Evolution P2

Modern Air Pollution Control

  • Contributed to cleaner air quality

  • Allowed natural flora like lichen to thrive again

  • Trees showing lighter colors due to decreased pollution

  • Natural Selection Impact: Favor of lighter moths in cleaner air, as darker moths become rare.

Natural Selection Overview

  • Is Natural Selection Random?

    • Not Random: It selects for survival based on better adaptations to the environment, though genetic variations occur by chance through mutations.

  • Is Natural Selection Perfect?

    • No organism is perfectly adapted; perfection is not achieved.

Causes of Genetic Variation

  • Sources of genetic variation include:

    • Germ-line Mutation: Mutations in sperm and egg cells.

    • Gene Duplication or Position Swapping: Alterations in chromosome structure.

    • Chromosomal Changes: Deletion or duplication of entire chromosomes.

    • Sexual Reproduction: New allele combinations arise from meiosis and random mating.

  • Human Genetic Variation: 99.9% DNA similarity among all humans.

Offspring Variation

  • Offspring differ from parents due to:

    • Genetic variation from new allele combinations.

    • Environmental impact on gene expression (e.g., diet influences muscle growth).

Selective Forces in Natural Selection

  • Environmental Pressures: Factors like climate, competition, predation, etc.

  • Differential Reproduction: Organisms with beneficial traits survive better, increasing the chance of those genes in the next generation.

Consequences of Natural Selection

  • Result: Increased frequency of favorable genotypes leading to potential new species formation.

Other Mechanisms of Evolution

  • Polyploidy: Involves chromosome number changes through hybridization that can lead to new species, important in plants.

  • Gene Flow: Movement of genes between populations, can occur via migration and gametes.

  • Genetic Drift: Random changes in allele frequencies significant in small populations.

Artificial Selection

  • Definition: Choosing certain organisms for breeding based on desirable traits, mimicking natural selection but driven by humans.

  • Difference:

    • Artificial Selection: Human-driven, faster rate of change, less variation.

    • Natural Selection: Driven by environmental agents, slower, more variation.

Importance of Artificial Selection

  • Applications:

    • Domestication of wild plants for uniform traits (e.g., wheat, maize).

    • Improvement of livestock for productivity (milk, meat).

    • Resistance breeding for diseases.

    • Development of new crop strains (e.g., broccoli, hybrid rice).

Inbreeding vs. Outbreeding

  • Inbreeding: Mating of closely related individuals, leads to loss of vigor.

    • Examples: Self-fertilization in plants, highly pedigreed animals.

  • Outbreeding: Mating of unrelated individuals leads to more vigorous offspring.

    • Examples: Mongrel dogs showing greater fertility and survival rates.

History of Domestication

  • Domesticated Dog (Canis familiaris):

    • Evolved from grey wolf, selected mainly for behavior and utility traits over time.

  • Domesticated Crop (Zea mays):

    • Teosinte transformed by native Americans into maize through selective planting for beneficial traits.

  • Selected Phenotypes:

    • Reduced seed covering and retention on plant cobs contributed to successful domestication.