chapter 23 - ecosystems

Question 1

what are the abiotic factors affecting ecosystem

Answer 1

light - for photosynthesis
h20 availability - photosynthesis
o2 availability - respiration
temperature - enzymes / migration
edophic ( soil) factors - type of soil/ soil pH

Question 2

what are the biotic factors affecting competition

Answer 2

competition
predation
diseases

Question 3

what are trophic levels

Answer 3

stages in food chain

Question 4

what are the tropic levels

Answer 4

producers –> primary consumers –> secondary consumers –> tertiary consumer –>

Question 5

what is biomass

Answer 5

mass of living material in an area or organism without h20

Question 6

why is h20 not considered as biomass

Answer 6

water levels fluctuate depending on the environment and times of the day so is not a true representation on amount of energy in organism

Question 7

what happens to biomass up the tropic levels

Answer 7

biomass decreases

Question 8

how is biomass measured

Answer 8

calorimeter - measures calories within organism

Question 9

how does calorimeter work

Answer 9

1)collect sample
2)kill sample
3)put in oven at 80degrees celcius to evaporate water
4) point where mass stays same is biomass

Question 10

why shouldnt you insert sample in oven at 100 degrees celcius

Answer 10

organic matter may decay so results not valid

Question 11

what are unit of biomass

Answer 11

land animals - gm^-2

ocean animals - gm^-3

Question 12

what is ecological efficiency

Answer 12

efficiency in which biomass is transferred from one tropic level to the next

Question 13

why is ecological efficiency never 100%

Answer 13

sunlight reflected
other factors affecting the photosynthesis rate
some energy used up for photosynthesis to occur
some energy lost as thermal energy through respiration
some energy lost by excretion
some parts of food not eaten

Question 14

what are agricultural ways to increase efficiency

Answer 14

keep animals indoors
keep fences to decrease movement
feed animals high energy content
vaccination
genetic engineering/selective breeding

Question 15

what are decomposers

Answer 15

feed on dead organic matter
saprophytic
secrete enzymes for external digestion

Question 16

what are detritivores

Answer 16

internal digestion
feed on dead organic matter
increase surface area on food to increase decomposition rate

Question 17

describe carbon cycle

Answer 17

1) consumers release co2 to atmosphere by respiration and producers take in co2 from atmosphere by photosynthesis
2) co2 transmitted to consumer as it eats producer
3) consumer dies and decomposers feed on organic matter releasing co2 to atmosphere
4) undigested material becomes fossil/fossil fuels
5) fossil fuels burnt for energy and combustion releases co2

Question 18

what is nitrogen used for

Answer 18

amine group for proteins

Question 19

what is nitrification

Answer 19

ammonium ion ( NH4+) turned to nitrite ( NO2-) then to nitrate ( NO3-) by oxidation

Question 20

what bacteria converts ammonium ion to nitrite ion

Answer 20

nitrosomonas

Question 21

what bacteria converts nitrite ion to nitrate ion

Answer 21

nitrobacter

Question 22

what is ammonification

Answer 22

nitrate ion and nitrate ion converted to NH4+ which is converted to ammonia ( NH3) by decomposers

Question 23

what is denitrification

Answer 23

NO3- ( nitrate) converted to N2 in by denitrifying bacteria , pseudomonas, in anaerobic conditions

Question 24

what is nitrogen fixation

Answer 24

N2 + 3H2 —– 2NH3 catalysed by nitrogenase found in bacteria such as azotobacter and rhizobium