quiz 3 Flashcards
disturbance
an event that changes a community, removes organisms from the area, and alters resource availability
why does succession occur?
- the result of changes induced by vegetation itself
- early-arriving & later arriving species may be linked in 1 of these processes:
1. early arrivals facilitate the appearance of later species by modifying the environment so it is less favourable for the success of existing plants and more favourable for the invasion and growth of other plants
2. may inhibit the establishment of later species
3. may tolerate later species but have no impact on their establishment
what are the 3 main changes in community structure that categorize ecological succession
- general increase in community diversity
- general increase in abundance of organisms
- general change in size and longevity, decrease in birth rates
primary succession
- no soil exists
- pioneer species : prokaryotes, protists, fungi
- over hundreds-thousands of years
secondary sucession
- begins where soil remains after a disturbance
- earliest recolonizers are seeds ( by wind and animal dispersion )
- about 50-200 yrs
compare and contrast primary and secondary succession, specifically identify the similarities between the between processes, the conditions that exist at the beginning of each type of succession, the potential sources of new species in each and the time frame over which each type of succession occurs
similarities:
- natural ecological processes = gradual development of an ecosystem over time
- increase in biodiversity = diversity increases as ecosystem progresses and develops
- involves pioneer species = both processes begin with pioneer species that help modify the environment
- community formation = succession leafs to the establishment of a stable and mature ecosystem
differences:
starting conditions:
- primary succession begins in an area where no previous ecosystem existed, like bare rock. Environment is harsh, lacking soil and organic matter
- secondary succession occurs in areas where an ecosystem previously existed but was disturbed. there is soil present and potentially organisms that survived the disturbance
sources of new species:
primary - arrives through wind, water, and animal dispersal. lichens and mosses are often the first to colonize and form soil
secondary - species may regenerate from seeds, roots, spores that survived in the soil
time frame:
primary - hundreds to thousands of years, soil formation must occur before plants and animals can establish
secondary - proceeds more quickly, about 50-200 years, since soil is already present and the ecosystem can recover, not be discovered
why are pioneer species replaced by other species during succession?
- changes in environmental conditions
- alter soil properties, permitting new plant species to grow, altering environment to make it suitable for larger, more competitive species to establish
- when they die they enrich the soil with nutrients
lichens as pioneer species
- fixing carbon and nitrogen levels
- breaks down rock and exposes minerals
- traps windblown soil
- retains water
ecosystem
the community of organisms in an area and the physical factors with which they interact
biomes
major types of ecosystems
occupies broad geographic areas
biosphere
sum of the planet’s ecosystems
climate
the long term prevailing weather conditions
- the 4 major abiotic components of climate are:
-> temperature, precipitation, sunlight, wind
macroclimate
global, regional, and landscape climate patterns
microclimate
consists of very fine local patterns (like under a fallen log)
latitudinal variations in climate
global climate patterns are determined by solar energy and earth’s movement
- the angle of sunlight hitting the earth affects its intensity
- temperature variations determine patterns of evaporation and circulation of air and water
global air circulation and precipitation
- water evaporates in the tropics, and warm wet air masses flow from tropics to the poles
- rising air masses release water and cause high precipitation, esp in the tropics
- cooling trade winds flow east to west in the tropics
- prevailing westerlies blow from west to east in temperate zones
terrestrial biomes
i) forests : tropical rainforest, coniferous forest, temperate deciduous
ii) savanna, temperate grasslands, chaparral
iii) desert, tundra
ecotones
areas where terrestrial biomes blend into each other
- no sharp boundaries
- could be wide or narrow
major aquatic biomes can be characterized by
- physical environment
- geological features
- chemical environment
- photosynthetic organism
- heterotrophs
- marine biomes have a salt concentration of 3%, freshwater less than 0.1%
aquatic biomes
- open oceaen
- coral reefs
- wetlands
- estuaries and intertidal
- lakes, streams, rivers
what is primary production?
the amount of light energy converted into chemical energy (in Joules) by autotrophs during a given time period
-> sets the spending limit for an ecosystem’s energy budget
explain the difference between gross primary production and net primary production
gross = total primary production
net = total, minus energy used for respiration/metabolism
-»» amount of new biomass in a given time period
*** this is what is available to consumers
which of the terrestrial biomes have the highest and lowest NPP? include abiotic conditions of each
highest:
Tropical Rainforest
- warm temperature
- high precipitation rates
- abundant sunlight, warm climate
=> optimal for photosynthesis = high biodiversity and productivity
lowest:
Desert
- minimal precipitation and high temperature => limits plant growth and water accessibility
- nutrient poor soils
which of the aquatic biomes have the highest and lowest NPP? include abiotic conditions of each
highest:
Coral Reefs
- warm, shallow waters
- abundant sunlight
- constant nutrient cycling
lowest:
Deep Open Ocean
- limited nutrients
- minimal sunlight
which biotic factors are similar between the highest production terrestrial and aquatic biomes
Coral Reeds and Tropical Rainforests:
- High biodiversity
- vast number of plant, animal, and microbial species - abundance in primary producers
- tr; lots of dense trees = high photosynthesis
- cr; symbiotic algae in corals = photosynthesis - efficient nutrient cycling
- mutualistic relationships
which biotic factors are similar between the lowest production terrestrial and aquatic biomes
Desert and Deep Ocean
- low biodiversity
- few species have adapted to the extreme conditions of both environments - Sparse Primary Production
which factors limit production in aquatic and terrestrial ecosystems?
carbon
oxygen
nitrogen
phosphorus
diffusion
movement from high to low concentration
facilitated diffusion
diffusion with transport protein channels to help the molecule through the membrane
channel proteins
water, lipid insoluable components that allow molecules and ions to cross
carrier proteins
when molecules are too large to fit the protein channel, undergoes a subtle change in shape
osmosis
diffusion of water across a semi-permeable membrane
- hypo wants to be hyper,, hypertonic solutions disperse into hypotonic solutions
- isotonic = equalized
tonicity
ability of a solution to cause cells to gain or lose water
plants in hypertonic solution
losers water, shrivels
plants in hypotonic solution
water enters
good!!!!
plants in isotonic solution
no water movement -> plant wilts
active transport
substances moving against the concentration gradient
- uses energy
- transport protein required
nutrient flow
the movement and cycling of essential elements throughout diff components of the ecosystem
1. uptake by producers - plants absorb nutrients from soil, water, air and sunlight to make organic matter through photosynthesis
2. transfer through the food chain - herbivores consume plants, transferring nutrients to their bodies, carnivores eat herbivores to continue the flow
3. decomposition and recycling - when organisms die, decomposers break down their bodies and release nutrients back into the soil and water for reuse by plants
4. geochemical cycling - some nutrients like carbon and nitrogen cycle through the atmosphere through soil and water
continuous movement of nutrients maintains ecosystems and supports life at all levels
compare and contrast the flow of energy vs flow of nutrients through an ecosystem
similarities:
- both essential for life
- both involve producers, consumers, decomposers
- both depend on external inputs
differences
- sources -> energy comes from sunlight, nutrients comes from earths reservoirs
- direction -> energy is a one way flow, nutrients is cyclic (continuously recycled)
- loss -> energy lost as heat, nutrient “loss” is retained and reused within the ecosystem
- movement -> energy moves through food chains but ends, nutrients moves through chains and is returned to producers through decomposistion
why do nutrients cycle more quickly in warmer and wetter ecosystems? how does this affect NPP?
- faster decomposition
— higher temps and moisture levels speed up microbial activity, causing organic matter to break down more rapidly - increased biological activity
— warmth and moisture promote plant growth and microbial activity, enhancing nutrient uptake and recycling
It increases NPP because plants have more access to essential nutrients, leading to high rates of photosynthesis and growth
why do nutrients cycle more quickly in aerobic than anaerobic aquatic ecosystems?
- more efficient decomposition
- faster chemical reactions
- better nutrient circulation
how does agriculture lead to nitrogen enrichment of terrestrial and aquatic ecosystem
- fertilizer use
— synthetic fertilizers add large amounts of nitrogen to soil, exceeding what plants can absorb - livestock waste
— manure from forms releases nitrogen into soil and water systems - crop residue and nitrogen-fixing plants
— legumes fix atmospheric nitrogen, increasing soil nitrogen levels
how nitrogen enrichment would change an oligotrophic lake
oligotrophic lakes are nutrient poor and low productivity. nitrogen enrichment would cause
abiotic:
- increased nutrient levels (n and po4)
- increased turbidity (reduced water clarity)
- lower oxygen levels due to increased decomposition
biotic:
- increased algal and cyanobacteria growth
- decrease in fish and other aerobic organisms due to oxygen depletion
- shift in species composition, favouring organisms that thrive in nutrient rich environments
carbon reservoirs humans use for fuel and energy and impact on atmospheric carbon
major reservoirs :
fossil fuels - formed from ancient organic matter
forests - wood burning releases stored carbon
soil and peatlands - disturbance and agriculture release stored carbon
why this increases atmospheric carbon
- burning fossil fuels releases CO2 that was stored underground
- deforestation removes carbon sinks, reducing carbon absorption
- soil disturbance releases CO2 previously stored in organic matter
how increased atmospheric carbon influences primary productivity
- short term boost - more co2 can enhance photosynthesis in some plants, increasing primary productivity
- long term negative effects - warm temps cause droughts, reducing productivity,, ocean acidification (from dissolved co2) harms phytoplankton, reducing marine productivity
which structure in roots, stems and leaves facilitate gas exchange in vascular plants
root hairs
- thin extensions of epidermal cells that increase surface area for gas exhange
- oxygen from the soil diffuses into root cells for cellular respiration while co2 diffuses out
- epidermis is very permeable to water
- accounts for much of the surface area of roots
- facilitated by mycorrhizae
lenticels
- on wood stems, small spongy opening that allow direct gas exchange
stomata
- tiny openings that regulate gas exchange
- guard cells control stomatal opening and closing
- can be on upper and or lower surfaces of leaves and sometimes on stems
xerophytes
plants adapted to arid climates that have leaf modifications that reduce the rate of transpiration:
- thick cuticle
- many xerophytes have a thicker waxy cuticle on leaves and stems, reducing water loss by preventing evaporation - reduced or modified leaves
- small, needle like or spiny leaves to reduce surface area for transpiration - sunken stomata
- rolled leaves
stimuli for stomatal opening and closing
generally stomata open during the day and closed at night to minimize water loss when it is too dark for photosynthesis
opening triggered by:
- light
- depletion of CO2
- internal clock, circadian rhythm
stomata close during the daytime when plants suffer water deficiency due to
- loss of turgor pressure in guard cells
- abscisic acid production in response to the water loss
mechanisms of stomata opening and closing
- changes in turgor pressure open and close stomata
turgid -> guard cells bow outward and pore opens
flaccid -> guard cells less bowed and pore closes - the result of
potassium movement in and out of cells
changes in guard cell shape - stomata open when guard cells actively accumulate potassium
transport in vascular plants
- plants can move a large volume of water from roots to shoots
- continuations of the three tissue systems throughout the plant body (dermal, ground, vascular)
transport in roots
most water and mineral absorption is root tips by root hairs
- root hairs are covered by a thin layer of water
—> epidermis is permeable to water, diffusion and active transport of minerals across the membranes
examples of sugar sources and sugar sinks
sources (sites of sugar production or storage release)
- mature leaves = performs photosynthesis
- storage organs
sinks (sites of sugar consumption or storage)
- growing tissues = young leaves, buds, flowers, developing seeds, fruits
sugar transport in plants
- sugar loading at source
— sucrose is actively loaded into sieve-tube at the source, lowering water potential - water uptake from xylem
— water moves into sieve tubes by osmosis, increasing turgor pressure - bulk flow at sink
— the pressure difference between source (high pressure) and sink (low pressure )drives phloem sap through sieve tubes - sugar unloading at sink
— sucrose moves out of sieve tubes into sink tissues - water recycled and returned to xylem
— as sugar exits, water follows by osmosis, reducing pressure at sink
mechanisms of pressure flow in phloem
- sugar loading at source
— sucrose is actively loaded into sieve-tube at the source, lowering water potential - water uptake from xylem
— water moves into sieve tubes by osmosis, increasing turgor pressure - bulk flow at sink
— the pressure difference between source (high pressure) and sink (low pressure )drives phloem sap through sieve tubes - sugar unloading at sink
— sucrose moves out of sieve tubes into sink tissues
how is sucrose loaded into sieve tube elements at the sugar source
by phloem loading:
- active transport via proton pump
- diffusion in some plants
symplastic route
water and minerals can travel through a plant by different routes, through the continuum cytosol
apoplastic route
via cell walls and extracellular spaces
endodermis
innermost layer of cells in the root cortex
- surrounds the vascular cylinder
- last checkpoint for selective passage of minerals into vascular tissue
casparian strip
blocks apoplastic transfer into the vascular cylinder
