Ecosystem, sampling and effect of human activity on the enviroment

Question 1

What is an ecosystem?

Answer 1

A natural unit consisting of living organisms (flora and fauna) and their interactions with each other and the non-living components of the habitat.

Ecosystems include different communities that interact with each other and their environment.

Question 2

What is a community in ecological terms?

Answer 2

A community is composed of populations of different species occupying the same habitat at the same time.

Communities are characterized by dynamic feeding relationships among species.

Question 3

Define a population.

Answer 3

A group of organisms of the same species occupying the same habitat at the same time.

Populations can vary in size and density.

Question 4

What is a species?

Answer 4

Organisms with similar characteristics that can interbreed to produce fertile offspring, sharing similar DNA and the same ecological niche.

The concept of species is fundamental in biology for classification.

Question 5

What is an ecological niche?

Answer 5

A particular role or function of an organism within its ecosystem, governed by its adaptation to the food supply, habitat, and abiotic factors present.

The niche is unique to each species and is not shared.

Question 6

True or False: An organism’s niche can be shared with other species.

Answer 6

False.

Each species has a unique niche that is not shared with others.

Question 7

Fill in the blank: An ecosystem consists of living organisms and their interactions with _______ components of the habitat.

Answer 7

non-living

Non-living components include physical factors such as soil, water, and climate.

Question 9

What are producers?

Answer 9

Producers are all autotrophic (‘self-feeding’) organisms that convert light energy into chemical energy through photosynthesis.

Question 10

What is the role of producers in food chains?

Answer 10

Producers produce organic compounds and form the basis of all food chains.

Question 11

Define consumers.

Answer 11

Consumers are heterotrophic organisms that break down large insoluble organic compounds into smaller soluble molecules for energy.

Question 12

What are primary consumers?

Answer 12

Primary consumers are herbivores.

Question 13

What are secondary and tertiary consumers?

Answer 13

Secondary and tertiary consumers are carnivores.

Question 14

What are saprobionts?

Answer 14

Saprobionts are bacteria and fungi that break down dead organisms and recycle nutrients in the environment.

Question 15

What is another term for saprobionts?

Answer 15

Saprobionts are also known as decomposers.

Question 16

What term should be used in exams instead of decomposers?

Answer 16

Use saprobionts or saprobiotic microorganisms in an exam.

Question 17

What do detritivores feed on?

Answer 17

Detritivores feed on detritus, which is decaying organic matter.

Question 18

Give an example of a detritivore.

Answer 18

An example of a detritivore is woodlice.

Question 19

What is the function of detritivores in the ecosystem?

Answer 19

Detritivores break down decaying matter into smaller pieces, increasing the surface area for decomposition by microbes.

Question 20

What is the significance of decomposition in ecosystems?

Answer 20

Decomposition aids the recycling of nutrients in the ecosystem.

Question 21

Describe method for biomass measurement

Answer 21

1. Heat all the plant material (removed from a known area) at 100O C for 15 minutes, and
   then weigh and record the mass. A lower temperature for a longer time-period can be
   used. Higher temperatures are not be used as this can cause organic compounds to burn.
2. Reheat at same temperature for the same period and reweigh.
3. Repeat until a constant mass is obtained which indicates all the water has been
   removed.
4. Divide the dry mass by the area from which the plant material was removed.
   To determine increase in biomass over time, repeat the above procedure removing all the
   plant material from equal areas of land over specified time-periods.

Question 22

Reason for not all sunlight being absorbed

Answer 22

Light misses the chloroplasts/chlorophyll/photosynthetic tissue

Some light which hits the chlorophyll is reflected/not absorbed

Only certain wavelengths of light are used in photosynthesis.

Question 23

Reason for not all energy being transferred?

Answer 23

Most energy is transferred to the environment in the form of heat released during respiration

not all parts of an organism are consumed or they are indigestible and are not
absorbed e.g. teeth and bones

loss occurs via excretory products

Question 24

Productivity in Animals (Consumers) calculated as?

Answer 24

N = I – (F + R)

Question 25

Why keeping animal confined increases the efficiency of energy conversion?

Answer 25

Movement restriction means less energy use in muscle contraction The environment is warmer so animals lose less heat and therefore respire less in order to maintain body temperature Also, food is highly controlled so that optimum nutrition is provided with no / little wastage. Food has a high energy content and high digestibility so more of the food is used to increase biomass

Question 26

How can you improve yield of animal live stock?

Answer 26

Selective breeding of animals to produce high yield varieties Using growth hormones to increase growth rates and biomass

Question 27

Interspecific competition?

Answer 27

Competition between different species

Question 28

Intraspecific competition?

Answer 28

Competition within a species

Question 29

How does nitrogen fixation happens?

Answer 29

Nitrogen fixing bacteria can fix nitrogen into ammonia/ammonium compounds N2 + 3H2 -> 2NH3 Some are in soil, some are in mutualistic relationship with leguminous plants

Question 30

What is and how happens ammonification?

Answer 30

Ammonification is the production of ammonia from dead organism Saprobiotic microorganisms also known as decomposers, cause decay and break down animal and plant proteins into ammonia which forms ammonium ions in the soil

Question 31

What is and how happens nitrification?

Answer 31

This is the oxidation of ammonia and ammonium ions in the soil into nitrites and then nitrates by nitrifying bacteria One group of nitrifying bacteria oxidise ammonium ions into nitrites and another group of nitrifying bacteria oxidise nitrites into nitrates NO2- is Nitrites NO3- is Nitrates Nitrates are then absorbed by plant roots

Question 32

Denitrification?

Answer 32

Conversion of nitrates into nitrogen by denitrifying bacteria Denitrifying bacteria reduce soil fertility by converting nitrates back into atmospheric nitrogen Denitrifying bacteria are anaerobic and increase in number in waterlogged soils Ploughing helps to aerate soil reducing the build up of denitrifying bacteria

Question 33

Key stages of the phosphorus cycle?

Answer 33

Most phosphorous is locked up in sediments and rocks but weathering causes rocks to release phosphate ions and other minerals. This inorganic phosphate is then distributed in soils and water. Plants absorb inorganic phosphate from the soil. The plants may then be consumed by animals. When the plant or animal dies, it decays, and the organic phosphate is returned to the soil. Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus. This process is known as mineralisation. Phosphorus in soil can end up in waterways and eventually oceans. Once there, it can be incorporated into sediments over time.

Question 34

Equation for capture release?

Answer 34

Estimated total = no of 1st sample * no of 2nd sample / no of recapture

Question 35

Assumption for capture release method?

Answer 35

Organisms mix randomly within the population Sufficient time must elapse between capture and recapture to allow random mixing. The less mobile the species the longer the time lapse must be. It is only applicable to populations whose movement is restricted geographically. Organisms disperse evenly within the geographical area of the population. Changes in population size as a result of immigration, emigration, births and deaths are negligible. Marking does not hinder the movement of the organisms or make them conspicuous to predators. A marking technique should be used that cannot be washed, rubbed or licked off between capture and recapture.

Question 36

Index of diversity equation?

Answer 36

d = N (N - 1)/ ∑n (n - 1) d = species diversity N = total number of organisms of all species n = total number of organisms of each species ∑ = the sum of

Question 37

Chi square equation?

Answer 37

X² = ∑ (observed - expected)² / expected

Question 38

What is 3 stages of succession?

Answer 38

Primary stage with primary coloniser called pioneer species that makes humus Then secondary stage which is more complex and add to humus Then climax community which is most stable and has dominant or co-dominant species with grates productivity/biomass and also more complex

Question 39

What is seres and seral stages?

Answer 39

Stage of succession and complete sequence of seres

Question 40

What is practice preventing stage of succession?

Answer 40

Grazing prevents succession beyond grassland as seedlings of herbaceous plants and shrubs are continually eaten Ploughing breaks seedlings up and they area buried preventing germination Natural events such as fires and floods

Question 41

Disadvantage of removing hedgerows?

Answer 41

When not covered with growing crop, the soil is much more exposed to wind erosion, and, if sloping, to erosion by rainwater. In drier parts of the country there can be considerable losses of the more fertile topsoil There is reduced flexibility of land use on farms which keep some animals, since fences have to be erected to keep them separate. There is also less shelter for the animals There is far less habitat and food resources for wildlife resulting in a decrease in species diversity. Predators that normally keep pests under control lose their habitat and as a result crops are exposed to large infestations by pests. Therefore farmers apply large amounts of pesticides which tend to reduce natural populations even further. They add diversity and interest to the landscape (aesthetic conservation reason) They act as corridors along which many species move and disperse themselves.

Question 42

Advantage of removing hedgerows?

Answer 42

The space previously taken up by hedges can be used for growing the crop, which increases the yield per unit area. Also there is no need to cut and maintain the hedges which reduces labour costs. It is easier to manoeuvre large machines, such as combine harvesters, which speeds up sowing seeds, harvesting and spraying It removes the shading effect of tall hedges which reduce crop yield by absorbing light, moisture and nutrients. It removes habitats that might harbour pests, diseases and weeds, especially over winter.

Question 43

How can you minimise damage of agriculture?

Answer 43

Use more organic manure, which improves soil structure by providing more humus so retaining more water. As the humus decays the nutrients are released more slowly so there is less chance of them being leached away. Delay the application of chemical fertilisers until the main growing season so that more is absorbed before it is washed away Leave crop stubble over the winter (i.e. plough later) – reduces soil erosion Rotate crops – growing a different crop year on year makes better use of minerals available at each soil depth. It also prevents the accumulation of crop-specific pests Practice set aside – leave areas of wilderness to develop Stop destroying hedgerows

Question 44

What is BOD?

Answer 44

Biochemical oxygen demand (BOD) The amount of dissolved oxygen needed by aerobic decomposers to break down organic materials

Question 45

How is BOD measured?

Answer 45

Measuring bacterial activity The more organic matter (e.g. sewage) in the water, the more aerobic saprophytic bacteria there will be

Question 46

What is DDT?

Answer 46

Specific pesticide that has devastating effects on some top carnivores, most notably birds Some birds disappeared completely from USA as eggshell becomes thinner due to hormonal change in calcium metabolism so lost of egg Effective against malaria but banned in developed countries

Question 47

phenoxyacetic acids?

Answer 47

Type of auxin that can be used as herbicide Selective, affects only dicotyledonous plants Interfere with growth by interfering with gene expression

Question 48

Stages of a biological control programme?

Answer 48

Identifying the pest species and tracing where it came from originally Finding natural enemies of the pest to become control agents Testing the control agents under careful quarantine to ensure that it will be: specific, not change its prey and become a pest itself, not introduce diseases and whether its life cycle allows it to develop into a population large enough to act as an economic control Breeding or mass culture of the control agent Development of the most effective distribution/release of the control agent Monitoring and evaluating the success of the programme

Question 49

Advantage of biological control?

Answer 49

Specific therefore highly effective against a particular pest Does not pollute Once introduced the control organism reproduces itself Pests do not become resistant Cheaper/more economical than repeated applications of chemicals

Question 50

Disadvantage of biological control?

Answer 50

Control agents can sometimes become pests themselves Hard to control Testing/screening for the correct organism can be expensive The control agent rarely eradicates the target species but once the prey fall to low numbers this may result in a drop in the population of control agents so it may be necessary to re-introduce the control agents ethically concerning e.g. the use of the myxomatosis virus against rabbits Possibility of resistance

Question 51

What is integrated pest management?

Answer 51

Combining chemical, cultural and biological methods with knowledge of pests population dynamics to control them

Question 52

Ways of preventing/control pests?

Answer 52

Chemical Biological Cultural Genetic engineering i.e. engineer to be resistant against pests Legalisation i.e. ban certain species to be brought by human in country

Question 53

What is info needed for successful integrated pest management?

Answer 53

Crop growth characteristics Type, number and life cycles of the pest Pest population dynamics and its relationship to crop damage Pest-host plant relationships Pest-predator relationships and their effect on pest population dynamics Effects of insecticides on crops, pests and non-target species