BILD 3: History of Evolutionary Thought

Describe the prevailing view regarding evolution and species in Europe in the 1800s.

• Each species was created individually by God (“special creation”) & has stayed the exact same throughout time (no evolution)

• The earth is older than 6000 years (most scholars accepted this idea)

Define the hypothesis of gradual and consistent geologic change, name its main proponent, describe its predictions about the age of the Earth, and discuss the evidence to support it that Darwin found on his voyage.

• Hypothesis: With slowly over time, forces (tectonic plates movement) can create gradual and consistent changes in the Earth’s geological landscape. (taken from Lyell really)

• Main Proponent: Charles Darwin (Lyell as another main)

• Predictions about age of Earth: at least 4.6 billion years old

• Darwin’s evidence: seashell fossils in Andes Mountains (12000 ft) + portions of coastal shelf (& as a result the coastline) raised 8 ft by a volcanic eruption and massive earthquake in Chile

Describe the biogeographical patterns Darwin observed on his voyage and explain how each of them provides support for the theory of evolution.

• Sloths + Armadillos: modern species resemble ancient (giant) species in the same region→showcases the principle of succession; species are similar across time in a region because modern species are descended with modification from local ancestors + species go extinct

• Seashell fossils in Andes Mountains (12000 ft) + rising coastline after earthquake (+ volcanic eruption): Earth is old + changes slowly→there has been enough time for many tree branchings (divergence) to create an enormous tree of life + all of modern biodiversity

• Galapagos tortoises: different environments correspond to different body shapes w/ each shape being well-matched to its environment→different selection pressures on each island produces different local adaptations via natural selection, resulting in new branches of the tree

Explain the principle of succession and why it constitutes evidence for descent with modification.

• Principle of Succession: Living organisms look similar to the fossils in their region because they are descended from those ancestors, with modification

• It is part of the evidence for descent with modification because it tells that as organisms evolve, species’ characteristics slowly changes from their ancestors

Describe the process of artificial selection, compare it to natural selection, and explain why it contributed to Darwin’s understanding of evolution.

• Artificial Selection Process: Humans chose which individual mate with which individual, selecting for certain traits (and creating many different species from a common ancestor)

• Contribution to Darwin: Darwin bred pigeons to understand how selection can create new body shapes, trying to understand how evolution happens

Give some examples of how organisms have established populations in new habitats via dispersal.

• Seeds floating on water + using the waves/current to take them to new land (they stay viable for a long time in saltwater)

• Tortoises floating on water (they don’t need to eat much bc slow metabolism)

Describe the process of adaptive radiation that led from one mainland species to many Galapagos finch species with different beaks. Explain how local adaptation can contribute to increased differences between populations.

• Adaptive Radiation: The diversification of species originating for a common ancestor to fill a wide variety of ecological niches

  • Some niches are more full and have more competition; by adapting to empty niches, populations/individuals can live and thrive more easily→this leads to a diverse amount of species

• Local adaption to different environments creates differences between populations

Describe the two main ideas in Darwin’s Origin of Species

• Process: descent with modification + divergence

• Mechanism: natural selection