Chapter 5 Evolution Of Biodiversity - Science Online

Chapter 5Evolution of Biodiversity

Earth is home to a tremendousdiversity of species Ecosystem diversity- the variety ofecosystems within a given region.Species diversity- the variety of species ina given ecosystem.Genetic diversity- the variety of geneswithin a given species.

Species richness- the number of species in agiven area.Species evenness- the measure of whether aparticular ecosystem is numerically dominatedby one species or are all represented by similarnumbers of individuals.

Evolution is the mechanismunderlying biodiversity Evolution- a change in the geneticcomposition of a population over time.Microevolution- evolution below thespecies level.Macroevolution- Evolution which givesrise to new species or new genera, family,class or phyla.

Creating Genetic Diversity Genes- physical locations on chromosomeswithin each cell of an organism.Genotype- the complete set of genes in anindividual.Mutation- a random change in the geneticcode.Phenotype- the actual set of traitsexpressed in an individual.

Evolution by artificial and naturalselection Evolution by artificial selection- when humansdetermine which individuals breed.Evolution by natural selection- theenvironment determines which individualsare most likely to survive and reproduce.

Darwin’s theory of evolution bynatural selection Individuals produce an excess of offspring.Not all offspring can survive.Individuals differ in their traits.Differences in traits can be passed on fromparents to offspring.Differences in traits are associated withdifferences in the ability to survive andreproduce.

Evolution by Random ProcessesMutation- occur randomly and can add to thegenetic variation of a population.Genetic drift- change in the genetic compositionof a population over time as a result of randommating.Bottleneck effect- a reduction in the geneticdiversity of a population caused by a reductionin its size.Founder effect- a change in a populationdescended from a small number of colonizingindividuals.

Speciation and extinctiondetermine biodiversity Allopatric speciation- when new species arecreated by geographic or reproductive isolation.

Sympatric speciation- the evolution of onespecies into two species in the absence ofgeographic isolation, usually through theprocess of polyploidy, an increase in thenumber of sets of chromosomes.

The pace of evolution

Evolution shapes ecological nichesand determines species distributions Range of tolerance- all species have an optimalenvironment in which it performs well. The limitto the abiotic conditions they can tolerate isknown as the range of tolerance.Fundamental niche- the ideal conditions for aspecies.

Niches Realized niche- the range of abiotic and bioticconditions under which a species lives. Thisdetermines the species distribution, or areas of theworld where it lives.Niche generalist- species that live under a widerange of conditions.Niche specialist- species that live only in specifichabitats.

The Fossil Record Fossils- remains of organisms that havebeen preserved in rock. Much of whatwe know about evolution comes fromthe fossil record.

The Five Global Mass Extinctions Mass extinction- when large numbers ofspecies went extinct over a relativelyshort period of time.

The Sixth Mass Extinction Scientists feel that we are in our sixthmass extinction, occurring in the last twodecades.Estimates of extinction rates vary widely,from 2 % to 25% by 2020.In contrast to previous mass extinctions,scientists agree that this one is caused byhumans.

Evolution is the mechanism underlying biodiversity Evolution- a change in the genetic composition of a population over time. Microevolution- evolution below the species level. Macroevolution- Evolution which gives r