unit 7 Flashcards
i do pass my exams, i have never revised the night before, i am a godd srudent
Genotype
the genetic constitution of an
organism
Phenotype
the expression of the genetic
constitution
and its interaction with the
environment
Homozygous
two copies of the same allele for
a gene
Heterozygous
two different alleles for the
same gene.
Recessive allele
An allele that is only expressed
if there are no dominant alleles
present
Dominant allele
An allele that is always
expressed in the phenotype
Codominance
two alleles are both dominant
both are expressed in the
phenotype
Sex-linkage
a gene located on the X
chromosome
in the non-homologous region
Multiple alleles
More than two alleles for a gene
Autosomal
linkage
genes located on
the same
chromosome
(not the X or Y
chromosome)
Epistasis
When one gene masks/modifies
with the expression of another
gene
Monohybrid
The inheritance of one gene
Natural
selection
the process that leads to
evolution in populations
results in species becoming
better adapted to their
environment
Dihybrid
The inheritance of two genes
Differential
reproductive
success
not all individuals are equally
likely to reproduce
results in changes in allele
frequencies within a gene pool
Selection
pressure
factors that affect the survival
of an organism
the driving force of natural
selection
Allele
frequency
The proportion of an allele in
the population
Disruptive
selection
Individuals with either extreme
trait are more likely to survive
and pass on their alleles
the middling trait allele
becomes less frequent
leads to speciation
Speciation
the process that results in the
creation of new species
Reproductively
isolated
Two populations of the same
species, but they cannot breed
together
there is no gene flow
Allopatric
speciation
Two populations become
reproductively isolated due to
being geographically separated
results in the formation of two
new species
Sympatric
speciation
Two populations become
reproductively isolated whilst in
the same location
e.g. due to changes in behaviour
results in the formation of two
new species.
Genetic drift
the change in the allele
frequency within a
population between
generations
occurs from one
generation to the next
substantial genetic drift
results in evolution
Population
All the individuals of one
species in the same area at the
same time
Habitat
The range of physical, biological
and environmental factors in
which a species can live
Community
all the species in a particular
area at a particular time
Niche
An organism’s role within an
ecosystem
their position in the food web
and their habitat
Ecosystem
all the biotic and abiotic factors within an enironment
Carrying
capacity
The maximum population size
an ecosystem can support
Abiotic factors
Non-living conditions of an
ecosystem
Biotic factors
Impact and interactions
between organisms
Interspecific
competition
Competition between members
of different species
Intraspecific
competition
Competition between members
of the same species
Predator-prey
relationship
the interaction between
predator and prey and how this
affects their population sizes
When would you
use random
sampling?
when there is a uniform
distribution of the plant species
to avoid bias
Quadrat
a frame
gridded or opened
used to sample non-motile
organisms
When would you
use a line
transect
When sampling a non-uniform
area
e.g. a rocky shore
What must you do
to ensure your
samples are
representative?
Take a large sample (at least
30)
randomly sample
Belt transect
one tape measure is placed
through an ecosystem that is
not uniform
the quadrat is placed at every
position along a tape measure
Interrupted belt
transect
one tape measure is placed
through an ecosystem that is
not uniform
the quadrat is placed at set
intervals along the tape
measure
The 3 measurements
you can take when
counting plants in a
quadrat?
density
percentage cover
frequency
Density
measurement
when you count the individuals
present
Frequency
measurement
count how many squares out of
the 100 contain the species you
are investigating
Percentage cover
measurement
investigator estimates the
percentage of the entire quadrat
covered with the species that is
being investigated
standardise by counting 1% for
every small square that is at
least half covered by the plant
When would you
use mark-releaserecapture?
Estimate the population size of
motile organisms
What is a
succession?
the change in an ecological
community over time
What is a
primary
succession
a succession with a pioneer
species colonising a hostile environment e.g. bare rock or
sand
the first time the land is
colonised
becomes gradually less hostile over time
pioneer species then dies out
What is a
secondary
succession?
there is a disruption that
causes plants to be destroyed
succession starts again, but the
soil is already formed
Pioneer
species
The first species to colonise an
area
e.g. lichen
Climax
community
The final seral stage in
succession
the most stable stage
Humus
A thin layer of soil that forms in
early primary succession
Conservation of
habitats
Protecting habitats as a means
to protect species
maintains habitats and food
sources
What is the
advantage of
managing succession?
Conserves a range of habitats
and a range of food sources
enabling a wider range of
species to survive
Hardy-Weinberg
principle
a mathematical model used to
predict the allele frequencies
within a population
p^2 + 2pq + q^2 = 1
p + q = 1
Effects of
stabilising
selection
the middle (median) trait has a
selective advantage and
continues to be the most
frequent in the population
range decreases as the extreme
traits are lost over time
Effects of
disruptive
selection
alleles for the extreme traits
and the middling trait allele
become less frequent
leads to speciation
Selective
advantage
ndividuals with alleles that
make them more likely to
survive in that environment
What creates
genetic
variation?
mutations
crossing over in meiosis
independent segregation in
meiosis
random fertilisation of gametes
Why is genetic drift
important in small
populations?
the impact of allele frequency
changes has a bigger impact
proportionally
results in evolution occurring
more rapidly
Assumptions of the
Hardy-Weinberg
principle
There will be no change in the
allele frequency between
generations within a population
e.g. no deaths, births or
migration
Assumptions of
mark-releaserecapture
the marked individuals released
distribute evenly after being
released
no migration
no births or deaths
Evolution
a change in allele frequencies in
populations
over many generations
Effects of
directional
selection
one of the extreme traits has a
selective advantage
occurs when there is a change
in the environment
the modal trait changes
How would you
randomly sample?
place two tape measures at
right angles to create a gridded
area
use a random number generator
to get coordinates
place the quadrate at the
coordinates and collect the data
repeat at least 30 times
How would you
sample using a
line transect?
Place a tape measure at a right
angle to the
road/river/shoreline
place quadrat every set
distance meters (e.g. 5 metres)
collect the data in each quadrat
repeat placing the tape
measure in parallel 30 times
What is the formula to
calculate population
size with mark-releaserecapture?
estimated total population = no. organisms initially caught X nu. organisms in second sample / no. of marked rganisms recaptured
Describe the markrelease-recapture
method of sampling
an initial sample of the
population is captured
individuals are marked and
released
allow them time to randomly
disperse
a second sample is captured
the total number captured in
the second sample and the
number recaptured with the
marking are recorded
describe the changes you would see in a succession
abiotic factors become less hostile
biodiversity increases
becomes more stable
