Ecosystems

Question 1

How to determine dry mass of a sample

Answer 1

-Dry material by heating to 100c evaporates the water
-weight mass continue heating until no further change in mass
-record dry mass

Question 2

Measuring energy in biomass

Answer 2

-chemical energy stored in biomass can be measured by calorimetry
-weight sample of dry material
-burn in pure o2 within a sealed chamber
-bomb surrounded by water bath
-combustion causes temp increase
-as we know how much energy is needed to increase the of of 1g by 1C if we know the volume of water and temp rise we can calculate energy release

Question 3

Ploughing leads to increase in crop yield

Answer 3

-increase level of o2 for nitrifying bacteria
-replaces nutrients for ammonification
-decreased denitrifying

Question 4

Phosphorus cycle

Answer 4

-exists as phosphate ions in sedimentary rocks
-rocks in seas and uplifted to surface
-weathering dissolves ions becoming available for absorption by plants
-plants incorporate into biomass
-animals ingest plants
-excess excreted and many accumulate in waste material
-dead matter broken down by saprobionts so ions back into water/soil

Question 5

Nitrogen cycle

Answer 5

N2> NH3> nitrites > nitrates >plant protein > animal protein> NH3

Question 7

Types of competition

Answer 7

-Intraspecfic: between individuals of same species which occupy the same niche
-interspecific: between individuals of different species whose niches overlap