Click here to load reader

5.4 Evolution

  • View

  • Download

Embed Size (px)


5.4 Evolution. Define Evolution. Evolution is the process of cumulative change in the heritable characteristics of a population. Charles Darwin at age 22 traveled on HMS Beagle in 1831. Evidence for Evolution. Fossil Record - PowerPoint PPT Presentation

Text of 5.4 Evolution

5.4 Evolution

5.4 Evolution

Define EvolutionEvolution is the process of cumulative change in the heritable characteristics of a population

Charles Darwin at age 22 traveled on HMS Beagle in 1831Evidence for EvolutionFossil Record Most fossil data gives us sporadic information rather than continuous dataOverall, life which existed more than 500 mya was very different from life todayApart from organisms like sharks, cockroaches, ferns most organisms are very different from fossilized ancestorsAlthough most top predators are mammals, none of them existed during the Age of the Dinosaur

Evidence for Evolution2. Selective Breeding of Domestic AnimalsProvides good evidence for recent changes in heritable characteristicsIdea is to breed best plant/animal specimens together so offspring have higher likelihood of retaining those traitsEx: milk and meat cows

Evidence for Evolution3. Homologous StructuresAll life is connected through evolutionary history and therefore some organisms must share similar structuresEx: five-fingered (pentadactyl) limb


Natural SelectionDarwin noticed that plants and animals produce more offspring than the carrying capacity of that environment can supportEx: plants produce more seeds than propagateEx: mushrooms produce more spores than growEx: fish lay more eggs than survive

Not all offspring survive because of limited resources leads to struggle for survivalConsequences of OverproductionOverpopulation and limited resources causes competition Competition can lead to adaptive behaviors and allow organisms more fit for environment to have higher survival/reproduction rates and then these organisms genes are more likely to be passed on to the next generation

VariationMembers of a species can show variation (variation refers to differences in phenotypes)

Continuous VariationDiscontinuous Variation

Ex: blood groupsEx: height of trees in forestMutations and the Environment are a couple of methods which increase variationHow does Sexual Reproduction Increase Variation?1. Meiosis due to random orientation and independent assortment, each gamete contains a unique set of parental chromosomes

How does Sexual Reproduction Increase Variation?2. Fertilization random fertilization (egg + sperm) allows new combination of genes in organism

3. Crossing over during Prophase I of Meiosis also increases variation

How Natural Selection leads to EvolutionNatural selection is a process where the survival/thriving of organisms is dependent on the compatibility between their characteristics and the environmentThe Steps of Evolution by Natural Selection:Overproduction of offspring with genetic varianceBetter suited for enviro = higher likelihood to survive/reproLess suited for enviro = lower likelihood to survive/reproOver many generations these effects can change the gene poolEVOLUTION

Examples of Natural Selection in response to Environmental ChangeAntibiotic Resistance:Antibiotics are medications given for bacterial infections, but some bacteria are resistant to the antibiotics. The resistant bacteria can transfer their plasmids to other bacteria, creating strains that are resistantEx: a new strain of Staph bacteria (MRSA) has evolved to be resistant to antibiotics

Examples of Natural Selection in response to Environmental ChangePeppered MothPrior to Britains Industrial Revolution (1780-1850), both moths lived in the area but by the mid-1800s the environment in England had changed due to soot blanketing the trees so that the light colored moths were easier for birds to hunt therefore the darker moths had a natural advantage

Search related