genetic diversity and adaptation Flashcards
why are there 7.3 billion people alive but they all look different
genetic diversity
what is the cause of genetic diversity
DNA determines the considerable variety of proteins that make up each organism
Therefore genetic similarities and differences between organisms may be defined in terms of variation in DNA
- therefore, DNA leads to genetic diversity
what do members of species have in common
a section of DNA that codes for one polypeptide is called a gene
members of the same species have the same genes
e.g. all humans have a gene for blood group and how all snapdragons have a gene for petal colour
how do organisms differ in phenotype -appearance
e.g. blood group in humans depends on which two alleles human possess - similar to what colour a snapdragon depends on
Therefore organisms of the same species differ in their combination of alleles, not their genes
what is gene diversity described as
it is described as the total number of alleles in a population
what is a population
a population is a group of individuals of the same species that live in the same place and can interbreed
how many populations do a species consist of
a species consists of one, or more populations
what determines how great the genetic diversity of a species is
the greater the number of different alleles that all species possess, the greater the genetic diversity if that species
what reduces genetic diversity
genetic diversity can be reduced when a species has fewer different alleles
why is having greater genetic diversity an advantage for a species/population
greater GD, the more likely that some individuals in a population will survive and environmental change
this is because of a wider range of alleles and therefore a wider range of characteristics
This gives a greater probability that some individual will possess a characteristic that suits it to the new environmental conditions
what is genetic diversity a factor of
natural selection
why do certain alleles get passed on to the next generation
not all alleles of a population are equally likely to be passed to the next generation
This is because only certain individuals are reproductively successful and so pass on their alleles
what affects the frequency of different alleles in a population
difference between the reproductive success of individuals affects alleles frequency in a population
how do alleles get passed down to the next generation
- within any population of a species, there will be a gene pool containing a wide variety of alleles
- random mutation of alleles within this gene pool may result in a new allele of a gene which in most cases will be harmful
- however, in certain environments, the allele of a gene might give its possessor and advantage in their competition with others
- these individuals will be better adapted and therefore more likely to survive in their competition with others
- These individuals are more likely to obtain the available resources ad so grow more rapidly and live longer. As a result, they will have a better chance of breeding successfully and producing more offspring
- only these individuals that produce successfully will pass on their alleles to the next generation
- therefore is the new allele that gave the parents an advantage in the completion for survival that is most likely to be passed on to the next generation
- as the new individual also have the new “advantageous” allele, they turn are more likely to survive and reproduce successfully
what happens to the less advantageous alleles in the population
over many generations, the number of individuals with the new “advantageous” allele will increase at the expense of the individuals with the “less advantageous” alleles
overtime, the frequency of the new alleles in the population will increase and the old alleles decrease
what does it mean when we say advantageous alleles
what is “advantageous” depend upon th environment conditions at any one time
e.g. alleles for black body colour may be “advantageous” as camouflage against a smoke-blackened wall but non- advantageous against a snowy landscape
what is selection
selection is the process by which organisms that are better adapted to their environment tend to survive and breed while those that are less adapted tend not to
what does selection depend on
different environmental conditions favour different characteristics in the population
- depending on which characteristics are favoured selection will produce a number of different results
what may selection favour
selection may favour:
- individuals that vary in one direction from the mean of the population
This is called DIRECTIONAL SELCTIONand changes the characteristic of the population
-average individuals.
This is called STABILISING SELECTION and preserved the characteristics of a population
what are characteristics influenced by
- more than one gene (polygenes)
these types of characteristics are influenced by the environment more than one determined by a gene
what are the effects of the environment on polygenes
the effect of the environment on polygenes produces individuals in a population that vary about the mean
when you plot this variation on a graph you get a normal distribution
what is directional selection
if environmental conditions change, the phenotypes that are best suited to the new conditions are most likely to survive
some individuals, which fall to either the left or right of the mean will possess a phenotype more suited to the new conditions
- these individuals will be more likely to survive and breed. They will, therefore contribute offspring and pass the alleles they possess to the next generation
over time the mean will then move in the dirc=ection of these individuals
what is an example of directional selection
antibiotic resistance in bacteria
e.g.
shortly after the discovery of antibiotics, t became apparent that the effectiveness of some antibiotics at killing bacteria reduced
It was fount that these populations of bacteria had developed resistance to antibiotics such as penicillin
It was found that these populations of bacteria had developed resistance to antibiotics such as penicillin
what was the resistance of the bacteria to antibiotics due too
the resistance was not due to the development of tolerance to the antibiotic, but rather a chance mutation within the bacteria
looking at bacterias resistance to antibiotics in more detail
- SPONTANEOUS mutation occurred in the allele of a gene in a bacterium that enabled it to make a NEW PROTEIN which before it was able to kill the bacteria
- the bacterium happened, by chance, to be in a situation where penicillin was being used to treat and individual.
In these circumstances, the mutation gave the bacterium the advantage of being able to use penicillinase to break down the antibiotic and so survive while the rest of the bacteria population died - bacterium that survived was able to divide by binary fission to build up a small population of penicillin-resistant bacteria
- members of this small penicillin-resistant population were more able to survive and therefore multiply, in the presence of penicillin than members of the non - resistant population
- lead to an increase in the frequency of the allele that enables the production of the penicillinase
what is a common misconception about bacteria resistance
bacteria do not mutate because of the presence of antibiotics
- mutation occurs randomly and are very rare
however as there are so many bacteria around the total number of mutation is large
what is stabilising selection
if environmental conditions remain stable itis the individuals with the phenotype closest to the mean that are favoured
individuals are more likely to pass their alleles on to the next generation
These individuals with phenotypes at the extremes are less likely to pass on their alleles
Stabilising selection, therefore, tends to eliminate the phenotype at the extreme
how do you know if a population underwent stabilising selection
the population’s characteristics are preserved rather than changed
- stabilising selection, therefore, results in phenotypes around the mean of the population being selected for and those both extremes being selected against
what does natural selection result in
natural selection results in species that are better adapted to the environment that they live in: survive
these adaptions may be:
- anotomical
- physiological
- behavioural
what are anatomical adaptations
such as shorter ears and thicker fur in artic foxes compared to foxes in warmer climates
what are physiological adaptions
oxidising of fat rather than carbohydrate on kangaroo rats to produce additional water in a dry desert environment
what are behavioural adaptions
such as the autumn migration of swallows from the UK to Africa to avoid food shortages in the UK winter
how many living organisms are there
around 18 million different living organisms
how many species are there
estimates for the total number of species on earth range from 10 million to 100 million
- this figure is more likely to be 14 million
what is classification
classification is the organisation of living organisms into groups
This process is not random but is based on a number of accepted principles
how do scientists distinguish between one type of organism from another
at one time, scientists often gave new organism a name that described their features
e.g.
blackbird, rainbow trout e.t.c
This resulted in the same name being used in different parts of the world for very different species
Therefore, it was difficult for scientists to be sure which organisms they were referring to the same organism
Swedish botanist Linnaeus overcame this problem by devising a common system of naming organisms - system is still used today
what was the system that Linnaeus devise
it was called the binomial system- this is because it is identified by two names
what are the features of the binomial system
it features are as follows:
First name
- which is the generic name, it denoted the genes to which the organism belongs
This is equivalent to the surname used o identify people and shared by their close relatives
Second name
- specific name, denotes the species to which the organism belongs
Equivalent to the first name/ given name used to identify people -
However, its name is never shared by other species within the genus
what are the rules required for the binomial system
- names are printed in italic/ if handwritten, they are underlined to indicate that they are scientific names
the first letter of the generic name is in UPPER CASE but the specific name is in lower case
If a specific name is not known, it can be written as “sp”
are the names of organisms constant
naming organisms are in a constant state of change
current names reflect the present state of scientific knowledge and understanding
-classification of species is regularly changing as our knowledge of their evolution, physical features biochemistry and behaviour increases
how do members of their own species distinguish themselves
members of the same species have similar/ similar same genes and therefore resembles one another physically and biochemically
- same is true for behaviour
this helps them to distinguish members of their own species from those of other species
Therefore individuals can recognise members of species by the way they look and behave
what is courtship behaviour
the ability to display a behaviour is genetically determined
It too has evolved and it influences the chances of survival
courtship behaviour has therefore evolved to allow species to mate and reproduce
why is reproduction important
no individuals live forever
so reproduction is therefore the means by which a species can survive over time
Each individual has adaptions that help to ensure that their DNA is passed on, through the reproductive process, to the next generation
why is it important for mating to be successful
females of species only produce eggs of specific time (often as little as once a year)
Therefore it is important to ensure that mating is successful and that offspring have the maximal chance of survival
what does courtship behaviour do in order to make sure mating is successful
courtship helps to achieve this by enabling individuals to:
- recognise members of their own species to ensure that mating only takes place between members of the same species because only members of the same species can produce fertile offspring
- identify a mate capable of breeding because both partners need to be sexually mature, fertile and receptive to mating
- form a pair bond that will lead to successful mating and raising offspring
- synchronising mating and raising of offspring
- synchronising mating so that it takes place when there is the maximum probability of the sperm and egg meeting
why are females of many species receptive to mating for a period of time
females of many species undergo a cycle of sexual activity in which they can only conceive during a very short time
therefore they are receptive to mating for a period around the time they produce eggs
Therefore courtship behaviour is used by males to determine whether the female is at this receptive stage
what happens when the females of a species respond to courtship behaviour
if she responds with the appropriate behavioural response, courtship continues
- the likely result is the production of offspring
what happens if the females of a species do not respond to the courtship behaviour
if the behaviour is not receptive and the females exhibit a different pattern of behaviour, the males cease to court her and urns there attention elsewhere
how do individuals know they are the same species
during courtship, animals use signals to communicate with potential a potential mate and with numbers of their own sex
typically there is a chain of actions between a male and female
- this chain of behaviour is the same for all members of a species but differs for members of other species
In this way, both the individuals recognise their partner of the same species and they may be prepared to mate
why is it important to group species
with so many species past and present, it makes sense to organise them into manageable groups
what is classification
the grouping of organisms is known as classification
what is taxonomy
the theory and practice of biological classification is called taxonomy
what are the 2 main biological classification
artificial classification divides organisms according to differences that are useful at the time
e. g.
1. colour
2. size
3. number of legs
these are described as analogous characteristics where they have the same function but do not have the same evolutionary origins
e.g.the way of butterflies and birds are both used for flight however they originated in very different ways
phylogentic classification
what is phylogenetic classification
a) it is based upon the evolutionary relationships between organisms and their ancestors
b) classifies species into groups using features derived from their ancestors
c) arranges the groups into a hierarchy in which groups are contained within larger composite groups with no overlap
what are the relationships in a phylogenetic classification partly based on
relationships in a phylogenetic classification are partly based on homologous characteristics
Homologous characteristic have similar evolutionary origins regardless of their functions in the adult of a species
e.g. the wing of a bird, the arm of a human and front legs of a horse all have the same basic structure and evolutionary orgins and therefore homologous
what are taxons
each group within a phylogenetic biological classification is called taxon (plural taxa)
taxonomy is the study of these groups
what is the study of these groups
taxonomy is the study of these groups and their positions in a hierarchal order, where they are now as taxonomic ranks
what are the taxonomic ranks based on
taxonomic ranks are based upon the evolutionary line of descent of the group members
what is the highest taxonomic rank
the highest taxonomic rank is the DOMAIN
what are the three different domains identified
bacteria
eukarya
archae ) a group of prokaryotes)
what are bacteria
are a group of single - celled prokaryotes with the following features
- absence of membrane -bounded organelles such as nuclei or mitochondria
- unicellular, although cells may occur in chains or clusters
- ribosomes are smaller (70s) than in eukaryotic cells
- cell walls are present and made of murein (but never chitin/ cellulose)
- single loop of naked DNA made up of nucleic acids but no histones
what are archaea
group of single - celled organisms originally classified as bacteria which they resemble in appearance
they differ from bacteria:
- their genes and protein synthesis are more similar to eukaryotes
- their membranes contain fatty acid chains attached to glycerol by ester linkages
- there is no murein in their cell walls
- they have a more complex form of RNA polymerase
what are eukarya
are a group of organisms made up of one or more eukaryotic cells
features are:
- their cells possess membrane-bounded organelles such as mitochondria
- they have membranes containing fatty acid chain attached to glycerol by ester linkages
- not al possess cells with a cell wall, but where they do it contains no murein
- ribosomes are larger (80s) than in bacteria and Archaea
what are the four kingdoms that eukarya is split into
- fungi
- plantae
- animalia
what is the largest group known as in each kingdom
within each kingdom the largest groups known as phyla
what is the diversity within the phylum divided into
diversity within each phylum allows it to be divided
what is each class divided into
each class is divided into families and at this level, the differences are less obvious
what is each family divided into
it is divided into genera
what is each genus divided into
species
KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES
what is the hierarchical order of taxonomic ranks based upon
the supposed evolutionary line of descent of the group members
what is phylogeny
the evolutionary relationship between organisms is known as phylongeny
It is derived from the word “phylum”, which in classification, is a group of related or similar organisms
what does phylogeny of an organism reflect
the phylogeny of an organism reflects the evolutionary branch that led up to it
The phylogenetic relationships of different species are usually represented by a tree-like diagram called a phylogenetic tree
what are the three components of biodiversity
species diversity - refers to the number of different species and the number of individuals of each species within any one community
genetic diversity - refers to the variety of genes possessed by individuals that make up a population of a species
ecosystem diversity - refers to the range of different habitats, from a small local habitat to the whole of the earth
how do we measure species diversity
one measure of species diversity is species richness
This is the number of different species in a particular area at a given time (community)
e.g. two communities may have the same number of species by the proportions of the community made up of each species may differ markedly
how else can we measure species diversity
by calculating the index of diversity
how do we calculate the index diversity
d= N(N-1) /Σn(n-1)
d=index of diversity
N= total number of organisms of all species
n =total number of organisms of each species
Σ = the sum of
a worked example of using the index of diversity
use the index to calculate the species diversity of the habitats
You must first calculate n(n-1) for each species in each habitat
You can then calculate the sum of n(n-1) for each species
You can now calculate the species diversity index for each habitat
what does a higher value of d mean
the higher the value of d, the greater is the species diversity
so, even though the total number of species and the total number of individuals are the same in both habitats, thee species diversity of habitats X is much greater
what has happened to classification systems as science has developed
as science has developed it has become possible too use a wider range of evidence to determine relationships between organisms
what are the changes that happens to organisms when they evolve
when organisms evolve not only their internal and external features that change, but also the molecules of which they are made
what determines the changes in the organisms when they evolve
DNA determines the proteins of an organism
It follows that changes in the features of a species are due to changes in its DNA
Comparing the genetic diversity within, and between species helps scientists to determine the evolutionary relationship
what are the different ways that scientists can use genetic info to compare evolutionary relationships between organisms
comparison of DNA base sequences
comparison of the base sequence of mRNA
comparisons of amino acid sequences in proteins
comparison of observable characteristics
what is the traditional way of measuring genetic diversity
by observing the characteristics of organisms
This method is based on the fact that each observable characteristics is determined by a gene or genes (with environmental influences)
what are the limitations of using observable characteristics as a measure of genetic diversity
using observable characteristics has its limitation because a large number of them are coded for by more than one gene
They are polygenetic. This means thy are not discrete from one another but rather vary continuously
It is often difficult to distinguish one from another
Characteristics can also be modified by the environmental Differences may therefore be a result in the different environmental conditions rather than different alleles
e.g. height in humans is determined by a number of genes. However, environmental factors like diet can influence the actual height of an individual
how do we compare DNA base sequences
with the advent of gene technology, we can now read the base sequence of the DNA of any organism
e.g. we can now determine the exact order of nucleotides on DNA
DNA sequencing is now routinely done by automatic machines and the data produced is anlaysed by computers
how do we use a computer to analyse the sequence of DNA
In these computerised systems, each nucleotide base can be tagged with a different coloured fluorescent dye
adenine=green, thymine=red, cytosine=blue,
guanine=yellow
This produces a series of coloured bands, each of which represents one of the four nuclotide bases
how do we use the sequence of base pairings to measure base sequences
we can measure the genetic diversity of a species by sampling hr DNA of its members and sequencing it to produce a pattern of coloured bands
Analysis of these coloured bands.
Analysis of these patterns allows us to compare one species with another or one individual with another of the same species to determine how diverse they are
the process of reading DNA sequences with the human eye is slow - what do scientists do instead
the process would be slow with the human eye and so the patterns are scanned by lasers and interpreted by computer software to give the DNA nucleotide base sequence in a fraction of the time
other than measuring the genetic diversity what else can we use base sequences to determine
we can also use this technique to determine the evolutionary relationships between species
how can the base sequences determine the evolutionary relationships between species
when one species gives rise to another species during evolution, the DNA of the new species will initially be very similar to that of the species that gave rise from it
due to mutations, the sequences of nucleotide bases in the DNA of the new species will change
-consequently, over time, the new species will accumulate more and more differences in its DNA
As a result, we would expect species that are more closely related to show more similarly in their DNA base sequences than species that are more distantly related to show more similarity in their DNA base sequence a than species that are more distantly related
As there are millions of base sequences in every organism, DNA contains a vast amount of information about the genetic diversity and evolutionary history of all organisms
how can comparing the base sequence of mRNA measure genetic diversity
mRNA is coded by DNA
The base sequences on mRNA are complementary to those of the strand of DNA from which they were made
It allows that we can measure DNA diversity, and therefore genetic diversity, by comparing the base sequence of mRNA
how does comparing the amino acids sequences of proteins
the sequence of amino acids in proteins are determined by mRNA which is determined by DNA
Genetic diversity between and within species can therefore be measured by comparing the amino acid sequences of proteins
what does the degree of similarity between the base sequences in species show/mean
the degree if similarity in the amino acid sequence of the same protein in two species will also reflect how closely related the two species are
why has mankind made a considerable impact on the natural world
in our efforts to provide enough food for the human population at a low cost, mankind has had a considerable impact on the natural world
what happens when natural ecosystems develop
as natural ecosystem develop over time, they become complex communities with many individuals of a large number of different species
in other words these communities have a high index of diversity
what are agricultural ecosystems controlled by
agricultural ecosystems are controlled by humans and are different
how are agricultural ecosystems different from natural ecosystems
farmers often select species for particular qualities that make them more productive
As a result of species, and the genetic variety alleles they possess, is reduced to the few that exhibit the desirable features
to be economic the number of these desirable species need to be large
why is the index of species diversity low in agricultural ecosystems
any particular area can only support a certain amount of biomass
If most of the area is taken up by the one species that the farmer considers desirable it follows that there is a smaller area for all the other species - these other species now have to compete for what little space and resources are available
many will not survive this competition- even if the species evolved to adapt to the changes
In addition pesticide are used to exclude these species because they compete with the light,mineral ions, water and food by farmed species
why is food important
food is essential for life, and with an ever - expanding human population there is pressure to produce it more and more intensively
what has happened to the food production in the UK over the last 40yrs
food production has doubled over the past 40 years
how has the increased food production in the UK happened
- it has been achieved by the use of improved genetic varieties of plant and animal species
- greater use of chemical fertilisers and pesticides,
- greater use of biotechnology and changes in farm practices, leading to larger farms and conversion of land supporting natural communities into farmland
these changes have had many ecological impacts
what is the overriding effect of intensive food production
the overriding effect of intensive food production has been to diminish the variety of habitats within ecosystems and consequently reduce species diversity
what are the certain practices that directly removed habitats and reduced species diversity
- removal of hedgerows and grubbing out woodland
- creating monoclutures, e.g. replacing natural meadows with cereal crops or grass for silage
- filling in ponds and draining marsh and other wetland
- over - grazing of land, e.g. upland areas by sheep, thereby preventing regeneration of woodland
what farming practices have a indirect effect on habitats
- use of pesticides and inorganic fertillisers
- escape of effluent from silage and slurry tanks into water courses
- absence of crop rotation and lack of intercropping or undersowing
why have we created a number of management techniques
despite the obvious conflicts between intensive food production and conservation, there are a number of management techniques that can be applied to increase species and habitat diversity, without unduly raising food costs or lowering yields
examples of management techniques
- maintain existing hedgerows at the most beneficial height and shape
An A - shape provides better habitats than a rectangular one - Plant hedges rather than erect fences as field boundaries
- maintain existing ponds and where possible create new ones
- leave wet corners of fields rather than draining them
- plant native trees on the land with a low species diversity rather than in species rich ares
- reduce the use of pesticides - use biological control where possible or genetically modified organisms resistant to pests
- use organic instead of inorganic fertillisers
- use crop rotation that includes a nitrogen - fixing crop, rather than fertiliser to improve soil fertility
- use intercropping rather than herbicides to control to control weeds and other
- create natural meadows and use use hay rather than grasses for stage
- introduce conservation headlands - areas at the edges of field where pesticides are used restrictively so that wild flowers and insects can breed
what effects does the management techniques on the food
these practices will make food slightly more expensive to produce
what does the Department for Environment, Food and Rural Affairs (DEFRA) and The European Union
they encourage farmers with financial incentives
this is because maintaining biodiversity is very important
why is maintaining biodiversity important
if biodiversity is reduced the global living system becomes increasingly unstable and we all rely on the global system for food and other resources
