What is Evolution Simply Change Over Time Biologic

What is Evolution? Simply: Change Over Time Biologic Evolution the change in species over time A. K. A. descent with modification This definition encompasses: small-scale evolution changes in gene frequency in a population from one generation to the next large-scale evolution the descent of different species from a common ancestor over many generations).

Mechanisms of Evolution The processes of evolution Evolution is the process by which modern organisms have descended from ancient ancestors. Evolution is responsible for both the remarkable similarities we see across all life and the amazing diversity of that life — but exactly how does it work? Fundamental to the process is genetic variation upon which selective forces can act in order for evolution to occur. We will focus on: Descent and the genetic differences that are heritable and passed on to the next generation; Mutation, migration (gene flow), genetic drift, and natural selection as mechanisms of change; The importance of genetic variation; The random nature of genetic drift and the effects of a reduction in genetic variation; How variation, differential reproduction, and heredity result in evolution by natural selection; and How different species can affect each other's evolution through coevolution.

What is natural selection? • The process in nature that results in the most fit (best adapted) organisms producing offspring. • 3 steps: variation --> selection --> reproduction Survival of the Fittest Individuals with characteristics best suited to their environment survive. Individuals in a population who are best suited to the environment will be selected for (survive) and pass their genes (and traits) to their offspring.

What is the relationship between variation and fitness? ➢ Variation • Differences amongst individuals in a population (both in genes and physical traits), that result from sexual reproduction. ➢ Fitness • The combination of physical traits and behaviors that help an organism survive and reproduce in its environment. Populations of organisms have a variety of physical traits and behaviors. Certain individuals have traits and behaviors that are better suited to certain environments than others.

What is the relationship between variation and genes? ➢ Variation • Differences amongst individuals in a population (both in genes and physical traits), that result from sexual reproduction. ➢ Genes • Sections of DNA that code for particular traits Populations of organisms have a variety of different genes. The genes provide the variations where some are better suited to certain environments than others.

➢ What is the relationship between fitness and survival of the fittest? Fitness • The combination of physical traits and behaviors that help an organism survive and reproduce in its environment. ➢ Survival of the Fittest • Individuals with characteristics best suited to their environment survive. Individuals in a population who have the best fitness (best suited traits and behaviors) will survive.

What is the relationship between natural selection and adaptation? ➢ Natural Selection • The process in nature that results in the most fit (best adapted) organisms producing offspring. • 3 steps: variation --> selection --> reproduction. ➢ Adaptation • The process that enables organisms to become better suited to their environment. Through the process of natural selection (variation --> selection --> reproduction) , populations of organisms become better adapted to their environment over time.

Influences on Evolution Genetic Drift Gene Flow Mutations

Genetic Drift ➢ Genetic Drift • Genetic change in a population, occurring in the absence of natural selection, due to random, chance events. ➢ Examples of events leading to genetic drift: - mutation - chance dispersal - extreme weather conditions

Gene Flow ➢ Gene Flow • Transfer of alleles (genes) from one population to another. ➢ Examples of events leading to genetic drift: • Migration - Immigration: organisms with certain alleles moving into a population - Emigration: organisms with certain alleles moving out of a population

Mutations ➢ Mutations • A change in the genetic sequence - they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes ➢ Examples of events leading to mutations: • Random mutation during DNA replication or protein synthesis • Environmental factors such as sunlight, radiation, and smoking