Evolution and Biodiversity Chapter Four

Evolution: All species descended from earlier ancestral species. Changing genetic make- up in a population over time. Accepted scientific explanation of how animals adapt and survive

Evolution and Adaptation Macroevolution – long term, large scale changes Microevolution – small genetic changes Gene pool – all genes in a population Mutation – random change in structure of DNA. Every so often, a mutation is beneficial for survival. Natural selection – individuals that have traits that benefit survival.

Natural Selection Microevolution is changes in the gene pool of a population over time that result in changes to the varieties of individuals in a population such as a change in a species' coloring or size. Macroevolution If the changes are over a very long time and are large enough that the population is no longer able to breed with other populations of the original species, it is considered a different species.

Evolution and Adaptation Microevolution Macroevolution

Natural Selection Three things must happen: 1. Genetic variability in a trait within population 2. Trait is heritable 3. Differential reproduction – must enable individuals with the trait to leave more offspring than others without the trait. Adaptive (heritable) trait helps survival and reproduction under current conditions

Speciation, Extinction, and Biodiversity How Species Evolve Speciation: A new species can arise when member of a population become isolated for a long period of time. Genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited. Fig. 5-7 p. 94

Geographic Isolation …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10

Reproductive Isolation a category of mechanisms that prevent two or more populations from exchanging genes The separation of the gene pools of populations, under some conditions, can lead to the genesis of distinct species. Reproductive isolation can occur either by preventing fertilization, or by the creation of a degenerate or sterile hybrid, such as the case with the common mule and the hinny. Basically, organisms have a barrier such as unfavored genes that don't allow them to mate.

Extinction Background extinction – slow rate When Environmental changes occur, species must evolve to adapt. If not… Background extinction – slow rate Mass extinction – quickly, large groups Mass depletion – higher than mass (Ice Age) 99% of species that have existed on earth are now extinct. Changes in Earth’s biodiversity – has leveled off during the last 1.8 million Years. Is this due to human influence?

Extinction Adaptive radiation – after mass extinctions, numerous new species evolve to fill vacated niches. Takes 1-10 million years for adaptive radiation to rebuild biodiversity. Human impacts – accelerated extinction

Human Impacts on Evolution Artificial Selection – artificially selecting superior genetic traits Agriculture Hatcheries pets Genetic Engineering Gene splicing Species creation in laboratories Takes less time than artificial selection Concerns about Genetic Engineering Many failures (1% success rate) Lead to more abortions? Only for the wealthy?

GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding. We have used genetic engineering to transfer genes from one species to another. Figure 4-15

Genetic Engineering: Genetically Modified Organisms (GMO) GMOs use recombinant DNA genes or portions of genes from different organisms. Figure 4-14

Identify and remove portion of DNA with Phase 1 Make Modified Gene E. coli Genetically modified plasmid Insert modified plasmid into E. coli Cell Extract Plasmid Extract DNA Plasmid Gene of interest DNA Identify and remove portion of DNA with desired trait Remove plasmid from DNA of E. coli Insert extracted (step 2) into plasmid (step 3) Identify and extract gene with desired trait Grow in tissue culture to make copies Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Fig. 4-14, p. 95