Answer 12

1. At 1 mm above ground, the eggs would experience temperatures ranging from 33°C
   to 55°C during the day time. (15 +18 and 25 +30 to get the range);
2. At temperatures below the tolerance limit of the eggs at 45° C, the increase in
   temperature would lead to faster development of the eggs due to increase rate of
   enzyme reactions;
3. As temperatures increase between 45°C and 55°C there would be an increase in the
   risk of eggs dying since the maximum temperature is beyond the tolerance limit of
   the eggs at 45°C;

Question 13

The fossil record shows that over geological time evolution has occurred at different rates.
Describe, with examples, factors that may have influenced the rate of evolution
over geological time, before the appearance of humans. (do not attempt this question in an
exam if you can do Q4) [14]

Answer 13

The rate of evolution over geological time has indeed varied, and several factors can
influence the pace of evolutionary change. Before the appearance of humans, there were
several key factors that influenced the rate of evolution. Here are some examples:
1. Environmental Changes:
a) Climate Shifts: Changes in climate, such as ice ages or periods of
warming, have had a significant impact on the rate of evolution;
b) Organisms that can adapt to these new conditions may evolve rapidly to
survive, while those that cannot may face extinction eg woolly mammoth;
c) Geological Events: Geological events like volcanic eruptions, earthquakes,
and the formation of new landmasses/islands can alter habitats, leading to
selective pressures and driving the evolution of species adapted to these
changing environments;
d) eg. Lord Howe Island was a volcanic island formed off the coast of
Australia. The difference in soil condition – volcanic and calcareous soil
led to the sympatric speciation of the Howea palms ;

2. Predation and Competition:
   a) Interspecies Competition: Intense competition for resources, such as food,
   territory, or mates, can drive rapid evolution as species develop new
   adaptations to outcompete others.
   b) For example, the evolution of long necks in giraffes allowed them to access
   food sources that were out of reach for other herbivores;
   c) Coevolution with Predators: The presence of new predators can drive prey
   species to evolve defensive mechanisms.
   d) An example is the evolution of defensive structures in prey animals, like
   the spines on a porcupine;
3. Mass Extinction Events:
   a) Mass extinctions, such as the Permian-Triassic or Cretaceous-Paleogene
   events, have had profound effects on the rate of evolution. These events
   wiped out a significant portion of life on Earth, creating opportunities for
   survivors to rapidly diversify and fill vacant ecological niches;
   b) Mammals, for example, diversified rapidly through adaptive radiation after
   the extinction of non-avian dinosaurs;
4. Geographic Isolation:
   a) Geographic barriers like mountain ranges or oceans can separate
   populations of a species, leading to allopatric speciation. Geographically
   isolated populations may experience different selective pressures, which
   can result in the evolution of new species.
   b) The classic example is the finches in the Galápagos Islands which
   exhibited adaptive radiation;
   c) Geographical isolation can be due to continental drift eg primitive
   marsupials can be found mostly in Australia which was isolated early from
   the rest of the continents;
5. Genetic Mutations:
   a) The rate of genetic mutations can influence the rate of evolution. Increased
   mutation rates, due to factors like radiation or chemical exposure, can
   accelerate the appearance of new traits in populations.
   b) Some mutations may be beneficial eg antibiotic resistance of bacteria to
   fungal penicillin, while others can be detrimental;
6. Reproductive Strategies:
   a) Different reproductive strategies can influence the rate of evolution.
   Species with shorter generation times and higher reproductive rates, like
   insects eg mosquitoes, may evolve more rapidly than species with longer
   generation times, like elephants;
7. Adaptive Radiation:
   a) When a single ancestral species gives rise to multiple descendant species
   in a relatively short time, it’s known as adaptive radiation.
   b) This can occur when new ecological niches become available, as seen
   with the diversification of cichlid fish in African lakes;
8. AVP - Symbiosis:
   a) Symbiotic relationships, such as mutualism or parasitism, can drive
   coevolution between species;
   b) For example, the evolution of flowering plants and their pollinators, like
   bees, is tightly linked due to mutualistic interactions;

These factors, along with many others, have interacted throughout Earth’s history,
resulting in the diverse array of life we see today. The rate of evolution has not been
constant but has been influenced by a complex interplay of these and other factors over
geological time.
Note: Examples given should be those before the appearance of humans.
QWC: At least 3 factors and 2 examples given

Question 14

Discuss, with examples, how a wide range of different human activities, including
science and technology, can affect the evolution of organisms. [11]

Answer 14

Directional selection of Peppered moth (Biston betularia)
1. Prior to the industrial revolution, the majority of peppered moths had light-colored
wings, which provided camouflage against light-colored lichen covered bark of trees;
2. As industrialization darkened tree trunks due to soot and pollution, darker moths had
a selective advantage and were selected for;
3. They survived and reproduced and hence the favourable allele coding for dark colour
increased in frequency and the population shifted towards darker forms;
4. This is an example of natural selection in response to human-induced environmental
changes;
Artificial selection of domesticated animals/plants
5. Humans have selectively bred domesticated animals and plants for specific traits for
many years;
6. For instance, the transformation of wild mustard into various Brassica crops such as
broccoli, cauliflower, and cabbage over thousands of years is a result of artificial
selection;
7. Similarly, dog breeding has led to the development of hundreds of diverse dog breeds
with specialized characteristics, from herding to hunting;
Antibiotic resistant bacteria
8. The overuse and misuse of antibiotics in healthcare and agriculture;

9. has led to the evolution of antibiotic-resistant bacteria (such as MRSA:Methicillin-
   resistant Staphylococcus aureus)
10. as bacteria with random genetic mutations* that provide resistance to antibiotics will
    be selected for in the presence of antibiotics and will survive and reproduce and will
    increase in numbers;
11. while susceptible strains are eliminated.
    Insecticide-resistant insects
12. Genetically-engineered crop plants such as Bt-corn express Bt-toxin, a bio-
    insecticide, that in harmful to insects (as they kill them by creating pores in their mid-
    gut membrane) but not humans;
13. The extensive planting of Bt-crops and the overuse of Bt-insecticides has led to Bt-
    resistant insect species being selected for, surviving and reproducing and increasing

in numbers;
14. An example is the diamondback moth which is a crop pest with resistance to Bt-toxin;
Herbicide resistant crops
15. The creation of genetically-engineered herbicide-resistant crops, such as Roundup
Ready soybeans;
16. Has led to the evolution of herbicide-resistant weeds;
17. When herbicides are sprayed to kill weeds that grow around Roundup ready soybean
plants, weeds that are resistant to the herbicide will be selected for, survive and
reproduce and increase in numbers leading to the formation herbicide-resistant weed
populations.
Chemical mutagens and ionising radiation
18. Chemical mutagens and ionizing radiation can cause mutations in the DNA of plants
and increase their genetic diversity;
19. For example, exposure to chemical mutagens like ethyl methane sulfonate (EMS)
can induce mutations in plants such as rice (Oryza sativa L.), resulting in novel traits
that can be selected for in breeding programs;
20. Ionizing radiation, like X-rays, has been used in the development of new crop
varieties, of rice, wheat, barley, cotton etc;
Marker can accept other examples for each category and allocate marks accordingly.
QWC: Examples given from at least 3 different categories.

Question 15

Describe the advantages of using genome sequences to reconstruct a phylogeny for
Scalesia on the Galapagos Islands. [3]

Answer 15

1. Nucleotide data are objective. Molecular character states are unambiguous as A, C, G
   and T are easily recognisable and cannot be confused;
2. Nucleotide data are quantitative. Molecular data are easily converted to numerical form
   and are amenable to mathematical and statistical analysis and hence computation.
   Degree of relatedness can be inferred and quantified by calculating nucleotide
   differences between species;
3. Nucleotide data can be used to compare species which are morphologically
   indistinguishable especially if they are very closely related like the finches;
4. As changes in nucleotide sequences accumulate over time with clockwork regularity.
   We can estimate time of speciation and place speciation events on a timescale above;

Question 16

Explain what can be learnt by comparing genomes of different species of fish such as
seahorses and zebrafish. [3]

Answer 16

1. Evaluating molecular homologies based on DNA of cytochrome c gene (any

example) can determine degree of nucleotide similarity;
2. The more related they are, the greater similarity there is in the sequence of their
homologous gene/DNA allowing the determination of ancestor-descendant
relationships;
3. Understand the link between genotype and phenotype;
4. Reveal structure of genetic variation between different populations of the individual
species;

Question 17

With reference to Fig. 9.1, suggest and explain how changes in the diversity of flowering
plants and changes in the diversity of mammals have affected the diversification of
beetles.[3]

Answer 17

1. As the diversity of flowering plants increased steeply from 135 million years ago
   (mya) to 75 mya, this created new niches for habitats e.g and food types for
   herbivorous mammals, leading to an increase/ rapid diversification of mammals;
2. This led to the increase in diversification of beetles at the same time period from 100 mya to 5 mya, shown by the increase in branches in phylogenetic tree, as there is increase in variety plants available as food for herbivorous mammals to diversify and occupy new niches;
3. With the increase in mammals, the dung of herbivorous mammals available as food for dung beetles led to the
   rapid diversification of dung beetles

Question 18

Describe the biological, ecological and morphological concepts of a species.[6]

Answer 18

1. Biological: A species is a group of organisms capable of interbreeding and producing
   fertile, viable offspring;
2. Members of the same species are reproductively isolated from other species;
3. They share a common gene pool and have the same chromosome number;
4. and usually have similar morphological, physiological and behavioural features;
   (note: pts 1and 2 are more important)
5. Ecological: A species is a group of organisms sharing the same ecological niche* within its native environment, focusing on unique adaptations to particular roles in a biological communitu.
6. The differences between species are due to the differences in the ecological
   resources that they depend on. This means that if a species can no longer occupy
   a particular niche, it would be considered a new species;
7. Morphological: A species is a group of organisms sharing similar body shape, size
   and other structural features;
8. definition can be applied to all organisms (i.e. sexually and asexually reproducing
   organisms);

Question 19

Using Fig. 10.1, Fig. 10.2 and Fig. 10.3, describe and explain the predicted effect of global
warming on the relative fitness of insects in temperate and tropical regions.[3]

Answer 19

1. Increase in temperatures due to global warming in tropical regions 20°S and 20°N of
   equator will decrease relative fitness of tropical insects from 0.0 to -0.1;
2. as they have small thermal safety margins* as their environments are already close to
   their physiological optimum and so they will approach their physiological optimum
   temperature faster and risk extinction;
3. Increase in temperatures due to global warming in temperate regions 20°S to 60 °S of
   the equator and 20°N to 60°N of equator will increase relative fitness of temperate insects
   from 0.0 to +0.12 and 0.0 to +0.09 respectively,
4. as they have larger thermal safety margins* as their environments are on average
   cooler than their physiological optimal, and thus have broader thermal tolerance;
   Note: The difference between an organism’s thermal optimum and its current climate
   temperature is known as the thermal safety margin.
   For insect species, thermal safety margins increase sharply with latitude.

Question 20

Define biological classification and explain how classification relates to phylogeny.[3]

Answer 20

1. Biological classification groups organisms based on overall morphological similarities and
   usually does not consider their evolutionary history;
2. It uses a naming system where each organism is given a binomial name* and grouped
   into a domain, kingdom, phylum, class, order, family, genus and species in a hierarchical
   manner;
3. Phylogeny also groups organisms but they are grouped based on their evolutionary history
   / ancestor-descendent relationships using molecular data and;
4. It does not rank organisms but instead assigns each organism a position on a
   phylogenetic tree* based on its evolutionary relationship with other organisms on the
   tree;

Question 21

Explain why knowledge of mutation rates is useful in reconstructing phylogenies.[2]

Answer 21

1. Rate of mutation/time taken for mutation to accumulate in virus types is constant;
2. from the number of nucleotide differences between different virus strains, it is
   possible to distinguish between different virus strains /infer evolutionary
   relationships/degree of genetic divergence between different virus strains
   or
   infer common ancestor of virus strains;
3. from the number of nucleotide differences, it is possible to infer the time when a
   certain strain virus emerged or share common ancestor;
   Reject time of speciation because viruses are not able to form new species.
   A: if not specifically reference to virus

Question 22

Use the data in Table 3.1 to evaluate whether or not the changes in coral cover in
these two areas of the Great Barrier Reef from 1985 to 2012 can be attributed to
global climate change.[4]

Answer 22

Decrease can be attributed to climate change because
1. Coral bleaching is a result of increase in sea water temperatures which cause
zooxanthellae to be expelled from corals, eventually leading to death of coral;
2. Mean percentage decrease due to coral bleaching was 0.36% and 0.04% in
area 1 and area 2 respectively;
3. Tropical storms are more severe due to increased temperatures from climate
change;
4. Mean percentage decrease due to tropical storms 1.05% and 1.75% in area 1
and area 2 respectively;
Decrease should not be attributed to climate change because
1. There were only 2 sites studied, both in the Great Barrier Reef;
2. Changes may be due to localised environmental conditions and not global
climate change;
3. Data is represented as a mean value over 27 years, so unable to see changes
on a yearly basis to make an informed conclusion;

Question 23

define biological evolution

Answer 23

descent with modification through the
mechanism of natural selection and refers to the cumulative
changes that occur in a population from generation to
generation over time.
* This leads to differences in populations and explains the origin of
all the organisms that exist today or have ever existed.
* It encompasses both microevolution and macroevolution.

Question 24

define microevoLUTIOn

Answer 24

changes in allele or genotype frequencies that occur within a gene pool of a population of a particular species over generations.

Evolution is thus a change in the genetic makeup of populations over generations

Question 25

define macroevolution

Answer 25

large-scale evolutionary events over geological times. Macroevolution results in phenotypic changes in populations that are significant enough to warrant their placement in taxonomic groups at species level and higher. It involves the descent of different species from shared ancestors over many generations. * Macroevolution is an evolutionary event seen zoomed back, the overall pattern; the origin of species and higher-level taxa, such as families or classes, are the concerns of macroevolution. It is also a long-term view, attending to such phenomena as the rise, diversification, and demise of dinosaurs; the origin of birds; and the appearance of mammals.

Question 26

essential features of Darwin-wallace's theory

Answer 26

Obv1: organisms have great reproductive ability Obv2: environmental restrictions/ constancy in numbers Inference 1: struggle for existence Obv 3: variation in structure and behaviour within the population Inference 2: survival of the fittest by natural selection Obv 4: differential reproduction (like produce like) evolutIOn of population -(only if there is genetic or reproductive isolation)-> formation of new species

Question 27

define population genetics

Answer 27

the study of the genetic composition and variability of a population. * It is concerned with - the frequency and distribution of alleles/genes in a population and the evolutionary forces that act on it, and - the genotypes in natural populations and factors that determine them.

Question 28

define population

Answer 28

It is a group of individuals of the same species that live in a defined geographic area. Note that a species is the smallest unit of the classification system (see Section 3.2). * The individuals of a population are capable of interbreeding (free to reproduce with any other individual) and producing fertile offspring. * This group of individuals is considered as belonging to a sexually reproducing species, in which the individuals share a common gene pool. Random mating occurs in the population and therefore genes of individuals are free to mix within the gene pool. * Thus, a population is the smallest unit that can evolve.

Question 29

define gene pool

Answer 29

total collection of all genes (ie all the alleles at all gene loci) of all breeding individuals in a population at any one time - is dynamic - each population has a gene pool

Question 30

allele and genotype frequency definition

Answer 30

allele frequency: The relative proportion of the alleles of a gene present in a population. genotype frequency: The relative proportion of a particular genotype present in a population.

Question 31

5 conditions for non-evolving populations

Answer 31

1. large population 2. random mating occurs 3. no gene flow 4. no mutations occur 5. no natural selection occurs

Question 32

causes of microevoLUTIOn

Answer 32

any factor that results in change in allele frequencies in a gene pool to violate the hairy-weinberg equilibrium. - natural selection - genetic drift - gene flow

Question 33

sources of genetic variation

Answer 33

1. random mutations to generate new alleles -> source of new alleles that are new heritable variations for selection pressures to act on; can change allele frequency in gene pool of a population and mutation rates are rare and slow. 2. crossing over (at prophase I of meiosis) and independent assortment of homologous chromosomes (at metaphase I) during meiosis 3. sexual reproduction which involves fertilisation of gametes

Question 34

define natural selection

Answer 34

the process by which certain individuals that are better adapted to an environment survive to reproduce, i.e. differential survival and reproduction. There is thus reproductive success of fitter individuals over those that are less fit. It increases the frequency of favourable genotypes / alleles in the gene pool, and the resultant population becomes adapted to its particular environment.

Question 35

define genetic drift

Answer 35

The random change of allele and genotype frequencies, as a result of chance alone, can differ from generation to generation in a small gene pool / population.

Question 36

define gene flow

Answer 36

Gene flow is the movement of genes / alleles from one population to another. This may be achieved by the migration of fertile individuals from one population to another and breeding in that new population.

Question 37

define speciation

Answer 37

Speciation: the evolution / origin of species. Evolution occurs whenever the inherited characteristics of a population or of a species change over a period of time. When these changes lead to the formation of one or more new species, speciation has taken place.

Question 38

define allopatric speciation

Answer 38

formation of new species when one population becomes geographically separated from the rest of the species and subsequently evolves by natural selection and / or genetic drift.

Question 39

define sympatric speciation

Answer 39

a new species evolves within the same geographic region as the parental species OR geographically overlapping population(s).

Question 40

define biological classification

Answer 40

Biological classification is the act of systematically arranging organisms into groups based on particular shared characteristics (mainly morphology) and their similarities. It may not take into consideration evolutionary relationship between species.

Question 41

define taxon / taxonomy

Answer 41

A taxon (plural: taxa) is a formal grouping of organisms at any given level, such as species, genus, or phylum.

Question 42

define character

Answer 42

A character is any structural, chromosomal, or molecular feature that distinguishes one group from another.

Question 43

define macroevolution

Answer 43

It is the large-scale phenotypic changes in populations that generally warrant their placement in taxonomic groups at the species level or higher.

Question 44

define biodiversity

Answer 44

It is the variety of living organisms (i.e. distinct biological species) and their range of behavioural, ecological, physiological and other adaptations in an area such as an ecosystem.

Question 45

define systematics

Answer 45

It is a discipline of biology involves the scientific study of the diversity of organisms, focusing on classifying organisms and determining their evolutionary relationships. Systematics connects classification with evolutionary history.

Question 46

define biological classification

Answer 46

It is the act of systematically arranging organisms into groups based on particular shared characteristics (mainly morphology) and their similarities. * Classification may not take into consideration evolutionary relationship between species.

Question 47

define phylogeny (LO!!!)

Answer 47

It is the organization of species according to particular characteristics which takes into consideration the evolutionary relationship between species.

Question 48

define homology

Answer 48

Homology refers to the presence, in two or more species, of a structure derived from a recent common ancestor (shared ancestry).

Question 49

define analogy

Answer 49

Analogy refers to a characteristic that superficially appears homologous, but is actually independently acquired. This is a form of convergent evolution whereby similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages. analogus structures: homoplasies

Question 50

state the environmental factor most imps in determining changes in the frequency of different beak sizes [1]

Answer 50

aVAILABILITY of food (eg seeds) -- contextualise to question Weather

Question 51

state the process that resulted in the change in frequency of diff beak sizes [1]

Answer 51

natural selection. R: directional selection because this is not a process, its describing the result of natural selection

Question 52

suggest an explanation for the distribution of variation shown by the shape of these curves [3]

Answer 52

1. ref to normal circumstances following a long period of wet weather, small soft seeds are produced in large quantities, finches with medium beak size, are selected for, while selecting against small and large beaks fiinches 2. following long period of drought, larger and harder seeds are available, finches with medium to small beak sizes are selected for, while selecting against finches with small beaks 3. both curves exhibit normal distribution however after drought population size of medium beaked finches decreases, and mean beak size shifts towards the right/ increases from medium to large/ exhibit directional selection

Question 53

suggest why finches with large beaks are more successful at eating large seeds than finches with small beaks [2]

Answer 53

1. beaks are stronger, can crush the seeds more successfully than the birds with smaller bills 2. large beaks, can grip the larger seeds 3. large seeds cannot fit into small beaks

Question 54

outline what is meant by stabilising selection [1]

Answer 54

ref to a form of natural selection, which selects for the intermediate phenotype and selects against the extreme phenotypes. R: genotype!!!

Question 55

state one condition under which stabilising selection occurs [1]

Answer 55

1. in an unchanging environment 2. where competition is not severe

Question 56

with ref to fig, explain how the production of cyanide depends on the genotypes of the clover plants [3]

Answer 56

1. at least 1 dominant allele for both genes 1 and 2 is necessary for the production of cyanide 2. ref to acyanogenic plant will be missing at least one dominant allele at either gene 1 or 2 any one from: 3. production of both enzymes 1 and 2 are required to complete the biochemical/ biosynthesis pathway (for cyanide production) 4. lack of production of either one or both enzymes will cause biochemical pathway for cyanide production to be incomplete 5. ref to recessive alleles at either gene locus is epistatic to the other locus Recall: gene interaction -> epistasis

Question 57

suggest how the cell membranes will be damaged by low tempt [2]

Answer 57

1. proteins embedded in the cell membrane are inactivated by the low tempt thus can no longer function 2. phospholipid bilayer reduced fluidity, becomes tightly packed 3. formation of ice crystals inside the cells -> rupture membrane structure

Question 58

with ref to figure, explain how the diff proportions of cyanogenic plants may have evolved in populations found in diff parts of Europe [1]

Answer 58

1. as tempt rose from -9.0dgC to 8.0dgC, proportion of cyanogenic plants increased, most plants being acyanogenic below 0dgC, and most being cyanogenic above 4.4dgC 2. tempt is the selection pressure, causing cyanogenic plant cells to freeze below 0dgC, releasing cyanide, damaging the plants metabolism, thus acyanogenic plants are selected for 3. slugs exert selection pressure at higher tempts above 4.4dgC, cyanide production kills/deters slugs hence cyanogenic plants are selected for

Question 59

with ref to figure, explain why the large ground finch, medium ground finch and small ground finch are considered to be 3 separate species. [3]

Answer 59

1. idea of morphological species concept, where the 3 species of finches have significantly different beak lengths and body masses 2. idea of ecological species concept where the finches live on different islands with different food sources, developing diverse feeding habits and diets/ unique ecological niches 3. use of relevant data from fig to show difference in beak length/ body mass between at least 2 species, eg small ground finch has beak length between 16-19mm, while large ground finch has beak length between 36-40mm 4. idea of biological species concept, finches are reproductively isolated, sufficient reproductive isolating mechanisms, adaptations and genetic diversity to be 3 different species

Question 60

discuss how its shown that microevolution and macroevolution have contributed to the evolution of Darwin's finches. [4]

Answer 60

change in allele frequency in a population over time Microevolution: 1. colonisation of different islands that presented different selection pressures, with different food sources available 2. ref to natural selection, some individuals survive better on different food sources, reproduce more successfully, increasing the allele and genotype frequencies in the gene pool of the finch population over time 3. ref to contribution by microevolution where small-scale evolutionary changes are observed in a specific finch population, with more individuals better adapted with suitable beak length and body mass Note that: individuals selected for, survive, reproduce, pass down their genes to the next generation; NOT GENES SELECTED FOR!! Macroevolution: any 2 from 1. ref to rise in sea levels over past...formation of islands...where islands [] were formerly in one large land mass of Santa Fe. 2. ref to creation of ecological opportunities/ adaptive zones, with diverse food sources available on the different islands 3. ref to contribution by macroevolution through possible extinction of some species of finches through rise in sea levels, creating unoccupied adaptive zones, hence surviving species of finches are presented with new ecological opportunities. 4. ref to contribution by macroevolution through adaptive radiation of the Galapagos finches where 14 species of finches evolved from an ancestral finch species, after formation of Galapagos islands 5.ref to evolutionary novelties through morphological innovation, where finches evolved with different beak lengths, rapidly diversifying from a common ancestor

Question 61

describe the advantages of using genome sequences [molecular evidence] in reconstructing phylogenetic rls [3]

Answer 61

1. genome sequence variation, have a clear genetic basis that's easy to interpret 2. finches possess nucleic acids, molecular data can be collected for comparison 3. molecular evidence, unambiguous and objective 4. genome sequences are precise, accurate, quantifiable, facilitates objective assessment of evolutionary rls 5. certain molecular traits in common, offering valid basis for comparison among all organisms 6. ref to fig 9.3, quota data Formula: (memorise) 1. objective and unambiguous 2. quantitative and open to statistical analyses to determine degree of relatedness between organisms

Question 62

describe briefly why these 4 ectomorphs have diff adaptations [3]

Answer 62

1. ref natural selection 2. diff selection pressures from the diff habitats they occupy 3. ref to selection for favourable adaptations 4. ref to change in allele frequency note phrasing: gene cannot be selected for. individuals are selected for.

Question 63

explain how data provided evidence for allopatric speciation [2]

Answer 63

1. ref to geographical isolation, different islands having different species) 2. ref to disruption of gene flow

Question 64

explain how data provide evidence for sympatric speciation

Answer 64

1. ref to new species evolves within same geographical region 2. ref to 4 different ecomorphs: canopy/ twig, resulting in large toepads/ short legs respectively

Question 65

outline how the evolution of lizards differs between the 2 islands [3]

Answer 65

1. ref to genetic drift/ founder effect, random change of allele frequencies as a result of chance alone 2. ref to smaller gene pool on the smaller islands 3. ref to less genetic variation amongst lizards in smaller islands 4. AVP, islands could have unique climatic conditions wipe out -> extinction