Evolution and Darwin

Evolution and Darwin

Important Points

  • We do not come from monkeys: Humans and monkeys share a common ancestor.
  • Evolution and Religion: Evolution is a process accepted by the Catholic Church and other religions; it does not conflict with religious beliefs.
  • Evolution is a Scientific Theory: It's a well-supported explanation of nature with a vast body of evidence, not just a hunch.

What is Evolution?

  • Evolution is the progressive change in organisms over time.
  • It's the process transforming life from early forms to the diversity seen today and involves changes in genes.

Key Definitions

  • Evolution: Change in species over time; descent of modern species from ancient ones.
  • Adaptation: A trait that increases an organism's chance of survival in a specific environment.
  • Theory of Evolution (Darwin/Natural Selection): Explanation of how evolution occurs.
  • Species (Sp. or Spp.): A group of organisms with shared traits, common ancestry, and capable of interbreeding.

Old Theories of Evolution

Jean Baptiste Lamarck (Early 1800s)
  • Proposed the "inheritance of acquired characteristics."
  • Believed that using or not using body parts leads to the development of certain characteristics that are passed to offspring.
  • Lamarck was the first to suggest organisms change over time, with new organisms being modified descendants of older ones.
"The Inheritance of Acquired Characteristics"
  • Example: Giraffes acquired long necks by stretching to reach leaves, passing the lengthened neck to offspring.
Jean Lamarck (1744-1829)
  • French scientist.
  • Theory of use and disuse: Used organs become stronger; unused organs weaken and wither.
Lamarck's Hypothesis
  • Hypothesized that acquired traits are passed to offspring, which is proven false.
  • Organisms acquire traits from experience (not genes), and these are inherited by offspring.
  • Example: Giraffes stretching their necks, with offspring inheriting longer necks.
Implications of Lamarck's Theory
  • A nose job would result in children inheriting the new nose, which is incorrect.
  • Children inherit the original nose because DNA doesn't change with appearance alterations.
Logical Fallacy
  • DNA determines which traits are passed to children.
  • Changing appearance does not alter DNA; therefore, children won't inherit the new appearance.

Charles Darwin

  • Influenced by Charles Lyell's "Principles of Geology."
  • Darwin realized natural forces gradually change Earth's surface, and past forces operate today.

Charles Darwin (1809-1882)

  • Naturalist who studied and preserved biological specimens.
  • Embarked on a 5-year voyage around the world aboard the HMS Beagle.

Darwin's Voyage of Discovery

  • The HMS Beagle sailed off Patagonia.
The Voyage of the Beagle (1831-1836)
  • The voyage included stops in South America and the Galapagos Islands.
Observations
  • Darwin spent 5 years (1831-1836) surveying the south seas, primarily South America and the Galapagos Islands, collecting plants and animals.
  • He observed unique species on the Galapagos Islands.
  • These observations led him to write a book.

Darwin's Book: Origin of Species by Natural Selection

  • Published in 1859.
  • Described his theory of evolution.
  • Initially caused controversy with the church, which eventually accepted his theory. Darwin was buried in a famous church in England.
Charles Darwin's Main Points
  • Published "On the Origin of Species by Means of Natural Selection" in 1859.
  • Species evolved from ancestral species, not created in their present form.
  • Proposed natural selection as the mechanism for evolution.
Darwin's Observations
  • Organisms are well-adapted to their environments.
    Example: the Kori Bustard is perfectly adapted to its environment. Camouflage is present. Long, strong, legs.
Galapagos Islands
  • Darwin observed different species of tortoises, iguanas, and finches on each island, related to mainland forms.
Ideas Shaping Darwin's Thinking
  • Artificial Selection: Selective breeding of organisms based on desired traits, practiced since early human societies.

The ancestor of the domesticated dog is the wolf.

Variations in Organisms
  • Each species has organisms with varying characteristics (e.g., height, foot size, speed, vision, smell).
Struggle for Existence
  • There is a limited amount of resources.* Food, water, shelter.
Organisms with Favorable Adaptations
  • Organisms with favorable adaptations have more chances to survive and reproduce in a certain environment– SURVIVAL OF THE FITTEST
  • "Fitness" refers to the ability to survive, reproduce, and leave viable offspring.
  • Natural Selection: Environmental pressures determine survival and reproduction chances.
Descent with Modification
  • All species evolve from pre-existing species over time.
  • Modifications are adaptive characteristics passed down to offspring.
Darwin's Theories Today
  • Darwin's theories are accepted as the most accurate explanation for evolution.
    *Adaptive radiation illustrated in Galapagos finches.
Darwin’s First Theory

*States that newer forms appearing in the fossil record are modified descendants of older species.

Conclusion
  • Darwin observed many species and fossils.
  • Theory of evolution by natural selection: Nature selects organisms with variations that allow them to survive better (survival of the fittest).
  • He collected similar species and hypothesized that they shared a common ancestor.
Quote from Darwin
  • "I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection."

*Survival of the fittest by means of natural selection. *

Process
  • Variations may give certain organisms advantages to survive, while other organisms die.
  • Nature selects those organisms that will die or survive.
Giraffes
  • Darwin explained why giraffes have longer necks than their ancestors due to overproduction, competition for food, variation in neck length, and the survival and reproduction of longer-necked giraffes.
Natural Selection Theory
  • Individuals with favorable traits are more likely to leave more offspring better suited for their environment.
  • Also known as "Differential Reproduction."
  • Example: English peppered moth (Biston betularia) - light and dark phases.

Evidence of Evolution

  1. Biogeography: Geographical distribution of species.
  2. Fossil Record: Fossils and their order in sedimentary rock layers (strongest evidence).
  3. Taxonomy: Classification of life forms.
  4. Homologous Structures: Similar structures due to common ancestry (comparative anatomy).
  5. Comparative Embryology: Study of structures during embryonic development.
  6. Molecular Biology: DNA and proteins (amino acids).
Other Evidence
  • Structural Adaptations:
    • Mimicry
    • Camouflage
  • Fossils
  • Anatomy:
    • Homologous Structures: Similar structure/different function.
    • Analogous Structures: Different structure/similar function.
Comparative Morphology
  • Similar skeletal plans used for different appendages in whales, cats, bats, and gorillas.
Vestigial Structures
  • Embryos: Alligator, snake, chicken, opossum, and mouse embryos with limb buds and tailbuds.
Comparative Embryology
  • Embryos of different animals pass through similar developmental stages due to conserved molecular mechanisms.
Observed Evolution
  • Evolution of pesticide resistance in insects in response to selection.

Evolutionary Time Scales

  1. Macroevolution:
    • Long time scale events that create and eliminate species.
  2. Microevolution:
    • Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations.