BIO FINAL EXAM Flashcards
Ecology is the study
- How organisms interact with each other and environment
- Distribution and abundance of species
- Structure of function of ecosystems
- Science of biodiversity
Ecology vs Enviornmentalism
Environmentalism: social and political movement
(people being more ecoally aware)
Model organisms
stand in for all animals and plants
Mice: for vertebrates
Fruit fly: insects
Arabidopsis thaliana: plants
Population
Community
Ecosystem
individuals of the same species in one place at the same time
species living together at one time
all the species plus nonliving environment
Species Ranges: what is it?
We don’t know more than 85% of species and bacteria have the most species.
Knowing species range tell us where plants and animals grow
Good cuz they give us food, clothing, medicine
Predict how biodiversity will react to different things like
Habitat destruction, pollution, invasive species, climate change
For microbes and infectious disease agent: to determine disease risk
Determining specice’s range
Dispersal
Climatic and other inexhaustible conditions (unlimited ie temp, salinity)
Food or other exhaustible resources (limited ie space, nutrients)
Species interactions e.g competition, predation, or mutualism
These factors vary across space and time: gradients of conditions
Organisms perform best at certain portions of gradient
Determining abundance
Example: THE SIXTH EXTINCTION
Ongoing mass extinction due to mostly human actively
32% of known vertebrate species are decreasing in population size or range.
Important people to know:
Lynn Margulis: Created theory of symbiogenesis, arguing that modern plant cells are the result of the merging of separate ancestors (symbiosis).
Thomas Malthus: Has a theory stating the food supply can’t keep up with the growth of human population, resulting in disease, famine, war, etc.
Spieces tolerance
Climate and other niche axes
Species have ranges of tolerance along environmental gradient
The ecological niche
combination of physiological tolerances and resource requirements of a species
A species place in the world (what climate it lives in what it eats etc)
The Hutchinsonian Niche
Considers the niche as an n-dimensional hypervolume where each axis is an ecological factor important to the species we are talking about.
Outside of the blue area (ellipses) a species cannot survive
Temperature: mostly a function of latitude - How does it affect latitudes
Warmer at equator closer towards pole
Higher latitude colder: seasonality is a function of temperature (winter summer)
Lower latitude is warm: seasonality stays the same year round
Reasoning: at higher latitudes, light strikes the earth’s surface at a lower angle and is spread over a greater area: photon density not as high
The tilt causes seasonality - winter the tilt is shaper meaning less light hits it
What are hadley sells and how do they work
The hottest air is at the equator and hot air rises (think of hot air balloon)
Hot air rises up from the earth’s surface and into the upper atmosphere at the equator where they eventually start drifting south and north of the equator and fall back down around 30 degrees north and south in latitude
As air rises, it start to cool down at adiabatic lapse rate - 5-10 celsius/km
As air cools, water vapor condenses causing rain to fall near equator and air warms as it falls
Resulting in dry high pressure agrees at 30 degree latitude
Ferrel cells - 30-60 & Polar cells - 60-90
Coriolis effect
the earth’s rotation deflects winds
Air masses near earth’s surface are spinning together with earth as earth spins around its axis
Objects spin at diff speeds depending on latitude
Near equator it moves fast cuz it has has to move equal to earth’s circumference in 24 hours - around 40000 km/24hr north pole you have smaller circumference so they don’t move as fast
Because the storm is moving faster than the points on the ground beneath it are moving eastwards it overshoots its points
Intertropical convergence zone
shows a rain clouds across the planet at the equator
Not exactly above 0 degree in latitude but moves around
Moves 23 degrees north Tropic of cancer and 23 degrees south capricon
It’s at the location of ascending branches of the hadley cells
The convergence zone moves more in Asia because there is more landmass in asia VS in the Americas, there is more thermal inertia than land masses which mean they resists changes
Land heats and cools faster than water therefore greater swings in temp therefore move movement of intertropical convergence zone
Movement of intertropical convergence zone causes seasonality in rainfall in the tropics
Monsoon season in asia’s vs dry seasons COMPARED to america that is rainy
Coriolos effect (general definition):
objects appear to be deflected eastwards as they move away from the equator and deflected westwards as they move towards the equator
Coupled cells + coriolis effect
prevailing wind patterns
0-30 degrees towards equator air deflected westwards
Easterly winds: blow to the west and originate to the east
Westerly winds: blow winds to the east and originate in the west
30-60 degrees away deflecting east
60-90 degree deflecting to the west
weak winds
Right at the equator and 30 degrees winds blow straight up to upper atmosphere - weak winds
The affect of land mass
More land mass at northern hemisphere affects wind speeds
At 44 degrees north we get moderate westerly winds cuz landmass breaks wind speed
At 44 degrees south lost of wind cuz theres mainly ocean
Vegetation growth (primary production) increases w moisture and temp
Biomes - regions w certain computations of moisture and temp
Similar latitudes tend to have similar biomes
Desserts occurs at 30 degrees north and south
Additional climate patchiness overlaid on basic latitudinal belts
Oceans provide thermal inertia
Precipitation
Evaporations high from warm bodies of water
Orographic precipitation: air forced up mountainsides undergoes cooling, precipitates on upper windward slopes which lead to rain shadows created on leeward slopes of mount ranges
Animals and biomes
Animals geographical ranges often correspond to biomes ie climate or vegetation
But transient biomones (ecological versatility), recent history eg limited dispersal, and being limited by other organisms (enemies, friends) are exceptions
Ecological niche modeling use data from a species present distribution to predict where they can leave
Physiological ecology
the study of physiology in the context of an organism’s ecology
Ranges of tolerances: limit distribution
Organism: complex chemical reactions
Enzymes function best at optimum temp and osmotic condition: fitness is maximized
Mechanisms for homeostasis: evolved to challenge hostile environment
Maintenance of homeostasis: requires energy and is limited by constraints and trade off
What do orgaisms physiology reflect
the climate and other conditions its adapted to
Diff environment lead to different physiologies
Similar environment lead to similar adaptation (convergent evolution)
Heat Balence + why is important
especially important to homeotherms (birds, mammals)
Poikilotherms
(most reptiles, amphibians, fish, invertebrates) lack physiological means to deviate from environmental temperature: their temperatures fluctuate
Poikilotherms have lower energy requirements than similarly sized homeotherms because it maintaining constant temperature requires energy
Homeotherms
must regulate heat balance to keep internal temperature within a narrow range: many traits contribute
Modes of heat gain and loss
Radiation: heat transfer by electromagnetic radiation
Conduction: direct contact w substrat
Convection: moving fluid (air or water)
Evaporation: cooling from wet surfaces
Redistribution: circulatory system redistributes head among body parts
SA VOL
Size matters to heat balance because of surface area to volume ratio
Surface area determines equilibration rate - big SA:Vol equilibrates quickly
Volume provides the inertia
Bergmann’s Rule
Homeotherms tend to be larger at higher latitudes to conserve heat
Shape matters:
SA is needed for function - particular shapes
Therefore the shape is a trade off and adaptive compromises
Allen’s rule
Homeotherms tend to have smaller appendages at higher,colder latitude
Ways to counteract heating up + allens rule tie in
Insultion: more important than size and shape
Fur, blubber, feathers
Animals spend a lot of resources for insulation
Convective cooling is enhanced by vascularization
- Desert hares ears blood vessels
Countercurrent circulation to limbs conserves heat: Arteries and veins should appressed (close together) in appendages to conserve heat
Separated in appendages designed to shed heat
Countercurrent flow maintains gradient so head is always flowing from outgoing blood to incoming blood
Evaporative cooling
Behavioral thermoregulation: seek out cooler places on a hot day
Trade offs and example of weseal
cause animals to not be perfectly adapted
Being good at x may necessarily imply being bad y
Weasels are the shape they are to be able to hunt for gophers
Constrains
Natural selection builds on what’s already there
Plany ecophysiology
Plants cant evade stress by moving
- But they make their own food - autotrophs
- Photosynthesis light, co2, and water
- Leaf stem and roots reflect adaptation
Angiosperm flowering plant
Hermaphrodites: have both and male and female parts
- Anthers: pollen - male, stigma - women
- Depend on animals to move pollen
Plants are sessile
they have little scope for behavior
Are autotrophic and they need the same things to grow: light, Co2, water, soil nutrients
Plants bring CO2, water and light in functioning photosynthetic tissue to create carbohydrates and o2
Enzymes need to be at a good temp
Respiration turning carb and oxygen into co2 and h2o
Carbon balance: for growth plants have to acquire more carbon through photosynthesis than they lose through respiration:
Net primary productivity (NPP)
C gained via photosynthesis - C lost via respiration = NPP
Photosynthetic structures embody adaptation to environment
Example of conserveing water
PALO VERDE
Photosynthetic bark on trunks and branches: can grow without incurring head load and water loss through
Sometimes even sheds all its leaves as an adaptation
Microphyll: super small leaves
PLANT FEATURES THAT MAKE THEM WHAT THEY ARE
Chlorophyll make plants green
Plants take in CO2 through stomata but they also lose water through stomata (transpire)
Leaf size and shape: SA:V ratio important again
Large leaf surface: good for light and gaining CO2
Cost: easily transpire and therefore cause overheating
Coping with overheating/water loss
They use rubisco to carbon fix but it doesn’t work at high temp
Sometimes catches o2 instead of Co2
Plant defence to waterconservation
C4 photosynthesis: enzyme pepe carboxylase accepts CO2
CAM photosynthesis: close stomata during the day avoiding waterloos, open at night to let in CO2 and store that CO2 as maltate to be able to do photosynthesis during the light
Large leaves grow in shady habitats and open and close their stomata by opening stomata cuz stomata releases water for evaporation cooling (hormone ABA is responsible)
Trade off between water conservation and rapid growth
Conserve water vs carry out photosynthesis seen on desert plants
Rainforset adpations
VS TROPICAL
Extensive but shallow because rainforests have a shallow of nutrient rich soil
Root foraging
Going roots into soil patches where nutrients are abundant
Split root experiment to see how roots adapt
Legumes also get nitrogen from nitrogen fixing bacteria
Take Dinitrogen from the air and turn it into a form via nitrogen fixation
Deciduous habit: leaves gone during cold or dry seasons to reduce water stress/ tissue damage
Population ecology
N - Number of individuals in absolute terms (y axis, time on x axis - Time Series)
N/area - population density
Leaf shape influence
Limar vs turbulent flow
Limnar: unimpeded moves like aerodynamic like moving over a car
Cases a stagnant boundary layer of air to build up on the leaf surface: Prevents gas exchange
Turbulent flow: ridges and irregular
Does a better job at promoting gas exchange
Morphological plasticity
Epiphytes have their roots in the air or on trees so they can still be water stressed even in rainforest
Why care about N?
Natural resource management:
Ex size of fish stocks in ocean
Abundance of outbreaking insect pests in forests
How much damage they do to forests
Conservation: Population declines of species
Health: Monintstoring population or bacteria in humans
Understanding and predicting human population growth
Basic science question of what limits population growth
Goal of most population models
Predict the trajectory of population through time ie N as a function of t
How many populations are in the population now? Nt
Time advances by one so t - t +1: How many individuals are in the population one step later: Nt +1
General model: Nt+1 = f(Nt)
Malthus
scientist said Human population cannot grow faster than food production
Time steps
When using differential equation, time steps are infinitesimally small: use concept of limits and calculus growth is smooth and is best suited for species w continuous reproduction
Ex population size of humans
Difference equations: time steps are discrete (days, years), use it iterated recursion equations
Best suited for episodic reproduction
Lambda
Nt+1 = Nt x (lambda)
Lambda: Nt+1/Nt the multipleive factors by which population changes over one unit of time
Lambda > 1 births exceed dead population is growing
Notation
Therefore population growth starts at t = 0 therefore N0 or N(0)
How can N change from Nt to Nt=1 (All happen in one time step)
D = number who die
B = number born
E = emigrate
I = immigration
Nt+1 = Nt - D + B - E + I
Births and immigration are equivalent, Death and immigration are equivocation
Only model births and death and assume no immigration or emigration
Treat birth and deaths during one time step per capita rates that are fixed constant - dont expect birth and death rates to be changing a lot
Consequences
Main consequence of an exponential model growth is that when it increasing it will increase til infinity (exploding in an exponential way)
All species have the potential for positive population growth under good conditions(lambda greater than 1)
All species have the potential for negative population growth under good conditions less than 1
But no species has ever sustained lambda more than one or less than 1 for a long period
Density-dependent regulation (growth depends on N) or Density independent reduction
Geometric growth
Geometric growth
N1 = lambda (N0) N2 = lambda (N1) = N2 = lambda ( lamda (N0) Therefore Nt = N0lambda ^t
Continous time
assumes population growth is instantaneous
Instantaneous, per captivate rate of population change = b-d = r (a constant)
r= intrinsic rate of increase
Differential equation = dN/dT = rN General continuous time: Nt = N0 e ^ rt
Exponential growth if r > 0 Ln (lambda) = r
Logistic growth
S-shaped growth = logistic growth (only happens when populationstarts low)
Same as exponential growth with a new term added for breaks
dn/dt = rN (1-N/k)
K = carrying capacity - the size of the population that the resources in the environment can support
General equation
Nt = (KN0e^rt)/(K+N0 (e^rt - 1))
Pros
Inflection point at K/2 aPros:
Mathematically tractable model of intraspecific competition and simple
Can be expanded to consider multiple species competition
Cons of logistic growth model
too simple
Always a gradual approach to carrying capacity
In reality density dependence is likely to be non linear
Allee effects
negative effects of low density
Arise from social benefits ex mate finding, group living and group defense
Issue of the models
But Fecundity and survivorship depends on age
Species have diff life history strategies
Life story : what age do events occur at
Typical life history
Start life small size
Grow for a period without reproduction- resource accumulation
When they have enough resources and become mature they prediction
Some expend all resources at once some spread it out cuz they have various lifestyles
Need to consider age structure and how birth and death rate depend on age
Age structured population growth
Still single population but now fecundity and survivorship vary w age
Variation is summarized by life tables of age specific rates
Important implication for:
Evolution of life histories
Conservations
Understanding changings structure of human population
Age-sex pyramid
Stable age structure - instead of period it’s gonna be a flat shape - roughly the same number of individuals in the same age
Life tables
Life tables: summarize the life events that statistically expected for the average individual of an specific age in population
Age of death and age of timing of reproduction
Suvivorship schedules
Age classes denoted subscript x
Lx = probability of being alive at age x
L0 = 1.0 cuz when a baby is alive its always 1
“Survivorship curve” graph of lx vs x
Lx necessarily declines with x
If mortality is constant then its gonna have an exceptionally curve: Usually use plot w log(lx)
Type 2 - straight line
Type 1 - survivorship high in early live and then declines rapidly at old age (ex humans)
Type three - early mortality but after middle age survivorship is high
Impact of growth rate
Higher growth rates = higher fitness
Constraints and trade-offs: reproduction is costly. Longe reproductive periods allow for accumulate more resources
Semelparity: ate in life reproduction
Iteroparity: multiple years of their life reproduction
Fecundity schedule
Age defined by x again
Mx = number of daughters birth to a female of age x during the interval of x to x +1
Shape of mx is specific to species
Reproductive period usually preceded by resource accumulation phase
Fecundity - survivorship trade-offs = cost of reproduction
Net production
R0 = average number of daughters a female has in her lifetime
R0 = Sum of lx mx
Unit of one generation
Generation time (Average age at which a female gives birth) T = sum of x lxmx/r0
X = female age
r = ln(R0)/T = ln(lambda)
Plant life history cateorgies
look at doc
Life expectancy
Life expectancy = ex
Reproductive value vx = expected number of future daughters left to an individual age x
Fitness consequences of alternative life history straighteners and trade off between current reproduction and future
Selection generally selects for early prediction so genes can be copied but u need to accumulate resources which can delay reprodction
Specific compeition
Intraspecific competition (conspecifics): same species competition for resources
Interspecific competition: different species
Scramble/exploitative competition: depletion of a shared resource
Ex squirrel eating bird food leaving less food for birds
Contest/interference: direct interactions ex battle over territory
Invasive ants fight harvester ants: Invasive often drive down population of native ants
Possible outcome of lokta model for interspecifc compeititon
dn1/dt = r1n1( 1 - N1/K1 - (a12N2)/K1)
a= alpha aij = per capital effect on specifics one of individuals of species 2
“Competition coefficient”
A is fixed for a pair of species
Convert individuals into an equal number of individuals of species one because species are not equivalent competitors
Possible outcomes
Two species stably coexist
Species 1 may always win (N1 = K1, N2 = 0)
Species 2 may always win ( n2 = K2, N1 = 0)
Indeed of winner may depend on starting N’s
Outcomes depend on values of K’s and a’s
Coexistence requires both species to inhibit their own growth more than they inhibit each other’s
Can expand to consider n species
Equlibrium, stability, coexistence
Equilibrium = N’s no longer changing (dN/dt = 0)
For a community: a community not changing over time meaning that all populations in a community at equilibrium
Generally: constant species composition over time
Stability : ability of a system to return to equilibrium following a disturbance
Coexistence: two or more species have non zero population sizes at equilibrium
Principal competive exclusion
Principal competitive exclusion:
LVM predictions that for two species to co-exist competition between species muscat be weaker than within species (Old idea - 1934 gause said)
Paradox of plankton
Competitive exclusion seems false for plankton (also rainforesets cuz all the trees live together)
WHY? Lotka volterra models too simple and ignores too much relative
Real populations be ne kept below K
Lotka volterra model for predator prey
Lotka-Volterra models for predator-prey interaction tend to cycle
Similar to competition models: two differential equations
Repdicy couple lagged population cycles
These cycles are hard to sustain in a lab -
Most common result: predator and prey do not coexist, interaction is unstable
But cycles in natural are unusual
Additional factors
Heavy browning regulates food available - hares may also be cycling w food
Most natural cycles have complex causes
Antagongistic vs coevolution
Coevolution = reciprocal adaptation
Prey evolves defenses - predators counteract w new adaptations to get over defenses
Life dinner principal
unequal election pressures
Prey should be under stronger selection to make defenses than predator to make counter defenses cuz life vs food
Defences are often inducible + example
Human immune system
Reply morphology, chemistry and behavior
Plant secondary chemical
Predation and community structure
Competition decrease biodiversity = superior competitors exclude inferior
Predators and parasites also influence biological invasions
Invasive species achieve high population size and have a negative effect
Enemy release hypothesis: invaders impacts result from having fewer natural enemies in their new range compared to their native range
Many parasites have complex life cycles
Single host spices = direct life cycle
Many requires two or most host species to complete life cycle = complex life cycle
Vectors are hosts that transport parasites to next host
Zoonotic diseases: diseases transferred between animals and humans
Often refer to other host species as reservoir
Distribution, life history traits, and behaviors of hosts can affect parasite abundance and transmission
Community ecology of disease
Dilution effect: for seieases that infest many host, host diversity can dilute disease risk to humans or animals - conserving host would be good
Amplification effect: most host or vector species can support larger populations of disease causing organisms increasing risk to humans or animals
Latitudinal gradient in species richness:
More species near the tropes at the equator than the poles
Age or time the habitat has had accumulate species = most places near poles were under ice
Maybe climate
Relating back to predation - moew human pathogens are near the tropics and equator
But a good part of this is based on government stuff ie healthcare spending
Mutualisms typically involved reciprocal exchange of goods or services between species
Nutritional mutualism
Legumes and rhizome: exchange fixed c for fixed n
Defensive mutualism
ants and plants exchange protection for food
Dispersal mutualisms
Plants and animal seed dispensers: exchange seed dispersal for food
Plants and animal pollinators: exchange gamete dispersal for food
Mutualism between humans and free living wild animals
EXAMPLE
Yao people in mozambique harvest wild honey so they use honey guides birds to get them to the nests because honey guides only eat the bees waxes
Has been around for at least 500 years
Playback experience: play a series of sounds to see how birds react
Showed that the birds were able to understand and signal humans to where the bees next are
Limits of the population growth of mutualists?
Strong intra-specific competition
A third species or competitor
Diminishing return to mutualism as the population grow
Only mutualists when the population is small but not large
Invasive meltdown
the process which two non-native species facilitate one another’s spread
examples of invasive meltdowns
Spring ephemerals
Produce short-lived carpets of flowers which flow right after snow melts
Seed dispersal between native anit vs invasive red ant
Invasive red ant spreads a lot of seeds in europe so she wanted to see if it did the same
Used a experimental mesocosms
Invasive ant caused the invasive plants to move around more vs native and did more with native plants
Are mutualistic relationships often highly specialized?
But most mutuals are NOT tightly coevolved
Reciprocal adaptation (coevolution) between flowers and insects
and example
Aphids feed on phloem sap that is rich on sugars but poor in essential amino acids
Adapids have intracellular bacteria that provide their hosts w essential amino acids
Buchera are vertically transmitted: passed on from mothers egg to off spring
Vertically transmitted endosymbionts often have tiny genomes
Buchnera has a much smaller genome than free living bacteria
Other endosymbiotic bacteria also have tiny genomes
mitochondria: - 17000 base pairs only codes dor 37 genes vs nuclear genes that have 3 billion
Endosymbiotic bacteria lose genes that they no longer need
Some functions are unnecessary cuz theyre no longer freelivig and are protected
“Outsourced” to host genome
Horizontally transmitted
Partners are anew each generation
Mutualisms are rarely one to interactions - usually many
Current hot area of research:
Understanding networks of interactions among large number of species
Microbiomes: all the microbes living together or those collectives
Most plants have many pollinator species; most pollinators visit many plants species
Meta populations
“population of populations”
DIspersal connects populations
A metapopulation is a collection of spatially distinct populations that are connected via dispersal
We call each spatially distinct population a “patch”
Dispersal is important for…
colonization of new habitats
Postglacial colonization depends on plant and animal dispersal
Metapopulation and population persistence - source-sink
Metapopulation structure can allow population persistence even when individual populations are doomed
Local populations can be re established by colonist by other populations after going extinct
Source-sink dynamics
“Sinks” are populations in a small habitat patches that would go extinct expect
Migrants from”source” population “rescue” these populations
Things that can counteract stuff that influences disperal of speices
Predation keeping competitive exclusion from going to competition
Non-equilibrium conditions, habitat patchiness, rescue by migration, variation in life history strategy
WHAT DETERMINES THE NUMBER OF SPECIES ON AN ISLAND
Colonization: a species can arrive on island from else
Extinction: species can go locally extinct on island
In-situ specification: a lineage can split in two on a island but its a slow process
Theory of island biogeography
Predict the number of pieces on an island from the island size and isolation (distance from mainland)
Ignores in-situ speciation only colonization and extinction
Graphical model rate on y number of spices on x
Point where they cross is the equilibrium
Near island is easier to colonization so it has a higher colonization rate therefore greater species
Larger species have a smaller extinction rate so it has a higher equilibrium rate
Trophic levels
Primary producer: plants
Primary consumers = herbivores
Second consumers = predators = carnivores who eat herbivores
Tertiary consumers who eat secondary consumers
Decomposers eat dead organic matter
Higher biomass at lower trophic levels
Decreasing biomass as you go up
Trophic cascade
Two interactions between two trophic levels cascade to a third trophic level
When a predator eats a herbivore which lets plants grow
solid line = direct
dashed = indirect
Top-down vs bottom up control
Top down: advance kept low cuz of predation
Experiment test = remove predator
Bottom up control: abundance kept low because of resource limitation
Experiment = resource addition
Trophic hypothesis: Green world hypothesis - why is the world green
World is green because carnivores keep down herbivores now that herbivores don’t limit plant growth
Example of indirect effect to
Trophic cascades involve effects across trophic levels
Can drastically affect communities
Special difficulties of herbivore
Easy to be a carnivore: animal tissue easy to convert into animal tissue
BUt plant tissue is hard to convert into animal tissue
Cellulose and lignin tough indigestible without microbial symbionts
Plant tissues heavily defended against herbivores
Coevolution between plants insects herbivores is responsible for much biodiversity: specialization is common
Monarch butterfly can evade the milkweed toxins
Plant-herbivore interactions as an arms race
Plants evolve toxins to reduce herbivory; insects evolve detoxification or other mechanisms to overcome plant defenses
Very common (we think plants taste OK because our food crops have been artificially selected for low toxicity)
Many types of secondary chemicals; alkaloids especially potent and prominent
Chemicals often deleter generalist herbivores
But no plant species is toxic enough to escape from specialist herbivores
And special insects may evolve to use defensive chemicals such as feeding stimulation or defense compounds
Results: escalation arms race
Species interactions and co evolutionary races
Interactions between organisms in the physical environaml producer wonder adaptations
But physical environment isnt complex enough to produce extraordinary species diversity
Interactions with other organisms can producer unlimited diversification
Challenges and solutions are different for vertebrate herbivators
Many insects complete development on a single well defended plants - they must overcome the plants defnseces
Verbrates grazers often eat some plant tissue and then move on to another plants
Vertebrates hervatoried often select mixed diets so theyere avoiding high doses of one toxin
Some detoxification by microbes in fermentation chambers
Guts between mammals - suggest how theyre processing plants is similar
Acclimation
Early or gradual exposure to environmental stress can reduce its negative impacts
Porcelain crabs acclimated to cold temp functions better at colder temperatures
But acclimation to warm temp increases high temp tolerance only minimally
Plasticity
Plasticity to changing conditions
Student snow hares over 3 winters
Radio collared hares and performed weekly measurements of coat color and snow around
Is there enough sufficient plasticity to respond to the color of the environment
In the fall they turn white regardless of the snow on the ground
In spring there is more variation
when there was more snow in one year they waited a little
Not enough plasticity to avoid mismatches
Plasticity alone in coat color change will not be able to respond to changes in conditions
NOT ENOUGH FOR THEM TO ADAPT
Range Shifts
Species are moving polewards
Also moving up mountains but what if there run out of mountains
Pikes are in trouble when itis hot in the summer
Adaptation
Any trait that makes an organism better able to survive in environment
Evolutionary process that leads to origin and maintenance of such traits
They create variation on earth
Pikas affected by climate change?
The elevational range of american pikas in great basin is greeting smaller
Sites where pikas have gone locally extinct often hd temperatures above 26 c which can be lethal
The american pima was considered as an endangered species in US
But pikas in mountains in rocky mountains are fine
Macroevolution
Determining the evolutionary relationships in terms of common ancestry
Study long term patterns
Use comparative data - looking at many species and different sub displences
Ex molecular biology and genomics
Jean Bapitsite Lamark
First to use the term evolution
First to provide a causal mechanisms: the inheritance of acquired characters
Turned out ot be the wrong one tho
Occurred characters: idea that over a course of an individual’s life time you can accupure characters and pass them onto the next generation (girrafe thing)
Evolutionary mechaisms
Determining the particular microevolutionary processes for evolutionary change (eg natural sleetcion)
Focuses primarily on the population level
Ecpeirmeht and comparative studies the genetics and ecology of populatiosn
Two basic ideas of origin of speices
All organisms have descended with modification from common ancestors
The process of leading to adaptation isn natural selection operating on variation a,ong individuals
Darwin - Gradualism
Darwin read Lyell’s book on princicples of geology
Lyell argued that present day geological processes can explain the history of the earth - gradualism
Were not seeing giant new continents form in our life term or new species popping up
The notion of a dynamic rather than a static world emerged in Darwin’s thinking
Darwin - exploration
Darwin influenced by the botanist John S henslow at cambridge
Voyage on HMS beagle around the world as ship’s naturalist
Made numerous observations and collections of plants animals and fossils
Returned to england and spend the rest of his life in seclusion at down house developing his ideas conducting experiments and writing books
Spieces vary
Variation patterns of galapagos mocking birds
Darwin doubts fixity of species
There are similar species endemic to the islands descended from a south american mainland ancestor
Matlus influence in darwin
Emphasizing human populations cannot continue to expand exponentially
We cannot have unregulated growth forever
Events leading up to publication of The origin of Species
0 years taken up with accumulation of evidence for the theory of evolution
1844: wrote but did not publish an essay on natural selection - essay
1856: began work on natural selection book
June 1858: Received “On the tendency of varieties to depart indefinitely from the original type” by A.R. Wallace
July 1856: Linnean society presentation of Darwin-Wallace paper
1859: Publication of the “The origin of species by means of natural sleetcion or the preservation of favored races in the struggle for life”
Sold out and became popular and impactful
Why do we emphasize darwin more than wallace
Cuz of the book
why was lamarck wrong
Inheritance only by germ cells gametes; somatic cells do not function as agents of heredity
This genetics information cannot pass from soma to gametes onto the next generation
Modern interpretation genetic information flows in one direction only from DNA to protein but never in reverse
Elements of darwin’s theory
Evolution occurs primarily at the population level (indidviduals do not evolve)
Variation is not determined by the environment//is not directed
You dont adapt when u need it
3 Most fit type depends on environment
4 Survival of the fitter: evolution works with available variations but it will not achieve perfection
Implication of Darwin’s Theory
Concept of a changing universe replaced view of static world
What people thought at his time
A phenomenon with no purpose
Natural selection revealed how complex adaptations with important functions can appear through a blind, unplanned process
Evolution by natural selection
Treatment of the antibiotic gets more in with the resistant
Antibody does not cause restsistant it just selected between the resistant that was already available
Fossils
Show evolution
Earth is very old
Allows for immense amound of time for biological evolution
Slow gradual evolutionary : evluition can be occurring even if we dont see it in our life time
Intermediate forms
Evidence for common ancestors linking features of living and extinct organisms
Fossils in young increasingly resemble modern species in same region
Older starts show increasing difference
Evolutionary time points in the layers of fossiple finding
Galapgos
Clearly birds n have feathers but they dont fly
Provided darwin w the question of why a designer put feathers on an organisms that doesnt fly? But this makes sense in terms of natural selection
It descended from birds that used to flybut cant anymore but it still retained those traits
WHY DOES IT NOT FLY?
Maybe it was favoured not to fly: flying is costly
In islands teher are fewer predators and more reason to swim and catch prey so theres no reason to fly
VEstigial character
No function
ex * ear muscles, tailbone, goosebumps, appendix
EVIDENCE FOR VESTIGIAL CHARACTERS IN GENOMES
Olfactory receptor genes: allow us to smell diff types of odors
Each gene allows us to smell diff types of odors
More olfacry genes have become inactive in species that rely less on senses of smell
We have a lot of dead genes (genes w mututaion) that are in our genes cuz were not as heavily reliant on smell
Study results
Over half of our genes are not working
The common ancestor of humans, mammals, baboons etc developed trichromoatic color vision came along side losing a lot of olfactory genes cuz we weren’t heavily dependent on smell
Howler monkey indpentely evolved trichromatic color vision evolved
EVIDENCE FROM HOMOLOGY
Organism features are consistent with modification of pre-existing structures
Not expected of each organisms was individually optimally designed
Provides the evidence that were related from the similarity
Approx 500 genes share across all orms of life
Storng shared constraints for genes involved in basic cellular functions
We share the same mechanisms even with bacteria
Adaptive radiation
The evolution of ecological phenotypic diversity within a rapidly multyling lineage as a result of speciation
Orginaties from a single common ancestor
The process results in an array of many species
The species different in traits allowing expoliation of a range of habitats and resources
Three features commonly identity an adaptive ration
Recent common ancestry from a single species
Phenotype environment correlation
Rapid speciation
Evidence from biogeography
Geographically close organisms resemble each other
Different groups organisms adapt to similar environment in different parts of the world convergent evolution
Geographically isolated regions have unusual organisms
Australia
Distinct flora and fauna w high endusms (can only be found in that place) and many unique adaptations
Biological uniqueness isa result of its long history of island form other land masses
Shows lots of island characteristics
Evidence From Domestication
Vast amounts of heritable variation found within species
This variation can be selected on,leading to dramatic changes over generations
Artificial selection as the human imposed analog to natural selection in the wild
Not exactly the same design just that if there are genetic variants favored taht are better to survive and reproduce in the environment you can get rapid changes just like how when humans domesticate eplants and animals
Characteristics of mutuals
Mutuaion is an inevitable phenomenon
Despite ceeular mechanisms to correct errors during DNA replication
Mutation is not directed toward an outcome by the organism or by the environment
Not like u move to a hot environment and then change ur cells to adjust
Random respect to effects on fitness
Not summoned to make things better
Rate depends on the type of mutation
Can vary among genes
Environment can affect mutation rate
EG mytagens, high temperature
But its not directing the organism - can a role but not affecting it directly
Where does heritable variation come from?
Mutation, Degreation, recomination
Mutation and the structure of DNA
Point mutations
Changed G to a C - single nucliotoid mutation
Insertions/deletions (”indels”)
Change in repeat numbers
Chromosomal rearrangements (eg inversion)
Conclusion from medels pea expierment
1) Inheritance is determined by discrete particles
* Genes
2) Each diploid organism carries two copies of each gene
* Alleles can exhibit dominance / recessivity
3) Gametes fuse to make offspring
* Sperm / pollen with egg / ovule
* Gametes contain only one allele per gene
4) Offspring inherit one gamete from each parent at random
* One allele per gene at random from each parent
Mendels law of segration
3) Gametes fuse to make offspring
* Sperm / pollen with egg / ovule
* Gametes contain only one allele per gene
4) Offspring inherit one gamete from each parent at random
* One allele per gene at random from each parent
What generates diversity
Segregation + independent assortment of chromosomes generates diversity
Independent assortment and segregation during meiosis generates diversity
Allows different combinations of parental chromosomes
Recombination during meiosis furthers contribution to variation
Types of genotype, phenotype
Genotype: genetic consiture
Phenotype: observed traitGenome: organism’s entire DNA
Polymorphisms: common in nature
Direct correspondence between rait and its genetic basis
Easy to track selection and evolution
2 or more phenotypes
Phenotype variation in mumatls: most traits vary continuously not with discrete actegorgies
Discrete traits: Simple “Mendelian” genetics
Continuous: complex inheritance
Continuous variation and darwinian natural selection are fully consistent with mendel’s laws
Quantative factors
Quantitative traits often are affected by many factors
Complex polygenic = many gene interaches
Environmental interaction
BUT It is very hard to study quantive genetics in humans
Very difficult to control for environmental differences in humans
Simple connections between genotype and phentupe extremely unsual
Discrete variation
‘Mendelian’ genetics
* Genes of major effect, dominance and recessiveness
* Spread of alleles, change in allele frequency
Continuous variation
* Quantitative genetics
* Many genes each with alleles of small effect,
important environmental effects
* Selection response as change in average trait value
WHAT FACTORS INFLUENCE PATTERNS OF GENETIC DIVERSITY AND EVOLUTION
(1)
Mutation
Presents an increase in genetic variation
Minor one because its one base in millions but its what causes a series
Increases genetic variation
Ultimate source of genetic variation
Caused by errors during replication (Not directed)
Recombination
Working w the existing variation that exist thru mutual and creating new combinations
Random genetic drift:
Caused by random sampling effects in each varination
May not be due to genetic differences in an organism’s fitness/reproduction/survival
Smaller the population size - the stronger the affects of genetic drift
WHAT FACTORS INFLUENCE PATTERNS OF GENETIC DIVERSITY AND EVOLUTION
(2)
Natural selection:
Negative (Purifying) selection
Decreases genetic variation
Mutuals that reduce fitness are removed by natural selection
Positive (directional) selection (adaptations)
Decreases genetic variation in populations
Mutations that increase fitness will become fixed in a population
Selection favoring diversity
Increases or retains genetic variation in populations
Natural selection can act to maintain diversity over the long term (eg heterozygote advantage)
Selection should be favoring to keeping both allele around
MIgration (gene flow)
If they don’t interbreed - it doesnt affect genetic variations
Two populations taht have been somewhat isolated - two different variations in the population
Creating variation in the C allel that wasnt there before (slide pic)
Increases genetic diversity in populations
Migration influences the structuring of diversity over a large spatial scale
WHAT METRICS OF GENETIC VARIATION?
Heterozygosity (H)
Fraction of individuals that are hetergozygous averaged across gene loci
Loci: one site that were focused on (relative ex it can be a base or a large sequence)
Recall from mendelain genetics
Heterozugotes indidvials have bpth alleles
&
Polymorphism (P)
Proportion of gene loci that have 2 or more alleles in the population
A locus can be polymorphic without being heterozygous
What maintains genetic variation?
- Mutual-selection balance
Less fit types reintroduced by mutation
Followed by selection acting to remove them - Selection maintaining variation
Heterozygote advantage
Frequency-dependent selection
A rare type has a an advantage over a common type
EX pathogen - if you are a pathogen and u have a rare antigen you might be favored because they might not respond quickly
Fitness variables in space or time
All of these are under the umbrella term “balancing selection”
Classical vs balence
in notes
Moprhical cytological
Morphological
colour polymorphism
Cytological
Chormonse inversions
Looked under a microscope
Saw plenty of genetic variations
EARLY QUANTITATIVE GENETIC EVIDENCE FOR THE EXISTENCE OF GENETIC VARIATION
Rather than focus on mendelian discrete trails, focus on continuous polygenic traits
Selection experiments on different groups of organisms
Involves controlled breeding of individuals with particular trails for many generations
ARTIFICAL SELECTION
Evolutionary responses of continuous traits
Demonstrates existence of heritable variation in fitness-related phenotypes
Due to many underlying genes
RESULTS OF ARTIFICIAL SELECTION EXPERIMENTS ON QUANTITATIVE TRAITS
Selection responses demonstrate that abundant genetic variation exists for polygenic quantitative traits
But often no information on P&H as key populatio genetic traits
Also: comparative studies difficult as traits studied often are group specific
Still no solution to the question: what maintains genetic variation
enzyme polymorphism
Many loci can be examined
* Can be used in nearly any organism
* Loci co-dominant, heterozygotes can be identified
* Variation examined close to DNA level
* Provides genetic marker loci for other studies
EXTRA INFO
Mutatio-selection balance
Less fit types maintained by epatestd mutational input
Selection maintaining variation
Herterozyogote advantage
Frequency-dependet selection
Ditness varies in time or space
Selectively neutral variation
Different types do nto differ in their fitness relative to one another
New mutations neither eliminated or retained by selection
The Neutral Theory:
Negative selection rapidly eliminates
detrimental mutations
* Positive selection rapidly fixes
beneficial mutations
* The only mutations left to create
genetic variation are selectively
neutral
Reproductive system
Asexual
Making clones of themselves
Violation of mendel’s law
Sexual
Can have species w separate sexes like humans
Or hermaphrodites such as plants
Mating w others: cross-fertilization
Mating w self: self-fertilization
WHAT IS SEX? WHAT IS ASEX?
Sexual reproduction:
2 paremt contribute genetic material to offspring
Meiotic, reductive division to form gametes
Fusion of gametes
Asexual reproduction
1 parent contributes genetic material
No meitoic reductive division
Offspring are genetic replicas (conlones) of parents
THE COSTS OF SEX
Time and energy to find and attract mates (“dating cost”)
Increased energetic costs of mating
Risk of predation and infection
Cost of producing males
50% less genetic transmission
Break up of adaptive gene combinations
Segregations
BENEFITS OF SEX
The big question “The paradox of sex”
Can it overcome the costs
THE TWOFOLD COST OF MEIOSIS
Compared to asexual females, sexual females contribute only 5-% of her gene copies to the next generation
This transmission bias favors asexuals in competition with females
Should see that asexual form should be favoured
HYPOTHESES FOR THE ADVANTAGES OF SEX
Bringing together favorable mutations
Eliminating harmful mutation
Benefits of genetic variation in variable environments
“Lottery models” given environmental unpredictability
Creating all these diff combinations - like lottery tickets
Spatially heterogeneous environments
“Tangled bank hypothesis”
Temporally heterogeneous environments
“Red queen hypothesis”
Many theoretical models, but limited experimental evidence
Can be hard to distinguish and test these hyptheises
FAVORABLE COMBINATION SOF MUTATIONS BROUGHT TOGETHER MORE RAPIDLY BY SEX
Evening primrose: Multiple sexual-asexual transition
30% of Oenothera species are functionally asexual
Can we find consequences of these in their genomes?
Many independent transitions
ADVANTAGES OF SEX IN EVENING PRIMROSE: Elimination of harmful mutations
Asexual oenothera have:
More “premature” stop codon mutations
Leads to dysfunctional proteins
Higher rates of proteins sequences evolution
Implies greater accumulation of deleterious mutations
Macroevolutionry history of asexulaity
Asexuality by parthenogenesis:
* Sporadically distributed across the animal kingdom
* More common in invertebrates, rare in vertebrates
Asexuality by clonal propagation:
* Much more common in plants
* Few species (if any) are exclusively asexual
Asexual species are usually at the tips of phylogenies
* Macroevolutionary pattern indicates higher extinction rate
* Low chance of long-term evolutionary persistence
* Probably due to extremely low genetic variation & accumulation of
deleterious mutations
Mating patterns
Who mates with who, and how often?
Mates are less closely related than random
= outbreeding
Mates are more closely related than radom = inbreeding
In pratice there is a continuum between outbreeding and inbreedting
Outrcrossing
Mating w someone else
Either by outbreeding or inrbeeding
Fusion of gametes from 2 parents
Gametes derive from eiotic reductive division
Selfing (self fert;ixation)
Mating w urself
Most extreme form of inbreeding but not asexual repridction
Fusion of gametes from 1 parents
Gametes derive from meiotic reductive division
Inbreeding avoidance traits in flowering plants
Large,showy flowers attract pollinators
Timging offset between male and female reproduction
Pollen vs ovule maturation within a flower
When a male vs female flower open
Diverse morphological and physiological mechaimss to avoid selfin g
Self-icompatiablity
IN animals
Dispersal by one sex
Delayed maturation
Extra paur copulation Kin recognition and avoidance
Population genetics effect of inbreeding
Changes genotype frequencies
Increases homozygosity
Decreases heterozygosity
Does not directly change allele frequencies
Does not change polymorphism (p)
Fitness
Genetic contribution of individuals to next generation relative to others as a result of differences in viability and fertility
Darwin fitness
A relative quantity not absolute survival or offspring number
Selective Advantage:
The amount by which some individuals of a given genotype are better adapted to a given environment
Reflects relative differences in fitness
How to study Adaptation?
Monitors correlations of allele or traits with environment over space and time
Track a populations phenotype over multiple generaiosn and see if its changing
Are there changes in population that leads to evolutionary change? Is it related to any environmental change?
Analyze genomic diversity
Gene targeted by selection ought to show distinct pattens
Parts of the genome that are subjected by slectionshould show a pattern
Experimental manipulation
Differneces in environment w evolution overtime
Natural selection on Allele
Positive direction selection (adaptation)
Even tiny selection advantages can spread through populations with enough time
Gonna make the population adapt
Turns out it doesn’t even take that much time for these allele to spread
Negative purifying selection
Variation maintain selection (balancing)
Types of selection
Disruptive selection: favours Both extremes
Stablizing selection on human birth weight
Directional selection: favours one extreme
Directional selection: beak sizes on galapagos finches
As seed abundance decrease, population fell but as seeds became harder average beak size increased
Due to the drought of seeds - before seeds wre less hard but now they were harder
Disruptive selection on beak sizes in AFRICAN FINCHES
Disruptive selection leads to trait divergence
In some cases, may lead to speciation
Requires spatial heterogeneity or discrete resources
The struruggle to determine the agents of selection
Research through today shows:
Thousands of measurements of selection
Demonstrates fitness differences and evolutionary change in traits
And yet:
Many fewer convincing cases document the mechanisms agent of selection in natural populations
Linking evolution to ecology is difficult
Evolution by Pollution
Evolution of industrial melanism in peppered moths
Pepper moths
Before 1850, dark mothers were rare but as indtural population balckented tree trunks near cities, the dark variant of pepper moths replaced light forms in polluted areas
Lighter one were still in rural areas
Before1850 the allele that caused the darkness was rare
Hypothesis: Mechanism of selection due to selection by birds
Differences in moth crypsis (camouflage) depend on trunk coloration
Light form on a dark tree trunk - ur visible to predation
Experiments in the field test this
After introduction of the UK “Clean air act” in 1956
There was a decline in the frequency of the dark form
There was a lag in the revolutionary response shows the time required for foresets to return to a more natural (unpolluted state) as well as low initial frequency of the recessive allele for typical coloration
COmbined effects of selection, gene flow and genetic drift on population divergence
Gene flow: adds to homogeny
Natural selection will be acting to drive them apart
If theyre in diff environment
Drift will do the same
How to measure gene flow?
Difficult to observe and measure
Potential (dispersal ) vs actual (interbreeding)
Gamete vs individual
Even a little can affect this - youre looking for any little change
Use experimental approaches
Use neutral genetic markers
Polymorphic genetic variants that arent tagrtes of selection
Let us infer non-selective processes affecting genetic diversity of populations
Gene flow between crop and weed sunflowers
Most gene flow occurs over a short distcnace but a small amount occurs as far as 1km
Combined effects of selection, geneflow and genetic dift on population divergence
Genetic drift
Stochastic (inpredicble or random) evolutionary forces
Mutuation
Random w respect to fitness
Recombination
Shuffling genes randomly
Geneftic dift
Very much like rolling a dice
Good w mathematically modelling cuz we know propbabliyu
Deterministic (predictable or non-random) evolutionary force
Natural selection
Stochastic Processes resulting in a loss of diversity
Genetic dift
Stochastic changes in allele frequency due to random variation in fecundity and mortality - some survive some dont just by chance
Most important when populations are small
Population bottle necks:
A single sharp reduction in abudance, usually followed by rebound
Causes a loss of diversity
Founder events:
Colonization by a few indidviuals that start a new population
Colonixing group contains only limited diversity compared to the source population
Random flunctions in allele frequencies in populations of different size
Genetic dift is more prounched in small populations
More drastic flucnations each generation
More rapid loss of genetic diversity
Faster time to allel fixation or loss
Less consistency across replicate populations
Human genetic variation over space
Humans show a loss of genetic variation with increasing distance from east africa
Reflects serial founder events as humans migrated from source populations
Differences between populations within a species
Genetic differentiation among populations is often observed across a geographic range
DIfferent allel frequencies in different populations
Phenotypic differentiation may be:
Adaptive (“local adaptation”) or
Due to genetic dift or
Phenotypic plasticity
Evidence for local adaptation:
Reciprocal transplant studies
Genomic analyses
Phenotypic plasticity:
The ability of a genotype to modify its phenotype in response to changes in the environment
Occurs through modifications to growth and development and behavior
Under genetic control
Common in sedentary organisms - plants corals
Also in animal behaviour
Behaviour itself is a type of plasticity
Ohnotypic plaasticty often is an adaptation to unpredictable neivornments
But not all phenotypic plasticity results from adaption
Some of it might be maladaptive - sometimes when species evolve in enironments that they werent exposed to
Reciprocal Transplant Studies
Growth of equivalent genotypes in contriasting environments and comparisons of their relative performance
Can separate phenotypic variation into genetic and enviornmental compoents
Enables measuremnts of selection against non-local genotypes
Provides evidence of local adaptation
Tradeoffs associated with skin pigmentation
High UV radiation:
Interferes w folate
Very important vitation
May have selected for increased pigmentation
Low UV radiation
Redcued Vitiam D syntesis
Mau have selected for reduced pigmentation
No single “best” phenotype across globes due to trade-offs
Was there a history of local adaption on skin Pigmentation
Numerous genes known to affect skin pigmentation
Allele of these gens show rapid allel frequency change over time using ancient genomes (indicates natural selection)
Allele of these gens show higher between population differentiation than most other genes
Evidence supporting a history of local adaptation
Only evidence in local adaptation in humans
Diseases resistance (ex malaria)
Lactose tolerance
Natural selection associated with history of agriculture/pastoral societies
What is a species?
raditionally defined by phenotypic similarity
Fairly easy to dindetify within a region (symatric)
In one location if theres a number fo plants that look similar then youre like oh theyre the same
Symatric - look within a habitat
BUt problem arises from gradual differences across regions
Popilations can diverge from eachother - how do we deicide if theyre different around
Allopatric - different populations..? Watch video
Genetic similarity also used to identify and define species (phyologenitic species concept)
Where do you cut things out
TWO MAIN SPEICES CONCEPTS
Taxmonix (or morphkogical)
Often based on phenotype
Based on primarily on dictint measurable differences
Biological
Based on interfertility among individuals
Concepts vary amgong organisms: NO UNVIERSAL SPEICES CONCEPT
Ex bacteria dont interbreed sao we cant use this idea for them
The biological species concept (BSC)
A group fp interbreeding natural pooulations that are reproductively isolated from other such groups
If they can breed together then theyre the same
The BS Chelps frame the species problem as tractable research question
Biological species concept: points to highlight
Focuses on the PROCESS
Process of speciation in a way that we can study it
Geopgrahic isolation alone is not suffient
Just bc they live in geographic iolandt doesnt mean theyre diff speices
Isolation does not have to be obsolete
Question of what cutoff
Must be possibly interbreeding in the wild
DOes not apply well for bacteria, asexuals, highly self fertilizing species or fossils
PROF VIEW: BSC is the mots useful species oncept we have, leads to the best research on the speciation
WHERE DOES SPEICATION OCCUR?
Allopatirc speciation much more common and easier to evolve due to evolution with minimal gene flow
Symatic - same location
Reproductive isolating barriers
Pre-zygotic barriers prevent mating or fertilzation so no zygote gets formed
Geogprahical, ecological
Temporal, behavoural
Mate recognition
Mechanicals
Genutal structure compatibility
Eboltional divergnence
Cellular
Sperm-egg compatibility
PRE-ZYOGTIC ISOLATION IN APPLE MAGGOT FLIES: HABITAT AND TEMPORAL ISOLATION
Host shift from hawthorns and after arrival of domesticated apples in 1800s
Differences in timin of host planting frituing (app;e vs hawthorne)
DIfefrent timing of fly mating on preferred host plant
Reduces fly gene flow by 94% in sympatry (same region)
REPRODUCTIVE ISOLATING BARRIERS
POst-zygotic barriers prevent proper functioning of zygotes once they are formed
TAXON
taxonomic unit (taxa plural)
Kingdom, phyla, clSSES, ORDER, FAMILIES, GENERA, SPECIESS
Carolus Linnaeus
The founder of taxnoony
Binomial nomenclature
Hierarchical system of classification
Even before darwin’s day it was clear that things were more similar and diff than others
Kingdoms
Purpose of biological classification
Name is key to shared info on an organism
Predictive power
Enables interpretation of origins and evolutionary history
on tree
Terminal nodes: taxa
Terminal branches: accumulated evolutionary change
Internal nodes: common ancestors, speciation
Interbranches: accumulated evolutionary change
Molophysleyic group VS Paraphyletic
Molophysleyic group: includes the complete set of species from a common ancestor
Paraphyletic group: contains some but not all species derived from a common ancestor
Non evolutionary commonness in the pairing
Why conduct phylogenetic analys
Understand history of life
Large scale patterns ofevoltion
Understand how many times traits have evolved, how fast, underwhat conditions
Practical:
Where and when did parasites spread?
Which flu strain was most successful last year
Adaptive evolution - what are they key mutations that help these things evolve
What are the driver mutations as SARS COV-2 evolves?
Phylogenies as a forensic Record
Speices that share a more recent common anector tend to be more similar
Descent with modification
We can begin to shape evolution based on who shares what traits
In the reconstruction of phylogenetic history
got to udenifty and distinct btween ancestor and derived traits
Ancestral trait = A trait shared w common ancestor
Derived trait = A trait that differs from the ancestral trait
CONVERGENT EVOLTION
The independent evolution of structures that resemble one another and perform similar functional roles due to the shared ecology of unrelated organisms
INFERRING SPEICES RELATIONSHIPS FROM DNA SEQUENCES
Gens can be sequenced
Species can be assessed for changes in the sequence of nuelcotides
CHanges can be used to infer relationships in a branching diagram (phylogeny)
Using phylogeny to understand the origin and evolution of traits
Key innovations: origin of a novel trail resulting in adaptive radiation
Carriers of the trait can expoiut new resources or set of habits
SUsually associated with rapid evoluirontary divsersifciation (adpative raidtaions)
Diversification
Diversification = speciation - exicition
Key inncoation could increase speculation ordecrease ecteiion to ufluence
In the pic maybe the key innvolation is what lead to the thing
Why Do some groups have more species than Others
Use replicate sister groups compression
WIth one phyilogeruc comparison it is difficult to say key innviatio is involved but w more repetition then tehres more evidence
Hevibority associates with HIgher diverisiftaiui rate
Coevolution between insects and plants drives a higher rate in speciation in herbabtives
Other features associated with greater diverisuation
Secual reproduction allows us to have more genetic varion = more diversiation Outcrossing species
* Animal pollination in plants
* Increased dispersal
Major transitions in evolution:
A small number of events lead to a major changes in how inherence worked
Previously idpenitnt evolving nuts merged leading to higher level complexity and specialization through division of labor
What is the “Unit of Slection”.
Most pheotipuc traits we study in orgiams arose due to selection that increases the fitness of individuals
May of may not be good for psieces
Ex selection for color for mating but it might be bad
Inddviual selection is usually stronger than group selection
Cooperative Adpative
High relatedness
* Genes that lead to helping relatives can
spread via natural selection
2) Reciprocal altruism
* In cases where organisms repeatedly
encounter each other
* Mutual cooperation can lead to highest fitness
3) BUT: Cooperation sometimes breaks down
* E.g. selection for ‘cheaters’
GENES AS THE ULTIMATE TRAGET OF SELECTION: richard dawkins
Because genes are the unit of inheritance ultinaekty the target of selection is the gene
Selection on individual organisms is a form of copperations
Genones are composed of uenlated geens and allele that have been inherent from different places
Seergation, recomiabtion, and random mating ensures that they are mostly passed on indietely
How Do Individual Genomes Stay So Cooperative?
1) Mitosis and meiosis
* Ensures that alleles don’t compete within an individual
* Fair representation of gene variants among daughter cells
2) Development and multicellularity
* Starting from a single cell prevents initial competition
among cell lineages
3) Uniparental inheritance of organelles
* Chloroplasts and mitochondria replicate asexually
* Prevents competition within cells of different organelle
genome
BREAKDOWN OF COPPERATION: CHEATING MESOIS
MEITOIC DRIVE
If an allels can bias iys own ttanstmisson
Then it can spread to higher freuence wven while reducing individual fitness
Selfish genetic element relative to organisms fitness interests
SO IT CAN INCREASE FREUENCE OFTHE THING EVEN IF IT REDUCES INIDVIUALS FITNESS
Meiotic drive can RAPIDLY ELIMINATE alleles that have higher individual fitness
Sometines when meotic drive happens but it gets reduced by natural selection
BREAKING ANOTHER ONE OVER-REPLICATION - also cheating
Self replicating segments of DNA
THE Replication separated from cellular replicayopn
Ensure their own over representation in offspring
How do genomes not expose from transposition
Allele airing elsewhere in genome that sielce TE will be faviorusd
Mechiams controlling DNA and hsitione methylaition - probably evolved as a way of regulating
piRna and RNA interference may have evolved as silencing mechanisms
Tranpsotion
Trabsotion is a form of mutation that can dispruot a gene
ransposition increases TE abundance
* Natural selection against harmful effects
on the organism reduces abundance of
chromosome copies with most TEs
– Overall abundance results from a balance
between these opposing forces
30© BIO120 Fall 2023
mictocondia
MITOCHORIA STAY COOPERATIVE BY:
Uniparental plastid inheritance strongly reduces
competition within individuals
* Consistent with hypothesis that it evolved to
maintain cooperation
– e.g. active exclusion of sperm mitochondria at fertilization
COnflict of ntrest:
Material ingtericayion of cyptasmic genmonic
Bipertanl inherical of nulacear genome
MItochondrial mutations that enhance material fitness can spread
*even if the cost is serve to male fitness
Cytoplasmic Male Sterility in Plants
- New mutations in the mitochondria that make
hermaphroditic plants “male sterile” can spread
– “Male sterile” hermaphrodites = “female”
– Because they favour mitochondrial transmission
– Can reduce fitness of plant as a whole - Leads to evolution of nuclear ‘restorer’ alleles that
re-enable fertility through pollen
– Arms-race co-evolution of CMS & restorer genes
Cooperation of mulecullar orgaisms:
Starting from a single cell reduces competitionwithin individuals
Sepration of germline with limited numbers of cell division inhibits transmission of selfish cell lineages
Tumor supporsos, other features inhibit unregulated cell division
CANCER: selfish cell liengaes evolving within an vidual
Many features ensure that the natural selection
within an individual is limited (minimize genetic
variation within individuals)
* Ensures that many genes succeed by enhancing
the fitness of the organism (‘group’)
* BUT: countless ways to evade cooperation
* Presence of strong selection on rest of genome
(‘policing’) seems essential to maintain higher-level
cohesion!
Evoltionarily-Informed Cancer treatment>
Strong, prolonged selection pressures using the same chemothreapity drugs
trong, prolonged selection pressures
using the same chemotherapy drugs
– May not be the best solution
– Selects for resistance
* Cycling drugs, multidrug cocktails, lower
doses of drugs
– A better option?
– Ethical considerations make tests of theory
for human application challenging
Invreeding depression problems
Stagies for reduing ib pr in small cative animal specuces
FOunding indidvuauls
Ex like rhinos w only 17 left
What will allow animals to adapt before exiction
How likely is evolutionaly rescuxe
Depends on population size, beenfical mutation rate, and how much fitness was reduced - basis on model
