Flashcards
Natural Selection
Cards in this deck (38)
- 1speciesgroup of individuals that share characteristics and can reproduce to produce fertile organism
- 2populationgroup of individuals of the same species living in a particular place at a particular time
- smaller populations quicker change can happen - 3gene poolsfrequency of the alleles of a particular gene
- 4gene pools- to see how populations have changed
- allele freq. is relative freq. of a particular allele in a population
- range from 0-100%
- evolution --> changes in the gene pool
- gene pools are dynamic - 5what causes gene pools to change1. mutations
2. selection pressure --> natural selection
3. random genetic drift - including founder effect
4. changes in gene flow --> immigration and migration - 6mutations- permanent change in the DNA of an organism
- cause a change in the genotype and phenotype
- raw material for natural selection --> genetic variation
- if the mutation provides a new allele, could help the organism to survive --> frequency of the allele will increase in gene pool - 7genetic drift- random fluctuation of allele frequencies in a population, from one generation to the next
- 8why does random genetic drift occur- due to a random chance, a certain allele is lost/gained from the gene pool of a population, hence changing the allele frequency in the population
- 9random genetic drift results in:- traits being lost from small populations
- unusual traits not commonly found in the parent population - 10example of random genetic driftDunkers
- population in Pennsylvania --> migrated from Hesse, Germany
- religion doesn't allow them to marry outside of their religion
- study identified number of different allele frequencies from the original German population and surrounding US population
- different blood groups, different ear lobes
- same selective pressures --> hence could have only been genetic drift - 11founder effect- example of random genetic drift
- small isolated population formed when a small number of people migrate and settle in a new area (uninhabited)
- gene pool of founding population is limited - 12migration= gene flow --> movement of genes from one population to another
- affects gene pools as brings new alleles from different populations to existing gene pools
- new alleles = advantageous - 13isolation- barrier to gene flow
- causes gene pools to lack genetic variation --> slows down or stops natural selection --> which slows down or stops evolutionary change - 14sociocultural barriers- religion
- language
- educational background
- economic status - 15geographical barriers- mountains
- oceans
- rivers
- deserts - 16isolation - different selective pressures leads to- the selection of different characteristics in the population
- 17genetic diseases- can cause allele frequency changes in gene pools
- allele for fatal disease would be expected to be eliminated from the gene pool overtime - 18natural selection- affects the frequency of alleles in a gene pool
- the frequency of favourable alleles increases
- the frequency of unfavourable alleles decreases - 19natural selection based on 3 observations1. variation - some members of population possess characteristics that can be passed on to the next generation
2. birth rate - more offspring born, than there is resources = competition
3. natures balance - number of organisms remains very constant - 20principles of evolution through natural selection1. variation of characteristics in a species
2. more offspring are produced than can survive
3. excessive birthrate and limited resources leads to struggle for survival
4. individuals with characteristics best suited to the environment, have more chance of surviving and reproducing (survival of the fittest)
5. favourable characteristics are passed on to the next generation
6. in the gene pool, the frequency of favourable alleles increases gradually over time - 21natural selection in humans- environment in early humans had a big impact on characteristics of humans
- 22body shape - African hot environment- increased allele frequency for short body and long limbs
- large SA compared to volume
- radiate more heat from skin in hot environment - 23body shape - eskimo cold environment- increased allele frequency for longer bodies and shorter limbs
- small SA compared to volumes
- lose less heat in a cold environment - 24body shape in cold environment- long body and short limbs = survival advantage
- when reproduce pass on favourable alleles to offspring
increased allele frequency for long body and short limbs - 25short body and long limbs in cold environment- survival disadvantage
- die before reproductive age
- decrease in allele frequency in the gene pool - 26skin colour - dark skin- natives from hot countries e.g Africa
- have genes that produce lots of melanin
- evolutionary terms --> protects against melanoma
- selective pressure --> UV light causing skin colour
- survival advantage --> no cancer - 27white skin- Northern Europe
- melanin stops UV light being absorbed
- need UV light to produce vitamin D
need vitamin D to absorb calcium
need calcium for strong bones
osteoporosis --> survival advantage to have dark skin in Norther Europe - 28speciationprocess of producing a new species from an existing species
- after many generations, changes in each population prevent interbreeding - 29key steps in speciation1. inherited variation
2. struggle for survival
3. isolation
4. differential selection
5. speciation - 30inherited variation- from germline mutation
- gene or chromosomal
- can provide a survival advantage
- change genotype and phenotype - 31differential selection- when each environment has a different selective pressure, causes a change in the allele frequency in the gene pool of each population
- 32sub-species- the same species just slight variation
- 33small population- individuals have a large impact on gene pool
- evolution fast
- by random chance e.g random genetic drift
- non adaptive - 34large population- individuals have a small impact on gene pool
- evolution slow
- natural selection is driving force
- changes are adaptive - 35Aborigines on Bentinck Islands- islands cut off from main land due to rising sea levels
- population became isolated
- after many generations blood alleles were compared
- population all Ib, no Ia
- on mainland low Ia, high Ib
- this is due to random genetic drift - 36thalassemia (genetic drift)- Recessive disease
- Anaemia – results from defects in formation of haemoglobin
- Low haemoglobin = causes fatigue due to few RBC
- Require blood transfusions throughout life and special drugs to remove excess iron that builds up
- Mediterranean people
- Marriages between cousins among people inhabiting the countries around
Mediterranean
- Increases chance of having a child with a genetic disease caused by a recessive allele
- As a result, thalassaemia common in these countries - 37what is sickle cell anaemia?- Point mutation in the gene responsible for haemoglobin
- Results in red blood cells being a crescent shape
- Usually fatal as cells don’t carry as much oxygen as normal RBC and they stick together and block small blood vessels
- Causes swelling in joints, strokes, damage to lungs and heart, death
sickle cells = don’t carry as much O2 and tend to stick together - 38sickle cell anaemia - natural selection- In the tropical zone of Africa, up to 40% of some populations carry the allele for SCA
- Disease occurs when a person inherits the allele from both parents
- Sickle cell trait gives certain advantages to those who have it provides degree of resistance to malaria = highest survival rate
- Reproduce, pass on selective advantageous allele to offspring = increase in allele frequency
- Malaria is a disease prevalent in parts of the world where sickle cell anaemia is found
- Allele is maintained in areas where malaria is present
- Those resistant = selective advantage against the selective pressure of MALARIA!
- Survival of the fittest = reproduce = pass on allele
Information
- Description
- Year 12 Sciences Flashcards on Natural Selection, created by Savannah Kerr on 03/09/2017.
- Created by
- Savannah Kerr
- Views
- 1
- Rating