Lecture 2 - Darwinian Evolution

Darwinian Evolution

Evolution

The process of species accumulating changes overtime by adapting to their environment. Summarized as descent with modification by Darwin.

Scala Naturae

A scale of complexity for organisms devised by Aristotle, using the assumption that species are unchanging.

Binomial Nomenclature

A system of naming organisms with genus and species: Genus species, devised by Carolus Linnaeus. Humans are classified as Homo sapiens.

Linnaean System

System of classification in increasing specificity: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Immutable

Unchangeable. People used to think that the world was immutable. James Hutton and Charles Lyell, profound geologists, believed that the geology of Earth gradually changed overtime, but not life. Charles Darwin introduced the idea of descent with modification

Fossils

Preserved remains of organisms ranging from thousands to billions of years old.

Strata

The layers of sedimentary rock on the Earth’s surface formed over long periods of time. Fossils can be aged based on which stratum it is found in, with older being deeper.

Paleontology

The study of fossils

Use and Disuse

A proposed mechanism of evolution by Jean-Baptiste where body parts strengthen or deteriorate based on usage. This is not a mechanism of evolution according to evidence.

Inheritance of Aqcuired Traits

A proposed mechanism of evolution by Jean-Baptiste where modifications of an organism can be inherited by offspring. Traits do get inherited, but not acquired traits.

HMS Beagle

The boat Charles Darwin used for exploration. Through his voyages in South America, he observed fossils and organisms, eventually coming up with the theory of evolution

Natural Selection

A process where organisms that have favorable traits in their environment are more likely to reproduce and pass on traits.

Artificial Selection

A type of natural selection caused by humans. Genetic structure of populations shift due to human activity

Example of natural selection

Galapagos Finches. A single species inhabited many isolated islands off of the mainland of South America. Due to differing factors in their environments, the finches on each island developed a distinct morphology and became new species.

Example of Artificial Selection

Canines. Humans breed dogs to get specific traits like enhanced intelligence, smaller or bigger size, fur color, etc.

Wild Mustard. Wild Mustard domestication have led to kale (better leaves), brussels sprouts (better side buds), cabbage (better tip bud), broccoli (better flowers and stems), and kohlrabi (better stems).

Darwin’s observations

1- Members of a population vary in inherited traits

2- All species produce an unsustainable amount of offspring relative to their environment

Darwin’s inferences

1- Individuals with more heritable traits tend to survive and reproduce more

2- An unequal ability to survive combined with a limited environment leads to a population accumulating favorable traits over many generations.

Evidence for evolution

1. Direct observations of evolutionary change

2. Homologous anatomy

3. Biogeography

4. The fossil record

Direct Observation of Evolution

Documentation of organisms in thousands of scientific studies show adaptations like bacterial drug resistance.

Homologous Anatomy

Related species exhibit similar structures due to sharing a common ancestor. Humans, whales, bats, and cats all have limbs with 5 sections: pendactyl limbs.

Divergent Evolution

When related species accumulate differences in traits. Species branching from a common ancestor.

Vestigial Structures

Features or structures which serve no purpose currently, but exists due to being useful to the organism’s ancestors. Humans still have a tail bone and appendix. Snakes have hind leg bones.

Evolutionary Trees

Visual representations of hypotheses explaining the evolutionary pathways and relationships of species

Analogous Anatomy

Structures found in species which are similar, but not due to common ancestry, but rather through selective pressure.

Convergent Evolution

The tendency for species in independent, similar environments to have similar adaptations, seemingly showing evidence of common ancestry. Different branches start converging.

The Fossil record

The collection and analysis of fossils. It shows the history of lifeforms through long stretches of time. Going back in time tends to show a similarity of differing species and shows relations between very distinct modern species.

Biogeography

The study of where organisms live geographically. The distribution of species is influenced by geography. Continental landmasses split from Pangea, forming the continents, and a family of fish live in both South America and Australia.