bio 2-9

Location: Galapagos Archipelago, specifically Daphnia Major.
Focus of Study: Researchers studied the medium ground finch, focusing on the variation of beak depth within the population.
- Aim: To measure and analyze the average beak size across various members of the population.
- Key Finding: There was significant variation in beak depth; some birds had shallow beaks while others possessed larger, deeper beaks.

Condition for Natural Selection: Variation must be present within a population for natural selection to occur.
- Observations: Changes in beak depth year-over-year, influenced by environmental factors.
- Predictability: Researchers could predict changes in beak depth based on the availability of resources (i.e., food sources such as seeds).

Drought Years: Larger, harder seeds become dominant; birds with deeper beaks have higher survival rates.
Wet Years: Increased availability of smaller seeds; birds with smaller beaks are favored.
Graphical Representation:
- Axes: Y-axis shows mean offspring beak depth; X-axis shows mean parental beak depth.
- Correlation: As parental beak depth increases, offspring beak depth also increases, indicating a positive correlation.
- Implication: Traits such as beak size are passed down from parents to their offspring, supporting natural selection.

Contrary to directional selection, oscillating selection leads to back and forth shifts in trait popularity.
Instead of a constant increase in beak size over time, sizes hover around the mean depending on yearly environmental factors.

Evolutionary changes can be slow (millions of years) and not immediately noticeable across generations.
- Small changes accumulate over time, leading to larger changes in the population's traits.

Scientific Name: Biston betularia.
Phenotypic Variation: Two primary color variations: light (recessive) and melanic (dominant).
- Melanic variants were rare until the industrial age.
Impact of Industrial Revolution:
- Increased pollution led to darker trees due to soot; this favored the melanic moths as they were less visible to predators.
- Rapid increase in melanic moths’ prevalence during the 1850s.

Researchers like JW Tutt conducted studies to affirm that lighter moths suffered higher predation due to visibility against soot-darkened trees.
- Evidence: Experimental tagging and recapture of moths showed lighter variants were more frequently predated upon.

Natural Selection: Involves pressures such as predation that favor certain traits over others, resulting in changes in allele frequency over time.
- The shift toward greater representation of the melanic forms indicates strong selection pressures.
Artificial Selection: Human-driven selection can similarly affect trait frequency quickly.
- Examples include selective breeding of crops or animals leading to rapid changes in desired traits.

Selection Studies on bristle numbers: Tracks the bristle count as a phenotypic trait.
- Selective breeding based on bristle numbers had drastic effects on population averages within just a few generations.

Ancestral Plants: Tiosynth, a wild ancestor of modern corn, showcases substantial changes through human selection.
- Increased oil content: From 4.5% to over 20% in under 100 years due to selective breeding.

Dog Breeding: Domestication of dogs resulted from selective breeding for various traits, leading to the stunning diversity observed today, from mastiffs to chihuahuas.
- Different breeds were often specialized for various tasks such as hunting, pest control, or companionship.

Fur color or size changes can occur due to selection pressures, both artificial (human-imposed) and natural (wild environments).