Unit 4 SAC 2 Flashcards
population definition
members of one species living in one region at a particular time
gene pool definition
sum total of genetic information present in a population
genotype definition
The total set of this genetic information in an individual
genetic diversity definition
the amount of genetic variation there is within a population’s gene pool
allele frequency definition
the proportion of a specific allele in a population
how to calculate allele frequency
- times the # of organisms by 2 (for 2 alleles) to gain total number of alleles in the pool
- write the number of alleles for each type (10 of a, 6 of A)
- divide each # of alleles by the total alleles in the pool for the allele frequency of that allele.
what are the 3 agents that can cause allele frequency changes
- changes in environmental selection pressures leading to natural selection
- genetic drift
- gene flow
what are environmental selection pressures
external agents which influence the ability of an individual to survive in their environment
what are the 3 categories of environment selection pressure
- physical agents
- chemical agents
- biological agents
example of physical agents
climate change
example of chemical agents
pollutants in soil or water
example of biological agents
predation
what is natural selection
a process in which organisms better adapted for an environment are more likely to pass on their genes to the next generation
what is ‘fitness’
the ability to survive and pass genetic material on to the next generation
what is selective advantage
relative higher genetic fitness of a phenotype compared with other phenotypes controlled by the same gene
what are the 4 mechanisms of natural selection
- There is variation within the population’s gene pool.
- struggle for all individuals in the gene pool to survive. Environmental selection pressures act upon the population
- Individuals that are better adapted to their environment are more likely to survive and reproduce, passing their alleles on to the next generation
- The alleles that allow for survival will be inherited by subsequent generations and they can increase in frequency in the gene pool over time
what is genetic drift
random changes, unpredictable in direction, in allele frequencies from one generation to the next owing to the action of chance events
what are the 2 subtopics of genetic drift
- bottleneck effect
- founder effect
what is bottleneck effect
chance effects on allele frequencies in a population as a result of a major reduction in population size
what is founder effect
chance effects on allele frequencies in a population that is formed from a small unrepresentative sample of a larger population
3 examples of how bottleneck effect can occur
- a natural disaster
- a new disease to which the population has not previously been exposed
- human activity, such as destruction of habitat or large scale poaching.
gene flow definition
the movement of individuals and their genetic material between populations
what are the 2 ways gene flow can happen
- immigration
- emigration
what is immigration
the movement of individuals and their alleles into a population, and thus into a gene pool
what is emigration
the movement of individuals and their alleles out of a population, and thus out of a gene pool
what does natural selection do to genetic diversity
decreases it
what does gene flow do to genetic diversity
increases it
what does genetic drift do to genetic diversity
decreases it
what does bottleneck effect do to genetic diversity
decreases it
what does founder effect do to genetic diversity
decreases it
what does mutations do to genetic diversity
increases it
what is a mutation
a permanent alteration in the DNA sequence of a gene that leads to the formation of new alleles
what are mutagens
chemical or physical agent that can cause mutation in DNA
what are 3 examples of causations of mutations
- radiation (x-rays)
- chemicals (benzene)
- pathogenic (bacteria)
what has to happen to the mutation for it to come about (and in future populations)
it is first necessary that the mutation occur in the germline of an organism so that it may be passed to the next generation.
what are the 3 types of traits mutations can give
- advantageous
- neutral
- disadvantageous
what are point mutations
a mutation that affects a single nucleotide
what are the 2 types of point mutations
- substitution (silent, nonsense, missense)
- frameshift (insertion, deletion)
what are the 2 types of point frameshift mutations
- insertion
- deletion
what are the 3 types of point substitution mutations
- silent
- nonsense
- missense
what are silent mutations
a type of mutation in which a single base change does not change the amino acid and final protein expressed
why are silent mutations possible
because DNA is degenerate, meaning multiple codons can code for the same amino acid
what are nonsense mutations
a type of mutation in which a single base change leads to a STOP signal being received, resulting in a truncated protein
what are missense mutations
a type of mutation in which a single base change leads to the change in the amino acid translated in the protein chain
what are the 2 types of missense mutations
- conservative
- non-conservative
what is a conservative missense mutation
a type of missense mutation in which the substituted amino acid is similar in properties to the initial amino acid
what is a non-conservative missense mutation
a type of missense mutation in which the substituted amino acid is very different in properties to the initial amino acid
what are frameshift mutations
type of mutation in which, as a result of insertion or deletion of a base, all codons from that point are affected
what are insertion mutations
An insertion mutation occurs when one nucleotide base is added to a DNA strand
what is a deletion mutation
A nucleotide deletion also causes a frameshift with all bases from the point of the deletion being moved back by one position to compensate for the deletion
what are the 4 types of block mutations
- deletion of part of a chromosome
- duplication or gain of part of a chromosome
- translocation between non-homologous chromosomes
- inversion (when a segment of a chromosome rotates through 180 degrees)
what happens in translocation of homologous chromosomes
part of the chromosome will join to another one
what is polyploidy
the entire genome is replicated (so instead of 2 of each chromosomes there may be 3 of every chromosome).
what is aneuploidy
the loss or gain of a single chromosome
what are some reason for why having low genetic diversity is not favourable
(2)
- limit the population’s ability to adapt to changing environmental conditions,
- can make them vulnerable to becoming susceptible to disease and even to becoming extinct
what is artificial selection
the process by which humans breed animals or plants in such a way to increase the proportion of chosen phenotypic traits
what is a selective breeding program
a process of mating that is not random, but uses parents chosen by the breeder on the basis of particular phenotypic characteristics that they display
what are the 4 steps in the mechanism of artifical selection
- There is variation within the population’s gene pool.
- Humans select individuals with a desirable trait.
- These individuals breed and pass their alleles on to the next generation.
- The alleles that lead to the desired phenotype will be inherited by subsequent generations and they can increase in frequency in the gene pool over time.
what can artificial selection do (negatively)
can favour features that are disadvantageous for survival and reproduction and would be selected against in the wild (causing difficulty to survive)
what are antibiotics
a class of antimicrobial drug used in the treatment and prevention of bacterial infections that act either by killing pathogenic bacteria or by inhibiting their growth
what are the 3 consequences of rapid genetic change of pathogens
- bacterial resistance
- antigenic drift (viruses)
- antigenic shift (viruses)
what is bacteria mainly becoming resistant to (that is not good)
antibiotics, because of the selection pressure of the antibiotics being present
what are 3 examples of why bacterial resistance increases
- poor hygiene (more bacteria present)
- not finishing antibiotic course
- over-prescribing of antibiotics
what are the consequences of bacteria becoming resistant of antibiotics
Diseases which could once be treated with a dose of antibiotics can now be life-threatening to individuals with an antibiotic-resistant strain of infection because the bacteria can continue to reproduce in the body.
what is antigenic shift
Antigenic shift occurs when two or more strains of a virus combine to form a new strain of the virus with antigens from each of the original strains.
what is antigenic drift
Antigenic drift is when a point mutation alters a virus’s nucleic material, resulting in small changes to its antigens.
what are the consequences of antigenic drift occurring to a virus
there will be a partial immune response (because of the memory B cells, creating antibodies)
what are the consequences of antigenic shift
Organism has no memory of pathogen so time will be required for adaptive response (illness is given)
why cannot vaccines be given to things such as influenza virus
because of antigenic shift and drift occurring changing the genetic material, so the vaccine needs to be changed regularly to combat this
what are the 3 types of fossils
- physical
- trace
- biosignatures
what are physical fossils
the remains of all or part of the structures of organisms, such as bones, teeth or leaves
what are 3 ways physical fossils are commonly formed as
- mineralised fossils
- fossils impressions
- preserved organism
what are mineralized fossils
a physical fossil formed when the organic material of the structure is replaced by minerals
what are fossil impressions
a physical fossil formed when the organic matter has disappeared but the organism has left an impression of its structure
what are preserved organisms
a physical fossil formed when an organism is completely preserved in a substance such as amber, ice or tar
what are trace fossils
preserved evidence of the activities of organisms, such as footprints, tooth marks, tracks, burrows and coprolite
what are biosignatures
chemical or physical traces that can be inferred to have resulted from the action of life forms
what is an example of biosignatures
corrosion pits in rocks caused by chemosynthetic microbes
what are macroscopic fossils
a fossils that is of a size that is visible to the unaided eye
what are microscopic fossils
very small fossils of a size that can only be studied using a microscope
what is fossilisation
process of preserving parts of organisms that lived in the geological past
what are the 3 broad conditions to allow fossilisation to occur
- the remains are rapidly buried in sediments after death
- continued deposits of sediments bury it more and more deeply
- Over time the rock is eroded, uplifted through the movement of tectonic plates or excavated by palaeontologists so that the fossil is exposed
what are good climate conditions for fossils
- very cold environment
- low oxygen environments
what is faunal succession
the principle that fossilised fauna and flora in sedimentary rock strata are arranged vertically in a specific order
what are index fossils
fossils of geologically short-lived species that are widely distributed but are found in a restricted depth of rock strata
what are index fossils used for
to define a period of geological time
what are transitional fossils
the fossilised remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group
what are the 2 dating methods for fossils
- absolute dating
- relative dating
what are 2 methods to gain the relative age of fossils
- use of index fossils
- use of stratigraphic method (or faunal succession)
what is the stratigraphic method
the method of obtaining the relative age of an object by its position within a given sequence of rock strata
what could be said about the lowest rock strata level
it is the oldest
what is the most important method for estimating the absolute age of fossils
radiometric dating technique
what is the radiometric dating technique
a technique for obtaining an absolute age that depends on the known rate of decay of a radioactive parent isotope to a stable daughter product
what are isotopes
the different forms of an element which differ in the number of neutrons
how does the radiometric dating technique work?
- The radioactive isotopes, which can be called ‘parents’, spontaneously decay or break down over time to form stable ‘daughter’ products.
- The rate of the decay is specific for each radioactive isotope. This is usually measured in terms of half-life, the time taken for half the original radioactive isotope to decay.
what is an example of radiometric dating
carbon-dating
what is speciation
process of formation of new species
what are the 2 methods of isolation
- pre-zygotic isolation
- post-zygotic isolation
what is pre-zygotic isolation
barriers that prevent an organism from finding and securing a mate
what is post-zygotic isolation
barriers that prevent a fertile offspring developing after mating
what is an example of prezygotic isolation
geographic isolation (one species on top of mountain, compared to the bottom, unlikely to meet)
what is an example of post-zygotic isolation
incompatibility of gametes
what 4 processes must occur to allow for speciation
- variation
- isolation
- selection
- genetic divergence
what is variation
differences exhibited among members of a population owing to the action of genes
what is selection
the process in which a variant is more advantageous under certain selective pressures, enhancing its chance of survival and reproduction
what is genetic divergence
when two or more populations accumulate genetic changes, leading them to eventually be reproductively isolated
what are the 7 steps for speciation to occur
- variation appears in population
- breeding in population becomes isolated
- different characteristics emerge (from genetic drift, mutation or environmental pressure) to gain genetic divergence
- the environment changes and the organisms that are best suited survive
- survivors reproduce these traits to offspring
- the frequency of these genes rise
- the isolated population becomes quite different (new population)
what are the 2 types of speciation
- allopatric
- sympatric
what is allopatric speciation
speciation that occurs between two populations that are geographically isolated
what is sympatric speciation
speciation that occurs between two populations that have no geographical barrier between them
what is an example of allopatric speciation
Galapagos finches
what are the 3 steps in allopatric speciation
- physical barrier separates the population (geographically isolated), and no gene flow occurs (begin to mutate differently)
- different environmental selection pressures appear (different phenotypes being selected by natural selection or genetic drift)
- over time they become new species and reproductively isolated
what are the 3 steps in sympatric speciation
- population isolated by pre-zygotic isolation barrier (other than geographic isolation, such as temporal or behavioural isolation) and some gene flow occurs
- Over many generations, genetic divergence occurs. Eventually the isolated populations respond differently to environmental selection pressures
- change significantly over time. become reproductively isolated and new species
what is reproductively isolated
the inability of species to breed and produce fertile offspring
what is an example of sympatric isolation
Howea palms trees
what are the 4 types of evidence to show relatedness
- structural morphology
- molecular homology
- biogeography
- developmental biology
what is structural morphology
the process of comparing similarities in body structures to infer relatedness
what is molecular homology
the process involved in comparing similarities in molecular structures to infer relatedness, with a particular focus on DNA and amino acid sequences
what is developmental biology
the process of comparing embryos of different species to infer relatedness
what is biogeography
geographical distribution of species
what are homologous structures
structures of organisms that have evolved from a common ancestor to have possible differences in form and function but retain similarities in structure
what are vestigial structures
non-functional structures that are remnants of functional structures in ancestral species
what are 2 examples of vestigial structures in humans
- goosebumps
- tailbone
are species that have more amino acid differences more or less related
less related, as they have had more mutations to their amino acid sequences
what is a orthologous protein
gene or proteins derived from a shared ancestor in which the primary function is conserved
what is an example of an orthologous protein
haemoglobin
what are the 2 ways to compare DNA
- direct comparison of DNA base sequences
- comparison of whole genomes
what is comparative genomics
the comparison of DNA or genes between different species to identify evolutionary relationships
what are phylogenetic trees
a branching diagram showing inferred evolutionary relationships between life forms based on their observed physical and genetic similarities and differences
what are the 5 features of a phylogenetic tree
- sister taxa
- root
- branches
- nodes
- tips
what is the sister taxa (phylogenetic trees)
two groups with a common ancestor that is not shared with another taxa
what is the root (phylogenetic trees)
the common ancestor of all taxa on a phylogenetic tree (starting point)
what is the node (phylogenetic trees)
shows an ancestor of two or more descendants on a phylogenetic tree (where the species split)
what are branches (phylogenetic trees)
a section of the phylogenetic tree which indicates a speciation event (coming off the node)
what are tips (phylogenetic trees)
the terminal point of a phylogenetic tree, representing a particular species
