GENETIC DIVERSITY - meoisiis + adaption

Question 1

gene mutation

Answer 1

change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide
occur continuously
sometimes lead to a change in the polypeptide that the gene codes for

Question 2

genetic code being degenerate

Answer 2

Most mutations do not alter the polypeptide or only alter it slightly so that its structure or function is not changed

Question 3

different ways that a mutation in the DNA base sequence can occur:

Answer 3

Deletion of nucleotides
Substitution of nucleotides

Question 4

deletion of nucleotides

Answer 4

when a nucleotide s randomly deleted from the DNA sequence
changes the amino acid that would have been coded for
changing the groups of three bases further on in the DNA sequence
may dramatically change the amino acid sequence produced therefore the ability of the polypeptide to function

Question 5

types of Substitution of nucleotides

Answer 5

Silent mutations
Missense mutation
Nonsense mutations

Question 6

what is subtstitution

Answer 6

a base in the DNA sequence is randomly swapped for a different base
only change the amino acid for the triplet
not have a knock-on effect

Question 7

silent mutations

Answer 7

does not alter the amino acid sequence of the polypeptide (this is because certain codons may code for the same amino acid as the genetic code is degenerate)

Question 8

Missense mutations

Answer 8

mutation alters a single amino acid in the polypeptide chain (sickle cell anaemia is an example of a disease caused by a single substitution mutation changing a single amino acid in the sequence)

Question 9

Nonsense mutations

Answer 9

the mutation creates a premature stop codon (signal for the cell to stop translation of the mRNA molecule into an amino acid sequence), causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function (cystic fibrosis is an example of a disease caused by a nonsense mutation, although this is not always the only cause)

Question 10

effect of gene mutations on polypeptides

Answer 10

Most mutations do not alter the polypeptide or only alter it slightly so that its appearance or function is not changed
However, a small number of mutations code for a significantly altered polypeptide with a different shape
This may affect the ability of the protein to perform its function.

Question 11

affecting the ability of the protein to perform its function. For example:

Answer 11

If the shape of the active site on an enzyme changes, the substrate may no longer be able to bind to the active site
A structural protein (like collagen) may lose its strength if its shape changes

Question 12

mutagnic agent

Answer 12

environmental factors that increase the mutation rate of cells
Examples include:
High-energy radiation such as UV light
Ionising radiation such as X rays
Toxic chemicals such as peroxides

Question 13

Non-disjunction

Answer 13

occurs when chromosomes fail to separate during meiosis
This occurs spontaneously
gametes may end up with one extra copy of a particular chromosome or no copies of a particular chromosome
If the abnormal gametes take part in fertilization, then a chromosome mutation occurs as the diploid cell will have the incorrect number of chromosomes
Chromosome mutations involve a change in the number of chromosomes

Question 14

Meiosis produces daughter cells that are genetically different from each other and to the parent cell
This is due to the processes of

Answer 14

crossing over
Independent assortment

Question 15

independent assortmant

Answer 15

production of different combinations of alleles in daughter cells due to the random alignment of homologous pairs along the equator of the spindle during metaphase
different combinations of chromosomes in daughter cells increases genetic variation between gametes
ach pair can be arranged with either chromosome on top, this is completely random
The orientation of one homologous pair is independent / unaffected by the orientation of any other pair

Question 16

crossing over

Answer 16

The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that its alleles are exchanged

Question 17

process of crossing ovrt

Answer 17

During meiosis I homologous chromosomes pair up and are in very close proximity to each other
The non-sister chromatids can cross over and get entangled
These crossing points are called chiasmata
The entanglement places stress on the DNA molecules
As a result of this a section of chromatid from one chromosome may break and rejoin with the chromatid from the other chromosome
can result in a new combination of alleles on the two chromosomes

Question 18

The different combinations of chromosomes following meiosis

Answer 18

The number of possible chromosomal combinations resulting from meiosis is equal to 2n
n is the number of homologous chromosome pairs

Question 19

The different combinations of chromosomes following fertilisation

Answer 19

In random fertilisation, any two gametes may combine
Therefore the formula to calculate the number of combinations of chromosomes after the random fertilisation of two gametes is (2n)2
n is the haploid number and 2 is the number of gametes
This explains why relatives can differ so much from each other. Even with the same parents, individuals can be genetically distinct due to variation at the meiosis and fertilisation stage (as well as other possible mutations and crossing-over)

Question 20

DIFFERENCES OF THE PROCESSES OF MITOSIS AND MESOISIS

Answer 20

Mitosis contributes to the growth of an organism or to replace dead/dying cells
Meiosis produces genetically different gametes for sexual reproduction

Question 21

The Different Outcomes of Mitosis and Meiosis

Answer 21

Number of daughter cells
Mitosis = 2
Meiosis = 4
Mitosis = 2n
Meiosis = n

Question 22

what mitosis ends u wirh

Answer 22

two daughter cells genetically identical to each other and the parent cell
This is important so that growth and cell replacement can occur within a body continually
Every cell in an organism’s body (other than gametes) contain exactly the same genetic material

Question 23

what mesoiss eds up with

Answer 23

four daughter cells all of which contain half the genetic material of the parent cell and are all different from each other and the parent
This is important for genetic variation within families and the population
Genetic variation can reduce the risk of inheriting genetic diseases

Question 24

genetic variation

Answer 24

The small differences in DNA base sequences between individual organisms within a species population

Question 25

what results in genetic diversity

Answer 25

Genetic variation is transferred from one generation to the next and it results in genetic diversity within a species population is the number of different alleles of genes in a population

Question 26

what does mutation reuslt in

Answer 26

the generation of new alleles and contributes to genetic diversity or the size of the gene pool new allele may be advantageous,disadvantageous or have no apparent effect on phenotype

Question 27

new alleles

Answer 27

The new allele may be advantageous, disadvantageous or have no apparent effect on phenotype (due to the fact that the genetic code is degenerate New alleles are not always seen in the individual that they first occur in They can remain hidden (not expressed) within a population for several generations before they contribute to phenotypic variation

Question 28

effect of genetic diversity

Answer 28

There needs to be some level of genetic diversity within a population for natural selection to occur Differences in the alleles possessed by individuals within a population result in differences in phenotypes Environmental factors affect the chance of survival of an organism; they, therefore, act as a selection pressure increase the chance of individuals with a specific phenotype surviving and reproducing over others

Question 29

f a population has a small gene pool

Answer 29

low genetic diversity then they are much less able to adapt to changes in the environment and so can become vulnerable to extinction

Question 30

Principles of Natural Selection

Answer 30

Random mutation can produce new alleles of a gene Many mutations are harmful or neutral but, under certain environmental conditions, the new alleles may benefit their possessor, leading to an increased chance of survival and increased reproductive success The advantageous allele is passed onto the next generation As a result, over several generations, the new allele will increase in frequency in the population

Question 31

Example of Natural selection in Rabbits

Answer 31

Variation in fur colour exists within rabbit populations At a single gene locus, normal brown fur is produced by a dominant allele whereas white fur is produced by a recessive allele in a homozygous individual Rabbits have natural predators like foxes which act as a selection pressure Rabbits with a white coat do not camouflage as well as rabbits with brown fur, meaning predators are more likely to see white rabbits when hunting As a result, rabbits with white fur are less likely to survive than rabbits with brown fur Therefore, the rabbits with brown fur have a selection advantage, so they are more likely to survive to reproductive age and be able to pass on their alleles to their offspring Over many generations, the frequency of alleles for brown fur will increase and the frequency of alleles for white fur will decrease

Question 32

Natural selection causes

Answer 32

a change in allele frequencies over time Selection pressures (caused by the environment an organism is in) increase the likelihood that certain individuals with specific alleles survive to reproductive age, enabling them to pass on their alleles to their offspring

Question 33

community

Answer 33

Multiple populations (of different species) living and interacting in the same area

Question 34

Ecosystems

Answer 34

Communities interact with the non-living components of the environment they live in, forming ecosystems The interaction between a community (the living, biotic part) and the non-living (abiotic) parts of the environment

Question 35

Niche

Answer 35

The place where a species lives within an ecosystem is its habitat The role that a species plays within its habitat is known as its niche biotic interactions abiotic interactions

Question 36

how many species can a niche be occupied by

Answer 36

only be occupied by one species, meaning that every individual species has its own unique niche

Question 37

what happens when two species occupy a niche

Answer 37

they will compete with each other for the same resources One of the species will be more successful and out-compete the other species until only one species is left and the other is either forced to occupy a new, slightly different niche or to go extinct from the habitat or ecosystem altogether

Question 38

Adaptations to abiotic and biotic conditions

Answer 38

Adaptations are features of organisms that increase their changes of surviving and reproducing. These adaptations can be: Anatomical (e.g. structural features such as horns, claws or feathers) Behavioural (e.g. courtship of defensive behaviours) Physiological (e.g. processes inside the body such as venom production or the ability to digest cellulose)

Question 39

The Effect of Abiotic Factors on Biodiversity

Answer 39

The changes that species produce in their abiotic environment can actually result in a less hostile environment As a result, this can change or sometimes increase the biodiversity within that environment

Question 40

maximum stable population size

Answer 40

that an ecosystem can support is known as the carrying capacity

Question 41

Abiotic factors affecting population size

Answer 41

Abiotic factors involve the non-living parts of an ecosystem Some examples of abiotic factors that can limit population size include: light availability water supply temperature amount of space available soil pH

Question 42

if the temperature of their surroundings is significantly lower or higher than the optimum body temperature for that species

Answer 42

individuals will have to use up a significant amount of energy to maintain their optimum body temperature (via homeostasis) As each individual now has less energy available for growth and reproduction, fewer individuals reach reproductive age and successfully reproduce, meaning that population growth is limited

Question 43

Biotic factors affecting population size

Answer 43

Biotic factors involve the living parts of an ecosystem Biotic factors are the interactions between organisms This includes things like competition for resources and predation

Question 44

Biotic factors can be split into three main types:

Answer 44

Interspecific competition Intraspecific competition Predation

Question 45

Interspecific competition

Answer 45

ompetition for the same resources between individuals from different species competition between species means that the sizes of both populations are limited competition between species can lead to a decrease in the population size of one of the species and an increase in the population size of the other

Question 46

Intraspecific competition

Answer 46

This is competition for the same resources between individuals from the same species

Question 47

Example of infra specific competition

Answer 47

When resources are plentiful, the population of grey squirrels increases As the population increases, however, there are more individuals competing for these resources (e.g. food and shelter) At some point, the resources become limiting and the population can no longer grow in size - the carrying capacity has been reached

Question 48

Predation

Answer 48

Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers who are themselves eaten by tertiary consumers Consumers that kill and eat other animals are known as predators

Question 49

Predator prey cycle

Answer 49

The number of predators increases as there is more prey available The number of prey then decreases as there are now more predators The number of predators decreases as there is now less prey available The number of prey increases as there are now fewer predators The cycle now repeats

Question 50

What is sampling

Answer 50

Sampling is a method of investigating the abundance and distribution of species and populations

Question 51

are two different types of sampling:

Answer 51

Random Systematic

Question 52

In random sampling

Answer 52

the positions of the sampling points are completely random or due to chance This method is beneficial because it means there will be no bias by the person that is carrying out the sampling that may affect the results

Question 53

Systematic sampling

Answer 53

the positions of the sampling points are chosen by the person carrying out the sampling There is a possibility that the person choosing could show bias towards or against certain areas Individuals may deliberately place the quadrats in areas with the least species as these will be easier and quicker to count This is unrepresentative of the whole area

Question 54

Sampling methods

Answer 54

Quadrats Transects Mark-release-recaptur

Question 55

Frame quadrats

Answer 55

Quadrats must be laid randomly in the area to avoid sampling bias This random sampling can be done by converting the sampling area into a grid format and labelling each square on the grid with a number Then a random number generator is used to pick the sample points Once the quadrat has been laid on the chosen sample point the abundance of all the different species present can be recorded

Question 56

Why use transects

Answer 56

can help show how the distribution or abundance of a species changes with the different physical conditions in the area A transect is a line represented by a measuring tape, along which samples are taken

Question 57

For a belt transect

Answer 57

Place quadrats at regular intervals along the tape and record the abundance of each species within each quadrat This produces quantitative data

Question 58

Mark release and capture

Answer 58

The first large sample is taken. As many individuals as possible are caught, counted and marked in a way that won’t affect their survival e.g. if studying a species of beetle, a small amount of brightly coloured non-toxic paint can be applied to their carapace (shell) The marked individuals are returned to their habitat and allowed to randomly mix with the rest of the population When a sufficient amount of time has passed another large sample is captured The number of marked and unmarked individuals within the sample are counted The proportion of marked to unmarked individuals is used to calculate an estimate of the population size

Question 59

Belt transects equation

Answer 59

N = (n1 × n2) ÷ m2 N = population estimate n1 = number of marked individuals released n2 = number of individuals in the second sample (marked and unmarked) m2 = number of marked individuals in the second sample

Question 60

Assumptions from mar release capture

Answer 60

marked individuals are given sufficient time to disperse and mix back in fully with the main population The marking doesn't affect the survival rates of the marked individuals (e.g. doesn't make them more visible and therefore more likely to be predated) The marking remains visible throughout the sampling and doesn't rub off The population stays the same size during the study period (i.e. there are no significant changes in population size due to births, deaths or migrations into or out of the main population)

Question 61

Ecosystem

Answer 61

A relatively self-contained unit consisting of a community (or multiple communities) of species interacting with each other and with the non-living components of their environment There are both living (biotic) and non-living (abiotic) components within an ecosystem

Question 62

succession

Answer 62

ecosystems change from being very simple to being relatively complex Stages where new species colonise an area and change the environment May make the encvironment less suitable for existing species and more suitable for others with different adaptions

Question 63

Primary succession

Answer 63

when newly formed or newly exposed land (with no species present) is gradually colonised (inhabited) by an increasing number of species This new uninhabited land can be created in several ways.

Question 64

How new uninhabitable land can be created

Answer 64

The magma from erupting volcanoes cools and often leads to the formation of new rock surfaces or even new rocky islands in the sea Another way new land can be exposed is by sea-level dropping or the drying up of a lake, leaving areas of bare rock

Question 65

Sand dunes primary succession

Answer 65

coastal areas (marram grasses are the pioneer species in these environments as they have deep roots to access water that other plants can't reach and are able to tolerate the salty environment i.e. the high concentrations of sodium and calcium ions caused by sea spray)

Question 66

prey

Answer 66

Consumers that kill and eat other animals are known as predators, and those eaten are known as prey

Question 67

Primary Succession Occurs in a Series of Stages

Answer 67

Firstly, seeds and spores that are carried by the wind land on the exposed rock and begin to grow pioneer species die and decompose, the dead organic matter (humus) forms a basic soil Seeds of small plants and grasses land on this basic soil and begin to grow these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich Larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil, can now begin to grow soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees These final species to colonise the new land become the dominant species of the now relatively complex ecosystem The final community formed, containing all the different plant and animal species that have now colonised the new land, is known as the climax community

Question 68

Examples of a Changing Environment During Succession

Answer 68

Pioneer species that first colonise and grow on the bare rock, such as lichens, help to slowly break apart the top surface of the rock. As pioneernspecies die and decompose humus builds up. In this way, the lichens gradually change the local environment so that it becomes more suitable for other species, such as mosses. This cast shades to stop further growth of lichens . Their roots are longer and so further break up the rock. Organic matter increases as these bigger plants die more water retained so grasses shrubs and more flowering plants grownEventually, these species result in the formation of a thin soil layer that covers the newly formed rock surface completely. As lichens cannot grow on soil, they now disappear from the ecosystem. Finally, as the soil deepens further and trees are able to grow, they may then out-compete certain shrubs and other smaller plant species, which may no longer be able to grow beneath the trees due to a lack of light Eventually the area colonised by dominant plant species and a stable climax community is reached.

Question 69

what interrupts process of succession

Answer 69

Human activities stops a climax community from developing

Question 70

what interrupts process of succession examples

Answer 70

If left alone, a grassy field would eventually develop into an area of shrubs and trees due to the process of succession. However, regular mowing prevents these larger, more woody plants from establishing themselves, so succession can't occur (only the small grasses can survive being regularly mowed) Similarly, in areas where livestock such as sheep, horses or cattle are kept, succession is halted by the grazing activity of these animals, which eat any new plant shoots trying to grow. Again, grasses are the main plant species that can remain established in these areas

Question 71

Managing Succession

Answer 71

the protection and management of ecosystems

Question 72

Preventing Succession

Answer 72

Grazing animals can be introduced temporarily. Managed burning can be used, during which controlled fires are deliberately lit and allowed to burn away the shrubs and trees.

Question 73

burning fires

Answer 73

. Species such as heather (a key moorland plant) grow back quickly in their place. This resets the process of succession, meaning the larger, woody plants will take a long time to grow back, at which point the burning can be repeated

Question 74

Grazing animals

Answer 74

they eat the growing shoots of shrubs and trees, this stops these plants from establishing themselves and prevents succession

Question 75

Methods of Conservation

Answer 75

National parks- several restrictions Humans access is strictly controlled Industrial activities such as agriculture and building are tightly regulated Hunting is limited or completely prohibited Marine parks-also have restrictions to prevent overfishing and pollution Public engagement-Some of the profits made from parks can be used to improve the health and education standards in the nearby communities to illustrate the benefits of having such areas nearby

Question 76

Conservation in Captivity

Answer 76

Zoos can also contribute towards the conservation of endangered animal species Captive breeding programmes can breed individuals of a species so their offspring can be released into the wild

Question 77

problems with zoos

Answer 77

Captive breeding of small species populations can reduce genetic diversity Certain animal species will not breed in captivity Not all zoos can provide adequate habitats for animals with specific needs

Question 78

Botanic gardens

Answer 78

cuttings and seeds collected from the wild to establish a population of the endangered species in captivity

Question 79

Frozen zoos

Answer 79

Storing Genetic Material for Conservation deally, samples are collected from different individuals of the same species to maintain the gene pool The temperature used is roughly -196oC A large amount of genetic material can be stored in a relatively small space In the future genetic materials from extinct animal species could be used to breed and reintroduce a species through IVF and genetic engineering

Question 80

seed bank

Answer 80

conserves plant diversity by drying and storing seeds in a temperature-controlled environment Usually, seeds of the same species are collected from different sites to maintain the gene pool If the plant species goes extinct then the seeds can be used to grow them again Seeds can only be stored for so long. After a certain period of time, the stored seeds are grown into plants and fresh seeds for storage are taken from those plants

Question 81

Secondary succession

Answer 81

Event that disrupts the community but soil structure remains in plants

Question 82

Typical colonisers

Answer 82

Large quantities of wind dispersed seeds Rapid termination Photosyytetic Fix nitrogen Tolerate extreme conditions