Unit 2 Flashcards
Examples of hazards and what should be done about them
uneven/ challenging terrain, weather
conditions and isolation, should be identified and risk assessed
how should sampling be carried out and what should be given consideration?
in a manner that minimises impact on the wild species and habitats, consideration given to rare and vulnerable species and habitats
techniques for sampling wild organisms
transects (a line along which different samples are taken), point counts (counts of organisms seen and heard from a stationary point), remote detection (camera traps), quadrats, camera traps and scat sampling (indirect)
how can chosen techniques be appropriate for species being sampled?
-quadrats of suitable size and shape are used for sessile and slow-moving organisms
- capture techniques for mobile species
- elusive species can be sampled directly using
camera traps or indirectly using scat sampling
how can a sample be identified?
classification guides, biological keys or
analysis of DNA or protein
what does familiarity with taxonomic groupings allow?
predictions and inferences to be made between the biology of an organism and better-known (model) organisms
what does genetic evidence reveal?
relatedness obscured by divergent or convergent evolution
three domains
archaea, bacteria, eukaryota
plant kingdom main divisions
mosses, liverworts, ferns, flowering plants, conifers
phyla of the animal kingdom
Chordata, Nematoda, Arthropoda, Mollusca, Platyhelminthes
chordata
sea squirts and vertebrates
Arthropoda
joint-legged invertebrates: segmented body
typically with paired appendages
Nematoda
round worms: very diverse, many parasitic
Platyhelminthes
flatworms: bilateral symmetry, internal organs but no body cavity, many parasitic
Mollusca
molluscs: diverse, many with shells
what are model organisms from within all taxonomic groups used for?
to obtain information that can be applied to species that are more difficult to study directly
Model organism that have been important in the advancement of modern biology
- bacterium- E.coli
- flowering plant- Arabidopsis thaliana
- nematode- C. elegans
- arthropod- Drosophila melanogaster
- chordates- mice, rats and zebrafish
indicator species
presence, absence or abundance can give information about enviromental qualities such as presence of pollutant
Mark and recapture
method for estimating population size
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 individuals in this second sample are recaptures (R) then the total population N = (MC)/R, assuming that all individuals have an equal chance of capture and that there is no immigration or emigration.
methods of marking
banding, tagging, surgical implantation, painting and hair clipping
method of marking and tagging must
minimise the impact on the study species
ethogram
recording of all observed behaviors shown by a species over a period of time
what does an ethogram of the behaviours shown by a species in a wild context allow?
construction of time budgets- shows % of time spent on certain activities
measurements taken for ethogram
latency (time taken for animal to respond to a particular stimulus), frequency and duration of certain behaviours and activites
anthromorphism
when animals are credited with human emotions and qualities, must be avoided
evolution
change over time in the proportion of individuals in a population differing in one or more inherited traits
how can evolution occur?
random processes of genetic drift or non-random processes of natural and sexual selection
genetic drift
random change in how frequently a particular allele occurs within a population
why is genetic drift is more important in small populations?
alleles are more likely to be lost from the gene pool
natural selection and sexual selection cause
certain alleles to occur more frequently within a population because they confer a selective advantage
mutation
causes variation in traits to arise, original source of novel sequences of DNA, most are harmful but rarely can be beneficial to fitness of an individual
absolute fitness
ratio of frequencies of a particular genotype from one
generation to the next
F1/P
relative fitness
ratio of surviving offspring of one genotype compared
with other genotypes
absolute fitness of one genotype/ absolute fitness of most successful genotype
As organisms produce more offspring than the environment can support
those individuals with variations that best fit their environment are the ones most likely to survive and breed. Through inheritance, these favoured traits are therefore likely to become more frequent in subsequent generations
selection pressures
environmental factors that may reduce the reproductive success in a population and thus contribute to evolutionary change or extinction
where selection pressures are high
rate of evolution can be rapid
rate of evolution can be increased by
shorter generation times, warmer environments, the sharing of beneficial DNA sequences between different lineages through sexual reproduction and horizontal gene transfer
coevolution is frequently seen between
pairs of species that demonstrate a symbiotic relationship- interact frequently or closely
examples of pairs of species that undergo coevolution
herbivores and plants, pollinators and plants, predators and their prey, and parasites and their hosts
In co-evolution, a change in the traits of one
species acts as
a selection pressure on the other species
what is the Red Queen hypothesis and what does it exemplify?
evolution merely permits organisms to maintain their current success, exemplifies the ongoing co-evolution
between a parasite and host
fitness with respect to the coevolution of parasite and host
Hosts better able to resist and tolerate parasitism have greater fitness
Parasites better able to feed, reproduce and find new hosts have greater fitness
sexual reproduction
involves fusion of two gametes from two different parents producing dissimilar offspring
asexual reproduction
involves making exact copies of one parent
disadvantages of sexual reproduction
half of the population (males) are unable to produce offspring, only half of each parent’s genome passed onto offspring disrupting successful parental genomes
advantage of sexual reproduction
increase in genetic variation in the population
advantage of genetic variation
provides the raw material required to continue
adapting in the Red Queen’s arms race between parasites and their hosts
when is asexual reproduction a successful reproductive strategy?
very narrow stable niches or when recolonising disturbed habitats
examples of asexual reproduction in eukaryotes
vegetative cloning in plants and parthenogenic animals that lack fertilisation
where is parthenogenesis common?
cooler climates that are disadvantageous to parasites or regions of low parasite density/diversity
what do organisms that reproduce asexually have mechanisms for?
horizontal gene transfer between individuals, such as the plasmids of bacteria and yeast
Homologous chromosomes are pairs of chromosomes of
methe same size, same centromere position and with the same genes at the same loci
meiosis
mechanism by which variation is increased through the production of haploid gametes by meiosis in gamete mother cells
meiosis 1
- interphase- DNA replication to form identical chromatids
- homologous chromosomes pair up and line up along the equator of the cell
- random crossing over at the chiasmata resulting in exchange of DNA between homologous pairs and recombination of alleles of linked genes
- independant assortment- homologous pairs have completely random positions relative to other pairs, separation of parental chromosomes irrespective of their maternal and paternal origin- results in gametes with varying combos of maternal and paternal chromosomes
- # of possible combinations is worked out by 2^n
- homologous chromosomes are separated by spindle fibres and are pulled to opposite ends of the cell
- the cell divides, forming two haploid daughter cells
meiosis 2
sister chromatids are separated by spindle fibres and four haploid gametes (often genetically dissimilar) are formed
outcomes of haploid cells produced by meiosis
In many organisms, gametes are formed directly from the cells produced by meiosis. In other groups, mitosis may occur after meiosis to form a haploid organism; gametes form later by cellular differentiation.
linked genes
genes on the same chromosome
relationship between distance and frequency of recombination
the greater the distance betweeen linked genes, the greater the chances of crossing over and greater the frequency of recombination
hermaphrodite
organisms with both male and female reproductive organs
factors that may affect sex ratio of offspring
evironmental conditons (crocodiles) and resource availablity
things that may cause an organism to change sex
size, competition or parasitic infection
in which organisms are sex chromosomes X and Y?
live bearing mammals and some insects including Drosophila
what determines development of maleness in many mammals?
a gene on the Y chromosome
sex-linked patterns of inheritance in males
In live-bearing mammals, the heterogametic (XY) male lacks homologous alleles on the smaller (Y) chromosome. This can result in sex-linked patterns of inheritance as seen with carrier females (XBXb) and affected males (XbY)
why are affected males more likely to have a recessive condition than a female?
females would need two copies of the recessive allele to be affected, whereas males only need one
how are harmful effects prevented in female carriers with one affected gene?
the portions of the X chromosome that are lacking on the Y chromosome are randomly inactivated in one of the homologous X chromosomes in each cell. This effect prevents a double-dose of gene products, which could be harmful to cells.
why are carrier females less likely to have any deleterious mutations on X chromosomes?
Carriers are less likely to be affected by any deleterious mutations on these X chromosomes
as the X-chromosome inactivation is random, half of the cells in any tissue will have a working copy of the gene in question.
number and energy store of sperm vs egg
sperm are far more numerous than eggs but due to presence of energy store, eggs are much larger and fewer
what gender has the largest sexual investment?
females therefore lower chance of reproductive success and passing on genes
methods that sessile organisms use to increase reproductive success
asexual reproduction, hermaphroditism, mass release of gametes, very long penises
internal fertilisation
fusion of egg and sperm inside the body, necessary when no external moisture is available, egg in protective shell, requires highly advanced reproductive systems and behavioural synchronisation of sexes
external fertilisation
fusion of egg and sperm outside the body, in aquatic environments, uncertain method of fertilisation, vast number of sperm and egg released at the same time, timing is crucial to ensure sperm and egg meet
parental investment
costly in terms of energy but increases the probability of production and survival of young, level of parent care will depend on number of offspring produced and environment
r-selected species
unstable environment, low energy cost, many offspring produced, short life expectancy, type III survivorship pattern ( most die within a short time)
K-selected species
stable environment, high energy cost, few offspring porduced, long life expectancy, type I or II surviorship pattern (most live to near maximum life span)
how are organisms classed as r- or K-selected species?
based on reproductive strategy and life history, organisms can sometimes display traits of both groups
monogamy
one male + one female, long lasting pairs, cooperate in raising offspring
polygamy
one animal has more than one mate
polygny
one male + multiple females (red deer), dominant male passes on fit alleles, limited male choice, heavy competition
polyandry
one female + multiple males (honey bee)
fertilisation assurance, increased parental care, reduced male competition
increased exposure to diseases, increased predation risk
polygynandry
multiple males + multiple females (chimpanzees)
greater genetic diverity. less need for male competition, greater protection and nurture for young
sexual dimorphism
males and females of the same species have very different physical appearance, often in terms of colour and size - this is a result of sexual selection
General appearance of males and females
Females are generally inconspicuous to avod predation and increase survival chances of her offspring, males have more conspicuous markings, structures
and behaviours to display during courtship and territorial behaviour
female choice in courtship
involves females assessing honest signals of the fitness of males, can be in terms of good genes and low parasite burden
satellite males
sneaking males
reverse sexual dimorphism
normally inconspicuous females are larger or more ornate than males
male-male rivalry
sees larger males, often with appendages used a
weapons, having greater success at finding a mate as they can increase access to females through conflict
sneaking
smaller males employ sneaking behaviour and see equal success at gaining access to females
lekking
males of a species, usually birds, gather in a display area (lek) and display, females attend the lek and choose a mate
sign stimuli
trigger that provokes a behavioural response
fixed action pattern
series of sign stimuli followed by responses, instinctive
what can successful courtship in birds and fish be a result of?
species-specific sign stimuli that bring about a fixed action pattern response
imprinting
irreversible developmental processes that occur during a critical time period in young birds which may influence mate choice later in life
parasite
a symbiont that gains benefit in terms of nutrients at the expense of its host
difference between a predator-prey relationship and parasite-host relationship
the reproductive potential of the parasite
is greater than that of the host
ecological niche
multidimensional summary of tolerances and requirements of
a species
parasite niche and structures
Parasites tend to have a narrow niche as they are very host specific. As the host provides so many of the parasite’s needs, many parasites are degenerate, lacking in structures and organs found in other organisms.
ectoparasite
lives on the surfacer of a host
endoparasite
lives inside the host
definitive host
the organism on or in which the parasite reaches sexual maturity
intermediate hosts
may be required for the parasite to complete its life cycle
vector
plays an active role in the transmission of the parasite and may also be a host
fundamental niche
niche that it occupies in the absence of any interspecific competing influences
realised niche
niche that is occupied in response tointerspecific competition
competitve exclusion
As a result of interspecific competition and where the niches of two species are so similar that one declines to local extinction
how can potential competitors can co-exist where realised niches are sufficiently different?
resource partitioning
transmission
the spread of a parasite to a host
virulence
the harm caused to a host species by a parasite
factors that increase transmission rate
the overcrowding of hosts at high density; mechanisms that allow the parasite to spread even when infected hosts are incapacitated, such as vectors and waterborne dispersal stages; exploited and modified host behaviour
how can the host behaviour become part of the extended phenotype of the parasite?
through the alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour,
how can parasites impact hosts in order to benefit the parasite growth reproduction or transmission?
by suppressing the host immune system and
modifying host size and reproductive rate
what do sexual and asexual phases in parasites allow?
rapid evolution and rapid build-up of parasite population.
distribution of parasites across hosts
not uniform
non specific defences of mammal
physical barriers- skin, hair
chemical secretions- mucus, tears
inflammatory response- increase blood flow + WBCs allowing suitable defence or attack
phagocytes- WBCs that engulf and digest pathogens
natural killer cells destroying abnormal cells- detect signals from stressed cells and induce apoptosis
specific cellular defence in mammals
- immune surveillance by white blood cells- ability to respond to a foreign antigen before it enters the body
- clonal selection of T lymphocytes
- T lymphocytes targeting immune response and destroying infected cells by inducing apoptosis
- phagocytes presenting antigens to lymphocytes
- clonal selection of B lymphocytes
- production of specific antibody by B lymphocyte clones
- long term survival of some members of T and B lymphocyte clones to act as immunological memory cells
epidemiology
study of the outbreak and spread of infectious disease
herd immunity threshold
the density of resistant hosts in the population required to prevent an epidemic
how do endoparasites evade detection and reduce their chances of destruction?
Endoparasites mimic host antigens to evade detection by the immune system, and modify host-immune response to reduce their chances of destruction
antigenic variation
allows some parasites to evolve faster than the host immune system can respond to the new antigens
common parasites include
protists, platyhelminths, nematodes, arthropods, bacteria and viruses
parasites that need more than one host to complete their life cycle
Plasmodium which causes the human disease malaria and the platyhelminth, Schistosoma, which causes schistosomiasis in humans
how are ectoparasites and endoparasites of the main body cavities, such as the gut, generally transmitted?
through direct contact or by consumption of secondary hosts
how are endoparasites of the body tissues transmitted?
through vectors
parasites that can complete their life cycle within one host
some endoparasitic amoebas and ectoparasitic arthropods, bacteria and viruses
human diseases caused by bacteria and viruses
tuberculosis (bacteria), influenza and HIV (viruses)
viruses
infectious agents that can only replicate inside a host cell
structure of a virus
viruses contain genetic material in the form of DNA or RNA, packaged in a protective protein coat.
The outer surface of a virus contains antigens that a host cell may or may not be able to detect as foreign
retroviruses and how they reproduce
Viruses that contain RNA as genetic material rather than DNA.
Retroviruses use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell. This virus gene forms new viral particles when transcribed
challenges of treatment and control of parasites
Some parasites are difficult to culture in the laboratory
Rapid antigen change has to be reflected in the design of vaccines
The similarities between host and parasite
metabolism makes it difficult to find drug compounds that only target the parasite
a practical solution to parasitism
Civil engineering projects to improve sanitation combined with coordinated vector control
where do challenges in parasitism most likely arise?
where parasites spread most rapidly as a result of overcrowding or tropical climates
what can improvements in control and treatment of parasites result in
can reduce child mortality and result in population-wide improvements in child development and intelligence as individuals have more resources for growth and development
Sampling methods
Random sampling - individuals are randomly selected from the larger population
Stratified sampling - one large population may be divided up into smaller sub-populations and then individuals are then randomly selected from each sub-population.
Systematic sampling - may be taken at regular intervals, e.g. every 2 metres along the transect.
