5-

Question 1

What is another name for producers?

Answer 1

autotroph

Question 2

Why are quaternary consumers less common in mammals, but common in aquatic environments?

Answer 2

• mammals lose energy in maintaining body temp
• ↓ energy to pass on
• aquatic = stable environment
• fish = cold-blooded–> x lose heat for body temp

Question 3

What are sugars used for in plants?

Answer 3

• most = resp
• some = make bio molecules eg. cellulose
• –> biomass- chemical energy stored –> next trophic level

Question 4

Why do we measure the dry mass of tissue per given area?

Answer 4

amount of water varies –> affects overall mass

Question 5

How do we obtain a dry sample to measure mass?

Answer 5

• dry in oven 40-80°C (too high- burn sample)
• weigh at regular intervals until constant mass (all water evaporated)

Question 6

What are the units for dry mass?

Answer 6

gm-2 / kg h-2 (hectare)
- if grown within specific time- kg m-2 y-1 (per year)

Question 7

How can we estimate the mass of carbon in a sample?

Answer 7

calorimeter
- burn biomass
- measure energy given off as heat
- by cal. temp it heats a known vol of water to

Question 8

Evaluate pyramid of biomass

Answer 8

➕ ↑ reliable than pyramid of individual no. of organisms
➖ only estimated w/ small sample –> x representative
➖ drying + weighing –> time consuming/ ethical issues

Question 9

Evaluate pyramid of energy

Answer 9

➕ most accurate- organisms w/ same biomass could have diff. amounts of energy
➖ data is difficult to collect
➖ only representative of given area at one time point

Question 10

Def for productivity

Answer 10

rate of generation of biomass in an ecosystem
- unit: g m-2 y-1

Question 11

def for GPP

Answer 11

gross primary production
- total amount of chemical energy converted from light energy by plants in a given area

Question 12

4 reasons why not all light energy from sun is converted into chemical energy by plants

Answer 12

1. reflected
2. wrong wavelength
3. transmitted thru leaf
4. hits parts of plant x photosynthesise

Question 13

What is respiratory loss?

Answer 13

50% of GPP lost to environment as heat when plants respire

Question 14

def for NPP

Answer 14

net primary productivity
- energy available for plant growth & reproduction
- stored in plant biomass
- energy available for next trophic level

NPP = GPP - R

Question 15

def for secondary productivity

Answer 15

energy stored in biomass by primary consumers –> passed on to secondary consumer/ decomposer

Question 16

Why is only 10% of chem energy passed on to the next trophic level?

Answer 16

1. x all food eaten
2. some parts indigestible –> returned to environment as faeces
3. energy lost as heat in resp. & excretion of urine

Question 17

formula for net secondary production (N)

Answer 17

N = I - (F + R)
- I = energy in ingested food
- F = energy lost in faeces & urine
- R = resp.

Question 18

Why can food chains only support 4/ 5 trophic levels?

Answer 18

• net prod. v. low at top
• apex predators must eat large amounts of prey to consume enough energy
• energy transfer ↑ efficient up the chain ∵ plants have ↑ indigestible matter

Question 19

How do farming practices increase efficiency?

Answer 19

1. ↓ energy lost to pests- chemical pesticides, herbicides (weeds), biological controls 🐞 kill aphids
2. ↓ resp of livestock- controlling conditions –> ↑ energy for growth
   - ↓ costs
   - ↑ food in less time

Question 20

Ethical issues surrounding controlling living conditions of llivestock

Answer 20

1. restricts natural behaviour
2. pain thru uncomfortable conditions
3. diseases ↑ likely to spread (animals kept close tgt) –> overuse of antibiotics

Question 21

negative impact of using chemical pesticides & herbicaides on the environment

Answer 21

1. ↓ biodiversity
2. eutrophication
   - fertilisers get into rivers
   - algae growth over water
   - plants at bottom die
   - decomposers used up all O2
   - organisms die

Question 22

Give 2 uses of nitrogen in animals.

Answer 22

1. make a.a. –> proteins –> newcells + enzymes
2. nitrogenous bases –> nucleotides –> replication of DNA + RNA

Question 23

4 uses of phosphorus in animals

Answer 23

1. phosphate backbone of DNA
2. ATP
3. phospholipids in cell mem
4. calcium phosphate –> bones

Question 24

Why is phosphorus usually a limiting nutrient?

Answer 24

found in low conc, esp in aquatic systems
limits:
- ATP –> ↓ energy for growth
- ↓ DNA + mRNA –> ↓ proteins for growth
- ↓ phospholipids for cell mem
- ↓ photosynthesis ∵ needed in regen of RuBP

Question 25

What form does most phosphorus exist as?

Answer 25

PO4 3- in sedimentary rocks
- released in weathering
- taken up by a.t. in roots

Question 26

How do plants absorb the maximum amount of phosphates from soil?

Answer 26

symbiotic relationship w/ mycorrhizae (in return for sugars)
- hypae ↑ s.a. of root system
- ↑ phosphate, nitrates, water absorbed

my core is sane

Question 27

What is a major source of phosphate in waste?

Answer 27

guano of sea birds –> natual fertiliser

Question 28

2 advantages of using fertilisers in farming

Answer 28

1. ↑ productivity
2. improves efficiency of energy transfer

Question 29

Artificial fertilisers

Answer 29

• inorganic (pure chemicals)
• eg. ammonium nitrate from Haber process- N2 fixation

Question 30

Natural fertilisers

Answer 30

• organic matter
• eg. manure, compost

Question 31

How does crop rotation work?

Answer 31

• alternating growing crops for harvest + leguminous plants
• leguminous plants w/ N2 fixing bacteria- replace nitrates lost
• left to decay- recycle other nutrients

Question 32

Why is the excess use of fertilisers bad?

Answer 32

• ↑ nutrients
• ↓ Ψ
• ↓ water uptake
• water loss (dehydration) by osmosis

Question 33

Process of eutrophication

Answer 33

• excess mineral ions leach into ponds/ rivers
• rapid growth of algae (algal bloom)
• algae on surface blocks light –> x reach plants below –> die
• bacteria decompose dead plant matter
• O2 used up as bacteria respire
• fish + larger aquatic organisms die

↑ likely w/ nitrates ∵ phosphorus is ↓ soluble (natural fertilisers also x soluble, need to be broken down by saprobionts)