UNIT 19 & 20 Organisms and their environment & Human influences on ecosystems

Question 1

role of sun

Answer 1

principal source of energy input to biological systems/of all energy on earth​

Question 2

flow of energy through living
organisms, including light energy from the
Sun and chemical energy in organisms, and its eventual transfer to the environment

Question 3

sustainable resource

Answer 3

📌 a resource that is produced as rapidly as it is removed from the environment so that it does not run out.

[some resources can be conserved and managed sustainably - forests, fish stocks]

Question 4

population

Answer 4

a group of organisms of one species, living in the same area, at the same time

Question 5

community

Answer 5

all the populations of different species in an ecosystem

Question 6

ecosystem

Answer 6

a unit containing the community of organisms and their environment, interacting together

Question 7

food chain

Answer 7

showing the transfer of energy from one organism to the next, beginning with a producer

Question 8

interpreting food chains

Answer 8

​the arrow always starts at the nutrient source and ends at the predator​

Question 9

food web

Answer 9

a network of interconnected food chains

Question 10

interpret food webs

[which show a large range of organisms within an ecosystem and all of the possible ways the energy could be transferred​]

Answer 10

• break food webs down in to trophic levels [the position of an organism in a food chain, food web or ecological pyramid]

Question 11

producer

Answer 11

an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

(e.g. plants, algae, phytoplankton)​

Question 12

consumer

may be…

Answer 12

an organism that gets its energy by feeding on other organisms

• consumers may be classed as primary,
  secondary, tertiary and quaternary according to their position in a food chain

Question 13

herbivore
carnivore
decomposer

START WITH “an animal that gets its energy…”

Answer 13

• an animal that gets its energy by eating plants
• an animal that gets its energy by eating other animals
• an organism that gets its energy from dead or waste organic material

Question 14

trophic level

Answer 14

the position of an organism in a food chain, food web or ecological pyramid

Question 15

Food pyramids of number​ [sometimes pyramid]

-not varying sizes
- not lifespan

Answer 15

• tell us the population numbers of different trophic levels. usually, larger organisms tend to have smaller populations​

📌 tell us the least amount of information and are the poorest method of ordering the trophic levels.

• do not account for the varying sizes of the organisms. Larger organisms will require more energy and store more energy in their biomass.
• does not account for their lifespan. Some organisms live longer than others so will need more energy.​

Question 16

Food pyramids of biomass​

• yes difference in size

Answer 16

• measure the differences in the total proportion of mass between different trophic levels. ALWAYS pyramid shaped, bc there must always be more biomass in the previous trophic level to support the next

📌 more accurate bc they account for differences in the size of the organism. ​

Question 17

Food pyramids of energy​

• yes size and lifespan
• diff type of biomass = diff energy requirements

Answer 17

Only about 10% of energy is passed from one trophic level to the next as biomass​ [stored in the organism as biomass​]

Only the energy that is used to make new cells is passed on to the next trophic level​

the remaining 90% is lost through waste/excretion, egestion, respiration [as heat], maintaining body heat etc. ​

Question 18

food pyramids of energy best bc…

Answer 18

account for differences in size and lifespan of the organism so are more accurate.

• also account for the fact that different types of biomass have different energy requirements.​

Question 19

Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels

Answer 19

• only 10% flow of energy from one trophic level to the next higher level.
• Not enough energy remaining to support another trophic level

Question 20

carbon cycle

Question 21

nitrogen cycle

1. nitrogen fixing bacteria

Answer 21

-can fix nitrogen gas into other nitrogenous compounds (e.g. ammonia)

Question 22

2. lightning

Answer 22

nitrogen gas can also be fixed to ammonia by lightning

Question 23

3. nitrification

Answer 23

-ammonia toxic to plants, so nitrifying bacteria convert ammonia to nitrites then nitrates in nitrification process

Question 24

4. assimilated

Answer 24

4. nitrates can be assimilated by plants to be used in proteins

Question 25

5. feeding

Answer 25

proteins can be passed from plant to animals by feeding

Question 26

6. decomposition, deamination

Answer 26

animal and planets eventually die, causing decomposers like fungi and bacteria to perform deamination on proteins, forming ammonia

Question 27

7. denitrification

Answer 27

nitrogen-containing compounds like nitrates broken back down to nitrogen gas by denitrifying bacteria

Question 28

animal dies, nitrogen compounds in bodies available for plants. Outline processes that occur to make nitrogen compounds in bodies of dead animals available for plants to absorb [5]

Answer 28

eaten by hyenas or vultures egestion, faeces decomposition by bacteria and fungi ammonia to nitrite nitrite to nitrate nitrification plants absorb nitrate

Question 29

factors affecting population growth [4]

Answer 29

food supply predation disease competition

Question 30

4 phases populations have to growth

Answer 30

lag exponential / LOG stationary death

Question 31

lag phase LF = limiting factor

Answer 31

food is abundant population size small limiting maximum rate of population growth BIRTH > DEATH LF: number of reproducing individuals

Question 32

exponential phase

Answer 32

food is abundant deaths low population large enough to exponentially grow. BIRTH > DEATH - no LF

Question 33

stationary phase

Answer 33

food supply equal to population 📌 birth rate equals death rate 📌 population stays same size LF: food supply

Question 34

death phase

Answer 34

food supply less than population population size decreases DEATH RATE > BIRTH RATE LF: food supply

Question 35

Suggest why population of aphids did not increase rapidly until day 40

Answer 35

-small population to start with -takes time for eggs to hatch -not enough food -aphids not sexually mature -too cold -predators -disease -competition

Question 36

describe how humans have increased food production [5] 1. agricultural machinery

Answer 36

1. agricultural machinery (tractors, harvesters) to use larger areas of land and improve efficiency

Question 37

2. chemical fertilisers

Answer 37

to improve yields

Question 38

3. insecticides

Answer 38

to improve quality and yield

Question 39

4. herbicides

Answer 39

to reduce competition with weeds

Question 40

5. selective breeding

Answer 40

to improve production by crop plants and livestock

Question 41

monocultures - ADV

Answer 41

- more efficient (only need to buy equipment/consumables for one crop type, can harvest/tend to all crops at the same time) -crops can be optimised for highest quality/yields

Question 42

DISADV monocultures

Answer 42

-pathogens/disease will affect entire crop - destroys soil nutrients (different plants use different proportions of nutrients) - has larger impact on local ecosystem; reduces biodiversity -can lead to soil erosion due to lack of established roots through soil

Question 43

intensive livestock farming

Answer 43

- involves using limited space to farm large quantities of livestock, much higher than what the land could support naturally - fed high-calorie feeds. + in some countries, given antibiotics to stop them getting sick, further increasing yields. - housed in barns/coops, artificially heated during winter.

Question 44

intensive livestock farming - ADV

Answer 44

- requires less land -food can be produced year-round -less labor costs -less cost of production

Question 45

DISADV [of ILF]

Answer 45

-higher risk of disease outbreaks -herbicides and pesticides used -can cause eutrophication of water supplies & disrupt ecosystems. -reduces biodiversity in environment

Question 46

the process of eutrophication of water [6] 1. ions

Answer 46

1. increased availability of nitrate and other ions

Question 47

2. producers

Answer 47

2. increased growth of producers [preventing sunlight from reaching aquatic plants; water oxygen levels fall]

Question 48

3. decomposition

Answer 48

3. increased decomposition after death of producers

Question 49

4. respiration

Answer 49

4. increased aerobic respiration by decomposers

Question 50

5. oxygen

Answer 50

5. reduction in dissolved oxygen

Question 51

6. organisms

Answer 51

6. death of organisms requiring dissolved oxygen in water

Question 52

risk of untreated sewage to marine ecosystems

Answer 52

-untreated sewage & fertilisers RUN OFF into marine ecosystem has a NEG. IMPACT on MARINE HEALTH -& can lead to eutrophication of water -eventually creating an oxygen-deprived environment where very little can survive

Question 53

plastics (non-biodegradable), in marine habitats: [3]

Answer 53

📌 animals can eat plastics & become caught in it 📌 plastics can release toxins into water 📌 small microplastics ingested by marine organisms & enter food chain.

Question 54

plastics - in land habitats: [2]

Answer 54

-plastics buried in landfills -toxins in plastic leech into soil, making it unfit for growing crops or livestock

Question 55

air pollution - greenhouse gases [2 gases, 2 effects]

Answer 55

-elevated levels of CO2 and methane in atmosphere -higher levels => global warming & climate change

Question 56

sources of CO2 and methane [fossil fuels, livestock, melting permafrost]

Answer 56

📌 burning fossil fuels increases CO2 📌 keeping livestock generates methane gas 📌 global warming melts permafrost in sub-polar regions => more trapped methane released into atmosphere

Question 57

desc problems caused by non-biodegradable plastics in envir. [3]

Answer 57

-does not break down -fills up landfill sites -suffocates animals, kills animals trapped in it -releases toxins

Question 58

why organisms become endangered/extinct [6]

Answer 58

-climate change -habitat destruction -hunting -overharvesting -pollution -introduced species

Question 59

how endangered species can be conserved [4]

Answer 59

-monitoring and protecting species & habitats -education -captive breeding programmes -seed banks

Question 60

how forests can be conserved [4]

Answer 60

📌 education [abt sustainable forestry practices] 📌 protected areas 📌 quotas 📌 replanting trees [replacing those harvested]

Question 61

how fish stocks can be conserved [6]

Answer 61

📌 education [abt sustainable fishing practices] 📌 closed seasons 📌 protected areas (marine reserves) 📌 controlled net types & mesh size 📌 quotas 📌 monitoring fish stocks

Question 62

reasons for conservation programmes [4]

Answer 62

📌 maintaining or increasing biodiversity in ecosystems 📌 reducing extinction 📌 protecting vulnerable ecosystems 📌 maintaining ecosystem functions [nutrient cycling, resource provision (food, drugs, fuel & genes]

Question 63

How eutrophication could’ve resulted in reduction in numbers of cichlid fish [4]

Answer 63

Algae grow Less light for plants for photosynthesis Therefore plants die Plants stop producing oxygen Decomposers feed on dead plants Use up oxygen in aerobic respiration Low levels of oxygen cause fish to die Bacteria produce toxins which cause fish to die

Question 64

effects of large scale deforestation: 1. number of species 2. soils 3. rivers 4. atmosphere [8]

Answer 64

1. loss of habitat. species decrease/extinction. less food available. 2. increase in water content, soil erosion, loss of nutrients 3. soil washed into rivers, rivers flood 4. atmosphere: more carbon dioxide, less oxygen, co2 not absorbed in photosynthesis, global warming

Question 65

AI (artificial insemination)

Answer 65

sperm removed from male placed in female's uterus with small catheter after it's washed & processed

Question 66

in-vitro fertilisation (IVF)

Answer 66

eggs removed from a woman's ovaries, eggs are fertilised with sperm (taken from male) in lab, sperm and egg nuclei fuse in vitro, embryo later implanted into woman's uterus

Question 67

Describe the advantages of drawing a food web rather than a food chain for an ecosystem. [2]

Answer 67

shows complex feeding relationships. all organisms in the ecosystem. [each species has more than one food source. each species has more than one predator.]