“The process of change over time” Evolution part I “The process of change over time”

Charles Darwin Darwin is considered as the “father” of evolution Losing his passion to become a doctor in med school he took to the sea to become a “naturalist” in 1831 The name of the ship he spent 5 years on was the Beagle Darwin returned to England in 1836 with pages of notes from what he saw as well as many specimens from his journey

Charles Darwin Darwin spent 36 days on the Galapagos Islands These islands are located West of the Northern part of South America off the coast of Ecuador The Galapagos islands were an undisturbed island chain void of humans for thousands of years What Darwin found astonished him!

And lizards swam and ate algae Charles Darwin Because of geographic isolation, the inhabitants of the Galapagos evolved without predators This allowed humans to get as close as they wanted to research the animals Many species were the same species he found on other continents but, they had key differences! For example, a species of cacti normally only 5 feet tall grew to heights of 20 feet! And lizards swam and ate algae from the rocks

Charles Darwin One of the observations that spawned Darwin’s curiosity was the amazing similarities between animals of different species! Darwin also noticed that plants and animals had unique characteristics within the same species as well!

Important Vocabulary Natural variation – is defined as differences among individuals of the same species Interspecific variation – is variation among individuals of the same species Intraspecific variation – variation among individuals of different species Artificial selection – artificial selection is similar to selective breeding (being “chosen”) An example would be the selection for a mate that birds go through

Important Vocabulary Adaptation – any inherited characteristic that increases and organism’s chance of survival Adaptations can be a physical characteristic or a more complex behavior This lizard is known as the Thorny Devil and it lives in the harsh outback of Australia where there is very little water To get water, it’s body has special channels that lead water to the corners of its mouth and all it has to do is gulp to draw the moisture from the air that has condensed on its body (via capillary action)

Important Vocabulary Natural selection – aka. Survival of the fittest is defined as nature “selecting” individuals with characteristics making them well suited to their environment Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment. http://www.greenexpander.com/2007/12/10/amazing-octopus-camouflage/

Genes and Variation A group of interbreeding individuals is known as a population The genome of an individual organism is all of the genes that organism possesses worldwide The gene pool is ALL of the genes in a population including all of the ‘possible’ alleles For example: in Basenji puppies they can have 1 of 4 coat colors The relative frequency is how often that gene occurs in the gene pool

Genes and Variation Natural Selection and trait distribution Directional selection is when individuals in a population have a higher fitness over those in the middle range or lower range see figure 16-6 pg. 398 This causes a “shift” in the fitness towards one particular phenotype As an example: Suppose that there were many different height giraffes in a region of Africa that underwent sever climatic change The food availability is now 8’ higher than before and only a limited number of giraffe can actually reach the resource This would be directional selection

Natural Selection in Populations In any population of organisms there is variation within the species There are organisms that fit into a “bell curve” whereby the largest percent of the population is in the center with slightly different variations on either side These are two bell curves shown above. The mean is the average and the majority of the population phenotype. The curve represents the entire variation within the population

Directional Selection is the effect of a shift in a population’s phenotype in response to natural selection towards a more favored phenotype from the variation within the original population

Disruptive Selection Disruptive selection Occurs when both extreme phenotypes are favored by natural selection while the mean population is selected against by something in nature

Stabilizing Selection Occurs when the mean phenotype is highly favored in the environment and becomes even more dominant in the population This can lead to a lower diversity which makes species susceptible to disease or other limiting factors