ecosystems Flashcards
define ecosystem
all the interacting living organisms and the non-living conditions in an area
define community
all the populations of living organisms in a particular habitat
define habitat
the natural home or environment of an animal, plant or other organism
define population
a group of organisms of the same species that live in the same place at the same time
define species
the smallest and most specific taxonomic group. can breed to produce fertile offspring
define ecology
the study of relations of organisms to each other and their physical surroundings
what is meant by “ecosystems are dynamic”
dynamic ecosystems are constantly changing
define biotic factor
the living components of an ecosystem
define abitotic factor
non-living conditions of a habitat
e.g rainfall, temperature, light intensity
define edaphic factor
factors to do with soil
define food web
many interconnected possible routes of energy and biomass through an ecosystem
define food chain
a single possible route of energy and biomass through a food web
define trophic level
each stage in a food chain
what do the arrows represent in a food web
direction of energy flow
define heterotroph
another name for a consumer
define consumer
organisms that obtain their organic molecules and energy by feeding on other organisms
define primary consumer
animals that eat producers in a food chain
define secondary consumer
animals that eat primary consumers in a food chain
define tertiary consumer
animals that eat secondary in a food chain
define herbivore
animals that eat plants - primary consumers
define carnivore
animals that eat other animals - secondary consumer or higher
define omnivore
animals that eat both plants and other animals
define detritivore
animals that feed on detritus (dead and decaying material)
define decomposer
an organism that feeds on dead organic matter, turning the organic molecules into inorganic ions
role of detritivores in food webs
speed up decay by breaking down dead material into smaller pieces, increasing the surface area of decomposers to work on
role of decomposers in food webs
decomposers break down dead organisms releasing nutrients back into the ecosystem
define biomass
the mass of living material present in a particular place or in particular organisms
define dry mass
the mass of living material remaining once all the water has been removed
why is dry mass is a better indicvator of biomass than fresh mass
dry mass is a more reliable measure of mass as it exculdes fluctuating water concentrations
how to calculate the dry mass of each trophic levels in a food chain
organisms killed and placed in an oven until water has all evaporated - 2 identical mass readings
how to measure the energy content of organic matter
using calorimeter - burn matter and measure temperature rise of water
suitable units in a terrestrial ecosystem
gm^-2 grams per metre squared
suitable units in an aquatic ecosystem
gm^-3 grams per metre cubed
how does a pyramid of numbers represent data about an ecosystem
show number of each organism in a food chain - not always pyramid shaped
easy to count, hard to draw due to variation
how does a pyramid of biomass represent data about an ecosystem
shows mass at each trophic level in a food chain - almost alwats pyramid shaped
easier to draw, might be skewed due to time of year or reproduction rate
how does a pyramid of energy represent data about an ecosystem
shows energy available from each level - always pyramid
hard to calculate
suitable units for the energy at each trophic level in a food chain
kJm^-2yr^-1 Kilojoules per metre squared per year
how is energy transferred from one trophic level to the next
transferred between trophic levels as organisms feed on eachoteher.
only a small proportion of the food is converted into a new tissue and therefore only a small proportion of the energy is available for next level to eat
define ecological effiency
the efficiency with which energy or biomass is transferred from one trophic level to the next
energy or biomass available after the transfer / energy or biomass available before the transfer x 100
why is 1-3% of sunlight is converted into chemical energy in producers
not all energy used for photosynthesis - 90% reflected, some transmitted, some is unusable wavelength
other limiting factors eg water availability
proprtion of energy lost as it is used for photosynthetic reactions
define gross production
total solar energy that plants convert to organic matter
define net production
the energy converted into biomass and therefore available to the next trophic level
define respiratory losses
energy used in respiration so not available to next trophic level
define primary production
generation of biomass in a producer
define secondary production
generation of biomass in a consumer
why consumers convert only a small amount of the biomass
not all biomass eaten
energy transferred to environment - movement and respiration
some parts eaten but indigestible - lost as faeces
some energy lost from animal in excretory matierals
why does biomass decreases at each trophic level in a food chain
each level receives less energy than the level before due to energy losses such as in respiration
why are food chains with more than 4 trophic levels rare
not enough energy available as biomass to sustain another tier of organisms
how have humans manipulated energy transder in farming to our advantafe
provide abiotic conditions needed ot thrive
remove competition from other species
remove threat of predators
minimise trophic levels so least amount of energy is lost
importance of decomposers
decomposers break down the organic matter into small inorganic molecules that can then be used by producers
importance of detritivores
speed up decay process by breaking down organic material into smaller pieces
define nitrogen fixation
conversion of nitrogen gas to ammonium compounds
define nitrification
conversion of ammonium compounds into nitrites and nitrates
define denitrification
conversion of nitrates into nitrogen gas
define ammonification
conversion of nitrogen compounds in dead organic matter or waste into ammonium compounds by decomposers
microorganisms involved in the nitrogen cycle
nitrogen fixing: rhizobium
nitrifying: nitrosomonas (ammonia to nitrites)
nitrobacter (nitrires to nitrates)
dentrification: pseudomonas dentrificians (nitrates to nitrogen)
why does co2 levels vary throughout time
rate of photosynthesis, so rate of use of co2 fluctuates with light intensity.
at night - co2 levels are higher as respiration continues but photosynthesis doesn’t.
co2 levels lower in summer - more light = more photosynthesis
why have co2 levels increased over last 200 years
industry - increased burning of fossil fuels
deforestation - fewer large areas of trees - less photosynthesis removed
how do scientists gather data about co2 levels thousands of years ago
looking at ice at poles that formed 1000s of years ago but has never melted. - air bubbles trapped in ice
define succession
progressive replacement of one dominant type of species or community, until climax community is established
define primary succession
occurs on land that has been newly formed, no soil or organic material to begin with.
define secondary succession
occurs on land where soil is present but contains no plant or animal species
define deflected succession
when the direction of succession is affected by farming or other human activities
define pioneer species
the first organisms to colonise an area
define sere
the steps in succession
define climax community
final stage in succession, where community is in a stable state
define plagioclimax
stage in succession where artificial or natural factors prevent natrual climax community from forming
adaptations species have for being pioneer species
produce large number of seeds/spores to spread
seeds that germinate rapidly
able to photosynthesise
tolerance to extreme environments
ability to fix nitrogen from atmosphere - adds to mineral content of soil
describe effect of pioneer species on envrionment
if they die, their organic matter makes the environment more able to support other species.
describe how conditions of soil change as succession occurs.
weathering of bare rock produces particles that form the basis of soil.
pioneer species die and decompose = release organic product into soil
why does succession occur
result of changes to the environment, causing plant and animal species to change
define dominant species
most abundant species in an ecosystem
describe change in niche number and number of species as succession progresses
niche number and biodiversity increases as succession continues.
niche - role organism plays.
as succession continues, more organisms available to eat/be eated
biodiversity can dip as climax community forms if dominant species outcompetes others
why secondary succession is likey to occur more quickly than primary succession
soil is already present so time not spent eroding rock to form it
why deflected succession might occure
grazing and trampling of vegetation
removing existing vegetation to plant other crops
burning to clear forests - often leads to increase of biodiversity - nutrtient-rich ash
define lithosphere
plant succession that begins life on newly exposed rock surface
define psammosere
succession that began life on newly exposed coastal sand
define halosere
succession in a saline environment
define hydrosere
succession which occures in an area of fresh water
how can the abundance of plants be estimated
sampling with quadrats then multiplying up to size of whole area
what is capture-mark-recapture and how to estimate pop. size with it
capture as many as possible and mark them
reslease and recapture as many as possible
proportion marked will be the same as for the entire population
lincoln index to estimate the population size of a species
pop size = number marked x numver recaptured / number recaptured marked
what are the assumptions made when using capture-mark-release-recapture
population is closed - no immigration or emmigration
no deaths between samples
marked organisms must mix completely with the rest of the population between sampling.
