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Transcript
Biodiversity and Evolution Chapter 4 What is Biodiversity? • The variety of Earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life. • Species – A group of organisms with a set of characteristics that distinguish it from other groups of organisms. – Must be able to reproduce fertile offspring with other members within the species. • Species diversity vs. genetic diversity. • Ecosystem diversity – Biomes: large regions such as forests, deserts, and grasslands with distinct climates and certain species. Earth’s Change Over Time • Biological Evolution by Natural Selection explains how life changes over time. – Individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits. – Populations evolve. Not individuals. Charles Darwin • Theory of Evolution by natural selection: – Individuals produce more offspring than survive. – Individuals differ in their traits – Traits can be passed on from parents to offspring. – Some traits are more favorable than others (allow an organism to survive and reproduce) • Fitness: an ability to survive and reproduce • Adaptations are traits that improve an individual’s fitness. What’s necessary for evolution to occur? • Genetic Variability – Mutations – Recombination • Genes – segments of DNA that code for possible traits that can be passed down to offspring. – A complete set of genes is called genotype. Genotype vs. Phenotype • Phenotype can be influenced by just genotype or a combination of genotype and environment. Evolution by Artificial Selection • When humans determine which individuals breed. • Artificial Selection has produced numerous breeds of dogs, horses, cattle, sheep, pigs, and chickens with traits humans find useful or aesthetically pleasing. Evolution by Random Process • Mutations Evolution by Random Process Genetic Drift Evolution by Random Processes The Bottleneck Effect Evolution by Random Process Founder Effect Allopatric Vs. Sympatric Speciation • Allopatric Speciation: – Geographic Isolation – physical separation of members of a population resulting in different genotypes between the two new populations. – Reproductive Isolation – Genotypes of two populations become so different, they can no longer reproduce with one another. Allopatric Vs. Sympatric Speciation • Sympatric Speciation: – Polyploidy – number of chromosomes increase. Once an organism becomes polyploidy, they cannot reproduce with their diploid ancestors. • Often results either intentionally or non-intentionally in salamanders, snails, agricultural crops, etc. • Results in larger fruits and larger plants. Rate of Evolution • The ability of a species to survive an environmental change depends greatly on how quickly it evolved the adaptations necessary to thrive and reproduce. – Rate of Environmental Change – Genetic Variation – Population Size – Generation time