Ecosystems (Genetics, evolution and ecosystems)

Question 1

Ecosystem definition

Answer 1

An ecosystem is made up of all the living organisms that interact with eachother in a defined area, as well as the abiotic factors present

Question 2

Why are ecosystems dynamic?

Answer 2

Ecosystems are dynamic as they are constantly changing due to the living organisms present and the environmental conditions

Question 3

Biotic factors

Answer 3

Biotic factors - the living factors - interactions often involve competition - eg for food, space/territory and breeding partners

Question 4

Abiotic factors

Answer 4

Abiotic factors - the non-living/physical features -> eg light temperature, water availability, oxygen availability, edaphic (soil) factors

Question 5

Light as an abiotic factor

Answer 5

Light is an abiotic factor as:
-plants are directly affected by its availbility for photosynthesis, greater amounts increase sucess of a plant species
-Plants can develop strategies to cope with different light availbilities, such as developing photosynthetic pigments that need less light or selective reproductive systems to maintain energy

Question 6

Temperature as an abiotic factor

Answer 6

Temperature -> effect of temp on the enzymes controlling metabolic reactions -> affects ectothermic animals more than endothermic animals

Question 7

Ectothermic animals

Answer 7

Ectothermic animals are animals whose regulation of body tempreature depends on external surfaces such as light or hot rocks. These are cold-blooded animals.

Question 8

Endothermic animals

Answer 8

Endothermic animals control their internal temperature, and so are less affected by the external environment

Question 9

Why is water availability especially important for plants?

Answer 9

A lack of water causes plants to wilt, as water is required to keep cells turgid and keep the plant upright, and is required for photosynthesis. Xerophytes are adapted against water stress.

Question 10

Oxygen availability as an abiotic factor

Answer 10

Oxygen availbility is especially important in aquatic ecosystems, as it is beneficial to have fast-flowing cold water as it contains high conc of oxygen. When it is too warm or too slow, oxygen conc drops and leads to suffocation of aquatic organisms.

Question 11

Edaphic (soil) as an abiotic factor

Answer 11

Edaphic (soil) - different soil types have different particle sizes - has an effect on the organisms that are able to survive in them

Question 12

3 main types of soil that impact on organisms within ecosystems as an abiotic factor

Answer 12

-3 main types: clay (easily waterlogged, forms clumps when wet), loam (different sized particles, retains water but does not become waterlogged), sandy (has coarse, seperated particles that allow free draining, doesn’t retain water and easily eroded)

Question 13

Producers within trophic levels

Answer 13

Producers are organisms that convert light energy into chemical energy by photosynthesis

Question 14

Sucessive stages of tropic levels

Answer 14

Producer -> primary consumer -> secondary consumers -> tertiary consumers -> quaternary consumer

Question 15

Biomass definition

Answer 15

Biomass = the mass of living material present in a particular place or in particular organisms

Question 16

How to calculate biomass

Answer 16

Measuring biomass:
Multiply the biomass present in each organism by the total number of organisms in that trophic level (represents biomass present at that moment in time, does not take into account seasonal changes)

Question 17

How to measure biomass

Answer 17

How to measure biomass:
Organisms have to be killed, dried and placed in oven at high temp in order for water to evaporate so results are reliable, and then mass of material is measured.
-Measured in grams per square metre for land, and grams per cubic metre for areas of water

Question 18

Why is the biomass in each trophic level always less than the trophic level below?

Answer 18

Biomass consists of all cells and tissues, and can be equated to energy content due to compounds present, so when animals eat only a small amount of whats ingested is converted into new energy

Question 19

Energy available at each trophic level unit

Answer 19

Energy availble at each trophic level is measured in kiljoules per metre sequared per year (to allow for changes in photosynthetic production and consumer feeding patterns throughout the year)

Question 20

Ecological efficiency definition

Answer 20

Ecological efficiency = the efficiency with which biomass or energy is transferred from one trophic level to the next is called the ecological effeciency

Question 21

Why is it that producers only convert 1-3% of sunlight into chemical energy/biomass?

Answer 21

-Not all of the solar energy available is used for photosynthesis (approx 90% is reflected, some transmitted, some of unusuable wavelength)
-Other factors may limit photosynthesis, such as water availability
-A proportion of the energy is lost as it is used for photosynthetic reactions

Question 22

Formula for the energy available to the next trophic level

Answer 22

Formula for the energy available to the next trophic level:
Net production = gross production - respiratory losses

Question 23

Why is it that consumers at each trophic level convert at most 10% of the biomass in food to their own organic tissue?

Answer 23

-Not all of the biomass is eaten
-Some energy transferred to environment as metabolic heat due to movement and/or respiration
-Some parts of organism are eaten but are indigestible -> egested as faeces
-Sine energy lost in exctretory materials such as urine

Question 24

Ecological efficiency calculation

Answer 24

Ecological efficiency = (energy or biomass available after transfer) / (energy or biomass available before transfer) x 100

Question 25

How agriculture manipulate biomass through ecosystems

Answer 25

In agriculture, only two trophic levels present -> producers (crops), primary consumers (humans) -> means minimum energy is lost since fewer levels present -> more energy transferred into biomass for humans

Question 26

Decomposers within ecosystems

Answer 26

Decomposers = organisms that feeds on and braek down plant or animal matter (turns organic compounds into inorganic for photosynthetic producers) - mostly fungi and bacteria - saprotrophs

Question 27

Saprotrophs

Answer 27

Saprotrophs - digest food externally by secreting enzymes onto dead organisms or organic waste matter - these encymes break down complex molcules to be ingested by the organism - this is how decomposers release stored inorganic compounds back into the environment

Question 28

Detritivores

Answer 28

Detritivores - involved in decomposition - speeds up decay process by feeding on detritus (dead and decaying material) - break down into smaller organic material - increases surface area for decomposers to work on - eg woodlice and earthwoms - they perform internal digestion

Question 29

Nitrogen-fixing bacteria

Answer 29

Nitrogen-fixing bacteria - contains nitrogenase - which combines atmospheric nitrogen with hydrogen to produce ammonia - which can be absorbed and used in plants - this is known as nitrogen fication

Question 30

Nitrification

Answer 30

Nitrification is the process by which ammonium compounds in the soil are converted into nitrogen-containing molecules that can be ued in plants - free-living bacteria called nitrifying bacteria are involved

Question 31

Process of nitrification in well-aerated soil

Answer 31

Nitrification (oxidation reaction):
1). Nitrifying bacteria oxidise ammonium compounds into nitrites
2). Nirobacter (genus of nitrifying bacteria) oxidise nitrites into nitrates
-> nitrate ions are highly soluble and so in this form can enter the plant

Question 32

Dentrification

Answer 32

Dentrification = in the absence of oxygen eg in waterlogged soils, dentrifying bacteria convert nitrates in the soil back to nitrogen gass (known as dentrification)
-Only happens under anerobic conditions
-Bacteria use the nitrates as a source of energy for respiration and nitrogen gas is released

Question 33

Ammonification

Answer 33

Ammonification = name given to the process by which decomposers convert nitrogen-containing molecules in dead organisms, faeces and urine into ammonium compounds

Question 34

Effect of water temprature on amount of carbon that can dissolve

Answer 34

Higher the temprature of seas and oceans, less gas is dissolved, therefore global warming reduces the carbon bank in the oceans and releases more in the atmosphere - positive feedback loop

Question 35

Two types of sucessions

Answer 35

-Primary sucession = this occurs on an area of land that has been newly formed or exposed such as bare rock, no soil or organic material prsent to begin with
-Secondary sucession = occurs on areas of land where soil is present, but no plant or animal species

Question 36

When does primary sucession occur?

Answer 36

Primary sucession occurs when:
-Volcanoes erupt, despositing lava that cools and solidifies as igenous rock
-sand blown by wind or deposited by sea to create sand dunes
-silt and mud deposited at river estuaries
-galicers retreat depositing rubble and exposing rock

Question 37

Main seral stages/seres within sucessions

Answer 37

Main seral stages/seres within sucessions:
pioneer community colonisers (eg lichen) -> intermediate community (secondary, tertiary, shrub) -> climax community (dominant species)

Question 38

Pioneer community

Answer 38

Pioneer communities within sucessions:
-First seral stage, arrive as spores/seeds carried by wind or birds
-Eg algae and lichen
-Has adaptations
-Colonises inhospitable environments

Question 39

Adaptations of pioneer species that enable them to colonise a bare environment:

Answer 39

Adaptations of pioneer species that enable them to colonise a bare environment:
-Ability to produce large quantities of speeds/spores to be blown away and deposited on the new land
-Seeds germinate rapidly
-Ability to photosynthesis to produce their own energy
-Tolerance to extreme environments
-Ability to fix nitrogen from atmosphere to add to soil mineral content

Question 40

Intermediate communities within sucessions

Answer 40

Intermediate communities within sucessions:
Intermediate communities involve secondary and tertiary colonisers, that are introduced when pioneer species decompose and release organic components into the soil (known as humus)
-At each seral stage within the intermediate community the organisms are better adapted to the current conditionsm which outcompete previous organisms present and become dominant species

Question 41

Climax communities within sucessions

Answer 41

Climax community - community is as a stable state within the sucession - little change over time - consists of dominant species - not the peak biodiversity (this is reached mid-succession) as dominant species reduce biodiversity

Question 42

Deflected sucession

Answer 42

Deflected sucession -> human ativity halting the natural flow of sucession, preventing climax communities being reached
-When sucession is artificially stopped, the final stage formed is a plagioclimax

Question 43

Why is agriculture one of the amin reasons deflection sucession occurs?

Answer 43

Agriculture:
-Grazing and trampling of vegetation by domesticated animals
-Removing existing vegitation for crops (becomes final community)
-Burning for forest clearence - often leads to biodiversity increase as provides space and nutrient-rich ash for other species to grow eg shrubs

Question 44

Distribution of organisms

Answer 44

Distribution of organisms refer to where individual organisms are found

Question 45

How to measure distribution of organisms

Answer 45

Distribution of organisms can be measured thorugh the use of belt or line transects (systematic non-random sampling)

Question 46

What is systematic sampling?

Answer 46

Systematic sampling - different areas within an overall habitat are identified, which are then sampled separately

Question 47

Why is systematic sampling good to use within ecosystems?

Answer 47

Systematic sampling is beneficial as it allows scientists to study how the differing abiotic factors in different areas of habitats affect the distribution of species

Question 48

Abundance of organisms definition

Answer 48

Abundance of organisms refer to the number of individuals of a species present in an area at any given time

Question 49

Why does abundance of organisms fluctuate daily?

Answer 49

Organism abundance fluctuates daily due to :
-Immigration and births will increase the number of individuals
-Emigration and deaths will decrease the number of individuals

Question 50

Population definition

Answer 50

Population is a group of similar organisms living in a given area at a given time - hard to calculate eg due to environmental damages /hard to count each - so estimation calculated via sampling techniques

Question 51

Formula for measuring plant abundance

Answer 51

Formula for measuring plant abundance:
Estimated number in population (m^-2) = (number of individuals in sample) / (area of sample in m^2)

Question 52

Capture-mark-release-recapture method used to estimate population size

Answer 52

Capture-mark-release-recapture method used to estimate population size:
1). Capture as many individuals within the sample area
2) Mark/tag each
3) Release marked back and allow time for redistribution
4) recapture as many as possible and record number of marked and unmarked
5) use lincoln index to estimate the population size

Question 53

Lincoln index used to estimate the population size:

Answer 53

Lincoln index used to estimate the population size:
Estimated population size = (number of individuals in first sample x number of individuals in second sample) / (number of recaptured marked individuals)

Question 54

Simpsons index of diversity

Answer 54

Simpsons index of diversity:
-Used to calculate biodiversity
-Always between 0-1 (1= infinite diversity, 0 = none)

Question 55

What is a limiting factor in ecosystems?

Answer 55

A limiting factor is an environmental resource or constant that limits population growth

Question 56

Phases of a population growth curve that show abdunance within ecosystems

Answer 56

Phases of a population growth curve that show abdunance within ecosystems:
~Phase 1 = a period of slow growth – small number of individuals initially present reproduce increasing the total population – birth rate higher than death rate and so population increases in size
~Phase 2 = a period of rapid growth = as number of breeding individual increases, total population multiplies exponentially, no constraints
~Phase 3 = a stable state – further population growth prevented by external constrains, population still increasing but is stable, birth and death rates equal

Question 57

Limiting factors found within ecosystems

Answer 57

Limiting factors found within ecosystems include: abiotic (non-living, temp, light pH, water and oxygen availability, humidity), or biotic (living, pradators, diseases and competition)

Question 58

What is carrying capacity in ecosystems

Answer 58

Carrying capacity is the maximum population size that an environment can support

Question 59

What are density independant factors in ecosystems>

Answer 59

Density independant factors in ecosystems are factors that have an effect on the whole population regardless of its size -> eg earthquakes, fires, volcanic eruptions and storms

Question 60

Why does speciation occur?

Answer 60

Speciation occurs because:
-Variation occurs due to mutation
-Different environmental conditions present
-Reproductive seperation/isolation
-Different alleles passed on
-Eventually different species

Question 61

Effect of a loss of nutrients into a lake habitat

Answer 61

Effect of a loss of nutrients into a lake habitat:
-Growth of algae, blocks sunlight, less photosynthesis, less oxygen for fish to respire, fish die and decompose (eutrophication)

Question 62

Mutualistic relationship in the nitrogen cycle,

Answer 62

Mutualistic relationship = nitrogen fixation is an example of a mutualistic relationship, as both bacteria and plants benefit (bacteria gain carbohydrates, plants gain amino acids)