Evolution: Process, Heredity & Mechanisms

• Evolution is the process of developmental changes in a population of organisms over time due to changes in their genomes across generations.
• Heredity, the transfer of genetic material within chromosomes from parent to offspring, is a key factor in evolution.
• Genomes, the sets of genes in an organism's DNA or RNA, change over time due to internal and external factors.
• Environmental changes are a major driver of evolution.
• Charles Darwin and Alfred Wallace are key figures in the development of the Theory of Evolution.
• The Theory of Evolution is the most widely accepted explanation for how life has changed into its current forms.
• Organisms must adapt and change to pass on their genes as environments and competition between organisms shifts.
• It is populations, not individual organisms, that evolve over time.

Mechanisms of Evolution

• Catastrophism and gradualism are two major mechanisms of evolution.
• Adaptation and status (stasis) also play parts in understanding differing traits within a population of a species.

Catastrophism vs. Gradualism

• Catastrophism involves sudden, destructive events leading to mass die-offs followed by the emergence of new organisms.
• Georges Cuvier developed the theory of catastrophism.
• Cuvier found evidence of localized mass extinctions in the Paris Basin fossil record.
• Catastrophism can explain the mass extinction of dinosaurs.
• Gradualism is slow change within a genome over time without mass extinction markers.
• James Hutton developed the theory of gradualism.
• Hutton's studies show a gradual emergence of new traits with no breaks in the fossil record.
• Gradualism involves small changes accumulating over long periods.
• The theory of gradualism implies that evolution is always occurring because the environment is always changing.
• An example of evolution is antibiotic-resistant bacteria
• Bacteria with genes that make them resistant to antibiotics thrive while those without die off
• Resistant bacteria pass on the advantage to new generations, changing the genome.

Adaptation vs. Status

• Adaptation is a trait change that provides an advantage in a changing environment.
• Adaptation can involve individual genes or multiple genes affecting multiple traits.
• Status (stasis) is when a trait remains unchanged because it continues to be advantageous for survival.

Punctuated Equilibrium

• Punctuated equilibrium describes long periods of little change in a population, followed by short bursts of significant change.
• Evidence for punctuated equilibrium is found in fossil records showing rapid changes or new species emerging after long periods of stability.
• Camouflage, such as stripes on tigers is an example of punctuated equilibrium.
• Striped tigers can hide and stalk prey, unlike the non striped tigers, therefore they die out.

Adaptive Radiation

• Adaptive radiation occurs when many species with different traits emerge from one common ancestor.
• Differences are often due to differing environments or niches within the same environment.
• Melanin in human skin is an example, with light skin in low-UV environments for vitamin D production and dark skin in high-UV environments for sun protection.

Descent with Modification

• Descent with modification refers to the passing of genome changes from parent to offspring, leading to population evolution.

What Causes Evolution?

• Heredity is integral allowing the population to survive.
• Natural selection, random genetic drift, and sexual selection are factors that act on the inheritance of traits.
• Natural selection involves adaptations in an organism's genome that improve survival chances, which are then passed to offspring.
• Random genetic drift involves changes in genes due to mutation or random gene combinations during reproduction.
• Random genetic drift doesn't rely on natural selection.
• Sexual selection involves traits selected for mating purposes, even if they don't improve survival.

Types of Evolution

• Divergent, convergent, and parallel evolution are the three main types of evolution.

Divergent Evolution

• Divergent evolution occurs when closely related species develop different phenotypes and traits.
• An example is the Galapagos finches, who developed different beak shapes based on their diets to reduce competition.

Convergent Evolution

• Convergent evolution occurs when unrelated species develop similar features.
• Birds and bat wings have very similar structures, but the species are not closely related.
• These traits develop due to similar needs and environments but are separate from one another.

Parallel Evolution

• Parallel evolution occurs when distantly related species independently develop similar adaptations.
• The structures and functions of leaves are similar across many plants.

Examples of Evolution

• Habitat changes over time often drives evolution.
• Penguins have adapted flippers to swim swiftly through water to catch fast fish.

Evolution is the process of changes in a population of organisms over time. Heredity is a key factor in evolution. Genomes, sets of genes in an organism's DNA or RNA, change over time due to internal and external factors.