Evolution and Mutation Concepts

Evolution

• Evolution is descent with modification, as defined by Charles Darwin.
• Divergent evolution: Related species develop different traits due to differing environments or natural selection. Example: mammoths and elephants from Primelephas.
• Microevolution: Changes in allele frequencies within populations leading to evolution.
• Macroevolution: Formation of new species from existing ones.
• Convergent evolution: Different species evolve similar traits due to similar environments.
• Coevolution: One species evolves in response to another's evolution.
• Environmental pressures: Weather, famine, space limitations, competition for resources (food, mates). Organisms overcoming these pressures are more likely to survive and reproduce.
• Adaptive radiation: A common ancestor diversifies into various adapted species.

Mutation

• Adaptations arise from random heritable mutations in DNA.
• Mutations result from DNA replication errors or environmental mutagens (UV rays, viruses, carcinogens).
• Mutations provide biological advantages.
• Mutations introduce genetic variation, starting point for adaptation.
• Organisms have enzymes to repair faulty DNA.
• Beneficial mutations become characteristics of the species' population.
• Gene flow increases genetic variation by moving alleles between populations.

Structural Adaptations

• Special body features like camouflage, sharp talons, excellent vision, thick fur, thorns, or being poisonous.
• Mimicry is a structural and behavioral adaptation.
• Environmental pressures determine the benefit of variations within a species.

Physiological Adaptations

• Allow organisms to perform specialized functions.
• Hibernation: Physiological and behavioral adaptation reducing metabolism to conserve energy during harsh climates.
• Antibiotic resistance in bacteria (e.g., Staphylococcus aureus).
• Monarch butterflies consuming milkweed to become toxic.

Behavioural Adaptations

• Actions, or behaviours, that aid survival.
• Migration: Moving from one place to another.
• Mating rituals (e.g., lion roars, bird dances) increase reproduction.
• Mimicry is a behavioral adaptation, acting like a harmful species

Environmental Influences

• Environmental stresses (droughts, floods, climate change, human activities) affect variations and drive evolution.

Natural Selection

• A population's traits change over generations due to organisms with advantageous traits surviving more and reproducing.
• Natural selection requires variation within the species.
• Natural selection is not intentional or predictive of environmental change.

Selective Pressure

• Environmental conditions favouring certain traits over others. Pressures can be abiotic (non-living, e.g., climate) or biotic (living, e.g., competition).

Fitness

• An organism's contribution to the gene pool of the next generation, measured in viable offspring. Central to Darwin's theory.

Artificial Selection

• Humans exert selective pressure on a population to gain or modify desirable traits.
• Achieved via selective breeding.
• Very fast, compared to natural selection.
• Reduction of genetic diversity through monoculture (planting the same species). This makes crops vulnerable to disease and environmental issues. Health problems in animals also result.

Evidence of Evolution

• Fossil record: History of different species preserved in rock layers.
• Transitional fossils: Show links between groups of organisms (e.g., Archaeopteryx, dinosaur-bird characteristics).
• Vestigial structures: Reduced forms of structures functional in ancestors.
• Biogeography: Study of geographical distribution of organisms.
• Anatomy: Studying body structures and functions, ex. vertebrates using their bones for different uses.
• Homologous structures: Similar structure and origin, though function may differ.
• Analogous structures: Similar function, different evolutionary origin.
• Embryology: Studying early, prenatal stages of organisms.
• DNA analysis: Similar DNA sequences indicate common ancestry.

Mechanisms of Evolution

• Mutations introduce new alleles.
• Changes in allele frequencies indicate evolution.
• Gene flow: Increased genetic diversity and changes in allele frequencies. Increased genetic diversity increases survival against natural selection.
• Non-random mating: Selection for phenotypes or inbreeding that increases homozygous genotypes and harmful recessive allele expression (doesn't directly affect allele frequencies). Inbreeding decreases heterozygous genotypes and increases homozygous individuals.
• Genetic drift: Change in allele frequencies due to chance events, reduces variation.
• Bottleneck effect: Rapid population decrease causing allele frequencies changes due to a loss in genetic diversity. (disease, starvation)
• Founder effect: Small group starts new population.
• Natural selection:
  • Stabilizing selection: Favors intermediate phenotypes, reduces variation.
  • Directional selection: Favors one extreme phenotype over another, usually when environment changes.
  • Disruptive selection (diversifying): Favors extreme phenotypes, eliminating intermediates.
  • Sexual selection: Natural selection for mating.

Speciation

• Defining a new species involves physiology, biochemistry, behavior, and genetics.
• Allopatric speciation: Geographic isolation (e.g., continental drift, islands, mountains) divides a species into separate groups.
• Sympatric speciation: Populations in the same habitat diverge genetically through reproductive isolation (e.g., chromosomal changes, non-random mating).
• Polyploidy in plants: Improper meiosis creates gametes with extra chromosomes leading to new species.
• Prezygotic mechanisms: Prevent fertilization and zygote formation.
• Postzygotic mechanisms: Prevent hybrid zygotes from becoming viable or fertile.
• Prezygotic barriers: Prevent mating or fertilization.
• Postzygotic barriers: After fertilization, preventing hybrid fertility.

Prezygotic Mechanisms

• Behavioral isolation: Different courtship and mating cues.
• Habitat isolation
• Temporal isolation: Different breeding times.
• Mechanical isolation: Reproductive organ differences prevent fertilization.
• Gametic isolation: Gametes from different species don't recognize/fertilize each other.

Postzygotic Mechanisms

• Hybrid inviability: Genetic incompatibility stops hybrid zygote development.
• Hybrid sterility: Hybrid offspring are healthy but infertile.
• Hybrid breakdown: F2 generation or backcross with parents are weak or infertile.

Explore the fascinating processes of evolution and mutation. This quiz covers key concepts such as divergent evolution, coevolution, adaptive radiation, and the role of mutations in adaptation. Test your knowledge on how species evolve and respond to environmental pressures.