Natural selection

• Frequency-dependent selection is a type of natural selection that favors rare traits in a population, leading to a cyclical pattern of trait frequencies over time.
• Natural selection is the process through which species adapt to their environments and is the engine that drives evolution.
• English naturalist Charles Darwin developed the idea of natural selection after a five-year voyage to study plants, animals, and fossils in South America and on islands in the Pacific.
• A species is a group of similar organisms that can reproduce with each other.
• Variation is a difference.
• Natural selection is a process by which organisms that are better-adapted to their environments produce more offspring to transmit their genetic characteristics.
• Speciation is a process by which one or more populations of a species become genetically different enough to form a new species.
• In 1859, Charles Darwin brought the idea of natural selection to the attention of the world in his best-selling book, On the Origin of Species.
• A trait is a characteristic or aspect.
• A predator is an animal that hunts other animals for food.
• Natural selection is the process through which populations of living organisms adapt and change.
• Individuals in a population are naturally variable, meaning that they are all different in some ways.
• This variation means that some individuals have traits better suited to the environment than others.
• Individuals with adaptive traits, traits that give them some advantage, are more likely to survive and reproduce.
• These individuals then pass the adaptive traits on to their offspring.
• Over time, these advantageous traits become more common in the population through the process of natural selection.
• Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species.
• Natural selection is one of the processes that drives evolution and helps to explain the diversity of life on Earth.
• Charles Darwin chose the name natural selection to contrast with “artificial selection,” or selective breeding that is controlled by humans.
• Darwin argued that a process much like artificial selection happened in nature, without any human intervention.
• Darwin argued that natural selection explained how a wide variety of life forms developed over time from a single common ancestor.
• Darwin did not know that genes existed, but he could see that many traits are heritable—passed from parents to offspring.
• Mutations are changes in the structure of the molecules that make up genes, called DNA.
• The mutation of genes is an important source of genetic variation within a population.
• Mutations can be random (for example, when replicating cells make an error while copying DNA ), or happen as a result of exposure to something in the environment, like harmful chemicals or radiation.
• Mutations can be harmful, neutral, or sometimes helpful, resulting in a new, advantageous trait.
• If the environment changes rapidly, some species may not be able to adapt fast enough through natural selection.
• Through studying the fossil record, we know that many of the organisms that once lived on Earth are now extinct.
• An invasive species, a disease organism, a catastrophic environmental change, or a highly successful predator can all contribute to the extinction of species.
• Today, human actions such as overhunting and the destruction of habitats are the main cause of extinctions.
• Extinctions seem to be occurring at a much faster rate today than they did in the past, as shown in the fossil record.
• Natural selection and genetic drift are topics discussed in 9.3 & 9.4.
• The two main parts of the nervous system are the Central nervous system (CNS) which includes the brain and spinal cord, and the Peripheral nervous system (PNS) which includes the receptors, muscles, glands, and ganglia.