Selection And Evolution Flashcards

Question

Describe antibiotic resistance

Answer 1

*When antibiotics are no longer effective against bacteria *Antibiotic variation are no longer effective against bacteria E.g. penicillin inhibits cross link formation between peptidoglycans in bacteria cell wall Many bacteria, have penicilinase enzymes which can break down penicillin Become resistant to penicillin Caused by: 1. Spontaneous/random mutation in some bacteria *Mutation cause change in protein/ production of new protein that can be targeted by antibiotics Natural selection enables resistance genes to spread 2. Antibiotic is the selection pressure *Bacteria with allele coding for penicillinase has selective advantage *Antibiotics only kill bacteria that are non-resistant 3. Resistant bacteria more likely to survive and reproduce *More likely to pass down allele to offspring via binary fission 4. Overtime, resistance allele frequency increases

Answer 2

Peppered moth Spends the day resting on tree barks/branches/trunks Camouflage to protect itself against its predators (birds) Before 1849 moths with a speckled appearance was most common No. of moths with a melanin/black appearance increased in industrial areas BUT other places speckled form still more common ➡️Natural selection caused change in allele frequencies 1. Variation present *Black moths and speckled moths 2. Selection pressure= predation by birds *Industrial cities tree barks has a darker shade due to high pollutants *Black moths have a selective adaptation as they were more camouflaged *White moths are selected against 3. Black moths more likely to survive and reproduce *More likely to pass down allele to offspring 4. Overtime , allele for black colour increased in frequency in industrial cities

Answer 3

Selection pressure= SCA and malaria 3 genotypes: 1. HsHs: homozygous for sickle cell alleles *RBC cannot carry oxygen very well, may die from SCA *SCA selects against HsHs 2. HNHN: Homozygous for normal Hb allele *No SCA *Plasmodium parasite affects RBC *Malaria is lethal, so more likely to die from malaria *Malaria selects against HNHN 3. HNHS: Heterozygous for sickle cell anaemia and malaria *Have sickle cell trait *Do not die from SCA *Less likely to suffer severe effects of malaria *Contains less plasmodium in their blood *Has selective advantage *More likely to survive and reproduce *More likely to pass on HN and Hs *Sickle cell alleles is maintained within population because of sickle cell trait individuals

Answer 4

Used to calculate allele, genotype and phenotype frequencies in populations. 5 requirements of the principle: 1. The population is large 2. There is random mating within a population 3. No immigration and no emigration 4. No mutations 5. No selection pressure against one phenotype If frequencies in real life are not as expected, this m bay mean that one of the assumptions above does not apply

Answer 5

Equation 1-For alleles p+q=1 P=frequency of dominant allele (A) q=Frequency of recessive allele (a) 1= all alleles in a gene pool Equation 2- for genotypes p^2 + 2pq + q^2=1 P^2= Homozygous dominant (AA) 2pq= Heterozygous (Aa) q^2=heterozygous recessive (aa)

Answer 6

1.Natural selection 2. Genetic drift *Founder effect *Bottleneck effect 3.Artificial selection

Answer 7

*Random process due to chance, unlike natural selection →Changes in allele frequencies fluctuate due to random events →Cannot be predicted *Affects small populations more than large populations →Higher chance that allele will be lost from population *Random events usually cause small effects only *Unless....there is: 1. Migration →Founder effect 2. Natural disaster →Bottleneck effect

Answer 8

*Due to migration *Few individuals move to a new region →Become geographically isolated from the larger population *New population is established by a small number of individuals →Only carry a fraction of the alleles of the original population →Gene pool may not be representative of gene pool of original population →Lower genetic diversity than original population *Over time, population may become genetically distinct from the original population →May develop into separate species=speciation

Answer 9

*Large decrease in genetic diversity →Due to large decrease in population numbers →Common when natural disasters occur →But can occur due to overhunting/human activities too! *Small group of survivors →Gene pool will not be representative of gene pool of original population →Limited gene pool compared to previous population p/s: Conservation effort may increase population number BUT does not increase genetic diversity Low genetic diversity=suscpetible to disease/enviromental changes

Answer 10

*AKA selective breeding *Induviduals with desired features are selected to breed →By humans *Selection pressure=humans 1. Humans choose parents with desirable features 2. Parents with desired features are crossed 3. Select offspring with desirable features 4. Repeat for many generations →Increase in allele frequency for ideal charcteristics →Decrease in frequency of undesired characteristics

Answer 11

*Artificial selection can result in inbreeding!! →Increase in homozygosity →Harmful recessive alleles may be expressed →Inbreeding depression/loss of hybrid vigour →Limited gene pool/decrease in genetic variation *Offspring may show desired traits, but may not be well-adapted to its enviroment

Answer 12

AF: Humans are the selection pressure NS: Environmental selection pressure AF: Selected feature for human benefit NS:Selected feature of organisms benefit AF: Not for survival/evolution NS:Promotes survival/evolution AF: Inbreeding common NS: Outbreeding common AF: Genetic diversity lowered NS: Genetic diversity remains high AF: Results in inbreeding depression NS: Increases hybrid vigour AF: Increased homozygosity/decreased heterozygosity NS: Increased heterozygosity/decreased homozygosity AF: No isolation mechanism operating NS: Isolation mechanism operating AF: Usually faster NS:Usually slower

Answer 13

a)Improving the milk yield od dairy cattle b)Disease resistance in varieties of wheat and rice c)The incorporation of mutant alleles for gibberellin synthesis into dwarf species d)Inbreeding and hybridisation of maize

Answer 14

Desired traits: *Increased docility/calm temperament *Fast growth rates (for meat production) *High milk yield *Fat-rich milk *High fertility *Disease resistance *Breed individuals by collecting sperm from bull →Can freeze and use later →Artificial inseminating defrosted semen into cow during its fertile period →Can avoid inbreeding by referring to pedigree records

Answer 15

Wheat, triticum aestivum *Resistance to fungal infections *E.g. wheat rust Rice, oryza sativa *resistance to bacterial and fungal diseases *E.g. bacteria blight, "spots", "smuts" and rice blast Other desired traits in crop improvement: *High yield...so bigger ears/more grains per ear/bigger grains *Fast grow rates *Tolerance to high temperature *Pest-resistance *Gluten-rich grain for bread flour

Answer 16

Desired trait: Shorter stem, dwarf varieties in wheat →Greater porportion of energy put into grain instead of height=higher yield →Less susceptible to being knocked over by weather →less straw produced *Giberellin (GA) stimulate stem elongation →Incorporate mutant alleles for gibberellin synthesis into wheat by crossing shorter plants →Mutant alleles are of the Rht (reduced height) gene →Mutant alleles code for faulty enzymes in GA synthesis pathway →Inhibit gibberellin synthesis →Della protein nor broken down and continues to bind to transcription factor PIF →Inhibit transcription of growth genes →Dwarf variety

Answer 17

Maize, Zea mays *Problem:inbreeding leads to uniformity *Homozygous plants are less vigorous than heterozygous ones *Inbreeding caused plants of each gen to progressively becomes smaller and weaker (inbreeding depression) *Outbreeding produces heterozygous plants that are healthier, grow taller and have high yields *BUT problem! there will be no uniformity-hard to harvest and sell Solution: Inbreeding and hybridisation! 1. Companies use inbreeding to produce homozygous maize plants of desired traits for many generations →E.g. more kernels/big kernels/ high yield etc. 2. Cross-pollinate two inbred lines=hybridisation →Produce F1 seeds 3. farmers buy seeds and plant them →F1 plants are all hybrids/heterozygotes *All have the same genotype *Uniform! *Has hybrid vigour

Answer 18

Molecular evidence for evolution is found in: 1. Amino acid sequences of protein *Compare amino acid sequence of 2 species *The more similar the amino 2. Mitochondrial DNA (mtDNA)

Answer 19

*Compare amino acid sequence of 2 species *The more similar the amino acid sequence, the more closely related the species *More similar amino acid sequence=less time has elapsed since the most recent common ancestor. For example: Cytochrome c *Electron carrier in the ETC *Important proteins like these are highly conserved \ *Length and amino acid sequence for the protein are identical in rat and in mouse *But human cytochrome c has 9 amino acids that are diff →Mouse and rat share a more recent common ancestor →Human is more distantly related

Answer 20

*Compare nucleotide sequence in mtDNA of 2 species *There are less differences in nucleotide sequence, the more closely related the species *Few mutations=less time elapsed since the most common ancestor Characteristics of mtDNA: 1. mtDNA is circular, does not undergo crossing over 2. Mutations occur at a constant rate →Can act as a "molecular clock" 3. mtDNA mutates faster than nuclear DNA →Changes only arise by mutation and are not repaired →Not associated with histones →Oxidative phosphorylation can produces reactive oxygen species that can acts as mutagens 4. Smaller, has fewer genes →mtRNA analysis is quicker 5. mtDNA is passed from mother to offspring →All descendants of one female have identical mtDNA

Answer 21

Species: Group of similar organisms with the same *Morphological, *Physiological *Behavioural *Biochemical features *Which can interbreed to produce fertile offspring *i.e. NOT reproductively isolated from each other *members of one species are reproductively isolated from another species

Answer 22

*Formation of new species *Speciation involves a reproductive barrier between populations. Two types of speciation: 1. Allopatric speciation *Caused by geographical isolation 2. Sympatric speciation *Same location

Answer 23

*Speciation that occurs as a result of geographical barrier of same species 1. Geographical barrier E.g. river, mountain, sea *2 populations of same species physically separated *No breeding between populations= gene flow *Barrier prevents interbreeding between populations = populations reproductively isolated 2. Different selection pressures act on separated populations *Isolated population subjected to different environmental conditions *Individuals with beneficial alleles are selected for ➡️ More likely to survive and reproduce more ➡️ Pass on beneficial alleles to offspring ➡️ Change in allele frequency/ gene pool *Different mutations occur giving rise to new alleles *Genetic drift occurs randomly in separate populations 3. Over a long time/ many generations… *Population have sufficient differences *Populations are unable to interbreed to produce fertile offspring = reproductively isolated ➡️New species

Answer 24

*Same location, no physical isolation 1. Different features/behaviour (or other isolating mechanisms) ➡️Cause a population to not interbreed ➡️This is a barrier to gene flow 2. Over time… *Change in allele frequency due to genetic drift ➡️Cause populations to become reproductively isolated ➡️Cannot breed as they are now different species

Answer 25

E.g. Polyploidy in plants *Polyploid plants= has more than two sets of chromosomes ➡️Result of complete non-disjunction in meiosis ➡️Chromosomes fail to segregate to opposite poles ➡️Result in gametes with extra/ missing chromosome *Non disjunction= chromosomes fail to segregate to opposite poles ➡️Can cause an individual to have extra/missing chromosomes ➡️Cause diseases like Down syndrome, Triple X chromosome etc Complete non-disjunction= all identical chromosomes fail to segregate to opposite poles ➡️Result in diploid gametes ➡️ If fertilised (2n+n), can result in trisomy (3n) *In general, fusion of two mutated gametes result in ➡️New individuals with different chromosome number as parents ➡️Cannot interbreed with original parent species ➡️New species

Answer 26

*In past, mass extinction events were all natural *E.g. due to severe changes to climate and physical conditions *There were 5 previous mass extinction events *Humans may cause a 6th mass extinction event! *The international union for conservation of nature (IUCN) is the world’s largest global environment organisation *The IUCN red list of threatened species valuates the conservation status of plants and animals species. Some endangered species are high profile, others less photogenic or not enough publicity. Extinction is largely due to: *increased competition from a better adapted species *Habitat loss (Draining of wetlands, cutting down rainforests, pollution of air, water and soil) *Hunting/killing/poaching for sport or food or medicine *Climate change

Answer 27

* Smaller population are less resilient than larger populations *Populations with reduced genetic diversity face increased risk of extinction