ECOSYSTEM

Question 1

what is an ecosystem?

Answer 1

the relationship between all living and non-living components of a habitat

Question 1

what are the component of an ecosystem?

Answer 1

Habitat = place where organism lives
Population = all of the organism of one species, who live in the same place at the same time, who can breed together
Community = all the populations of different species, live in the same place at the same time

Question 2

what are two characteristic of ecosystems?

Answer 2

vary in size
very dynamic

Question 3

what are the 2 groups of factors affecting ecosystem?

Answer 3

abiotic and biotic factors

Question 4

list biotic factors

Answer 4

producers
consumer (primary, secondary and tertiary)
decomposers
predation
competition
hunting

Question 5

list abiotic factors

Answer 5

light
temperature
pH

Question 6

what are 3 types of change in ecosystem that affect population size?

Answer 6

cyclic changes - changes repeat themselves in a rhythm (tides), the way in which predator and prey species fluctuate is cyclic

directional changes - changes are not cyclic
unpredictable/erratic changes - have no rhythm and no constant direction

Question 7

what is biomass?

Answer 7

mass of all living materials in an ecosystem

Question 8

what is the first source of energy in an ecosystem?

Answer 8

sunlight.

Question 9

explain what happens to sunlight?

Answer 9

only a small percentage of light (1-3%) is absorbed by plants and used by them. The rest of the sunlight might not be absorbed to to light not hitting the chloroplast or due to wrong wavelength of light which makes it reflect.

Question 10

what is total amount of energy USED by the plant to make biomass called?

Answer 10

gross production

Question 11

what might be the energy use for in plants?

Answer 11

for respiration

Question 12

what is meant by net production?

Answer 12

the remaining energy, the energy that is going to be transferred to the next consumer

Question 13

how is net production calculated?

Answer 13

gross production - respiratory losses

Question 14

how do consumers get energy?

Answer 14

by ingesting producers, however only 10% of th energy is transferred to the consumer as some of the biomass might be digested and released into faeces, urine and respiration, released as heat.
less available at higher trophic levels

Question 15

what is the formula to calculate ecosystem efficiency?

Answer 15

(biomass transferred : biomass intake) x 100
(biomass at higher level : biomass at lower level) x 100
(biomass of primary consumer : biomass of producer) x 100

Question 16

what makes up the biomass?

Answer 16

organic and inorganic components

Question 17

what is a trophic level?

Answer 17

each level in the food chain

Question 18

what is meant by productivity?

Answer 18

the rate at which energy passes through each trophic level in the food chain

Question 19

what is gross primary productivity ?

Answer 19

the rate at which plant convert light energy into chemical energy

Question 20

how do human manipulate environmental factors to increase the amount of biomass in plants?

Answer 20

• grow plant under light banks and crops planted early to provide longer growing season to harvest more light , thus increasing the rate o photosynthesis and biomass production
• grow plant in greenhouses which provides warmer temperature increasing photosynthesis rate and biomass production
• crop rotation can stop the reduction of inorganic materials in soil (nitrate or potassium), thus plant will have more nutrients available to carry out more photosynthesis
• use of pesticides and fungicides and herbicides to kill insects that may feed on plants removing biomass from food chain
  -competition of weed for light, water and nutrients, reduces crop

Question 21

how do human manipulate environmental factors to increase the amount of biomass in animals?

Answer 21

• harvesting animal just before adulthood

-selective breeding to produce improved animal

-animals treated with antibiotics to avoid unnecessary loss of energy

• preventing animals from moving to look for food, food is directly supplied to them and environmental temp is kept constant

Question 22

why does the carbon cycle occur?

Answer 22

because there is a limited availability of carbon, therefore it is recycled

Question 23

describe the carbon cycle.

Answer 23

-carbon dioxide present in the atmosphere
-carbon dioxide uptaken by plants
-carbon dioxide is used for photosynthesis
-carbon dioxide is converted into carbon containing compounds = carbon fixation
-carbon dioxide is also released into the atmosphere via respiration
-consumers feed off from producers, therefore the carbon containing compounds are passed on the food chain
-consumers also release carbon dioxide via respiration
-when producers and consumers die, the carbon containing compound remain in their waste matter.
-these waste matters and compound are broken down by decomposers in a process called decomposition , this process releases carbon back in the atmosphere
- the waste matters that are not decomposed become fossil fuels
- when fossil fuels are burnt, via the process of combustion, this releases carbon dioxide into the atmosphere.

Question 24

what is the process of converting nitrogen gas into ammonia called?

Answer 24

nitrogen fixation

Question 25

what are the bacteria that carry out nitrogen fixation called? give 2 examples

Answer 25

nitrogen-fixing bacteria : Azotobacter (lives freely in the soil) ( nitrogen gas- ammonia - ammonium ions) rhizobium ( roots nodules) ( nitrogen gas - ammonia)

Question 26

in what condition can nitrogen fixation occur?

Answer 26

anaerobic conditions

Question 27

what is the process of converting ammonium ions into nitrate known as? describe the steps

Answer 27

denitrification : ammonium ions - nitrite - nitrate

Question 28

by what type of bacterias is nitrification carried out? give example in each step

Answer 28

nitrifying bacteria. ammonium ions into nitrite = nitrosomonas nitrite into nitrate = nitrobacter

Question 29

what is required for nitrification, why?

Answer 29

oxygen - bacteria need oxygen for aerobic respiration to ensure their survival, oxygen used in nitrification

Question 30

how is nitrogen returned to the soil?

Answer 30

by death and excretion of plants and animals

Question 31

what happens to dead organisms and excretion containing nitrogen? and what does it result to?

Answer 31

broken down by decomposers (saprobionts) , results in ammonia formation

Question 32

what happens to ammonia?

Answer 32

released into the soil to make ammonium ions

Question 33

what is ammonification?

Answer 33

the process of obtaining nitrogen form the decomposition of dead organism and excretion, producing ammonia which is then converted into ammonium ions

Question 34

how is thereduction of nitrogen gas availability in the atmosphere avoided?

Answer 34

by the process of denitrification

Question 35

explain the process of denitrification

Answer 35

denitrifying bacteria convert NITRATE into nitrogen gas in anaerobic conditions

Question 36

when can denitrifying bacteria carry out denitrification?

Answer 36

when they carrying out anaerobic respiration

Question 37

what processes can occur under anaerobic conditions?

Answer 37

nitrogen fixation an denitrification

Question 38

what processes reduce or oxidise nitrogen?

Answer 38

nitrogen fixation - reduction nitrification - oxidation denitrification - reduction

Question 39

what is succession in ecosystem?

Answer 39

when a habitat/ ecosystem changes from simple to complex over time

Question 40

how does succession occur?

Answer 40

via seral (intermediate) stages.

Question 41

what is the first stage of seral stages, describe it.

Answer 41

PRIMARY SUCCESSION : when there is an inhabited land, which is colonised by an initial species (mousse or lichen - PIONEER SPECIES), usually in the form of seeds or spores these species are often adapted for colonisation eg tolerant to extreme conditions and reproduce asexually. -primary succession

Question 42

what do pioneer species cause?

Answer 42

change the environment making it less hostile and enabling the survival of other species

Question 43

what is the second stage of seral stages?

Answer 43

INTERMEDIATE COMMUNITY : the growth of an intermediate community such herbs and grass, shrubs and trees. When these intermediate organisms decompose, they release nutrients into the soil making the environment less hostile secondary succession

Question 44

what is the last stage of seral stages?

Answer 44

CLIMAX COMMUNITY - when the environment becomes stable and no more succession occurs,present at the end of primary succession

Question 45

what is meant by deflected succession?

Answer 45

when human activities interfere or stop succession, such as agriculture and farming. the habitat doesn't reach t eh climax so it is called plagioclimax community.

Question 46

what is primary succession?

Answer 46

colonisation of uninhabited terrain over time by a living organism

Question 47

what is secondary succession?

Answer 47

recolonisation of an area after earlier community has been removed

Question 48

pioneer species

Answer 48

A species that can colonise barren terrain.

Question 49

ways to measure / sample ecosystem

Answer 49

using quadrants and transects

Question 50

what can be calculated using quadrants?

Answer 50

abundance and distribution of species

Question 51

what should be decided before starting to sample? (quadrants)

Answer 51

- where to place the quadrats : to random sampling , coordinates , systematic sampling at regular distance - how many samples to take : take samples from across the habitat, make a cumulative frequency against quadrat number. The point where the curve levels off tell you how many quadrants to use

Question 52

what is the equation to estimate the size of the population of each species in the whole habitat?

Answer 52

mean number of individual of the species in each quadrat : fraction of the total habitat area covered by a single quadrat

Question 53

what method of sampling is used to look for changes in abundance and distribution of a species across a habitat?

Answer 53

transect

Question 54

what are the 2 approaches of using a transect?

Answer 54

line transect =at regular intervals make a note of which species is touching the tape belt transect = at regular intervals , place a quadrat next the line (interrupted belt transect) , or place a quadrate and move it along the line (continuous belt transect)