Unit2 - Organisms and Evolution Flashcards
What is a hazard ( in the field) ?
Something with the potential to cause harm i.e manual handling and moving vehicle
What is a risk?
The likelihood of harm arising from exposure to a hazard.
What are some examples of hazards when working in the field?
Terrain- Assessing terrain prior to setting out is essential. Variations may include uneven surfaces, flat areas, hills, and steep gradients.
Adverse weather conditions- Can change very quickly in the field. Appropriate clothing, footwear, and supplies should be selected. In extreme weather, fieldwork may have to be postponed or abandoned.
Isolation- Areas of fieldwork can often be isolated.
Make sure someone at base is aware of routes and expected time of return.
Contact with harmful organisms- dangerous, poisonous or venomous can pose harm to humans.
What do risk assessments involve?
Risk assessment involves identifying control measures to minimise risk.
They should be carried out prior to any fieldwork.
Name some control measures while completing the fieldwork.
Control measures while completing fieldwork can include: Appropriate equipment Appropriate clothing Footwear Means of communication.
Sampling should be carried out in a way that minimises the impact on what?
wild species and habitats.
Consideration should be given to what types of species and habitats?
Consideration should be given to rare and vulnerable species and habitats that are protected by legislation.
What species can you sample using…. Point count?
Birds.
What species can you sample using…. Transect?
Plants / Sessile/ slow moving organisms.
What species can you sample using…. remote detection?
elusive species
What species can you sample using…. capture techniques?
mobile species
Describe the capture technique- point count.
A point count involves the observer recording all individuals seen from a fixed point count location.
This can be compared to other point count locations or with data from the same location gathered at other times.
This method is often used to count bird populations in a given area, over a set period of time.
Describe the capture technique- transects using quadrats.
A transect is a line along which different samples can be taken. These are often set up along an area where the terrain or abiotic factors are variable.
Quadrats of a suitable size and shape for the area are placed along the transect, allowing sessile or slow-moving organism abundance to be recorded.
Abiotic factors can also be measured to determine the habitat features for the organisms.
Describe the capture technique- capture techniques
Capture techniques such as traps and nets, are used for mobile species.
Describe the capture technique-remote detection
Remote detection is used to detect elusive (those that are difficult to find) species. They can be sampled directly by using camera traps or indirectly using scat sampling (examining faecal matter).
Identification of an organism in a sample can be made using what?
Classification Guides
Biological keys
Analysis of DNA or protein.
Organisms can be classified by what?
taxonomy and phylogenetics
What is taxonomy?
Taxonomy involves the identification and naming of organisms and their classification into groups based on shared characteristics. Classic taxonomy classification is based on morphology (the structures and features of organisms).
What is phylogenetics?
Phylogenetics is the study of the evolutionary history and relationships among individuals or groups of organisms. Phylogenetics is changing the traditional classification of many organisms.
What does Phylogenetics use?
Phylogenetics uses heritable traits such as morphology, DNA sequences, and protein structure to make inferences about an organism’s evolutionary history and create phylogeny (phylogenetic tree).
What is a phylogenetic tree?
Phylogenetic tree – a diagrammatic hypothesis of its relationship to other organisms.
Genetic evidence reveals relatedness obscured by what types of evolution
divergent or convergent evolution.
What is divergent evolution?
Increase in morphological differences between species as each adapts to different ecological niches.
What is convergent evolution?
Decrease in morphological differences between species as they adapt to similar ecological niche.
Familiarity with taxonomic groupings allows what it be made?
Predictions and inferences to be made
between an organism and better-known (model) organisms.
What are nematodes?
Nematodes – the round worms which show great variety, many of which are parasitic e.g. tapeworms.
What are arthropods?
Arthropods – the joint-legged invertebrates which are identified by their segmented body, typically with paired appendages, e.g. wasps, butterflies, spiders and crabs.
What are chordates?
Chordates – the sea squirts and vertebrates, e.g. birds, mammals, reptiles, amphibians and fish.
What are model organisms?
Model organisms are those that are either easily studied or have been well studied.
Model organisms from all taxonomic groups are used to obtain information that can be applied what?
Model organisms from all taxonomic groups are used to obtain information that can be applied to species that are more difficult to study directly.
Name a model organism.
Model organisms that have been important in the advancement of modern biology include:
The bacterium E. coli;
The flowering plant Arabidoposis thaliana;
The nemotode C. elegans;
The arthropod Drosophila melanogaster (fruit fly);
Chordates including mice, rats and zebrafish.
Why monitor populations?
Monitoring populations is essential in understanding environmental conditions.
Monitoring can allow us to identify areas of pollution vs clean.
What are indicator species?
The presence, absence or abundance of indicator species can give information of environmental qualities.
For example, the presence of pollutants.
Lichen can give information about air quality (sulphur dioxide levels).
Absence or reduced population indicates a species is what to some factor in the environment?
Susceptible
Abundance or increased population indicates it is what by the conditions?
favoured
Susceptible and favoured species can be used to monitor what?
an ecosystem.
Mark and recapture is a method used for what?
estimating population size.
How do you estimate the population size in calculation?
N = (MC)/R
A sample of the population is captured and marked (M) and released.
After an interval of time, a second sample is captured (C).
If some of the second sample are recaptured (R) then the total population can be represented by
What does mark and recapture technique assume?
This method assumes:
that 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;
That individuals that are marked and released can mix fully and randomly with the total population.
Name the 5 methods of marking?
Banding Tagging Surgical implantation Painting Hair clipping
The method of marking and subsequent observations must minimise the impact on the study species. It should not interfere with what?
It should not interfere with the individual’s normal behaviour or make it more conspicuous to predators.
The mark and recapture method must be clear in order to do what?
to permit subsequent observations.
What is ethology?
the study of animal behaviour.
What is Latency?
the time between the stimulus occurring and the response behaviour.
What is the frequency? (Animal behaviour)
The number of times the behaviour occurs within a period of observation.
What is the duration? (Animal behaviour)
The length of time each behaviour occurs during the observation period
Ethograms are methods of what?
recording animal behaviour over a set period of time.
What do ethograms list?
Specific behaviours observed and recorded in the study e.g eating lying down tail wagging.
The duration of each of the behaviours in the ethograms and what is recorded?
Total time of observation
A time budget can be constructed from an ethogram. What is a time budget?
shows the percentage of time spent on each animal behaviour.
What can a time budget be represented as?
pie chart, tables or charts
When performing an ethogram, what is it important to avoid doing what?
anthropomorphism
What is anthropomorphism?
assigning human emotions/ qualities to animal behaviour
What does anthropomorphism lead to?
invalid conclusion
What is a mutation?
Mutations are rare, random changes to genetic sequences which can be harmful, beneficial or neutral
What 2 ways can genetic material to be passed?
Vertically/ horizontally
What is evolution?
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited trait.
What is the allele frequency
Allele frequency = a measure of how common the allele is within a population/ the proportion of a given allele in the population with respect to all alleles of that gene.
During evolution changes in allele frequency can take place through the processes of:
Selection (non-random)
Sexual selection
Natural selection
Genetic drift (random)
Natural selection acts on what in populations.
genetic variation
Variation in traits arises as a result of what?
mutation.
Mutation is the original source of what?
new sequences of DNA.
These new DNA sequences that come about due to Mutation can be ……. alleles.
novel
Most mutations are harmful or neutral, but in rare cases they may be what?
beneficial to the fitness of an individual.
Describe the process of Natural selection.
As organisms produce more offspring than the environment can support, only the best adapted will survive.
Individuals with variations of a trait which make them better suited to their environment tend to survive longer and produce more offspring
When they breed, they pass on those alleles that confer an advantage to the next generation.
Therefore, natural selection results in the ….(1)…… in the frequency of advantageous alleles and the ….(2)……. in the frequency of deleterious alleles.
(1) - NON RANDOM INCREASE
(2) - NON RANDOM DECREASE
What is sexual selection?
Sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring.
Sexual selection does not increase the chances of survival, just what?
the likelihood that the organism will reproduce and pass on its alleles.
What does sexual selection sometimes lead to?
sexual dimorphism-the presence in a population of two sexes each with a different PHENOTYPE (look different)
Sexual selection can be due to what 2 things?
Female choice/ male vs male rivalry
Describe Male vs Male rivalry (sexual selection)
Males compete aggressively to defend territories and get access to females.
Larger, stronger males or males with better weaponry increase access to females through conflict.
Describe female choice(sexual selection)
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” or fitness.
e.g. ornaments or bright colouring
Genetic drift is a random process which results in what?
an increase or decrease in the frequency of inherited traits.
Genetic drift occurs when?
chance events (e.g. natural disaster) cause unpredictable fluctuations in allele frequency from one generation to the next.
Genetic drift is more important in what type of populations due to what?
small populations, as alleles are more likely to be lost from the gene pool.
what are two examples of genetic drift?
founder effect
population bottleneck
When do population bottlenecks occur?
population bottlenecks occur when a population size is reduced for at least one generation.
how does the founder effect occur?
Founder effects occur through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.
Why is a gene pool altered by genetic drift?
A gene pool is altered by genetic drift because certain alleles may be under-represented or over-represented and allele frequencies change.
When what are strong, the rate of evolution can be rapid.
selection pressures
What are selection pressures?
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.
What are some biotic selection pressures?
competition, predation, disease, parasitism
What are some abiotic selection pressures?
changes in temperature, light, humidity, pH, salinity.
The Hardy-Weinberg (HW) principle states what?
That, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.
The HW principle can be used to determine what?
whether a change in allele frequency is occurring in a population over time.
The HW principle can be used to calculate what?
allele, genotype, and phenotype frequencies in populations
Describe the Hardy-weinberg equation?
p2 + 2pq + q2 = 1
p+q=1
p = frequency of dominant allele
q = frequency of recessive allele
p2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q2 = frequency of homozygous recessive genotype
Changes suggest evolution is occurring.
what are the conditions for maintaining HW equilibrium
no natural selection,
random mating occurs,
no mutation,
large population size and
no gene flow (through migration, in or out).
‘Fitness’ of the individual is an indication of what?
Fitness is an indication of an individuals ability to be successful both at surviving and reproducing.
Fitness is a measure of the tendency of some organisms to do what?
produce more surviving offspring than competing members of the same species.
Fitness refers to what?
the contribution that is made to the gene pool of the next generation by individual genotypes.
Fitness can be determined in what terms?
absolute and relative terms
What is absolute fitness?
Absolute fitness is the ratio between the number of individuals of a particular genotype after selection, to those before selection.
Frequency of a particular genotype after selection/ Frequency of a particular genotype before selection
What happens if you get an absolute fitness of:
a) 1
b) above 1
c) below 1
If the absolute fitness is 1, then the frequency of that genotype is stable.
A value greater than 1 conveys an increase in the genotype
A value less than 1 conveys a decrease.
What is relative fitness?
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.
Number of surviving offspring per individual of a particular genotype
/ Number of surviving offspring per individual of the most successful genotype
What is co-evolution
Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other.
In co-evolution, a change in the trait of one species acts as what on the other species
selection pressure
Co-evolution is frequently seen in pairs of species that have what?
symbiotic interactions.
What is symbiosis?
Symbiosis – co-evolved intimate relationship between members of two different species.
What is mutualism?
Mutualism: both organisms in the interaction are interdependent on each other for resources or other services. As both organisms gain from the relationship, the interaction is (+/+).- plover and crocodile
What is parasitism?
Parasitism: the parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-)- vampire finch/ bobby
What is communalism?
Commensalism: only one of the organisms benefits (+/0)- fox and carbiou.
What does the red queen hypothesis state?
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.
This means that species in these relationships must adapt to avoid extinction.
What is sexual reproduction?
Sexual- offspring arise from the combination of male and female gametes after the process of fertilisation.
What is asexual reproduction?
Asexual- offspring arise from a single organism and share the DNA of that parent only. Offspring can be classed as clones.
What are the costs (disadvantages) of sexual reproduction?
There are two main disadvantages:
In any population where sexual reproduction is the reproductive strategy, only half of the population are able to produce offspring.
Sexual reproduction involves the mixing of genetic information. This means only half of each parent’s genome passed onto offspring, disrupting successful parental genomes
What are the benefits (advantages) of sexual reproduction?
Although there are costs to sexual reproduction, the benefits outweigh these due to an increase in genetic variation in the population.
This provides the raw material for adaptation which gives sexually reproducing organisms a better chance of survival under changing selection pressures (e.g. surviving new strains of diseases)
Without such genetic variety produced by sexually reproducing organism what would stop?
the Red Queen’s arms race
Co-evolutionary interactions between parasites and hosts may select for what type of hosts?
sexually reproducing hosts.
What does the genetic variability of sexually reproducing organism’s offspring do to their chances when they meet a parasite?
in their offspring decreases the chances that all of the individuals will be susceptible to infection by parasites.
The genetic variability in their offspring decreases the chances that all of the individuals will be susceptible to infection by parasites. What does this mean for the host?
This means that the host will be able to resist and tolerate parasitism, therefore showing greater fitness.
When will a parasite have greater fitness?
Parasites that are better able to feed, reproduce and find new hosts have greater fitness.
What are the benefits of asexual reproduction?
Just one parent can produce daughter cells and establish a colony of virtually unlimited size over time.
Offspring can be reproduced more often and in larger numbers
Whole genomes are passed on from parent to offspring.
When is asexual reproduction a useful strategy to use?
Maintaining the genome of the parent is an advantage particularly in very narrow, stable niches (very little environmental changes) or when re-colonising disturbed habitats.
What are examples of asexual reproduction in Eukaryotes?
Budding
vegetative cloning in plants
parthenogenesis in lower plants and animals that lack fertilisation.
What is parthenogenesis?
Parthenogenesis is a type of asexual reproduction in which an unfertilised female gamete develops into a new individual
What type of organisms carry out parthenogenesis?
Fire ants
Stick insects
Komodo dragon
Where is parthenogenesis most common?
It is more common in cooler climates or areas with low parasite density or diversity.
Cost of asexual reproduction?
Asexually reproducing populations are not able to adapt easily to changes in their environment
In asexually reproducing what do mutations (when they occur) enable to happen?
mutations can occur that provide some degree of variation and enable some natural selection to occur.
Organisms which reproduce principally by asexual reproduction also often have mechanisms for what?
horizontal gene transfer (between organisms of the same generation)
E.g. the exchange of plasmids in bacteria and yeast
What does horizontal gene transfer increases?
variation
What does horizontal gene transfer results in what?
faster evolutionary change than in organisms that only use vertical transfer.
What is meiosis?
Meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte
What is a gametocyte?
cells in eukaryotes that give rise to gametes
How many chromosomes do human body cells have?
46 chromosomes (23 pairs)
The two chromosomes in a pair are called what?
Homologous chromosomes
Homologous chromosomes have the same what?
the same size
the same centromere position
the same sequences of genes at the same loci (Latin: ‘places’).
How are homologous pairs are found because?
Homologous pairs are found because one copy of each chromosome has come from the female parent and the other copy has come from the male parent.
Because they are inherited from different parents, the alleles of the genes on each homologous chromosome may be different.
What does Meiosis produce?
genetically variable haploid cells which develop into gametes.
After meiosis, fertilisation happens what happens during fertilisation?
During fertilisation, gametes fuse their haploid nuclei to produce a diploid cell.(zygote)
After fertilisation, what happens?
Mitosis then produces genetically identical diploid cells to make a multicellular organism.
Meiosis is not what?
Meiosis is not a cycle.
Gametocytes (Gamete mother cells) undergo what to produce haploid cells
meiosis
What happens during interphase (prior to meiosis I)?
During interphase (prior to meiosis I), the homologous chromosomes have replicated so each is now made up of two identical sister chromatids attached at the centromere.
What happens during meiosis I - Pairing of homologous chromosomes
The chromosomes condense and the homologous chromosomes pair up so that they are aligned gene by gene.
Where does the chiasma form between homologous pairs?
forms at a random position between the homologous pairs.
Where can’t chiasmas form?
Never between sister chromatids.
What happens were chiasmas form?
Sections of DNA can be exchanged at these points.
The crossing over of DNA at the charisma during meiosis I is what and produces what?
This crossing over of DNA is random and produces genetically different recombinant chromosomes
The production of genetically different recombinant chromosomes can result in what?
new combinations of the alleles of these genes which increases variation
Genes that are situated closely on a chromosome are less likely to be separated during crossing over, whereas genes that are further apart are much more likely to be what?
separated.
Describe the Misosis I alignment on the metaphase plate?
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.
This means each pair is positioned independently of the others, irrespective of whether they came from mother or father
This is known as independent assortment.
What is meant by the term independent assortment?
The orientation of the pairs of homologous chromosomes at the equator is random.
This means each pair is positioned independently of the others, irrespective of whether they came from mother or father
This is known as independent assortment.
What does independent assortment result in (end of meiosis II)
variation in the combinations of chromosomes found in the haploid cells at the end of meiosis II.
With three pairs of chromosomes, there are how many combinations?
2x2x2 = 8 combinations.
Describe Meiosis I- separating homologous chromosomes?
The microtubules of the spindle fibres begin to shorten.
The chromosomes of each homologous pair are separated and move towards opposite poles of the cell.
The chromosomes group in each end of the cell and a nuclear membrane forms around them.
Cytokinesis occurs and two daughter cells are formed.
The sister chromatids are no longer identical due to the crossing over.
Two haploid cells are formed
Describe Meiosis II- second division?
Each one of the two cells produced in meiosis I undergoes a further division
The sister chromatids of each chromosome are separated.
A total of four haploid cells are produced.
The sex of birds, mammals and some insects is determined by what?
the presence of sex chromosomes
What is the default setting for human embryonic development?
is to become female (hence male nipples!).
The Y chromosome has a gene called what?
Y-chromosome has a gene called SRY
(Sex determining Region of Y-chromosome).
In most mammals, the SRY gene on the Y chromosome determines the development of what?
male characteristics
Because they are homologous, the sex chromosomes are what?
separated during meiosis into different gametes.
What does homogametic mean?
Human females produce all gametes with the same combination of sex chromosomes = homogametic.
What does hetrogametic mean?
Human males produce gametes with two possible combinations of sex chromosomes = heterogametic.
The y-chromosome lacks what that is found on its homologous x chromosome?
many genes
The Y-chromosome lacks many genes found on its homologous X-chromosome.
This leads to what?
a pattern of inheritance called sex linkage.
What is sex linkage?
In XX females, a recessive allele on one X can be masked by a dominant allele on the other X.
In XY males, a recessive allele on the X has no second copy to mask its effects.
This can lead to carrier females (XBXb) and affected males (XbY)
In homogametic females (XX) one of the two X chromosomes present in each cell is randomly………. at an early stage of development
inactivated
What is x chromosome inactivation?
X chromosome inactivation is a process by which most of one X chromosome is inactivated.
What does x chromosome inactivation prevent?
X chromosome inactivation prevents a double dose of gene products, which could be harmful to cells
what are less likely to be affected by any deleterious mutations on these X chromosomes ?
Carriers
As the X chromosome inactivated in each cell is random, half of the cells in any tissue will have what?
a working copy of the gene in question
What are hermaphrodites and what do they produce?
Hermaphrodites are species that have functioning male and female reproductive organs in each individual
They produce both male and female gametes and usually have a partner with which to exchange gametes
What are the benefits of being a hermaphrodite?
The benefit to the individual organism is that if the chance of encountering a partner is an uncommon event, there is no requirement for that partner to be of the opposite sex
What are some creatures that are hemaphrodites?
Earthworms and most land molluscs are hermaphroditic but must meet another individual to reproduce.
For other species what factors determine sex and sex ratio ? (3)
Sex can change within individuals of some species as a result of size, competition, parasitic infection, or temperature
Environmental sex determination in reptiles is controlled by environmental temperature of egg incubation.
In some species the sex ratio of offspring can be adjusted in response to resource availability e.g. increased competition
Amongst vertebrates, the clearest dimorphism is between what?
gamete (sex cell) size.
What are the differences between male and female gametes?
Females gametes: large, nutrient-filled, expensive to produce, limited in number, and produced infrequently. If fertilised this will lead to high costs to the female.
Male gametes: small, have no nutrients, cheap to produce, constantly made throughout life.
There is a greater investment from females than from males what is the female investment in mammals?
In mammals, there is an investment in the uterus and during gestation
There is a greater investment from females than from males what is the female investment in non-mammals?
In non-mammals, there is investment in the egg structure.
Parental investment is costly but does what?
increases the probability of production and survival of young
Organisms can be classified as r-selected (r-strategists) or K-selected (K-strategists) organisms based on what?
their level of parental investment in offspring and the number of offspring produced.
Describe K strategists:
Physical size?
Lifespan?
Maturation time?
Number of reproductive episodes ?
Number of offspring produced?
Size of offspring produced?
Energy input into offspring?
Level of parental care?
Success rate of rearing young to adulthood?
Larger
Long
Slow
Reproduce many times in their lifetime
Few
Large
High
High
Many have a high probability of surviving to adulthood
Describe R strategists:
Physical size?
Lifespan?
Maturation time?
Number of reproductive episodes ?
Number of offspring produced?
Size of offspring produced?
Energy input into offspring?
Level of parental care?
Success rate of rearing young to adulthood?
Smaller
Short generation time
Rapid
Often only once (and reproduce earlier in lifetime)
Large number
Small
Small
Limited
Most offspring do not reach adulthood
r-selection tends to occur in where?
unstable environments where the species has not reached its reproductive capacity
K-selection tends to occur in where?
whereas K-selection tends to occur in stable environments
Where does internal fertilisation occur?
Internal fertilisation occurs when the male and female gametes fuse inside the body. E.g. in humans.
Where does external fertilisation occur?
External fertilisation occurs when male and female gametes occur outside the body. E.g. in frogs.
What are internal fertilisation benefits?
Increased chance of successful fertilisation
Fewer eggs needed
Offspring can be retained internally for protection and/or development
Higher offspring survival rate
What are internal fertilisation costs?
A mate must be located, which requires energy expenditure
Requires direct transfer of gametes from one partner to another
What are external fertilisation benefits?
Very large numbers of offspring can be produced
What are external fertilisation costs?
Many gametes predated or not fertilised
No or limited parental care
Few offspring survive
Mating systems can differ based on what?
how many mates an individual has during one breeding season.
What is monogamy?
Monogamy: the mating of a pair of animals to the exclusion of all others.
What is polygamy?
individuals of one sex have more than one mate. _
What is Polygyny?
one male mates exclusively with a group of females. _
What is Polyandry?
one female mates with a number of males in the same breeding season.
In some bird and fish species, organisms can produce signals that only other members of that species will recognise. What is this called?
Species-specific stimuli
In some bird and fish species, organisms can produce signals that only other members of that species will recognise- species-specific stimuli. What is the response to this?
The response is a fixed action pattern in the opposite sex
What does sexual selection select for?
Characteristics that have little survival benefit for the individual, but increase their chances of mating
Many species exhibit sexual dimorphism as a product of sexual selection. What do males look like in comparison to females?
Females are generally inconspicuous; males usually have more conspicuous markings, structures, and behaviour.
Does type of sexual dimorphism occur in some species?
reversed
What does female choice involve?
Female choice involves females assessing honest signals of the fitness of males
Honest signals can indicate favourable alleles that increase the chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual.
e.g. in lekking species
Define honest signals?
Honest signals can indicate favourable alleles that increase the chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual.
Describe Lekking?
In lekking species, males gather to display at a lek, where female choice occurs (e.g. in some bird species)
Dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as ‘satellite’ males.
Females visit the lek and choose among the males based on honest signals (e.g. healthy plumage)
Generally, after mating occurs, no further contact goes on between males and females.
Describe male vs male rivalry?
Male-male rivalry through conflict (real or ritualised), increases access to females for mating
Males will fight for dominance and access to females
Males will often have elaborate ‘weapons’ such as antlers, tusks, horns.
What is an ecological niche?
An ecological niche is a multi-dimensional summary of tolerances and requirements of a species.
What is a fundamental niche?
A species has a fundamental niche that it occupies in the absence of any interspecific competition. (different species)
What is a realized niche?
A realised niche is occupied in response to interspecific competition. (different species)
As a result of interspecific competition, what can occur,
competitive exclusion
What is competitive exclusion?
where the niches of two species are so similar that one declines to local extinction.
When can resource partitioning happen?
Where the realised niches are sufficiently different, potential competitors can co-exist by resource partitioning.
Parasitism is a symbiotic interaction between what?
a parasite and its host (+/-).
Describe parasitism?
A parasite gains benefit in terms of nutrients at the expense of its host.
Unlike in a predator-prey relationship, the reproductive potential of the parasite is greater than that of the host.
Parasite tend to have what type of niche?
Parasites tend to have a narrow (specialised) niche as they are very host-specific.
As a host provides so many of the parasite’s needs, many parasites are what?
degenerate, lacking in structures and organs found in other organisms:
What is ectoparasite?
Ectoparasites live on the surface of its host
What is endoparasite?
Endoparasites live within the tissues of its host
Some parasites require only one host to complete their life cycle.
Many parasites require more than one host to complete their life cycle. these can be what or what?
Definite and intermediate host
What is a definite host?
The definitive host is the organism on or in which the parasite reaches sexual maturity.
What is an intermediate host?
Intermediate hosts may also be required for the parasite to complete its life cycle.
What is a vector?
A vector plays an active role in the transmission of the parasite and may also be a host.
What causes malaria?
Plasmodium causes malaria
What acts as a vector for malaria?
An infected mosquito, acts as a vector, bites a human.
Describe the path of the infection of the plasmodium parasite?
Plasmodium enters the human bloodstream.
Asexual reproduction occurs in the liver and then in the red blood cells.
When the red blood cells burst gametocytes are released into the bloodstream.
Another mosquito bites an infected human and the gametocytes enter the mosquito, maturing into male and female gametes, allowing sexual reproduction to now occur.
The mosquito can then infect another human host.
What is the definitive host for plasmodium?
mosquito
What is the intermediate host for plasmodium?
human
What causes the human disease schistosomiasis?
Schistosomes
Describe the process in the disease schistosomiasis?
Schistosomes reproduce sexually in the human intestine.
The fertilised eggs pass out via faeces into water where they develop into larvae.
The larvae then infect water snails, where asexual reproduction occurs.
This produces another type of motile larvae, which escape the snail and penetrate the skin of humans, entering the bloodstream.
Schistosomiasis - definitive host –
human
Schistosomiasis – intermediate host
– water snail
Schistosomiasis – vector –
snails
What are viruses?
Are parasites that can only replicate inside a host cell
Viruses contain genetic material in the form of DNA or RNA, packaged in what?
a protective protein coat.
Some viruses are surrounded by what?
a phospholipid membrane derived from host cell materials (helps to avoid the immune system).
The outer surface of a virus contains what?
antigens that a host cell may or may not be able to detect as foreign.
Describe the stages of virus’s life cycle?
Infection of host cell with genetic material
Host cell enzymes replicate viral genome.
Transcription of viral genes and translation of viral proteins.
Assembly and release of new viral particles.
What are RNA Retroviruses?
RNA Retroviruses are viruses with RNA rather than DNA
When RNA retroviruses inject their RNA into a host cell they also inject what?
an enzyme (reverse transcriptase)
What happens to the new DNA that reverse transcriptase make from single stranded RNA?
This new DNA is then inserted into the genome of the host cell.
RNA Retroviruses are viruses with RNA rather than DNA. As part of the host’s DNA, the viral genes can then be expressed to form what?
new viral particles.
Describe the life cycle of the RNA retrovirus?
Virus antigens attach to the host cell surface
Virus RNA genome inserted into host cell
Viral enzyme called reverse transcriptase reads Viral RNA to form DNA
New forms of viral DNA is inserted into the genome of the host cell
Viral genes are transporting to RNA and translated to make viral proteins.
Virus particles are assembled and burst out of the host cell.
Describe the life cycle of the RNA retrovirus?
Virus antigens attach to the host cell surface
Virus RNA genome inserted into the host cell
A viral enzyme called reverse transcriptase reads Viral RNA to form DNA
New forms of viral DNA is inserted into the genome of the host cell
Viral genes are transporting to RNA and translated to make viral proteins.
Virus particles are assembled and burst out of the host cell.
What is transmission?
Transmission is the spread of a parasite to a host
What is virulence?
Virulence is the harm (deleterious effect) caused to a host by a parasite
Parasites show a wide range of methods of transmission name some?
direct contact between hosts (e.g. human head lice)
vector (e.g. Anopheles mosquito in plasmodium transmission to humans)
consumption of secondary host (e.g. beef tapeworm)
water-borne infective stage (e.g. free-living stages in Schistosomiasis)
How do ectoparasites spread?
direct contact between hosts (e.g. human head lice)
consumption of intermediate host (e.g. beef tapeworm)
How do endoparasites spread?
vector (e.g. Anopheles mosquito in plasmodium transmission to humans)
Describe how overcrowding of host affects transmission?
Overcrowding of hosts when they are at high density spread parasites.
Mechanisms, such as vectors and waterborne dispersal stages, allow the parasite to spread even if what?
infected hosts are incapacitated.
Vectors – e.g. mosquitoes, ticks, tsetse flies
Waterborne dispersal – e.g. trematodes, cholera
What is used by the parasite to maximize its transmission?
Host behaviour is often exploited and modified by parasites to maximise transmission.
What types of things can parasites alter in host behavior?
For example, alter host:
Foraging
Movement
Sexual behavior
Habitat choice
Anti-predator behavior
The host behaviour becomes part of what of the parasite?
The host behavior becomes part of the extended phenotype of the parasite.
What do parasites do to host immune systems, size and reproductive rate and how do they benefit by do so?
Parasites often suppress the host immune system and modify host size and reproductive rate in ways that benefit the parasite growth, reproduction or transmission.
Our immune system has many ways by which it can respond to invasion by foreign cells, e.g. a parasite.
The immune response has both what and what aspects?
non-specific and specific aspects.
Name some examples of nonspecific defenses in the body.
Physical barriers -e.g skin
Chemical secretions
Inflammatory response
Phagocytes
Natural killer cells (destroy cells infected with viruses)
What do phagocytes do?
Phagocytes engulf and digest pathogens
What are antibodies?
Antibodies are specific proteins produced during immune responses
What are lymphocytes?
Lymphocytes produce antibodies
What type of tissue blocks the entry of parasites through chemical secretions? - non specific defences.
Epithelial
Epithelial tissue blocks the entry of parasites. Examples of this are?
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.
What type of enzymes are found in mucus
hydrolytic enzymes
Salvia a tears destroy what?
bacterial cell walls
Vagina and sweat glands denature what?
cellular proteins of pathogens.
Describe the non specific defences of the inflammatory response.
Inflammatory response:
Injured cells release signalling molecules.
This results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes.
Describe the non specific defences of the phagocytes.
Engulf the parasite and store them in a vacuole
Kill the parasite by using powerful enzymes contained in lysosome
Where do phagocytes store the parasite and how do they kill it?
vacuole
Kill the parasite by using powerful enzymes contained in lysosome
Describe the stages of phagocytosis?
- Phagocytes move to site of injury
- plasma membrane of the phagocyte engulfs the parasite
- Parasite is brought into the phagocytes in a vacuole
- Lysosomes move towards the vacuole
- Lysosomes fuse with the vacuole releasing digestive enzymes
- parasite is digested.
Describe the non specific defences of the natural killer cells.
Identify and attach to cells infected with viruses
Release chemicals that lead to cell death by inducing apoptosis.
How do natural killer cells lead to cell death?
The release chemicals that lead to cell death by inducing apoptosis.
A range of what constantly circulate the body, monitoring tissues.
white blood cells
If tissue becomes damaged or invaded, white blood cells release what?
cytokines
If the tissue becomes damaged or invaded, white blood cells release cytokines
This causes an increase in what?
Blood flow, resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage.
Mammals contain many different lymphocytes (specific cellular defense), each possessing what?
a receptor on its surface, which can potentially recognise a parasite antigen.
Binding of antigen to a lymphocyte’s receptor stimulates that lymphocyte to then do what?
divide and produce a clonal population of this lymphocyte.
What do different roles of lymphocytes? 2 different!
Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells.
This variable region gives the antibody its specificity for the binding antigen.
Antibodies have what that varies greatly between different antibodies
Antibodies have regions of amino acid sequence which varies greatly between different antibodies.
What gives the antibody its specificity for the binding antigen?
Antibodies have regions of amino acid sequence which varies greatly between different antibodies.This variable region gives the antibody its specificity for the binding antigen.
When the antigen (lymphocyte) binds to this binding site what is formed?
When the antigen binds to this binding site the antigen-antibody 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.
When the antigen (lymphocyte) binds to this binding site the antigen-antibody complex formed can result in
what?
inactivation of the parasite, making it susceptible to a phagocyte, or can stimulate a response that results in cell lysis.
Initial antigen exposure produces what?
memory lymphocytes cells specific for that antigen
What can memory lymphocytes produce?
These memory lymphocytes cells can produce a secondary response when the antigen enters the body in the future.
These memory lymphocyte cells can produce a secondary response when the antigen enters the body in the future. When this occurs what happens?
When this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration.
Parasites have evolved ways of evading what?
the immune system (refer back to co-evolution).
Particular success of invading the host immune system can be demonstrated by what?
Endoparasites.
How do endoparasites avoid stimulating an immune response?
Endoparasites don’t stimulate an immune response from mammals despite having foreign antigens.
How do endoparasites mimic what?
Endoparasites mimic host antigens to evade detection by the immune system.
What are endoparasites capable of modifying what?
Endoparasites are also capable of modifying the host-immune response to reduce their chances of destruction.
Some parasites show antigenic variation what does this mean?
Ability to change between different antigens during the course of an infection.
What does antigenic variation allow parasites to do?
Which allows them to change between different antigens during the course of an infection.
This allows them to evolve faster than the host immune system can respond to the new antigens.
And can also allow re-infection of the same host with the new variant.
Some viruses escape immune surveillance by doing what with there genome and hosts genome
integrating their genome into host genomes existing in an inactive state known as latency.
What is latency?
integrating their genome into host genomes existing in an inactive state known as latency.
When can the virus become active again after latency? Example.
The virus becomes active again when favorable conditions arise e.g. herpes simplex virus.
What is epidemiology?
EPIDEMIOLOGY is the study of the outbreak and spread of infectious disease.
What do vaccines help reduce?
Vaccinations reduce the spread of disease as vaccines contain antigens that can elicit an immune response.
Enough people vaccinated can bring about what?
herd immunity
What is the herd immunity threshold?
The herd immunity threshold is the density of resistant hosts in the population required to prevent an epidemic
There are many challenges to overcome in the successful treatment and control of parasites name a few and describe them.
- Some parasites are difficult to culture in the laboratory, making it difficult to design vaccines.
There is no way to study effects of treatment using a host animal
E.g. Schistosoma needs host signals to develop - Rapid antigenic variation has to be reflected in the design of vaccines.
Makes it difficult to make vaccines
E.g. need a new influenza vaccine each year - The similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite.
Describe the conditions that promote transmission
- Overcrowding allows parasite to spread rapidly
Overcrowding can occur in refugee camps that result from war or natural disasters (such as hurricanes, floods and earthquakes) or rapidly growing cities in less economically developed countries (LEDCs). - Tropical climates also allow parasites to spread rapidly.
Parasites are more common in tropical climates, including in many LEDCs. This is because there are larger numbers of the insect vectors used by parasites to transmit them to new hosts.
Conditions that promote transmission make what programs difficult to control parasites?
These conditions make co-ordinated treatment and control programs difficult to achieve.
Improvements in parasitic control can do what?
However, improvements in parasite control can reduce child mortality and result in population-wide improvements in child development as individuals have more resources for growth and development.
How would you tackle other parts of parasites life cycles? example…
Often these may be the only practical strategies
Medicines/vaccines are too difficult or expensive to develop
Instead target the transmission of the pararsite:
vectors (malaria) – mosquito nets – reduce vectors from infecting new host
water-borne (schistosomiasis) – civil engineering projects to improve sanitation – parasite is not transferred from human waste into drinking water or bathing water.
Civil engineering projects are used to do what and are combined with what?
to improve sanitation combined with coordinated vector control may often be the only practical control strategies.
E.g. sewage systems using microbes which break down sewage into harmless products. This has helped eradicate diseases such as cholera and dysentery in developed countries. These diseases are still common in poorer or less technologically advanced countries which have poor sanitation.
