D4.1

Key Components of Natural Selection:
- Overpopulation of offspring
- Variation within the population
- Struggle for survival
- Differential survival
- Reproduction and passing on of desirable traits
Population vs. Individual Level:
- The phenomena occurring at the population level are more significant than those at the individual level.

Main Sources of Variation:
- Mutation:
  - A change in the DNA sequence, typically occurring during DNA replication.
  - Mutations can be classified as good, bad, or neutral.
- Meiosis:
  - A reduction division process generating gametes, each genetically distinct and containing 50% genetic information from each parent.
  - Random orientation and crossing-over during meiosis contribute to variation.
- Sexual Reproduction:
  - Asexual reproduction results in genetically identical offspring, while sexual reproduction leads to variation, as gametes and mating individuals are both random.
Impact of Variation:
- Variation facilitates natural selection; frequencies of desirable traits increase, while less desirable traits decrease in a population.

Many organisms produce more offspring than can survive, resulting in competition for limited resources.
Carrying Capacity:
- Refers to the maximum number of individuals an environment can support.
- Limited resources, such as food, habitat, and water, can lower carrying capacity.
Struggle for Survival:
- A crucial element of natural selection, driven by competition.

Definition:
- A factor that influences survival and reproduction, thereby altering allele frequencies in a population.
Types of Factors:
- Abiotic Factors: Non-living factors affecting survival (light, pH, minerals, gases).
- Density-Independent Factors: Impact populations regardless of size, e.g., environmental changes affecting species adaptability, like climate change affecting penguins' ability to stay warm.

Definition:
- Competition amongst individuals of the same species.
Fitness:
- A measure of an individual’s ability to survive and reproduce; higher fitness generally corresponds to greater success than lower fitness.
Adaptation:
- Most organisms cannot consciously adapt; survival traits are typically inherited (e.g., camouflaged plover eggs).
Reproductive Potential:
- The maximum number of offspring an organism can produce without mortality factors affecting offspring.

Definition:
- A process where an individual's reproductive success is determined by physical and behavioral traits.
Examples:
- Birds of Paradise:
  - Sexual dimorphism is evident as males display bright colors and long tails to attract females, who are typically cryptic for camouflage.
  - Males compete for females—a manifestation of intrasexual competition.

Definition:
- Traits encoded in an organism's DNA that are passed to subsequent generations.
Acquired Characteristics:
- Traits developed during an individual’s lifetime that cannot be inherited (e.g., pink flamingos' color from diet, not genetics).
Lamarckism:
- The disproven idea that acquired traits during an organism's lifetime can be passed to offspring.

Conducted in 1970 to analyze the impact of predators on guppy coloration.
Methodology:
- Experiments conducted in various environments (natural and artificial) with and without predators for 15 generations.

Graphs represent various experimental conditions (e.g., ponds with no predators vs. those with harmless and dangerous species).
- Key questions focus on results comparison and addressing experimental design flaws.

Definition:
- The complete set of genetic information in reproductive individuals of a population.
Inbreeding:
- Can narrow the gene pool, affecting genetic diversity.
Allele Frequency:
- The proportion of a specific allele in a population, indicating genetic variability.
New alleles emerge through mutations or the introduction of new organisms.

Isolation leads to differing allele frequencies and can result in the emergence of new species.
Example:
- HLA complex in humans determines immune self-recognition; variations can impact transplant compatibility.

Example:
- Peppered Moth: Changes in allele frequency before and after the industrial revolution due to environmental factors affecting camouflage and survival.

Directional Selection:
- Favors one phenotype (e.g., dark-colored moths post-industrial revolution).
Stabilizing Selection:
- Non-extreme traits are favored (e.g., human birth weight).
Disruptive Selection:
- Both extremes of a trait are favored over intermediate phenotypes (e.g., survival of grey and Himalayan rabbits).

States conditions for allele frequency calculation within a stable population.
Equation:
- p² + 2pq + q² = 1
- p = frequency of dominant allele, q = frequency of recessive allele
- p + q = 1

Example problem calculating recessive allele frequency in a population based on disease occurrence.

Assumptions Required for Hardy-Weinberg Equation:
- Stable allele frequencies, diploid organisms, large population, sexual reproduction, random mating, no migration, and non-deleterious alleles.

Definition:
- Human-directed selection for specific traits in organisms through breeding.
Consequences:
- Unintended effects of artificial selection can lead to resistance in pathogens due to natural selection.