Natural selection
- 2. “Survival of the Fittest” Selection for traits that are most successful in current environment A constant process – environments change and therefore so do factors that determine success
- 3. Darwin proposed that organisms descend from common ancestors and change with time, diverging from the original common form This causes the evolution of new species
- 4. 1. Overpopulation 2. Competition 3. Variation 4. Survival of the Fittest 5. New Species
- 5. Organisms tend to produce many offspring – more than the environment can support Organisms will reproduce until something stops them (usually food)
- 6. •Because of overpopulation, individuals compete with one another over limited resources food, water, shelter, mates •Competition occurs both within and between species
- 7. •Individuals of a population vary in their traits and characteristics •This variation is passed on to offspring.
- 8. •Individuals with advantageous genetic traits are better adapted to their environment •This increases their chance of survival •This is called survival of the fittest
- 9. New species results by inheritance of trait(s), on genes, that give them another advantage over others New species evolve!
- 10. Where one species evolves into one or more other species Also called ADAPTIVE RADIATION
- 11. An inheritable characteristic that provides an advantage for survival and reproduction. Adaptations can be: 1. Structural – a part the organism has to help it survive Ex: Speed, camouflage, claws, quills, etc. 2. Physiological – a metabolic or chemical adaptation to help it survive Ex: ability to maintain internal temperature; use less water for photosynthesis; produce a poisen 3. Behavioral – something the organism does to help it survive Ex: Migration; solitary vs. herds; flying in formation
- 12. 1. Darwin’s finches 2. Peppered moth 3. Antibiotic resistant bacteria 4. Pesticide resistant mosquitoes **Do not copy!
- 13. Alleles exist with a certain frequency in populations of organisms The available genes and alleles in a population are called the “gene pool”
- 14. Changes in the structure of genes introduce new alleles to populations and disrupt equilibrium Not all mutations are good, many are fatal This is the source of all new alleles
- 15. Preference for a particular allele will increase its frequency in a population over generations Selection can happen in three different ways
- 16. 1. If the environment favours the average of the distribution, the selection is called stabilizing selection
- 17. 2. If the environment favours one extreme, the selection is directional
- 18. 3. If the environment favours both extremes, the selection is disruptive
- 19. Mutations: The Science of Survival https://www.youtube.com/watch?v=qVmusHZtQms (Darwin & Natural Selection) 20:00 to 29:29 (part 3?)