2.2 Communities and ecosystem

what can the feeding relationships in a system be modelled using

food chains, food webs and ecological pyramids

what is a community

a group of populations living and interacting with each other in a common habitat

what is an ecosystem

a community and the physical environment it interacts with

what is respiration

the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy

what is the word equation for respiration

glucose + oxygen -> carbon dioxide + water

what do most primary producers do

convert light energy into chemical energy through the process of photosynthesis

What is the word equation for photosynthesis?

Carbon dioxide + water -> glucose + oxygen

what are most producers

plants or algae

what do ecological pyramids include

pyramids of numbers, biomass and productivity and are quantitative models and are usually measured for a given area and time

what is bioaccumulation

the build-up of persistant/non-biodegradable pollutants within an organism or trophic level because they cannot be broken down

what is biomagnification

the increase in concentration of persistent or non-biodegradable pollutants along a food chain

what does a community contain

all the biotic components of a habitat

what must all living organisms do to get energy to survive

respire

what are the life processes

movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition

what are the two types of respiration

aerobic and anaerobic

in what form is much of the energy from respiration released as

heat energy

what do green plants do

convert light energy into chemical energy through photosynthesis

is photosynthesis a transfer or a transformation

transformation

what do leaves contain that allow photosynthesis to occur

chloroplasts and chlorophyll

what can plants do to glucose to create proteins

nitrogen and sulphur

what can plants do to glucose to make fatty acids and lipoproteins

rearrange carbon, hydrogen and oxygen and add phosphorous

what is the waste product of photosynthesis

oxygen

how does water reach the leaves from the roots

via transpiration

what is the compensation point

The level of light intensity at which the rate of photosynthesis exactly matches the rate of respiration.

when does the compensation point usually occur

at dawn or dusk

where does almost all energy on the earth come from

the sun

what is a food chain

the flow of energy from one organism to the next

what does a food chain show

the feeding relationships between species in an ecosystem

how do food chains usually start and end

with a primary producer and with a top carnivore

what is the most common type of producer

Autotrophs, which make their own food from carbon dioxide using water and energy from the sun

what do chemosynthetic organisms do

make their own food from other simple compounds found in deep oceans

heterotrophs

feed on autotrophs and other heterotrophs to obtain energy

what trophic level do primary producers occupy

1st

what is the function of primary producers

to provide the energy requirements of all the other trophic levels, habitat for other organisms, supply nutrients to the soil, bind the soil/stop erosion

what trophic level do primary consumers occupy

2nd

what is the function of primary, secondary and tertiary consumers

to keep each other in check through negative feedback loops, they also disperse seeds, pollinate flowers, remove old and diseased animals from the population

what trophic level do secondary consumers occupy

3rd

what trophic level do tertiary consumers occupy

4th

what is the function of decomposers and detritivores

to provide a crucial service to the ecosystem, break down dead organisms, release the nutrients back into the cycle, control the spread of diseases

give two examples of decomposers

bacteria and fungi

give four examples of detritivores

snails, slugs, blow fly maggots, vultures

what is the main limitation of a food chain

they can only illustrate a direct feeding relationship between one organism and the other in a single hierarchy

what are food webs made of

a complex network of interrelated food chains

what animals are the top predators of the tundra

wolves

what do wolves prey on

caribou and other large herbivores

why do otters live near rivers and lakes

so they can feed on fish

what are the smallest predators in the tundra

shrews

why are large herbivores and carnivores in the tundra dependent on a migratory way of life

the primary production of the tundra is not sufficient if only small areas are considered

what are ecological pyramids

graphical models of the quantitative differences between amounts of living material stored at each trophic level of a food chain

what is the main advantage of a pyramid of numbers

it's a simple, easy method of giving an overview and is good at comparing changes in population numbers

what does a pyramid of numbers show

the number of organisms at each trophic level per unit area

what are the disadvantages of a pyramid of numbers

all organisms are included, regardless of their size, does not allow for juveniles or immature forms, numbers can be too great to represent accurately

what does a pyramid of biomass show

the biomass at each trophic level

what is biomass

the quantity of dry organic material in an organism, a population or a particular trophic level

what are the units of a pyramid of biomass

units of mass per unit area

give an example where a pyramid of biomass isn't pyramid shaped

in oceanic ecosystems where the producers are phytoplankton as phytoplankton reproduce fast buy are present only in small numbers at any one time

what are the advantages of a pyramid of biomass

they overcome some of the problems of pyramids of numbers

what are the disadvantages of pyramids of biomass

only use samples from populations so it is impossible to measure the biomass exactly, organisms must be killed to measure dry mass, the time of year affects the result

what does a pyramid of productivity show

the rate of flow of energy or biomass through each trophic level

why are pyramids of productivity always pyramid shaped

they must follow the second law of thermodynamics

what do pyramids of productivity show

the rate of flow of energy or biomass through each trophic level

what are the advantages of a pyramid of productivity

most accurate system, shows the actual energy transferred and allows for the rate of production, allows for comparison of ecosystems based on relative energy flows, pyramids are not inverted

what are the disadvantages of a pyramid of productivity

it is very difficult and complex to collect energy data as the rate of biomass production over time is required, there is still the problem of assigning a species to a particular trophic level when they may be omnivorous

give an example of a pesticide that decomposes into harmless chemicals once they are sprayed

glyphosate

between 1932 and 1968, how much mercury and methylmercury was released into minamata bay

24 tonnes

why is to top trophic level in a food chain the most vulnerable to change

they have a limited diet so a change in their food prey has a knock on effect, their population numbers are low because of the fall in efficiency along a food chain so their ability to withstand negative influence is more limited than species with larger population