1.3 Natural Selection Flashcards
Causes
Mutations, Meiosis, Sexual Reproduction/Random Fertilization
Mutations
Add new alleles to the gene pool, some are harmful, some are not
Meiosis
Produces gamete with unique combinations of alleles
Sexual Reproduction/Random Fertilization
Unique offspring
Results
- Individuals will differ in the adaptations they have
- Some will be better adapted to the environment than others
Adaptations
Characteristics
Competition
More individuals are born than can survive (overproduction of offspring)
Competition for food, water, territory, reproductive partners, to avoid predators etc.
Adaptations, Survival, Reproduction
More favorable adoptions –> more likely to survive –> more likely to reproduce and pass on adaptations
Selective Pressure
Evolutionary force that causes particular traits to be more favorable in certain environmental conditions
Antibiotic Resistance
Mutated bacteria can survive in presence of antibiotics
Multiply –> Increase –> Spr
Forms of Natural Selection
- Directional
- Stabilizing
- Disruptive
Stabilizing Selection
Selects for an intermediate phenotype
Extremes die, middle lives/grows
(Capybara, Human birth weight)
Directional Selection
Favours on of two extreme phenotypes depending on the environment
Moves towards one of the extremes
(Giraffe neck length - longer = more food)
Disruptive Selection
Faviurs extreme phenotypes and selects against an intermediate phenotype
Moves towards extremes, middle becomes less
(Oyster coloration)
Environment
Surrounding/habitats that plants, animals and living organisms share
Natural Selection
The process which drives evolution; where favorable types are selected for and unfavorable types are selected against
Variation
The occurrence in an organism in more than one distinct color or form
Heritable
When a characteristic is transmissible from parent to offspring through genes
Allele
The form of a gene. E.g. if the gene is for “eye color”, then “blue” and “brown” are the different alleles
Allele Frequency
The proportion of a particular allele variant of a gene present amongst a population’s gene pool
Resistance
The natural ability to remain unaffected by agents in its environment. E.g. antibiotics or toxins
