17) Selection & Evolution Flashcards
1
Q
what is phenotypic variation caused by ? [3]
A
- genetics
- environmental factors (availability of food/water)
- genes AND environment
2
Q
what is continuous variation
A
- range of values (line graph/histogram)
- phenotypes are quantitative
- controlled by more than just 2 genes
3
Q
what is discontinuous variation
A
- distinct categories (bar chart)
- qualitative
- controlled by only that set no. of genes
4
Q
how is continuous variation caused
A
- polygenic (controlled by many genes)
- different genes/alleles have additive effect
- environmental factors contribute to variation
5
Q
describe the stages of natural selection
A
- mutation
- variation
- overproduction (environmental factors)
- struggle for existence
- survival of the fittest
- advantageous alleles passed on - allele frequency changes
6
Q
what is selection pressure
A
an environmental factor that confers greater chances of survival and reproduction on some individuals than on others in a population
7
Q
stabilising selection favours and is against..?
A
favours : moderate/intermediate
against : extremes in a phenotypic variation
eg: birth mass
- no change in environment
8
Q
directional selection favours and is against..?
A
favours : one extreme
against : one extreme
eg :
9
Q
disruptive selection favours and is against..?
A
favours : both extremes
against : intermediate
- bimodal distribution
- maintains genetic diversity
10
Q
what is the bottleneck effect?
A
- involuntary/wiped out
- population contracts
- major environmental event can reduce number of individuals in a population
- reduces genetic diversity as alleles are lost
- those that survive reproduce w close relatives
11
Q
what is the founder’s effect?
A
- voluntary
- population splits
- small number of individuals from large parent population start a new population
- not all of the gene pool is present in the new population
12
Q
how do bacteria become resistant to antibiotics (natural selection) [7]
A
- mutation
- directional selection
- antibiotic acts as selection pressure
- bacteria w mutation for resistance have selective advantage
- so survive/reproduce
- allele frequency increases
- increased chance of resistance if people do not finish the full course of antibiotics
13
Q
what is artificial selection [2]
A
- individuals w desired features chosen to breed
- selection by humans
14
Q
explain the process of artificial selection
A
- choose individuals with desired characteristics
- breed
- choose from desirable offspring
- repeat for several generations
- allele for desired characteristic is passed on
- allele frequency increases
- artificial insemination
15
Q
introduction of disease resistance to wheat & rice
A
- select plants resistant to disease
- by exposing them to disease to show resistance
- breed
- select offspring and breed together
- repeat for many generations
- EG of wheat disease = rust disease
16
Q
inbreeding & hybridisation to produce uniform varieties of maize
A
- breed plants w desired characteristics
- breed for many gens
- inbreeding
- produces homozygous plants
- outbreeding
- hybridisation
- hybrids (offspring are all heterozygous)
17
Q
improving milk yield of dairy cattle
A
- choose female w high milk yield
- choose male w sister/mother w high milk yield
- breed from offspring
- repeat for many generations
- allele for high milk yield passed on
- increase in allele frequency
- artificial insemination
18
Q
what is inbreeding
A
breeding between organisms w similar genotypes, or that are closely related
19
Q
how does selective breeding reduce genetic diversity [3]
A
- small number breeding individuals
- may not have all alleles
- loss of alleles due to discarded traits
- inbreeding
- many generations
- decreases heterozygosity
20
Q
what is evolution [3]
A
- formation of new species from pre-existing species
- change in characteristics/phenotypes
- over time/generations
- natural selection
- change in allele frequency/gene pool
21
Q
what is allopatric speciation
A
- geographical barrier (mountain, river)
- so population is separated
- no gene flow between populations
- diff selective pressure
- diff mutations
- adaption to env gives morphological / phenotypic differences
22
Q
what is sympatric speciation
A
- new species form due to reproductive isolation
- caused by ecological/behavioral barriers
- in SAME geographical region
23
Q
what are the conditions for using the t-test?
A
- data must be continuous & normally distributed
- ## similar standard deviations
24
Q
formula for degrees of freedom for t-test
A
n1 + n2 - 2
25
what is the significance level
0.05
26
if the t value is larger than critical value
null hypothesis REJECTED
27
if the t value is smaller than critical value
null hypothesis ACCEPTED
28
t value is always positive (+) so just ignore negative (-)
t value is always positive (+) so just ignore negative (-)
29
what are the conditions needed for Hardy Weinberg principle
- large population
- no migration
- no mutation
- random mating
30
symbol for dominant allele
p
31
symbol for recessive allele
q
32
p^2
given number
33
features that can be improved by selective breeding
- more yield
- better quality
34
how are DNA sequences used to show evolutionary relationships between species
- compare sequences of DNA
- more similar the sequences, more closely related the species
- over time mutations accumulate
- bioinformatics/database
35
outlines processes that may affect allele frequencies
- mutation
- genetic drift
- founder effect
- bottleneck effect
- natural selection
- migration
- genetic recombination (crossing over)
36
what is standard deviation
spread of data around the mean
37
disadvantages of selective breeding
- reduction in genetic variation
- less hybrid vigour
- inbreeding depression
- harmful recessive alleles could be expressed
- susceptible to new disease/environmental change
38
advantages of hybrid population
- more genetic variation
- genes/mutations from both subspecies
- more potential to adapt
- alleles for migration may help them find better habitat
39
outline how practical techniques can be used to conduct genetic analysis of a species
- obtain DNA
- from two individuals at diff locations
- PCR to amplify
- gel electrophoresis
- sequencing of DNA
- use microarray
- bioinformatics/database
- compare similarity
40
desired characteristics
- short ( so less likely to fall over)
- high yield
- resistant to disease
41
how are members of a species similar
- morphological
- physiological
- genetical
- ecologically
- behaviorally
- can interbreed to form fertile offspring
- reproductively isolated from other species
42
explain why species may become extinct
- environment changes
- species cannot adapt
- climate / temperature / sea level, change
- competition from, new species
- extinct species / species at risk
- habitat, degradation / loss
- extinct species / species at risk ;
- hunting by humans / poaching / (over)fishing
- extinct species / species at risk
43
features shared by animal species
- multicellular
- specialised cells
- eukaryotes
44
Some students decided to investigate whether the flies were members of one species or four separate species.
Suggest a simple investigation that the students could carry out
- mate them together
- see if offspring fertile
- bioinformatics investigation
45
what is genetic drift
- random change in allele frequency
- larger influence in smaller population
