Organisms And Evolution Flashcards
What is divergent evolution?
The development of differing life forms from a common origin.
Why is convergent evolution?
The separate evolution of similar phenotypic adaptations in lineages whose ancestors did not share these adaptations.
What random process causes evolution?
Genetic drift
What non random processes cause evolution
Natural selection and sexual selection
What is genetic drift?
The random increase or decrease in frequency of inherited traits over a number of generations.
Genetic drift has a greater effect In
Smaller populations.
What is sexual selection?
An increase in the frequency of alleles that make mating and reproduction more likely.
Absolute fitness
The ratio of frequencies of a particular genotype in one generation compared to the previous generation.
Factors that increase the rate of evolution
Higher selection pressures Shorter generation times Warmer environments Sexual reproduction Horizontal gene transfer
What is the red queen hypothesis
Both species are constantly evolving in response to changes in other species.
Benefits of asexual reproduction
Metabolic costs are lower
Production of offspring is rapid
Every member of population can reproduce
Disadvantage to sexual reproduction
Metabolic costs are higher
Reproduction rate is much slower
Disrupts successful parental genomes
What is parthenogenesis?
A process by which some animal species produce offspring asexually without needing makes for fertilisation.
Where is parthenogenesis more commonly found in?
Areas with lower partition like cooler climates.
What are homologous chromosomes?
Chromosomes of the same size, same centromere position and has the same genes at the same loci.
How does sexual reproduction increase variation?
It involves crossing over, independent assortment & combining haploid genomes from two individuals.
What is independent assortment
Homologous chromosomes are aligned in pairs irrespective of the parental origin.
What is a sessile organism?
An organism that does not move (fixed in one place).
Features of r selected organism
Smaller species
Many offspring
Lower chance of survival
Less parental investment
Features of k selected organisms
Larger
Fewer offspring
Longer lifespan
Larger parental investment
What happens in polygamy?
Each individual may mate with several others in the same reproductive season.
What happens in monogamy?
Each individual only shares gametes with one other individual.
What happens in ritualised courtship behaviours?
A specific sign stimulus from one individual produces a specific fixed-action pattern response in the other.
What is sexual dimorphism?
Differences in characteristics between two sexes of the same species.
What is reversed sexual dimorphism?
The female is larger or more brightly coloured than the Male.
What is a sneaker male?
Makes which can superficially resemble the female in appearance in order to avoid Male-Male rivalry.
What is lekking?
Communal display by groups of males in order to attract females.
What is the ecological niche?
The multidimensional summary of tolerances and requirements of a species.
What is the fundamental niche?
The niche an organism occupies when there is no interspecific competition.
What is the realised niche?
The niche an organism occupies when interspecific competition is present.
What is competitive-exclusion?
The local extinction of one species due to interspecific competition from another species.
What is resource partitioning?
Two competing species occupy different realised niches, compromising over resources so they can coexist.
What is an ectoparasite?
Parasites that live and feed on the surface of their host.
What are endoparasites?
Parasites that live within their host.
What is the definitive host?
The host in which the parasite sexually matures.
State what is meant by a narrow niche as applied to parasites.
Parasites tend to have a very narrow niche due to Hugh host specificity.
Explain what degenerate means as applied to parasites.
Parasites lack in structures and organs found in other organisms.
What is transmission?
The spread of a parasite to a host.
What is virulence?
The harm that a parasite causes to a host species.
What is the relationship between transmission and virulence.
The higher the transmission rate, the greater the virulence.
Give examples of factors that increase the transmission rates of parasites.
Overcrowding of hosts
Presence of vectors e.g mosquitoes
What is the extended phenotype?
A theory whereby the parasite modifies the hosts behaviour to increase its own transmission.
Give examples of how parasites modify their hosts for own gain.
Habitat choice e.g. ants go to top of blade of grass so they are eaten by its next host.
Anti-predator behaviour e.g. rats attracted to cats so they are eaten and parasite is infested by next host.
Give examples of physical and chemical barriers in non specific defence.
Skin, hair, mucus, tears.
Describe inflammatory response and explain it’s role in non specific defence.
When the skin is damaged, injured or infected cells can release histamine.
The histamine causes blood vessels to dilate increasing the blood flow to the affected area and increased capillary permeability.
This causes white blood cells such as phagocytes to travel to the area to allow a suitable defence or attack.
Describe the process of phagocytosis and the role of phagocytes in the process.
Phagocytes engulf parasites by forming their plasma membrane around them and pulling them in.
The parasite is then brought into the vacuole.
The vacuole fuses with the lysosome filled with digestive enzymes, which digests the parasite.
State the role of natural killer cells in non-specific defence.
Natural killed cells detect foreign antigens and cause apoptosis in pathogen infected cells.
Describe the role of phagocytes in specific defence.
The foreign antigens, previously engulfed by phagocytes are pushed back out onto the surface of the phagocyte. Therefore it is an antigen presenting cell.
Compare the role of T & B lymphocytes in specific defence.
In response to foreign antigens presented by phagocytes, B lymphocytes produce antibodies that are specific in shape to the antigen.
Explain what clonal selection is and it’s role in immunological memory.
Lymphocytes are activated when they bind to their receptors bind to their specific antigen. This causes them to divide rapidly to produce many more clones.
Discuss how endoparasites can evade detection by the hosts immune system.
Mimic hosts antigens.
Antigenic variation.
Explain how antigenic variation allows parasites to remain a step ahead of the hosts immune response.
The variation of antigens allows the parasite to evolve quicker than the hosts immune system can respond.
Define the term epidemiology.
The study of the outbreak and spread of infectious diseases.
Describe what herd immunity is.
Protection offered to non immune members of a population by sufficient numbers of immune individuals.
Define the term herd immunity threshold.
The density of resistant hosts required in a population to prevent an epidemic.
What is relative fitness?
Surviving offspring of one genotype compared with other genotypes.
How should sampling be carried out?
In a manner that minimises the impact on wild species and habitats.
What animals are quadrants used for?
Sessile organisms.
How are elusive species sampled?
Camera trap or scat sampling.
How can mobile animals be sampled?
Nets or traps
What are methods of marking?
Banding Tagging Surgical implantation Painting Hair clipping
What are forms of quantative data?
Latency
Frequency
Duration
Why is X-inactivation important?
So the cells have a single working copy of the X chromosome genes, prevents a double dose of gene products.
Absolute fitness is
Frequencies of a particular genotype in one generation compared to the next
Relative fitness is
Surviving offspring of one genotype compared to other genotypes.
Evolution is..
The change over time in frequency of alleles in the gene pool of a population.
Problems in treating parasitic disease
Some parasites are difficult to grow in culture
Drugs could harm host as host and parasite metabolism are similar
Parasite may use rapid antigen change so vaccine design would be very complex
Need to find drug which only targets parasite
What is the role of helper T cells
Stimulate b lymphocytes and cytotoxic T cells to divide rapidly
The genetic material of viruses can be
DNA or RNA
In viruses what is the DNA or RNA packaged in
A protective protein coat.
Steps of DNA virus reproduction
Virus antigens attach to host cell surface
Virus DNA inserted into the host cell and replicated by host enzymes
Virus genes are transcribed to RNA which is translated to make vital protein coats
New virus particles are assembled and burst out of host cell.
How do RNA Retroviruses reproduce
Virus antigens attach to host cell surface
Virus RNA inserted into host cell
Reverse transcriptase reads viral RNA to form DNA
New virus particles are assembled and burst out of host cell
What causes the embryo to develop into a Male?
A single gene on the Y chromosome (SRY).
What environmental factors can determine sex and sex ratio
Temperature
Size- clown fish- when female dies largest Male becomes a female.
Parisitic infection
describe meiosis I
Occurs in diploid gamete mother cells
Homologous chromosomes pair up
Chiasmata forms and crossing over occurs allowing for the recombination of new alleles
Chromosomes are lined up at equator irrespective of their parental origin
Homologous chromosomes separate to opposite ends of the cell and two non identical sister chromatids form.
Describe meiosis II
Sister chromatids separate and produce four genetically different haploid gametes
Schistosomiasis is caused by a
Endoparisitic flatworm
