Mechanisms for the Diversity of Life Biology 1-4 Mechanisms for the Diversity of Life

1-4C: Natural Selection The process that makes genetic change possible in living things is called natural selection. Members of a species that have certain characteristics that give them an advantage over other members of the species will be more likely to survive and reproduce, thus passing on their genetic information to the next generation.

1-4C: Natural Selection One of the most famous examples of natural selection is the Galapagos Finch Scientists believe that all 13 species of finch that now live on the Galapagos Islands (off the coast of Ecuador) developed from a single species that came from mainland South America.

1-4C: Natural Selection The birds changed due to environmental pressures, sometimes called selective pressure Because they were competing for the same resources, like food, those who were able to occupy a slightly different niche did better They survived and produced young birds with the same traits. A niche is the role an organism plays in its environment What it eats, where it lives, etc.

1-4C: Natural Selection If the finches could occupy slightly different niches, they wouldn’t have to compete with each other so much!

1-4C: Natural Selection Adaptive Radiation happens when a single species changes over time into a number of different species like the Galapagos finches

1-4C: Natural Selection An adaptation is a feature of an organisms body that helps it to survive. There are three main types of adaptations: Structural Adaptation Physiological Adaptation Behavioural Adaptation

1-4C: Natural Selection When organisms are not equipped to survive in their environment, extinction can take place.

1-4D: Artificial Selection Artificial selection is the intentional breeding of plants and animals. It is the same as selective breeding.

1-4D: Artificial Selection By crossing only plants or animals that have desirable characteristics, the breeder can improve the next generation. It can take a lot of time and many generations to reach an “ideal”.

1-4D: Artificial Selection Once a breeder has an “ideal” plant or animal, they want to continue producing the same type of individual. Inbreeding is commonly used to do this. Closely related stock that has similar traits are bred together to maintain the ideal.

1-4D: Artificial Selection Many varieties of purebred dogs are the result of generations of careful inbreeding, but it does have its risks Because most of the members of an inbred line are genetically similar, the chances that negative genetic defects will show up become much greater Problems in many dog breeds, such as hip and elbow problems, have resulted from repeated inbreeding

1-4D: Artificial Selection Hybrization is a cross between individuals that have different genetic makeups. Often the individuals are different (but related) species. The offspring are called hybrids and are often hardier than the parents This is called cross-breeding.

1-4D: Artificial Selection A lot of modern farms use monoculture farming, meaning that only one type of species is grown. It increases the efficiency of planting and harvest, but it can cause problems when the same crop is grown over and over again in the same area. Nutrients used by that crop get used up, and pests and disease can build up more rapidly over time.

1-4D: Artificial Selection In Ireland, growing only one kind of potato, the “lumper”, led to the Great Famine in the 1840’s Potatoes were cheap food for the masses, but they were grown in monocultures with little genetic variety When the potatoes were infected with a disease called potato blight, almost all the crops in Ireland failed, resulting in many people starving.

1-4D: Artificial Selection Polyculture involves growing more than one species in an area at a time.