Unit 2 Flashcards
Hazards in Fieldwork
Hazards in fieldwork include adverse weather conditions, difficult terrain, problems associated with isolation, and contact with harmful organisms
How should sampling be carried out
in a manner that minimises impact on wild species and habitats
What consideration must be given when carrying out fieldwork
Consideration must be given to rare and vulnerable species and habitats that are protected by legislation
Point count
A point count involves the observer recording all individuals seen from a fixed point count location.
What is used to sample sessile or slow moving organisms
Quadrats, of suitable size and shape, or transects are used for plants and other sessile or slow-moving organisms
What is used to sample mobile species
Capture techniques, such as traps and nets, are used for mobile species
What techniques are used to sample elusive species
Elusive species can be sampled directly using camera traps or an indirect method, such as scat sampling
How can an organism be identified and classified
Identification of an organism in a sample can be made using classification guides, biological keys, or analysis of DNA or protein
Organisms can be classified by both taxonomy and phylogenetics
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.
Phylogenetics
Phylogenetics is the study of the evolutionary history and relationships among individuals or groups of organisms
Phylogenetics uses heritable traits such as morphology, DNA sequences, and protein structure to make inferences about an organism’s evolutionary history
Taxonomic groups
Nematodes, arthropods and chordates are examples of taxonomic groups.
Model organisms
Model organisms are those that are either easily studied or have been well studied
Model organisms examples
E. coli
Arabidopsis
C elegans
Drosophila
Indicator species
Presence, absence or abundance of indicator species can give information of environmental qualities, such as presence of a pollutant
Population estimate formula
Procedure for the mark and recapture technique as a method for estimating population size using the formula
N= MC/R
Methods of marking animals
Methods of marking animals such as: banding, tagging, surgical implantation, painting and hair clipping
Measurements used to quantify animal behavior
latency, frequency and duration
Latency
Latency is the time between the stimulus occurring and the response behaviour.
Frequency
Frequency is the number of times a behaviour occurs within the observation period.
Duration
Duration is the length of time each behaviour occurs during the observation period.
Ethogram
An ethogram lists species-specific behaviours to be observed and recorded in the study. Recording the duration of each of the behaviours in the ethogram, together with the total time of observation, allows the proportion of time spent on each behaviour to be calculated in the time budget.
Anthropomorphism
When human characteristics and feelings are implied against animals
Evolution
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
Non random evolution
Natural and sexual selection
Random evolution
Genetic drift
Effects that mutations can have
Harmful, neutral or beneficial
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 may lead to sexual dimorphism
Male-male rivalry
large size or weaponry increases access to females through conflict.
Female Choice
Female choice involves females assessing the fitness of males.
Genetic Drift
Genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool
Bottlenecks
Population bottlenecks occur when a population size is reduced for at least one generation.
Founder effect
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.
Selection pressures
Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.
They can be biotic: competition, predation, disease, parasitism; or abiotic: changes in temperature, light, humidity, pH, salinity
Hardy Weinberg Principle
The Hardy-Weinberg (HW) principle states that, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations
Conditions for maintaining the Hardy Weinberg principle
The conditions for maintaining the HW equilibrium are: no natural selection, random mating, no mutation, large population size and no gene flow
Hardy Weinberg principle formula
p2 +2pq+q2 =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
Fitness
Fitness is an indication of an individual’s ability to be successful at surviving and reproducing
refers to the contribution made to the gene pool of the next generation by individual genotypes
Absolute fitness
Absolute fitness is the ratio between the frequency 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
Absolute fitness number results
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 and a value less than 1 conveys a decrease.
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
Co evolution
Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other
Symbiosis
Symbiosis: co-evolved intimate relationships between members of two different species.
Symbiotic interaction
Mutualism, commensalism, and parasitism are types of symbiotic interactions
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 (+/+).
Commensalism
only one of the organisms benefits (+/0)
Parasitism
The parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-).
Red queen hypothesis
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
The Red Queen hypothesis to explain the persistence of sexual reproduction
Co-evolutionary interactions between parasites and hosts may select for sexually reproducing hosts
If hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites
Asexual reproduction can be a successful reproductive strategy as whole genomes are passed on from parent to offspring
Maintaining the genome of the parent is an advantage particularly in very narrow, stable niches or when re-colonising disturbed habitats
Costs of sexual reproduction
Costs of sexual reproduction: males unable to produce offspring; only half of each parent’s genome passed onto offspring, disrupting successful parental genomes
Parthenogenesis
Parthenogenesis is reproduction from a female gamete without fertilisation.
Offspring can be reproduced more often and in larger numbers with asexual reproduction
Parthenogenesis is more common in cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity
What organisms use horizontal gene transfer
plasmids of bacteria and yeasts (prokaryotes)
Meiosis
Meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte
Homologous chromosomes
Homologous chromosomes are chromosomes of the same size, same centromere position and with the same sequence of genes at the same loci.
Meiosis 1
The chromosomes, which have replicated prior to meiosis I, each consist of two genetically identical chromatids attached at the centromere
The chromosomes condense and the homologous chromosomes pair up
Chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged
This crossing over of DNA is random and produces genetically different recombinant chromosomes
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
The chromosomes of each homologous pair are separated and move towards opposite poles
Cytokinesis occurs and two daughter cells form
Meiosis 2
Each of the two cells produced in meiosis I undergoes a further division during which the sister chromatids of each chromosome are separated
A total of 4 haploid cells are produced
Parental investment
Greater investment by females
Parental investment is costly but increases the probability of production and survival of young
R-selected species
smaller; have a shorter generation time;
mature more rapidly;
reproduce earlier in their lifetime, often only once;
produce a larger number of smaller offspring, each of which receives only a smaller energy input;
limited parental care;
most offspring will not reach adulthood.
K selected species
larger and live longer;
mature more slowly;
can reproduce many times in their lifetime;
produce relatively few, larger offspring;
high level of parental care;
many offspring have a high probability of surviving to adulthood.
External fertilization costs and benefits
benefits: very large numbers of offspring
can be produced
costs: many gametes predated or not fertilised; no or limited parental care; few offspring survive
Costs and benefits of internal fertilization
benefits: increased chance of successful
fertilisation;
fewer eggs needed;
offspring can be retained internally for protection and/or development;
higher offspring survival rate
costs: a mate must be located, which requires energy expenditure;
requires direct transfer of gametes from one partner to another
Monogamy
Monogamy: the mating of a pair of animals to the exclusion of all others.
Polygamy
Polygamy: individuals of one sex have more than one mate.
Polygyny
Polygyny: one male mates exclusively with a group of females.
Polyandry
Polyandry: one female mates with a number of males in the same breeding season.
Conspicuous
More obvious, males are usually more conspicuous as they have colourful markings etc.
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.
Lekking
Some bird species exhibit lekking behaviour. Dominant males occupy the centre of the lek, with subordinates and juveniles at the fringes as ‘satellite’ males. During the display, female choice occurs.
Male rivalry
Males will fight for dominance and access to females, often using elaborate ‘weapons’ such as antlers, tusks, horns.
Niche
An ecological niche is a multi-dimensional summary of tolerances and requirements of a species A species has a fundamental niche that it occupies in the absence of any interspecific competition
A realised niche is occupied in response to interspecific competition
As a result of interspecific competition, competitive exclusion can occur, where the niches of two species are so similar that one declines to local extinction
Where the realised niches are sufficiently different, potential competitors can co-exist by resource partitioning
Ectoparasite
Lives on the surface of its host
Endoparasite
Lives Within the tissues of its host
Malaria caused by plasmodium
An infected mosquito, acting as a vector, bites a human. 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.
Schistosomes
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 a human, entering the bloodstream.
Virus
Viruses are parasites that can only replicate inside a host cell
Viruses contain genetic material in the form of DNA or RNA, packaged in a protective protein coat
Viral life cycle stages
Viral life cycle stages: 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
RNA retroviruses use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell
Viral genes can then be expressed to form new viral particles
Transmission
Transmission is the spread of a parasite to a host
Virulence
Virulence is the harm caused to a host species by a parasite
How are ectoparasites transmitted
Ectoparasites are generally transmitted through direct contact
Endoparasites
Ectoparasites are generally transmitted through direct contact
Factors that increase transmission rates
Factors that increase transmission rates:
the overcrowding of hosts when they are at high density
mechanisms, such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacitated
Host behavior exploitation
Alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour.
Non specific defenses
Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected
Specific non specific defenses
Epithelial tissue blocks the entry of parasites; hydrolytic enzymes in mucus, saliva and tears destroy bacterial cell walls; low pH environments of the secretions of stomach, vagina and sweat glands denatures cellular proteins of pathogens
Signal molecules
This results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes.
Natural killer cells
Natural killer cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.
Specific cellular defenses
A range of white blood cells constantly circulate, monitoring the tissues
If tissues become damaged or invaded, cells release cytokines that increase 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, each possessing a receptor on its surface, which can potentially recognise a parasite antigen
Binding of an antigen to a lymphocyte’s receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte
Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells
Antibodies possess regions where the amino acid sequence varies greatly between different antibodies
This variable region gives the antibody its specificity for binding antigen
When the antigen binds to this binding site the antigen-antibody complex formed can result in inactivation of the parasite, rendering it susceptible to a phagocyte, or can stimulate a response that results in cell lysis
Memory lymphocyte cells are also formed
Antigenic variation
Antigenic variation in some parasites allows them to change between different antigens during the course of infection of a host
It may also allow re-infection of the same host with the new variant
Viral latency
Some viruses escape immune surveillance by integrating their genome into host genomes, existing in an inactive state
The virus becomes active again when favourable conditions arise
Epidemiology
Epidemiology is the study of the outbreak and spread of infectious disease
Herd immunity
The herd immunity threshold is the density of resistant hosts in the population required to prevent an epidemic
Challenges in creating a treatment or vaccine
The similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite
Antigenic variation has to be reflected in the design of vaccines
Some parasites are difficult to culture in the laboratory making it difficult to design vaccines
Treatments of LEDC
Civil engineering projects to improve sanitation combined with co-ordinated vector control may often be the only practical control strategies
Improvements in parasite control reduce child mortality and result in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development
What determines male characteristics
The SRY gene on the Y chromosome
What happens to heterogametic males (XY)
males lack most of the corresponding homologous alleles on the shorter (Y) chromosome
This can result in sex-linked patterns of inheritance as seen with carrier females (XBXb) and affected males (XbY)
X chromosome inactivation
is a process by which most of one X chromosome is inactivated.
What happens to one X chromosome in homogametic females
one of the two X chromosomes present in each cell is randomly inactivated at an early stage of development
X chromosome inactivation prevents a double dose of gene products, which could be harmful to cells
Hemaphrodites
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
Benefits of hermaphroditism
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
Environmental sex determination
Environmental sex determination in reptiles is controlled by environmental temperature of egg incubation.
How can sex change within species
Sex can change within individuals of some species as a result of size, competition, or parasitic infection
In some species the sex ratio of offspring can be adjusted in response to resource availability
How do retroviruses form DNA
They use an enzyme called reverse transcriptase which is then inserted into the genome of the host cell.
Viral genes can then be expressed to form new viral particles.
