Ecology Flashcards
(107 cards)
1
Q
define ecology
A
study of an ecosystem, and interactions
2
Q
define ecosystem
A
living and non-living organisms interacting in an area
3
Q
define biotic factor
A
living factor
4
Q
define abiotic factor
A
non-living factor
5
Q
define habitat
A
where an organism lives
6
Q
define population
A
all the same species in a place at the same time that are able to interbreed to produce fertile offspring
7
Q
define community
A
total number of species in a population
8
Q
define niche of species
A
specific rile the organisms plays in an ecosystem
9
Q
what type of organisms are decomposers
A
- bacteria
- fungi
10
Q
what affects population size
A
- births
- death
- immigration
- emmigration
11
Q
linear vs log graphs
A
- log offers the advantage where there a large range of values
- allow all data points to be represented accurately and patterns to be observed
12
Q
population growth curve stages
A
1) lag phase - slow change due to small numbers
2) log phase - rapid change due to increasing numbers
3) stationary phase - a stable population that fluctuates around the carrying capacity
13
Q
what is carrying capacity
A
maximum population size that can be maintained in an environment. its dependent on the limiting factors present
14
Q
what factor is density dependant?
A
biotic factors
abiotic actors are density independant
15
Q
the two types of sampling?
A
- random
- systematic
16
Q
what is random sampling
A
-eliminates bias and allows for statistical testing
- used to estimate size of a population
17
Q
what is systematic sampling
A
- used when there appears to be gradual change in the distribution of a species
- used to determine the relationship between the distribution and an abiotic factor
18
Q
how to carry out random sampling
A
- divide the area into aa grid
- generate pairs of numbers as coordinates
- use a large number of quadrats (>10) to improve reliability
- record abundance of species present in each quadrat (count individuals,% cover )
19
Q
point quadrats
A
- every plant on each pin hits is recorded. if the pin hits several overlapping plants all of them are recorded
- quadrat is placed at regular intervals across the tape measure
20
Q
‘in/out’ rule
A
top or right = IN
bottom or left = OUT
21
Q
things to consider when using quadrats:
A
1) size of the quadrat - the smaller the quadrat the greater the accuracy
2) number of samples being taken in the area - more samples you take the more reliable the results are
3) placing quadrat at coordinates - i.e. bottom left corner on coordinates
22
Q
drawing the graph
A
- plot the cumulative number of species or mean density against the number of quadrats used
- there is no need to use more quadrats once the line plateaus
23
Q
equation for estimated mean density
A
total no. of individuals counted / (number of quadrats x area of quadrat)
24
Q
equation for population total
A
mean per quadrat x no. of quadrats that fit into the sampled area
25
how to measure abundance
- species frequency - no. of quadrats that contain the species
- percentage cover - how much of the area in a quadrat is covered by a particular species. useful for species that are difficult to count e.g. grass
26
what are transects?
types?
systematic technique
- line transect -all individual touching the line are required
- continuous belt transect - all species within quadrats are recorded
- interrupted blet transect - all species are counted at set intervals
27
how to sample animals
capture, mark, release (Lincoln index)
1. a set of animals are caught and then marked in some way
2. animals are then released back into the community
3. after a specified length of time, several individuals are caught again
4. the number of marked individuals are counted
28
population size calculation via Lincoln index
no in the first sample x no in the second sample/number of marked individuals recaptured
29
what is the assumption that has to be made
- the proportion of marked to unmarked is the same in the sample as it is in the whole population
- method of marking must not be toxic, overly conspicuous or rub off
30
for the assumption to be true, what has to happen
- marked individuals need to be distributed evenly in the population
- defined boundaries of the population
- few deaths/births within the time frame
31
what is succession
a change in community over time
32
what is a community
a dynamic unit and passes through a number of stages from its origin to its climax
33
when do transitions take place
occur from one seral stage to the next as the abiotic and biotic factors change
as transitions occur the species present in the previous stage are outcompeted
34
the first species to colonise an area are called
pioneer species
35
features of pioneer species
- small, grow and reproduce quickly
- exploits sudden favourable change in conditions
- short-lived as outcompete by more complex organism
36
what happens when pioneer species die
change the abiotic factors and makes them more favorable for later species e.g. organic matter
37
final set of species to colonise an area are?
climax community
community stability is the greatest once the climax community
38
what is primary succession
when a community develops on uncolonized ground (bare ground) which has never had any vegetation
39
secondary succession
occur in areas which have previously been colonsied by vegetation, but has been colonised
e.g. forest fire
40
what is a plagioclimax?
when does it occur
deflected climax community
occurs when the normal process of succession is prevented e.g. intensive grazing. by sheep, cutting grass
41
what is a gene
an inherited instruction which codes for a polypeptide
42
what is an allele
alternative forms of the same gene alleles arise because of mutation
43
what is a genotype
genetic constitution (make up) of an organism
44
what is a phenotype
observable trait(s) of an organism
45
monohybrid cross
across in which the alleles of only one gene are involved
46
what is a test cross
type of genetic cross to determine the genotype of organisms expressing the dominant phenotype
47
what is codominance
alleles of a gene have to share dominance of a characteristic.
both dominant alleles are present the phenotype shows a mixture of the two characteristics
48
how to lay out a genetic cross
- parents phenotype
- parents genotype
- gamete genotype
- offspring genotype
- offspring phenotype
- ratio
49
name the blood groups
- A
- B
- AB
- O
50
blood group features
- autosomal - not on the sex chromosome
- multiple alleles - more than two alleles for the gene
51
blood group formula
( I A = I B) > I O
IA & IB are codominant and both of these alleles are dominant to IO
52
what is dihybrid inheritance
two genes, two alleles each
genes are on separate chromosomes (unlinked) they can be inherited in any combination
4 possible gametes can be prodcuted
53
dihybrid inheritance
What are the results if the parents are both heterozygous
9 : 3 : 3 : 1
54
dihybrid inheritance
results if one parent is homozygous recessive
1 : 1 : 1 : 1
55
sex chromosomes for most species
normally female: XX
male: XY
56
what is said when a gene is on a sex chromosome
every gene on the sex chromosomes is sex linked
57
difference between the x and y chromosome
- y chromosome is smaller so for many genes on the x chromosome there is no homologous pair present on the y
- so characteristics caused by recessive alleles have a greater change appearing in males
58
what do you have to write when talking about sex-linked characteristics?
you must show the sex chromosomes as well as the alleles
59
competition occurs for limited resources such as
- food
- shelter
- nesting sites
- mates
- light
- territory
- mineral ions
60
intraspecific competition
competition in the same species living in the same habitat
61
interspecific competition
competition between different species in the same community
62
features of intraspecific competition
- availability for resources will determine the size of the population
- individuals best adapted will survive and pass on their alleles while others die out
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features of interspecific competition
the more similar the species are the more intense the competition is
64
what is the competitive exclusion principle
two species will never occupy the same niche and both survive
65
what is predation
when one species is caught and eaten by another species. The populations of the predator and prey will both affect one another. This is called a predator-prey relationship
66
The predator-prey relationship and occurs as follows:
1. When the predator eats the prey, the prey population falls.
2. So predator population grows, so more prey is consumed.
3. The population of prey reduces and there is increased competition for the prey between the predators.
4. The lack of food for the predators means that the population falls meaning that less prey is eaten.
5. This allows the population of the prey to recover and therefore the cycle occurs over
67
what is conservation
human management of the Earth’s resources and involves managing succession.
68
what are linked genes
linked genes are a set of genes at different loci on the same chromosome that except for crossing over will be inherited together
69
when will crossing over occur
if genes are far apart they may be separated by crossing over
70
what will happen if linked genes are close together
unlikely to be separated by crossing over, so will be inherited together
71
what does it mean if you have offspring in intermediate categories in a test cross (linked genes)
there has been some crossing over - alleles are linked
72
if there's no crossing over in a test cross (linked genes) what will the ratio be
1 : 0: 0: 1
73
forming a hypothesis for chi-squared test
There is no difference between the observed and expected results
74
How to work out degrees of freedom
Classes - 1
75
When would you accept the null hypothesis
if the calculated value is less than the critical value
76
what is polygenic?
when characteristics are determined by more than one gene
77
what is epistasis
when alleles of one gene mask the expression of the alleles of another gene
78
what is dominant epistasis
dominant allele at one gene locus masks the expression of alleles at a second gene locus
79
dominant epistasis
heterozygous cross ratio
12 : 3: 1
80
what is recessive epistasis
two recessive alleles at one gene locus will mask the expression of alleles at a second gene locus
81
recessive epistasis
heterozygous cross with the same parents
9: 3: 4
82
what is a gene pool
all of the alleles of all of the genes present in a population
83
what is the allele frequency
number of times an allele appears within a gene pool
84
what is the Hardy-Weinberg principle used for
calculate the frequencies of the different alleles of a gene in a population
85
what does the hardy Weinberg principle assume
that frequencies of the alleles in a population remain constant between generations
86
assumption of the hardy-Weinberg principle to be accurate
1. no selection
2. no mutation
3. no migration
4. population needs to be large enough
5. random mating
87
hardy Weinberg principle
reason for no selection
all alleles are likely to be passed on
88
hardy Weinberg principle
reason for no mutation
no new alleles are created
89
hardy Weinberg principle
reason for migration
no new alleles are introduced or lost
90
hardy Weinberg principle
reason for the population being large enough
there are no genetic bottlenecks
91
hardy Weinberg principle
reason for random mating
alleles are mixed randomly
92
hardy Weinberg principle
allele equations
p + q = 1
p = frequency of dominant allele
q = frequency of recessive allele
93
hardy Weinberg principle
genotypes equations
p2 + 2pq + q2 = 1
p2 = frequency of homozygous dominant
q2 = frequency of homozygous recessive
2pq = frequency of heterozygous
94
Variation in phenotype
1. Random fertilisation - different alleles will join randomly.
2. Meiosis - nuclear division that creates gametes and the alleles will be assorted in the gametes randomly
3. Mutation - creation of new allele that is passed to the next generation
95
what is variation
the difference that exists between individual organisms
96
two types of variation
- interspecific - variation between species
- intraspecific - variation between members of the same species
97
how does variation occur
can be inherited or influenced by the environment
98
continuous variation features
- consists of a range of values between two extremes
- most individuals are close to a mean value
- low numbers of individuals at the extremes
- usually polygenic and affected by the environment
99
examples of continuous variation and how it would be plot
- height in humans
- length of stalks of a toadstool
usually a tally chart and plot result in a histogram - curve is bell-shaped
100
discontinuous variation features
- 2 or more distinct categories with no intermediate values
- monogenic
- the environment has little or no effect on discontinuous variation
101
examples of discontinuous variation and how it would be plot
- earlobes - attahced or unattahced
- blood groups - A, B, AB, O
plot results on a bar chart
102
directional selection
acts against one of the extremes in a range of phenotypes. One phenotype becomes rare, and an alternative phenotype becomes common
103
stabilising selection features
- acts against both extremes - choose median
- leads to a reduction in variation
104
disruptive selection
selection that removes individuals from the centre of the phenotypic distribution and causes the distribution to become bimodal (two peaks)
105
features of disruptive selection
- over time the extremes will become more common and the intermediate states will become less common or lost
- can lead to different species
106
what is speciation
development of a new species from an existing one. caused by reproductive isolation - can no longer breed to produce fertile offspring
107
when can speciation occur
geographical barrier (physical) barrier - allopatric speciation, or without a barrier - sympatric speciation
