Final Exam: Evolution and Ecology Flashcards
Great Chain of Being
aka scala naturae; an idea of a universal hiercharchy
metaphysical concept with gods tiered at the top, humans in the middle, and animals underneath
Nicholas Steno
- studied genealogy from theological point of view
- Provided insight into fossil record: “tongue stones” were sharks teeth, realizes that it must’ve represented something that lived and died
- Law of Superposition: lower levels of stratification are older than upper layers
Age of Discovery
Age of the Earth: Ussher
Age of Discovery happened in 15-17th century.
Age of the Earth: Ussher used Bible to say that Oct 6, 4004 BC, 9:00AM was the start of the Earth.
Darwin thought that the age of the Earth that people thought at the time was too young; ppl thought it was 6000 years old
Natural Theology
- Carl Linneaus
school of thought to prove the existence of God and divine purpose through observation of nature and the use of human reason; not dependent on revelations
Carl Linnaeus: created system of binomial nomenclature in Latin; transcended scientific category for all languages → now called taxonomy: inventory of life
Argument from Design
William Paley: organisms exist and function well therefore they were created by a being of high intelligence
Watch example: if you go outside and find a watch, you would think that someone had made it because it functions well; same with organisms
Adaptation vs Gradualism
ADAPTATION: form fits function
Bird beak example: osprey, tern, yellowlegs, loon, gull, night-heron, etc.
GRADUALISM: James Hutton; earth changes slowly but incrementally, thereby creating large changes with time
e.g. Grand Canyon
Extinction
Georges Cuvier: realized that some species die off without branching out to other forms of life
Jean Lamarck – Lamarckism (2)
no longer true
Principle of use and disuse: parts of an organism’s body that are used become more developed; parts that are not used become smaller and may disappear
Inheritance of acquired characteristics (mechanism of evolution): Changes achieved over an organism’s lifetime are passed on to its offspring
Uniformitarianism
Charles Lyell: says that we can’t assume anything that we can’t see, therefore he pushed for concrete evidence to prove theories; follows Hutton’s gradualism
Current laws of nature is the same as laws of nature in the past → Pushing theological ideas out of evolutionary biology (no miracles)
Alexander von Humboldt
Climbed Chimborazo volcano (S. Am) and recorded plants, discovered biological changes in altitude → origins of modern ecology / biogeography thru looking at the distribution of plants and animals across geographic zones / climates
Charles Darwin – HMS Beagle
five year contract; discovered many things; read Lyell and Humboldt; collected fossils and specimens through hunting expeditions; saw world in comparison framework
Charles Darwin – Law of Succession of Types
finding that living species generally resembled fossil forms of species from their same location
Charles Darwin – Galapagos Islands
endemic fauna; volcanically created chain of islands that was a good distance from South American coastline, preventing most species from traversing the coast; created an insular habitat and exclusive species with differences in form and behavior
Charles Darwin – Subsidence of Land Hypothesis
refers to the creation of coral atolls (eg. Mo’ orea in the Southern Pacific)
coral grows upward and outwards as the inner island disappears → Volcanic island - fringing reef - barrier reef - coral atoll
Morphological convergence
observed similarities across species in similar but distant environments
e.g. sugar glider and flying squirrel
Alfred Russel Wallace
unsung hero who collected specimen in the Amazon and worked with Darwin that came up with same ideas but in a different area; working class naturalist who published The Geographical Distribution of Animals
Charles Darwin – Pattern of Evolution
continuous, slow, gradual; change by “insensible degrees”
E. g. Darwinian giraffes: natural selection favors longer neck (better chance to get higher
Fecundity
large amount of offspring but only a few survive → AKA surplus production of offspring
e.g. pomegranate seeds, fish eggs
Individual Variation vs. Inheritance
INDIVIDUAL VARIATION: Genetic differences that are usually heritable; lead them to survive better in the wild (natural selection) or be chosen for animal husbandry (artificial selection)
INHERITANCE: Preservation of favored traits thru process of genetic transmission of characteristics from parent or ancestor to offspring
leads to differential survival / reproduction with successful traits as heritable and preserved due to the characteristics of nature → “Struggles for existence”
Explanatory power (6) A > C > H > V > E > F
used to support the pattern of evolution as proposed by Darwin
- Analogy: similarity of function and superficial resemblance of structures that have different origins e.g. wings in different organisms
- Convergence: organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches
- Homology: shared descent from a common ancestor
Same organ in diff. Creatures
Ex: tail in whale and human - Vestigial structures: rudimentary organs
- Embryology
- Fossil record
“Difficulties on theory”
Missing links: fossil record does not show a continuous stream of evolution; there are chunks of species missing
That’s because organisms are very hard to preserve, we have a poor geological record that does not capture changes by insensible degrees; other factors: erosion, haven’t found them yet
Includes Ussher, organs of extreme perfection, and blending inheritance
Organs of extreme perfection
Evolution of eyes: critics asked how does a highly functioning organ come to be thru evolution → Darwin argues that the final form came about thru minor steps that have been perfected bc whole parts are developed in useful and gradual stages
The eye example: Shows convergence between the endpoints of the vertebrates (bird and human) and cephalopods (squid)
Blending inheritance
Offsprings uniformly blend the features of the parents
Eg. two extremes have offsprings who have offsprings… until offsprings “wash out” with no genetic variation
Gregor Mendel
Particulate inheritance: pea plants are bi-allelic (only 2 alleles are observable / important)
Used findings towards the genetic foundation of evolution
Genetic locus, gene, gene pool
Genetic locus: position on the chromosome
Gene: unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring
Gene pool: represents all the alleles at all loci in all individuals
Rules of probability: Multiplication vs Addition
Rule of multiplication: the probability that independent events A and B will occur simultaneously is the product of their individual probabilities
Rule of addition: the probability that event A or event B will occur is equal to the probability of A plus the probability of B
Hardy-Weinberg principle (5)
p2 + 2pq + q2 = 1
Microevolution based.
Population assumptions: under these assumptions, allele frequencies in the gene pool will not change aka evolution isn’t happening
- No mutations
- Large (infinite) population
- Isolated (no gene flow)
- Random mating
- No natural selection
Microevolution (Forces) – Modern Synthesis, and Mutation
MODERN SYNTHESIS: aka neo-darwinism; articulated a new field of biology where you can identify the driver of the evolutionary process
MUTATION: random change in DNA
Microevolution (Forces) – Genetic Drift
- founder effect
- bottleneck effect
drift to loss or fixation occurs faster and is more likely in smaller populations; occurs bc populations are not infinitely large → produces random changes in allele frequencies that may lead to a loss of genetic variation
Founder effect: higher incidence in population due to founding population having high frequency of the allele (lack of gene flow) e.g. Amish of Lancaster County, PA where Ellis-van Creveld syndrome allele frequency is, PA vs. World: 0.07 vs 0.01
Bottleneck effect: large population shrinks to smaller population which leads to diversity loss e.g. greater prairie chicken and northern elephant seal
Microevolution (Forces) – Gene Flow
the movement of genes among populations due to migration and interbreeding
e.g. copper tolerance in bent grass near a mine → wind carries copper-tolerant alleles to non copper-tolerant plants, resulting in the the spread of this tolerance as a result of reproduction (not adaptation)
Microevolution (Forces) – Non-random mating
can lead to changes in genotype frequencies
Assortative: individuals tend to mate with individuals that are phenotypically similar to them
Disassortative: individuals breed with individuals unlike themselves
Inbreeding coefficient
Has negative correlation with verbal IQ due to the probability that a person with two identical genes received both genes from one ancestor → eg. incest
Just know how closely related two organisms are; inbreeding humans → higher coefficient of breeding correlates with lower learning abilities (true for non-humans as well)
Sickle-cell anemia
- point mutation
- heterozygote advantage
brought questions as to why diversity existed if “lesser” traits were destined to die out
Point mutation: changed the shape of blood cell due to incomplete dominance (aka heterozygous)
Heterozygote advantage: aka heterozygosity; allowed for higher tolerance / immunity to malaria but can clog in bloodstream / lead to other health consequences
Fitness
The relative contribution an individual makes to the gene pool of the next generation
an individual’s ability to produce viable and fertile offspring; environmentally dependent
Normal vs. Bimodal Distribution
Phenotypic variation
Normal distribution: aka Gaussian distribution; bell shaped curve
Bimodal distribution: two distinct peaks
Phenotypic variation : bimodal because gender based → eg, men are typically taller than women
Directional Selection
select away from original ideal towards one phenotype better adapted to the environment; i.e. dark mice living on dark lava flow
Stabilizing Selection
individuals in the middle are most advantageous; select against extremes; actively maintains genetic diversity
Disruptive Selection
Select against intermediate phenotypes; extremes are favored while anything in between is not
Eg. seacracker birds → birds with heavy/large bills exploit large seeds and birds with small/fine bills exploits small seeds BUT middle bills can’t exploit either
Ends up favoring bimodal distribution
Frequency dependent selection
common phenotype at a disadvantage; rare phenotype selected for
Eg. scale eating cichlid → has individuals that are let and right mouthed; dominant population vs surviving populations shifts as prey fish adapt to react to the dominant population’s attack but not the (ultimately surviving) population
Sexual selection: Intra vs. Inter
- sexual dimorphism
- epigamic traits
- anisogamy
INTRASEXUAL: selection within the SAME sex
- Sexual dimorphism: difference in appearance (eg. size / shape / color) between the sexes
males compete among each other for access to females
INTERSEXUAL: females choose mates due to limited offspring / energy to raise them, therefore more invested in who her partner will be
- Epigamic traits: selected for by the opposite sex
Females choice → Eg. paradise birds: males show themselves to females and have females choose; i.e. bird makes nest really pretty
- Anisogamy: sexual reproduction by the fusion of dissimilar gametes → Eg. bowerbird female gamesters are larger in size than male gametes
“Good Genes” hypothesis
questioned whether displays were allowing poor survival fitness genes to be passed OR display showcase both plumage and fitness → eg. long vs short calling tadpoles
Species concepts
- morphological
- biological
- phylogenetic
analysis of variation within a species
Morphological (MSC): characterizes a species by body shape and other structural features and is applied to asexual and sexual organisms → useful when information on gene flow is unknown
Biological (BSC): species as a population (or a group of populations) whose members have the potential to interbreed in nature and produce viable, fertile offspring (emphasis on reproductive isolating mechanism)
Phylogenetic (PSC): apples phylogenetic systematics, cladistic analysis, and assessment of relationships of genealogy in order to determine what should be called a valid species based on evolutionary history
Polymorphism vs. Phenotypic Plasticity
POLYMORPHISM: many phenotypic variations between closely related organisms due to the presence of multiple alleles
PHENOTYPIC PLASTICITY: Degree to which an organism’s phenotype changes depending upon its current or past environment
Reproductive isolation – Prezygotic (5)
H > T > B > M > G
locked in DNA before the zygote forms
- Habitat isolation: spatially separated
- Temporal isolation: different breeding times (eg. one species breeds in the spring; the other in the summer)
- Behavioral isolation: organisms can only recognize others of their species through a specific ritual → especially crucial in identifying potential mates
- Mechanical isolation: sexual organisms don’t “fit” together and physically cannot mate → eg. snails and their spirals
- Gametic isolation: not fusing at the gametic level even if copulation occurs
Reproductive isolation – Postzygotic (3)
V > F > B
prevents the formation of fertile offspring
- Reduced hybrid viability: inability to form normal gametes during meiosis → Eg. ensatina salamanders that live in the same region / whatnot may attempt to hybridize but the majority will fail
- Reduced hybrid fertility: inability to breed, therefore infertile or sterile; usually a result of cross species offspring → Eg. mule as a result of crossing a horse and donkey, resulting in superior physical form
- Hybrid breakdown: aka hybrid lethality; some first generation hybrids may be fertile but subsequent generations eventually lose their fertility → Eg. wasps
Ring species
connected series of neighboring populations that can interbreed with relatively closely related populations but for which there exist at least two “end” populations (too distantly related to interbreed)
eg. Ensatina salamanders: ring distribution formed due to heat distribution
Hybrid Zones
- 3 Outcomes: RSF
population with high gene flow - barrier forms, creating divergent patterns - might hybridize and interbreed
THREE OUTCOMES:
Reinforcement: populations develop to divergently that hybridizing is no longer possible
Fusion: merging of divergent populations into a single population
Stability: existence of the divergent populations AND hybrid population concurrently
Speciation
- allopatric
- sympatric
aka Cladogenesis: refers to a lineage-splitting event that produces two or more separate species
ALLOPATRIC: different species in different areas (“allo” meaning other)
SYMPATRIC: different species in the same area → Polyploidy: containing more than two paired (homologous) chromosomes
Taxon (pl. taxa)
- node based approach
- stem based approach
- apomorphy based approach
A phylogenetic group
- Node based approach: includes extant taxa, common ancestor, and all descendants (crown group?)
- Stem based approach: includes extant taxa, common ancestor, all descendants, and all stem/extinct taxa → crown group + all stem/extinct taxa relating to crown group
- Apomorphy based approach: focus on synapomorphy
Sister Taxa
Paraphyly vs. Polyphyly vs. Monophyly
SISTER TAXA: two phylogenetic groups (clade or species) that are each other’s closest relatives
Paraphyly: includes an ancestor but not all descendents
Polyphyly: does not include the common ancestor of all members of the taxon
Monophyly: refers to a clade; consists of a single ancestral species and its descendants
Crown group vs. Stem group
Crown: regarding extant taxa, their common ancestor, and all descendants from that common ancestor ; includes extinct taxa but not extinct taxa
Stem: very closely related to crown group but are not included; therefore considered t o be paraphyletic to the crown group
Ingroup vs. Outgroup
In: specific division of taxa whose evolutionary relationship is being determined
Out: taxon chosen to help polarize the characteristics but similar enough to relate to ingroup, even if they don’t particularly belong in it
Character Matrix
choose characteristics (present in taxon) you’re interested in studying and then score taxa based on whether the characteristics are present → allows for easier construction of cladograms
Parsimony analysis
aka Occam’s Razor
simplest explanation that can explain the data is preferred; don’t make any more assumptions than necessary
DNA-DNA hybridization
Historical study;
Single strands of DNA taken from each of 2 species then hybridize their DNA strands into a new double helix
Then apply heat to separate the newly made strands; the more heat (energy) needed to separate the two strands, the stronger the DNA bonds (the closer the two species are to each other)
Genetic sequencing
Modern study
DNA alignment: sequencing each base pair and determining structure
Phylogenomics
refers to the study of whole genomes
Study individual genomes in animals - indicates certain characters
Deletion of certain genomes indicate something happened within the lineage (practiced in lab)
Phylogram
Different from cladogram since branch lengths are indicative of distance/relationship genetically or recency of evolutionary split
Rafflesia
Hyrax
RAFFLESIA: molecular analysis of floral gigantism
HYRAX: little thing that looks like a rat but elephants are closely related to it?? → Unresolved polytomy: we don’t know if they’re closer to manatee or elephant
Adaptive radiation
period of relatively rapid speciation that coincides with the evolution of beneficial phenotypes → as opposed to EVOLUTIONARY radiation (explosive evolution / diversification of a group of organisms into forms filling different ecological niche)
Trophic (Feeding) guild
Sympatric carnivores of Israel
Community assembly: structure prey-predator relationships developing in close geographical places
defined as any group of species that exploit the same resources, often in related ways
Coevolution
Direct adaptations by one organism in response to the adaptations of another organism
Batesian vs. Müllerian mimicry
Bates: A harmless species looks like a dangerous (distasteful) one
Muller: A harmful (distasteful) species looks like a harmful (distasteful) one
Aposematism
aka Unken reflex
animal expose a colorful part of themselves and shows that they’re dangerous
e.g. newt
Biological arms race
aka antagonistic coevolution where one species develops a response to deter a predatory one but the latter continues to overcome it
Newt, garter snake: tetrodotoxin (poison) in newts but the snakes eat them, newts just keep getting more poisonous and snakes keep adapt
Types of Fossil Preservation
I > C > R > M > T > L
- Intact or body fossils: preserving both flesh and bone; 3D with original material → Eg. frozen tundra; amber
- Compression: usually of plants preserved in sedimentary rock via physical compression
- Replacement: external materials (eg. minerals) replace original material via diogenesis process → original morphology usually preserved
- Molds and casts: original material no longer present but morphology still exists e.g. shell casts in limerock
- Negatives → eg. indents
- Positives → eg. filled snail shells - Trace fossils (ichnofossils): typically made of footprints; indicative of migrant behavior, population, etc.
- Lagerstatten: cases of SPECTACULAR sedimentary preservation → might be the best ever
Eg. full body squid even though squids are soft bodied and hard to preserve
Index Fossils
good for identifying where in time you are; useful for dating / correlating the strata in which it was found
Radiometric Dating
(WW2) dependent on isotopes present (must decay into other isotopes) due to variants in neutrons; unstable isotopes decay over time
Parent and daughter isotopes
Daughter isotopes is 3 half lives after parent isotope
Half-life → eg. 14 C is 5.73 Ka
Geological Time Scale (PPMC)
Origin of Life
Origin of Earth (4.6 Ga)
Precambrian, Paleozoic, Mesozoic, Cenozoic
(3.9 Ga)
Miller-Urey experiment: helped convince scientists that living organisms came from inorganic compounds → answered the “how did life come from the void” question
Created amino acids (basic building blocks of life) from chemical composition of rocks
Cambrian Explosion
- burgess shale
- cambrian substrate revolution
(542 Ma): lots of evolution as a result of the experimental explosion, most of which died off
Burgess shale: fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada; famous for the exceptional preservation of the soft parts of its fossils
Cambrian substrate revolution: priapulid worms burrow into the marine sediment, thereby introducing oxygen into a formerly anoxic sea floor → new potential for life!
Macroevolutionary trends (6) E > A > CE > C > P > DG
- Extinctions
- Adaptive radiation
- Convergent evolution
- Coevolution
- Punctuated equilibrium
- Change in developmental genes
Exaptation vs. Tinkering
EXAPTATION: cooperation of an existing structure for use in a new functional context → viable explanation for how complex evolutionary beings develop over time, leading to speciation within lineages
eg. Pitcher plants, flytraps : adapted leaves; Sundews: rely on modified trichomes to capture insects
TINKERING: rebuilding function from organs / abilities that were not evolved for a particular reason or were byproducts of evolution → lends to the creation of novelties
eg. Archopteryx: origin of flight in birds with different feathers for different purposes
Tempo and mode of evolution (PG and PE)
PHYLETIC GRADUALISM: model of evolution which theorizes that most speciation is slow, uniform, and gradual → steady transformation of a whole species into a new one
PUNCTUATED EQUILIBRIUM: morphological stasis interrupted by bursts of evolution
Morphological Stasis: refers to the period of time in which a species accrues little to no morphological change
Eg. dawn redwood trees; horseshoe crabs
Levels of Selection
Species selection: consider that lineages are comparative to alleles thus creating macroevolutionary changes through different rates of replication and the extinction of lineages
Evolutionary developmental biology
aka “evo-bio” biology; study of developmental biology to shed light on evolutionary dynamics
Tetrapod origins
biological superclass that includes all living and extinct amphibians, reptiles, birds, and mammals → eg. Tiktaalik: aka fishapod; the transitional form from fish to amphibians
Big 5 Mass Extinctions
O > D > P > T > C
* know years*
- End of Ordovician (~444 Ma)
- Late Devonian (~375 Ma)
- End of Permian (~251 Ma)
- End of Triassic (~200 Ma)
- End of Cretaceous (~66 Ma)
Plate tectonics
Earth very dynamically shifting via plates located under continents; concept solidified in the 1950s → PANGEA
Biogeography: correlation of fossils and geography based on pangeanic history, overlap of fossils, and fitting of continental edges
Basal Synapsids
on the evolutionary path to us! → “mammal-like reptiles” named so by the fusion of their skulls (as opposed to diapsids with two holes in their head) ⇒ incorrectly named because they’re not reptiles OR mammals
eg. Dimetrodon (270 Ma)
Vertebral spines: rigid canals that carry blood into “fins” for temperature control → warming their blood via sun or evaporative cooling, also deters predators
Permo-triassic extinction
P > V> M > F
353 Ma ;; no single cause
Possible mechanisms:
- Plate tectonics: sea-level change; increased aridity; habitat loss
- Volcanism: greenhouse effect, ocean anorexia, ozone depletion; increase in UV radiation
- Methane belch (?) : from sea floor; creates greenhouse gases that are more dangerous than CO2
- Formation of Pangea increased competition during the adjustment to a new equilibrium + resulted in the loss of coastal habitat and different climates
K-Pg event
- Iridium Later and Chicxulub
- Nuclear Winter
65.5 Ma – aka KT- extinction; end of Mesozoic era
extraterrestrial explanation as a simple / catastrophic explanation for the mass extinction (big rock, hits earth, causes problems, all dinosaurs die)
** More to the story: speciation rates have been declining even before asteroid hit
- Iridium layer, Chicxulub crater: evidence found in the iridium layer (bc asteroids contain iridium) and dated to be around the time of extinction + found a crater!
- Nuclear winter: posited as a result of the asteroid landing; prolonged and worldwide cooling and darkening caused by sunlight-blocking smoke and soot entering the atmosphere
Early hominis
- Sahelathropus
- Ardipithecus
- Australopithecus
Sahelathropus (7 - 6 Ma)
- Foramen magnum position: evidence for bipedality (walked on 2 legs
- Ardipithecus (5.6 - 4.4 Ma)
Found complete skull, teeth are smaller compared to gorillas
Really long arms compared to legs, curved phalanges: indicates that they lived in trees area (arms used for swinging)
Australopithecus (4.2-1.8 Ma)
Homo (2.8 Ma)
- brain size evolution
- manual dexterity
Persistence hunting
Coincides with origin of stone tools
Hominin carnivory: butchery of large animals hypothesized to be caused by stone tools
Brain size evolution
Eating meats helped brain size expand through evolution
Manual dexterity
Precise and powerful grip: manipulative skills
Long strong thumb
Persistence hunting
Endurance running, a group strategy that can undertake fast animals
Out of Africa, Part 1 (1.8 Ma)
Part 2 (`100)
Part 3 (~14.5 Ka)
Dmanisi, Georgia: skulls of a species closer in relation to us than monkey but not exactly homo sapiens; heavy brow ridge, slight projecting of the lower facial profile (prognathism), larger brain than ancestral primate forms (still smaller than ours though)
(~100 Ka) moved throughout Western Europe and Australia; ice glaciers blocked passage into the New World until 20 Ka
Immigration into America: Beringian land bridge allowed for passage into the Americas during the warm season; nomadic homo sapiens likely followed food
Mastodon kill site in Florida: aka Page-Ladson site; underwater archaeological site with great preservation of stone tools and Mastodon (relatives of elephants) bones
Homo sapiens (~300 Ka)
Jebel Irhoud, Morocco (North Africa): earliest (currently known) representation of anatomically modern humans; reduced (but still heavy) brow ridge, long and flat brain, similar facial profile and dental configuration to us; strong evidence of tool making / usage of fire, dated through thermal luminescence (property of some materials to become luminescent in high temperatures after accumulating energy for a long period of time)
Late Pleistocene Extinctions
- Richard Owen
- Megafauna
Richard Owen was the first to suggest that ancient megafauna may have been driven to extinction by the “agency of man” through his studies of the extinct Moa birds of New Zealand and large invertebrates of Australia
Megafauna: extinction correlated in time with the arrival of humans → CAUSAL RELATIONSHIP since larger animals were in direct competition with humans for resources and had longer reproductive cycle (with low numbers of offspring per cycle)
Mass Extinction #6 ?
striking similarities between past mass extinctions and extinctions of today with an overall reduction in faunal body size; high rate of species loss per unit of time as compared to background extinction rates of the fossil record (measurable although difficult)
Anthropocene:
Anthropocene
- Plastiglomerates
- CO2 anomaly
defined as the period during which human activity has been the dominant
Plastiglomerates: acted as marker / deposit for the start of Anthropocene; new kinds of rocks on Hawaii where debris plastics are deposited on beaches, mixed with sands / shells / rocks, and then heated over time (eg. through bonfires) to create plastic conglomerates with natural materials
CO2 anomaly (c. 1610 CE): “discovery” of the Americas and the subsequent population decimation (as a result of warfare and disease) allowed flora to grow and therefore absorb more CO2, leading to a global change in altered carbon isotope budgets → change in atmospheric chemistry related to the sequestration of CO2 by plants
How does energy from the sun result in i) decreasing temperature at higher latitudes; ii) wet tropics and dry desert zone; and iii) the annual cycle of the seasons (seasonality)?
- Latitude and Solar Energy
- Hadley Cell
- Seasonality
LATITUDE AND SOLAR ENERGY: basic gradient of temperature; hottest at equator (0 degree latitude) with temperatures cooling towards both poles
I=Iocos(α)
I=Intensity of radiation hitting the Earth
Io=solar radiation when sun hits directly on equator
HADLEY CELL: first step in understanding how global patterns affect precipitation; great “cell” of circulating air that generates a lot of rainfall at the tropics and lack of rain at deserts (which are typically located at 30 degrees latitude) → warm air rises and generates rain once the partial pressure of water increases to the point of saturation (usually happens when warm air rises and then moves away from the equator until it cools to the point of falling)
SEASONALITY: result of Earth’s tilt and axial rotation; different parts of the Earth receive different amounts of solar energy at different parts of the year
Why does temperature decrease and rainfall (usually) increase at higher elevations in mountains? How do mountains create rain shadow?
- Elevation and Temperature
- Rain Shadow
ELEVATION AND TEMPERATURE: lower pressure means lower temperatures (see ideal gas law of PV = nRT) → lower temperatures push the water vapor from the windward side to the saturation point
RAIN SHADOW: occur on the leeward side as a result of descending air and reduced moisture left in the atmosphere → drier airs as a result of increasing temperatures (again, see ideal gas law)
What are the influences of the ocean on summer vs winter temperatures, and how do these influences create maritime climates near the coast?
View the ocean as a large body of water → possesses high thermal inertia (harder to warm up; cools down slowly), therefore near-coast winters are milder and summers are cooler
MARITIME CLIMATES: muted seasonality (=low amplitude); ocean acts as a thermal buffer that stabilizes a climate against changes; contrast to continental climates (polarized seasonality)
What are the three essential factors that create the Mediterranean-type climate in California?
MID-LATITUDE: moderate rainfall and temperature b/c CA has a ocean nearby as well, CA doesn’t have frost (=no too COLD winters in CA)
Higher latitude than desert (30 degrees); lot of rainfall → this is why CA has moderate rainfall
having HOT summers
COOL OCEAN: maritime climate with wet or mild winters
SUMMER HIGH PRESSURE SYSTEM OVER PACIFIC OCEAN: blocks summer storms from the West → clockwise high air pressure spinning system that makes all the summer storms hit the North (ex; Vancouver and Seattle get a lot of rain b/c of this clockwise system)
What are the three definitions of ecology?
- Study of the relationships between organisms and their environment (Haeckel’s original definition)
- Study of the distribution and abundance of organisms
- Study of transformation and flux of matter and energy in natural systems
What is meant by “species distribution”? What are the roles of dispersal and dispersal limitations as a factor influencing distribution?
SPECIES DISTRIBUTION: manner in which a biological taxon is spatially arranged
DISPERSAL: net movement of individuals or gametes away from their parent locations; sometimes expands the geographic range of a population or species
Contributes to the spacial distribution of species
DISPERSAL LIMITATIONS (time, habitat selection, biotic, abiotic factors) Global transportation broke these limitations (ex: Cattle egrets got dispersed in Am after New World got introduced/ human brought them into Americas)
What are the differences between biotic and abiotic factors?
BIOTIC: living components of the environment
Other plants, animals, and microbes (same and diff species)
ABIOTIC: non-living components of the environment
Temp, wind, soil composition, shade
What the the different meanings of “environmental gradient”, and how do these help us understand species distributions?
a range of environmental conditions e.g. low to high temperature, low to high soil nutrients, low to high pH
some are PHYSICALLY CONTINUOUS → e.g. the gradient in temperature moving from the bottom to top of mountain (elevation gradient)
others are PATCHY → span a range of environmental conditions (water/soil nutrient level)
How are the three major invertebrate groups (Ephemeroptera, Trichoptera, Plecoptera) distributed along gradients of water quality in accordance to their reflection of differences in environmental tolerance?
Species distributions along gradients are typically unimodal (one peak along the distribution, either in the middle or at one end or the other)
Remember %EPT from lab? This is it. ( INTOLERANT )
They are abundant in better water quality(more oxygen in water) = intolerant of low water quality (polluted water) -> AKA low oxygen in water
Shared vs. Distinct Preference model
SHARED preference model : intrinsic physiological response of the species that they do better at one end → Some can do well in competition but cannot tolerate the lower water quality (intolerant); Need to experiment one species at a time to see if species can tolerate or not
DISTINCT preference model : all species actually evolved different preferences (live in diff conditions) → Do not need to experiment one species at a time
What is the concept of population?
- demography
- 4 influences of population
- species
- level of organization
POPULATION: group of individuals of the same species that live in the same area
DEMOGRAPHY: study of the vital statistic of a population and how they change over time
4 INFLUENCES: 1. Birth (B) 2. Death (D) 3. immigration 4. Emigration \++ B-D model as being Nt+B-D=Nt+1 (# individuals in a population at a time)
SPECIES: population(s) whose members have the potential to interbreed in nature and produce viable, fertile offspring
How does a population with a constant birth rate (b) and death rate (m) exhibit geometric or exponential growth?
Population growth model: Nt+B-D=Nt+1 → the size of population in a given year is the size in previous year plus the number of new individuals born and minus the number of individuals that died
Absolute rate: just counting individuals (ΔN)
Hard to compare
Relative rate:: rΔN; intrinsic rate of natural increase
dN/dt=rN
Geometric/multiplicative model: Population increase by constant fraction
(ΔN/Δt)=rΔN
Geometric growth is in discrete time (year to year) and exponential is continuous.
What are the concepts of finite rate of increase (r△) and intrinsic rate of natural increase (r)?
r△= describes rate of population growth in discrete time (time t to t+1)
r = instantaneous / continuous per capita rate of increase
How do you read population growth graphs using linear vs logarithmic y-axes for population size and survivorship? Why use log graphs in the first place?
Exponential growth is linear when the y-axis (population size) is log-transformed
Use log graphs to respond to skewness towards large values OR show percent change or multiplicative factors
What is a cohort life table and a survivorship curve? What are the differences between types I, II, and III? What is meant by “age-specific fecundity (reproductive) output”?
COHORT LIFE TABLE:
Cohort life table
Cohort: group of individuals born at the same time
Track individuals their whole life and look at their fate
Tagging animals and tracking them
Survivorship Curve: a plot of the proportion or numbers in a cohort still alive at each age
- types I - a long adult period and clear aging and die when older e.g. humans
- types II - constant probability of dying all their life e.g. rodents, squirrels
- types III - producing lots of small offspring, most in which dies, and a few live to adulthood e.g. oysters
What is the carrying capacity concept (K)? How does an increasing population size result in a lower birth rate and/or higher death rate?
CARRYING CAPACITY (K): maximum number of individuals in a population that can be sustained with the current set of resources
The exponential growth function can be modified to include K, resulting in the logistic growth model.
r as the intrinsic rate of increase that describes how quickly a population size will increase starting at low density
K - N as density dependent and thus a modifier of N
What are the differences between the absolute growth rate (dN/dt) and the per capita growth rate (dN/dt divided by N)?
Absolute growth rate: number of individuals added per unit time
Per capita growth rate: growth rate per individual currently in the competition
In exponential model, r equals the difference between birth (b) and death (d) rates.
In logistic model, the per capita rate is r(K-N)/K , or the intrinsic growth rate multiplied by the density dependent term.
How does the logistic model relate to the S-shaped population growth curve?
When N is very small, it simplifies to the exponential model, and when N = K, dN/dt = 0 which is the flat part of the S-shaped curve when the population reaches carrying capacity.
What are the differences between density-dependent and density-independent factors that influence population dynamics?
DENSITY DEPENDENT: aka K SELECTION; selects for life history traits that enhance an individual’s fitness when a population is fairly stable → higher density means higher competition among individuals for limited resources
DENSITY INDEPENDENT: aka R SELECTION; selects for life history traits that maximize reproduction and the ability for a population to increase rapidly at low density
What are the key features that describe a species life history and the characteristics of R- and K-selected populations? (Specifically, age and frequency of reproduction, life span, number of offspring, investment in parental care.)
- Life History (5)
- K Selection (8)
- R Selection (8)
LIFE HISTORY: suite of traits related to a species lifespan and timing and pattern of reproduction
- Survivorship curve and lifespan
- Age at first reproduction
- Number and timing of reproductive episodes
- Size and number of offspring in each episode
- Duration and investment of parental care
K-SELECTION: density dependent selection, selects for life history traits that enhance an individual’s’ fitness when a population is fairly stable
- Late age at first reproduction
- Long lifespan
- Long maturation time
- Low mortality rate
- Few number of offsprings per reproductive episode
- Many number of reproductions per lifetime
- Extensive parental care
- Large size of offspring/eggs
R-SELECTION: density independent selection, selects for life proximity traits that maximize reproduction and the ability for a population to increase rapidly at low density
- Early age at first reproduction
- Short lifespan
- Short maturation time
- Often high mortality rate
- Many number of offsprings per reproductive episode
- Few number of reproductions per lifetime
- No parental care
Small size of offspring/egg
How does the allocation of limited resources create life history trade offs, which are shaped by natural selection in different environments?
PRINCIPLE OF ALLOCATION: individual organisms have a limited amount of resources to invest in different activities and functions; resources invested in one function are not available for another
In life cycles, resources must be allocated among growth, survival and reproduction → animals allocate TIME and GROWTH to different activities; plants allocate BIOMASS and NUTRIENTS to different parts that do different functions simultaneously.
How does the clutch manipulation experiment with collared flycatchers demonstrate a cost of reproduction?
Trade-off between reproduction now versus later
COST OF REPRODUCTION: producing more offsprings takes more energy away from the parents (because the parents have to raise them), so the parents won’t get to produce more offsprings later on
What is the definition of competition (in the context of ecology)? What is the distinction between interference and exploitation competition?
COMPETITION: occurring when two or more individuals (not species) share a resource and consumption by one reduces its availability for others, thereby limiting supply; causes ecological consequences such as reduced growth, survival or fecundity → can be intraspecific (same species) or interspecific (diff species)
INTERFERENCE COMPETITION: direct; physical contact / prevention → eg. lions and hyenas
EXPLOITATION COMPETITION: indirect; mediated by consumption of shared resources
What is the definition of ecological niche and how does this help to describe the patterns of resource partitioning in communities?
ECOLOGICAL NICHE: role and position a species has in its environment; includes all abiotic and biotic interactions between an environment and a species ability to survive / reproduce
RESOURCE PARTITIONING: species having different niches also have different sets of requirements → when in competition with each other, they can go into different parts of the gradient and consume resources so that their niches generate multispecies community of high diversity
What was Gauss’ Paramecium experiment? How did the two different experiments with the species in mixture illustrate competitive exclusion and coexistence?
Tested three types of paramecium: Paramecium aurelia; P. caudatum; and P. bursaria → All three have log curves when alone in the flask (intraspecies)
Combining A and C led to extinction of C (competitive exclusion); combining C and B led to coexistence at a lower carrying capacity (resource division)
COMPETITIVE EXCLUSION: if two species are competing for a limited resource, the species that uses the resource more efficiently will eventually eliminate the other locally; no two species consuming identical resources can coexist
COEXISTENCE: only occurs in species that use different resources; results in specialization → eg. C feeds in open water but B feed at the bottom of the flask
What was Connell’s barnacle experiment? How did the results illustrate the role of competitive exclusion in influencing species distributions? What are the differences between the realized niche and the fundamental niche?
Tested two types of barnacles: Cthalamus and Balanus → intertidal environment promotes variation in temperature, solar exposure, etc.»_space; First scientist to test hypothesis about tropical diversity
C is usually found higher on rocks than B → removed B and discovered that C can live lower down on rocks but is usually outcompeted by C → → fundamental niche of C is greater than its realized niche, which is limited by B
REALIZED NICHE: actual set of environmental conditions in which a species is able to establish a stable population in the presence of competitors
FUNDAMENTAL NICHE: full range of environmental conditions in which a species is able to maintain a stable population in the absence of competitors
How does competition result in evolutionary divergence in resource use (called character displacement)?
Paradox of not competing now due to strong competition in the past
Allopatric species tend to be morphologically similar and use similar resources. By contrast, sympatric populations, which would potentially compete for resources, show differences in body structures and in the resources they use.
Eg. Darwin’s finches on the Galapagos islands: allopatric but assumed that if sympatric then there would be competition until the beak sized diverged to fulfill the niches that allow for coexistence
What are the definitions of predation, herbivory, and parasitism?
- Symbiosis
SYMBIOSIS: tight and persistent relationship
PREDATION: an interaction in which the predator kills and eats the prey
HERBIVORY: an interaction in which an organism eats parts of a plant or alga but (often) does not kill it
PARASITISM: an interaction in which one organism (the parasite) derives nourishment from another (the host), which is harmed in the process; parasites are smaller than the host and live on or in the host’s body
What is the Paramecium-didinium, lynx-hare, and mite empirical systems? How do the predator-prey systems often show cycles or oscillations in population size of each species, why peaks in population are staggered by a ¼ phase, and why the prey population peaks before the predator?
- Lotka Volterra predator prey model
PARAMECIUM-DIDINIUM: P is prey, D is predator → first system led to extinction of both as D ate all of P → second system gave refuge to P; once D went extinct, P emerged
LYNX-HARE: contributed to generation of the Lotka-Volterra predator-prey model where the prey population typically peaks before the predator population, leading to oscillations that “chase” each other
MITE EMPIRICAL SYSTEM: structure 1 was single plane, prey went extinct → structure 2 had multiple levels that allowed for stabilization of three cycles before prey went extinct; stability as a result of refuge
What are the chemical, morphological, visual or behavioral defenses of prey species against predation?
CHEMICAL: poison, skunk’s spray, poison in plants (neurotoxic effects)
→ Coevolution (simultaneous evolutionary changes between two species that interact closely so each is a strong selective force on the other) e.g. milkweed and monarch butterfly
MORPHOLOGICAL: bodies that can change → eg. puffer fish
VISUAL: can be Batesian (non poisonous looks like poisonous) or mullerian (all poisonous; mutually benefits)
BEHAVIORAL: hiding, fleeing, and forming herds or schools
What is mutualism and what are the various ways in which mutualists can benefit each other? (Consider ants and acacia trees; clustering of plants in high elevation environments; and cushion plant interactions.)
MUTUALISM: symbiosis that is beneficial to both organisms involved
VARIOUS WAYS: disperse seeds; pollinate flowers; defend against harmful organisms; gather nutrients; forage, feed, and digest; photosynthesize and respire; modify environment and provide habitat
Eg. Ants and Acacia trees: Acacia provides a home to the ants, who protect the tree from all predators
Eg. Cushion Plants cluster together in order to protect one another from extreme solar exposure and thus conserve water.
What is the role of pathogens and disease in natural communities?
PATHOGENS: organism or virus that causes disease
Have impacts on distribution and abundance i.e. Chestnut blight makes Chestnut trees ecologically extinct
DISEASE: progresses through stages of within host dynamics, between host dynamics, and extinction
What is the basic disease spread model? What is the prediction that disease will spread if the number of susceptible individuals is greater than a critical threshold?
Susceptibles, Infected, Recovered: so individuals in host populations move between the boxes as they get sick and get better, the size of population isn’t necessarily changing
Transmission: susceptibles can become sick
Recovery: individuals get better
Immunity: Recovered going to susceptibles has a rate of 0
VARIABLES:
S=number susceptible
I=number infected
PARAMETERS:
β=transmission rate; higher values mean that when an infected individual comes into contact with a susceptible, the disease is more likely to be transmitted and the susceptible gets sick
r= recovery rate (time^-1); higher values mean infected individuals recover more quickly, and may have temporary or lifetime immunity
d=death rate of infected individuals (time^-1)
m= r+d (recovery+death)
When does disease spread?
Critical threshold refers to ST = m / β , where m is the combined rate of death (d) and recovery (r) of infected individuals and β (beta) is a transmission coefficient.
Disease spreads when susceptible population exceeds critical threshold, so disease spread can be prevented if S is lower or ST is higher
How do you apply the disease model to understand why (from an ecologist’s perspective) public health measures help to reduce the spread of disease?
- Vaccinations (shortcut!) reduce S
- hygiene reduces β, ST goes u
- quarantine reduces β, ST goes up
- culling reduces S
- crowd reduction reduces S (per unit area)
- treatment increases r and ST
Eg. Capetown study in South Africa: no immunity or vaccinations
What are the definitions of disturbance and succession?
DISTURBANCE: refers to loss of biomass; size is relative to organism of community natural or human event that change a biological community
SUCCESSION: slow and orderly progression of changes in community composition through time, usually following a disturbance
What are the differences between primary and secondary succession?
PRIMARY: de novo process; succession on bare ground that is completely devoid of life → eg. glacial retreats at Glacier Bay, AK
SECONDARY: lots of things survive disturbance to an existing community and some organisms survive → eg. dormant seeds
How is plant life history is adapted to disturbance? What are the key differences between early successional and late successional species?
PLANT HISTORY: namely reproductive strategies; also include any adaptations to withstand disasters that remove biomass (eg. wildfires)
EARLY: small seeds; extended dormancy with disturbance triggers germination rapid growth; short life span; early reproduction and high fecundity
LATE: large seeds; no dormancy shade to tolerate seedlings; slow growth but has a long reproduction period.
How do early-successional, pioneer species can inhibit or facilitate the colonization of late-successional species?
(3) FTI
Aka “why do ‘late’ species replace ‘early ones’?”
FACILITATION: early modifies environment in ways that the favor later-arriving species
TOLERANCE: early has little influence on later arriving species
INHIBITION: early inhibit establishment of later but early is short lived
FIRE ECOLOGY: What are the three conditions for fire: ignition, fuel, conditions (weather, topography)? What are some plant strategies for post-fire regeneration: above-ground survival, below-ground survival and resprouting, post-fire seed germination and regeneration?
Serotiny: canopy seed storage
IGNITION (historically lightning) + FUEL (typically plants) + WEATHER CONDITIONS / TOPOGRAPHY (fire promoted by dry/ air / hot winds and steep topography)
ABOVE GROUND: thick bark, few branches with foliage out of reach
BELOW GROUND: resprouting by growing new stems from the dead stems
What is the latitudinal diversity gradient and the role of environmental gradients in energy and water availability?
(3) REC
Richness: total number of species
Evenness: relative abundance of species
Composition: which species are present
What does the species-area curve refer to?
Measure of diversity of taxon relative to area occupied; linear when log
NEW GUINEA ISLAND STUDY: islands close to New Guinea had more diversity than farther ones even if the area of islands was relatively consistent or close to one another → introduces proximity as a factor
How does the island equilibrium model relate species diversity on islands to area and distance due to the balance of immigration and local extinction?
ISLAND EQUILIBRIUM MODEL: considered colonization and extinction rates to reach a balance of equilibrium diversity (number of species remains constant but composition remains in flux; aka dynamic diversity)
Considered island size (larger islands will have lower extinction rates and greater diversity) and island distance (far islands have lower colonization rates than near islands) to have FOUR equilibrium points of island diversity
Who is Robert MacArthur (1930 to 1972) and what was one of his important contributions to ecology?
WILSON ISLAND BIOGEOGRAPHY STUDY: types of island diversity as relative to the size and proximity of islands in relation to colonization and extinction rates → applications of biogeographical understanding
How does photosynthesis scales from being at a leaf-level to gross primary production (GPP) of ecosystems? What is meant by net primary production (NPP) and autotrophic respiration (R)?
PHOTOSYNTHESIS SCALES: solar energy captured in carbon bonds within plants via chloroplasts; rate at which photosynthesis or chemosynthesis occurs in order to produce oxygen (aka GPP, or gross primary production)
** NPP IS DEPENDENT ON GPP **
NET PRIMARY PRODUCTION (NPP): refers to biomass; used by plants to grow and reproduce but eventually consumed by animals and cycle through trophic system → NPP = GPP - R (Respiration)
Why are water, temperature and nutrients a factor in limiting NPP?
WATER: plants lose water (transpire) in exchange for gaining carbon in photosynthesis; water availability can negatively impact the GPP amount if insufficient water is taken up by plants since they can’t afford to open their pores to take in CO2
Plants open pores to take CO2 in, but H2O leaves when pores open
If water is limiting: plants can’t afford to open pores => pores can’t open, Carbon can’t come in
TEMPERATURE: photosynthetic enzymes are temperature sensitive, therefore cannot function in extremes
Too cold: for kinetic to work
Too hot: enzymes get denatured
Not every plant operate in the same temperature
NUTRIENTS: photosynthetic enzymes also need large amounts of nutrients (specifically nitrogen) for construction; nitrogen availability affects soil fertility affects photosynthesis affects GPP ; higher N means higher photosynthetic rate
What is relationship between NPP and diversity, at a global scale?
Higher NPP: usually across tropic (warm + wet)
Ocean: low NPP
UNITS: kg biomass/(m^2 x year)
KNOW: NPP ranges from 0-2.5 kg biomass/ (m^2 x year)
What are the roles played by the following organisms in the flow of energy and nutrients?
P > H > C > D
PRIMARY PRODUCERS (Trophic level 1): plants, organism that photosynthesize and capture energy
HERBIVORES: primary consumers; first step in taking the energy stored into plants into the trophic levels
PRIMARY AND SECONDARY CARNIVORES: consume herbivores; important in culling herbivore biomass so plant biomass is sustained leads to less plants as primary carnivore lowers secondary carnivore biomass which heightens herbivore biomass which lowers plant biomass → different from primary predators only because a second carnivore is introduced
DETRITIVORES: consumption of DEAD tissue and organisms; cleanses the ecosystem of decaying organisms
How does energy flow up from one trophic level to the next? How is that energy partitioned into assimilated versus non-assimilated energy
FLOW THRU LEVELS: following original biomass (energy captured from the sun by plants) through the consumers it passes through to an organism that‘s drawing on that energy → RULE OF THUMB: 10% of energy transferred from each level to the next
ASSIMILATED ENERGY: partly used for production of biomass by consumers, and partly for heterotrophic respiration to drive metabolism
How much of the mass is actually consumed and assimilated into the body : Cellular respiration + Growth (new biomass)
Assimilated = taken into the body and used
NON-ASSIMILATED ENERGY: energy not used, not taken into the body e.g feces
What are the concepts of bottom-up versus top-down control on ecosystems? What are the consequences for abundance and biomass of primary producers, herbivores, and primary and secondary carnivores?
- three level trophic cascade
- four level trophic cascade
BOTTOM-UP CONTROL: increased production on lower levels leads to greater productivity in all levels → cascading effect
TOP-DOWN CONTROL: consumers depress / reduce the biomass of the trophic level on which they feed, which indirectly increases the biomass of the next trophic level
E.g more trout -> fewer inverts -> more algae
THREE LEVEL –
- Abundance of primary producers => lesser herb <= more carnivores
- Fewer prim/sec carnivores => Abundance of herbivores => lesser primary producers
- Abundance of primary/secondary carnivores => lesser herbs => more primary producers
FOUR LEVEL : ocean example
1. More Fish -> Fewer Carnivorous invertebrates -> More Herbivorous invertebrates -> Fewer Algae
SO: in a 3-level trophic cascade: more fish => more algae
BUT in a 4-level trophic cascade: more fish => fewer algae
2. Impt. example: Urchin barren (sea otters extinct/reduced by Orca => more urchins => less kelp)
3. Kelp forest (sea otter present => limit urchins)
What is meant by the term trophic downgrading?
Study concept of consequences that occur when removing apex consumers (occupy highest trophic level) from ecosystems, thereby affecting the trophic levels and the overall health of the ecosystem
Human activity tended to remove top predator (wolf eating livestock)
Eg. loss of top predators in rain forests reduce tree regeneration in rain forests
What are the concept of stocks, fluxes, and residence time in an ecosystem?
- 4 compartments
STOCKS: aka pool; amount of compound in one compartment of an ecosystem
FLUXES: rate of movement between compartments; concept of net flux; counted in ONE direction only
RESIDENCE TIME (RT): how long a compound spends in a compartment
4 DIFFERENT COMPARTMENTS:
- Biosphere (living components upon soil)
- Geosphere (geological setting)
- Hydrosphere (all water surfaces: ocean, lakes, streams)
- Atmosphere
What are the key differences between the phosphorus and nitrogen cycle, specifically the different reservoirs and key processes that transfer elements between compartment, and the primary sources that provide inputs to biological systems.
Eg. N-fixation from atmosphere; P-weathering from rocks
What is the role of vegetation in the global water and carbon cycles? The importance of biological N-fixation and industrial N-fixation (fertilizer manufacture) to the global nitrogen cycle?
ROLE OF VEGETATION: continually absorb CO2 and water for photosynthesis
BIOLOGICAL N-FIXATION: some bacteria are metabolically capable of taking in N2 and turn it into (almost) amino acids; other times, lightning can chemically transform nitrogen into forms that organisms can use
INDUSTRIAL N-FIXATION: aka Haber-Bosch process of using industrial means to incorporate nitrogen into the soil; humans now performing 50% of all N-fixation
How did the Hubbard Brook experiment has demonstrated the importance of internal cycling to conserve nitrogen in forests?
- watershed
- precipitation collectors
- weirs gauging station
- result
Woodstock, NH;
Used an entire watershed: area where all of the water that falls in it and drains off goes to a common outlet/one stream/output
Precipitation collectors: measure inputs
Weirs gauging stations: measure outputs: volumes of water that leave the watershed → demonstrated importance of N cycling in vegetation soils almost as a closed system, which is why forests lead in the production of photosynthesis
Powerful quantitative method: close N budget - measure all input/output; keep track of flux
RESULT: Deforestation increase N losses from ecosystem
With forest: leaves fall off -> decompose -> flux of N from decomposed leaves into streams
Without forest: roots gone, soil erode, leaves left over => disrupt internal cycle of N decomposing => enormous loss of N thru system.
How do human activities threaten(decline) biodiversity? (4)
- habitat destruction
- pollution
- exploitation
- global change
HABITAT DESTRUCTION: largest cause of loss; nearly irreversible
Conversion of habitat into human development
POLLUTION: dramatic effects; disruption of the ecosystem so much that it can no longer sustain the same level of productivity
EXPLOITATION: direct harvesting of a species that decimates its population, leading to higher chances of extinction → eg. hunting and harvesting, overfishing
GLOBAL CHANGE: fossil fuel emission => greenhouse gas effect => global warming eg. climate change
What are the experiments that test the relationship between biodiversity and ecosystem function? What are the complementariy and sampling hypotheses that explain these results?
COMPLEMENTARITY HYPOTHESES
Species with different or complementing requirements can utilize resources more efficiently overall => increasing productivity
E.g species w diff. Response to rainfall = greater stability/resilience in wet vs. dry years; compared to either one alone
SAMPLING HYPOTHESES
More species include in community = more likely that some super-productive will be included → Sample 10-20 species: more likely to include super-productive
What are the critical processes that lead to extinction of small populations?
- extinction vortex
- sequence of struggles (5)
- conservation genetics
Smaller population => Chance of extinction higher
aka “extinction vortex”; explains ensures that a population encounters as it get smaller in population → likelihood of extinction increases as smaller populations have a greater susceptibility to random fluctuation
SEQUENCE OF STRUGGLES: less ability to adapt (bc there’s less variation) => inbreeding depression (population becomes more subdivided as a result of fragmentation) => more demographic variation (smaller populations have higher chance of demonstrating extremes; eg. all males born in a dwindling population) =>lower effective population size =>(catastrophic event) EXTINCTION
Conservation genetics: small population -> Greater inbreeding => genetic defects (deleterious recessive) ;; coutneracted by
interbreeding w other populations
Inbreeding and loss of genetic variability and greater susceptibility to random fluctuations
What are the most important tools available for conservation biologists to restore habitats and maintain ecosystem integrity? How can conservative actions be adapted to conserve biodiversity in the face of climate change?
- habitat protection
- corridors
- enhanced gene flow
HABITAT PROTECTION: large parks can hold more species; allow species to find suitable microclimates nearby to reduce effects of dispersal limitation
CORRIDORS: connect existing lands, thereby enlarging the total protected area; connect warm to cool locations: ALLOW species to move to new locations as climate warms
ENHANCED GENE FLOW: allows for higher level of diversity that can adapt to changes; reduces susceptibility of a population → Allow interbreeding to increase genetic variability
How do greenhouse gas emissions contribute to global climate change? How do ecosystems act as carbon sinks and carbon sources (relative to the atmosphere)?
- climate
- green house gas emissions
- carbon sink
- carbon sources
Climate: long term averages of weather condition/ probability of events
GREENHOUSE GAS EMISSIONS:
Energy can be reflected back (as light) OR absorbed (warm Earth) => all bodies radiating thermal energy →
Earth warm => emit thermal energy/radiation back into space
BUT some gas molecules hit other gas molecule on the way out => warming up the molecules=> emit thermal energy → heat becomes trapped in atmosphere, although some will diffuse back into Earth
CARBON SINK: reservoir that accumulates and stores Carbon-containing chemical compounds for an indefinite period of time → process by which carbon sinks removes CO2 from the atmosphere
Compartment that remove carbon from atmosphere
E.g Reforestation
CARBON SOURCES: absorption of CO2 from the atmosphere by plant through photosynthesis → Flux of Carbon into atm
E.g Deforestation, fossil fuel burning
What are the distinctions between amplifying (positive) feedback loops and stabilizing (negative) feedback loops, and their respective importance in global climate? What is meant by “albedo” and what is its role in amplifying feedbacks?
AMPLIFYING (POSITIVE) FEEDBACK LOOPS: Can cause destabilizing consequences in a system or lead to “runaway” warming or cooling stability; Push thing further in the direction that it started with → Importance in global climate: once Amplifying Feedback Loops starts: hard/takes a long period of time for system to stabilize
STABILIZING (NEGATIVE) FEEDBACK LOOPS: reduce the fluctuations in the output ;;
- Energy balance: energy in (solar radiation) = energy out (emitted radiation)
System warm => feedback will cool
As E warming => E emit more radiation → Importance in global climate: how global warming happen
- Greenhouse (Heat-trapping) gases LOWER the emission line because some radiation is retained in the atmosphere, thereby increasing temperature → global warming shifts location of stabilizing feedback to the right
ALBEDO (=albino): how much energy is reflected from a surface (%solar radiation) Whiter surface (snow) reflect MORE energy => High albedo Vegetation has Low albedo High albedo when cold/dry
What are SEVERAL EXAMPLES of how climate change impacts ecological systems: changes in phenology; species distribution shifts; vegetation change; drought-induced tree mortality?
All responsive to climate change
PHENOLOGY: seasonal timing of biological events
E.g flowering time of cherry blossoms in japan (sensitive indicator to see if biological systems are respondent to climate change)
SPECIES DISTRIBUTION SHIFTS: (Joseph Grinnell survey → Craig Moritz re-surveyed)
- Expansion: found higher up (elevation) than last surveyed
- Contraction: not found in the high elevation than last surveyed = live in slightly lower elevation
VEGETATION CHANGE: learn from fossils e.g oaks adapted to warmer / drier climates
DROUGHT-INDUCED TREE MORTALITY
Accelerate in many forest biomes as a consequence of a warming climate → E.g Sierra forest treated with prescribed fire => Reduce tree vulnerability to fire
Thinning + Prescribed fire => REDUCE tree mortality during drought
