topic 4B - diversity, classification and variation Flashcards
organisms of the same species will have very similar…
genomes
what always variates between two individuals, even twins?
their DNA base sequences
are the differences of genomes between individuals of the same species large?
the differences are small
genetic variation
the small differences in DNA base sequences between individual organisms within a species
what is genetic variation transferred between & what does it result in?
one generation and the next, resulting in genetic diversity within a species population
define genetic diversity
a high number of different alleles of genes in a population
what does mutation result in?
what does these things do?
new alleles
↳ contribute to genetic diversity
↳ increase the size of the gene pool
3 effects of new alleles:
-advantageous
-disadvantageous
-no effect on phenotype
why do some alleles have no effect on phenotype?
the fact that the genetic code is degenerate
are new alleles always seen in the individual that they first occur in?
no, they can stay hidden within a population for several generations before they contribute to phenotypic variation
what is required in a population for natural selection to occur?
genetic diversity
what causes differences in phenotypes?
generic diversity
(differences in alleles)
environment factors
factors that affect the chance of an organism’s survival
what is a selection pressure?
an environmental factor that influences the survival of an individual as they allow organisms with specific characteristics to survive better than others
the individuals with the favoured phenotypes are described as having…
higher fitness
define the fitness of an organism
its ability to survive and pass on its alleles to offspring
what do organisms with higher fitness have?
adaptations that make them better suited to their environment
which populations can adapt to change?
a population with a large gene pool or high genetic diversity can
small gene pools and adaptations:
-if a population has a small gene pool/ low genetic diversity then they are much less able to adapt to changes in the environment and can become vulnerable to extinction
what is the effect of natural selection on the frequency of alleles in a population
can cause the frequency of alleles in a population to change over time
steps of natural selection:
- an individual of a species mutates
- there is a random environmental change and competition happens
- better adapted individuals survive
- survivors reproduce & pass on their advantageous alleles, increasing the frequency of the allele in the population
- repeated over generations, the ‘mutated’ allele will become the norm
which 3 factors other than selection pressures can affect allele frequencies in a population:
-the founder effect
-genetic drift
-the bottleneck effect
when does the founder effect occur?
when a small number of individuals from a large parent population start a new population
alleles & the founder effect:
only some of the total alleles from the parent population will be present
is it possible to know which alleles end up in the founding population before it is formed?
no, it’s up to chance
what is generic drift?
-when a population is significantly small, chance can affect which alleles get passed onto the next generation
-over time some alleles can be lost or favoured purely by chance
-when there is a gradual change in allele frequencies in a small population due to chance and not natural selection then genetic drift is occurring
when does the bottleneck effect occur?
when a previously large population suffers a dramatic fall in numbers
what usually causes the bottleneck effect?
a major environmental event
the result of the bottleneck effect:
-alleles are lost which reduces the genetic diversity in the population
-the surviving individuals end up breeding and reproducing with close relatives (reduced gene pool)
the 2 types of selection:
-stabilising
-directional
explain stabilising selection:
-natural selection that keeps allele frequencies relatively constant over generations
-things stay as they are unless there is a change in the environment
what does stabilising selection select against?
it selects against extreme phenotypes and selects for the intermediate phenotypes
explain directional selection:
selection pressure that favours a particular phenotype
when does directional selection usually happen?
-when there is a change in environment
-when there is a change in selection pressures
-when a new allele has appeared in the population that is advantageous
natural selection shown through antibiotic (directional)
- random mutation happens in bacteria, nothing happens until antibiotics are used
- the mutation is antibiotic resistance (beneficial allele)
- antibiotics are introduced and the mutated bacteria becomes resistant
- while the other bacteria dies, a point is reached where only resistant bacteria remains and they reproduce, all the population consists of the resistant bacteria
- over generations, this leads to an increase in the frequency of beneficial allele that produces antibiotic resistance
(this is why the course must be completed)
what does directional selection favour?
one extreme phenotype
stabilising selection & human birth weights:
stabilising selection selects against the extreme phenotypes (high and low birth weights) and selects for the intermediate phenotypes (medium birth weights)
how natural selection causes a species to become better adapted to their environment:
over time natural selection will cause favourable allele frequencies to increase and unfavourable allele frequencies to decrease
3 types of adaptations:
-anatomical
-physiological
-behavioural
what are anatomical adaptations?
structural/physical feature
example of an anatomical adaptation:
the white fur of a polar bear provides camouflage in the snow so it has less chance of being detected by prey
what are physiological adaptations?
biological processes within the organism
what are behavioural adaptations?
the way an organism behaves
example of a behavioural adaptation:
cold-blooded reptiles bask in the sun to absorb heat
define evolution
the change in the characteristics of a species over several generations
what will happen if an environment is static?
selection pressures will not change and evolution will not occur
how do adaptations occur? (steps)
1) environment changes or a chance mutation produces a new allele
2) selection pressures favour individuals with advantageous characteristics or with the new allele
3) natural selection allows these individuals with advantageous characteristics/alleles to reproduce
4) those features that are better adapted to the environment become more common
5) whole populations of organisms become better suited to their environment
how can two species be formed from one original population of a species?
two populations of one species are isolated from each other and become so different in phenotype that they can no longer interbreed to produce fertile offspring
speciation
when a group within a species separates from other members of its species and develops its own unique characteristics
what is speciation a result of?
accumulated genetic differences
how do we know that organisms belong to the same species?
they can breed to produce fertile offspring
what is courtship?
behaviour that eventually results in mating and reproduction
why is courtship useful?
-attracts a mate of the same species
-attracts the opposite sex
what is taxonomy?
classifying organisms
what does a phylogenetic classification system do?
arranges species into groups based on their evolutionary origins and relationships
(tells us who’s related to whom and how closely related they are)
what is a hierarchy?
larger groups split into smaller ones, there’s no overlap between groups
what are different groups called? (phylogenetic classification)
each group is called a taxon (plural taxa)
why is grouping organisms into taxons useful?
it can make them easier to understand and remember
what is the highest rank?
dominion
how did scientists realise that prokaryotes could be split into two domains?
-molecular analysis of RNA genes -scientists realised that using cell type to classify organisms is insufficient
what are the three domains?
-archaea (prokaryotes)
-bacteria (prokaryotes)
-eukaryotes
what are organisms within the archaea domain usually called?
extremophile prokaryotes
where were archaea first found?
living in extreme environments
(not all archaea do)
do archaea cells have a nucleus?
no
what were archaea originally classified as?
bacteria
what separates archaea from bacteria?
-unique lipids found in their cell membranes
-no peptidoglycan in their cell walls
-ribosomal structure are more similar to the eukaryotic ribosome than that of the bacteria
what comprises the taxa?
one hierarchy
what are the taxa?
domain, kingdom, phylum, class, order, family, genus and species
how to remember the taxa:
…
what are similar families grouped into?
order
what is a binomial?
the scientific name of a species
what does a binomial consist of?
the organism’s genus and species name in modern latin
why are binomials useful for scientists?
they allow for species to be universally identified
↳ the binomial for a species is the same across the entire globe
what are binomials typed in?
italics
how are binomials handwritten?
they are underlined
what should the genus always begin with when writing binomials?
a capital letter
what should the species always begin with when writing binomials?
a lowercase
using the ____ of species has many limitations and can often lead to the wrong classification of species
physical features
Advances in _____ has allowed scientists to further investigate the evolutionary relationships between species
genome sequencing and immunology
which three types of sequence data are used to investigate evolutionary relationships?
-DNA
-mRNA
-amino acids
what can sequencing technology determine?
the order of DNA bases, mRNA bases and amino acids within an organism’s genome
what is sequencing technology especially useful for?
-comparison with an extinct species (using ancient DNA)
or
-when distinguishing between species that are very physically similar
what will scientists choose for comparison between organisms?
specific proteins or sections of the genome
what will allow for a more accurate estimate of evolutionary relatedness?
looking at multiple proteins or multiple regions of the genome
how can sufficient variation between species be shown?
the protein used needs to be present in a wide range of organisms
which protein is often used to find out evolutionary relatedness?
cytochrome c is often used as it is an integral protein to respiration, which is used by all eukaryotic organisms
rule for all types of sequence data:
the more similar the sequences, the more closely related the species are
two groups of organisms with very similar sequences will have…
separated into separate species more recently than two groups with less similarity in their sequences
species that have been separated for longer have had a greater amount of time to…
accumulate mutations and changes to their DNA,mRNA and amino acid sequences
which protein is often used when comparing organisms using immunological techniques?
albumin
do immunological techniques focus on proteins, DNA or mRNA?
proteins of organisms
method of using albumin (immunological techniques)
1) pure albumin samples are extracted from blood samples of different species
2) each albumin sample is injected into a different rabbit
3) each rabbit produces antibodies for that specific type of albumen
4) the different antibodies are extracted from the different rabbits and are then mixed with the different albumin samples
5) the precipitate (antibody-antigen complexes) resulting from each mixed sample is weighed
examining the results of using albumin (immunological techniques)
-the greater the weight of the precipitate, the greater the relation between the antibody and albumin
define biodiversity
the variety of species & habitats within a particular region
why is biodiversity important for ecosystems?
-makes them more resilient
-allows them to resist changes in the environment
define ecosystem
a community of organisms and their physical environment interacting together
define habitat diversity
the number of different habitats in a specific region
what does it mean if there is a large number of different habitats within an area?
that area has high biodiversity
define niche
all the conditions and resources required for an organism to survive and reproduce
define species diversity
the number of different species in a given community
define community
interacting groups in a common location
which two ways can species diversity be measured?
-species richness
-species diversity
define species richness
number of species within a community
what does species diversity look at?
-the number of different species in a community
-how many organisms are in each species
what does great species diversity entail?
-many different species
-many organisms in each species
scenario with low species diversity:
some ecosystems may have a large number of different species but for some species, there may only be 3 or 4 individuals
advantages of high species diversity
-more stable & resilient to environmental changes
moral & ethical reason for maintaining biodiversity:
humans have a responsibility to reduce their impact on the planet and other species
ecological reason for maintaining biodiversity:
biodiversity increases the stability of ecosystems
environmental reasons for maintaining biodiversity:
organisms provide essential environmental services:
-water cycle
-nutrient cycle
-absorption of carbon dioxide
economic reasons for maintaining biodiversity:
-medicine
-ecotourism
aesthetic reasons for maintaining biodiversity:
humans take pleasure from the visual effects of biodiversity
why can species richness be a misleading indicator of diversity?
it does not take into account the number of individuals of each species
which measure of species diversity do conservationists usually favour?
index of diversity
what is an index of diversity?
a measurement that describes the relationship between the number of species present and how each species contributes to the total number of organisms in that community
index of diversity formula
d = N (N-1) / Σ n (n - 1)
what does a larger result of d mean?
higher level of diversity
what is n? (index of diversity)
total no. of organisms for a single species in the community
what is N? (index of diversity)
total no. of organisms in the community
what is Σ ? (index of diversity)
sum of
calculating the index of diversity: steps
step 1: calculate N(N-1) to find the numerator
step 2: calculate n(n-1) for each species
step 3: add these numbers together to find the denominator
step 4: divide the numerator by the denominator
how did food production change after WW2?
there was a need to produce more food at a quicker rate
↳ farmers needed to produce a higher yield
which modern farming practices began after WW2?
-monoculture
-growing cereal crops rather than vegetables
-fields were made bigger to accommodate machinery
-more land was made arable
-the use of pesticides and fertilizers massively increased
how were fields made bigger? (modern farming)
removing hedgerows and stonewalls
how was more land made arable?
by draining wetland and filling in ponds
are the effects of modern farming on biodiversity positive or negative?
negative
which efforts have conversationists made to try and maintain or improve biodiversity around farmlands?
-they have rewilded areas by removing all human interference and reintroducing native species
-encouraged organic farming
what is essential for raising healthy livestock?
nutritious, fast-growing grass
what provides the highest quality grazing pasture?
a mixture of ryegrass and white clover species
where does the highest quality grazing pasture grow?
on drained, fertilised land
what do farmers do to grow these plant species?
fertilise and drain the land
how does growing these two plant species lower species richness?
-other plant species are outcompeted
OR
-the changes to the land mean it is no longer a suitable habitat for them
what does natural grazing land accommodate?
-a large variety of plant species
-can support a much greater range and number of insect species and bird species
two points in the year when food is plentiful for farmland bird species:
-ploughing of fields
-the harvesting of crops
how does the ploughing of fields benefit farmland birds?
brings invertebrates to the surface
how does the harvesting of crops benefit farmland birds?
-spilt grain from the crops
-seeds from weeds
-invertebrates more accessible by removing their cover
when were crops traditionally sowed & harvested, what did this mean?
sown - spring
harvested - autumn
↳ the gap between harvesting and ploughing was significant
when are crops now sowed & harvested, what does this mean ? (modern farming)
sown - autumn
harvested - summer
↳ the gap between harvesting and ploughing is very short
effect of new ploughing & sowing on farmland birds:
-smaller gap between harvesting and ploughing means there is a very short time when food is plentiful for birds but less time where the soil is redundant for the farmer
-scientists believe that this switch will greatly reduce the diversity of farmland birds in the future
key features of organic farms:
-the use of pesticides and inorganic fertilisers is highly restricted on organic farms
-food produced is free from harmful chemicals
perceived benefits of organic farming on biodive:
benefits biodiversity in and around organic farms
role of bumblebees
pollinate wildflowers and valued crops
why are bumblebees declining?
-bumblebees needs habitats with many
flowering plants to ensure a supply of pollen and nectar all year round
↳ hedgerows, grasslands
-monoculture of crops reduces plant diversity for bumblebee habitats
-pesticides can have a negative effect on bumblebees
is the link between modern farming and bee’s falling numbers confirmed?
no
farming practices that maintain or increase biodiversity can be…
-expensive
-labour intensive
-time-intensive
-reduce the yield of crops and livestock
why is it difficult to balance between conservation and farming?
-if a farmer stops using pesticides on crops, the number of bumblebees will increase but the number of pest species that destroy crops will also increase -reduce crop yield and profit
-the farmer will have to charge more for his produce, in what is a very competitive market
what has the EU set up to encourage farmers to use more environmentally friendly farming techniques?
grant schemes
↳ the money provided by the grants can offset any profit lost due to lower yield
individuals of the same species have similar…
behavioural, structural and physiological features
genetic isolation
-two groups are reproductively isolated from each other
-they do not interchange genes with each other in the production of offspring
-changes that occur in the allele frequencies of each group aren’t shared
-they evolve independently of each other which can lead to the formation of two groups that are no longer successfully able to interbreed
what can be looked at to measure genetic diversity?
-measurable & observable characteristics
-the nucleotide base sequence of DNA
-the nucleotide base sequence of mRNA
-the amino acid sequence of proteins
key facts about using observable & measurable characteristics:
-quickest but least reliable form of determining genetic diversity
-genetic differences between individuals can only be implied
examples of measurable characteristics
-number of legs
-number of petals
examples of observable characteristics
-fur/scales/feathers
-wings/fins
what has replaced using characteristics to determine genetic diversity?
(+ examples)
DNA sequence analysis:
-DNA analysis
-mitochondrial dna
-mRNA
-amino acid
process of DNA analysis (genetic diversity)
-DNA is extracted from the nuclei of cells taken from an organism
-DNA can be extracted from blood or skin samples from living organisms or from fossils
-the extracted DNA is processed, analysed and the base sequence is obtained
what is done with the results of the DNA analysis? (genetic diversity)
the base sequence is compared to that of other organisms to determine evolutionary relationships
the more similarities there are in the DNA base sequence…
the more closely related members of different species are
what can DNA sequence analysis be used to do?
create family trees that show the evolutionary relationships between species
mitochondrial DNA & genetic diversity
-only maternal mitochondrial DNA is present in a zygote
-there is no crossing over in mtDNA, the base sequence can only change by mutation
how has the lack of crossing over in mtDNA helped scientists?
they can research the origins of species, genetic drift and migration events
advantages of mRNA over DNA?
mRNA is often easier to isolate from cells than DNA:
-it is found in the cytoplasm
-there are usually multiple copies of the same mRNA
what is done with mRNA that has been collected?
-used as a template to produce cDNA (complementary DNA)
-the first strand of cDNA produced is complementary to the mRNA (the same as the template strand of the DNA)
-the first strand is then used to produce a second cDNA strand which is the same as the coding strand of DNA
what does the cDNA only contain?
exons
what type of mRNA should be compared between all samples?
mRNA for a known, universal protein
(eg: cytochrome c)
what type of protein sample should be taken from the individuals?
a protein found in all the individuals/species being compared
eg: haemoglobin
how can amino acid sequences be determined from mRNA sequences?
if the ‘frame’ is known (the correct start codon is determined)
disadvantages of using amino acids to deduce relationship between species:
-amino acid sequences of proteins evolve much slower than DNA
closely related species will probably have the same amino acid sequence even though these species split from their common ancestors millions of years ago
