UNIT4 AOS1 Flashcards
-changes in the genetic makeup of a population -changes in biodiversity over time -determining relatedness between species -human change over time
What are mutations?
changes in the DNA base sequence of gene
How do mutations usually occur?
through errors during DNA replication
What are point mutations? and what are the three types?
they alter add or remove a single nucleotide from a sequence of DNA or RNA and typically only effect a single gene. Deletions, substitutions and additions.
Are all mutations negative?
no a mutation may produce a new characteristic that may provide a survival advantage
What are substitution mutations?
occurs when one nucleotide is replaced by another type of nucleotide.
What is a silent mutation? and why can it occur?
a silent mutation is when a substitution results In a new codon that still codes for the same amino acid. it occurs due to the degeneracy of genetic code
What are missense mutations?
is when a base substitution results in a different amino acid being encoded.
What are nonsense mutations ?
is a point mutation that results in a premature stop codon in transcribed RNA and a non-functional protein
What is insertion mutations?
type of frameshift mutation where an nucleotide is inserted into DNA or RNA sequence
What are deletion mutation?
type of frameshift mutation where one nucleotide is removed from DNA or RNA sequence
What are block mutations?
block mutations affect large sections of chromosome, therefor affecting many genes. there are four main types, translocations, inversions, duplications and deletions
What are translocations?
is when a section of one chromosome attaches to the end of another chromosome. abnormally cause b rearrangement of parts between non-homologous chromosomes
What are inversions?
inversions occur when a single chromosome undergoes breakage and a segment of the chromosome is reversed end to end
What are duplications?
duplications are a type of mutation in which part of the second homologous chromosome joins on to its partner
What are deletions?
is a mutation in which a part of the chromosome is missing- part of the chromosome breaks off but does not reattach
What is a chromosomal abnormality?
a mutation that involves the gain or loos of whole chromosome in a cell- occurs due to mistakes in cell division
What is aneuploidy ?
occurs when an organism possesses an abnormal umber 0f chromosomes that is jot a who multiple of a haploid number
When do aneuploidy’s occur?
when there has been a non-disjunction is anaphase 1 or 2 of meiosis.
What is a polyploidy?
when whole sets of chromosomes do not seperate resulting in diploid gametes
Do animals or plants survive when polyploidy occurs?
animals rarely survive as it often results in a miscarriage.
very common in plants, although these plants cannot reproduce
How do we know if organisms are of the same species?
when they can interbreed to produce fertile offspring
What is a subspecies?
when two species interbreed creating infertile offspring
What are three types of phenotypic variation?
structural =appearance, short hair biochemical=colour which are due to protein expression physiological=metabolic rate, body temp behavioural= nest building, observation developmental= young-tadpole, adult-frog geographical= environmental behaviour
What is the ‘formula for phenotype’?
phenotype=genotype X environment
What factors that cause/increase genetic variation
- Sexual reproduction
- Mutation
- Gene Flow
How does sexual reproduction increase variation?
a) crossing over- which results in the recombination of genetic material in chromosomes, occurs in prophase1
b) random assortment of chromosomes into gametes,
c) particular combinations of parents=mixing of gametes
d) the particular combination of gametes
How does mutations increase genetic variation?
A mutation is a change in DNA base sequence, this can then change the structure of DNA making up a gene or chromosome
Define genepool
all the alleles of a gene present in a population
Define allele frequency
the proportion each allele if all genotypes are known must add to 1
Define polymorphic vs monomorphic population
p=individuals show variation in trait
m=all members of population show one form of a trait
Define evolution
the genetic change in a population over time
Define population
organisms of the same species living in the same place at the same time
Define gene flow and how it increases genetic variation?
gene flow is the movement of alleles form one population to another as a result of sexual reproduction between individuals from each population. this adds new Gennes or alleles to a populations gene pool
Define genetic drift
involves the unpredictable changes in allele frequencies in a population due to chance events. two types, the bottle neck effect and founder effect
How does genetic drift effect genetic variation?
creates a small isolated population that has no gene flow, therefor there is decreased genetic variation
Describe the bottle neck effect
results from the reduction in size of a population due to a natural disaster. genetically diverse original population, reduced due to natural disaster, time, genetic;y simplified population
Describe the founder effect
an example of genetic drift caused by the colonisation of an area by a limited number of individuals from a parent population not representative of original population. Decrease in variation, time and sexual reproduction creates a large popular with little variation
How does genetic drift effect the biodiversity of a population?
creates little genetic diversity and terror is unlikely to adapt to changing environmental conditions= more likely to become extinct
What are selection pressures?
are living or non-living factors that along with variation ‘select for’ or select against particular organisms serving and reproducing, therefor influencing the allele frequency of a population
Define heterozygote advantage
when in a situation that case heterozygous individuals to be favoured by selection pressures
What is an advantage of variation?
variation within a species improves the chance of the species serving environment change.
Define biological fitness
refers to the phenotype which is most suitable for the particular environment
What is needed for natural selection to occur?
- Genetic variation, resulting in phenotypic variation must exist in original population
- Species must be exposed to a selective pressure, where organisms with the favoured phenotype will have a better chance of surviving and reproducing
- The organisms that reproduce are likely to pass the favoured characteristic to next generation
- Therefor greater allele frequency of favourable characteristic
How is biodiversity in fragmented populations ?
fragmentation of population is typically caused by habitat fragmentation. With a more limited gene pool, population fragmentation causes a high rate of inbreeding within the populations which leads to decrease in genetic variability in the species involved.
Why does interbreeding decrease the genetic fitness of the population?
- it forces competition with relatives, which decreases evolutionary fitness
- there is an increased possibility that a lethal homozygous recessive trait may be expressed this decreases the average litter size therefor decreasing population
- Over time, the ability of a species to adapt to a changing environment
Define speciation
speciation is the process of species formation
What is allopatric speciation?
allopatric speciation can occur when members of a population are split into two seperate groups, each of which is exposed to different selective forces. If populations become geographically isolated and gene flow ceases allopatric speciation can occur as a result
What is artificial selection/selective breeding?
The process of selective breeding involves humans selecting and breeding organisms of their desired phenotype. therefore this variety will become the fittest in a population. reduces gene pool
What does the loss of genetic diversity due to selective breeding mean?
this means populations are more vulnerable environmental changes such as disease due to lack of variation
Why has selective breeding lead to an increase in genetic abnormalities?
in the same way inbreeding among human population can increase the frequency of normally rare alleles that cause diseases the deflective breeding of dogs has lead to health problems
Define sympatric speciation
is genetic isolation caused by behavioural differences, chromosomal differences and seasonal behaviour
Define extinction
in evolutionary terms extinction is ehe a species ceases to exist or a particular variation no longer exists globally. in genetic terms this means that the alleles for the species have been eradicated
Extinction V Mass extinction
extinction=alleles of one species lost change in niche of organism
mass extinction=alleles of many species lost
What is extinction caused by?
- a change in the environment so rapid that the course of evolution could not occur, and the change was too dramatic for the species to survive
- small inbreeding populations with little variation (genetic drift) suffer the adverse effects of a change selective pressure
- humans, removing habitats, introduction of feral organisms, hunting
Summary of plant evolution
the first land plants are believed to have evolved form a single celled aquatic organism (simple), were mosses and liverwort. Eventually plants with conducting tissues evolved, which gave rise to ferns and then seed plants. ultimately flowering pants evolved from a group of vascular seed plants
Summary of mammal evolution
unicellular aquatic organisms are have though to evolves into multicellular aquatic animals. vertebrates first appeared in primitive fish. amphibians were the first vertebrates to move onto land. reptiles evolved from certain amphibian species and birds and mammals evolved at a later date from different reptile groups.
When were the first humans first believed to have evolved?
2.8 million years ago
When were the first primates believed to have been around?
65 million years ago
When was the first algae n land believed to be?
444-416 million years ago
When were the first land vertebrates believed to evolved?
350 million years ago
When were mammals believed to have evolved?
251-200 million years ago
What evidence of biological change over time is there?
- Fossils
- Coparative anatomy
- homologous and analogous structures
- vestigial structures - Comparative embryology
- Molecular homology
What are fossils?
fossils are evidence of prehistoric life. they do not need to be part of the original animal . they are commonly found in sedimentary rock.
What is needed for fossils to be formed?
- there must be a quick burial
- Must be near bed of water
- body of organism or prehistoric evidence is covered by sediments such as mud, slit sand
- compresses by sediment, therefore does not entirely decompose]
- minerals and water penetrate the hard parts of the dead organisms therefor Turing it Ito rock and reserving it
What is strata?
strata refers to the layers of sediment rock
What is relative dating?
also known as stratigraphy . is the science of determining the age of an object in comparison to another without determining the absolute age.
What are index fossils?
index fossils are fossils used to define geographical periods. often the only way to age a fossil bed is to use index fossils together with stratigraphy
How is the absolute age of fossils dated?
dated using radiometric dating which uses the half life of a radioactive element, either I the fossil itself or the surrounding rock to date fossils
What are transitional fossils?
are fossils with features intermediate between those of ancestral and descendant species
What are living fossils?
are living organisms which have remained essentially unchanged fro their ancestors of hundreds of millions of years ago, lung fish
What are homologous structures? What are they evidence of?
structures in different organisms that have a similar basic pattern through common origin, although they may serve a different purpose. evidence of divergent evolution
What are analogous structures?
features that have similar function in different organisms but may not have the same structure. may be due to similar;ar selective pressures
What are vestigial structures?
in some organisms there may be some organs that are functionless or reduced in nature, these are vestigial structures. e.g pelvic bone in a whale
What is comparative embryology? and how is it used as evidence of biological change over time?
comparative embryology compares different organism at the embryonic stage . Organisms with distinctively different adult forms are often similar at. embryo stage. this suggests that these organisms have a common ancestor
What is molecular homology?
if species have similar genes and proteins we can predict how similar they are in terms of evolution. e.g RNA,DNA, antibody-antigen, enzymes, amino acid sequence
What is convergent evolution?
occurs when similar features independently develop on organisms that are not closely related. similar features because of similar selection pressures
What is divergent evolution?
two related species diverge from a common ancestor. then they independently evolve a common feature that was not found in the common answer. exposed to different selection pressures
Why is mtDNA best to use for molecular homology?
- small and circular DNA molecules that are inherited maternally, therefor more stable and recombination and crossing over cannot occur, therefor more conserved
- mtDNA that are not apart of a gene can be hyper variable, this means that there can accumulate mutations without interfering with cellular functions.
What part of the mtDNA gives an indication of relatedness?
the variable regions. the more similar the DNA sequence the closer the relationship the two organisms have
What is the molecular clock?
the molecular clock is a technique that uses rates of molecular change to deduce the time in geological history when two species diverged. uses amino acid changes caused by mutations in DNA
What is a limitation of the molecular clock?
it assumes that the rate of mutations is constant. which is untrue because selective pressures also affect phenotype
What are master genes? and give an example
genes that control gene expression levels of regulatory genes. an example is BMP gene which produces the BMP protein
What does an increase in BMP cause? in finches and cichlid
promotes wide, deep beak
-strong, heavy biting jaws with powerful muscles
What does a decrease in BMP causen finches and cichlid
promotes long narrow beak
-longer slender sucking jaws
List steps of DNA hybridisation
- Prepare unique DNA from species to be compares=must be same part of chromosome
- Make single stranded by heating then mix
- Cool and allow strands to pair- some parting will occur between DNA from different species
How does the pairing of DNA in DNA hybridisation indicate the relatedness of a species?
the more closely related 2 species are the more complimentary their DNA will be therefor the stronger the hybrid molecule will bind. therefor the temperature to separate them will be higher
Define hominoids
include all apes, both the great and lesser apes
Define hominids
include all the great apes
Define hominins
collective term for all species and their bipedal close relatives
What characteristic define primates?
- large brain for body size
- five long finger and opposable thumb
- forward facing eyes
- four upper and lower incisors
- tendency for erectness
- parenting shown
Characteristics that define hominins
- bipedal consequences=s-shaped spine, wider pelvis, flat arched foot, foramen magnum as skull base
- reduced canines and incisors
- large frontal lobe
- reduced jaw size relative to skull
- reduced brow ridge
- flatter skull
What are the structural changes in evolution?
- skull shape= becomes flatter, bigger cranium size, large frontal lobe=increased use of tools
- Foramen magnum= moved to skull base
- Pelvic structure= wider, bipedalism, reproduction for birthing bigger skulls
What are technological changes in evolution?
- use as fire as tool-cooked food=smaller canines
- rocks as tools=hunting=more advantages=top of food chain
- clothing=less hair to keep warm
Define cultural changes in relation to evolution
cultural evolution refers to the transmission of information from generation to generation that does not involve genetic transmission
What does the out of Africa theory suggest about neanderthals, modern human ancestors and Denisovans ?
That neanderthals and modern human ancestors eft Africa at different times and were therefor exposed to different selective pressures that caused speciation. it is believes that gene flow occurred between the two suggesting that at one stage they were in the same place at the same time, therefor at least subspecies.and deneflow seen in Denisovans with both neanderthal and modern human ancestors , although more like neanderthals
What does the regional continuity hypothesis suggest?
- modern humans should appear throughout Africa, Asia and Europe during the same time period
- transitional forms should be found in Africa , Asia and Europe
- Variation in mtDNA should be approximately the same in human populations from all regions of the old world
What are some examples of cultural evolution?
as the frontal lobe began to dive so did language, rituals(burying the dead), dancing, folklore, living in groups(easier reproduction and looking after young)
