Selection And Evolution Flashcards
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Mutations that occur in body cells often have no effects at all on the organism
Discontinuous variation and an example:
اختلاف گسسته
Differences between individuals of a species in which each one belongs to one of a small number of distinct categories with no intermediates.for example:
Blood group(qualitative differences)
Continuous variation and an example:
اختلاف پیوسته
Difference between individuals of a species in which each one can lie at any point in the range between the highest and lowest values.for example:
Height and mass(quantitative differences)
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Mutations in cells in the ovaries or testes of an animal or in ovaries or anthers of a plant may be inherited by offspring
Discontinuous variation is caused entirely by….
Genes(with the environment having no effect)
Continuous variation is also affected by genes but…………can also have an effect
Environment
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In discontinuous variation different alleles at a single gene locus have large effect on the phenotype
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in continuous variation different alleles at a single gene locus have small effect on the phenotype
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In continuous variation different genes have the same, often additive effect on the phenotype
Polygenes:
A number of different genes at different loci that all contribute to a particular aspect of phenotype(in continuous variation)
Some other examples of discontinuous variation:
Inheritance of:
-sickle cell anemia (HBB)
-haemophilia(F8)
-flower color in salvia)
-stem color of tomato plants
-feather colors of chicken
Biotic factors:
(Example)
An environmental factor that is caused by living organisms (predation,competition for food or infection by pathogens
Abiotic factors:
Example
An environmental factor that is caused by non-living components.(water supply,nutrient levels of the soil,soil ph, light intensity)
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Most genes have many more than two alleles that you consider
Fitness:
The ability of an organism to survive and reproduce
Selection pressure:
An environmental factor that affects the chance of survival of an organism.(organisms with one phenotype are more likely to survive and reproduce than those with a different phenotype
Stabilizing selection:
Natural selection that tends to keep allele frequencies relatively constant over many generations
Directional selection:
Natural selection that causes a gradual change in allele frequency over many generations
Disruptive selection :
Natural selection that maintains relatively high frequencies of two different sets of alleles;individuals with intermediate features and allele sets are not selected for
Polymorphism:
(happens when disruptive selection)
The continued existence of two or more different phenotypes in species
Directional changes happen when
There’s a change in selection pressure or when a new allele arises by mutation
Antibiotic resistance of bacteria is an example of ……
Directional selection
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Plasmids are quite frequently transferred from one bacterium to another (even between different species)
Genetic drift:
The gradual change in allele frequency in a small population,where some alleles are lost or favoured just by chance and not by natural selection
Gene pool:
The complete range of DNA base sequences in all the organisms in a species or population
Founder effect :
The reduction in a gene pool compared with the main populations of a species, resulting from only two or three individuals (with only a selection of the alleles in the gene pool) starting off a new population
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Without genetic variation the species is unlikely to be able to adapt to changes in its environment such as climate change
Evolutionary bottleneck :
A period when the numbers of a species fall to a very low level resulting in the loss of a large number of alleles and therefore a reduction in the gene pool of the species
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If the differences are significant and migration and non random mating can be discounted,this suggests that DIRECTIONAL SELECTION is occurring in the population
Artificial selection (selective breeding):
The selection by humans of organisms with desired traits to survive and reproduce
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Unlike natural selection,artificial selection often concentrates on 1 or 2 characteristics
Inbreeding depression:
A loss of the ability to survive and grow well due to breeding between close relatives; this increases the chance of harmful recessive alleles coming together in an individual and being expressed
Inbreeding;
Breeding between organisms with similar genotypes or that are closely related.
Outbreeding:
Breeding between individuals that are not closely related to
Hybrid vigour:
An increase ability to survive and grow well, as a result of outbreeding and therefore increasing heterozygousity
Evolution:
A process leading to the formation of new species from pre-existing species over time
Morphological:
Relating to structural features
Physicological:
Relating to metabolic and other processes in a living organism
Reproductive isolation:
The ability of two groups of organisms to breed with one another;two populations of the same species may be geographically separated or two different species are unable to breed to produce fertile offspring
Genetically isolated:
No longer able to breed together.there is no exchange of genes
Speciation:
The production of new species
Geographical isolation:
Separation by a geographical barrier such as stretch of water or a mountain range
Allopatric speciation:
The development of new species following geographical isolation
Sympatric speciation:
The development of new species without any geographical separation
Ecological separation:
The separation of two populations because they live in different environments in the sane area and so can not breed together
Behavioural separation:
The separation of two populations because they have different behaviors which prevent them breeding together
About human mitochondrial DNA(mtDNA):
-is inherited through the female line(zygote contains the mitochondria of the egg but not for the sperm)
-since the mtDNA is circular and therefore cannot undergo any form of crossing over so changes in the sequence of nucleotides can only arise by mutation
-mtdna mutates faster then nuclear DNA acquiring one mutation every 25000 years
