Topic 7 - Genetics, populations, evolution and ecosystems Flashcards
1
Q
what is meant by the term genotype
A
the genetic constitution of an organism/ the genetic makeup of an organism, made up of alleles which determine a particular feature
2
Q
what does a dihybrid cross determine
A
the genotypic and phenotypic combinations of offspring for two particular genes that are unlinked
3
Q
how many gamete combinations will there be for 2 genes with 2 alleles each
A
4
4
Q
define genetics
A
the study of inheritance
5
Q
define phenotype
A
the features resulting from the expression of the genes and their interaction with the environment
6
Q
define genome
A
the total genetic makeup of an organism
7
Q
define gene
A
a section of DNA that codes for a particular protein
8
Q
define dominant
A
alleles that always appear in the phenotype shown by capital letters
9
Q
define recessive
A
alleles that are only expresed if both alleles of a pair are present, shown by lower case letters
10
Q
define homozygous
A
two alleles of a pair are the same
11
Q
define heterozygous
A
two alleles of a pair are different
12
Q
define homozygous recessive
A
this describes an individual who has two recessive alleles of the same gene
13
Q
define homozygous dominant
A
an individual who has two dominant alleles of the same gene
14
Q
what is codominance
A
when both alleles are expressed in the phenotype
e.g. CRCR = Red flowers
CRCW = pink flowers
CWCW = white flowers
15
Q
what do we call it when a lethal allele is expressed later in life
A
genetic disease
16
Q
what is sex linked characteristics
A
when there are different genes for males and females
17
Q
true or false
males never inherit their X chromosome from their mothers and pass it on to their daughters
A
false
males always inherit their X chromosome from their mothers and pass it on to their daughters
18
Q
what is the chromosome for females
A
XX
19
Q
what is the chromosome for males
A
XY
20
Q
what is the phenotype ratio when two heterozygous parents are crossed
A
9:3:3:1
21
Q
what is the phenotype ratio when heterozygous chromosome parents is crossed
A
3:1
22
Q
using x and y what is the genotype for the description ‘homozygous dominant, homozygous dominant’
A
XXYY
23
Q
what is an autosome
A
a chromosome that isn’t a sex chromosome
24
Q
when does autosomal linkage of genes occur
A
when two genes are on the same chromosome
25
how could there be more genetic variation for gamates
crossing over due to weak linkage
26
finish the sentence:
the closer together the gene loci are on a chromosome...
the lower the chance of chiasma forming btwn them and separating them
27
why are the possible number of genotypes in the offspring reduced
when genes are on the same chromosome, they cannot be separated in meiosis I [independent assortment of homologous chromosomes], so two linked genes are passed into the gamete together and are inherited together
28
ratio for dihybrid unlinked vs autosomal linkage
dihybrid: 9:3:3:1
autosomal: 3:1
29
define epistasis
the genes at one locus interect with genes at another locus by masking or surpressing their expression
30
define allele
alternate version of a gene
31
what is the hardy-weinberg principle
a mathematical model which can be used to predict the allele frequency w/n a population
32
define species
a group or organisms with similar characteristics which can breed to produce fertile offspring and reproductively separated from other speicies
33
define population
group of organisms of the same species living in a particular area at a particular time
34
define gene pool
all alleles of the genes within a population at one time
35
define allele frequency
the proportion of an allele within the gene pool/how often an allele occurs in a popoulation (given as a % or number)
36
how does assumptions effect accuracy
it impedes it
37
what assumptions are made in the hardy-weinberg model
- large population
- no migration to introduce/remove alleles
- no mutations
- no selection favouring particular alleles
- mating is random [no selective breeding]
38
what is the equation for the hardy-weinberg equation
p^2+2pq+q^2 = 1
p + q = 1
where:
p = frequency of dominant allele
q = frequency of recessive allele
p^2 = the frequency of the homozygous dominant genotype
2pq = the frequency of the heterozygous genotype
q^2 = the frequency of the homozygous recessive genotype
39
what is genetic diversity
a measure of the number of different alleles in a population/all the different alleles available in the gene pool
40
what type of selection keeps variation around the mean
stabilising
41
what type of selection moves the variation away from the mean
directional
42
what is disruptive selection
when extreme phenotypes are favoured leading to an increase in alleles with distinct phenotypes
43
where does disruptive selection occur and what does this result in
in fluctuating environments where predation favours the middle range phenotype = two peaks at the extremes of the distribution
44
what can continued disruptive selection lead to
speciation (where new species are formed over time)
45
what causes allopatric speciatin
when populations are separated geographically leading to reproductive isolation
46
why does genetic variation always exist
random mutations
47
what could cause geographical isolation
natural disasters
48
what happens in allopatric speciation
- species are separated due to geographical isolation which results in an accumulation of different beneficial mutations = they become genetically different which means they cannot interbreed to produce fertile offspring, becoming 2 different species
49
why does sympatric speciation occur
populations become reproductively isolated due to differences in their behaviour
50
where does sympatric speciation occur
it occurs at a genetic level e.g. due to waking/sleeping patterns
51
how does sympatric speciation occur
the individuals do not see each other due to different changes in mutations, which means that they will not reproduce together = no gene flow = reproductively isolated populations will accumulate different mutations in their DNA which means they cannot interbreed to produce fertile offspring = two different species
52
define genetic drift
the random change of allele frequency due to only some of each generation reproducing
53
genetic drift always occurs from one generation to the next, what does continual and substantial genetic drift result in
evolution
54
what type of population is genetic drift found in
smaller ones
55
what is ecology
the study of relationships between orgnaisms and their environment - biotic and abiotic
56
what do ecologists study
the biosphere, land, air and water surrounding Earth
57
define abiotic
conditions that are physical, non-living parts of environment (e.g. temperature, light intensity, rainfall)
58
define biotic
conditions that invovle the living parts of the envrionment (e.g. competition, predation, disease)
59
define species
a group of organisms that can interbreed to produce fertile offspring
60
define population
all the organisms of one species in a habitat
61
define community
all the populations of different species living an area
62
define habitat
the place where an organism lives within an ecosystem
63
what is interspecific competition
competition for resources btwn members of different species
64
define intraspecific competition
competition for resources between members of the same species
65
what is population size
number of individuals
66
what is population density
number of individuals per unit area
67
what is population growth
change in number of individuals
68
what is population growth rate
change in number of individuals per unit time
69
what do we call the graph that is the most commonly found in population growth rate graphs
sigmoid or S-shaped
70
in signoid graphs, why does the population grow slowly at first
few to reproduce, may not find mate
71
in sigmoid graphs, what causes the exponential growth phase to end
lack of food/space, intraspecific competition, build-up of toxins, increase in disease
72
define carrying capacity
maximum population size which can be sustained. it varies due to abiotic factors and interactions between organisms
73
in sigmoid graphs, what are the factors which limit the size of a population known as
environmental resistance
74
what happens when the population size increases too rapidly
it may go above the carrying capacity of the environment
75
what is a population crash known as
boom and bust
76
what shape of the curve is known as for a boom and bust
J shaped
77
why would carrying capacity decrease
the environment is damaged by overpopulation
78
what factors limit population growth
density dependent factors: the higher the population density the greater the effect. normally biotic factors
density independent factors: have the same effect whatever the population density. normally abiotic factors
79
state two types of relationship btwn predators and their prey
seasonal relationships, larger efficient predators in a yearly cycle
80
describe a negative feedback loop in terms of predators and prey
when predator go up, preys go down, then there's less food so predators go down
81
define ecological niche
how a species lives in relation to all the environmental factors that affect it.
82
what does a population niche refer to
its role in its ecosystem. e.g. feeding role in the food chain - predator, producer, parasite
83
what niches other than its feeding role could a population have
food, habitat, reproduction method, behaviour
84
how does different niches in ecosytems help us
they help use to understand the interactions btwn populations
85
do the members of the same population always have the same niche
yes and they are well adapted
86
what are specialists
species with narrow niches
87
can different specialists coexist in the same habitat
yes when they are not competing
88
what happens when different specialists coexist
leads to high diversity
89
what are generalists
species with broad niches e.g. common crow
90
in the same habitat, will generalists compete and how does this affect the diversity
generalists will compete, leading to low diversity
91
are generalists able to cope with a changing food supply
they can switch from one food to another or even one habitat to another
92
what is optimal niche
the ideal conditions for the individual to reproduce and maintain a viable population
93
when two addverse conditions are combined, what does this lead to
the organism cannot survive
94
what is a potential (fundamental) niche
the potential conditions under which the individual can survive
95
define autotroph
an organism that can convert abiotic sources of energy into energy stored in organic compounds
96
define succession
the change in a community over time due to changes in the abiotic environment
97
what kind of an environment might an ecosystem start with
extreme one e.g. bare rock or barren land
98
why might an ecosystem start with an extreme environment
- glacier retreating and depositing rock
- sand dunes forming by wind or sea
- volcanoes depositing lava
- slit and mud being deposited by reviers
- lakes or ponds being created by land subsidence
99
what does it mean for an ecosystem to be dynamic
they constantly change over time
100
which conditions change over time in succession
biotic and abiotic
101
define primary succession
the process that occurs when newly formed or newly exposed land is gradually colonised by an increasing number of species
102
summarise the process of primary succession
- pinoeer species can survive harsh conditions and colonise the area
- they can change abiotic factors of their environment e.g. decomposition adds nutrients to ground
- over time, this allows more complex organisms to survive
103
what is the climax community
the final stage of succession where the ecosystem is balanced and stable
104
when is the climax community reached
when the soil is rich enough to support large trees or shrubs and the environment is no longer changing
105
how might a species alter the environment that develops during succession
a species may improve the environment to make it more suitable for other species or, a species may worsen the environment by making it less suitable for other species
106
what happens as succession continues
community becomes more diverse with more complex food webs
107
what is the time period difference between primary and secondary succession
primary succession takes thousands of years, secondary takes decades
108
define sere
an alternative name for succession in a community
109
define primary succession
a succession sequence that occurs on land that has not had plants or soil in the past or has been completely cleared of these e.g. by volcanism usually bare rock
110
define abiotic factors
one of the non-living chemical or physical components of an ecosystem
111
define climax community
a community that has reached an equilibrium with the environment and no longer appears to be changing in composition
112
define pagioclimax
a course of succession which differs from the natural course of succession. often as a result of human activity but can also be due to natural cuases
113
define conservation
the active management of natural populations in order to rebuild numbers and ensure species survival
114
define colonising species
a species that is able to grow on bare land and rock, making nutrients available for species that establish later
115
define gap regeration
the regrowth of plants after a space in the canopy is opened, following the loss of a larger tree
116
define secondary succession
a succession sequence that takes place after a land clearance e.g. forest fire or landslide. it does not invovled the loss of seed and root stock
117
define deflected succession
a course of succession which differs from the natural course of succession e.g. as a result of human activity
118
define ecological succession
the progression from initial colonisation of a newly cleared area to a climax community
119
define pioneer community
the earliest community that becomes established on bare site
120
why doesn't secondary succession require pioneer species
the soil is already developed and there is a seedbank
121
what is the impact of human activiity on succession
natural climaax isn't reached due to farmland being weeded. this results in plagioclimax/artifical climax
122
state an ethical rreason why we conserve habitats
we should be able to coexsit with other species on earth and respect them
123
state an economic reason why we conserve habitats
the greater the diversity of organisms, the more substances could be produced, studied and may be valuable in the ftuure
123
state a cultural and aesthetic reason as to why we conserve habitats
ecosystems and wildlife provide us with enjoyment, interest and inspiration
124
when a climax community forms due to succession what happens
some of the species at earlier stages are no longer present, their hbiatats may disappear or may be out-competed
125
if a factor preventing a climax community was removed, what kind of succession would take place
secondary succession
126
what is a climax community also known as
climatic climax
127
give an example of a conservation conflict in the Uk
the conservation of hen harriers and commercial hunting of red grouse - hen harriers prey on red grouse chicks
128
define pioneer species
the first organisms to colonise an inhospitable substrate
129
as small plants die and decay in the soil, what increases
organic matter
130
define seral stage
a distinct community in the sucession
131
