chapter 13

Question 1

energy entering ecosystems and transferred between roganisms.

Answer 1

-ultimate source of energy for animals in an ecosystem is sunlight.
-converted to chemical energy during photosynthesis and transferred between organisms as food. x

Question 2

food chain

Answer 2

illustrates trophic relationship between organisms.
energy/biomass is transferred from one organism to the next
trophic level is based on position in the food chain.
-organisms may have different trophic levels in different food chains or in different stages of their life.

Question 3

producer
primary
secondary
tertiary consumer

Answer 3

producer- produce food using light energy from the sun during photosynthesis.
primary consumer- herbivore
eats producer

secondary consuer- usually carnivore
eats primary consumer

tertiary consumer- predator, but can be scavengar or parasites.
carnivoreso[[\

Question 4

saprobions/decomposers

Answer 4

-usually fungi or bacteria that break down dead/decomposing material into valuable minerals so that they can be used by the plant.

Question 5

food chains
food webs

Answer 5

food webs- organisms do not feed on a single food source. within a habitat, many food chains are interlinked to form a food web

food chain- produces, primary, secondary, tertiary and quaternary consumers and saprobiens.

Question 6

what is biomass?
what are the units of biomass

Answer 6

total mass of living material in given area at a specific time.
mass per unit area- often grams per metre squared.

Question 8

biomass and its units/g

Answer 8

biomass- total dry mass of living material in a given area at a specifici time
units- mass per given area

Question 9

How to calculate remaining biomass of an organism.

Answer 9

total mass of carbon or dry mass of tissue per given area.
per given area- so it can be compared for organisms of different sizes
dry mass- mass without water.

Question 10

gross primary production

Answer 10

total chemical energy stored in plant biomass in given area of volume/total energy resulting from photosynthesis.

Question 11

net primary production

Answer 11

total chemical energy stored in plant biomass after losses from respiration have been taken into account.

net primary production= gross primary production- losses from respiration

Question 12

net production of consumers/energy available from animals to create new biomass

Answer 12

chemical energy from ingested food- chemical energy lost through faeces and urine +respiratory losses.

Question 13

units of productivity

Answer 13

kJ/ha/per year

kJ- unit of energy
ha- unit of area- standardise measurements- to allow different environments to be compared as they vary in size

per year- takes into account the impact of seasons- rain, light and heat.

Question 14

why is the nitrogen cycle required?

Answer 14

78% of the air is nitrogen but it cannot be absorbed by plants and animals directly via gas exchange
-triple covalent bond in nitrogen is difficult to break

microorganisms convert nitrogen to nitrogen containing compounds to be absorbed by plants and animals.

Question 15

stages of the nitrogen cycle

Answer 15

ammonification
nitrification
nitrogen fixing
denitrification.

Question 16

nitrogen fixing

Answer 16

either naturally through lightning or industrial processes e.g. the haber cycle

mutualistic ntirogen fixing bacteria- produce nitrogen containg compoiunds
plant gets amino acids from bacteria and bacteria gets carbohydrates from the plant.

free living nitrogen fixing bacteria- reduce nitrogen to ammonia, which is used by plants to make amino acids
when bacteria die, they release nitrogen compounds back into the soil

Question 17

ammonification.

Question 18

denitrifcation

Answer 18

denitrifying bacteria in the soil reduce nitrate ions into nitrogen gas.
reduces availability of nitrate ions for plant use
bacteria need anaerobic conditions.

Question 19

nitrifiation

Answer 19

nitrifying bacteria in the soil oxidise ntirogen gas into nitrite ions
nitrite ions oxidised into nitrate ions
nitrate ions can be used by plant to produce nitrogne containing compounds
bacteria require well aerated soil.

Question 20

why is the phosphate cycle important?

Answer 20

phosphate is found in:
ATP
DNA/RNA
phospholipid bilayer

so the cycle is an essential part of life

Question 21

where is phosphorus found?

Answer 21

-unlike in the carbon and nitrogen cycle, phosphorus is not a gas so is not found in the atmosphere

• phosphate ions are found in their mineral form in sedimentary rocks.

Question 22

mycorrhizae

Answer 22

fungal associations between plant roots and beneficial fungi

Question 23

how do mycorrhizae benefit plant growth?

Answer 23

increased surface area of fungi for water and mineral absorption
mycorrizhae act as like a sponge, keeping water and mineral ions near the roots

so the plant is more drought resistant and absorbs more inorganic ions.