Evolution of Biodiversity Chapter 5 Evolution of Biodiversity

It is difficult to estimate the number of species on Earth What is the range of current estimates for the number of species on Earth? 5-100 million species However, most scientists agree that there are approximately 10 million species.

Species richness- the number of species in a given area. Species evenness- the relative proportion of individuals within the different species in a given area

Page 151 species richness and species evenness are two different measure of species diversity. Both communities contain the same # of species, community 1 has more even distribution of species and is therefore more diverse than community 2.

Why are they both important? So- what is the difference between species richness and species evenness? Why are they both important? Species richness is the number of species in a given area. Species Evenness is the species abundance, which is the relative proportion of individuals within different species in a given location.

Evolutionary Relationship can be illustrated using phylogeny Phylogeny: the branching pattern of evolutionary relationships Describe how scientists determine phylogenic trees. Identify changes that distinguished each species from its common ancestor.

The relatedness of the species in a phylogeny is determined by similarity of traits: the more similar the traits of two species, the more closely related the two species are assumed to be.

Review: How many species are estimated to exist on Earth? Two Savanna Communities both contain 15 plant species. In community a, each of the 15 species is represented by 20 individuals. In community B, 10 of the species are each represented by 12 individuals. The remaining 5 species are each represented by 3 individuals. Which one has a higher species evenness? 100 million Community A has a higher species evenness.

HW: Page 184, read and answer FRQ. Page 153

Module 15: How Evolution Creates Biodiversity

Evolution is the mechanism underlying biodiversity Evolution- a change in the genetic composition of a population over time. Microevolution- evolution below the species level. (occurs within species, creating a variety of characteristics seen among individuals) Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla. How do they both contribute to biodiversity on Earth? Both create genetic variation at the species level and greater species diversity in communities. Greater variation allows for increased survival and stability as populataions and communities have greater adaptability to changing conditions.

Creating Genetic Diversity Genes- physical locations on chromosomes within each cell of an organism. Genotype- the complete set of genes in an individual. Mutation- a random change in the genetic code. Phenotype- the actual set of traits expressed in an individual. (physical)

How do variations in phenotype benefit the organism? Remember, phenotype can be influenced by both genotype and environmental factors. By being able to respond to changing environmental conditions, organisms can improve their ability to survive and reproduce. Page 155.

Evolution by artificial and natural selection Evolution by artificial selection- when humans determine which individuals breed Usually with a preconceived set of traits in mind Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce. Evolution can also be a result of random processes (mutation, gene flow, genetic drift, bottleneck effect, and founder effect)

Artificial selection on animals Domestic dogs have been bred by humans to get the desired traits.

Earth is home to a tremendous diversity of species Ecosystem diversity- the variety of ecosystems within a given region. Species diversity- the variety of species in a given ecosystem. Genetic diversity- the variety of genes within a given species.

Artificial Selection Artificial selection has been useful to humans. However, with the use of herbicides by farmers to kill weeds, there is an increasing chance for a mutation to occur that allows the weed to survive to herbicide application. If this mutated plant passes on its resistant gene to its offspring… we gotta problem.

Darwin’s theory of evolution by natural selection Individuals produce an excess of offspring. Not all offspring can survive. Individuals differ in their traits. Differences in traits can be passed on from parents to offspring. Differences in traits are associated with differences in the ability to survive and reproduce.

Fitness: an individuals ability to survive and reproduce. Adaptation: a trait that improves an individuals fitness All species produce an excess # of offspring. Only those offspring with the fittest genotype will pass on their genes to the next generation. This Photo by Unknown Author is licensed under CC BY-SA