7. Genetics Populations and Ecosystems Flashcards
1
Q
what is a population?
A
a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed
2
Q
what is a habitat?
A
the part of an ecosystem where an organism lives
3
Q
what is a community?
A
all the populations of different species living in the same habitat at the same time
4
Q
what is an ecosystem?
A
a community of all living and non living components of an environment (the biotic and abiotic factors)
5
Q
what is a niche?
A
the role of a species within an ecosystem and their habitat, including their position in the food web and what they eat. governed by adaptation to abiotic and biotic factors. no two species have the same niche.
6
Q
what is the carrying capacity?
A
the maximum population size an ecosystem can support
7
Q
what are the abiotic factors?
A
the non living features of an ecosystem eg the temperature and the water availability
8
Q
what are the biotic factors?
A
the living factors eg. the presence of predators and food
9
Q
the niche a species occupies within a population includes what?
A
its biotic interactions - what it eats and what its eaten by
its abiotic interactions - eg the oxygen it breaths in and the co2 it breaths out
10
Q
what is a species?
A
organisms that can interbreed to produce fertile offspring (can exist as one or more populations)
11
Q
give 6 examples of abiotic factors
A
- temperature
- oxygen
- carbon dioxide concentration
- light intensity
- pH
-soil conditions
12
Q
what is evolution?
A
the change in the allele frequencies in a population
13
Q
what are the three types of selection?
A
directional
stabillising
disruptive
14
Q
what is directional selection?
A
when the extreme trait has the selective advantage, so organisms with alleles that code for an extreme trait are more likely to survive and reproduce. this is in response to an environmental change.
15
Q
what is stabilising selection?
A
when the modal trait (organisms with alleles that code for characteristics towards the middle of the range) are more likely to survive and reproduce. occurs when there is no environmental change.
16
Q
what is disruptive selection?
A
when extreme traits on both ends of the range have the selective advantage
17
Q
what is an adaptation?
A
a feature that increases an organisms chance of survival and reproduction
18
Q
state and describe the three types of adaptation
A
behavioural = the way the organism acts, such as migrating to find food
physiological = internal biological functions helping the organism survive
structural = features of an organisms body that help it survive
19
Q
by what process do adaptations develop?
A
natural selection
20
Q
explain how natural selection increases an organisms chances of survival
A
- organisms better adapted to the environment are more likely to survive and reproduce
- by doing this, they will pass on their alleles
- thus, the frequency of this allele will become increase within the population
21
Q
give two examples of biotic factors that can affect population size
A
competition and predation
22
Q
what is interspecific competition?
A
when members of different species compete for the same resources that are in limited supply.
(the individual better adapted to the environment is more likely to succeed in the competition)
23
Q
what is intraspecific competition?
A
when members of the same species compete for resources and a mate. (individuals that are fitter, have more energy or are in better condition are more likely to attract the mate)
24
Q
state 4 things that species may compete for
A
- space
- food
- water
- a mate
25
what is the general strategy for taking a random sample?
- chose a random area to sample to avoid bias by dividing the field into a grid, and then using a random number generator to select coordinates
- chose an appropriate technique to take a sample (eg. quadrats or transects)
- repeat the process, taking as many samples as possible (reducing the likelyhood results are down to chance)
- number of individuals in the whole area can be estimated by taking a mean of the data in each sample and then multiplying it by the size of the whole area
26
describe the population relationship between predators and prey
- as the prey population increases, theres more food for the predators, so the predator population increases.
- however, as the predator population increases, more prey is eaten, so the prey population begins to fall.
- this means theres less food for the predators, so their population decreases too.
27
how to ensure samples accuratley represent the population?
random sampling in uniform areas to eliminate bias
- line transects to examine a change over distance
- a large number of samples (30+) to ensure your accuratley representing the population
28
when is it appropriate to use a quadrat?
- when the sample contains slow/non moving organisms
- when the organisms are uniformly distributed in the area
29
when do we use a line transect?
- when there is uneven distribution of organisms in the area (populations that change over distance)
- when the sample contains slow/non moving organisms
30
with moving organisms, what sampling technique do we use?
mark-release-recapture method
31
describe how the mark-release-recapture method works
include the equation
- an initial sample of the population is captured
- these individuals are marked and then released back into the wild, and the number of marked individuals is recorded (mark must be weather resistant)
- marked individuals are then left for a period of time to allow them to randomly disperse throughout the habitat
- the second sample is then captured
- the total number captured in the second sample is recorded, and the number recaptured is also recorded
- the process is repeated multiple times, and a mean is then calculated for more reliable results
population size = (number initially captured x number in second sample) / number marked in second sample
32
what are the ethics to consider when doing the capture-recapture method?
- how organisms are captured and marked must not cause permanent harm
- the mark must be non toxic
- mark must not increase chances of predation or reduce chances of reproduction
33
what are the assumptions associated with the capture recapture method?
- that the population size is constant (no birth/death or migration)
- that the animals always distribute evenly (they may all huddle near food in reality)
34
how would a student use a quadrat to estimate a sample population on a uniformly distributed field of daisies? (6)
1. lie two tape measures at a right angle to create a gridded area
2. use a random number generator to generate two coordinates
3. place the quadrat and collect the data (calculate the percentage cover or the frequency of the daisies)
4. repeat this process at least 30 times and then calculate a mean, before multiplying by the size of the field.
35
what are the two different types of line transect?
the belt transect and the interrupted belt transect
36
how does a belt transect work?
the quadrats are placed next to eachother along the transect
37
how does an interrupted belt transect work?
the quadrat is placed at uniform intervals along the tape measure with spaces in between them eg. every five metres (to cover a larger distance OR if not much distance will be observed using a belt transect)
38
describe a method as to how a student would set up and conduct a sampling experiment using a line transect (4-6)
- place a tape measure at a right angle to the shore line
- take a 1m quadrat divided into 100 squares and place it next to the tape measure every 5 meters/ next to eachother
- count the squares containing organism and calculate the percentage cover, then record this in a table
- repeat by placing another 30 transects at right angles to the shore line along your sampling area
39
state and describe the different methods that can be used to estimate the abundance of a species
1. local frequency = the % of squares in the quadrat with the species present
2. density = count how many of one species you have within the quadrat (eg how many daisies) and then apply this to the area of the field
3. percentage cover = the % of full squares occupied within the quadrat
40
what are the advantages and disadvantages of using the local frequency method?
advantages = quick method to sample a large area, and useful if its too difficult to identify individual organism or too many to count
disadvantages = poor accuracy as it doesnt consider overlapping plants or the size of the plant
41
what are the advantages and disadvantages of using the density method?
more accurate if you can easily distinguish an individual plant, and there are not too many to count. can be used to estimate species richness
more time consuming
42
what are the advantages and disadvantages of using the percentage cover method
advantages = quicker method than density, and useful if its too difficult to identify the individual organism or if theres too many to count
disadvantages = subjective, which limits accuracy. and doesnt consider overlapping plants or the size of the plant
43
describe how you could estimate the size of a population of sundews (motile species) in a small marsh
- capture sample, mark them and release them back into the environment
- leave time for them to disperse before the second collection
- the population is equal to (number marked in first sample x the total number in second sample) / the number marked in second sample
44
state the four different phases of a sample population growth curve
lag phase
log phase
stationary phase
death phase
45
recall six events that occur during the lag phase on a population growth curve
genes switch on
enzyme synthesis
dna replication
protein synthesis
digestion and absorption
46
recall four events that occur during the log (exponential) phase on a population growth curve
high nutrient availability
high oxygen levels
less intra-specific competition
waste products havent yet reached a toxic level
47
recall what happens during the stationary and death phases on a population growth cure
stationary = the birth rate is equal to the death rate
death = the birth rate is lower than the death rate
48
why is a log scale used to record the number of cells?
because there is a large range / increase in numbers
49
define succession
the gradual directional change in an ecological community over time
50
what are each of the stages during succession called?
the seral stages
51
what is the final seral stage of succession? (the end result)
the climax community
52
what are the two types of succession?
primary and secondary succession
53
when does primary succession occur?
- happens on land thats been newly formed or exposed - eg where a volcano has just erupted or where sea level has dropped exposing land
- theres no soil or organic material to begin with, just bare rock
54
what is the first species to ever colonise bare rock or sand called?
the pioneer species
55
what are pioneer species adapted to do?
survive in harsh abiotic factors
56
describe and explain how primary succession occurs
- pioneer species colonise the area
- they then change the environment and make it less hostile by decaying, leaving behind a soil called humus that contains nutrients
- this enables other species colonise the area and survive
- some new species change the environment, which makes it les suitable for the previous species
- the soil becomes more fertile, so a range of plants can grow which increases the habitats for other organisms
- biodiversity changes (increases)
- the environment becomes more stable, and the climax community forms after a few hundred years
57
when does secondary succession occur?
when a primary succession becomes disrupted - eg. the present community becomes destroyed.
- so, succession starts again, but the soil is already created so it does not start from the bare rock seral stage.
58
what happens during secondary succession?
species richness and number of organisms increases (biodiversity increases)
- as succession occurs, larger plant species and animals colonise the area
- therefore food webs become more complex
59
define what is meant by conservation
the maintenance of biodiversity and genetic diversity within a species and also the variety of habitats and ecosystems
60
what is typically the reason for the destruction of habitats, and what does this lead to?
what is done because of this?
human activity
a loss of food and space for organisms and can lead to extinction
to conserve habitats, succession is often managed.
61
what are the advantages of maintaining earlier stages of succession and preventing the climax community?
a greater variety of habitats are conserved and therefore a greater range of species
62
what is speciation?
the process that results in the creation of a new species
63
what is the primary source of genetic variation?
mutation
64
name two other factors that produce further genetic variation
- meiosis
- random fertilisation of gametes
65
why does speciation occur?
because one original population of the same species becomes reproductivley isolated, which means there are now two populations of the same species that cannot breed together
66
what is the consequence of speciation
the accumulation of differences in their gene pools, causing a change in phenotype - to the extent that the two populations would be unable to interbreed to produce fertile offspring - and therefore classed as two different species
67
what are the two ways organisms can become reproductivley isolated?
allopatric speciation
sympatric speciation
68
what is allopatric speciation and explain how it works
when populations are separated geographically, by a physical barrier.
this means the populations will experience slightly different conditions, and therefore different selection pressures. so, different changes in allele frequencies occur. different alleles will become more advantageous in different populations. the changes in allele frequency will lead to changes in the gene pools of the separated populations, causing changes in phenotype frequencies. over generations, individuals from the different populations will have changed so much that they wont be able to breed with eachother to produce fertile offspring, so they have become reproductivley isolated.
69
what is sympatric speciation and explain how it works
occurs when two populations are geographically in the same location, but random mutations occur within the population, preventing members of that population breeding with the other members of the species. this can be due to differences in behaviour (eg the mutation affected the courtship ritual) or even changes in when individuals become fertile. these would mean they would not be able to reproduce together and there will be no gene flow between the two groups of organisms. over generations, these reproductivley isolated populations will accumulate different mutations to the extent their DNA is so different they cannot interbreed to create fertile offspring and therefore are classed as two different species.
70
what is genetic drift? and why does it affect smaller populations more than larger populations?
the change in allele frequency within a population between generations.
- it only has an impact on smaller populations.
- only substantial genetic drift results in evolution.
- however in smaller populations, even the slightest change in allele frequency has a large impact.
71
what is the gene pool?
the complete range of alleles present in a population
72
what is a locus?
the fixed location of a gene on a chromosome
73
define diploid
term applied to cells in the nucleus that have two sets of chromosomes
74
define haploid
a term applied to cells in the nucleus that only contain a single copy of each chromosome
75
what is an allele?
one of a number of alternatives forms of a gene
76
what is a recessive allele?
an allele that is only expressed in the phenotype when both alleles are recessive/no dominant allele
77
what is a dominant allele?
an allele that is always expressed in the phenotype of an organism
78
define codominant?
when both alleles are expressed in the phenotype
79
define homozygous
when the alleles are the same for a particular gene
80
define heterozygous
when the alleles are different for a particular gene
81
define genotype
the genetic constitution of an organism
82
define phenotype
the physical characteristics of an organism due to its genotype and its interaction with the environment
83
what letter chromosomes do males have?
what letter chromosomes do females have?
males = XY
females = XX
84
are there any alleles on the Y chromosome?
no
85
what is a carrier?
an individual who is heterozygous for a condition (caused by a recessive allele), but it is not expressed in their own phenotype, and can be passed on to their offspring
86
explain why a trait caused by a recessive allele would be more common in men than in women
- males are XY and females are XX /males only have one X chromosome, whereas females have two
- males only have one allele of the gene, recessive allele is always expressed
- whereas female needs two recessive alleles/recessive allele may be masked by a dominant allele
- as there are no alleles on the Y chromosome
87
when dealing with dihybrid parents, what method do we use to determine the gametes?
FOIL
first, outside, inside, last
88
what ratio will offspring be produced in if organisms are heterozygous for both genes
9:3:3:1
89
what ratio will offspring be produced in if organisms are heterozygous and linked?
3:1
90
what is autosomal linkage?
when two genes are on the same chromosome
91
what is an autosome?
any chromosome that ISNT a sex chromosome
92
what would be the evidence for a recessive trait on a pedigree analysis chart?
two parents that do not have the trait but an offspring that does
- this means the parents must be heterozygous carriers, as they have the recessive allele but its not expressed in their phenotype
93
what would be the evidence for a dominant trait on a pedigree analysis chart?
two parents who do have the condition, and a child that does not
- this is because the parents must be heterozygous dominant and therefore carriers of the recessive allele
94
what is sex linkage?
when the gene is on the X or Y chromosome
95
what is the evidence for a sex linked trait
always seen in males and not in females (only the case if trait is recessive)
96
what is the evidence that a trait is not sex linked on a pedigree analysis chart?
males and their daughters = males always pass their X chromosome onto their daughters.
an affected male cannot have an unaffected daughter if condition is caused by a dominant allele
OR
mothers and their sons = if it was sex linked, sons always inherit their X chromosome from their mothers.
with a condition caused by a recessive allele, an affected mother cannot have an unaffected son.
97
what is epistasis?
the interaction of different genes. when the gene at one locus influences the expression of another gene at another locus
98
what is the general null hypothesis in genetics?
there is no significant difference in the phenotype ratio expected of___ and the phenotype ratio observed. Any deviation from the expected ratio is due to chance.
99
what is the purpose of the chi squared experiment?
to compare how well the observed results match the expected results
100
method for answering a chi-squared question
- work out the expected number of organisms by applying the ratio to the actual number of organisms
- take the observed values from the expected values (O-E)
- square each value of O-E
- divide (O-E)^2 by the expected values
- then add together all the values from the previous step
- choose your number of degrees of freedom by subtracting 1 from the total number of phenotypes
- always use 0.05 probability
- if the chi squared value is LESS than the critical value, you can accept the null hypothesis (difference isnt significant)
- if the chi squared value is GREATER than the critical value, reject the null hypothesis as the difference IS significant
then answer the question like this : using __ degrees of freedom and 0.05 probability, the critical value was__. the chi squared value is __ which is less/more than the critical value, so we can accept/reject the null hypothesis as the difference is/isnt significant and there is a 0.05 probability the results are/arent due to chance
101
what is allele frequency?
the proportion of a particular type of allele in a population
102
what is genotype frequency?
what is phenotype frequency?
- the proportion of a particular genotype combination in a population
- the proportion of a particular physical characteristic in a population
103
what does the hardy weinberg principle state?
the frequencies of dominant alleles, recessive alleles, and genotypes wont change in a population from one generation to the next if certain conditions are met
104
what are the 5 conditions required for the hardy weinberg principle
- very large population
- no emmigration or immigration
- no mutations
- random mating
- no selection pressures & natural selection
105
what are the two hardy weinberg equations?
what do the different components of the equation mean?
p+q=1
p2 + 2pq + q2
p = frequency of the dominant allele
q = frequency of the recessive allele
p2 = frequency of dominant homozygous allele
2pq = frequency of dominant heterozygous genotype
q2 = frequency of recessive homozygous genotype
106
in the hardy weinberg calculation, what is the frequency of dominant alleles (homozygous and heterozygous) represented by?
how would you rearrange the equation to find p2?
p2 + 2pq
take this from one and then square root
