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How can the process of evolution by natural selection be modelled? -…
How can the process of evolution by natural selection be modelled?
What is evolution by natural selection?
• 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.
• Over time, these advantageous traits become more common in the population. Through this process of natural selection, favourable traits are transmitted through generations.
• Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species.
• Darwin and other scientists of his day argued that a process much like artificial selection happened in nature, without any human intervention. He 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.
What are the key features of evolution by natural selection?
4 stages
Reproduction
• In order for natural selection to act on a given population, that population must reproduce to create a new generation.
• Over many generations, individuals with traits most suitable for their environment tend to reproduce more than those that don't
• The higher the reproduction rate of a population, the higher the competitive pressure is on an individual to survive. This pressure ensures that only the most suitable members survive while the weaker members perish
Heredity
• Heredity works hand-in-hand with reproduction since the genes of the parents combine to create the genes of their offspring. Parents with advantageous traits must pass those traits on to their offspring in order for natural selection to act.
• Otherwise, the genes which create the advantageous traits would die with the parents without being copied to the next generation.
• Speciation occurs when members of a species are geographically isolated into differing environments, allowing for unrelated lines of heredity.
• Over time, traits in each population begin to differ to better suit them for different environments.
• Given enough time, the number of differences between the populations can become so great that they can no longer interbreed.
Variation in characteristics
• Natural selection can only occur within a population when members of the population have a variation in individual traits.
• For example, a study of natural selection on colour within a population requires different individuals to have varying colours.
• Without a variation in characteristics, there are no traits for nature to "select" over others
Variation in fitness
• In biology, fitness has a more technical meaning than its common definition. Within the context of evolution, fitness is the ability of an organism to survive and reproduce as much as possible.
• Varying levels of fitness in members of a population is a prerequisite for natural selection to occur
• Otherwise, natural selection cannot act to produce more individuals with beneficial traits and fewer with less useful traits.
Explain why natural selection is important for populations?
• 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.
• 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.
• In nature, traits like your family's red hair can have a much greater impact.
• Individuals that develop beneficial traits have a better chance of survival and individuals with less useful traits are weeded out through the process of natural selection
• The greater the variety of traits that exist in a population, the greater the population's chance of survival.
• This is true because a larger number of alleles provides more options for dealing with changes to the environment
Include a real-world example of natural selection, beyond those explored in class, to help support your explanation.
Skeletal adaptations
• Giraffes, lizards, and many other known species adapted to their environments through genetic changes to their skeletons. This form of natural selection meant that members of the population who didn't develop and present these skeletal changes died out
• For example, giraffes developed long necks to reach food sources higher up in trees, so members of the giraffe population who didn't develop a long neck died out
• At the same time, certain lizards in one region developed longer leg bones to help it climb up during periods of flood and to escape predator, shorter legged lizards of the same population died out until only the lizards with the long legs survived