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bio > 3.5 Energy and ecosystems > Flashcards

3.5 Energy and ecosystems Flashcards

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Biology 101 flashcards
1
Q

define photoautotrophs

A

produces

use light energy to synthesise their own food

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2
Q

how do plants synthesise their own organic compounds

A

from atmospheric, aquatic CO2
most sugars used as respiratory substrate
rest used to make biological molecules = forms plant biomass

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3
Q

define heterotrophs

A

cannot synthesise their own energy
obtain it from autotrophs/ other hetertrophs
act as consumers

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4
Q

how can biomass be measured

A
  • mass of carbon

- dry mass of tissue per given area

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5
Q

method to measure biomass

A
  1. sample of organism dried in oven at low temp , to avoid combustion
    2.sample reweighed at regular intervals
  2. mass constant = all water removed
    4.mass of carbon = 50% of dry mass
    5
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6
Q

why is dry mass used

A

more representative

water content of sample varies

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7
Q

what is calorimetry used for

A

to estimate chemical energy stored in dry biomass

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8
Q

method for calorimetry

A
  • sample of dry biomass burnt
  • energy released used to heat known vol of water
  • change in temp of water used to calculate chemical energy
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9
Q

define GPP

A

gross primary production

-chemical energy store in plant biomass in a given area in a given time

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10
Q

define NPP

A

net primary production

  • chemical energy store in plant biomass after respiratory losses
  • GPP - R
  • available for plant growth and reproduction
  • available to other trophic levels
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11
Q

formula for net production of consumers

A

N = I - (F + R)

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12
Q

rates of productivity units

A

kJ ha–1 year–1

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13
Q

why is per unit area used

A

different environments vary in size
standardises results so
environments can be compared

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14
Q

why is per year used

A

more representative
as it takes into account effect of seasonal variation
on biomass
so environments can be compared

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15
Q

describe inefficient energy transfer between sun–>producer

A
  • wrong wavelength of light
  • light strikes non-photosynthetic region
  • light reflected
  • lost as heat
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16
Q

describe inefficient energy transfer producer–>primary consumer–>secondary consumer etc

A
  • respiratory loses
  • lost as heat
  • not all plant/animal eatern
  • some food not digested
17
Q

farming practices to increase energy transfer efficiency; crops

A

simplifying food webs to reduce energy/biomass loss

  • herbicides->killweeds/less competition/more energy to create biomass
  • fungicides->reduce fungal infections/more energy to create biomass
  • pesticides->reduce loss of biomass from crops

fertilisers

18
Q

farming practices to increase energy transfer efficiency ; livestock

A

reduce respiratory losses within human food chain
-restrict movement
-keep warm
slaughter animal while young- most of energy used for growth
selective breeding to produce breeds with higher growth rates
antibiotics - prevent loss of energy due to pathogens

19
Q

role of saprobionts in recycling chemical elements

A
  • feed on dead plants/animals + their waste products + break down organic molecules
  • secrete enzymes for extracellular digestion
20
Q

role of mycorrhizae in recycling chemical elements

A
  • symbiotic relationship between fungi + roots of plants = mycorrhizae
  • fungi act as extension of plant =hyphae=increase sf area = ^ rate of absorption of water/nutrients
  • mutualistic relationship- plants produces fungi with carbohydrates
21
Q

state the stages of the nitrogen cycle

A

ammonificiation
nitrification
nitrogen fixation
denitrification

22
Q

what happens in ammonification

A
  • nitrogen containing compounds from dead organism/waste broken down
  • converted to ammonia ->ammonium ions in soil
  • by saprobionts
23
Q

what happens in nitrification

A

ammonium ions–>nitrites–>nitrates
two stage oxidation reaction
by nitrifying bacteria ( need o2)`
nitrates absorbed via active transport

24
Q

why do farmers aerate their soil

A

increase o2->more nitrifying bacteria, less denitrifying–>maximise nitrogen availability

25
Q

what happens in denitrification

A

nitrates in soil–>nitrogen gas
by denitrifying bacteria –> anaerobic
reduces availability of nitrogen containing coumpounds for plants

26
Q

what happens in nitrogen fixation

A

N2–>nitogen containing compounds
by nitrogen-fixing bacteria
-can be free living in soil
-or mutualistic

27
Q

what is the importane of the nitrogen cycle

A
  • N2 is unreactive + not easily converted to other compounds
  • most plants can only take up nitrogen as nitrates
  • used by plants/animals to make proteins/nucleic acids–>growth
28
Q

describe the stages of the phosphorous cycle

A
  1. phosphate ions in rocks released by erosion/weathering
    - taken up by aquatic produces
    - passed along to birds
    - guano, bird waste, returns phosphate ions
  2. phosphate ions taken into plants by roots + in biomass
  3. phosphate ions transferred via food chain
  4. some phosphate ions lost from animals in waste products, death
    - decomposed by saprobionts
    - releases phosphate ions to soil
29
Q

why are fertilisers used

A

replaces nutrients

  • crops harvested
  • livestock removed
  • nutrients removed from soil
30
Q

what are artificial fertilisers

A
  • inorganic
  • contain pure chemicals
  • more water soluble-larger quantities washed away-impacts environment
31
Q

what are natural fertilisers

A
  • organic
  • manure,compost,sewage
  • cheaper but nutrients cant be controlled
32
Q

how does the leaching of fertiliers happens

A
  • rain washed water soluble compounds out soil into waterways
  • worse when more fertiliser added
33
Q

what is eutrophiciation

A
  • caused by leaching
  • rapid growth of algae in ponds + rivers=algal bloom
  • algae blocks light, prevents it from reaching below
  • death of photosynthetic plants
  • sapriobionts decompose dead plant-aerobic-reduces o2 conc-death of aquatic organisms
34
Q

why is leaching less likely with natural fertilisers

A
  • nitrogen/phosphorous in organic molecules
  • organic molecules less soluble in water
  • need to be decomposed by saprobionts
35
Q

how can fertilisers reduce species diversity

A
  • favours fast growing compounds
  • slower growing plants lose out
  • less organisms who feed off of them

bio (12 decks)

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