Unit 2: Ecology Flashcards
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: 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: 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)
Who was Alexander von Humboldt (1769 - 1859) and his contribution to the founding of ecology?
Climbed Chimborazo volcano (S. Am) and recorded plants → origins of modern ecology / biogeography thru looking at the distribution of plants and animals across geographic zones / climates
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
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; eg. other plants, animals, and microbes (same and diff species)
ABIOTIC: non-living components of the environment; eg. temperature, wind, soil composition
What the the different meanings of “environmental gradient”, and how do these help us understand species distributions?
- Defined as a range of environmental conditions e.g. low to high temperature, low to high soil nutrients, low to high pH
- Some gradients are physically continuous e.g. the gradient in temperature moving from the bottom to top of mountain; other gradients are patchy in the natural world, and the patches span a range of environmental conditions
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)
What is the concept of population?
+ levels of organization
Demography: the quantitative study of the structure, vital statistics, and dynamics of populations through time
POPULATION: group of individuals of the same species that live in the same area
SPECIES: population(s) whose members have the potential to interbreed in nature and produce viable, fertile offspring
Levels of organization: global ecology > landscape “ > ecosystem “ > community “ > population “ > organismal ecology
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 defined as a group of individuals born at the same time; tag and track individuals their whole life and look at their fate
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 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
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.
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 Joseph 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.
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
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
