Final - Part 3 Flashcards
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What is the ultimate source of genetic variation?
MUTATION of nucleotide sequence
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What does variation in a population mean?
What does success of an organism mean?
We think about genetic and phenotypic variation at the level of a population of the same species
success of an organism: measured by the # of offspring which are contributed to the next generation.
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Fitness
Define it. But it’s not that important
Quatification of an individual’s genetic contribution to the next generation
It’s not all about how well it could survive
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Toward Evolutionary theory
Jean-Baptist Lamarch + criticism
- Proposed inheritance of acquired characteristics as a mechanism for species to change over time
- Use it or lose it - repeated use of a trait changes and strengthen it (vice versa)
- These strengthened & advantageous characteristics are passed on to offspring
- For example, if a giraffe stretched its neck to reach leaves high up in trees, its offspring would inherit longer necks.
- Criticism: how is that passed on genetically??
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Charles Darwin
- Gradient of Variation in appearances depending on the environment the species live in
- Natural selection
- There are variations in heritable traits within populations
- Some variants are more successful and more able to reproduce than others in a given environment.
- The popuation thus changes over time with respect to this trait.
- Born with certain traits, not acquiring it.
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Natural Selection
The more successful variants are thought of as being selected by its environment
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3 Types of Selection from selective pressure
Which one is the most likely to form new species?
Draw diagrams
- Stabilizing selection - decreasing the range between the phenotypes to an average
- Directional selection - Going to 1 direction (white -> black moth)
- Diversifying selection - No in between, going to 2(or more) extreme ends
- MOST likely to result in the formation of new species
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Artificial selection
Example of it
Humans deliberately directing how poulations change over time
Domestication: Wild species traits selected that are often not advantageous in the wild
Ex) dog breeds, wheat
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Population changes that’s NOT by natural selection
Genetic drift: population change by LUCK
- Certain individuals can’t reproduce suddenly due to luck.
- 갑자기 내가 파리채로 파란 파리들을 몰살하면 우짜것어
- MoRe likely to happen when the population is small
Genetic bottleneck: drift to the extreme!
- A sudden loss of population can dramatically change the traits and variation of a population.
- The survivors are the only contributors to the gene pool
Founder effect: Reverse bottleneck(?)
- A small population that moves into a new place is just a sample of the old population’s diversity
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Species concept
What makes a species
- Its provides us ways to categorize life
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Morphology
Using physical similarity/difference to delineate species
- colours/shape
- But it’s NOT a good and meaningful way
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Biological species concept + criticism to this definition
definition of species + 4 criticisms
Species: a group of organisms that are capable of interbreeding, and can produce viable offspring that can also reproduce
Criticism:
1. Cannot be used to define asexual species
2. What we think are separate species might be able to reproduce by mating each other (라이거 같은)
3. Extinct groups are impossible to verify
4. Interbreeding populatins might display meaningful morphological differences (we might want to categorize them into different species)
1 way to define a species that works for all organisms doesn’t exist yet
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Binomial species names + why name species this way?
2 reasons
Each species has 2 names:
Genus + Specific epithet
- Standardized, “universal” language between biologists
- Each organism can have only 1 binomial names but often have multiple common names that could cause confusion
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Linnaean Classification System
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
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All species in a genus should share a____
Common ancestor
ex) all members of the ‘Canis’ genus share a common ancestor (dogs, coyote, wolves)
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Key properties that separates 2 species
2
- Separate species should NOT be able to interbreed
- Populations that cannot interbreed are: reproductively isolated
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Reproduction Isolation(barriers between species) can occur by:
3 cases - summary
1. Temproal Isolation
2. Habitat Isolation
3. Hybrids not being viable
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2 Categories of reproductive isolation
- prezygotic isolation: individuals can’t physically meet and mate
- postzygotic isolation: individuals can mate, but the offsprings are inviable or infertile
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Temporal Isolation
pre? post?
Species don’t interbreed because reproduction happens at different times
- Common in olants & insects
- Prezygotic isolation
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Habitat Isolation
Species do not interbreed because they occupy different habitats
- Prezygotic isolation
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Hybrid Inviability
Species can interbreed but the hybrid offsprings do not survive or offsprings are infertile
- Failure to survive to sexual maturity
- Embryonic development failure
- Postzygotic isolation
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When does a new species arise?
- species is evolving through time, capable of mating, enabling gene flow.
- barrier rises! Dividing the population
- Gene flow disrupted
- Changes accumulate that cause reproductive isolation
- New species emerge
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2 Types of Speciation
- Allpatric speciation
- Sympatric speciation
-> Both of them are related to where the two species are when they diverge
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Why/When would gene stop flowing?
3 reasons
- Individuals will also not necessarily stay in teh same place
- The environments can suddenly change
- Randome chance and other processes can also eliminate portions of the population
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Allopatric Speciation + 2 types
Geographic separation physically prevents species from interbreeding
- Either species moving to isolated islands or the geological change separate the population
- Vicariance: Water spliting land
- Dispersal: new small island created next to the main land become bigger
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Sympatric Speciation + Adaptive radiation
Sympatric Speciation: populations not physically isolated but an also result in speciation.
- Diverging/Disruptive selection causes sympatri specition.
- Adaptive radiation: when. founder population colonizes a new area, new species can rapidly emerge as the offspring begin settling into their own unique niche and diverging in characteristics from the original founder population.
- This occurs when teh founder populations are still in contact
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Hybrid zone
When imperfectly isolated species come into contact, the balance between interbreeding and selection against hybrids can maintain a hybrid zone
- 2 opposite forces controlling the population of the interbreeding hybrids
- That area is the hybrid zone
- Hybridization could form new species
- More likely in plants (orange + pomelo = grapefruit)
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Ecology
Define it
Study of the interactions of living things with their environment.
at both single organism and ecosystem levels
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Ecological Niche + 5 aspects of life history
Range of environmental conditions/resources a species can tolerate within its ecosystem
- In a given ecosystem, each species settle into their unqiue ecological niche
- Niches can change over time
- The life history of a species can determine the niche
Aspects of Life history:
1. Size of mature individual
2. Timing of maturity
3. Parental care
4. Offspring #: Ferundity
5. # of reproduction events in lifespan
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Population ecology + important values of population ecology calculation
Population ecology: Concerns how populations change over time in a given environment
- Measure changes in a population in response to biotic & abiotic factors.
Some important values:
1. Population size
2. Density
3. Distribution
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Models of Population growth
4 variables
N = # of individuals in a population
t = time span
r max = the max growth rate of the population (Birth & death rate)
- Life history determines this
K = Carrying Capacity = the maximum population size that a given environment can sustain
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2 Models used to generalize population changes
Exponential growth model
- Population change if resources are UNLIMITED
- a population will increase consistently and indefinitely
Logistic growth model
- Resources are LIMITED
- There is Carrying capacity
- The limit’s impact increase as the N approaches K
These are theoretical though
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2 other things that regulate population growth (that’s not K)
Which one is abiotic and which one is biotic?
Density dependent regulation:
- At high densities, there is more competition for limited resources
- Disease spreads faster
- Individuals are more easily preyed upon
- ALL BIOTIC FACTORS
Density Independent regulation:
- Seasonal changes
- Disasters
- Regardless of how many species there are
- ALL ABIOTIC FACTORS
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r- vs K-selected species
K-selected species:
- Staying close to K (maximize spending energy on fewer offsprings)
- 질로 승부
r-selected species:
- Maximize reproductive rate (r)
- 양으로 승부
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How to determine K?
We need to determine what the limiting resources are
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Community Ecology + 3 types of symbiosis
Define it
Community Ecology: How species interact with each other
1. Competition
2. Consumption
3. Symbiosis
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Competition
- Competitive exclusion principle
- Resource partitioning
- What if the niche completely overlap?
Don’t forget the +. - sign
When 2 species in a community can use the same resources (niches overlap) there is competition
- Neither of the species benefit from this interaction (-, -)
Competitive Exclusion principle: species can’t occupy the same niche.
Resource Partitioning: one or both species will evolve to modify niches until they no longer compete
If niches completely overlap, one species could be forced out of the community or extinct
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Consumption
- Heterotrophic species?
- Predation & Herbivory
- Nom nom food
- (+,-)
- Predation: Where an individual of one species KILLS and eats another for food
- Herbivory: one species eats an autotroph
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How predation & herbivory drive evolutionary arms races
3 ways + how plants do it
Species selected for adaptations to avoid being eaten or consume food more effectively.
1. Camouflage / warning coloration -for both prey & predator
2. Mimicry: warning colouratin but animals piggyback on the true warnings of a different species
Plants:
- Being pointy
- Poisonous
- Caffeine
- Etc
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3 main types of symbiosis
- Parasitism
- Commensalism
- Mutualism
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Parasitism
Parasite species benefits but host negatively affceted
- (+,-) (or +, 0)
- A parasite usually takes nutrients from its host
- Host could die but not necessarily (cuz then where would the parasite live)
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Commensalism
1 species benefits while the relationship remains neutral for the other
- (+, 0)
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Mutualism
- BOTH BENEFIT
- (+,+)
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Red Queen hypothesis of evolution
A species MUST adapt and evolve not just for reproductive advantage, but also for survival because the competing organisms are also evolving
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Community dynamics
- Primary succession
- Secondary succession (r- or k-selected species are more prevalent?)
Study of how community composition changes
Primary succession: immediately after a disturbance, pioneer species adapted for the disturbed environment took over and formed a community
Secondary succession: the community changes to different species to reach an equilibrium state of the area
- r-selected species are more prevalent in that area cuz they reproduce quickly
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Food chain & food web
Food chain: a linear network of links in a food web
BUT
Many organisms eat organisms from different trophic levels
it’s better to organize into food web
