Evolution and Natural Selection

Study Notes

Definition: The process of gradual change in the inherited traits of a population over successive generations.
Impact on biodiversity: Evolution drives the diversification of life on Earth, leading to the incredible variety of plants, animals, and microorganisms we see today.
Natural selection: The process by which organisms with traits better suited to their environment survive and reproduce more successfully, passing those favorable traits onto their offspring.
- Examples: The evolution of camouflage in animals, the development of antibiotic resistance in bacteria, the long necks of giraffes.
- Relationship to evolution: Natural selection is the primary mechanism driving evolution.
Variation and evolution: Variations within a population allow for some individuals to be better adapted to changing environmental conditions, enhancing their survival and reproductive success, thus passing on those advantageous traits and driving the evolutionary process.

Definition: Changes in the sequence of DNA or chromosomes that can alter an organism's traits.
Causes:
- Environmental factors: Radiation, chemicals, viruses.
- Errors during DNA replication: These errors can occur randomly during the copying of DNA.

Selection pressure: A factor that favors certain traits over others in a given environment, leading to the survival and reproduction of individuals with those traits.
- Example: In a population of peppered moths, industrial pollution favored dark-colored moths, increasing their survival and reproduction.
Genetic characteristics and fitness: An organism's genetic makeup determines its traits, which can influence its ability to survive, reproduce, and pass on its genes.

Definition: The intentional breeding of organisms with desirable traits to produce offspring with those traits.
Comparison to natural selection: Selective breeding is a human-directed version of natural selection, where humans choose the traits that promote desired characteristics instead of environmental factors.
Advantages: Used to improve food production, produce healthier livestock, and develop specific traits in plants and animals.
Disadvantages: Can lead to reduced genetic diversity, making populations more susceptible to diseases and environmental changes.
Examples: Breeding cows for increased milk production, developing disease-resistant crops, and creating dog breeds.

Definition: The evolutionary process by which new species arise from existing ones.
Mechanisms:
- Geographical isolation: Physical separation of populations, preventing gene flow and leading to the development of distinct species.
- Reproductive isolation: The inability of individuals from different populations to interbreed, preventing gene flow and driving the divergence of separate species.
- Examples: The evolution of Darwin's finches on the Galapagos Islands (geographic isolation) and the divergence of different species of frogs due to mating calls (reproductive isolation).

Descent with modification; change in the genetic makeup of a population over time.
Biodiversity is the variety of life forms on Earth; evolution creates biodiversity through adaptation to different environments.
Natural Selection is a mechanism of evolution where individuals with traits better suited to their environment survive and reproduce more successfully, passing those traits to offspring.
- Example: Peppered moths in England became darker due to pollution, increasing survival rate.
Variation is crucial for evolution as it provides the raw material for natural selection.
- Example: Some peppered moths already had darker genes, allowing them to blend into the polluted environment and survive.

Changes in DNA or chromosomes altering the genetic makeup of an organism.
Factors that contribute to mutations include:
- Radiation (UV light, X-rays)
- Chemicals (carcinogens)
Natural selection can favor certain mutations, leading to population changes.

An environmental factor that favors certain traits over others.
Example: In a population of bacteria, introducing an antibiotic will create a selection pressure favoring bacteria with resistance genes.
Survival and Reproduction: Organisms with advantageous traits are more likely to survive, reproduce, and pass those traits to offspring.

Artificial selection by humans to breed organisms with desired traits.
Advantages:
- Production of higher-yielding crops
- Improved livestock breeds
Disadvantages:
- Reduced genetic diversity can make populations vulnerable to disease
- Ethical concerns about animal welfare

The formation of new species from existing ones.
Geographical Isolation occurs when populations are separated by physical barriers (e.g., mountains, oceans).
Reproductive Isolation occurs when populations can no longer interbreed, often due to differences in courtship rituals, mating seasons, or other reproductive mechanisms.