Midterm 1 (Lectures 1-9) Flashcards
Ecology
*ON EXAM
- Derived from “oikos” (Greek) meaning ‘home’
- The scientific study of the interactions between organisms and their environment
Environment
all factors (abiotic and biotic) outside the organism that influence it
Abiotic vs biotic
Abiotic: physical and chemical
Biotic: other organisms
What is the goal of ecology? What are three other questions that can be asked?
How abiotic and biotic factors influence the distribution and abundance of organisms.
- Where are the organisms found?
- How many organisms are there?
- What do the organisms do?
In ecology, which ecological processes do we try to explain or understand?
-processes of birth, death and migration
Which are the two classes of explanation? Give an example.
*ON EXAM
- Proximal: patterns explained by the present environment
Eg. How did the weather this summer influence plant growth in the region? - Ultimate: patterns explained by the past environment (ecological experiences of ancestors through evolution)
Eg. How has the climate over the past 1000 years influenced the plant species present in the region?
As scientists, ecologists go through which process when studying ecology?
- Observe/discover
- Question
- Hypothesis
- Evaluate hypotheses by:
a. Observe/sample
b. Experimentation
c. Mathematical modeling - Inference/conclude
- Share results with public (communicate results)
Which is the 1st step for an ecologist?
Observation/discovery: discover patterns and interconnections through observation
Which is the 2nd step for an ecologist?
Question: question the pattern and interconnections that are observed
What? questions that describe patterns or relationships
How? questions whether there are causes of these patterns and relationships *proximal
Why? questions why a system functions the way it does, examines the evolutionary basis of the patterns and relationships *ultimate
Which is the 3rd step for an ecologist?
Hypothesis: develop possible answers/explanations to questions and express ideas about how a system works
Which is the 4th step for an ecologist?
Test Hypothesis: evaluate hypothesis to determine if it can be rejected
Which is the 5th step for an ecologist?
Conclusion: draw inferences about ecological processes
-high variation in nature=high uncertainty in results from statistics (based on + or - 5% uncertainty?)
Which is the 6th step for an ecologist?
Communicate results: shares results with public
Which are three different ways of testing a hypothesis?
- sampling/observational studies: descriptive studies, collect measurable features (variables) of the natural world, a natural experiment (*not manipulated)
- experimental studies: natural processes are allowed to proceed under conditions that are controlled or manipulated, experimenter must fully understand the natural history of the organism under study
- mathematical modeling: representations of nature, examine the fit of natural processes to mathematical relationships, relationships may not be exactly true (not a true correlation), model’s ability to accurately represent the essence of the relationship, models have heuristic value (may reveal unexpected patterns or serve as a guide to new discoveries)
Statistics
study and analysis of quantitative data
Why is science an iterative process?
A process for arriving at a decision or a desired result by repeating the steps. The objective is to get a result to share with the public, but doesn’t follow all the steps (may have to go back and forth).
What are the 3 levels of ecology’s hierarchy?
- individuals: interactions with their biotic and abiotic environment
- populations:
- abundance/distribution patterns of groups of organisms due to processes of birth, death, migration
- evolutionary change occurs at the population level
- interactions of organisms of the same species
- interactions of two populations of different species - communities:
- interactions of multiple populations of different species
- structure and species interactions = ecosystem ecology
Conservation ecology
blend of evolution, population, community and ecosystem ecology → apply to conservation issues
Ecosystem ecology
- structure and species interactions (in communities)
- energy, nutrient, chemical pathways
Evolutionary ecology
individuals are the units of evolution, assumes that specializations imposed by evolutionary history
Physiological ecology
individual responses to abiotic environment
Behavioural ecology
individual responses to other individuals (biotic)
Hypothesis
*ON EXAM
A prediction that can be tested.
Three ways to test a hypothesis are?
*ON EXAM
- Observation/sampling
- Experimentation
- Mathematical modeling
List five truths about evolution.
- Mutations generally do not transform an organism that is already alive
- Mutations are inherited from parents to offspring.
- Evolution does not occur on an individual basis, but by population
- Evolution typically leads to alternate not ultimate forms
- Evolution requires a selection pressure in order to occur
Population
*on exam
- *variable fitness among individuals
- a group of individuals of one species living together
- where evolutionary change is revealed
Individual
- Individuals (phenotypes) respond to selection pressures in their environment. Responses to selection pressures alter the relative contribution of individuals to future generations (fitness), through the process of natural selection
- Reservoir of genetic information
What is DNA and how does it affect an individual?
- DNA is 4 nucleotides arranged in an alpha helix
- Each individual has a unique sequence of nucleotides in their DNA
- DNA is contained in chromosomes
What are the only 4 nucleotides that are contained in the entire genetic code?
A-T
C-G
Chromosomes
- contains DNA in its structure
- come in matched pairs, one from each parent
Genes
- DNA is organized into discrete subunits called genes
- code for proteins
Locus
Particular location of a gene on a chromosome
Alleles
- two or more alternative forms of a gene
- result from slight differences in the DNA sequence of the gene
- cause slight differences in form and function
Homozygote
an individual that has the same alleles at a particular locus on the pair of chromosomes (AA, aa)
Heterozygote
- an individual that has different alleles at a particular locus on the pair of chromosomes (Aa)
- If one allele is fully expressed and the other has no noticeable effect
Dominant vs recessive allele
Dominant allele – fully expressed (A)
Recessive allele – unexpressed (a)
Who is Gregor Mendel?
- Worked with pea plants phenotypes
- Discovered genotypes
- Mendelian Inheritance
Mendelian Inheritance
- breeding of two individuals results in multiple combinations of alleles
- 1 allele present on each chromosome of a parent
- 1 chromosome (allele) is present in each gamete produced by a parent
- Gametes combine in offspring to form a new combination of alleles
- use Punnett square
- how genetic variation is maintained
Genetic recombination
all possible allele combinations from random mating of any combination of individuals in a population
Genotype vs Phenotype
*on exam
Genotype: genetic variation within species
- all genetic characteristics of an individual (set of genetic information)
- morphological, physiological and behavioural
- genetic characteristics are encoded in DNA
- Fixed during the lifetime of an individual
Phenotype: variation within genotypes
- interaction of the genotype of an individual with its environment
- outward expression of genes in the appearance/behaviour of an individual
- Responses of individuals to environment may vary
- Not Fixed during the lifetime of an individual
- Individuals with the same genotype may look different under different environmental conditions
Phenotypic plasticity
-the ability of a genotype to alter its phenotypic expression under different environmental conditions
-There are limits to phenotypic plasticity! (Responsiveness to environmental conditions)
Ex) Daphnia can only produce so much pigmentation or be transparent
When talking about phenotypic plasticity, how are phenotypic variations expressed?
- Discrete, alternative forms
- e.g. Social insects – such as bees and ants, two types of larvae hatch with essentially the same genetic material but queens are adults that reproduce and soldiers/workers are adults that defend the other larvae - Continuous variations in form (continuously varying phenotypes)
-Reaction norm = relationship between response of a continuously varying trait and environmental conditions
-e.g. Daphnia respond (pigmentation) to varying UV radiation
A)Avoid predators → transparent (no pigmentation), vulnerable to UV
B)Avoid effects of harmful UV radiation → highly pigmented, vulnerable to predators
-level of pigmentation varies continuously in response to UV radiation and predator abundance
Evolution
*on exam
- is a change in the genetic composition of a population of a species over time
- the match of individuals to their environment is a product of the successes and failures of their ancestors
- the present form and function of individuals are specializations to their environment
Adaptation
-the change in a genetically determined trait in response to environmental conditions that enhances the ability to cope with the environment
-evolutionary process that takes place in a population over many generations through natural selection
-Traits can be behavioural, physiological or morphological
Ex) fur colour in rabbits And seasonal leaf loss of trees
Fitness
*on exam
- the proportionate contribution of an individual to future generations (by reproduction)
- Responses to selection pressures alter the relative contribution of individuals to future generations (fitness), through the process of natural selection
- Number of offspring produced
- Number of offspring surviving to reproductive age
- Fitness is a relative term
- fittest individuals leave the greatest number of descendants relative to other individuals in population
What are the “Darwin Awards?”
-jokes and memes about human stupidity, resulting in probability of that individual not passing on their genetic information to offspring
Ex) man pulls tail of tiger and will probably result in their death before having any children
-natural selection takes care of stupidity
How does the colour blue in our example of fish affect evolution?
- Colour is a heritable trait
- blue is a favourable trait
- higher survival and higher reproduction
- leaves a higher proportion of descendants in next generation
Natural selection
- Operates on the individual
- Individual variation has a genetic basis → traits are inherited
- Individuals with favourable traits are more likely to reproduce; these individuals leave more descendants than others
- Favourable traits are passed on to future generations at a higher frequency
- Genetic composition of the population changes over generations or evolves
What determines if a trait is favourable?
- Selection pressures:
- Environmental conditions - abiotic factors
- Species interactions (predators, competitors) – biotic factors
- Selection pressures establish differences in fitness among individuals with different genotypes and phenotypes
What are some assumptions made when talking about natural selection?
- Individuals of a species are not identical – genetic variation
- Some of this variation is heritable
- Individuals leave different numbers of descendants – varying fitness
- Fitness depends on the interaction between an individual’s traits and its abiotic & biotic environment (The environment acts as selection pressures)
A change in the genetic composition of a population over generations is termed ________.
*on exam
Evolution
Evolution is the result of ____________ acting on a trait that allow an organism with higher _________ to produce more offspring.
*on exam
Selection pressures, fitness
Evolution operates on the __________ but the effects are seen on the _________ level.
*on exam
Individual, population
____________ operates at the individual level but ____________ is observed at the population level.
*on exam
Natural selection, evolutionary change
Explain the Hardy-Weinberg principle.
The genetic composition (allele frequencies) within a population does not change (~evolution does not occur) unless one of the following assumptions are broken:
i. No Mutations – can create an allele
ii. (Non) Random mating - among individuals in a population (certain individuals more desirable e.g. blonde individuals only mate with other blondes) *If random mating, allele frequencies will stay the same
iii. No Migrations – can add or subtract from the gene pool
iv. Small Populations – limited gene pool and mating opportunities, becomes less random
v. Natural selection – most important! Selective pressures (or changing abiotic and biotic factors)→varying fitness among individuals → favourable traits are passed on to future generations at a higher frequency → genetic composition of the population changes over time
What are the three general types of selection (selective pressures)?
*on exam
1) Stabilizing
2) Disruptive
3) Directional
What happens to frequency, fitness and average size: Stabilizing selection
Frequency: Both small and large sizes are removed from population
Fitness: Large and small sizes are produced much less than medium. (Bell curve)
Average size: Straight line indicates medium size.
Ex) sickle cell anemia
What happens to frequency, fitness and average size: Disruptive selection
Frequency: Medium size is removed since its most common.
Fitness: Bell curve is flipped since now more large and small sizes reproduce.
Average size: No medium sized offspring, mostly large and small sizes.
What happens to frequency, fitness and average size: Directional selection
Frequency: most common situation, removes largest size
Fitness: Highest fitness in small sizes
Average size: In time, the population gets smaller and smaller
How is the Peppered Moth from England evidence of natural selection?
- Survival of the moth from birds depends on being camouflaged against the tree trunk
- Two forms: light and dark
- Colour: determined by a single gene → colour reflects genetic variation among individuals
- Early 1800s – occasional dark forms, but primarily light form
- Early 1900s – dark form became more common in heavily industrialized areas. Why?
1) Soot deposited on tree trunks
2) Dark colour –more favourable
3) Genetic composition of population changed over generations; More and more of the darker colour to avoid predation from birds=higher survival and fitness
Commercial fishing is inherently selective towards harvesting larger fish. What type of selection is this?
Directional selection
Does exploitation in commercial fishing cause evolution? How was this proven in the lab and by whom? How is it similar in the wild?
- Conover & Munch studied Atlantic silverside (Menidia menidia) experiments in lab by selectively removing larger fish, selectively removed smaller fish, removed fish at random and measured fish for 4 generations.
Conclusion: mean weight of harvested fish declined over the 4 generations - Fishing pressure can significantly change the genetic composition of populations in 20-50 yrs. Size-selection is one of the primary reasons why overexploited fish populations do not recover.
Who cares? Why is commercial fishing impacting conservation of our fish?
- Smaller fish produce fewer eggs and fewer offspring
- The amount of fish available to harvest decreased over time
Biological species concept.
- Distinguish species based on their potential to interbreed and produce fertile offspring
- implies that reproductive isolation (or genetic isolation) defines a species because reproduction is the means of transferring genetic information (DNA)
How does speciation occur?
1) isolation: exchange of genes among individuals of a population (gene flow) stop, some individuals become reproductively isolated from other individuals
2) isolated subpopulation experiences different selection pressures (→different favourable traits → varying fitness)
3) genetic composition of subpopulation changes over generations (1o
via natural selection)
4) After generations, if the isolated subpopulation can no longer
interbreed with the origin population → speciation (If subpopulations can interbreed – no speciation)
Allopatric vs Sympatric Speciation
Allopatric (geographic) speciation: individuals are geographically isolated by a physical barrier (e.g. river, mountain, unsuitable habitat)
Sympatric speciation: subpopulations are isolated without geographical isolation (e.g. timing or location of breeding), *disruptive selection favours divergent phenotypes
What is a classic example of allopatric speciation?
- Darwin’s finches of the Galápagos Islands
- Couldn’t interbreed since they changed so much (physically)
- physically separated by different islands
What is a classic example of Sympatric speciation?
- the Mias and Arrow Cichlid species of Nicaragua living in small, isolated, low productivity lakes
- disruptive selection=divergent food preferences (competition) → different food and feeding habitats
- Two morphotypes=different feeding morphology, body shape
- Reproductive isolation=differences in courtship behaviour → non-random mating (premating)
- so separate species
What maintains speciation?
Speciation is maintained through reproductive isolation of the subpopulations…
Isolating mechanisms
mechanisms that restrict exchange of genes between subpopulations
What are some isolating mechanisms that allow for speciation to occur?
- Premating
– prevent mating
-Separation of mating events in space and time
-Behaviour, mechanical or structural incompatibility - Postmating
- reduced survival or reproductive success of offspring
- donkey + horse can still reproduce but offspring is a mule that is sterile
Evolutionary change occurs due to a number of agents, the most important of which is _________, as well as mutations, non-random-mating, migration and small population sizes.
*ON EXAM
Natural selection
There are three general forms of selection (selective pressures): _______, ________, and __________.
*ON EXAM
Disruptive, directional and stabilizing
The biological species concept implies reproductive isolation and speciation can involve geographic isolation (_________) or not (_________).
*On exam
Allopatric, Sympatric
Human activities _________ (can or cannot) cause species to evolve either by altering their habitat or harvesting individuals of a species.
*on exam
Can
Climate
- is the part of the physical (abiotic) environment that has the greatest impact on an organism
- long-term average pattern of weather
Weather
combination of temperature, humidity, precipitation, wind, cloudiness at a specific place and time
How are global weather patterns generated and what are the results?
- Earth’s atmosphere intercepts solar radiation
- Earth’s rotation and movement generate prevailing winds and ocean currents
- result: environmental heterogeneity
Environmental heterogeneity
variability in abiotic factors across space
Weather patterns differ at different spatial scales (climate patterns). Name them.
Global → Regional → Local → Micro (largest to smallest spatial scales)
Which two types of climate patterns determine the large-scale distribution of plants and animals?
Global and regional climate patterns determine the large-scale distribution of plants and animals.
Name the two types of habitats experienced by organisms on planet Earth.
1) aquatic environment
2) terrestrial environment
Which type of climate pattern will be our main focus for the course? Why is it relevant?
Microclimate:
- Local climatic conditions do not match the general climate profiles of the larger region
- Because local patterns of microclimate are the actual environmental conditions experienced by organisms → our focus
Why is the aquatic environment so important?
Dominant environment on Earth ~ 75 % of the planet’s surface is water
What is the microclimate variability in aquatic environments compared to terrestrial environments?
Aquatic: Low degree of microclimate variability in time and space (not as much difference in aquatic compared to land that has lots of variation in climates)
Terrestrial: High degree of microclimate variability in time and space
How is the aquatic environment separated?
Divided by salinity: saltwater (oceans) and freshwater (lakes and rivers)
Divided by depth (maximum of 11km deep in oceans - mean ocean depth =3.7km
What is the relationship between the aquatic environment and solar radiation?
Solar radiation is
- reflected back into atmosphere
- absorbed or reflected by suspended particles (alive & dead)
- absorbed by water
- solar radiation declines exponentially with depth (Distinct vertical profiles of light, temperature, oxygen, pressure, etc.)
How does light directly and indirectly impact the aquatic environment?
Direct impact: plants
○ Plants require sunlight for photosynthesis
○ Plants are restricted to top 100 m (depth, very restricted to surface)
Indirect impact: animals
○ Herbivores are restricted to depths where plants reside
For animals inhabiting deep water (further than 200m in depth) have which adaptations to survive?
i. Lack pigment
ii. Large eyes (maximum light-gathering ability)
iii. Organs that produce light (bioluminescence, produce their own light to attract other organisms)
How does temperature impact the aquatic environment?
- Exponential decline in solar radiation with depth → decline in temperature with depth
- After temperature continues to decline with depth but at a slower rate
- Some form of thermal stratification occurs in all open bodies of water
- Mixing of the water column can break down this gradient (e.g. winds, currents, seasonal)=important for organisms to survive stratification
EX) as water cools, it becomes more dense until 4oC (max density) → 4- 0 oC is less dense
- Fall: surface waters cool, become more dense, sink, creates mixing= fall turnover
- Winter: surface water less than 4 degrees, less dense, keeps cold water at surface (freeze), warm water below allows for organisms to survive the winter
Thermocline
Thermocline = region with most rapid decline in temperature
How does oxygen impact the aquatic environment?
-Oxygen diffuses from the atmosphere into aquatic environments
-Oxygen produced by plants during photosynthesis
○ Restricts high concentrations of oxygen to surface waters
○ Limits respiration and metabolic activity of animals
○ Mixing of the water column can break down this gradient
-further down you go in depth, the less oxygen is available
What is the greatest constraint on terrestrial environments?
Greatest constraint is desiccation (drying out) ~ living cells contain 75 - 95 % water
What is a major influence on evolution in terrestrial environments?
Maintaining water balance
Which abiotic component is the foundation for which all terrestrial life depends on? What are its functions?
Soil is the foundation upon which all terrestrial life depends
- Medium for plant growth
- provides vertical structure for animal life
- Controls the fate of water in terrestrial environments
- Provides habitat for decomposers (Nature’s recycling system)
- Moisture-holding capacity of the soil is critical for availability of: Water and chemical elements dissolved in soil water
What causes variation in the moisture-holding capacity of soil?
- Climate - directly influences the physical & chemical reactions in the soil & water availability through levels of precipitation in that area
- Type of parent material - material from which soil develops (Physical and chemical characteristics determine properties of soil)
- Topography -eg. Slope, level ground (more slope=less moisture it will hold)
- Aspect – north vs south-facing sites (north may experience more precipitation than south, Differ in their exposure to solar radiation/wind)
- Presence/absence & type of vegetation (Vegetation alters microclimates)
How does vegetation alter microclimates?
i. Light (via shading)
ii. Temperature (via shading)
iii. Moisture (via use)
iv. Wind movement
v. Structure – habitat for animals (Eg. Different bird species depend on vegetation of different heights)
* Vegetation provides a high diversity of microclimates for terrestrial ecosystems
_______ is the combination of temperature, precipitation, wind, etc at a specific place and time, the long term patterns of which make up a __________.
*on exam
Weather, climate
Climate can exist on different spatial scales including: \_\_\_\_\_ \_\_\_\_\_ \_\_\_\_\_ \_\_\_\_\_ *on exam
Global, regional, local, micro
Aquatic microclimates are divided by ______ and _______.
*on exam
Salinity and depth
_______ is the foundation for terrestrial life.
*on exam
Soil
The moisture-holding capacity of soil is affected by: \_\_\_\_\_\_ \_\_\_\_\_\_ \_\_\_\_\_\_ \_\_\_\_\_\_ \_\_\_\_\_\_ *on exam
1) climate
2) type of parent material
3) topography
4) aspect
5) vegetation
