Evolution Retake

EVOLUTION: BIOLOGY'S UNIFYING CONCEPT

INTRO TO EVOLUTION

  • Evolution: The process of biological change in populations over time that makes descendants genetically different from their ancestors.

TWO TYPES OF EVOLUTION

  • Microevolution: Evolution occurring on a small scale affecting a single population.

  • Macroevolution: Evolution occurring on a large scale affecting changes in species across populations.

EVOLUTION TODAY

  • Bacteria Evolution: Have evolved to outsmart our antibiotics.

  • Lactose Tolerance in Humans: Ability for adult humans to consume lactose.

  • Owls' Color Change: Owls changing colors to survive a changing climate.

HISTORY OF THE THEORY

Hutton & Lyell

  • They contributed to the concept that Earth is millions of years old.

James Hutton (1785) - Theory of Gradualism

  • Proposed that Earth was shaped by geological forces occurring over long periods of time (millions of years).

Charles Lyell (1833) - Theory of Uniformitarianism

  • Suggested that geological processes of today are the same as those of the past.

Malthus' Contribution

  • Thomas Malthus (1798):

    • Hypothesized that, eventually, resources would run out in a growing population, causing competition.

    • This idea helped Darwin realize not all individuals in a population can survive due to limited resources.

Lamarck's Contribution

  • Jean-Baptiste Lamarck (1809):

    • Proposed that environmental change leads to use or disuse of structures.

    • Inheritance of Acquired Characteristics: Individuals can pass on traits acquired during their lifetime to descendants.

Alfred Russel Wallace (1858)

  • Independently proposed the idea of evolution by natural selection, which motivated Darwin to publish his work.

Charles Darwin

  • Published: "On the Origin of Species" (1859)

  • Presented evidence and proposed a mechanism for evolution known as natural selection.

DARWIN'S THEORY: EVOLUTION BY NATURAL SELECTION

DARWIN’S VOYAGE

  • Collected considerable data, observations, and evidence along the coastline of South America during his voyage on the H.M.S. Beagle which set sail in 1831.

  • Notable observations included the Finches of the Galápagos Islands.

DARWIN FOUND 3 PATTERNS OF BIODIVERSITY

  1. Species vary globally.

  2. Species vary locally.

  3. Species vary over time.

DARWIN’S CASE OF NATURAL SELECTION

THE STRUGGLE FOR EXISTENCE

  • Influenced by Malthus’ ideas about competition for resources.

  • Conclusion: When more individuals are produced than can survive, members of a population must compete for food, space, and other necessities.

VARIATION AND ADAPTATION

  • Observed variation among island species adapting to their environment.

  • Examples:

    • Galápagos tortoises living in areas with tall plants have long necks and legs.

    • Galápagos finches in areas with hard-shelled nuts have strong beaks.

SURVIVAL OF THE FITTEST

  • Fitness: Refers to how well an organism can survive and reproduce in its environment.

  • Survival of the fittest: Refers to the differing rates of survival and reproduction.

NATURAL SELECTION

  • Natural Selection: The process by which organisms with variations most suited to their environment survive and leave more offspring.

  • Environments influence fitness.

  • Over time, natural selection results in changes in the inherited characteristics of a population.

DESCENT WITH MODIFICATION

  • Suggests each species has descended, with changes, from other species over time.

  • Implies all species, living and extinct, are descended from ancient common ancestors.

EVIDENCE FOR EVOLUTION

BIOGEOGRAPHY

  • Study of where an organism lives now and where their ancestors lived can show evolutionary relationships.

Example: Camel Family

  • North America: Llama

  • Africa: Dromedary camel

  • Asia: Bactrian camel

  • Europe: Original ancestors of the camel family.

  • Australia: Connections through historical migrations.

AGE OF EARTH & FOSSIL EVIDENCE

  • Recent fossil discoveries trace the evolution of modern species from extinct ancestors.

ANATOMICAL EVIDENCE

ANALOGOUS STRUCTURES

  • Structures that serve a common function but do not share a common structure, indicating similar environmental pressures rather than a common ancestor.

HOMOLOGOUS STRUCTURES

  • Structures with similar structure but different functions, indicating relatedness but different evolutionary pressures.

  • Example structures include:

    • Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges across different species (Human, Cat, Horse, Bat, Dolphin).

VESTIGIAL STRUCTURES

  • Structures that serve no apparent purpose in the current form of the organism.

  • Examples on Humans:

    • Plica semilunaris (eye), wisdom teeth, appendix, body hair, goosebumps, ear muscles, tonsils, male nipples, and coccyx.

EMBRYOLOGICAL DEVELOPMENT

  • Similar embryonic stages across various species (fish, salamander, tortoise, chicken, human) show gill slits and tail structures before differentiating.

MOLECULAR CLUES

  • Similarities in DNA sequences and amino acid sequences across species indicate shared ancestry.

  • Example DNA sequences:

    • Species I: ACA GCA CCG

    • Species II: ACT GCT GGA

    • Species III: ACA GCA GGG

    • Species IV: ACT GCA CCG

MECHANISMS OF EVOLUTION

CHANGING POPULATIONS

  • Gene Pool: All alleles of all genes in a population, indicating genetic diversity.

  • Genetic Equilibrium: A state where the gene pool does not change; populations not at genetic equilibrium may be evolving.

GENETIC DRIFT

  • Changes in gene frequency within a very small population due to chance events.

Examples of Genetic Drift:

  1. Bottleneck Effect: Change in frequency after a traumatic event, such as disease.

  2. Founder Effect: A small population leaves the original group, leading to changes in gene frequency.

DISRUPTING GENETIC EQUILIBRIUM

Factors include:

  • Immigration or emigration

  • Small population size

  • Natural selection

  • Nonrandom mating (sexual selection)

  • Mutations

  • Isolation

IMMIGRATION OR EMIGRATION (GENE FLOW)

  • Immigration: Individuals who join a population introduce new alleles to the gene pool.

  • Emigration: Individuals who move out of a population can reduce genetic diversity.

NATURAL SELECTION (NS)

  • Organisms better adapted to their environment tend to survive and reproduce more offspring.

Requirements for Natural Selection:

  • Reproduction

  • Variations among organisms

  • Differing fitness levels

  • Heredity (like produces like)

  • Limited resources

TYPES OF NATURAL SELECTION

Directional Selection

  • Favors extreme phenotypes over others.

  • Example: Light-colored peppered moths versus dark-colored peppered moths; coloration shifted due to environmental changes during the Industrial Revolution.

Stabilizing Selection

  • Eliminates extreme phenotypes and reduces variety.

  • Example: Robins typically lay four eggs; smaller clutches may not result in viable offspring, and larger clutches may lead to malnourished chicks.

Disruptive Selection

  • Favors extreme phenotypes and selects against average traits.

ARTIFICIAL SELECTION / SELECTIVE BREEDING

  • The intentional choice of traits in organisms for reproduction to obtain desirable characteristics.

  • Examples of selective breeding in plants:

    • Broccoli - suppression of flower development

    • Cabbage - suppression of internode length

    • Kale - enlargement of leaves

    • Cauliflower - sterility

    • Kohlrabi - enhancement of flowers

    • Wild mustard as the original plant.

ISOLATION

Types of Isolation:

  1. Temporal Isolation: Species reproduce at different times.

  2. Behavioral Isolation: Differing behaviors or courtship rituals prevent recognition as potential mates.

  3. Geographic Isolation: Physical barriers separate populations.

  4. Genetic Isolation: Lack of interbreeding prevents successful reproduction.

  5. Mechanical Isolation: Physical incompatibility prevents fertilization.

MUTATION

  • Mutations can be harmful or beneficial, altering genetic sequences.

Types of Mutations:

  • Missense Mutation: Changes in one amino acid.

  • Silent Mutation: No change in amino acid.

  • Nonsense Mutation: Premature stop codon.

  • Frameshift Mutation: Changes reading frame leading to extensive changes in protein.

PATTERNS IN EVOLUTION

Patterns of Evolution Include:

  • Punctuated Equilibrium: Evolution marked by rapid speciation episodes followed by long periods of stability.

  • Convergent Evolution: Unrelated species evolve similar traits due to analogous environmental pressures.

    • Example: Both bats and whales using echolocation for navigation.

  • Divergent Evolution: Closely related species evolve different traits.

    • Example: Dogs descending from wolves; Zebras, Donkeys, and Horses share common ancestry.

  • Coevolution: Two or more species evolving in response to each other.

  • Adaptive Radiation: Single species evolves into multiple forms to occupy different niches.

  • Mass Extinctions: Sudden events that eliminate many species on a global scale.

PHYLOGENY

Phylogenetic Analysis

Cladograms and Phylogenetic Trees

  • Diagrams that illustrate evolutionary relationships among organisms, showing both common ancestors and present-day species.

Derived Characteristics in Species Relationships

  • Analyzing common traits can help establish relatedness among various species (e.g., reptiles, birds, amphibians).

Common Characteristics of Mice and Lizards

  • Shared traits across various species include (e.g., jaws, lungs, claws or nails, fur, mammary glands, feathers).