Natural Selection/Speciation Flashcards
Discuss variations in a population.
Individuals in a population express a range of phenotypes due to the variation of the genotypes; of which is inheritable under circumstances that the trait gives an advantage in survival/reproduction over the rest of the population.
What is a gene pool?
The sum of all genes, with all variations possessed by a particular species at a particular time.
Outline the Allele frequency and their impacts on a population.
Relative frequency of a particular allele in a population; effected by:
Founder Effect - Small no. of organisms migrate to a new area, carrying a very small fraction of the original genetic variation.
Bottleneck Effect - A population reduced from a catastrophic event (allele may be lost by chance); as surviving pop. increase, only their allele will be present - gene pool falls.
Genetic Drift - Random fluctuation of allele frequencies in a pop. from one generation to the other - greatest impact on small pops. Consequence of genetic bottleneck; results from inbreeding from limited mating possibilities.
Outline the process of gene flow.
There are changes in allele frequencies in a gene pool due to migration.
- May influence the genetic composition of a pop. if there are differences in allele frequencies of native + non-native pops.
- Increase migration rate and difference in allele frequencies between pops., the greater their impact of gene flow.
What are the barriers to gene flow?
- Pops. kept apart by geographical barriers (e.g. mountains).
- Environmental differences.
- Different characteristics being favoured in other pops.
- Overtime, allele frequency of each gene pool will change depending on which characteristics are favoured for survival.
- Isolation results in the development of separate gene pools.
What are the three steps of Speciation?
The evolutionary process that leads to the formation of a new species - macroevolutionary process (allopatric/sympatric):
Isolation - of breeding pop., can be allopatric/sympatric. Interbreeding; gene flow between pops. is disturbed.
Adaptation - result of natural selection; isolated pop. begins to adapt to their current environment. Sub-pops. accumulating genetic variations - limited migration/interbreeding - small pop. can be influenced by random genetic drift.
Reproductive Isolation - if two pops. become sufficiently different - can’t interbreed; if this occurs both will be considered different species.
Outline the terms Natural and Artificial Selection.
Natural S - When the fitness of the individual is determined by the natural environment.
Artificial S - When humans decide which species should leave offspring for the next generation - animal/plant breeding programs.
What are the steps of Natural Selection?
1) Overproduction - more young are born than survive to maturity.
2) Variation - sexually reproducing species show variation in all inherited features.
3) Struggle for Survival - competition between individuals in a pop. for resources to survive.
4) Adaptation - species have features that enable them to survive in their environment.
5) Survival of the Fittest - some individuals are more likely to survive than others.
6) Reproductive Fitness - some individuals are more likely to survive, reproduce more than others.
7) Allele Carryover - offspring that survive will carry the alleles that determine adaptive features.
8) Change to Gene Pool - alleles that determine favourable features will increase in the gene pool - unfavourable decrease - evolution.
What is mutation and how is this linked with selection?
Permanent structural alteration in an organisms DNA. important for genetic variation. Natural selection determines which mutations remain in a gene pool.
Identify the difference between Micro/Macroevolution.
Micro - any change in the gene pool of a pop. - natural selection, genetic drift, etc.
Macro - major evolutionary changes above the species level.
Adaptive radiation: single group of organisms make rise to a new species. Rare/associated with major environmental change/catastrophic events.
What is the difference between Allopatric and Sympatric Speciation?
Allopatric - when species become physically separated via. geographical barriers and gene flow between pops. stops.
Sympatric - when two/more new species form a single population that is not separated by geographical barriers. results when pops. are under pressure.
