mullerian mimicry vs batesian mimicry
Mullerian: 2 harmful species mimic each other
Batesian: a harmless species mimics a harmful one
fundamental niche vs realized niche
fundamental: what organism can accomplish under IDEAL conditions
realized niche: lifestyle and resources organism actually pursues
Intraspecific vs interspecific competition
Competition: need same resource
intraspecific: within the same species
interspecific: between different species
\+/- of each Competition: Predation: Herbivory: Parasitism: Mutualism:
Competition: -/- Predation: +/- Herbivory: +/- Parasitism: +/- Mutualism: +/+
adaptations by prey vs adaptations by predators
Predators: claws, fangs, venom, speed, camouflage and mimicry ex. thermoreception by rattlesnakes
Prey: flee, live in groups
a) mechanical defense: ex. porcupines
b) chemical defense: ex. skunks
c) aposematic coloration: warning coloration-ex.-frogs store poison in skin
d) cryptic coloration: camouflage; colors or markings that blend into physical surroundings
species abundance vs species richness
species richness: # of DIFFERENT spp that live w/in a community
species abundance: spp evenness/refers to proportion of each sp
relationship between diversity and community stability
the higher the diversity in a community: the more productive, make more biomass, better able to withstand environmental stress, more resistant to invasive species
energetic hypothesis
only 10%of nrg stored in organic matter of each level transferred to the next level
- food chain length limited by inefficient nrg transfer
- predicts food chains should be larger in habitats of higher photosynthesis production
Phenotypic variation vs genetic variation
Phenotypic variation: observable differences between individuals
- sometimes an either/or situation: you have or you don’t
- sometimes traits on continuum: human height, skin color- influenced by more than one gene
Genetic variation: differences among individuals in gene or nucleotide sequence
Sources of genetic variation:
- point mutation: new allele
- large scale changes in chromosome structure
- rapid reproduction: very short generation time in prokaryotes- more mutations per unit time– more variation
- sexual recombination: source of most genetic variation among organisms that sexually reproduce; unique combination of alleles from parents
conditions required for HW equilibrium
- no mutation
- random mating
- no natural selection
- very large population (no genetic drift)
- no gene flow between populations
SEQ major mechanisms of evolution
mutation–>non-random mating–> natural selection–>genetic drift–>gene flow
Mutation as a major mechanism
- Any heritable change in DNA
- random and permanent
- One allele → different allele - immediate change to gene pool
- Not always Passed on
a) Somatic cells - not passed to offspring
b) Very harmful - cleared by natural selection
c) Could be neutral - no change to protein structure or function - Importance of Mutations
a) Very little effect on allele frequencies
b) Especially in large populations
c) But: Source of genetic variation
d) → raw material for natural selection - variation
Nonrandom mating as a major mechanism of evolution
- Random mating: each individual in population equally like to mate with any individual of opposite sex
a) Random mixing of gametes - Nonrandom mating: no random mixing of gametes
- Example: Inbreeding
a) Mating of closely related individuals - genetically similar
b) Common when mating based on proximity, especially if low
mobility
c) Can change allele frequencies and genotype frequencies - more homozygotes
Natural selection as a major mechanism of evolution
- Important evolutionary mechanism
- HW assumes all individuals have an equal ability to mate and produce
viable offspring - Almost never true - variation exists, resources limited
- → nonrandom changes in allele frequency
- Selection decreases genetic diversity
- Selection acts on Phenotype
a) Morphs: contrasting phenotypes (e.g. red and white flower)
b) Polymorphic: population with 2 or more morphs at detectable frequencies- Populations must be polymorphic for natural selection to operate
- Modes of Selection
- 3 types of selection can change phenotype distribution: stabilizing selection, directional selection, disruptive selection
- Modes of Selection (fig. 23.13)
Stabilizing selection vs. Directional selection vs. Disruptive selection
(1) Stabilizing selection
(a) Selects intermediate phenotypes
(b) Common in stable environments
- Example: Human birth weight
(2) Directional Selection
(a) Selection for one phenotypic extreme
(b) Shifts phenotype distribution towards that extreme
- Examples: Antibiotic resistance; Break size in finches
(3) Disruptive Selection
(a) Selection for both phenotypic extremes over
intermediate state, occurs when the environment is
highly variable
- Example: Flu vaccine
Genetic drift as a major mechanism
- Random changes in allele frequency - chance events
- Decreases genetic diversity with population
- Examples:
a) 10 plants, 5 red, 5 white, cow randomly eats 3
b) Large change in allele frequency - Drift is stronger in smaller populations
- Special cases of genetic drift
a) bottleneck effect
b) founder effect
bottleneck effect vs. founder effect
bottleneck effect: size of pop. drastically reduced
- surviving pop. has different allele freq. from ancestral pop.
founder effect: small number of individuals colonize a new habitat
- gene pool of new population different from parent population due to small sample size
Biological species concept
- Group of populations whose members have the potential to interbreed in nature and produce viable offspring
- Share common gene pool
- Gene flow between populations of same species
- No gene flow with different species - reproductive isolation
Limitations of biological species concept
- Extinct/fossil species
- Asexual species
- Viruses/microbes
- But generally useful for extant sexual species
morphological species context vs. ecological species concept
morphological species concept:
a) species distinguished by shape/structure
b) applies equally well to sexual, asexual, extinct species
c) disagreement over which features are most important
ecological species concept:
a) species define by ecological niche- how individuals interact with living and nonliving parts of the environment
b) works for sexual and asexual organisms, but must be extant
prezygotic isolation mechanisms
- Habitat Isolation
a) Overlapping geographic range, but live/breed in different areas
(1) Rarely interact, no opportunities to mate - Temporal Isolation
a) Overlap, but breed at different times - different times of the year, season, day- Example: Dendrobium, genus of orchids - flower on different days, only open for 1 day
- Behavioral Isolation
a) Species-unique behaviors enable mate recognition - Mechanical Isolation
a) Mating attempted but sexual structures incompatible - Gametic Isolation
a) Molecular or chemical differences between species - egg and sperm incompatible
b) Common in aquatic organisms - release gametes into water
c) But sometimes fertilization occurs between 2 species
allopatric speciation vs sympatric speciation
Allopatric: Geographic isolation → drift or selection → divergence
- Mechanisms of Separation
a) Geographic barriers- Mountain range, river, land, bridge, falling water level
- Migration
a) Small offshoot population → isolation from parent population- Example: Crickets in Hawaiian Islands
- Chance Events
a) Random events can isolate sub-populations- Example: Storm separates small population - may explain island populations
- Experimental Allopatric Speciation
a) Flies divided into 2 populations → different diets
b) 40 generations, reintroduced
Sympatric: Reproduction isolation without geographic isolation
- Sympatric Speciation Mechanisms
a) Polyploidy: Having >2 sets of chromosomes → Reproductive isolation
b) Within single species
c) Or in hybrids - Sexual Selection
a) Selection for different traits in males and females
b) Can become a barrier to reproduction between subpopulations - Habitat Differentiation
a) Subpopulation uses habitat or resources not used by the rest of population
b) Can lead to habitat isolation
c) Example: North American apple maggot fly
d) Habitat isolation → temporal isolation → postzygotic barriers - Sympatric Speciation Can be Rapid
a) Example: Japanese snails
b) Single gene causes shell to spiral in different directions
c) Genitalia no longer oriented correctly → mechanical barrier
SEQ Linnaean classification system
each taxonomic level is MORE INCLUSIVE than the one “below” it
- upside down triangle
DKPCOFGS
interpret a phylogeny (components)
- branch points/nodes: divergence of 2 evo lineages from a CA
- sister taxa: group of organisms that share immediate CA; closest relatives
- root: branch that represents most recent CA of all taxa on tree
- basal taxon: lineage that diverges early on in groups history; 1st to diverge from CA
- polytomy: branch with >2 descendant groups
