Transcript A-1 Notes
Unit A: Biological Diversity Topic 1: Biological Diversity and Survival Variations Variations are differences between organisms caused by genetic and environmental factors. A genetic difference could include being born with gray eyes. An environmental factor could include height and nutrition. Eating a poor diet will result in a shorter person than if that same person ate a healthy diet with protein and calcium. Variation Between Species There is variation between species, and within a species. Biological diversity is the number and variety of organisms in an area. The more biological diversity in an area, the healthier the environment of this area. A species is a single class of living things. Only members of the same species can reproduce healthy offspring. Variation Inside a Species There may be variation inside a species (different breeds of dogs), but as long as reproduction is possible, the organisms belong to the same species. A lion and tiger can, very rarely, produce offspring together; however, the ‘liger’ cubs never live past three months. Therefore lions and tigers are two different species. Speciation Speciation is the process where one group of one species, gradually adapts to its own habitat and becomes so different genetically, that it becomes its own species. Lions and tigers were once part of the same species, but over time, and through evolution, they have diverged into two species. Variations and Adaptations Variations occur all the time. Every organism has their genetic material change randomly when they are developing in the womb. A certain variation becomes common in a group or species when it helps the organism adapt to its environment. There are two kinds of adaptations: Structural Adaptations I. Structural Adaptations – adaptations that are physical, resulting in changes to the bodily structure. An example would be the adaptation of the polar bear to have white fur, allowing polar bears to camouflage themselves in snow. A human example would be our brains which have evolved to have large areas devoted to thinking and planning. This structural adaptation has allowed us to work together and use tools. Behavioural Adaptations II. Behavioural Adaptations – Adaptations that change the way a species act. An example would be the tendency to hunt in packs (lions, wolves) or alone (shark, snakes). A human example would include shivering when you are cold. Importance of Variation Variation is a good thing for survival. If the members of a species are too similar, than one catastrophe could wipe out the entire species. In the Middle Ages 1/3 the population of Europe and Asia died from the Bubonic Plague. Had there been less variation in the human species, the entire human populations in these areas might have been wiped out. Importance of Variation The same thing applies to different species. Because different species of dinosaurs were similar genetically, most of the species were wiped out 60 million years ago. Diversity Index The diversity index is a measurement that measures the health of an ecosystem. It compares the diversity of the number of species (runs) in an ecosystem with the # of organisms. The more variety in kinds of species in an ecosystem, the higher the diversity index. DI = # of Runs / # of Organisms Bottleneck Events Catastrophic events which can wipe out a species/population. One such event occurred 70000 y.a. Human species reduced to 100010000. Survivors now better suited to volcanic eruptions.