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Biology Alevel > Ecosystems > Flashcards

Ecosystems Flashcards

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1
Q

Habitat?

A

Place where an organism lives

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2
Q

Population?

A

All the organisms of one species in one habitat

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3
Q

Producer?

A

An organism that produces organic molecules using sunlight energy e.g plants

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4
Q

Consumer ?

A

An organism that eats other organisms e.g animals/birds

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5
Q

Decomposer?

A

An organism that breaks down dead or undigested organic material e.g bacteria/fungi

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6
Q

Trophic level?

A

A stage in a food chain occupied by a particular group of organisms e.g producers are the 1st trophic level of the food chain

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7
Q

Ecosystem?

A

All the organisms living in a certain area / all non living factors living there
- dynamic system - changing all the time

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8
Q

Abiotic/biotic factors on rock pools?

A

BIOTIC : seaweed is food source for consumers like limpets
- intense comp for food can limit no. Organism present in ecosystem

ABIOTIC : tides - can be completely submerged by ocean at high tides so experience similar abiotic factors : pH , Salinity , Temperature etc.
at low tide, more extreme abiotic factors ( higher salinity /temps) - only some organisms tolerate

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9
Q

Playing field biotic/abiotic factors?

A

BIOTIC : large amounts of plants (producers) attract large number of organisms as FOOD SOURCE

ABIOTIC: rainfall/sunlight affect growth of producers —> heavy rain can cause soil to be waterlogged so hard for growth
- reduces no. Consumers the ecosystem can support

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10
Q

Large tree biotic and abiotic factors?

A

BIOTIC: insects can use leaves of trees as FOOD SOURCE
- however overconsumption of leaves can slow tree growth /lead to death of tree

ABIOTIC : drought can lead to death of tree/negatively impact growth of tree

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11
Q

What are biotic and abiotic factors and examples?

A

Biotic : living features of the ecosystem - predation/competition for food, water,light or space / disease / camouflage and mimicry

Abiotic : non-living features of ecosystem - temperature /rainfall /soil nutrient availability /humidity /salinity/pH /turbidity (cloudiness) of water

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12
Q

What is biomass?

A

Mass of living material of the organism /tissue
Chemical energy that is stored within organism/tissue

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13
Q

What can biomass be measured in terms of?

A

Dry mass of organism /tissue
Mass of carbon that organism /tissue contains - generally taken as 50 % of dry mass
Chemical energy content of organism when burned in pure oxygen

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14
Q

What is calorimetry used for? Process?

A

Used to estimate the chemical energy stored in dry biomass
1. Involves burning sample of dry biomass in calorimeter
2. Burning sample heats known volume of water
3. Change in temp of water provides an estimate of chemical energy the sample contains

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15
Q

Why is a large proportion of sun’s energy not available for photosynthetic plants?

A

Light falls away from plants
Light passes through leaves /reflected away
Light is a mixture of wavelengths - Only certain wavelengths stimulate photosynthesis

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16
Q

Why is only a small percentage of biomass transferred to next trophic level?

A
  • not all of plant’s biomass is eaten by primary consumer
  • not all consumer’s biomass intake is DIGESTED
  • chemical energy is converted to mostly MOVEMENT AND HEAT - only *small amount to new biomass
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17
Q

Efficiency of biomass transfers between trophic levels EQUATION?

A

Efficiency of transfer = (biomass transferred / biomass intake ) x 100

Or
efficiency = net productivity of primary consumers/ net productivity of producers

18
Q

Net productivity of producers /net primary productivity (NPP) EQUATION? What is it?

A

Amount of energy available to next trophic level (Kj m-2 yr-1)
NPP = GPP - R
GPP = gross primary productivity (energy taken in - rate at which plant convert light energy—> chemical energy by photosynthesis)
R = respiratory losses

19
Q

Net productivity of consumers equation?

A

N = I - (F + R)

I = chemical energy store in ingested food
F = chemical energy lost to environment in faeces/urine
R = respiratory losses to environment

20
Q

How does human activity manipulate the efficiency of biomass transfer?

A

Farmers can increase agricultural productivity by increasing biomass transfers by:
For producers :
- Irrigation to maximise growth in dry weather
- Use of fertilisers - growth of plants
- Selective breeding for fast growth
- Use of fungicides/pesticides

For primary consumers :
- Use of good quality feeds / food supplements
- Use antibiotics and vaccines to reduce disease
- Control predation with fencing etc
- Intensive control of conditions to reduce energy loss from movement or from getting cold outside

21
Q

What are decomposers known as and how do they break down organic/waste matter?

A

Saprobionts - from fungi/bacteria kingdom

  • They secrete enzymes onto dead organisms/waste material which digest the material externally - EXTRACELLULAR DIGESTION
    Products of extracellular digestion is then absorbed by SAPROBIONTS
    This method is known as SAPROBIOTIC NUTRITION
  • not all products of extracellular digestion are absorbed by Saprobionts/many remain in surrounding for other organisms
22
Q

Why are Saprobionts essential ?

A

Nutrients would be locked up in dead/waste matter and wouldn’t be made available again for producers to use
- also some Saprobionts can excrete important nutrient mineral ions as waste products from their own metabolism

23
Q

What is mycorrhizae ?

A

The symbiotic (mutually beneficial) relationship between fungi and plants

Fungi’s hyphae interact with plant roots / increase SA of root system of plants —> INCREASE WATER AND MINERAL IONS ABSORBTION
- in return fungi receive organic compounds (e/g glucose) from plant

24
Q

Role/reactants and location of nitrogen fixing bacteria? (Azotobacter and Rhizobium species)

A

Convert gaseous nitrogen into AMMONIA (NH4+) -ANAEROBIC process
Reactants: N2 + H+—> NH3 (reduction)
Location: root nodules , leguminous roots

Rhizobium form mutualistic relationship with plants- provide plant with nitrogenous compounds /plant provides carbs to them

25
Q

Nitrifying bacteria role,reactants , location? (Nitrosamines and Nitrobacter species)

A

Nitrify ammonium ions into NITRITE (NO2-) and nitrate (NO3- ) - highly soluble and can be absorbed by roots
BACTERIA FOUND IN SOIL:
Nitrosamines : NH4+ —> NO2- (NITRITES)
Nitrobacter : NO2- —> NO3- (NITRATES)
- both oxidation

26
Q

Denitrifying bacteria role, reactants and location?

A

Use nitrates for respiration and return gaseous nitrogen back into atmosphere
FOUND IN SOIL
Reactants: NO3-—> N2 (reduction)

27
Q

What is the carbon cycle?

A

1.photosynthesis - autotrophs (makes their own food using light,water, CO2 and other chemicals) uses energy from sun to ‘fix’ carbon dioxide , turning CARBON —> SUGARS /ORGANIC MOLECULES
Removes carbon from atmosphere
2. Sedimentation - body of dead plants not fully decomposed by Saprobionts - bodies form layer of sediment and accumulates over millions of years- locking carbon into ground
- sediment is store of energy /form fossil fuels (e.g peat /coal)
3. Respiration - respiration puts CO2 back into atmosphere / released in LINK REACTION /KREBS CYCLE of aerobic respiration
Anaerobic releases CO2 via fermentation by yeast, mould and bacteria
4. Feeding- Carbon passed from autotroph to heterotroph during feeding (primary to secondary consumer)
5. Decay/decomposition - dead plants/animals are fed upon by detritivores/decayed by saprophytes
- release carbon to surroundings /supply detritivores and saprophytes with carbon

28
Q

How has burning fossil fuels and caused climate change ?

A

CO2 is being returned faster than it can be absorbed by plants and aquatic producers
Also warmer temps means less co2 can dissolve in oceans so released into air

CLIMATE CHANGE as a result /affect habitats

29
Q

What is succession?

A

Progressive change in a community of organisms over time
- biotic and abiotic conditions change over time

30
Q

What is primary succession?

A

Process that occurs when newly formed/newly exposed land is gradually colonised by an increasing no. Species
Uninhabited land created by:
Magma from volcanoes cools/forms new rock surfaces or even new islands in sea
Sea level dropping/lake dry up —> leave areas of bare rock

31
Q

eg of barren terrain undergoing primary succession? What is a pioneer species?

A

Sand dunes in coastal areas - marram grass are the pioneer species in these environs as they have deep roots to access water that otherwise plants can’t reach/can tolerate salty environment

Pioneer species: species that can colonise bare rock or ground (usually first living things there) /begins process of succession

32
Q

Stages of primary succession? What is a climax community?

A
  1. Seeds/spores carried by wind ,land on exposed rock and begin to grow - pioneer species
    These species die/decompose , dead organic matter (humus) forms basic soil
  2. Seeds of small plants/grasses , carried by wind or other ways (by sea/bird faeces) land on basic soil and begin to grow - adapted to survive shallow /nutrient poor soils
    As these small plants die/decompose , new soil becomes deeper and more nutrient rich / roots of these plants also form network that hold soil in place /prevent it being washed away
  3. Larger plants /shrubs and small trees that need deeper , more nutrient rich soil and water , can begin to grow
  4. Soil is now sufficiently deep, contain enough nutrients/water for growth of large trees —> DOMINANT SPECIES (final species to colonise new land) —> now a complex ecosystem

Climax community is formed : stable final community that exists in a balanced equilibrium after the process of succession has occurred

33
Q

Example of changing environ dung succession?

A
  1. Pioneer species grow on bare rock (lichens) help break apart top surface of rock
    Fragmented rock as well as humus left behind when lichens die, are broken down —> BASIC SOIL
    Lichen have changed local environment so it’s more suitable for other species (e.g mosses)
  2. Mosses grow /soil builds up until small plants and grass colonise new land—> result in formation of thin soil layer that covers newly formed rock completely
    Lichen *cannot grow on soil —> DISAPPEAR from ecosystem - less suitable for lichens
  3. Soil deepens further /trees grow that out compete shrubs and smaller plants due to lack of light
34
Q

What is deflected succession? Examples?

A

When succession is stopped or interfered with causing stable community to be different to climax community - PLAGIOCLIMAX COMMUNITY

Lawn mowing —> if left alone, field would develop into shrubs/tres due to succession , but mowing prevents this (only grasses survive by regular mowing)
Grazing - succession halted by grazing of livestock , as they eat new plant shoots trying to grow

35
Q

Why is preventing an area from reaching its climax community /managing succession sometimes a good thing?

A
  • ecosystems at immediate stages of succession (small plants, grasses and shrubs present) have DISTINCT DIVERSITY, which wouldn’t exist if climax community is reached —> these plants can be of CONSERVATION IMPORTANCE
  • diverse plant species provide food/habitat for a high diversity of animal species —> some animals may be of CONSERVATION IMPORTANCE ( bc endangered/rare or have functions in ecosystem)
36
Q

Ways succession can be prevented for conservation purposes?

A

Grazing animals can be introduced temporarily - at growing shoots of shrubs and trees
Managed burning - controlled fires lit/burn away shrubs and trees

37
Q

How do biologists estimate abundance?

A

ACFOR : Abundance , Common, Frequent, Occasional , Rare

38
Q

What is random and systematic sampling?

A

Random: positions of sample points completely random/due to chance
Systematic: positions of sample points chose by the person carrying out the sampling —> SAMPLE BIAS MAY BE INTRODUCED

39
Q

Method to find dry mass and energy value of plant biomass?

A

Dry mass :
Weigh crucible (heat proof container) without sample
Place sample in crucible/put in oven at low temp - dont let it burn otherwise lose biomass
Remove/weigh crucible at regular intervals during drying process
Once mass of crucible stops decreasing /becomes constant —> sample is fully dehydrated
Subtract original mass of the crucible from the constant mass to find dry mass of sample

Find energy released by sample of plant biomass:
Use calorimeter - burn dried sample and used energy released to heat known vol of water
- measure change in temp of water - use to estimate the chemical energy stored within sample (JOULES or KILOJOULES )

40
Q

Nitrogen cycle? And which bacteria involved at each stage?

A
  1. Nitrogen fixation - RHIZOBIUM/AZOTOBACTER
  2. Ammonification - nitrogenous compounds from dead organisms (plants,animals,faeces)—> AMMONIA by decomposer —> AMMONIUM IONS (NH4+)
  3. Nitrification - NITROSOMONAS /NITROBACTER
  4. Dentrification - dentifyung bacteria
41
Q

What are point quadrant?

A

Horizontal bar on 2 legs with series of holes along its length
- placed at random points in sample area
- pines dropped through holes in frame/every plant pin touches is recorded
No. Individuals of each species recorded in each quadrat / % cover calculated by no. Times pin has touches a species as percentage of total no. Pin has dropped
(GOOD FOR USE IN DENSE VEGETATION)

Biology Alevel (26 decks)

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