Descent with modification

Exam Information

Exam grades will be available online by Thursday.
The averages will be provided then, even if all papers aren't returned.
The delay is due to the holiday weekend and preparing student posters for expos.

Expo

Expo is an on-campus conference for undergraduate and graduate student research.
It includes hosted sessions and talks.
To find more information, search "expo spring 2025 Lamar University" on Google.
It's a good opportunity to see research being done by faculty members with undergraduates, regardless of major.

Extra Credit

The last homework was an extra credit opportunity.
Additional optional homework assignments will be available covering biodiversity.
These will cover: bacteria, archaea, protists, fungi, plants, and animals.
You can complete up to three assignments.
Each completed assignment adds five points to your grade, for a total of 15 points.
It is recommended, especially the plant assignment if taking Gen Bio two in the fall.
These assignments won't be on the final exam.

Final Exam

The final exam is NOT comprehensive.
It covers material from five lectures, starting from today (Thursday).
The exam is on Tuesday, the thirteenth, with ample time to take it.

Shift to Evolution

The course is shifting from intra-organismal biology to evolution.
This portion is often part of Gen Bio two at other universities.
Evolution connects to Mendelian inheritance.

Superior Traits

The concept ties back to the bonus question on the last exam about superior traits (e.g., short vs. tall, round vs. wrinkled).
Without additional information, it's impossible to determine which trait is superior.
Example: large corn kernels vs. small corn kernels.
Large kernels may be seen as superior due to farmers wanting larger kernels to sell.
However, predators might target larger kernels, making smaller kernels superior in that context.
The superiority depends on the situation and environment.

Evolution Topics

The course will cover the history of understanding evolution, natural selection, and other mechanisms of evolution.
The focus today is on Darwin's original view of natural selection.

Intra-organismal Biology Review

The semester has covered topics from atoms to macromolecules, cells, and cell division.
Genetic material (DNA) and its variations (alleles) lead to diversity among organisms.
Different alleles result in different phenotypes (physical traits).
These traits can be acted upon by the external environment.

Evolution and Populations

Evolution occurs at the population level (at minimum).
The focus shifts to above the organismal level.

Biodiversity

Evolution explains the origin of biodiversity.
Humans categorize organisms (e.g., grouping cats, plants).
Evolution helps explain and categorize this diversity.

Evolution: Pattern vs. Process

Evolution can be viewed as a pattern or a process.

Pattern

Evolution as a pattern refers to observable patterns in nature.
Example: white fur in Arctic climates across different species (polar bears, foxes, rabbits, weasels, etc.).
Another example: armored vs. unarmored forms of three-spine sticklebacks based on predator presence.

Process

Evolution as a process explains the mechanisms that produce these patterns. This is the more common usage of the term.

History of Evolutionary Thought

Aristotle

Aristotle was the first to try to categorize life's diversity.
He grouped fishes, lizards, and birds, placing humans as the most complex.
He believed all life forms were perfect, permanent, and created to fit their environment.
Species were considered immutable (unchanging).
He developed the Scala Naturae (scale of nature), a ladder of increasing complexity with humans at the top.
He observed that cartilaginous fishes, sharks and skates and rays are viviparous, meaning that they have internal fertilization, and the females typically give birth.

Carl Linnaeus

Linnaeus introduced a hierarchical system of classification to manage increasing species discoveries.
He established binomial nomenclature (two-name system) for species: genus and species name.
For example, $Homo sapiens$ for humans.
He used a hierarchical categorization system moving away from linear scala natura.
Species name is sapiens. Homo is the genus.
The hierarchical categorization system goes from species to genus to family to order to class, and so on.
Despite this, species were still thought to be immutable.

Jean-Baptiste Lamarck

Lamarck, in 1809, proposed a mechanism for evolution, suggesting species change over time (Lamarckism).
He observed similarities and variations in the fossil record.
He proposed that traits acquired during an organism's lifetime could be passed to offspring.
His proposed process of inheritance of acquired characteristics is now refuted.
Classic example: Giraffes stretching their necks to reach higher leaves, resulting in offspring with longer necks.

Charles Darwin

Darwin is considered the father of modern evolutionary theory.
He initially studied medicine and then became interested in naturalism.

HMS Beagle Voyage (1831-1836)

Darwin served as a naturalist on the HMS Beagle for a five-year voyage.
The route included surveying the southern border of South America.
He experienced diverse environments, including temperate regions and tropical rainforests, with local fauna unlike the species from Europe in similar climate.
He noted that temperate species in South America resembled tropical species more than European temperate species.
In the Galapagos Islands, Darwin observed varying species on different islands.

Influences on Darwin

Geology: James Hutton and Charles Lyell suggested gradual geological changes over millions of years, implying Earth was much older.
Thomas Malthus: Proposed human population growth would outstrip resources, inspiring Darwin's ideas on survival and reproduction.

Natural Selection

Darwin concluded that species could change over time through natural selection.
Definition: Individuals with certain inherited traits survive and reproduce at higher rates due to those traits.
Beneficial traits are called adaptations.

Adaptation Examples

Finches' beaks adapted to different food sources.
Plants' thorns for protection or leaf shape for photosynthesis.
Catfishes' pectoral fin spines for protection.
Adaptation = Survival + Reproduction + Genes being passed On

Darwin's Four Postulates

Observation 1: Members of a population vary in their inherited traits.
Observation 2: All individuals can produce more offspring than the environment can support; many offspring fail to survive and reproduce.
Inference 1: Individuals with traits that increase survival and reproduction in a given environment leave more offspring than other individuals.
Inference 2: This unequal ability to survive and reproduce leads to the accumulation of favorable traits in the population over generations.

Stickleback Example

Sticklebacks can be either armored or not: An enclosed body of water has both.
Add in Yellow Perch.
Armored is more beneficial since it is protection

Key Points About Natural Selection

Natural selection acts on individuals, but populations evolve.
It only applies to inherited traits with variation within a population.
The traits which are favorable depend on the environment

Darwin's Publication

Darwin's book, "On the Origin of Species," published in 1859, introduced natural selection.
He delayed publishing due to fear of ridicule.

Alfred Russel Wallace

Alfred Russel Wallace independently conceived the idea of natural selection.
Wallace sent his manuscript to Darwin in 1858, prompting Darwin to publish his own work.
Darwin published first and Lyle then promoted Darwin and Wallace at the same time.

Modern Theory of Evolution

The simplest definition: Evolution is any change in the genetic composition (gene pool) of a population over time.
Mutations are the source of genetic variation.
Sufficient variation can allow diverse life to appear.

Darwin's Shortcomings

Darwin was much more aware of his shortcomings than other evolutionary scientists.
He talked about everything he couldn't explain.
Sexual selection is really the explanation for this.

Testing the Hypothesis

Sexual selection can be tested by other evolutionary scientists.
Even if one is incorrect, continue to test.

Evidence Supporting Evolution

There's much evidence to support the idea of evolution.

Artificial Selection

Artificial selection shows traits can be selectively bred such as with dogs.
Humans breed organisms so that the proper evolutionary paths take place.

Examples From Nature

Stigglebacks: Marine species that differ over all of the lakes. (Armor vs Lack of Armor).
Homologous Features: Shared among organisms, different organisms, derived from a common ancestor.

Homologous Traits

Homologous Traits have common ancestry, but their shape changes according to function (divergent evolution).
Looking at organisms with homologous traits = information on evolutionary relationships.
Shared Traits = the closer related species is.

Tunicates

Vertebrates and Tunicates are closely related.
The Adult Tunicates and Vertebrates are very genetically different.

Early stages of Development

If we look at Early stages of Development we can see that there are a lot of characteristics that stay.
We see the notocord and the post anal tails since they can be lost early on.

Vestigial Structures

Pelvic girdle of a whale is an example of evolution.

The Appendix

The appendix in humans is thought of to be useless, but aids the immune system.
If we get sick and wipe out the bacteria for ourselves the bacteria is replenished by the appendix.

Spurs in Boas

They still use Spurs for reproductive activities.
Structures remain during evolution, but can be lost over time.

Analogous Traits

We should not be confusing structures with homologous traits.
Analogous Traits: These are traits that have a similar function, do the same thing, they look very similar to each other, but do not necessarily share an ancestor.

Examples of Analogous Traits

The wings of the bird and the bat.
New/Old World Eye Fishes
They both evolved independently.