B4 - Adaptation, Variation, and Natural Selection

Adaptation, Variation, and Natural Selection

• Adaptation is a structural, behavioral, or physiological process that aids survival and reproduction in a particular environment (e.g., camouflage).
• Variation in organisms can be observed both between species (interspecific) and within the same species (intraspecific). Variation is crucial for survival.
• Variation arises from heritable mutations that confer a selective advantage.
• Sexual reproduction fosters variation by combining genetic material from two parents, creating new gene combinations in offspring.
• Variations that increase survival and reproduction become more common in a population across generations, becoming adaptations.

Variation

• Variations are visible differences among organisms.
• Variations are crucial for survival as they allow organisms to adapt to their environment.
• Variation can occur between different species (interspecific variation) and within the same species (intraspecific variation).

Variation and Survival

• Variation within a species is primarily due to sexual reproduction.
• Offspring inherit 50% of their DNA from each parent, producing new combinations of genes and characteristics.
• Variations that promote survival and reproduction are passed down to more offspring.
• These variations become more common in a population through generations—becoming adaptations over time.

Phylogeny

• Phylogeny is the evolutionary history of a species or group of organisms.
• It studies how variations arise in the first place.

Adaptations

• Adaptation: Structural, behavioral, or physiological processes that aid survival and reproduction.
• Structural Adaptations – Physical characteristics, examples include eagle's talons, long legs on a giraffe for reaching high branches
• Behavioral Adaptations – An animal's actions—examples: migration (birds, certain insects), hibernation.
• Physiological Adaptations – An organism's internal workings—examples: venom production (snakes, spiders), photosynthesis.

Mutations

• In order to reproduce, DNA within cell nuclei must replicate and divide.
• DNA replication isn't perfect; mistakes occur during replication.
• These small genetic code changes are called mutations.
• Mutations result in gene expression changes.
• Mutations are a source of variation.

Types of Mutations

• Neutral mutation – No effect on the organism.
• Harmful mutation – Reduces an organism's fitness (likelihood of survival and reproduction).
• Beneficial mutation – Enhances an organism's fitness.

Mutations and Selective Advantage

• Some mutations produce beneficial changes in individuals.
• Mutations that increase an individual's chance of survival are more likely to be passed on to the next generation.
• Mutations are more frequent in changing environments.
• The resulting mutation can provide a selective advantage in new environments.

Natural Selection

• Natural selection is a process where traits that improve an organism's chance of survival to reproductive age are passed down to future generations.
• These traits become more common in a population, causing it to evolve over time.

Natural Selection and Environment

• Whether a trait is selected for or against depends on the organism's current environment.
• Changes in the environment can drive changes in the traits of a population.
• Populations adapt to their environment.

Example of Natural Selection (Skin Colour)

• Humans need sunlight to absorb Vitamin D.
• Harsh UV rays from sunlight damage cells without protection.
• Skin colour is an adaptation to environmental pressures (sun exposure).
• Individuals with skin colours better absorbing vitamin D in high UV environments are more likely to survive and successfully reproduce.

Artificial Selection

• Artificial selection is the process where humans select and breed individuals with desired traits.
• Domestic animals and crop plants have been artificially selected over generations.
• Artificial selection provides an example of how dramatic evolutionary change can be achieved over relatively short periods.

Explore the concepts of adaptation, variation, and natural selection in this quiz. Learn how structural, behavioral, and physiological adaptations aid survival, and understand the importance of genetic variation among and within species. Test your knowledge on how these processes drive evolution and species diversity.