SCIENCE OUTREACH
DEPARTMENT OF BIOLOGY
Critical Information Upon Which Evolution Depends
As we develop discussions for these, we will add appropriate links.
The Process Itself
Molecular Biology
Mutations happen. Environmental mutagens (including oxygen radicals) damage DNA at random; DNA repair is imperfect, so base changes occur. In general, mutation is a continuous source of genetic variation.
RNA-polymerase builds RNA molecules to match the sequences of genes. It doesn't know what it's building; whatever the sequence of the gene, polymerase builds the corresponding RNA.
Ribosomes and tRNAs build protein molecules according to the sequences of mRNA molecules. They don't know what they are building; whatever the mRNA sequence, they build the corresponding amino acid polymer.
The primary determinant of protein folding is the hydrophobic effect, in which hydrophobic amino acids are forced to the center, and hydrophilic amino acids cover the exterior of the protein "globule." Subsequent events fine-tune the structure and adopt the lowest-energy conformation. As with transcription and translation, these events know nothing. They simply occur, with the results dependent on the sequence of amino acids.
Regulation of Gene Expression
Some genes are expressed in all cells of a multicellular organism. Other genes are expressed only in specific locations. Many genes that determine the patterns of embryonic growth and development are expressed only in small numbers of cells. Mutations that change their patterns of expression can have dramatic effects on the morphology of the fully-developed organism.
Genetics
Transmission of Information From Generation to Generation
Most simply put, every species reproduces after its own kind. Offspring inherit DNA from their parents. Yes, there is meiotic shuffling of alleles, and there are dominant/recessive allelic relationships, but the essential fact is that DNA is inherited. Mutations are inherited (when they occur in gametes). Individual multicellular organisms cannnot change their genetics during their lifetime, so evolutionary change can occur only by descendent generations replacing ancestral generations.
How Genotype Informs Phenotype (see also morphology)
The specific alleles an individual organism inherits from its parents determine its heritable characteristics. It is important to have a sense of how this can occur, rather than merely memorizing the terms "genotype" and "phenotype." Two models that are accessible are pigmentation (such as fly eyes and hair color) and limb development (see below).
Developmental Biology
How Morphology is Controlled in Multicellular Organisms
Most developmental decisions occur in small groups of cells that are precursors to the larger structures of the mature individual. These decisions involve cell-cell interactions, diffusible molecules (what we might call "short-range hormones"), and changes in the patterns of gene expression.
Limb Development as an Example
We know many of the genes that are involved in limb development, and can therefore begin to visualize how modest changes in their expression can create significant changes in the morphology of the mature animal.
Ecology
Natural Selection favors some genetic variants, and selects against others. Students often see this as a vague statement. The statement loses some of its vagueness when we rephrase it in terms of ecological competition. Those who out-compete the others are the ones whose genes are passed on.
Competition occurs, of course, because resources are limited. At equilibrium, most ecosystems are at their carrying capacity for the species within them. For one species to prosper, or for some genetic variants within a species to prosper, they do so at the expense of others that are less fit.
There are many interesting species interactions that result from evolutionary cooperation. Pollination and the formation of edible fruits are good examples.
Supporting Evidence
Geological Time
Measurement Methods (a good discussion of relative dating, radiometric dating, etc.)
A Christian Perspective on Dating Methods (an excellent resource, especially in making the point that a great many paleogeolgists are Christians)
Paleobiology: Fossils and Time (a condensed, quite readable summary of the history of thinking on the age of the earth)
Plate Tectonics
USGS publication, This Dynamic Earth
An interesting discussion on the topic at Debating Christianity
The Fossil Record
What Fossils Are (a page at Enchanted Learning's site, dedicated to dinosaurs, with lots of addditional dinosaurian information)
What We Can Learn From Fossils Besides Just "What The Organism Looked Like"
Correlating Ages From Different Locations (and a lesson plan that gets at some of this)
Biostratigraphy--a major player in world-wide oil exploration
Reconstructing what life was like, based on the fossil evidence
Representations of the Data
Phylogenetic Trees
Data "bits" Used in Comparisons
Formats for Trees
Representation of the Data vs Explanation of How the Data Came to Be
last updated: Jan 16, 2009
