Lecture 8 Flashcards
Ecosystems
ecosystem
all the organisms living in a community as well as the abiotic factors with which they interact
two important ecosystem processes
- energy flow
- chemical/nutrient cycling
autotrophs vs. heterotrophs
autotrophs (primary producers)
- foundation of ecosystems
- form organic molecules through the reduction of inorganic carbon (or nitrogen/phosphorus) obtained from the environment
heterotrophs (consumers)
- obtain organic carbon other elements from other organisms
- include primary/secondary/tertiary/quaternary consumers and decomposers
decomposers
a special class of consumers that break down molecules from primary producers/consumers, and return carbon (and other elements) to the ecosystem in inorganic form
trophic structure
a measurement of community structure that focuses on how energy flows from autotrophs to heterotrophs
two types of trophic structure
- food chain: focuses on the transfer of energy and nutrients through trophic levels by showing one series of interactions
- food web: focuses on the transfer of energy and nutrients through trophic levels by showing “all” interactions (focuses on predator-prey; excludes parasitism)
trophic level
the position of an organism within a food chain/web, based on what level it feeds at
the order of trophic levels
primary producer → primary consumer → secondary consumer → tertiary consumer → quaternary consumer
apex predator
the predator at the top of the food chain/web (nothing eats them)
trophic transfer efficiency (TTE)
- measurement of how efficient the transfer of energy is from one trophic level to the next, often measured by biomass
- averages 10% across most trophic levels
- affected by endothermy (endotherms waste energy to produce heat) and diet
- limits the number of trophic levels to five
energy vs. nutrient flow throughout the ecosystem
nutrients cycle through the ecosystem
- primary producers turn inoragnic carbon (and nitrogen) into organic forms
- consumers eat producers (or other consumers) to gain access to said nutrients
- decomposers return carbon and nitrogen to inorganic forms, restarting the cycle
energy doesn’t cycle through the ecosystem
- new energy must be harvested by producers to sustain the ecosystem
- energy can come from the Sun (photosynthesis) or chemical reactions (chemosynthesis)
- energy can only move in one direction through the ecosystem, and much of it is lost at each trophic level (via heat or work)
trophic pyramid
shows the biomass or productivity at the various levels within the food web
trophic period
relative amounts of energy or bionass in each trophic level
aquatic vs. terrestrial trophic pyraminds
aquatic trophic pyramids are often inverted, due to the low biomass of algae
primary production
production of organic compounds from CO2 through photosynthesis
flow chart of energy vs. nutrient flow throughout the trophic levels
energy flow (one-way)
- Solar energy is absorbed by primary producers.
- Primary consumers (herbivores) obtain energy from primary producers.
- Upper consumers (secondary, tertiary, quarternary) obtain energy from lower consumers.
- Producers and consumers emit energy through poop and/or decomposed matter into “detritus”.
- Decomposers obtain little energy from detritus.
- Energy is released as heat at every trophic level.
nutrient flow (cycle)
- Primary consumers (herbivores) obtain nutrients from primary producers.
- Upper consumers (secondary, tertiary, quarternary) obtain nutrients from lower consumers.
- Producers and consumers emit nutrients through poop and/or decomposed matter into “detritus”.
- Decomposers obtain nutrietns from detritus.
- Primary producers obtain nutrients from microorganisms, completing the cycle.
decomposers vs. detritivores
- decomposers break down detritus into inorganic matter to be used by primary producers (e.g. fungi, bacteria)
- detritivores consume detritus/break it down into smaller, more manageable pieces for decomposers (e.g. vultures)
primary productivity
the rate at which energy is converted by autotrophs to organic substances (often by photosynthesis)
three things that control photosynthetic rate
- water
- nutrient availability
- sunlight
Liebig’s Law of the Minimum
primary production is limited by the nutrient that is least available (if not water, this is often nitrogen)
nutrient limitations in three different ecosystems
- forests: limited by nitrogen
- open oceans: limited by phosphorus and nitrogen
- coastal marines: limited by iron
solar hours across the Earth
all parts of the Earth have equal solar phours, but the way these hours are divided varies by latitude
the equinoxes and solstices in the Northern Hemisphere
- Winter solstice in December represents the shortest day of the year; this is the start of winter.
- As time goes on, the days get gradually longer.
- Spring equinox in March represents the moment when day and night are both approximately 12 hours long; this is the start of spring.
- As time goes on, the days get gradually longer.
- Summer solstice in June represents the longest day of the year; this is the start of summer.
- As time goes on, the days get gradually shorter.
- Autumnal equinox in September represents the moment when day and night are both approximately 12 hours long; this is the start of fall.
- As time goes on, the days get gradually shorter.
- This cycle repeats throughout the year; the length of days during the solstices are reverse for the Southern Hemisphere (i.e. longest day in the winter solstice, shortest day in the summer solstice).
distance from the equator and day length
- the closer to the equator, the less variation between day length (i.e. the equator has approximately 12 hours of daylight during the solstices and equinoxes)
- the further from the equator, the more variation between day length (e.g. the North Pole has 24 hours of daylight during summer solstice and 0 hours of daylight during winter solstice)
insolation
the amount of solar radiation reaching a given area of the Earth, often measured as energy per unit area or energy per unit time
the impact of latitude on insolation
- solar angle varies with latitude, because the Earth is a flattened sphere
- insolation decreases as you move further from the equator
- at the equator, temperatures are high and sunlight is concentrated
- at the poles, temperatures are low and sunlight is spread out
uplift vs. subsidience
- uplift: as the Earth is heated, air is warmed; warm air is less dense, and hence rises and moves towards the ITCZ
- subsidience: as warm air moves away from the ITCZ, it cools down and descends back to the Earth
insolation and wind currents
- Insolation warms the Earth.
- Warm air rises due to uplift.
- This creates a band of low pressure that causes surface winds to move towards the ITCZ.
- As hot air rises, it holds less water, creating tropic rains.
- High elevation air moves away from the ITCZ, cools, and descends back to Earth (subsidience), creating high pressure bands.
ITCZ
the intertropic convergence zone is where Hadley cells meet, and it moves across the planet (furthest north at summer solstice, furthest south at winter solstice)
the creation of deserts
subsidience within Hadley cells create deserts because descending air warms up, absorbs the water from the Earth, and generates arid climates
three circulation patterns
- trade winds (Hadley cells): surface winds in the tropics that are driven by uplift within the ITCZ; they blow east to west
- easterlies (Polar cells) surface winds in polar regions that are driven by subsidience near the poles; they blow east to west
- westerliest (Ferrell cells) surface winds that are driven by other cells to either cells on either side of them; they blow at mid-latitudes from west to east
insolation and seasonality in Toronto
- Toronto has the highest isolation during the summer solstice
- Toronto has the lowest isolation during the winter solstice
The Earth is furthest from the sun in ________, and closest in ________.
July, January
the impact of the Earth’s elliptical orbit in the Northern hemisphere vs. the Southern hemisphere
- in the Northern hemisphere, winters are warmer and summers are cooler than if the orbit was circular
- in the Southern hemisphere, winters are colder and summers are warmer than if the orbit was circular
- the Earth’s orbit can weaken seasonal changes (i.e. Northern hemisphere) or enhance them (i.e. Southern hemisphere)
the two things that influence seasonality
- the tilt of the Earth (major influence)
- the elliptical orbit of the Earth (minor influence)
the impact of biodiversity on primary production
- as species biodiversity increases, plant biomass also increases
- as species differ in resource usage, more species mean more efficient use of said resources (niche complementarity)
- adding limiting nutrients can increase primary production, which increases biodiversity
- herbivores can keep dominant plants in check
- plants respond to grazing with prey compensation
prey compensation in grazed plants
- grazers don’t kill their prey (plants), so the prey can respond to damage by reallocating resources to repair the damage
- humans take advantage of this: pruned plants grow fuller (i.e. more foliage and fruit)
