Genetics and Natural Selection Study Notes

Genetics

• Genetics: The study of biological inheritance patterns and variation.
• Alleles: Different forms of a gene.
• Law of Dominance:
  • Dominant allele is always expressed; represented by uppercase letter.
  • Recessive allele is expressed only when dominant allele is not present; it is represented by lowercase letter.
• Homozygous: When alleles are represented by the same letter (e.g., AA or aa).
• Heterozygous: Both alleles are present, but the dominant allele is expressed (e.g., Aa).
• Law of Segregation: Alleles separate during meiosis.
• Law of Independent Assortment: Genes that segregate independently do not influence each other’s inheritance. This helps account for the many genetic variations observed in sexually reproducing organisms.
• Dominant Allele Expression: Expressed if one copy is present (AA or Aa).
• Recessive Allele Expression: Two copies of the allele are required to be expressed (aa).
• Genotype: The genetic makeup; the gene itself (AA, aa, or Aa).
• Phenotype: Describes what the gene is expressing (e.g., black eyes or blue eyes).
• Genotypes:
  • Homozygous dominant (AA)
  • Homozygous recessive (aa)
  • Heterozygous (Aa)

Example

Let's consider:

• A = black eyes
• a = blue eyes
• B = brown hair
• b = blond hair

Punnett Square Example:

Natural Selection

• Natural selection explains how evolution can occur and how organisms adapt to survive.

• Factors of natural selection:

  • Predators
  • Climate
  • Competition
  • Diseases

  These factors determine if a species survives or not.

• Artificial Selection: Used to alter organisms to express desired traits.

Types of Natural Selection

• Overproduction: Producing more offspring than can survive.
• Variation: Heritable differences among individuals.
• Adaptation: A feature that allows an organism to better survive in its environment.
• Descent with Modification: Over time, natural selection will produce more individuals with advantageous traits.

Key Concepts in Natural Selection

• Variation: Differences in a population are crucial.
• Inheritance: Traits are inherited from parents to offspring.
• Selection: Some traits are more advantageous than others, leading to "survival of the fittest."
• Natural selection is a gradual process, not abrupt.
• Adaptation is critical; organisms must adapt to survive.

Evolutionary Structures

• Homologous Structures: Same underlying structures, different functions.
• Analogous Structures: Different structures, same function.
• Vestigial Structures: Structures reduced in size through evolution (e.g., appendix).

Viruses

• How Viruses Reproduce:
  • Attachment
  • Replication
  • Entry
• Good Bacteria: Bacteria in your gut.
• Bad Viruses: Example: COVID-19.

Protists

• Different Types of Protists:
  • Zooplankton
  • Protozoa (Animal-like protists)
  • Algae (Plant-like protists)
  • Fungi-like (Mold)
• Protist Function: Used to help an organism obtain resources from the environment.

Fungi

• Multicellular
  • Cell Wall Composition: Chitin
  • Examples: Mushrooms
• Protists
  • Unicellular
  • Cell Wall Composition: Cellulose
  • Examples: Algae (seaweed)
• Fungi Structure: Hyphae, Mycelium, and Fruiting Body
• Fungi Classification: Based on different reproductive structures.
• Beneficial Fungi: Decomposition, medicine, and food.
• Harmful Fungi: Mold can be detrimental to health.

Plants

• Monocots: One seed leaf, parallel veins.
• Dicots: Two seed leaves, branching veins.
• Seed: Embryonic plant.
• Woody Plants: Hard and thick stems.
• Herbaceous Plants: Soft stems.
• Guard Cells: Help with gas exchange and monitor water loss using turgor pressure.
• Flowers: Contain male (stamen) and female (carpel) parts.

Animals

• General characteristic: Animals are cellular and have no cell walls
• Earthworms: Bilateral symmetry, segmentation (septum).
• Clams: Bilateral and coelomate
• Crayfish: Bilateral symmetry, coelomate, jointed appendages.