Module 1
Evolution matters because it shows us our place in life and connects us to every living thing on earth and many more that have died. It gives us the true account of our origins.
The stages in the scientific method are to observe patterns, ask questions, form hypothesis, make predictions, and then gather evidence.
A hypothesis is a testable explanation that answers a question. It relates to a prediction because scientists use the hypothesis to predict what evidence they expect to find if the hypothesis is correct. Scientists make hypotheses and predictions about the past by asking what evidence should exist today if a past event really happened, and then examining that evidence to test their predictions.
Diversity of life: Evolution explains why there are so many different species. Populations change and diverge over time, creating new species.
Unity of life: Despite the diversity of organisms, living things share many characteristics because they descended from common ancestors.
Geographic distribution of life: Evolution explains why organisms are found in particular locations. Their locations often reflect where their ancestors lived, how they dispersed, and how populations became isolated and evolved.
Adaptive “design” of life: Organisms have traits that appear designed for particular functions. Evolution explains these adaptations through natural selection.
Intelligent design: Complex biological structures are explained as the result of a designer with foresight, planning, and a goal.
Blind Watchmaker: Evolution through natural selection can produce the appearance of design without actually planning ahead.
Nested hierarchy: Living organisms can be classified into smaller groups within larger groups. This pattern reflects evolution because species branch from common ancestors and become increasingly different over time.
Classification: The process of organizing living organisms into groups based on shared characteristics and relationships.
Why classify? Classification organizes biological diversity, makes organisms easier to identify and compare, and helps scientists understand evolutionary relationships.
Flat classification: Organisms are placed into separate categories without groups being contained within larger groups.
Nested/hierarchical classification: Organisms are placed into smaller groups within larger groups based on shared characteristics and evolutionary relationships.
Linnaean Classification: A nested system used to classify living organisms from the broadest group to the most specific.
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
Domain: Broadest level of classification; groups organisms based on fundamental cellular/genetic differences.
Kingdom: Large group within a domain based on broad biological similarities.
Phylum: Group within a kingdom based on major similarities in body organization/body plan.
Class: More specific group within a phylum.
Order: More specific group within a class containing more closely related organisms.
Family: Group within an order containing even more closely related organisms.
Genus: Group containing very closely related species. Plural = genera.
Species: Most specific level in the traditional Linnaean hierarchy; a distinct group/lineage of organisms.
As you move down the hierarchy, groups become smaller and more specific. Each smaller group is contained within the groups above it.
Taxon: A group of organisms at any level of classification. The plural is taxa. For example, a species is a taxon, and a genus is a higher-level taxon that can contain one or more species.
Genus = singular; Genera = plural
Criteria for grouping organisms into taxa: Scientists group organisms based on shared characteristics that reflect evolutionary relationships and common ancestry. Evidence can include similarities in anatomy, development, and DNA/genetics.
Multiple related taxa can be grouped into a higher-level taxon based on characteristics they share because of common ancestry.
Example: Related species can be grouped into a genus, and related genera can be grouped into a family.
Why life shows nested classification: Living organisms naturally form groups within larger groups.
Linnaeus's explanation: The nested organization of life reflected God's plan/order in nature.
Darwin's explanation: Descent with modification. Organisms descend from common ancestors and change over generations. As ancestral populations split into different lineages, they create a branching genealogical pattern, producing groups within groups.
A phylogenetic tree is a diagram representing a hypothesis about evolutionary relationships/common ancestry.
┌── A
┌───┤
│ └── B
──────┤
│
└────── C
The place where a lineage splits is called a node.
A
/
────────●
\
B
Determining relatedness: Organisms that share the most recent common ancestor are most closely related. Look at the branching points/nodes, not how close organisms appear on the page.
Evidence for common ancestry:
Comparative anatomy: Similar underlying body structures can indicate inheritance from a common ancestor.
Embryology: Similar developmental patterns can indicate shared ancestry.
Genetics: Similarities in DNA and genes provide evidence of inheritance from common ancestors.
Biogeography: Where organisms live can reflect where their ancestors lived, dispersal, isolation, and evolutionary history.