6.5 ecosystems

Question 1

define ecosystem

Answer 1

a community of animals, plants and bacteria and its interrelationships with the environment (abiotic and biotic)

Question 2

define habitat

Answer 2

the place where an organism lives

Question 3

define population

Answer 3

all of the organisms of one species who live in the same place at the same time and can breed together

Question 4

define community

Answer 4

all the populations of different species who live in the same place and interact with each other

Question 5

explain what biotic factors are

Answer 5

living components
- producers
- consumers
- decomposers
- predation/ disease

Question 6

explain what abiotic factors are

Answer 6

non living components
- pH
- humidity
- temperature
- concentration of pollutants

Question 7

explain why an ecosystem is dynamic

Answer 7

can change
- cyclic - changes repeat with rhythm
- directional - changes are not cyclic, go in one direction
- unpredictable - no rhythm or direction, are erratic

Question 8

define biomass transfer

Answer 8

transfer of biomass from one trophic level to another

Question 9

define trophic level

Answer 9

the level at which an organism feeds in a food chain

Question 10

explain how biomass is transferred through ecosystems

Answer 10

at each trophic level = living organisms need energy to carry out life processes, respiration releases energy
biomass is lost through dead material/ organisms
biomass is less at higher levels of the food chain

Question 11

explain the pyramid of numbers

Answer 11

area of each bar is proportional to the number of individuals

Question 12

explain the pyramid of biomass

Answer 12

area of each bar is proportional to the dry mass of all the organisms at the trophic level

Question 13

how can the efficiency of biomass transfer be calculated

Answer 13

(biomass at higher trophic level or consumer/ biomass at lower trophic level or producer ) x100

Question 14

define productivity

Answer 14

the rate of production of new biomass by producers

Question 15

define gross primary productivity

Answer 15

the rate at which plants convert light energy into chemical energy through photosynthesis

Question 16

define net primary productivity

Answer 16

the proportion of energy from the sun available to enter the food chain

Question 17

explain how primary productivity can be increased

Answer 17

planting crops early/ under light banks
irrigating crops
growing in greenhouses
crop rotation
pesticides/ fungicides

Question 18

explain how secondary productivity can be improved

Answer 18

harvesting animals before adulthood
selective breeding
treating with antibiotics
zero grazing

Question 19

explain what a saprotroph is and give examples

Answer 19

enzymes are secreted to break down organic material and then the products are re absorbed
bacteria and fungi

Question 20

why is nitrogen recycled

Answer 20

inert gas
used to make proteins and nucleic acids

Question 21

what bacteria is involved in nitrogen fixing

Answer 21

rhizobium
free living bacteria - azobacter

Question 22

explain how rhizobium bacteria and free living bacteria allows for nitrogen fixation

Answer 22

on root nodules of leguminous roots/plants
nitrogen gas and H+ ions are converted into (NH3) ammonium ions
by reduction

free living in the soil
converts nitrogen gas into ammonium ions

Question 23

what bacteria is involved in nitrification

Answer 23

nitrosomonas
nitrobacter

Question 24

explain how nitrosomonas and nitrobacter allows for nitrification

Answer 24

ammonium ions are nitrified by nitrosomonas into nitrites (NO2-)

nitrites are nitrified by nitrobacter into nitrates (NO3-)

both by oxidation

Question 25

explain how denitrification occurs

Answer 25

denitrifying bacteria converts nitrates back into nitrogen gas by reduction returned to the atmosphere

Question 26

how are plants and animals involved in the nitrogen cycle

Answer 26

nitrate ions are taken up by plants animals feed on plants and digest the proteins - death and decomposition = ammonification occurs and ammonium ions returned to soil - nitrogenous excretion of animals = urea released

Question 27

explain the importance of the carbon cycle

Answer 27

carbon dioxide is respired by animals , plants and microorganisms carbon dioxide is absorbed by plants for photosynthesis microorganisms decompose dead organic waste and release carbon carbon can dissolve into oceans and be used by aquatic plants

Question 28

explain the processes in the carbon cycle

Answer 28

C02 in the air photosynthesis = taken in by plants plants fed on by animals - animals/ plants excrete/ die = humus and waste produced - decomposition returns carbon to the atmosphere death and fossilisation = of plants/animals forms fossil fuels = combustion respiration = of animals and plants returns carbon to the air

Question 29

define succession

Answer 29

progressive change in a community of organisms overtime

Question 30

define primary succession

Answer 30

succession on a newly exposed surface

Question 31

define secondary succession

Answer 31

succession on a previously colonised area

Question 32

define deflected succession and what does it result in

Answer 32

when succession is stopped or interfered with eg. mowing a lawn sub climax community = plagioclimax

Question 33

define pioneer species

Answer 33

species that begin the process of succession, colonising an area as the first living things there

Question 34

explain how succession happens

Answer 34

algae and lichens live on bare rock = pioneer community erosion of the rocks, build up of dead organisms = produces soil supports larger plants which now replace/ succeed the algae process continues until final, stable community is reached = climax community

Question 35

explain succession on sand dunes

Answer 35

pioneer species eg. sea rocket, prickly sandwort can tolerate salty, sandy conditions wind blown sand builds up forming a mini sand dune plants die and decay, nutrients accumulate dune gets bigger and more plants can colonise it eg. sea couch grass dunes become more stable process keeps going

Question 36

name the ways the abundance and distribution of a species can be measured

Answer 36

quadrats transects

Question 37

explain how to carry out sampling with a quadrat

Answer 37

can find out the number of individual species or the presence or absence of a species percentage cover is estimated randomly position the quadrats or take samples at regular distances take as many samples until the data levels off in a cumulative frequency table

Question 38

explain how transects can be carried out

Answer 38

line - at regular intervals determine the species touching the tape belt - regular intervals use a quadrat