lecture 3 - species and speciation Flashcards
(17 cards)
Distinguish between population variation and ontogenetic variation.
Population: Differences between individuals in a breeding group (e.g., shell shape in scallops).
Ontogenetic: Changes within an individual’s lifespan (e.g., skull growth in Triceratops).
Define “gene pool” and “deme.”
Gene pool: All genes in a population.
Deme: Local interbreeding population (e.g., grass adapting to mine tailings).
How does natural selection act on variation?
Favors traits enhancing survival/reproduction, altering allele frequencies (e.g., metal-resistant grass).
What is intersexual selection?
Females choose mates with conspicuous traits (e.g., bright plumage, elaborate horns).
What is the morphological species concept’s limitation?
Relies on appearance alone (e.g., similar meadowlarks are distinct species due to behavioral isolation).
Define the biological species concept.
Groups of interbreeding populations reproductively isolated from others (e.g., lions/tigers produce infertile ligers).
Describe allopatric speciation with an example.
Geographic isolation → genetic divergence (e.g., antelope squirrels separated by the Colorado River).
How can sympatric speciation occur?
Without geographic isolation, via sexual selection or ecological niches (e.g., cichlid fish in lakes).
What is the founder effect?
Small founding population leads to genetic drift (e.g., Hawaiian honeycreepers’ rapid diversification).
What does Bergmann’s rule state?
Larger body sizes in colder climates (reduced surface area/volume ratio conserves heat).
Explain Allen’s rule with an example.
Shorter appendages in colder climates (e.g., Inuit body proportions vs. tropical populations).
What are ring species?
Populations diverging around a barrier, with terminal forms unable to interbreed (e.g., herring gulls).
Define anagenesis.
Gradual transformation of a species over time (e.g., Athleta petrosa mollusk lineage).
Contrast punctuated equilibrium with gradualism.
Punctuated equilibrium: Long stasis punctuated by rapid speciation (e.g., abrupt appearance of new fossil forms).
Gradualism: Slow, continuous change (Darwin’s view).
List three mechanisms of reproductive isolation.
Behavioral: Different mating rituals.
Ecological: Occupying different habitats.
Hybrid Inviability: Offspring fail to thrive.
How to remember allopatric vs. sympatric?
“Allo” = “away” (geographic separation); “Sym” = “same” (no separation).
Why are fossil species based on morphology?
Cannot observe interbreeding; time dimension shows evolutionary trends (e.g., punctuated equilibrium).
