Exam 1 Flashcards
Three types of Biodiversity
Ecosystem, species, and genetic diversity
Speciation
the process by which one spp splits into two or more
Biological species concept: species def
a group of populations whose members have the potential to interbreed in nature and produce fertile offspring.
Reproductive isolation
prevents members of different spp from mating with each other; prevents gene flow between spp: therefore the spp are distinct from each other
Conservation Biology
mission-oriented, crisis-driven, problem-solving field focused on the preservation of biological diversity
Extirpation
the loss of a single population of a species
Extinction
irreversible loss of all populations of a species
Hybrids
When some pairs of clearly distinct species occasionally interbreed and produce hybrids (ex: Grizzly and Polar Bear)
Morphological Species Concept
classifies organisms based on observable physical traits (applied to asexual organisms and fossils)
Homology
the similarity in characteristics that result from common ancestry
Homologous structures
have different functions but are structurally similar because of common ancestry
Vestigial structures
remnants of features that served important functions in an organism’s ancestors
Nonhomologous/analagous traits
Similarities resulting from convergent evolution (similar habitats, diets, etc)
Ecological Species Concept
defines a spp by its ecological role or niche and focuses on unique adaptations to those roles in a biological community (ex: 2 spp may look similar but differ in diet or habitat)
Phylogenetic Species Concept
(most modernly used) defines a spp as the smallest group of individuals that shares a common ancestor (done by testing DNA or morphology)
-difficulty in determining amt difference necessary to separate spp
3 Key Points about Evolution by natural selection
1) Individuals do not evolve: populations evolve
2) natural selection can amplify or diminish only heritable traits, not acquired ones
3) evolution is not goal directed and does not lead to perfection (favorable traits vary as envr changes)
3 Modes of natural selection
- directional (causes characteristics to take one extreme more)
- stabilizing (keeps characteristics more moderate-extremes die)
- disruptive (some factor causes all moderates to die, almost creating two spp of remaining extremes, but factor leaves and spp come back together)
Mutation definition
changes in the nucleotide sequence of DNA and the ultimate source of new alleles
Prezygotic Barriers
(physical barriers before zygote formation) Habitat (Garter snakes), temporal (E&W Spotted Skunks), behavioral (birds), mechanical (flies), and gametic isolation (corals&anemones)
Postzygotic Barriers
(genetic/embryonic barriers after zygote formation) Reduced hybrid viability, reduced hybrid fertility, hybrid breakdown
Allopatric Speciation
when landmasses separate organisms and prevent them from mating (ex: Antelope Squirrels)
Polyploidy
cells have more than two complete sets of chromosomes
Sympatric Speciation
can result from polyploidy by self-fertilization or by hybridization (80% of all living plant spp)
Adaptive radiation
the evolution of many diverse spp from a common ancestor (ex: the Galapagos Archipelago-finches)