Chapter 2 - Ecology's Evolutionary Backdrop (CHAPTER + SLIDES) Flashcards
slides notes are included!!
Theory of natural selection & “struggle for existance”
2 Ecologists
- Charles Darwin
- Alfred Russel Wallace
How many fundamental truths of evolutionary theory?
4
Fundamental truth 1
Individuals that form a population of a species are not identical
Fundamental Truth 2
some of the variation between individuals is heritable
Fundamental Truth 3
all populations could grow at a rate that would overwhelm the enviornment; but in fact, most individuals die before reproducing and most reproduce at less than their maximal rate
Fundamental Truth 4
Different ancestors leave different numbers of descendants.
Evolution Definition
The change over tume, in the heritable characteristics of a population or a species
Fittest definition
The proportionate contirbutions that an individual makes to future generations
- survive better
- reproduce more
- leave more descendents
Human selection
Has an aim for the future
- it is not nature
- Natural selection tends to have past enviornments that have selected particular characteristics that we see in the modern day.
Variation occurance
happens despite conservative characteristics of a species
- two populations will NOT diverge if the members or pollen of the organisms continiously migrate and mate mixing their genes.
Intraspecific Variation
Natural selection and evolution within a species
Countergradient variation
Genetic differences counteract enviornmental effects, which reduces the phenotype differentiation between populations.
Hybridization
the production of offspring sharing the characteristics of two parents
Reciprocal transplant experiments
- compare things grown in their natural habitat vs when they’re away
- investigates local adaptation and selection
Ways in which natural selection can occur
- Predation
- Pollution
Sources of variation
- Age
- Sexual differences
- enviornmental factors
- Individual difference in inherited traits
Co-evolution
a result of reciprocating selection
- can be mutualistic or antagonistic
Biospecies
“Two individuals that can breed together in nature to produce fertile offspring”
for something to not be classified as a biospecies there must be a barrier that can prevent gene flow
Ecological Speciation
1) ecological source of divergent selection
2) means of reproductive isolation
- both free of sudden change.
Pre-Zygotic Isolation
Prevents offpsring production
Post-Zygotic Isolation
Fails to produce offpsring (NOT PREVENT.)
Geographical isolation
Geographical barrier
- if this occurs and then the subpopulations that were split meet up again, that can actually reinforce reproductive isolation.
Allopatic phase
subpopulations in different places
Sympatric phase
subpopulations in the same place
Allopatric speciation
- Islands, dawins finches
Island endemics
Species that are only known from one island or area
- explained by techtonic plate movement
Ring species
Multiple subpopulations that can interbreed but when two ends meet they can’t
Sympatric speciation
Endemism (occurance of many endemic species together)
Changes in climate & how they affect plant and animal distribution
Cycles of glatiation => retreating tropical species to specific spots, creating an endemism hot spot.
Changed pollen distrubiton
Greenhouse effect by humans => endangering all species.
Parrallel Evolution
The similar development of a trait in two distinct species that share a similar original trait in response to a similar evolutionary challenge / pressure.
- explained by techtonic plate movement
- example: placental & marsupals in australia both diversified from a common ancestorial line and inherited a common set of potentials & constraints.
Analogous Structure
Similar in function
Homologous Structure
Similar in bone form and from a common ancestor.
Convergent evolution
Analogous structures, two different things converge into one similar thing.
Example: Bat and bird wings
Founder effect
A pool of founder genes have astrong influence on the development of the population. EXAMPLE: the amish.
1) Start with big pool of genes
2) split into subgroups that dont reproduce with others
3) the subgroups’s genes found the rest of that groups genes
4) limited to those genes.
Population bottleneck
An evolutionary even where a large % of a population is killed or prevented from reproducing
Graph:
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RECOVERY
Or
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-—\
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EXTINCTION
