- Even if the zygote survives to adulthood, the adult hybrid is infertile, keeping the two species that created the hybrid reproductively isolated.
- - mitochondria and chloroplasts have enzymes and transport systems homologous to those found in the plasma membranes of living prokaryotes - both organelles replicate their DNA through a splitting process similar to bacteria- both organelles contain a single, circular DNA molecule not associated with histone proteins, similar to bacteria- both organelles have their own ribosomes
- More genetically diverse populations have greater ability to adapt to changing environments because they are more likely to contain some individuals who can withstand the environmental pressures, while less genetically diverse populations are at greater risk of decline in population size or extinction.
- Two organisms that can form a zygote may still be reproductively isolated if the zygote does not survive to adulthood.
- populations are reproductively isolated from each other. This prevents them from interbreeding, and as the environments change, the evolution of new species may occur.
- If speciation rates are greater than extinction rates, species diversity will increase. If extinction rates are greater than speciation rates, species diversity will decrease.
- Even if two organisms are able to successfully copulate, if their gametes are incompatible, no zygote will be produced and the organisms will be reproductively isolated.
- - antibiotic resistance in bacteria - tumor cells developing resistance to chemotherapy drugs- pesticide resistance in insects- evolution of previously unseen pathogens and viruses- genomic changes in organisms over time
- Even if the first generation of hybrids is viable and fertile, successive generations result in offspring that is weaker and less robust and will cease to exist after a few generations.
- Occurs in the same geographic area (no geographic isolation), but other factors lead to reproductive barriers between members of the group, such as polyploidy in plants or sexual selection in animals.
- If an environment is relatively stable, there will be less selective pressure on populations, and the rate of speciation will be slower.
- If organisms live in different habitats and do not come into contact with one another, they cannot mate and form zygotes and are thus reproductively isolated
- 1) Inorganic materials that were present in Earth's early atmosphere combined to make the building blocks of biological molecules 2) Meteorites may have transported the organic materials needed for life to Earth
- a species is a group of organisms that are capable of interbreeding and producing viable and fertile offspring
- Occurs when a larger population becomes geographically separated and the smaller subgroups diverge and become separate species over time
- phylogenetic trees indicate the approximate time of evolutionary events, while cladograms do not
- the evolution of organisms into separate species that occupy different ecological niches. This often occurs after mass extinction events when many niches are left open for new species to fill. An example is Darwin's finches on the Galapagos Islands.
- Organisms can live in the same habitat, but if they are active at different times of the day or have breeding seasons during different times of the year, they will be temporally isolated and will not interbreed
- the least closely related member of the phylogenetic tree
- Gene flow is caused by the migration of individuals into a population. If these individuals carry different alleles than the receiving population, the allele frequency of the receiving population will change.