Genetics and Evolution Study Notes

Taxonomy is the branch of biology that identifies, names, and classifies species.
Developed by Carolus Linnaeus, a Swedish scientist.
The Linnaean system has two main components:
- Binomial nomenclature: Each species has a two-part name.
- Genus: The first part indicating a group of closely related species.
- Specific epithet: The second part that distinguishes between species within a genus.
- Hierarchical classification: Organisms are classified into a hierarchy starting from species to broader groups (family, order, class, phylum, kingdom, domain).

Lamarck proposed that evolution is the refinement of traits that help organisms succeed in their environments.
He introduced the idea that traits acquired or diminished during an organism's life could be passed on to offspring, a concept now known as inheritance of acquired characteristics.
While his mechanism was incorrect, he recognized the role of environmental interactions in evolutionary changes, influencing later thinkers like Darwin.

Darwin began his foundational voyage at age 22 on HMS Beagle, which aimed to chart parts of the South American coastline.
He formulated his theory of evolution, emphasizing natural selection as the mechanism for evolution.
Natural selection suggests that individuals with favorable traits are more likely to survive and reproduce.

Fossils are imprints or remains of ancient organisms, providing a historical record of life.
They reveal significant changes in organisms over time and show the extinction of various species.
Limitations of the fossil record include:
- Bias towards organisms in environments conducive to fossilization.
- Many fossils being distorted or destroyed through geological processes.
- Inaccessibility of certain fossils to paleontologists.

Homology: Analyzes similarities among organisms due to common ancestry.
Vestigial structures: Remnants from ancestral forms that serve little to no function in current organisms (e.g., human appendix).

Darwin visualized evolution as a tree depicting relationships among species.
The trunk symbolizes the first organisms, with branches representing the diversity of species today.
Each fork represents a common ancestor from which evolutionary paths diverged.

Artificial selection involves selective breeding of domesticated plants and animals to enhance desirable traits.
Two essential components:
- Variation: Differences among individuals (e.g., coat types in puppies).
- Heritability: The ability to pass traits from parents to offspring. Traits that are not heritable cannot be selected for improvement.

A population consists of individuals of the same species that interbreed in a shared area.
The gene pool encompasses all allele variations within that population.

The three primary drivers of evolutionary change are:
- Natural selection
- Genetic drift
- Gene flow

Genetic drift occurs when population sizes shrink, leading to a loss of genetic diversity.
Causes include:
- Bottleneck effect: A drastic reduction in population size.
- Founder effect: A small group establishes a new population.

Types of natural selection:
- Directional selection: Favors one extreme phenotype.
- Disruptive selection: Favors extreme phenotypes at both ends.
- Stabilizing selection: Favors intermediate phenotypes.

Reproductive barriers prevent interbreeding between closely related species and can be classified as:
- Prezygotic barriers: Prevent mating or fertilization before the zygote is formed.
- Temporal isolation: Different breeding times.
- Habitat isolation: Different living areas.
- Behavioral isolation: Different mating rituals.
- Mechanical isolation: Physical incompatibilities.
- Gametic isolation: Incompatibility of gametes.
- Postzygotic barriers: Occur after zygote formation, affecting hybrid viability and fertility.
- Reduced hybrid viability: Some hybrids do not survive.
- Reduced hybrid fertility: Hybrids may be sterile (e.g., mules).

Understanding these concepts is essential for grasping the principles of biological classification and evolution. Each point represents a fundamental component of the broader picture of life on Earth and the processes that have shaped biodiversity over time.