BIO 311D

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Mechanisms of Evolution

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BIO 311D

Adaptive Radiation: development of several new species from a common ancestor due to adaptations to different environments

Species in habitats

specialized

realized niche and fundamental niche are about the same size

are only able to live in very specific environments such as a canopy in a rainforest

generalized

have larger fundamental niches than realized niche

Mammals evolved from reptiles

Homo Sapiens evolved from Ardipithecus 5 milion years ago

humans most closely related to chimpanzees with only 1.4% difference in genomic DNA

Whales are most closely related to Hippos

Birds evolved from dinasaurs

developed active flight beginning with Arboreal. to leaping, to parachuting, to gliding, to active flight

Organization of Genetic Variation

polyploidy in plants allow for more gentic variation

Introduction of genetic variation

DIvergence from a common ancestro based on adaptation to the environment the organism was exposed to

Mutations: random changes in genetic code

greates source of genetic variation

make new alleles

95% harmfull 4% neutral 1% beneficial

Genetic Rescue

The introduction of a closely related species into the endagered population to introduce more genetic variability in order to enhance chances of survival by reducing inbreeding depression

inbreeding depression causes many organisms to die off because of the lack of genetica variabiltiy

Selection: differential reproduction among differing phenotypes in a population

Natural Selection

environment selecting based on phenotypic traits

adverse weather conditions speed up evolution

Selective forces acting on humans

Automatic abortion of monosomes, trisomes because fetus develops slower

Sexual Selection

Components: Males compete, Females choose

Survival of the Fittest

selection is doe based on pheotype

ex: english moths that the birds were eating base on the ones that they could see, either white moths or peppered moths

Population Regulation

Population dependent factors

Birth Rate

as population increases birth rate decreases

contraception has decreased the total births in recent years

amount of education of women also affects this

Mortality Rate

as population density increases the mortality rate increases

more densily populated ares are more prone to enconter disease and to cause it to spread

Main factors that allow for population growth are food, medicine and sanitation

disease also affect the chances of survival of an organism

Speciation: species formation from a common ancestor

Character Displacement

when two organisms are headed towards each other based on resources but then swerve away in order to reduce competition

EX: finches on Gallapagos Island with different sized beaks

Evolution

Convergent

development of phenotypic similarities between distantly related taxa over time

Divergent

accumulation of phenotypic differences between two lineages originating from a common ancestor over time

Parallel

similar changes in the phenotype between two geographically isolated taxa (species, genera, etc.)

Sympatric Speciation

species formation from a common ancestor in the same geographical location

Allopatric Speciation

species formation from a common ancestor in geographically separate location

Species Interaction:

competition

resource partitioning

when organism focus on a speciic resource to reduce competition

allow for the most fit individuals to pass on their genes

Males compete to reproduce with females

the male that best adapted will most likely be able to reproduce more than a male that is not very strong

resources and habitat

Realized niche

the resources and habitats that an organism actually takes up

fundamental niche

the resources and habitats that an organism can use or take up

Relationships

Predation

one organism depends on the other organism as a food source

Mutualism

both of the organisms benefit from the relationship

Commensalism

when one organisms benefits and the other one is not harmed

Parasitism

when one organism benefits and the other one is harmed