Lecture 1 + 2 Flashcards
Ecological phenomena can occur at a range of
- biological scales
- spatial scales
- temporal scales
- all of the above
All of the above
Generally, most studies will evaluate a hypothesis based on whether the p-value is
p < 0.05
___ are functioning groups of individual organisms of the same species in a defined location
Populations
The principal sources and approaches used to gather ecological evidence include ___
Observations, experiments, and mathematical models
Sluggish oceans’ circulation cause in part by melting of Greenland and Arctic Ocean ice. Consequences?
Faster build-up of CO2 in the atmosphere
Greater weather extremes (cold, heat, floods, droughts)
May become far worse
Ice Loss and Polar Vortex
The loss of sea ice may be worsening the polar vortex, allowing cold blasts the dip south from the Arctic
Ecology is a science
Hypothesis generation and testing
Testing through models, observations, and experiments
Science is a process for gaining new knowledge, for improving understanding. NOT a list of facts or theories.
Ecology is not Environmentalism
Ecology: scientific study of the interactions of organisms and their environment; a field of biological science
Environmentalism: concern for and action toward protecting the environment; a social movement
Ecological science can feed into environmentalism
Scientists have an ethical responsibility to share their knowledge with the public (shale gas, methane, and global warming)
Hierarchical scales of organization in ecology
- biosphere
- ecosystem
- community
- population
- organism
- organs and tissues
- cells
- organelles
- molecules
Population
Groups of organisms of the same species in a defined area
Communities
All of the populations (different species) in a defined area
Ecosystems
Community of organisms AND the physical environment in a defined area
Biosphere
All life interacting with the physical environment at the scale of the entire planet
Properties observed at a particular level of organization arise out of the functioning of the parts at lower levels
cells -> organs
communities -> ecosystems
Important to look at lower levels, but we can often predict and understand behaviour at one level of organization without fully understanding the functioning at lower levels
ex. Boyle’s Law (1662) for gases:
pressure * volume = constant
understanding of this based on quantum mechanics at the level of individual gas molecules not developed until 250+ years later
similarly, we can predict the consequences of adding nutrients to a lake (ecosystem) without fully understanding the functioning of algal populations
Does the nitrogen added to an ecosystem from the atmosphere (in acid rain) affect biodiversity? How might scientists (ecologists) test the hypothesis that yes, adding more nitrogen changes diversity?
Observations: compare biodiversity across ecosystems that are similar except in terms of how much nitrogen inputs they get from the atmosphere
Experiments: add nitrogen and see how the ecosystem responds
Experiment: adding nitrogen to grassland plots at different levels
Much less “noise” or variation in the pattern, compared to observational data.
But hard to know if the effect is consistent across sites with different climate, soil types, etc.
Ecologists have the greatest confidence in understanding relationships when ___
observational data agree with experimental data
Experimental Lakes Area
An experiment, but with no replication. Instead, comparison to a reference lake that received no acid.
Effects of acid observed at far higher pH’s (less acid) than had been predicted from lab studies of populations of fish.
Lake trout in a reference lake receiving no acid are healthy.
Lake trout in the acidified lake are clearly underweight in the years before they are finally gone.
When evaluating case studies in ecology, it is important to keep in mind:
- phenomenon occur at a variety of scales
- data and evidence can come from a variety of sources
- scientific evidence is necessary
- all of the above
- none of the above
All of the above
Which field of ecology studies trends and fluctuations in the number of individuals of a particular species at a particular time and place as a result of birth and death rates?
- Community ecology
- Systems ecology
- Ecosystem ecology
- Population ecology
Population ecology
A researcher is studying how the physiology of individual single-celled organisms of the same species. This is an example of studying ecology at what level?
- organismal
- population
- ecosystem
- community
Organismal
Which approaches can ecologists use to answer research questions?
- mathematical models
- controlled laboratory experiments
- manipulative field experiments
- observational data
Say you go and measure the diameter of trees in old growth forests throughout 30 plots of land in Argentina. You want to know if tree size differs between sites. This is an example of what type of study?
Comparative field observation study
You design an experiment to test how ultraviolet radiation impacts the development of a species of frog tadpoles. You set up your experiment so that there are 50 replicates, instead of only 10. Why is it a good idea to have so many replicates?
The more replicates you have the greater the likelihood of obtaining accurate results
You compile a model to test how dissolved carbon dioxide levels are affecting calcium deposition in the Pacific Ocean as a result of climate change. Your model indicates that many species relying on carbonate for shell deposition will not be able to survive due to the projected future changes in dissolved carbon dioxide levels as a result of climate change. What is the likely conclusion to draw from this result?
Your model is only a prediction and can be applied cautiously to help land managers and other researchers
One researcher studies plant cells and how these cells and plants respond to increased concentrations of carbon dioxide. Another researcher studies how multiple species interact and what affects their abundances and distributions. A different researcher studies a species’ DNA and what changes have occurred between populations as a result of evolution. What do these researchers all have in common?
- They all study community ecology since each researcher is interested in what happens within communities
- They are all interested predator-prey interactions
- They all study one of the many levels of biology with some application to ecology
- They all study organismal biology since each researcher only studies the response of single-celled organisms
They all study one of the many levels of biology with some application to ecology
Which of the following is NOT important to remember when collecting data?
- Estimate accurately and without bias
- Be as precise as possible
- Fabricate data if necessary
- Effectively use the time, money and human effort that has been invested
Fabricate data if necessary
Which two scientists derived the theory of evolution by means of natural selection?
Charles Darwin and Alfred Russel Wallace
Which scientist devised an orderly system for naming different organisms?
Carl Linnaeus
Which term refers to a trait that has a genetic basis and is capable of being passed down to subsequent generations?
Heritable
Peppered moths (Biston betularia) vary in color from place to place. Is the variation within these populations heritable?
- No, variation within this species is not heritable
- Yes, the trait is the same in all populations which allows any moth to change from white to black at any given time
- Yes, this trait is heritable and is selected for or against depending on the environment
- No, variation is not heritable because reproduction does determine the color morph.
Yes this trait is heritable and is selected for or against depending on the environment
Changes in temperature in the North Sea over the past million years caused changes in sea level that:
- Prevented the dispersal of animals and plants between land masses
- Caused almost all animals to go extinct
- Allowed for dispersal of both plants and animals between land masses
- None of the above
Allowed for dispersal of both plants and animals between land masses
What type of evolution is described as the process whereby organisms that do not share a recent common ancestor evolve similar traits as a result of having to adapt to similar environments or ecological niches?
Convergent evolution
Evolution
Genetic change in a population over time
Evolution (a genetic change) can be occurring if there is
- genetic drift (random)
- gene flow
- sexual selection
- mutations
- natural selection (some individuals are more fit)
Natural selection and fitness
Fitness is measured by reproductive success
Survival is important because it enables reproduction
Assertions for evolution by natural selection
- Excess of individuals, intraspecific competition
- Variation in phenotypes
- Heritability of phenotypes
- Phenotype correlated with fitness
Microevolution
Small scale changes
Macroevolution (speciation)
Evolution of new species
- over time we can get very large changes in populations of organisms
- if 2 populations are genetically isolated and change enough (such that they can’t produce offspring), they are different species
- Excess of individuals and intraspecific competition graph
Graph (time v. #): low population (happy – low competition); exponentially growing population (meh); slowing down logarithmically (sad – high competition)
- Excess of individuals and intraspecific competition importance
- reproductive potential exceeds environment
- there is intraspecific competition between individuals
- individuals are ultimately competing to have the highest fitness
-> some individuals have long lives, some short
-> some individuals reproduce a lot, some not at all
- Variation in phenotypes
- a phenotype is a measurable quality of an organism
- variation in phenotypes means that individuals are different
- important because individuals are different
- natural selection requires variation
- Variation in phenotypes graph
ex. running speed v. # of proto-cheetahs; inverted bell curve
-> most individuals will be average
High heritability
Offspring resemble their parents due to genetics
Low heritability
Offspring do not resemble their parents
- Heritability of phenotype graph and importance
ex. mid-parent speed v. offspring speed -> linear increasing slope (if parents are fast, offspring are likely to be fast)
- offspring will resemble their parents because of shared genetics
Factors that contribute to a phenotype
Genetics
Environment
Heritability
- phenotype is a function of genetics and the environment
P = G + E + (G*E) - think about human height
- “nature vs. nurture”
- only heritable phenotypes can evolve due to evolution by natural selection
- traits determined by the environment do not evolve due to evolution by natural selection
-> no genetic change
- Phenotype correlated with fitness graph and importance
ex. running speed v. individual’s fitness: linear increasing slope
- individuals with a certain phenotype may be more fit!
How will the distribution of proto-cheetah running speeds change over thousands of years?
The inverted bell curve squeeze inwards, so more cheetahs are faster
Natural selection
Differential fitness of genotypes; related to factors in the environment
- when a phenotype has a variation with a genetic basis and some phenotypes are more fit, those phenotypes will become more common in the population
Evolutionary adaptation
Specific phenotypic traits that have evolved due to natural selection
- many different traits follow a cheetah type story
- natural selection can lead to cool phenotypes
Natural selection and society
- pesticides
- herbicides
- antibiotics
- COVID
- changes in urban populations
- evolutionary responses to global warming
- more
Other issues
- evolutionary arms race (co-evolution)
- fixed traits (limit to a trait ex. limit to cheetah speed)
- mutations (mutate to even faster speed)
- trade-offs (and stabilizing selection)
Stabilizing selection
A form of natural selection wherein individuals with moderate or average phenotypes are more fit
Disruptive selection
Favouring individuals with extreme phenotype
The change, over time, in the heritable characteristics (genetics) of a population of species is known as _______?
Evolution
The term _______ refers to the genetic contribution (often times measured as number of offspring) that an individual contributes to the next generation.
Fitness
A male bullfrog (Rana catesbeianus) is found to mate with more females and produce more offspring than any other male in a pond being studied. What would you say about this bullfrog’s fitness?
- This males fitness is low compared to all other males in the pond
- This males fitness is intermediate compared to other males in the pond
- This males fitness is the highest of all other males sampled in the pond
- This male must have the loudest vocalization and be most aggressive
This males fitness is the highest of all other males sampled in the pond
The theory of evolution by means of natural selection relies on what established assertions?
- Variation is heritable
- There is differential reproductive success
- Individuals of a population of species are not identical
- All individuals are favoured by natural selection
Variation is heritable
There is differential reproductive success
Individuals of a population of species are not identical
You and your friend are walking on the Cornell campus and you notice two different flower beds. The flowers in one of the flower beds are very bright red, while the flowers in the other flower bed are a pale red. Your friend says to you, “the difference in color is due to genetic differences between the flowers in each bed.” What should you say to your friend?
- “That is a great observation. Flower colour is genetically controlled and so the flowers are different.”
- “That is not the case, the bright red flowers are probably brighter because there is more fertilizer in the one of the flower beds.”
- “That is possible. However, we cannot rule out that the flowers are different colours due to an environmental factor.”
- “That is an interesting observation. The difference in flower colour is probably due to a mutation that occurred in each individual flower in one of the flower beds.”
“That is possible. However, we cannot rule out that the flowers are different colours due to an environmental factor.”
Many phenotypes are a function of genetics and the environment. So, you can not be sure which factor is more important for the flower colour phenotype.
Male deer compete for mates by fighting with their antlers. The male deer with the largest antlers tend to secure the most mates. Why do we not see a large number of male deer with super large antlers?
- Directional selection drives antler size to phenotypic extremes
- There are also negative aspects to having large antlers, so stabilizing selection favours an average antler size
- Disruptive selection results in the intermediate antler size being the most common
There are also negative aspects to having large antlers, so stabilizing selection favours an average antler size.
We often find trade-offs in ecology. For example large antlers might help to secure mating events, but they also come with costs such as the energy to build the antlers and the ability to move etc.
You learn that many plants are chemically defended and that herbivorous predators have developed resistance to many of these plant defenses. However, it appears that plants have responded to herbivore resistance by producing more chemical defenses, which in turn deters some herbivores. Evidently, this process has occurred many times over the last millions of years. This is an example of:
Co-evolution
“When the cheetahs evolve to run faster what happens to the gazelles?”
Since the peak of the last glaciation, global temperatures have risen by about 8 degrees Celsius. Pollen records indicate:
- All flora have responded the same by expanding their range
- Some tree species have retreated their range
- Some tree species have expanded their range
- That trees were not expanding or contracting their range
Some tree species have retreated their range
Some tree species have expanded their range
Speciation is ________.
A gradual process that happens over evolutionary time
ex. Think of the example with cheetahs on islands
A seismic event occurs, splitting a population of wolves in two. One half of the population is now exposed to a very mountainous and rocky habitat with much snow, while the other half of the population is left to live in a wooded forest habitat. After thousands of generations, another seismic event occurs and the population of wolves is now able to be one again. However, they will no longer mate with one another. This is an example of:
Allopatric speciation
Think of the example with cheetahs on islands
Two populations of deer are found in a mountainous habitat. These two populations look very similar. Also, there is observed mating between them that results in viable offspring. Have these two populations have diverged into two species?
- Yes, they have been separated by mountain barriers and their is no exchange of genetic material
- Yes, because the two populations are allopatric
- No, because the two populations are sympatric
- No, because there is observed mating between them that results in viable offspring
No, because there is observed mating between them that results in viable offspring
