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AH Biology > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

What hazards can occur when working in the field and what control measure can be used to reduce risk?

A

Difficult Terrain- footwear, appropriate equipment
Isolation- means of communication, someone aware of location
Adverse weather conditions- appropriate clothing and footwear
Contact with harmful organisms- appropriate clothing, exit route

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2
Q

How should sampling be carried out?

A

In a way that minimises impact on wild species and habitats.

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3
Q

What type of species should be considered when sampling?

A

Vunrable species and habitats that are protected by legislation.

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4
Q

What are examples of sampling techniques?

A

Point count for birds, transects for plants/slow moving organisms, remote detection for elusive species, capture techniques for mobile species.

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5
Q

How is a point count carried out?

A

A point count involves the observer recording all individuals seen from a fixed point often used to count bird populations.

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6
Q

What is a transect?

A

A transect is a line along which different samples can be taken often set up where the terrain or abiotic factors are measured.

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7
Q

How should quadrants be set up along a transect?

A

Quadrants of suitable shape and size for the area should be set up along the transect.

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8
Q

Which organism are capture techniques used for?

A

Capture techniques such as traps or nets are used for mobile species

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9
Q

What organisms are detected by remote detection?

A

Remote detection is used to detect elusive species.

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10
Q

What are some examples of remote detection methods?

A

Camera traps or scat sampling.

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11
Q

What does the presence, absence or abundance of an indicator species give information about?

A

The presence, absence or abundance gives information about the environmental qualities. (e.g presence of pollutants)

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12
Q

Give an example of an indicator species?

A

Lichen can give information about air quality and sulphur dioxide levels.

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13
Q

What does the absence of an indicator species show?

A

Absence or reduced population of an indicator species shows it is susceptible to some factor in the environment.

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14
Q

What does abundance or increased population of indicators species indicate?

A

Species is favoured by the environmental conditions.

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15
Q

What is mark and recapture used for?

A

To estimate a population size.

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16
Q

What is the equation for mark and recapture?

A

N=MC/R

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17
Q

How is a mark and recapture carried out?

A

A sample of the population is captured, marked and released. After a interval of time, a sample of the same size of population is captured and the number of marked individuals can be used in the equation N=MC/R

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18
Q

What does the mark and recapture method assume?

A

All individuals have an equal chance of capture
There is no immigration or emigration during the sample time
There is no birth and death during the sample time
Individuals that are marked and released can mix fully and randomly with the population.

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19
Q

What methods of marking are there?

A

Banding, tagging, surgical implants, painting, hair clipping.

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20
Q

How is a marking method selected?

A

To minimise impact on the study species and have no effect on behaviour or predictor interaction. The mark however must be clear to permit subsequent observations.

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21
Q

What is ethology?

A

Ethology is the study of animal behaviour.

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22
Q

What measurements can be used to quantify animal behaviour?

A

Latency- The time between the stimulus occurring and the response behaviour.
Frequency- The number of times behaviour occurs within a observation period
Duration- the length of time each behaviour occurs during and observation period

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23
Q

What are ethograms?

A

Ethograms are a method of recording animal behaviours over a set period of time

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24
Q

What is included in a ethogram?

A

Species and species behaviours to be observed and recorded.
The duration of each of the behaviour and the total time of observation.

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25
Q

What does a time budget show?

A

A time budget shows the percentage of time a species spends on each behaviour.

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26
Q

What can a time budget be represented as?

A

A pie chart, tables or charts.

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27
Q

What is anthropomorphism?

A

Anthropomorphism is assigning a human emotion to an animal behaviour and leads to invalid conclusions.

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28
Q

What is evolution?

A

Evolution is the change overtime in the proportion of individual in a population differing in one or more inherited trait.

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29
Q

Where can changes in allele frequency take place during evolution?

A

Sexual selection, natural selection (non random) and genetic drift (random)

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30
Q

How does genetic variation arise during natural selection?

A

As a result if mutation, this is the original source of new sequences of DNA.

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31
Q

Are mutations normally beneficial or harmful?

A

Most mutations are harmful or neutral, but in rare cases they can be beneficial to an individuals fitness.

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32
Q

When does natural selection occur?

A

As organisms produce more offspring than the environment can support, only the best adapted can survive?

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33
Q

How does natural selection occur?

A

Individuals with variations of a trait which makes them better suited to their environment tend to survive longer and produce more offspring. When they breed they pas on those beneficial alleles to the next generation.

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34
Q

What does natural selection result in?

A

Natural selections results in the non random increase in frequency of advantages alleles and the non random decrease in frequency of deleterious alleles.

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35
Q

What is sexual selection?

A

Sexual selection is the non-random process involving the selection of alleles that increase the individuals chances of mating and producing offspring.

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36
Q

Does sexual selection increase the chance or survival?

A

No, sexual selection does not increase chances of survival, only the likelihood that an organism will reproduce and pass on its alleles.

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37
Q

What can sexual selection lead to?

A

Sexual dimorphism

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38
Q

What causes sexual selection?

A

Male-male rivalry and female choice.

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39
Q

What happens during make to make rivalry?

A

Males compete aggressively to defend territory and get access to females.

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40
Q

What traits are beneficial in male to male rivalry?

A

Larger stronger males or males with the best weaponry increase chances of mating

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41
Q

What is female choice?

A

If males cannot control access to females then females will choose a male based on traits he displays that are considered to be “high quality” of fitness like bright colouring.

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42
Q

What is genetic drift?

A

Genetic drift is a random process which results in an increase or decrease in the frequency of inherited traits.

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43
Q

When does genetic drift occur?

A

Genetic drift occurs when chance events like natural disasters cause unpredictable fluctuations in allele frequency from one generation to the next.

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44
Q

What size of population is genetic drift important in?

A

Genetic drift is more important in small populations as alleles are more likely to be lost from the gene pool.

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45
Q

What are examples of genetic drift?

A

Population bottlenecks- occur when a population size is reduced for at least one generation.
Founder effects- occur through the isolation of a few members of a population from a larger population. The gene pool of a new population is not representative of that in the original population.

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46
Q

How are gene pools altered by genetic drift?

A

Certain alleles may be under represented or over-represented and allele frequencies change.

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47
Q

What are selector pressures?

A

Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles. When selection pressures are strong, the rate of evolution can be rapid.

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48
Q

What are examples of biotic and abiotic selector pressures?

A

Biotic- competition, predation, disease, parasitism.
Abiotic- changes in temp, light, humidity, pH, salinity.

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49
Q

What is fitness?

A

Fitness is an individuals ability to be successful at both surviving and reproducing.

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50
Q

What is fitness a measure off?

A

Fitness is a measure of the tendency of some organisms to produce more surviving offspring than completing members.

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51
Q

What is absolute fitness?

A

Absolute fitness is the ratio between numbers of individuals of a particular genotype after selections to those before selection.

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52
Q

What is the equation for absolute fitness?

A

Frequency of a particular genotype after selection/frequency of a particular genotype before selection

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53
Q

What is relative fitness?

A

Relative fitness is the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype.

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54
Q

What is the relative fitness equation?

A

Number of surviving offspring per individual of a particular genotype/number of surviving offspring per individual of the most successful genotype

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55
Q

What is co-evolution?

A

Co-evolution is the process by which two or more species evolve in response to selection preasure imposed by each other.

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56
Q

Where does co-evolution often occur?

A

Co evolution is frequently seen in pairs of species that have symbiotic interactions.

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57
Q

What is an example of commensalism?

A

Cattle egrets- birds live near cattle as when cattle graze they move and stir up insects. The birds eat the insects.

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58
Q

What is an example of mutualism?

A

Pollinators and plants- birds pollinate plants which allows them to produce nectar which birds benefit from.

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59
Q

What is the red queen hypothasis?

A

The red queen hypothesis states that in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species.

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60
Q

What is asexual production?

A

Offspring arise from a single organism and can share the DNA of that parent only. Offspring can be classed as clones.

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61
Q

What is sexual production?

A

Offspring arise from the combination of male and female gamete’s after process of fertilisation.

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62
Q

What is a disadvantage of sexual reproduction?

A

Only half the population are able to produce offspring
Sexual reproduction involves the mixing of genetic information so only half a genome is passed into offspring. This disrupts successful parental genomes.
Genetic variability in offspring decreases chances all individuals will be susceptible to infection by parasites.

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63
Q

What are benefits of asexual reproduction?

A

Just one parent can produce daughter cells and establish a colony of virtually unlimited size
Offspring can be produced more often and in larger numbers
Whole genomes are transferred- beneficial in narrow stable niches or when recolonising disturbed habitats

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64
Q

What are examples of asexual reproduction in eukaryotes?

A

Vegetative cloning in plants
Parthenogenesis in lower plants and animals that lack fertilisation

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65
Q

What is parthenogenesis?

A

A type of asexual reproduction in which unfertilised female gamete develops into a new individual

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66
Q

What are disadvantages of asexual reproduction?

A

Asexually reproducing populations are not able to adapt easily to changes in their environment- mutations can occur to provide some degree of variation.

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67
Q

Why do asexually reproductive organisms reproduce faster?

A

Can reproduce via horizontal gene transfer. Increases variation and results in faster evolutionary change.

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68
Q

What is meiosis?

A

Meiosis is the devision of the nucleus that results in the formation of haploid gametes from a diploid gametocyte

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69
Q

What are gametocytes?

A

Gametocytes are cells in eukaryotes which give rise to gametes.

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70
Q

What do homologous chromosomes have in common?

A

Same size, same centromere position’ same sequences of genes at the loci-position

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71
Q

What happens prior to mitosis one?

A

Homologous chromosomes have replicated so each is now made up of two identical sister chromatids attached to the centromere.

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72
Q

What is the first step of meiosis one?

A

Chromosomes condense and the homologous chromosomes pair up so that they are aligned gene by gene.

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73
Q

How is a chiasma formed?

A

A chiasma forms between homologous pairs and sections of DNA can be exchanged at these points.

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74
Q

How can a chiasma result in a new combination of alleles?

A

The crossing over of DNA is random and produces genetically different recombinant chromosomes. This can result in new combinations of the alleles of these genes which increase variation.

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75
Q

How are chromosomes aligned at the metaphase during meiosis?

A

Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle. The orientation of the pairs of homologous chromosomes at the equator is random.

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76
Q

What is independent assortment?

A

Each pair of chromosomes is positioned independently of the others, irrespective of whether they came from mother or father. This is known as independent assortment.

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77
Q

How do the homologous chromosomes separate in meiosis?

A

The microtubules of the spindle fibres begin to shorten. The chromosomes of each homologous pair are pulled towards opposite poles. The chromosomes group in each end of the cell and a nuclear membrane forms around them.

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78
Q

What happens at the beginning of meiosis two?

A

Each one if the two cells produced in meiosis one undergoes a further devision and the sister chromatids add separated forming a total of 4 haploid cells.

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79
Q

Why are meiosis produced haploid cells genetically variable?

A

Crossing over allows exchange of DNA
Independent assortment means random allocation of maternal and payeenal chromosomes
Sexual reproduction combines info from 2 parents.

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80
Q

What is sexual reproduction?

A

Offspring arising from the combination of male and female gamete’s after the process of fertilisation.

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81
Q

What is asexual reproduction?

A

Offspring arise from a single organism only and share the DNA of that parent only. Offspring classes as clones.

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82
Q

What are disadvantages of sexual reproduction?

A

Only half the organisms in a population can produce offspring and only half a parents genetic information is passed onto the offspring- this can disrupt successful parent genomes.

83
Q

Why is the main advantage of sexual reproduction?

A

An increased genetic variation in the population.

84
Q

How is sexual reproduction effective against changing selection pressures?

A

The genetic variation in the population provides the raw materials for adaptation which grants a better chance of survival under changing selection pressures

85
Q

How does sexual reproduction grant hosts an advantage over parasites?

A

If host reproduce sexually, the genetic variability of the individuals decreases the chances that all individuals will be susceptible to infection by parasites. This means hosts can resist and tolerate parasitism showing a greater fitness.

86
Q

Why is asexual reproduction a successful strategy?

A

One parent can produce daughter cells and establish very large colonies, The Offspring can be reproduced more often and in larger numbers and whole genomes can be passed from parent to offspring.

87
Q

When is maintaining a genome of a parent especially advantageous?

A

In very narrow, stable niches or when re-colonising disturbed habitats.

88
Q

What are examples of asexual reproduction in eukaryotes?

A

Vegetative cloning in plants
Parthenogenesis in lower plants and animals that lack fertilisation

89
Q

What is parthenogenesis?

A

A type of asexual reproduction in which an unfertilised female gamete develops into a new individual.

90
Q

Where is parthenogenesis common?

A

It is more common in cooler climates or areas with low parasite density or diversity.

91
Q

What is a cost of asexual reproduction?

A

Populations are not able to adapt easily to changes in their environment.

92
Q

How does variation arise in asexual populations?

A

Mutations can occur and provide some degree of variation and enable some natural selection to occur. Organisms that reproduce principally by asexual reproduction often have mechanisms for horizontal gene transfer.

93
Q

What is an advantage of horizontal gene transfer?

A

Increase variation and results in fast evolution change than in organisms that only use verticals transfer.

94
Q

What is meiosis?

A

Meiosis is the devision of the nucleus that results in the formation of haploid gametes from a diploid gametocyte.

95
Q

What is a gametocyte?

A

Cells in eukaryotes which give rise to gametes.

96
Q

What do the homologous chromosomes have in common?

A

The same size
The same centromere position
The same sequence of genes at the same places.

97
Q

How is the sex of birds, mammals and some insects determined?

A

By the presence of sex chromosomes.

98
Q

What does the SRY gene determine?

A

The SRY gene on the Y chromosome determines the development of male characteristics.

99
Q

What is meant by homogametic?

A

All gametes are produced with the same combination of sex chromosomes like in human females.

100
Q

What is meant by heterogametic?

A

Gametes are produced with two possible combinations of sex chromosomes like in human males.

101
Q

What leads to sex linkage?

A

The Y chromosome lacks many genes found on its homologous X chromosome.

102
Q

What is sex linkage?

A

In XX females, a recessive allele on one X can be masked by a dominant allele on the other X. In males there is no second copy to mask it’s effects.

103
Q

What does sex linkage lead to?

A

Carrier females (XB Xb) and affected males (Xb Y)

104
Q

What is X chromosome inactivation?

A

In homogametic females one of the two X chromosomes present in each cell is randomly inactive at an early stage of development.

105
Q

Why is X chromosome inactivation important?

A

Prevents a double dose of gene products which could be harmful to cells. Carriers are less likely to be affected by any deleterious mutations in these X chromosomes.

106
Q

What is a hermaphrodite?

A

Hermaphrodites are species that have functioning male and females reproductive organs. They produce male and female gametes.

107
Q

How to hermaphrodites reproduce?

A

They usually have a partner which they exchange gametes.

108
Q

What is a benefit of being a hermaphrodite?

A

The benefit to the individual organism is that if the chance of encountering a partner is an uncommon event, there is no requirement for the partner to be of the opposite sex.

109
Q

What are some examples of hermaphrodites?

A

Earth worms and land molluscs, must meet another individual to reproduce.

110
Q

What is environmental sex determination?

A

When environmental factors determine sex and sex ratio rather than genetic factors.

111
Q

What factors can change can change sex if individuals?

A

Size, competition, parasitic infection or temperature

112
Q

How is environmental sex determination controlled in reptiles?

A

In reptiles, environment sex determination is controlled by environmental temperature of egg incubation.

113
Q

When is sex ratio of offspring adjusted in some species?

A

In response to resource availability e.g. increased competition

114
Q

What are some features if the female gamete?

A

Large, nutrient filled, expensive to produce, limited in number and produced infrequently.

115
Q

What are some features of male gametes?

A

Small, have no nutrients, cheap to produce and constantly made throughout life.

116
Q

What does fertilisation lead to in females?

A

Fertilisation leads to a high cost to females as there is a greater investment from females than males.

117
Q

In mammals when is there an investment from females?

A

In the uterus and during gestation

118
Q

When is there an investment from females in reptiles?

A

In egg structure

119
Q

What is the advantage of parental investment?

A

Parental investment is costly but increases the probability and survival of young.

120
Q

What separates r-selected and K-selected organisms?

A

level of parental investment and number of offspring produced.

121
Q

What are some features of r-selected offspring?

A

shorter lifespan, singular early reproduction, large amount of small offspring, little energy put into offspring, low offspring survival rate.

122
Q

What are some features of K-selected offspring?

A

longer lifespan, reproduce many times, few offspring, high energy put into offspring, many survive to adult

123
Q

When does r- selection occur?

A

r-selection tends to occur in unstable environment where the species has not reached its reproductive capacity.

124
Q

When does K-selection occur?

A

K-selection tends to occur in stable environments

125
Q

What is internal fertilisation?

A

Internal fertilisation occurs when the male and female gametes fuse inside the body.

126
Q

What is external fertilisation?

A

External fertilisation occurs when male and female gametes fuse outside the body.

127
Q

What are the benefit of internal fertilisation?

A

Increased chance off offspring survival
Fewer eggs needed
Offspring can be retained internally for protection and/or development
Higher offspring survival rate

128
Q

What are the costs of internal fertilisation?

A

A mate must be located which requires energy expenditure
Requires direct transfer of gametes from one partner to another

129
Q

What is the benefit of external fertilisation?

A

Very large numbers of offspring can be produced

130
Q

What are some costs of external fertilisation?

A

Many gametes are predated or unfertilised
Low or no parental care
Few offspring survive

131
Q

What is monogamy?

A

The mating of a pair of animals to the exclusion of all others.

132
Q

What is polygamy?

A

Individuals if one sex have more than one mate.

133
Q

What is Polygyny?

A

one male mates exclusively with a group of females.

134
Q

What is polyandry?

A

One females mates with a number of males in the same breeding season

135
Q

What do many animals do to find a mate?

A

Many animals have mate-selection courtship rituals

136
Q

What is an example of a courtship ritual?

A

In some bird and fish species organisms can produce signals that only members of that species will recognise. The response of a fixed action pattern in the opposite sex.

137
Q

What is an example of sexual dimorphism?

A

Females are generally inconspicuous, males have more conspicuous markings, structures and behaviour.

138
Q

What is opposite sexual dimorphism?

A

Reverse sexual dimorphism.

139
Q

What do honest signals indicate?

A

Indicate favourable alleles that increase the chance of offspring survival or a low parasitic burden suggested a healthy individual.

140
Q

What is lekking?

A

In leaking species males gather to display at a lek, where females choice occurs. Dominant males occupy the centre of the lek, subordinates at the fringes as satellite males.

141
Q

What do females do when they visit the lek?

A

They choose among males based on honest signals, mating occurs, and no further contact goes on between males and females.

142
Q

What do males often have to help with male to male rivalry?

A

Males will often have elaborate weapons such as antlers, tusks, horns.

143
Q

What is an ecological niche?

A

An ecological niche is a multi-dimensional summary of tolerance and requirements of a species

144
Q

What is a fundamental niche?

A

A species has a fundamental niche that it occupies in the absence of inter specific competition.

145
Q

What is a realised niche?

A

A species has a realised niche that in occupied in response to inter specific competition.

146
Q

What is competitive exclusion?

A

When two niches are too similar that one declines to local extinction.

147
Q

When does resource partitioning occur?

A

When the realised niches are sufficiently different, potential competitors can co-exist due to resource partitioning?

148
Q

How does parasitism differ from predator-prey relationships?

A

The reproductive potential of a parasite is greater than that of the host

149
Q

What type of niche to parasites usually have?

A

Narrow (specialised) niche

150
Q

What is the difference between ectoparasites and endoparasites?

A

Ectoparasites live on the surface of the host while endoparasites live within the tissue of the host.

151
Q

What is a definitive host?

A

The organism on or in which the parasite reaches sexual maturity

152
Q

What is an intermediate host?

A

A host aside from the definitive host required for a parasite to complete its lifecycle

153
Q

What does a vector do?

A

A vector plus an active role in the transmission of the parasite and may also be a host.

154
Q

What virus causes malaria?

A

Plasmodium

155
Q

How does a mosquito give plasmodium to a human?

A

An infected mosquito, acting as a vector, bites a human. Plasmodium enters the human bloodstream.

156
Q

Where does plasmodium asexually reproduce?

A

Asexual reproduction occurs in the liver and then the red blood cells.

157
Q

How do gametocyte end up in the human bloodstream?

A

When the red blood cells burst they release gametocyte into the bloodstream

158
Q

How do gametocyte enter back into the mosquito?

A

Another mosquito bites an infected human and the gametocytes enter the mosquito.

159
Q

What is the definitive host of plasmodium?

A

The mosquito as gametocytes mature into male and female gametes allowing for sexual reproduction to occur.

160
Q

What parasite causes schistosomiasis?

A

Schistosomes

161
Q

What is the definitive host of schistosomes?

A

Schistosomes reproduce sexually in the human intestine.

162
Q

How do the fertilised eggs pass into water?

A

The fertilised eggs pass out via faeces onto water where they develop into larvae.

163
Q

Where does asexual reproduction occur in schistosomes?

A

The larvae then infect water snails, where asexual reproduction occurs.

164
Q

What happens after schistosomes asexually reproduce?

A

They produce another type of mobile larvae, which escape the snail and penetrate the skin of humans, entering the bloodstream.

165
Q

What are viruses?

A

Viruses are parasites that can only replicate inside a host cell

166
Q

In what form do viruses contain genetic material?

A

Viruses contain genetic material in the form of DNA or RNA, packages in a protective protein coat.

167
Q

What do some viruses have to help avoid the immune system?

A

some are surrounded by a phospholipid membrane derived from host cell materials

168
Q

What does the outer surface of a virus contain and what can a host cell do with this information?

A

The outer surface of a virus contains antigens that a host cell may or may not be able to detect as foreign.

169
Q

What are the viral life cycle stages?

A

Infection of host with genetic material
Host cell enzymes replicate viral genome
Transcription if viral genes and translation of viral proteins
Assembly and release of new viral particles

170
Q

What are RNA retro viruses?

A

RNA retroviruses are viruses with RNA rather than DNA
e.g. HIV

171
Q

How do RNA retroviruses work?

A

When an RNA retrovirus inject their RNA into a host cell they also inject enzyme reverse transcriptase

172
Q

How does reverse transcriptase work?

A

Reverse transcriptase first synthesises DNA from the single-stranded RNA
This DNA is inserted into the genome of the host cell
Viral genes are then expressed to form new particles.

173
Q

What is transmission?

A

Transmission is the spread of a parasite to a host

174
Q

What is virulence?

A

Virulence is the harm caused by the parasite to a host

175
Q

How to ectoparasites transmit?

A

by direct contact

176
Q

How do endoparasites transmit?

A

By consumption of intermediate host or vectors

177
Q

What mechanisms may viruses have to transmit?

A

Vectors and waterborne dispersal stages
Vectors- mosquitos, ticks
Waterborne dispersal- trematodes, cholera

178
Q

What can cause ectoparasites to transmit easily?

A

Overcrowding

179
Q

What can a parasite do to a host to increase transmission?

A

Host behaviour is often exploited and modified by parasites to maximise transmission. The host behaviour becomes part of the extended phenotype of the parasite.

180
Q

What are some examples of host behaviour a parasite can modify?

A

Foraging, movement, sexual behaviour, choice of habitat and anti-predator behaviour.

181
Q

What can parasites do to the immune system of hosts?

A

Parasites often suppress host immune system and modify host size and reproductive rate in ways that benefit the parasites growth, reproduction and transmission.

182
Q

What aspects of immune response does the body have?

A

Specific and non-specific aspects

183
Q

What are some examples of non-specific defences?

A

Physical barriers and chemical secretions

184
Q

What are some examples of non-specific responses?

A

Natural killer cells, inflammation, phagocytes

185
Q

What is chemical secretion?

A

When epithelial tissue blocks the entry of parasites

186
Q

What are examples of chemical secretions?

A

Hydrolytic enzymes in mucus
Saliva and tears destroy bacterial cell walls
Low pH environments of the secretions in the stomach
Vagina and sweat glands denature cellular proteins of pathogens

187
Q

What is an inflammatory response?

A

Injured cells release signalling molecules
This results in enhanced blood flow to the site, bringing anti microbial proteins and phagocytes

188
Q

How do phagocytes work?

A

Phagocytes engulf the parasite and store them in a vacuole
Kill the parasite using powerful enzymes contained in the lysosome

189
Q

How do natural killer cells work?

A

Identify and attach to cells infected with viruses
Releases chemicals that lead to cell death by inducing apoptosis

190
Q

How does the body monitor tissue?

A

A range of white blood cells constantly circulate the body, monitoring tissues.

191
Q

What do cells release when they become damaged?

A

Cytokines

192
Q

What do cytokines cuase?

A

This causes an increase in blood flow, resulting in non specific and specific white blood cells accumulating at the site of infection or tissue damage

193
Q

How does a lymphocyte detect viruses?

A

Mammals contain many different lymphocytes, each possessing a receptor in its surface, which can potentially recognise a parasite antigen.

194
Q

What does binding of an antigen to a lymphocytes receptor cause?

A

Binding of antigen to a lymphocytes receptor selects that lymphocyte to then devide and produce a clonal population of this lymphocyte.

195
Q

How can a lymphocyte fight infection?

A

Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite infected cells.

196
Q

What gives an antibody it’s specificity for the binding antigen?

A

Antibodies have regions of amino acid sequence which varies greatly between different antibodies. This variable region gives the antibody its specificity.

197
Q

What happens when an antibody binds to an antigen?

A

When the antigen binds to this binding site the antibody l-antigen complex formed can result in inactivation of the parasite, making it susceptible to a phagocyte or can stimulate a response that results in cell lysis.

198
Q

What does initial antigen exposure produce?

A

Initial antigen exposure produces memory lymphocyte cells specific to that antigen.

199
Q

What do memory cells do as a result if second exposure?

A

These memory cells can produce a secondary response when the antigen enters the body in the future. When this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration

200
Q

What is immune evasion?

A

Parasites have evolved ways of evading the immune system, particular success can be demonstrated by endoparasites

201
Q

How can endoparasites avoid stimulating an immune response from mammals despite having foreign antigens?

A

Endoparasites mimic host antigens to evade detection by immune system or modify the host immune response to reduce their chances of destruction

202
Q

What is meant by antigenic variation

A

Allows them to change between different antigens during the course of infection. This allows them to evolve faster than the host immune system can respond.

203
Q

How can a virus avoid secondary response when reinfecting?

A

The virus can change its antigens and reinfect the same host with a new variant

204
Q

What is latency?

A

Some viruses escape immune surveillance by integrating their genome into host genomes existing in an inactive state know as latency. The virus becomes active again when favourable conditions arise.

AH Biology (3 decks)

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