7.4 Natural selection

• Advantageous Feature: An advantageous feature, in the context of natural selection, refers to a trait or characteristic of an organism that provides a survival or reproductive advantage in its environment. These features enhance an organism's ability to adapt to its surroundings, increasing its chances of survival and reproduction. Over time, advantageous features become more prevalent in a population due to natural selection.
• Natural Selection: Natural selection is the process by which organisms with traits that are better suited to their environment tend to survive and reproduce more successfully than those with less advantageous traits. This differential reproductive success leads to the gradual change of traits within a population over successive generations. Natural selection acts on heritable variations in a population, promoting the transmission of advantageous traits and ultimately driving evolutionary change.
• Resistant: In the context of natural selection, resistance refers to the ability of an organism or population to withstand the effects of selective pressures, such as predation, disease, or environmental challenges. Organisms that possess resistance to these pressures are more likely to survive and reproduce, passing on their resistant traits to future generations. Over time, resistance can become more prevalent in a population through the process of natural selection, leading to the evolution of adaptive traits.
• 1. In every species, there is variation among individual organisms.
  2. Some of this variation is caused by differences in their genes.
• 1. Some individuals have features that make it more likely that they will survive than individuals who do not have these features.
  2. The individuals with these advantageous features are therefore more likely to reproduce and pass on the genes that produce the advantageous features to their offspring.
  3. Over many generations, the genes that produce these advantageous features become a little bit more common, and the genes that are not so useful become a little bit less common.
• Within a population of bacteria, there is genetic variation
• Some bacteria may have mutations or genes that confer resistance to certain antibiotics, while others do not
• When antibiotics are introduced into the environment, they exert selective pressure on the bacterial population
• Antibiotics kill susceptible bacteria, but resistant bacteria survive
• Resistant bacteria have a survival advantage in the presence of antibiotics
• They can continue to grow and reproduce while susceptible bacteria are killed
• Resistant bacteria are more likely to survive and pass on their resistance traits to their offspring
• Resistant bacteria reproduce and spread within the host organism or to other individuals in the environment
• Transmission of resistance genes can occur through mechanisms such as binary fission, conjugation, or transformation
• Over time, the prevalence of antibiotic-resistant bacteria increases in the population
• The effectiveness of the antibiotic decreases
• This process is driven by natural selection, as the selective advantage conferred by resistance traits leads to their spread and persistence in the bacterial population
• What is Extinction?Extinction is the permanent loss of a species from the Earth. It occurs when the last individual of a species dies, and there are no more living members of that species left anywhere in the world.
• Why Does Extinction Occur?Extinction can happen for various reasons, including natural events like climate change, geological events like volcanic eruptions or asteroid impacts, as well as human activities such as habitat destruction, pollution, overhunting, and introduction of invasive species. These factors can disrupt ecosystems, reduce available resources, and directly harm populations, leading to their decline and eventual extinction.
• When Does Extinction Occur?Extinction events can happen at any time in Earth's history. They have occurred periodically over millions of years due to natural processes, but the rate of extinction has increased dramatically in recent centuries, primarily due to human activities. Mass extinctions, which involve the loss of a large number of species over a relatively short period, have occurred several times in the history of life on Earth.
• How Does Extinction Happen?Extinction can occur gradually over time as populations decline and fail to recover, or it can happen suddenly in events known as mass extinctions. In both cases, the ultimate cause is the inability of a species to adapt to changing environmental conditions or to withstand pressures imposed by natural events or human activities. Extinction often results from a combination of factors, with human impacts playing an increasingly significant role in driving species to extinction in modern times.