genetic diversity and adaptation

Question 1

what determines the phenotype of an organism

Answer 1

sequences of bases on the DNA code - determines proteins made in cells - ultimately determines the characteristics

Question 2

what is a gene pool

Answer 2

total amount of inherited info in a species
all the alleles of all the genes in a pop

Question 3

what are alleles

Answer 3

different forms of the same gene

Question 4

what is genetic diversity

Answer 4

total no. of alleles in a population

therefore greater number of alleles means more genetic diversity and variation

Question 5

why is genetic diversity important

Answer 5

long-term survival of a species
greater the genetic diversity in a species the wider range of characteristics in the pop
so some will have advantageous characteristics
and allows natural selection to therefore occur and survive + reproduce

Question 6

what happens in species with low genetic diversity

Answer 6

death

Question 7

what happens in species with high genetic diversity

Answer 7

some mem of species survive as are adapted

Question 8

what factors increase genetic diversity

Answer 8

-mutation
mutation= change in base sequence on DNA so results in new alleles created - protein could be altered
-meiosis- reshuffle alleles present in gene pool - cross over event and IA generate huge amounts of variation

Question 9

what factors decrease genetic diversity

Answer 9

-selective breeding
-genetic bottleneck
-founder effect
-random genetic drift

Question 10

what is selective breeding

Answer 10

humans artificially choosing organisms with desirable/favourable characteristics and using them as breeding stock

eg crops
high yield,better taste, better colour, increased tolerance to enviro conditions

animals
increased body size,increased product, improved temperament, too look a certain way

Question 11

how does selective breeding reduce genetic diveristy

Answer 11

inbreeding over many generations
results in inability to adapt to sudden enviro conditions

Question 12

what are genetic bottlenecks

Answer 12

event takes place in which either a significant % of pop is killed or significant % of pop is prevented from reproducing
small pop = small no. of alleles and small gene pool
eg environmental change or hunting/human intervention

Question 13

an example of a genetic bottleneck

Answer 13

cheetahs
-severe climate change eg ice age - large no. killed so only few cheetahs to breed so less alleles in pop
-human hunting hunt to extinction so less alleles as inbreed

Question 14

what is the founder effect

Answer 14

population founded from a small no. of individuals then those individuals will carry a small range of alleles and pop that develops from them will have limited genetic diversity
often result of geography
results in speciation

Question 15

what is natural selection

Answer 15

process which acts upon populations so that those organism with the best features survive and breed#

eg advantageous characteristic increases reproductive success and disadvantageous limits

Question 16

what are the 3 types of adaption

Answer 16

anatomical
physiological
behavioural

Question 17

what is the process of natural selection

Answer 17

-all species produce more offspring than are needed to replace themselves and maintain the population at a constant level - OVERPRODUCTION
-individual members of the same species and their offspring are different from one and other - VARIATION DUE TO MUTATION
-in a population there will be limited resources and there will be COMPETITION between individuals for survival - food,water,space,mate etc
-some individuals will be better suited to the environment than others- ADAPTATION so more likely to survive
-indviduals that survive are more likely to breed and pass on their alleles - DIFFERENTIAL REPRODUCTIVE SUCCESS
-over time species will change as the environment changes -adavtangageous alleles increase in frequency and disadvan decrease- CHANGE IN ALLELE FREQUENCY

Question 18

what are selective pressures

Answer 18

factors of the habitat which act on individuals
-competition -limited resources so individuals can compete with each other - better competitors more likely to survive
-predation- prey adapted to avoid predator and predator adapted to catch prey
-disease - kill organisms or result in them being debilitated so less able to compete-organism with genotypes resistant to disease will be able to survive ad pass on genotype

Question 19

what are the 3 types of selection

Answer 19

-stabilising
-directional
-disruptive

Question 20

what is stabilising selection

Answer 20

operates when there is no chnage in the environment and the selective pressures remain the same- range towards mean

Question 21

what is directional selection

Answer 21

directional selection opertes hen there is a change in the environment and the selective pressures change
-end if variation range more favourable

Question 22

what is disruptive selection

Answer 22

two extremes of a range are selected for and river a period of time in which the middle range disappears

due to extreme enviro change - causes two distinct habitats nd two distinct selective pressures - results in speciation

Question 23

give an example of stabilising selection

Answer 23

human birth wieght

-too low - die as organs not developed
-too high- die in childbirth

selective pressures
-mothers health and nutrition
-birth process
-avaliability of medical intervention

steps to combat
-high birth weight- forceps and c-section
-low - neonatal care eg incubators and drugs

Question 24

give an example of directional selection

Answer 24

antibiotic resistance in bacteria

Question 25

what are antibiotics

Answer 25

chemicals which kill or inhibit bacteria but do not affect human cells

Question 26

give an example of an antibiotic

Answer 26

penecillin - acts by preventing the cell wall from forming - high osmotic so the bacterial cells burst

however do not affect human cells as humans do not have meurin in cell wall

Question 27

how does bacterial resistance occur

Answer 27

by random chance mutation
develop resistant alleles to antibiotic
so have selective advantage
will survive and pass on resistant alleles

will have no competition as the non-resitant bacteria will all be killed - so can quickly replicate by binary fission

Question 28

how do humans combat resistant strains

Answer 28

use selective pressures-
and limit use of that specific antibiotic to prevent multiple resistance

Question 29

what are the two ways in which alleles can be passed via bacterial DNA in plasmids

Answer 29

horizontal transmission (one generation)
-process of conjunction
-two bacterial cells become joined by a thin cytoplasmic bridge - conjunction tube
-donor cell replicates its DNA and copy is passes to the recipient
-therefore enquires characteristics encoded by DNA

vertical transmission(multiple generations)
-divide via binary fission
-plasmids repliacted as well as bacterial chromo
-daughter cells also have copy of resistant allele

Question 30

how do bacteria develop multiple resistance

Answer 30

-random chance mutation
-one strain of bacteria resistant to one particular antibody
-another strain of bacteria has acquires resistance to another antibody- the antibiotic will select the resistant cells
-2 strains can then exchange genes by conjugation and the resulting strain is now resistant to both antibiotics
-over-use of antibiotics =s has resulted in development and selection of bacteria with multiple resistance

Question 31

what is MRSA

Answer 31

methicillin-resistant Staphylococcus aureus
-strain of bacteria that has developed multiple resistance
-can cause boils and pneumonia

-developed due to over-use of antibiotics and the fact that many patients do not have the full course of antibiotics - and more chance of resistant genes spreading via transmission

-used in intensive farming to prevent disease

Question 32

why is MRSA a problem in hospitals

Answer 32

-people in hospitals tend to be weaker and older than general pop - so more vulnerable to infection-weaker immune system
-more people in small area - transmitted easier
-over-use of antibiotics

Question 33

how are hospitals tackling MRSA

Answer 33

-improved hygiene
-limit misuse and over-use of antibiotics

Question 34

how do doctors treat the bacterial infection tuberculosis

Answer 34

with a mix of antibiotics so at least one will be effective in treatment- pop killed of quick

Question 35

peppered moth explanation of origin

Answer 35

Before the Industrial Revolution, peppered moths were predominantly white. This allowed them to camouflage with the light-coloured trees and lichens in their habitat.
The environment changed when the Industrial Revolution darkened the trees with soot.- produce SO2 - fossil fuel
The white moths became easier for predators to spot and the white colour was now selected against.
Natural selection caused the frequency of the black-coloured moth to increase because the black colouration became more favourable.

Question 36

peppered moth exam answer - how is one moth more common - in case of peppered

Answer 36

-random chance mutation
-has selective advan - more camouflaged in the countryside etc
-advan over selective pressures
-more likely to survive and achieve differential reproductive success
-pass on alleles so allele frequency changes
-and frequency of peppered colouration is more favorable

converse for melanic
and for why one colour died out

Question 37

what is genetic drift

Answer 37

When a population is significantly small, chance can affect which alleles get passed onto the next generation
Over time some alleles can be lost or favoured purely by chance
When there is a gradual change in allele frequencies in a small population due to chance and not natural selection then genetic drift is occurring

Question 38

suggest how u could measure the genetic diveristy of a pop

Answer 38

-take DNA samples
-compare DNA base sequences of the same genes
-divide numver of different alleles by number of pop
-convert mean into frequency