Cycle 11 - Evolutionary Ecology Flashcards
Outline the various types of species/population interactions
Define co-evolution
Co-evolution: occurs when genetically based, reciprocal adaptation occurs in two or more interacting species
Explain commensalism
Commensalism
- One species benefits from and the other is unaffected by the interactions
- Rare in nature because few species are unaffected by the interactions of others
- Ex., oxpeckers eat organisms off hosts and do not cause harm to the host
Explain mutualism
Mutualism
- Both partners benefit
- Common
- Ex., co-evolved relationships between flowering plants and animal pollinators
Explain parasitism
What are the types of parasites?
Parasitism
- One species benefits and harms the host
- Differ from predators because they do not directly kill their prey
- Ex., vampire bats are parasites because their sole means of survival depends on obtaining blood from their host
Endoparasites (tapeworms, flukes, roundworms) live within the host
Ectoparasites (leeches, mosquitoes) feed on the exterior of the host
Explain why close mutualisms can be risky
Mutualism can place species on the edge of survival –> extinction of one must lead to change or the extinction of both if said species was only source of survival)
Explain factors that provide an advantage in the evolutionary arms race
- Generation time: affects how rapidly one party can evolve
- Ex., rapid antibiotic resistance
- Larger population size: likelihood that they will stumble across some sort of beneficial mutation
- I.e., anything that gives a high mutation rate/fast rate of evolution
Define the ‘life-dinner principle’
Prey-predator relationship: prey is running for its life while predator is running for dinner
Selection is stronger on prey because it only has one chance to survive the encounter; predator won’t die if it misses one meal
What is the prudent parasite hypothesis?
Prudent-parasite hypothesis: parasite should always minimize virulence
- Virulence decreases over evolutionary time
- Parasites hat are highly virulent have probably only recently jumped to a new host
What is the trade-off hypothesis?
Trade-off hypothesis: parasites balance costs/benefits of virulence
- High virulence reduces survivorship of current host, but may enhance transmission to new hosts
- Optimal virulence can depend on transmission mode and ecology of parasite/host
Compare ultimate and proximate explanations
Ultimate explanation: appeals to evolutionary origins and to the previous selection pressures that may have caused the trait to increase in frequency over time (ex., bird is singing because over evolutionary time, male birds that sang a lot were better able to attract mates)
Proximate explanations: proximate explanations have to do with the biochemical and physiological underpinnings of a trait (ex., bird sings because of hormones, because it is happy/angry)
Explain ways in which disease symptoms may represent adaptations by the host or by the parasite
Adaptations by host:
- Some symptoms help us expel the parasite, eg, coughing, vomiting
- Fever helps kill bacteria by raising body temperature
- Anemic people → low blood iron levels prevents some bacteria from replicating
Adaptations by parasite:
- Runny nose and sneezing increase parasite’s ability to jump to new host
- Stomach and intestinal upset causes diarrhea, which makes it easier for parasite to spread via water supply
Expain why selection does not necessarily improve health and wellness over time
- Selection only acts to improve fitness - the ability to pass on one’s genes
- Doesn’t act to maximize health and well-being
- There is always a trade-off
Explain the ways in which humans’ current environment differs from our ancestral environment, and how this may affect human health
- Higher access to food resources → increased lifetime number of menstrual cycles
- Increased population density and social group size → easier for diseases to spread → parasites become more virulent
- Better personal hygiene, clean water → decreased risk of infectious diseases, eg. mumps, tuberculosis, hepatitis A, but increased risk of autoimmune disorders, eg. multiple sclerosis, type 1 diabetes, asthma
What is antagonisitc pleoitropy?
Antagonistic pleiotropy: a trait or allele increases one aspect of fitness, but decreases another aspect of fitness
These harmful traits are likely maintained through heterozygote advantage
Ex., sickle-cell anemia vs. malaria
Explain why traits that reduce survival very late in life are not likely to be strongly selected against
- Not everyone survives to old age
- So, selection is much stronger on fitness that increases survivability earlier in life than alter in life, even if they reduce longevity
- Traits that reduce late-life fitness but have no effect on early-life are selected against, but only weakly (not many ancestors made it to a late age)
Explain the arguments that humans are no longer evolving
Selection
- Minimal selection pressures
- Getting better at protecting ourselves from illness
- Low famine in western world
Genetic drift vs. gene flow
- More interbreeding from different geographical areas
Genetic drift not very powerful
- Becomes less and less important as technological travel increases
Mutation
- Genetic screening to correct potentially harmful mutations
What is a selective sweep?
Selective sweep: when a favourable new mutation increases in frequency, adjacent stretches of DNA come along for the ride (hitch-hiking)
Through this analysis, it has been found that there has been a recent acceleration of human adaptive evolution since the last 30 or 40,000 years
Give some examples of recent human adaptation
Examples of recent human adaptation:
- Adaptations to new food sources (ex. amylase, lactase persistence)
- Adaptations to new environments (ex. oxygen transport in high-altitude populations; pale skin in high-latitude populations)
- Adaptations to parasites (immune receptors)
- Brain size and language (ASPM and FOXP2 genes)
Explain the utility hypothesis of brain size
Utility hypothesis: language, tool use, and planning lead to survival and thus increased fitness
- Ex., an individual is smart enough to create a throwing axe to kill more animals –> more food –> increased fitness
Explain the mind-mating hypothesis of brain size
Mating-mind hypothesis: art, wordplay, humour and music lead to mating success and thus increased fitness
- Note: sexually selected traits like these are usually sexually dimorphic (i.e. restricted to one sex), but they are found in both sexes because modern humans are monogamous –> both sexes are choosy)
