Evolution Flashcards
Define descent with modification
All organisms share common ancestor
Descendants have accumulated modifications that help them better adapt to environment
Define microevolution
Change in allele frequency of a gene pool form one generation to the next (within a population)
How can microevolution lead to macroevolution ?
If genetic changes result in reproductive isolation from ancestral population
Define macroevolution
Evolution above species level ; descent of different species from common ancestor
Define population
A summation of all the organisms of the same species, who live in the same geographical area and have the capability of inbreeding
Define gene pool
Collection of all genes and various allelic forms of those genes within a particular population
Define allele frequency
Frequency or proportion of a particular allele in the gene pool
Define variation ( phenotypic )
The differences in characteristic between individual organisms belonging to same natural population
What is variation caused by ?
Genetic variation
Effect of the environment
What does variation result in ?
Different fitness and reproductive success between individuals in same population, under particular conditions (selective pressures) of their natural habitat
Is effects of environment that result in variation, heritable ?
It cannot be inherited
What leads to genetic variation ?
- meiosis and random fusion of gametes
- mutations : gene mutation & chromosomal aberration
How does meiosis and random fusion of gametes lead to variation ?
Reshuffling of existing alleles give rise to new combinations of alleles and genotypes in individuals = different phenotypes
How does gene mutation lead to variation ?
Results in new alleles (same gene but diff form) and new characteristics, increasing gene pool for natural selection to work on
How does chromosomal aberration lead to variation ?
Results in new genotypes with new combinations of alleles, affecting characteristic of individuals
Are mutations disadvantageous ?
Mostly
However when there is increased genetic variation, beneficial mutations may arise
When env change, mutations once unfavourable become favourable
Are mutations passed down / inheritable ?
Only those that occur in gametes are passed down to next generation
Define gene flow
Movement of alleles from one population to another due to migration of individuals
How else can genetic variation in population be increased ?
Gene flow from different population
Do all variations results in differential reproductive success ?
No
- some genetic variations are not expressed (eg. intron mutation)
- phenotype expressed may not be significant to reproductive success
- env conditions may not be electing for the particular phenotype
What is Charles Darwin’s definition of evolution ?
Descent with modification
- all organisms are related through descent, share a common ancestor
- descents have accumulated modifications or adaptations that fit them into their environments
What are the two inferences that Charles Darwin made from his observations of nature ?
- Selective agents / pressures present
- Survival of the fittest
What are the observations that Charles Darwin had for him to propose natural selection as mechanism for evolution ?
- Overproduction of offspring
- Constancy in number
- Variation among offspring
- Like produces like
Which group does natural selection operate on ?
Populations