Organisms and Evolution Flashcards
Sampling should be carried out in a manner that…
minimises impact on wild species and
habitats
Consideration must be given to…
rare and vulnerable species and habitats that are protected
by legislation
The chosen technique, point count, transect or remote detection must be
appropriate to
the species being sampled
Quadrats
of suitable size and shape, or transects are used for plants and other sessile or
slow-moving organisms
mobile species capture techniques…
Traps and nets
Elusive species can be sampled directly using
camera traps or an indirect method, such as
scat sampling
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
involves the identification and naming of organisms and their classification into groups based on shared characteristics
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
Familiarity with taxonomic groupings allows…
predictions and inferences to be made about
the biology of an organism from better-known (model) organisms
Model organisms are those that..
are either easily studied or have been well studied
indicator species
Presence, absence or abundance of indicator species can give information of
environmental qualities, such as presence of a pollutant
Susceptible and favoured species can be used to…
monitor an ecosystem
Methods of marking animals
banding, tagging, surgical implantation, painting and
hair clipping
The method of marking and subsequent observation must minimise the…
impact on the
study species
Some of the measurements used to quantify animal behaviour are…
latency, frequency and
duration
ethogram
behaviours shown by a species in a wild context allows the
construction of time budgets
anthropomorphism
needs to be avoided as this can lead to invalid conclusions
Evolution
is the change over time in the proportion of individuals in a population differing in
one or more inherited traits
During evolution
changes in allele frequency occur through the non-random processes of
natural selection and sexual selection, and the random process of genetic drift
Natural selection acts on…?
acts on genetic variation in populations
Populations produce
more offspring than the environment can support
Individuals with variations that are better suited to their environment tend
to survive longer
and produce more offspring, breeding to pass on those alleles that conferred an advantage
to the next generation
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
Sexual selection can be due to
male-male rivalry and female choice
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
Bottleneck effect
The bottleneck effect in biology refers to a sharp reduction in the size of a population due to environmental events, such as natural disasters (floods, fires, earthquakes) or human activity (habitat destruction, overhunting). This reduction in population size drastically limits genetic diversity, as only a small, random subset of individuals survives to repopulate the species.
Founder effect
type of genetic drift that occurs when a small group of individuals from a larger population establishes a new population in a new area. Because the founding members are a small sample of the original population, they carry only a limited subset of the genetic diversity from the original population. This reduced genetic diversity can lead to a population that is genetically different from the original one, even if the new population grows in size over time.
A gene pool is altered by genetic drift because…
certain alleles may be under-represented or
over-represented and allele frequencies change
Where selection pressures are strong, the…
rate of evolution can be rapid
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. The HW principle can be used to determine whether a change in allele frequency is
occurring in a population over time
Fitness
an indication of an individual’s ability to be successful at surviving and reproducing. It refers to the contribution made to the gene pool of the next generation by individual
genotypes
Absolute fitness
the ratio between the frequency of individuals of a particular genotype before and after selection
Relative fitness
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
Co-evolution
the process by which two or more species evolve in response to selection
pressures imposed by each other
types of symbiotic interactions
Mutualism, commensalism, and parasitism
What is a cost of sexual reproduction?
Males unable to produce offspring
Only half of each parent’s genome is passed onto offspring, disrupting successful parental genomes.
What is the primary benefit of sexual reproduction?
Increased genetic variation in the population
How does genetic variation contribute to the survival of sexually reproducing organisms?
Provides the raw material required for adaptation
What hypothesis explains the persistence of sexual reproduction?
The Red Queen hypothesis
What type of interactions may select for sexually reproducing hosts?
Co-evolutionary interactions between parasites and hosts
How does sexual reproduction affect susceptibility to parasites?
Reduces the chances that all offspring will be susceptible
What is a key advantage of asexual reproduction?
Whole genomes are passed on from parent to offspring
In what situations is maintaining the parent’s genome advantageous?
In very narrow, stable niches or when re-colonising disturbed habitats
What are examples of asexual reproduction in eukaryotes?
Vegetative cloning in plants and parthenogenesis in lower plants and animals
What is a benefit of asexual reproduction regarding offspring production?
Offspring can be reproduced more often and in larger numbers
Where is parthenogenesis more common?
In cooler climates or regions of low parasite density or diversity
What is a limitation of asexually reproducing populations?
Not able to adapt easily to changes in their environment
What allows some degree of variation in asexually reproducing populations?
Mutations can occur
What mechanisms do organisms that reproduce asexually often have?
Mechanisms for horizontal gene transfer
What are examples of organisms that utilize horizontal gene transfer?
Bacteria and yeasts
What is meiosis?
The division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte
Meiosis is essential for sexual reproduction.
In diploid cells, how do chromosomes typically appear?
As homologous pairs
Homologous pairs consist of one chromosome from each parent.
What occurs during meiosis I?
The chromosomes condense, homologous chromosomes pair up, and chiasmata form.
Chiasmata are points of contact where genetic material can be exchanged.
What are chromatids?
Genetically identical copies of a chromosome attached at the centromere
Each replicated chromosome consists of two sister chromatids.
What is crossing over during chiasmata?
The exchange of sections of DNA between non-sister chromatids of a homologous pair
This process increases genetic diversity.
What is the significance of the random orientation of homologous chromosomes at the equator?
It contributes to genetic variation in gametes
This randomness is a key feature of meiosis.
What happens to homologous chromosomes during meiosis I?
They are separated and move towards opposite poles
This separation reduces the chromosome number by half.
What occurs after meiosis I?
Cytokinesis occurs and two daughter cells form.
Each daughter cell is haploid.
What happens during meiosis II?
The sister chromatids of each chromosome are separated
Meiosis II resembles mitosis but starts with haploid cells.
What determines the sex of birds, mammals, and some insects?
The presence of sex chromosomes
In mammals, the SRY gene on the Y chromosome is crucial for male development.
Which gene on the Y chromosome is responsible for male characteristics in most mammals?
SRY gene
What type of males lack most corresponding homologous alleles on the Y chromosome?
Heterogametic (XY) males
What can result in sex-linked patterns of inheritance?
The lack of homologous alleles in heterogametic males
Examples include carrier females (XBXb) and affected males (XbY).
What happens to one of the X chromosomes in homogametic females (XX)?
It is randomly inactivated at an early stage of development
Why is X chromosome inactivation important?
It prevents a double dose of gene products, which could be harmful to cells
Why are carriers less likely to be affected by deleterious mutations on X chromosomes?
Because of X chromosome inactivation
What is the result of random X chromosome inactivation in tissues?
Half of the cells will have a working copy of the gene in question
What are hermaphrodites?
Species that have functioning male and female reproductive organs in each individual
What do hermaphrodites produce?
Both male and female gametes
What is the benefit of being a hermaphrodite?
No requirement for a partner of the opposite sex if encountering a partner is rare
In some species, what factors determine sex and sex ratio?
Environmental factors rather than genetic factors
Can sex change within individuals of some species?
Yes, due to size, competition, or parasitic infection
How can the sex ratio of offspring be adjusted in some species?
In response to resource availability
What is the primary difference in investment between males and females in reproduction?
Greater investment by females
Females typically invest more energy and resources in producing eggs compared to males producing sperm.
How does parental investment affect the probability of young survival?
Parental investment is costly but increases the probability of production and survival of young
Investing resources in offspring can lead to higher chances of their survival and reproductive success.
What are r-selected organisms characterized by?
r-selected organisms are characterized by a high number of offspring and low parental investment
These organisms often thrive in unstable environments.
What are K-selected organisms characterized by?
K-selected organisms are characterized by fewer offspring and high parental investment
These organisms tend to thrive in stable environments.
In what type of environments does r-selection typically occur?
r-selection tends to occur in unstable environments
In these environments, species have not reached their reproductive capacity.
In what type of environments does K-selection typically occur?
K-selection tends to occur in stable environments
These environments allow for more investment in fewer offspring.
External fertilisation Benefits
Very large numbers of offspring produced.
External fertilisation costs
Many gametes are predated or not fertilised.
no/limited parental care
few offspring survive
Internal fertilisation costs
mate needed which requires energy expenditure
requires direct transfer of gametes from one partner to another
internal fertilisation benefits
increased chance of successful fertilisation
fewer eggs needed
offspring retained internally for protection
higher offspring surv rate
What are mating systems based off of?
how many mates an individual has during one breeding season
polygamy
individuals of one sex having more than one mate.
What are the two types of polygamy?
polygyny and polyandry
polygyny
one male mates exclusively with a group of females
polyandry
one female mates with a number of males in the same breeding season
monogamy
involves the mating of a pair of animals to the exclusion of anothers
What are courtship rituals?
a set of display behaviours which animals use to attract a mate. These are common in birds and fish
successful courtship in birds and fish can be a result of…?
species-specific sign stimuli and fixed action responses
What does sexual selection select?
characteristics that have little survival benefit for the individual , but increase their chance of mating.
Result of sexual selection
sexual dimorphism
sexual dimorphism
females are generally inconspicuous, with bland colours and lacking ornate structures.
Reversed sexual dimorphism
females are conspicuous and males are inconspicuous.
what does female choice involve?
females assessing honest signals of the fitness of males.
What are honest signals?
indicates favourable alleles that increase the chances of survival of offspring or a low parasite burden.
What is lekking?
some birds species display lekking behaviour. Involves males of the species gathering to display at a lek, where female choice occurs.
What area of a lek do satelite males occupy
fringes
how is access to females for mating increased.
success in male rivalry through conflict
Niche
a multi-dimensional summary of tolerances and requirements of a species
Fundamental niche
that it occupies in the absence of any interspecific competition.
realised niche
the range that they have been fittest in comparison to other organisms present.
What is competitive exclusion?
As a result of interspecific competition. Occurs where the niches of two species are so similar that one declines to local extinction.
When species realised niches are sufficiently different…
potential competitors can co-exist by resource partitioning.
Parasitism
A symbiotic interaction between a parasite and its host (+/-). A parasite gains benefit in terms of nutrients at the expense of its host.
Reproductive potential of a parasite
unlike in a predator-prey relationship, the reproductive potential of the parasite is greater than that of the host.
Most parasites have a narrow realised niche because…
they are host specific
As the host provides so many of the parasite’s needs, many parasites are degenerate…
they lack in structures and organs found in other organisms.
Ectoparasites vs endoparasites
ectoparasites live on the surface of their host, whereas an endoparasite lives within the tissues of its host.
What is a Vector?
plays an active role in the transmission of the parasite and may also be a host.
Malaria is caused by
Plasmodium.
Schistosomiasis is caused by
schistosomes
What are viruses
parasites which can only reproduce in host cells. some virsuses are surrounded by a phospholipid membrane derived from host cell materials.
What do viruses contain?
genetic material in the form of DNA or RNA, packaged in a protein coat.
What does the outer surface of viruses contain?
antigens that a host cell may or may not be able to detect as foreign.
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 which 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
What is transmission
the spread of a parasite to the host
what is Virulence
the harm caused to a host species by a parasite
How are ectoparasites transmitted
direct contact
How are endoparasites transmitted
Endoparasites of the body tissues are often transmitted by vectors or by consumption of intermediate hosts
Factors increasing 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
How do parasites maximise transmission rates?
Host behaviour is often exploited and modified by parasites to maximise transmission
The host behaviour becomes part of …
the extended phenotype of the parasite
How do parasites benefit the parasite growth, reproduction or transmission?
Parasites often suppress the host immune system and modify host size and reproductive rate in ways that benefit the parasite growth, reproduction or transmission
examples of Non-specific defences
Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected with viruses are examples of non-specific defences
specific cellular defences
A range of white blood cells constantly circulates, 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
Endoparasites mimic..
host antigens to evade detection and modify host immune response
to reduce their chances of destruction
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
Some viruses escape immune surveillance by?
integrating their genome into host genomes,
existing in an inactive state known as latency. The virus becomes active again when favourable conditions arise
Epidemiology
is the 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
Why is it difficult to find a drug that only targets the parasite?
The similarities between host and parasite metabolism makes it difficult to find drug
compounds that only target the parasite
What has to be reflected in the design of vaccines?
Antigenic variation
Why is it difficult to make some vaccines?
The parasites are difficult to culture
Challenges arise where parasites spread most rapidly as a result…
overcrowding or tropical climates. These conditions make co-ordinated treatment and control programs difficult to achieve
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 enviroment is parthenogenesis most likely to occur in?
cool climates with low parasite density
