Midterm Topic 3 Flashcards
What is artificial selection
- When specific animals are bread together
- Breeders have selected certain traits and bread the animals with these traits to create different dog breads
- 10 000 years of artificial selection in dog breeds
Natural vs. Artificial selection
Natural selection: Differential reproduction and survivorship among individuals within a population
- -> something is happening on the environment and only selected individuals with certain traits can survive and reproduce.
- -> Morphological traits (body parts), chemical (biochem), behavioural (psych)
- -> which traits help us to survive in our environment and reproduce
In artificial selection is does not have to do with fitness. In natural selection only the fittest survive, but in artificial selection, desirable traits are the ones selected for and it does not have to do with fitness.
Darwin in the Galapagos
Darwin’s extensive studies in the Galapagos Islands lead to his theory of natural selection, adaptation, and extinction.
-Saw a lot of variation in the morphology of the birds → some birds had larger beeck, others smaller
-The size and sharpness must be linked to the type of food found in the environment
The food is shaping the beeck
Fitness
Fitness: survival and reproduction
- Random mutations produce new alleles into a population and natural selection acts of these heritable traits, and possibly changing their frequency in a population
- Traits that confer higher fitness will increase over time and traits that confer lower fitness will decrease over time
The Key to Natural Selection
Key: Differential reproductive success because of heritable variants; everyone has ancestors, but not everyone leaves descendants
- heritable variants = differences in our genetic makeup
- the genetic makeup codes for the traits that allow animals to survive in the environment. These can be morphological traits, chemical traits and behavioural traits.
Heritability Definition
- A genetically-based trait that can be passed from parents to their offspring
- Passed down through genes from generation
Evolution Definition
- Changes in allele frequency in a population over time
- Everything is based on genes so evolution is the change in the genes (which codes for traits)
Darwins Three Conditions for Natural Selection
- Variation exists among individuals in a population in the traits they possess
There have to be difference of traits within a population (hair colour etc) - Individuals’ different traits are, at least in part, heritable
The traits have to be able to be passed on - Traits confer differences in survivorship and reproduction, a measure we call fitness
Natural Selection and Allele frequency
- Gene alleles are the basis of phenotypic traits
- Phenotype is the expression of the genotype (genes)
- Natural selection acts on heritable variation among individuals and can result in changes in allele frequencies and associated trait values in a population
- Traits that confer high fitness increase over time, while those that confer low fitness decline
Natural Selection provides 3 key answers
- Descent with modification
- -> Explain how the change occurred over time - Adaptive function
- -> What is the purpose - United all species into one grand tree of descent: including humans
- -> Human, non human animals are all the same
- -> At the time human were considered very unique and were in no way comparable to other animals (church influence)
Parent - offspring regression analysis
- Examine similarities and differences between a parent and their offspring in terms of the traits they possess
- If a trait is heritable, then that trait value should be similar between parent and offspring
Selection Experiment
-Different groups of individuals are subject to differential selection on the trait in question. If the average trait value changes in subsequent generations, the trait is heritable.
Trait Value
A trait value is where that trait stands on a scale
For example, does the animal exhibit low aggression, medium aggression or high aggression
Heritability of Exploratory behaviour - bird experiment
REFER TO GRAPH
THIS IS A PARENT OFFSPRING REGRESSION
Hypothesis: Exploratory behaviour has a genetic component
Prediction: there will be a positive correlation between a parent’s exploratory behaviour and that of it’s offspring
Methods:
- The parents were placed in an aviary with artificial wood trees (crosses)
- they recorded the number of flights and hops in the aviary in the first two minutes as an index of exploratory behaviour
- then the offspring were placed in the same aviary and their flights and hops were recorded for the first two minutes
Results:
They saw a positive correlation → how the parent expressed the trait, was the same as the way the offspring expressed the trait
Bird Experiment - Selectional Experiment
GRAPH –> v shaped graph
- They conducted a selection experiment for high and low exploratory scores of the birds.
- -> ie. high exploratory score birds were mated with high exploratory score bird, low exploratory birds were mated with low exploratory birds
- nine pairs of birds were used for breeding and the process was repeated for 4 generations
- By the fourth generation, the fast line exploratory score was over 4x that of the slow line
- Over generation you will get the two extremes
- this shows that there is a genetic component to the exploratory behaviour of birds
Why are there variations within a population (textbook)
- Variation is important in a population as changes in the environment can change the fitness of a particular trait
- Many behaviours develop because of genes and environmental effect, and even closely related individuals experience different behaviours
- Many complex behaviours require learning and so are modified by our experiences
- There might be little to no fitness variation in varying behaviours → for example where and how far the owl goes when it decides it’s time to leave has no effect on it’s fitness
- Individuals within a population typically differ in size, nutritional status, health, and other traits → with age, a bird’s vocal abilities increase as the skill of song requires both genetics and learning
Frequency dependant selection
the fitness of a trait depends on its frequency in the population relative to other phenotypes
Positive frequency dependant selection
the fitness of a phenotype increases as it becomes more common
Negative frequency dependant selection
the fitness of a phenotype increases as it becomes less common
–> this is the case in the sneaker male
Great Blue Tit experiment
- some of the birds are really aggressive towards dummy birds, and some were not
Question: Does the male aggressive affect fitness?
Methods:
- The aggressive behaviour of the males was recorded. A fake male was placed in their area and the aggressive behaviours were observed.
- To test the affect on fitness, camera’s were set up in the nests of the males.
Results: The survival rate of the offspring was pretty much the same.
The aggressive males do not bring as much food to their of spring as the non aggressive males do. However, the females picked up the slack for the more aggressive males.
How can we explain variation in a population (lecture)
- Differences in: genetic composition (gene recombination/new alleles/mutations) OR in environmental conditions
- Genetic-environment interactions
- Differences in learning
- Also possible, little to no variation in fitness over certain behaviours
→ like the birds, there were variations between the aggression but no increased fitness - The fitness of a trait may be related to frequency
- Trait differences can lead to behaviour differences
How does differential learning (3) affect variation in a population
Bee experiment
- Trial and error learning is seen in bees, increasing the rate of food delivery
- -> the learning graph is gradual as change happens over time. If it was one shot learning, the graph would go up immediately
- over time, the bees learn how to find food, and become more efficient
- there is individual variation in learning which is also connected to survivorship
- -> if they don’t learn, the wont eat and they will die
TRAIT BEING LOOKED AT; trial and error learning
Example of little to no variation in fitness over certain behaviours
Eastern screech owls show great variation in dispersal direction
When the offspring get to a certain age, they leave their home. They disperse in all directions.
There is great variation in dispersal behaviour (the trait we are studying) but it does not impact their survival and reproducibility.
The fitness of a trait may be related to frequency
The Round Goby
- In male round goby fish, there are variations in the size, colour and behaviour.
- The big male is sometimes called the parental male
- The small mall is the sneaker male
Parental male
- spends a lot of time in parental behaviour
- he establishes a territory and guards the territory to protect it for females that come along
- The big male waits for a female to come along and decide if she likes the territory → if she does, she will deposite her eggs → the male then swims over and deposits his sperm and fertilizes them. The female leaves and the male protects the eggs.
- produces more pheromones to attract the female
The sneaker male
- male produce more sperm than the parental males and also have larger testes than the parental. –> because they have to really quickly deposit the sperm and swim away. Some sperm may be deposited where there is no eggs, or eggs that are already fertilized –> larger number of sperm does not mean more fertilized eggs
- The sneaker males don’t have territories but stay close to the parental male area and when the time is right the sneaker male quickly goes into the territory of parental male and deposit their sperm.
- the sneaker males closely resemble females and there for are not easily detected as a threat by the parental male
- there are always less sneaker males in a population than parental males
-If there was a change in balance and there were more sneaker males, the system would fall apart because the sneaker males do not participate in parental behaviour. —> There will be less protection around the fertilized eggs
Parental behaviour: cleaning out bacteria, protection from predators, protecting the eggs from other males who want that territory and will kill the eggs
Why do the sneaker males continue to exist?
They are still successful but to a lower extend than the parental males which is why they both still exist
What is an adaptation
- An evolutionary process that results in a population of individuals with traits best suited to the current environment
- traits that result from natural selection are called adaptations
- A trait that enhances fitness
- A trait can be anything that the researcher is interested in studying and is asking how it affects fitness
- it is very dynamic –> depends heavily on the environment and what is happening around them
Fitness
- survival and reproduction
- surviving is great but you need to be able to pass on the alleles to other generations
Indirect indicators of fitness
- sometimes there is not enough time or resources to conduct an experiment over many generations ot see how it affects fitness, therefore, indirect indicators of fitness are used
- They include:
- -> healthy growth rate
- ->healthy body size
- -> feeding efficiency
these factors are correlated with an individual’s ability to survive and reproduce
Birds Foraging on salamanders
- Numerous species of salamanders (small, cryptic, slender) have similar polymorphisms (variations)
- ->Within each individual species, some of them had a dorsal stripe while others did not
- The researchers investigated whether frequency dependant selection as a result of bird predation
Methods:
-They made salamanders out of clay, some with stripes on their back and others without stripes
-They attached a food reward on the bottom
The models were then placed in an open area near a woodlot
-The models were in ratios of 5:45 for 6 days, then equal for one day, then 45:5, followed by a final day of equal
-The team counted how many salamanders had food on them still at the end of each day
-They found that bluejays hunted them
Results:
- After the experiment they found that the rare form, whether that be stripped or not stripped, had the survival advantage
- Therefore frequency did affect survivorship and was negative frequency dependant
Directional fitness
- individuals with one extreme (highest or lowest) trait values in a population possess the highest fitness
- because high fitness is associated with one extreme, there is a shift in that trait within a population towards that extreme
- even though there is this shift, there is still variation in the population
Donald Miles
Natural selection research at sites in Arizona’s Sonoran Desert and central New Mexico.
He studies characteristics, such as speed and strength and their relation to survival and reproduction.
Interested in how organisms are adapted to their environments and how the changing environment affects the ability of organisms to persist in a given locality.
Directional selection in juvenile ornate tree lizards
Research question: Can directional selection act on locomotor performance in juvenile ornate tree lizards? (Miles 2004)
Methods:
- Ornate tree lizards (Urosaurus ornatus)
- Captured from wild
- Tested locomotor performance of individuals on 2m raceway
- Measured body size and mass
- Uniquely marked individuals and released back into wild & Recorded survival for 6 months
Some variables measured: Snout to vent length Burst velocity Mean velocity Stride length **do we need to know more specific??
Results: lizard population are quickly becoming extinct around the world. Only the extremes were surviving. The graph was an example of disruptional selection
Side note: noticed that changes in temp (particularly when it was too hot), would resulting the lizards not going out to hunt and therefore starving and dying
Directional selection lizard example textbook
Experiment of lizards
Found that larger, heavier individuals had higher survivorship
Also found that those with higher mean velocity, higher burst velocity and longer stride length had higher survivorship
Larger size tends to correlate with faster movement
But which is more important
Using a regression analysis it was determined that locomotor performance was more important than body length in affecting survival
Locomotor performance is a function of stride length
Therefore he concluded that there was a strong directional selection on limb length in juveniles: longer limbs produce longer strides allowing the individual to achieve greater velocity and in turn enhance survivorship
Disruptive selection
- a situation where individuals with either of the two extreme (highest or lowest) trait values will have the highest fitness
- over a period of time, there is an increase in frequency of both the extreme traits
Example of disruptive selection textbook
Within a single pond of spadefoot tadpole, there are a lot of variations in feeding morphology and behavior Some individuals (omnivore morphs) feed mostly on the detritus (decomposing organic materials) and they have rounder bodies with smooth mouthparts and small jaw muscles The other individuals (carnivore morphs) also consume invertebrates and have elongated bodies, notched mouth parts, and large jaw muscles Then there is an intermediate that has the morphology of both 2 predictions were made: Omniv. Would feed more efficiently than intermediate on detritus and carni. would feed more efficiently than intermediate on invertebrate Omni. and carni. Would have higher fitness than intermediate Researchers examined feeding efficiency and force tadpoles to consume only one food type. Measured the size change (ie. growth rate) The also would place the carni. and intermediate tadpoles in a chamber alone with 10 fairy shrimp and timed how long it took for them to capture and eat the shrimp To test the second prediction, they marked 500 tadpoles one of the three morphs. 8 days later they collected 1500 tadpoles and counted the number of each marked one as well as the morph of 301 unmarked ones The researchers found that the feeding performance of the specialized morphs were higher than the intermediate and the intermediate morph had a lower fitness than the two other morphs Both predictions were supported
Stabilizing Selection
- those individuals with intermediate trait values will have the highest fitness
- over time there is an increase in frequency of the intermediate trait
Stabilizing selection example textbook
Individuals with intermediate traits have the highest fitness
Ex. defending a territory requires a lot of energy
Convict cichlids are aquarium fish that will individually defend small territories and feed on a variety of food including invertebrates, small fish, plants, algae.
In the experiment, there was a single food patch that could be defended (food patch was of varying size in the different tanks)
He measures how much food the dominant fish ate, the number of intruders it chased away and its growth rate.
Growth rate = fitness for this experiment
A dominant fish was placed inside and 4 subordinate fish were also placed
Found that there was reduced fitness it the fish that guarded a large area and a small area
The ones that defended small areas had less food to eat
The ones that defended large areas had to expend more energy
Individuals that guarded intermediate sized areas had more to eat and grew faster, but spent less time and energy chasing away the intruders.
Optimal trait
The trait value that confers the highest fitness
Cost benefit approach
A method used to study behavioural adaptations in which the fitness benefits and costs of different traits are examined to determine which has the highest net benefit (benefit - cost)
The simplest cost benefit approach predicts that a behaviour that maximizes fitness, irrespective of how other animals behave, will continue to be passed down
However in many cases, the fitness of a behaviour depends on how others behave
keep in mind there is no 100% trait that will make you 100% optimal
Game theory
A cost benefit model that says an individual’s fitness is affected by the behaviours of others
Game theory is used to predict the proportion of each behaviour that one should observe in a population
evolutionary stable strategy (ESS)
The solution to biological games This strategy (a single behavior or multiple behaviors observed in different portions of the population) cannot be beaten by any alternative strategy and no player will adopt a different strategy because doing so will result in lower payoff. → a strategy that if adopted by a population cannot be invaded by another strategy because it yields the highest fitness
Cooperation in chimp video
Chimps ask for human help when they need it and the chimps will also help the humans
In the video, the chimps didn’t help each other but did help humans
Helping others to survive and reproduce
Cooperation may happen between species that aren’t related
Do organisms behave well towards each other for the good of the groups and the survival of the species?
Do animals have a sense of fairness video
One monkey has the rock, the other has the food
The monkey passes over the rock needed to open the food bin
The monkey 2 opens the food and shares it with monkey 1
Monkeys learn that white chips can be traded for food
Monkey 1 gets a dry chip for the chip, while monkey 2 gets a grape
Monkey 1 catches on that he is getting shafted and tries to get a grape
These monkeys don’t know if they are related. Smarter animals with highly developed social brains develop other strategies
They display tit for tat strategies
This shows how animals can cooperate even if they don’t know if they are related
Questions, is cooperation for the individual or group
Group Selection
a selection that favours particular groups of individuals over other such groups
→ if all individuals attempted to maximize fitness by reproducing, the resources would be over exploited, leading to extinction
There were flaws with group selection
This idea was by Wynne Edwards
Bill Hamilton
Bill Hamilton noticed that the majority of the individuals that are cooperating, tend to be related and therefore have identical copies of some of the genes
Cooperation is actually at the level of the gene not at the group
If the relationship between the two are high, then there are more identical copies of the genes
The higher the relatedness, the higher the cooperation
There is little cooperation for food sharing
Says cooperation can be explained by direct fitness and indirect fitness
Direct fitness and indirect fitness
Direct fitness: number of offspring produced by the individual, how many gene copies did that individual leave themselves
Indirect fitness: the amount of offspring close relative have. Close relatives have similar genes to you and therefore can increase your own fitness as well
Inclusive fitness
Indirect + Direct = Inclusive Fitness
Kin selection
Individuals can increase their fitness by helping close relatives
These seems to be favouring how an individual seems to be thinking about maximizing fitness
At what levels is cooperation happening at?
It looks like it is happening at the organism level however it is actually happening at the gene level
Sexual Selection
A type of natural selection that acts on heritable traits which affect reproduction
Acts on heritable traits but only those that affect reproduction
Sexual Dimorphism
Are morphological trait differences between the sexes.
Eg
Male birds are more colourful than female birds
There are a lot of choice of what we consider attractive → what is attractive is generally considered sexually dimorphic traits
Intersexual Selection
inter = between
Between the sexes
Has to do with mate choice
There is selection happening between the sexes
What do the females find attractive in males
Females do more of the choosing in general and males do more of the competing
Intrasexual Selection
within
Males fighting with each other, showing aggressive tendencies
Traits that allow for 2 males to compete with one another to gain access to the female
Sexual Selection example (textbook)
Male widowbirds perform a dance for females and display their tail. Females may visit many males before selecting one to mate with, build a nest with and raise offspring with
Multiple females can breed in a single male territory
In an experiment it was seen that females preferred the males with longest tails, and didn’t have much to do with tail colour and territory
Long tails are energetically costly, but they help to reproduce
Sexual Selection in House Finches
Research question: Is the red colouration on male house finches a result of sexual selection? (Hill 1990)
Hypothesis: Red is a sexually selected trait in males
Prediction: Females will prefer males with the most intense red colouration
Methods:
Experiment 1
Quantified male plumage colour intensity
Allowed females to choose among males
Measured how red is a particular set of feathers on the male, then allowed the females to chose
Experiment 2
Artificially dyed males Allowed females to choose among males
Results: in both the natural and manipulated experiment, the brighter red colour is preferred
Conclusion: Red is a sexually selected trait
A third experiment was performed
Bunch of females together, who is spending more time with who
Bunch of females placed together and some hoped over and spend more times with others
Females all have very low colour feathuration
Some females are still preferred BY other females
Sometimes individuals are preferred just because
Yes red is the preferred colours but no data is 100% clean
