B4 - Adaptation, Variation, and Natural Selection (Updated 2024) PDF

B4 - Adaptation, Variation, and Natural Selection I can… Explain that variations result from heritable mutations that have a selective advantage Discuss the importance of sexual reproduction with regards to individual variation and evolution Variation In all organisms, visible di...

B4 - Adaptation, Variation, and Natural Selection I can… Explain that variations result from heritable mutations that have a selective advantage Discuss the importance of sexual reproduction with regards to individual variation and evolution Variation In all organisms, visible differences may be observed, called variations Variations can occur both between different species (interspecific variation) and within the same species (intraspecific variation) Variation = survival! Variation and Survival Variation within a species is largely the result of sexual reproduction In sexual reproduction, offspring inherit 50% of their DNA from each parent, resulting in a new combination of genes and therefore new characteristics Variations that give an individual a better chance of surviving to reproduce will be passed onto offspring ○ Through generations, this variation will become more and more common in a particular population ○ Such variations are called adaptations Variation and Survival Phylogeny: The history of the evolution of a species or a group of organisms ○ Studies how variation arises in the first place Adaptations Adaptation: Structural, behavioral, physiological processes that help an organism to survive and reproduce in a particular environment (ex. camouflage) ○ Structural: How it looks Ex. Owls - long talons help them to be better predators ○ Behavioral: How it behaves Ex. Geese - migrate to a warmer place in the winter The American bittern is well ○ Physiological: What it does camouflaged among plants in its Ex. Scorpion - ability to produce habitat. venom/poison  Mutations In order to reproduce, DNA within the nucleus of cells must first replicate and divide The process of DNA replication is not perfect; mistakes are often made Small changes in the genetic code are A. Normal, healthy red blood cell. referred to as mutations, and result in B. Sickled blood cell, is a mutated gene that changes in gene expression can be inherited from parents. ○ Mutations are thus another cause of variation. Types of Mutations Neutral mutation: No effect on the organism Harmful mutation: Mutation that reduces an organism’s fitness Beneficial mutation: Mutation that enhances an organism’s fitness Mutations and Selective Advantage Some mutations produce a change in individual that is beneficial Mutations that increase individuals’ chance of survival will most likely be passed on to next generation Mutations are more common in situations when the organism’s environment is changing ○ Mutation provides selective advantage in new environment Natural Selection Natural selection: Process that results when traits that increase an organism’s chance of survival to reproductive age are more likely to be passed onto future generations. As a result, these traits become more common in a population, causing that population to change over time Natural Selection and Environment Whether or not a particular trait is selected for or selected against depends entirely on the organism's environment at that moment in time; thus, changes in the various traits of a given population are driven by environmental change These mice are the same species, but are different colours. Why might the mice have this adaptation? Natural Selection and Environment Natural selection doesn’t anticipate changes in environment Random changes occur and produce traits that may benefit organism in future When the environment changes, then those variations that have been produced increase ability of some organisms to survive ○ If variation is detrimental, it’s unlikely that it will be passed on until environment changes to select for that variation Example of Natural Selection Skin colour! Humans need sunlight to survive as it permits the absorption of vitamin D Without any protection from the sun, harsh UV rays can damage cells Artificial Selection Artificial selection: The process of humans selecting and breeding individuals with the desired traits Today’s domestic animals and crop plants have been artificially selected over many hundreds of generations Provides compelling evidence that similar and more dramatic changes occur in nature over millions of years and countless generations