Evolution and Comparative Method Flashcards
How many species are currently on the planet?
8.7 million
How many species in all of Earth’s history?
1-5 billion
What is evolution?
Change in the frequencies of alleles in a population over time
What are alleles?
Gene variants
What three things drive evolution?
Mutation, natural selection, and drift
What three things do you need for evolution by natural selection?
Variation, selection, heritability
Define variation
the population contains individuals with different traits
Define selection
Individuals with cerain traits have higher chance of reproduction/survival
Define heritability
Traits are genetic
What does evolution by natural selection produce?
Adaptations
What are adaptations
A fit between the organism and its environment
What is genetic drift
A variation in the frequency of different genotypes in a small population, resulting from the chance disappearance of particular genes as individuals die or do not reproduce
Describe what mutations are like in reality
- Will immediately disappear from the population if the individual is not viable
- Some will have very small effects on survival and reproduction. The smallest advantage is important, though and will lead to change.
What is an adaptive trait
One that enhances an individual’s chance of success at survival and/or reproduction
What is the reference point for chance of survival/reproduction
It is relative to others in the population
What are adaptive explanations?
Explaining why an adaption is beneficial for an organisms survival/reproduction
What are the four ways of testing adaptive explanations?
- Compare existing variation in the population
- Treat the behavior as a “design feature”
- Create artificial variation in the population
- The comparative method
Explain the method of comparing variation in the population
Seeing whether or not organisms without a certain adaptation are susceptible to things that hinder their survival and reproduction. If so, what are these things?
What is the disadvantage to the method of comparing variation in the population
Difficult to do if natural selection has already eliminated the alternatives
Explain the treat the behavior as a design feature method
Imagining you wanted to design an animal that was optimal for surviving and reproducing in its environment given the diseases, predators, etc
Explain the method of creating artificial variation in the population
Simulating animals that dont have a certain adaptation to test if they would survive and reproduce at a smaller rate
What was the adaptive explanation for gulls throwing away their egg shells after their chicks were hatched
They used artificial variation in the population. They created artificial nests with eggs in them. Some were positioned near broken eggshells, others had no broken shells nearby.
Predators were much more likely to take eggs from nests with shells nearby than from nests with no shells nearby
What type of adaptation is eggshell removal likely to be?
Antipredatory adaptation
What is antipredatory adaptation
Reduces conspicuousness of nest
What is the comparative method
Testing your hypothesis by comparing the behavior of different species. Finding species that are closely related to the animal, but whose environment differs from the animals’ in one key way. If they dont perform or have the adaptation, this strengthens the case for your adaptive explanation explanation.
What text introduced the comparitive method?
Harvey and Pagel 1991
What does the comparitive method seek to understand
The drivers of evolutionary change and the adaptive value of specific traits
How does the comparitive method go about understanding the drivers of evolutionary change and the adaptive value of specific traits
By relating the degree to which a species displays the trait with the degree to which the hypothesized selection pressure is present
What are two important things to keep in mind with the comparative method?
The more species you compare, the better
The more you know about how those species are related, the better
What is phylogenetics
The study of the evolutionary history of species, and their relationships
What is phylogeny?
A tree that depicts phylogenetic relationships
How are phylogenetic trees reconstructed
By studying heritable traits and looking for shared characteristics
What determines how close different species are on a tree
The number of traits the species share, and how similar these traits are
What is the but when it comes to shared traits
They must be homologous, not analogous
Define homologous trait
Shared traits because they were inherited from a common ancestor
Define analogous trait
Traits that have the same function but different origins. Ex: evolved independently/convergently
What three things can we use to understand the cognitive capabilities of extinct species?
Phylogenetics
Anatomical measurements
Archaeological evidence
What can phylogenetics allow for
Inference of ancestral mental states
Give an example of how anatomical measurements can lead to understanding cognitive capabilities of ancestral species?
Cranial capacity -> brain size -> inferred cognitive “sophistication”
What can archaeological evidence provide
Traits implying the emergence of specific cognitive capacities
Insert information from slide 22 and 23
Give two examples of archaeological evidence in humans
Appearance of art - may signal appearance of abstract thinking/language
Appearance of complex stone and tools - may signal appearance of enhanced planning, teaching, communication, cooperation, division of labor, etc
Explain monkeys and tools (type monkey, type tool, timeline)
Capuchin monkeys in Brazil have been using stone tools for at least 3000 years
Chimpanzees in West Africa have been using stone tools for at least 4300 years
What does understanding behavior and cognition require
Understanding evolutionary past and present
How can behavioral and cognitive adaptations be studied
Systematically (“Why does the animal do this?”)
What can comparing species provide
Insights into selection pressures that promote the evolution of specific traits
What are Tinbergen’s 4 questions
Mechanism, ontogeny, adaptation, phylogeny
What two explanations from Tinbergen’s 4 questions were mostly talked about in this slide deck?
The ultimate ones: adaptation and phylogeny
What two explanations from Tinbergen’s 4 questions were not really talked about in this slide deck?
The proximate ones: mechanism and ontogeny
