Exam 3 Flashcards
community structure
includes attributes like
1) # of species
2) species diversity
3) relative species abundance
guild
group of organisms that all make their living in the same way
ex: all seed-eating animals in an area
what is species richness and the problem with it?
.# of species in a community
problem: # of species depends on sample size
rarefraction???
can correct the over/undersampling of species richness
diversity
-measured with richness (# of species)
-evenness- how equal are the species in terms of abundance?
-Simpson’s index
Simpson’s Index
probability that any 2 individuals randomly chosen from community come from same species
Simpson’s Index of Diversity
probability that any 2 individuals chosen randomly from community come from different species
Simpson’s Reciprocal Index
number of equally common spcies you would need to measure the mix
food chains
simple interactions
food webs and the 2 types of interactions
summarize feeding relations in a community
-all food chains in an ecosystem
-help identify strong interactions
directly: predation, herbivory, parasitism
after food item is dead: detritivore
non-food web interactions
habitat formation, competition, amensalism, commensalism
indirect interactions
one species affects another through a third intermediate species
1) indirect commensalism
2) apparent competition
keytone species
-have disproportionate effect on their environment relative to abundance
-ecosystem may experience a dramatic shift if a keytone species is removed (even if small biomass or productivity)
green world hypothesis
predators play a role in maintaining plants in an ecosystem by limiting number of herbivores in that system
5 keystone interactions
1) competition
2)predation or herbivory
3) may be prey or predators
4) structure
5) may be dominant species but not always
where does species diversity tend to be higher?
-in complex environments
-intermediate levels of disturbance (high diversity) —–> allows some species to colonize but not enough time for competitive exclusion
equilibrium model of island biography
the theory of island biography by MacArthur and Wilson
-# of species on islands is determined by balance b/w species immigraiton and extinction
-rate of immigration of new species decreases as # of species increases
-rate of species extinction increases as # of species increases
when is immigration highest according to Equilirbium Model of Island Biogeography
new island with no organisms
why does extinction rate increase due to competition?
-population of each species decreases, creating larger pool of species for potential extinction
what is extinction on islands determined by?
size (allocation of space)
what is immigration on islands determined by?
isolation from source of immigrants
what are the 2 predictions of Model of Island Geography?
1) more species on large islands and near islands
2) species on islands is dynamic (always changing) but # remains the same
species turnover
the change as a result of immigration and extinction
4 updates from recent studies in regards to the Model of Island Geography?
1) species richness is not always at equilibrium
2) island size may affect immigration
3) island distance from source colonizers may affect extinction
4) area and isolation only 2 environmental factors. Other factors may affect richness
5 possible reasons why species richness increases in the tropics
1) time since perturbation (evolutionary hypothesis)
2) productivity
3) environmental heterogeneity (intermediate disturbance)
4) favorable (ambient) energy
5) interspecific interactions
geographical area hypothesis
strong positive relationship between area and species diversity
why is extinction rate lower in N.A and Asia during glaciation?
because had more diversity —-> more species available
natural selection
-differential reproductive success
-a trait that increases ability of individual to survive and reproduce compared to others that differ in that trait
-a trait that has risen via selection
evolution
-change in allele frequency in a population over time
-descent with modification
aristotle
-“ladder of nature”
-Scala naturae
-suggested that each entity had its perfect representation and had a perfect purpose in the order of life
Linnaeus
-father of taxonomy –> hierarchy of life
-binomial naming –> Genus species
-created ordered nested class classification system (based on common traits of reproduction)
James Hutton
-geologist, proposed idea of gradualism
-world runs through cycles of decay and repair
-major geological changes could be explained by accumulation of small processes caused by continuous processes (think rock cycle)
Charles Lyell
-father of modern geology
-used uniformitarianism to expand Hutton’s ideas
-same geological processes in past as today
-same rate as today (renewals, cycles)
Jean Baptiste de Lamarck
-linked evolution to adaptation
-extinct species have been replaced by descendants with new features
-said features (adaptations) helped them survive in their environment
-“inheritance of acquired characteristics”
-similar to “use/disuse” or “use or lose”
-Darwin rejected these ideas (good_
August Weismann
disproved Lamarck’s ideas by cutting tails of mice off
Charles Darwin + Alfred Wallace
evolutionary history and mechanism of natural selection (old)
Summary of 3 observations from Darwin
1) All species produce more offspring than needed to replace them
2) most populations remain fairly stable in size (once they get to K)
3) environmental resources for life are limited
Inferences of Darwin’s observations
1) differential reproductive success (those w “best” traits survive and reproduce more)
2) those heritable, favorable traits (adaptations) accumulate over time, matching the species to its environment —> new species
what has to be true for evolution via natural selection
1) phenotypic variation - individuals within populations are a variable
2) variation is in part heritable
3) competition - some individuals are more successful at surviving and reproducing
4) fitness is not random (linked to the phenotypic traits that vary among individuals)
what does H^2 measure?
heritability- the proportion of total phenotypic variation due to gene variation
H^2= 0. no genetic differences. all env
H^2= 1 all differences are genetic. no env
natural selection acts on _________ but evolution consists of changes in _________
phenotypes
allele frequencies
evolution is always a generation _____ any changes in the environment
behind
exaptations
traits that originally evolved for one function may continue to evolve and acquire new function
is genetic material static?
no
natural selection is ____ but ______
nonrandom but not progressive
no “advanced forms” just “better” at adapting
why does natural selection act on individuals?
for good of population
altruism
2 things missing from darwin’s theory
didnt know how variation was
1) generated in populations (mutations)
2) passed on to offspring (Mendel genetics)
evidence of change through time in lineages
microevolution- changes in allele frequencies (thus distributions) within populations. can be seen within our lifetime
macroevolutions- large evolutionary change (typically differences among populations that would warrant species status)
what reveals common ancestry?
homologous structures
vestigial structures
-a rudimentary version of a body part that DOESNT WORK the way it once did
-fossil record and transitional forms (shows gradual change)
ex: archaeopteryx b/w dinosaurs and birds
homologous structures
-structures adapted to different purposes b/c of descent w modification from common ancestor
-DNA, RNA or protein sequences can be homologous
-anatomically similar. functionally different
what can sequence homology result from?
1) horizontal gene transfer –> “xenologs”
2) speciation event –> “orthologs” –> look for common descent (compare 2 different species)
3) duplicating event –> “paralogs” –> same organism. multiple copies of same gene (not good for assessing evolutionary differences between species. how 1 species changes over time)
analogous structures
-“homoplasty”
-obtained by need
-anatomically different
Divergent evolution
-homologus structures
-structures derived from common ancestor
-used to build phylogenetic trees
Divergent evolution
-homologous structures
-structures derived from common ancestor
-used to build phylogenetic trees
convergent evolution
-analogous structures
-functionally similar. anatomically different
-distinct phenotypes converged on same phenotype
-NEED BASED
systematics
the study of biological diversity and its evolution
taxonomy def and goal
the science of biological classification, how organisms are assigned to taxa/ groups
-goal: utility and monophyly
nomenclature def and goal
-process by which taxa are named
-goal: stability
systematics rules
1) taxa are arranged in hierarchical ranks
2) names are treated as if Latin regardless of origin
3) species names are binomials ex: Solanum tuberosum L.
phylogenetics
study of evolutionary history and relationships among individuals/ groups of organisms
what does the length of branch represent in phylogenetics?
time that taxa has been evolving
terminal
a species
branches
lines in a phylogenetic tree that connect nodes –> node
terminal –> node
nodes
where branches intersect (represent ancestors)
MRCA
most recent common ancestors
-nodes of terminals
clade
a group of organisms believed to have evolved from a common ancestor
root
MRCA of the ingroup (point that connects ingorup and outgroup)
character
a feature common (homologous) to al terminals sampled
character state
what a character looks like in an individual
polytomy
more than 2 lineages diverged and dont know how
polytomy
more than 2 lineages diverged and dont know how
sister taxa
indicates lineages that share a branch point
basal taxon
oldest species, most ancestral
branch point
indicates where 2 lineages diverged
monophyletic groups
contain all descendants of a MRCA
!!!! goal!!!!
polyphyletic groups
exclude MRCA of its members
-not good
-inferred relationships
paraphyletic groups
exclude descendants
apomorphy
derived character unique to a clade
synapomorphy
-an apomorphy SHARED by 2 or more taxa
-(homologous traits from common ancestor)
-most important trait when creating a tree
autapomorphy
characters UNIQUE to a single TAXON and are uninformative for assessing relationships
plesiomorphy
ancestral evolutionary trait homologous within clade but not required to that group
symplesiomorphy
plesiomorphy shared by 2 or more taxa found in earliest common ancestor
what is homoplastly?
-similarity in traits NOT due to common descent. OUT OF NECESSITY
what causes homoplastly?
1) convergent evolution
2) parallel evolution- implies that same phenotype evolved in 2 separate lines from same ancestral phenotype
3) evolutionary reversals- the return of a derived character state to ancestral character state A-> T -> A
phenotypic plasticity
capacity of 1 genotype to exhibit different phenotypes in different environments
-mechanism of environmeorthologntal variation
