Selection causes Microevolution

Selection causes Microevolution• Frequency of alleles (versions of a gene) changes in a population

Selection creates Adaptations

Traits common to all members of a populationConfer greater success

Selection can lead to Macroevolution

Populations no longer interbreed Become more different over long periods of time

micro

macro

Change on a grand scale

Selection can lead to Macroevolution

= different species

Ensatina salamanders

Inhabit the CA coast, and Sierra foothills, but not the hot , dry Central Valley

From Microevolution to Macroevolution Geographic Isolation

Geographic isolation causes Reproductive isolation

Interbreed

Do not interbreed

Functionally separate species

Species? Organisms that interbreed, producing viable, fertile, offspring

A mule is neither horse nor donkey

The evolution of a species is called speciation

Geographic isolation causes Reproductive isolation

Geographic isolation causes Reproductive isolation

Geographic isolation causes Reproductive isolation

Grand Canyon

Other factors also cause Reproductive isolation

Sexual selection

Other factors also cause Reproductive isolation

Behavior

TimingLay eggs in green (early) fruit

Lay eggs later, in ripe fruit

Mature at different times, reproductively isolated

Once isolated, the populations become less and less alikeYes, via selection but also

via unique genetic mutationsRandom mutation creates green phenotype

Once isolated, the populations become less and less alike

Random chance event causing changes in allele frequencies

Yes, via selection but alsovia genetic drift random changes, not directed

Genetic drift

Most apparent in small populationsNet loss of variation/diversity

Ex: bottleneck event

20 Northern Elephant Seals

30,000 todayOf 24 genes studied no allelic variation

Hunted population

Genetic drift Ex: founders effect

Small founding population with less genetic variation than the original

During a Caribbean hurricane, Green iguanas are rafted to Anguilla from Guadeloupe

Gene Flow causes change (aka evolution) too

Movement of genes - via individuals or gametes - between populations

pollination spreads sperm

Gene Flow causes change (aka evolution) too

Movement of genes, via individuals or gametes between populations

immigrationemigration

More or less alike in time?

• Reformat following slides

• Which type of event explains the high incidence of polydactylism found in the Amish population?

Bottleneck, Gene Flow or Founder Effect?

Founder Effect

• Flower population: ww = white flower; WW and Ww = purple flower; a mud slide wipes out most of the white flowered plants. What type of event occurred?

Bottleneck, Gene Flow or Founder Effect?

Bottleneck

• Genetic modifications from transgenic plants passed to neighboring populations of wild relatives. What type of event occurred?

Bottleneck, Gene Flow or Founder Effect?

Gene Flow

• Millions of greater prairie chickens once lived on the prairies of Illinois. As these prairies were converted to farmland and other uses during the 19th and 20th century, the number of greater prairie chickens plummeted to less than 50 individuals. The few survivors have low levels of genetic variation. What type of event occurred?

Bottleneck, Gene Flow or Founder Effect?

Bottleneck

• This event resulted in the world wide spread of several insecitcide-resistance alleles in the mosquito Cluex pipiens, a vector for West Nile virus and Malaria. What type of event occurred?

Bottleneck, Gene Flow, or Founder Effect?

Gene Flow

• A few weeks after two major hurricanes swept through the Caribbean islands, fishermen on the island of The allele frequencies for the founding population on Anguilla differed from those on Guadeloupe. What type of event occurred?

Bottleneck, Gene Flow or Founder Effect?

Founder Effect