6.3.1 Ecosystems

define ecosystem?

• all the organisms living in a certain area and all the non-living factors there

define biotic factors?

the living features of an ecosystem

define abiotic factors?

the non living features of an ecosystem

state biotic factors?

• competition

• food

• territory

• mating

state abiotic factors?

• temperature

• light

• ph

• water and humidity

• oxygen availibility

  • edaphic factors e.g soil

name 3 types of ecosystem?

rock pool, playing field, large tree

state the main route which energy enters an ecosystem?

photosynthesis

define producer?

makes food on its own

In what form do plants store energy as?

biomass

define biomass?

the mass of living material present in a particular place or organism

state the term used to describe energy transferres through ecosystems?

biomass transfer

state 2 methods of measuring biomass?

• mass of fresh material pre4sent

• dry mass

what do food chains show?

simple lines of energy transfer

what do food webs show?

many food chains in an ecosystem and how they overlap

is all energy transferred to the next trophic level?

• no, some is lost:

  • e.g plants cannot use all the light energy which reaches the leaves as some sunlight may ht parts of the plant which cannot photosynthesize e.g bark

  • some parts of food are indigestible so pass organisms and come out as faeces

define net productivity?

the amount of energy available to the next trophic level

net productivity equation?

Net productivity = Gross productivity - respiratory loss

state the name of the element all organisms need to make essential compounds?

carbon

what does the carbon cycle represent?

how carbon moves through living organisms and the non living environment

why do plans and animals need nitrogen?

to make proteins and nitric acids

what do plants and animals need to transform nitrogen into a form which they can use?

they require bacteria to transform it into nitrogen compounds

what does the nitrogen cycle represent?

how nitrogen is converted into a useable form then passed on between different living organisms and the non living environment

what 4 processes involving bacteria does the nitrogen cycle consist of?

• nitrogen fixation

• ammonification

• nitrification

• denitrification

what occurs in nitrogen fixation?

• nitrogen gas is turned into ammonia by Rhizobium and Azotobacter

where are Rhizobium found?

in root nodules

how does Rhizobium form a mutualistic relationship with root nodules?

• they provide the plant with nitrogen compounds and the plant provides them with carbohydrates

where are azotobacter found?

in the soil

do azotobacter form a mutualistic relationship with plants?

no

define ammonification?

• when nitrogen compounds from dead organisms are turned into ammonia by decomposers which goes on to form ammonium ions

• animal waste also contains nitrogen compounds which are turned into ammonia by decomposers and bo on to form ammonium ions

define nitrification?

when ammonium ions in the soil are changed into nitrogen compounds that can be then be used by the plants

state the first step of nitrification?

• nitrifying bacteria called nitrosomonas change ammonium ions into nitrites

state the second step of nitrification?

• the other nitrifying bacteria called nitrobacter change nitrites into nitrates

define denitrification?

when nitrates in the soil are converted into gas by denitrifying bacteria

when does denitrification occur?

this happens under anaerobic conditions when soils become waterlogged