Organisation of an ecosystem

விளையாடிக் கற்றுக்கொள்ளுங்கள்

ஆற்றல் சம்பாதிக்க இந்த கேள்விகளுக்குப் பதிலளியுங்கள், பின்னர் மீன் பிடித்து ஆராயுங்கள். கணக்கு தேவையில்லை.

கல்வியாளர்களுக்கு: Organisation of an ecosystem (Science, Biology)-க்கான தயாரான பாட ஸ்லைடுகள், திருப்புதல் குறிப்புகள் — உங்கள் பாடத்தில் அவற்றைப் பயன்படுத்தவும், அல்லது கற்பவர்கள் நேரலை விளையாட்டாக விளையாடும் ஊடாடும் வகுப்பு செயல்பாடாக தலைப்பை இயக்கவும்.

பாட குறிப்புகள்

Levels of Organisation

Producers are photosynthetic organisms that make biomass for life on Earth, usually green plants or algae.
Producers make glucose by photosynthesis using light energy from the Sun, then use it to build other biological molecules that form their biomass.
Every food chain starts with a producer at the first trophic level, which is always the largest level.
In extreme environments such as underwater volcanic vents, producers are chemoautotrophs that make organic molecules without sunlight.
A food chain shows feeding interactions and the transfer of energy from one organism to the next.
The arrows in a food chain show the transfer of energy from one level to the next, not 'eats'.
The source of all energy in a food chain is light energy from the Sun.

Consumers and Feeding Relationships

Primary consumers eat producers and are herbivores or omnivores.
Secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers; both are carnivores or omnivores.
Predators are consumers that kill and eat other animals; the animals they eat are prey.
In a stable community, predator and prey numbers rise and fall in cycles.
Predator and prey cycles are out of phase: the predator peak lags behind the prey peak because it takes time for predators to reproduce.
As prey numbers rise, predator numbers increase; as predators increase, prey numbers then fall.

A savanna food web showing feeding relationships among producers (tree, grass, shrub) and consumers up to top predators (lion, leopard).

Investigating Ecosystems with Quadrats

Ecology studies the distribution and abundance of species and their interactions with each other and the abiotic environment.
Quadrats are square frames of wood or wire, often 0.25 m² or 1 m², placed on the ground to record the organisms inside.
Quadrats measure abundance by recording the number of individuals of a species, species richness, or percentage cover.
Percentage cover is used when individuals are hard to count, such as grass or moss.
When estimating percentage cover, count a square if more than half of it is covered by the species.
Quadrats are placed randomly to avoid bias, using a grid and a random number generator.
Sampling reduces the time spent counting, but the sample must be large enough and unbiased to represent the whole population.

Transects and Estimating Population Size

A transect measures how the abundance of a species changes along a changing habitat.
A tape measure is laid through the habitat and a quadrat is placed at regular intervals, such as every 5 metres.
At each interval you can record the number of individuals, species richness or percentage cover.
Transects are useful for investigating how an abiotic factor such as light intensity, moisture, soil depth or altitude affects a species.
To estimate population size, calculate the mean number per quadrat, then scale it up to the total area.
You should understand mean, mode and median, calculate arithmetic means, and plot graphs with suitable scales.

The Carbon Cycle

Elements such as carbon are finite on Earth, so they must be recycled to build future organisms.
Carbon is removed from the atmosphere as carbon dioxide by plants and algae during photosynthesis.
Carbon passes to animals and microorganisms when they feed on plants and algae.
Carbon returns to the atmosphere as carbon dioxide during respiration by plants, animals and microorganisms.
If organisms die where decomposers are absent, their carbon can form fossil fuels over millions of years.
Combustion of wood or fossil fuels releases carbon dioxide back into the atmosphere.
Remember that plants respire too, so they also return carbon dioxide to the atmosphere.

The carbon cycle

The Water Cycle

The water cycle provides fresh water for plants and animals on land before it drains into the seas.
Water enters the atmosphere by evaporation from oceans, rivers and lakes, driven by the Sun's energy.
Transpiration from plants also releases water vapour into the air.
Rising moist air cools, and water vapour condenses to form clouds.
Water returns to Earth as precipitation such as rain, snow and sleet.
Water is continuously evaporated and precipitated, and all life depends on water, including for photosynthesis.

Decomposition and the Role of Microorganisms

Decomposers break down dead organisms and waste products, returning materials to the environment.
The main groups of decomposers are bacteria and fungi; detritus feeders such as earthworms and woodlice also help.
Decomposition (decay) recycles carbon and mineral ions such as magnesium and nitrates.
Microorganisms return carbon to the atmosphere as carbon dioxide when they respire.
Temperature, water availability and oxygen availability affect the rate of decay.
Light intensity does not affect the rate of decay.
There is a finite number of elements on Earth, so recycling by decomposition is essential.

Uses of Decomposition

Gardeners and farmers provide optimum conditions of warmth, moisture and oxygen for rapid decay of waste plant matter.
The compost produced is used as a natural fertiliser for growing plants and crops.
Once spread on soil, compost is broken down further, recycling minerals such as magnesium and nitrates for plant growth.
Anaerobic decay occurs when microorganisms break down material without oxygen.
Anaerobic decay produces methane and carbon dioxide, together called biogas.
Methane can be burned as a fuel: methane + oxygen → carbon dioxide + water.
Biogas generators are large containers where plant or animal waste decays anaerobically to produce methane.

Required Practical: Decay in Milk

This practical investigates the effect of temperature on the rate of decay of fresh milk by measuring pH change.
Bacteria in milk carry out anaerobic respiration, producing lactic acid which lowers the pH.
As temperature increases, the rate of decay increases up to a point, because of increased kinetic energy and enzyme activity.
Over time the rate of decay decreases as bacteria run out of sugars to respire, so the pH stops changing.
The rate of decay is calculated as the pH change per unit time.
Storing milk at low temperature slows decay, which is why milk should be kept refrigerated.

Impact of Environmental Change

Environmental change can alter the distribution of species — where organisms live.
Key changing factors are temperature, availability of water and composition of atmospheric gases.
These changes may be seasonal, geographic or caused by human interaction.
As average temperatures rise with climate change, some plant, bird and insect species are spreading northwards into new areas.
Wildebeest migrate north and south following the rainfall, which provides fresh grazing and water.
Oxygen is needed for aerobic respiration; some aquatic animals such as fish need water with high oxygen concentrations.
Carbon dioxide is needed for photosynthesis, and some species such as lichen are sensitive to air pollution like sulphur dioxide.

ஸ்லைடுகள்

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பதிவு செய்க — இலவசம்உள்நுழைக

பயிற்சி கேள்விகள்

இலவச முன்னோட்டம் — 64-இல் 8 கேள்விகள். அனைத்தையும் பார்க்க பதிவு செய்யவும்.

1.Which process is carried out by all ecological producers?
Easy
- ARespiration
- BPhotosynthesis
- CDecomposition
- DCombustion
2.Which of the following best describes a grazing animal in a food chain?
Easy
- APrimary consumer
- BSecondary consumer
- CProducer
- DHerbivorous predator
3.Which of the following sketch graphs best represents the fluctuations in numbers of predators versus the numbers of prey in a feeding relationship?
Easy
- APredator and prey numbers peak at the same time
- BPredator numbers peak before prey numbers
- CPrey numbers peak before predator numbers, with the two cycles out of phase
- DPredator and prey numbers remain constant over time
4.Which of the following is the name for the sampling method where quadrats are laid down along a straight line to sample how wildlife varies along that line?
Easy
- ARandom sampling
- BTransect
- CQuadrat
- DBelt transect
5.A scientist wants to use quadrats to investigate species in a field. Which technique is best for deciding where to place the quadrats to collect the sample?
Medium
- APlace quadrats down in areas where the species under study is present in large numbers.
- BPick the sunniest areas because more life will grow there.
- CClose your eyes, throw the quadrat and sample the area where it lands.
- DCreate a grid of the field and use a random number generator to find coordinates to place the quadrat down.
6.Which of the following processes is the one by which carbon enters the carbon cycle by being incorporated into the biomass of producers?
Medium
- ADecomposition
- BPhotosynthesis
- CAerobic respiration
- DEvaporation
7.Which of the following is not a factor that affects the rate of decay of dead biomass by microorganisms?
Easy
- ATemperature
- BLight intensity
- CWater availability
- DOxygen availability
8.What do decomposers do?
Easy
- AThey use light energy to make glucose
- BThey break down dead plant and animal matter
- CThey transport oxygen around the body
- DThey absorb water and mineral ions from the soil

மேலும் கேள்விகள்

9.Which of the following are processes that return carbon dioxide to the atmosphere? (select all that apply)
Medium
- APhotosynthesis
- BRespiration by plants
- CCombustion of fossil fuels
- DDecomposition by microorganisms
- EEvaporation of water
10.In a food chain, the arrows represent the transfer of energy from one organism to the next.
Easy
True or false?
11.In a stable community, predator and prey populations always peak at exactly the same time.
Easy
True or false?
12.Match each ecological term to its correct definition.
Medium
- Producer
- Primary consumer
- Decomposer
- Predator
- An organism that breaks down dead material and waste
- An organism that makes its own food by photosynthesis
- An animal that kills and eats other animals
- An organism that feeds directly on producers
13.Arrange the following events in a woodland food chain into chronological order, starting with the event that happens first.
Medium
- Woodland birds feed on ladybirds
- Aphids feed on tree sap
- Birds of prey feed
- Trees photosynthesise and produce food
- Ladybirds feed on aphids
14.Which of the following is the correct definition of a quadrat?
Easy
- AA square frame used to sample organisms in a habitat
- BA line along which samples are taken
- CA type of net used to catch insects
- DA chemical used to test for starch
15.Decomposers include both bacteria and fungi.
Easy
True or false?
16.Which of the following is not a way in which water enters the atmosphere in the water cycle?
Medium
- AEvaporation from oceans
- BTranspiration from plants
- CCondensation forming clouds
- DEvaporation from rivers and lakes
17.Which of the following environmental changes can affect the distribution of species in an ecosystem? (select all that apply)
Medium
- ATemperature
- BAvailability of water
- CComposition of atmospheric gases
- DLight intensity
- EHuman interaction
18.Which of the following is the correct equation for calculating the rate of decay?
Easy
- ARate = change in pH × time
- BRate = change in pH ÷ time
- CRate = time ÷ change in pH
- DRate = change in pH + time
19.In a biogas generator, decomposing microorganisms must be kept in anaerobic conditions to produce methane.
Easy
True or false?
20.Which of the following is the main role of microorganisms in the carbon cycle?
Medium
- AThey take carbon dioxide out of the atmosphere by photosynthesis.
- BThey release carbon dioxide into the atmosphere by respiration during decomposition.
- CThey convert nitrogen gas into nitrates.
- DThey evaporate water into the atmosphere.
21.In a food chain, which organism is always at the first trophic level?
Medium
- APrimary consumer
- BProducer
- CSecondary consumer
- DTertiary consumer
22.Which of the following statements about food chains are correct? (select all that apply)
Medium
- AThe arrows show the transfer of energy from one organism to the next.
- BFood chains always begin with a producer.
- CPrimary consumers are always carnivores.
- DThe source of all energy in a food chain is light energy from the Sun.
- EDecomposers are always the first organism in a food chain.
23.Consumers that kill and eat other animals are called prey.
Easy
True or false?
24.Match each term about feeding relationships to its correct description.
Easy
- Producer
- Primary consumer
- Predator
- Prey
- An organism that makes its own food by photosynthesis
- A herbivore that eats producers
- An animal that kills and eats other animals
- An animal that is killed and eaten by another animal
25.The numbers of predators and prey in a stable community rise and fall in cycles.
Easy
True or false?
26.Which of the following statements about quadrats are correct? (select all that apply)
Medium
- AA quadrat is a square frame placed on the ground.
- BA quadrat can be used to measure the abundance of plants.
- CQuadrats should always be placed in the area where the species is most common.
- DA quadrat can be used to measure percentage cover.
- EA quadrat is a long tape laid in a straight line.
27.Arrange the stages of the water cycle into the correct order, starting with the process that puts water vapour into the atmosphere.
Medium
- Water vapour condenses to form clouds
- Water evaporates from oceans, rivers and lakes
- Water falls as precipitation
- Water is taken up by plants and animals
28.Which of the following conditions would increase the rate of decay of dead plant material? (select all that apply)
Medium
- AWarm temperature
- BVery dry conditions
- CPlenty of oxygen available
- DWater available
- ENo oxygen available
29.A species of butterfly is found only in the warm south of a country. Over many years the average temperature in the north increases. Which of the following is the most likely effect on the distribution of the butterfly?
Medium
- AIts distribution spreads northwards into areas it could not previously inhabit.
- BIts distribution disappears completely.
- CIts distribution stays exactly the same.
- DIts distribution moves southwards into cooler areas.
30.A student wants to investigate how the number of dandelions changes as distance from a large tree increases. Which of the following is the best method?
Medium
- APlace a quadrat at every metre along a tape measure laid out from the tree.
- BPlace all the quadrats close to the tree.
- CPlace quadrats only where the most dandelions are growing.
- DCount every dandelion in the whole field by eye.
31.Which of the following are examples of environmental changes that can affect the distribution of species in an ecosystem? (select all that apply)
Medium
- AA rise in average temperature
- BA change in the availability of water
- CA change in the composition of atmospheric gases
- DA change in the number of chromosomes in a species
- EA change in the colour of a flower
32.A student wants to know how the abundance of a plant species changes as they walk from a shaded woodland into an open field. Which sampling method is most suitable?
Medium
- APlace quadrats randomly across the whole area using a random number generator
- BLay out a tape measure and place quadrats at regular intervals along it
- CCount all the plants in the largest quadrat they can find
- DTake a single quadrat sample from the middle of the field
33.A gardener wants to make compost quickly from dead leaves. Which set of conditions would give the fastest decay?
Medium
- ACold, dry, no oxygen
- BWarm, moist, plenty of oxygen
- CWarm, dry, no oxygen
- DCold, moist, plenty of oxygen
34.Which of the following statements about the carbon cycle are correct? (select all that apply)
Medium
- ACarbon enters living organisms when producers photosynthesise.
- BCarbon is passed to animals when they feed on plants.
- CCarbon is returned to the atmosphere by respiration of plants, animals and microorganisms.
- DCarbon is returned to the atmosphere by photosynthesis.
- ECarbon is only cycled through living organisms, not through the atmosphere.
35.A food chain is: grass → rabbit → fox. Which organism is the secondary consumer?
Medium
- AGrass
- BRabbit
- CFox
- DSun
36.In a food chain, the arrows show the direction of energy transfer from one organism to the next.
Easy
True or false?
37.A graph shows the numbers of a predator and its prey over many years. The prey population peaks in year 4 and the predator population peaks in year 5. Which statement best explains the one-year delay?
Medium
- APredators always eat prey one year after they are born.
- BIt takes time for predators to reproduce and increase in number after more prey become available.
- CPrey numbers only increase after predators have decreased.
- DThe predator and prey populations are not linked.
38.A species of fish lives in a lake. A factory releases waste into the lake, causing a rapid growth of aerobic microorganisms. Which sequence of events is most likely to reduce the fish population?
Hard
- AMicroorganisms produce oxygen → fish have too much oxygen → fish die
- BMicroorganisms use up oxygen during respiration → oxygen concentration falls → fish cannot respire aerobically
- CMicroorganisms produce carbon dioxide → water becomes too cold → fish die
- DMicroorganisms block sunlight → plants cannot photosynthesise → fish have no food
39.A student uses a 0.25 m² quadrat to sample daisies in a meadow. The mean number of daisies per quadrat is 4. The meadow has an area of 500 m². Which of the following is the best estimate of the total number of daisies in the meadow?
Medium
- A2000
- B8000
- C500
- D125
40.A student investigates the effect of light intensity on the distribution of a plant species. They place a 1 m² quadrat every 2 m along a 20 m transect from a shady woodland edge into an open field. Which of the following is the best reason for placing the quadrats at regular intervals rather than randomly?
Hard
- ATo ensure the sample is unbiased
- BTo measure how the abundance changes along the environmental gradient
- CTo increase the total area sampled
- DTo avoid counting the same plant twice
41.An area of 10,000 m² is to be sampled using 1 m² quadrats. Calculate the number of quadrats needed to sample 2% of the overall area.
Medium
42.Complete the sentence about the carbon cycle.
Easy
Carbon is taken out of the atmosphere by plants during ____, and returned to the atmosphere by ____ in plants, animals and microorganisms.
43.Complete the definitions using the correct ecological terms.
Easy
A. The number of individuals of one species found in a sample is called ____. B. The geographical locations of all the members of a population is called ____.
44.Name the piece of equipment a student should use to count the number of dandelion plants in a sample area.
Easy
45.A student placed a 1 m² quadrat at 10 random positions in a field. The number of dandelions counted in each quadrat was: 6, 3, 8, 5, 4, 7, 2, 6, 5, 4. Calculate the mean number of dandelions per quadrat.
Medium
46.Use the mean number of dandelions per quadrat from the previous question (5) to estimate the total number of dandelions in the whole field. The field has an area of 400 m² and each quadrat is 1 m².
Medium
47.Complete the sentence about the water cycle.
Easy
Water enters the atmosphere as water vapour by evaporation and ____. It returns to Earth as ____.
48.A milk sample falls by 2.4 pH units over 8 minutes. Calculate the rate of fall of pH in pH units per minute.
Medium
49.Calculate the mean number of daisies per quadrat.
Medium
50.Estimate the total number of daisies in the whole field.
Medium
51.A student sets up a decay experiment with milk at 25°C. The pH falls from 7.0 to 4.6 over 6 hours. Calculate the rate of fall of pH in pH units per hour.
Medium
52.Name the process by which plants and algae take carbon dioxide out of the atmosphere.
Easy
53.Over 97% of the Earth's water is salty so will not sustain life on land, which requires fresh (unsalted) water. With reference to the water cycle, explain how salty ocean water is converted to reach land as fresh water in nature.
Medium
54.In an investigation into the effect of temperature on the decomposition of milk, lipids in the milk are converted to fatty acids and glycerol by the enzyme lipase. The experiment is set up with an initial pH of 8.0 which then fell as the experiment progressed. Explain the fall in pH levels during the experiment.
Medium
55.In an investigation into the effect of temperature on the decomposition of milk, lipids in the milk are converted to fatty acids and glycerol by the enzyme lipase, and phenolphthalein is used in the reaction mixture. Describe the role of phenolphthalein in this experiment.
Medium
56.In a separate experiment, scientists measured the rate of decay of <0.05 pH units per minute at 3°C. Suggest how this information could be used to advise consumers about the correct storage of milk as a food source.
Medium
57.Explain why the rate of decay is faster at 35°C than at 10°C.
Medium
58.An area of 10,000 m² is to be sampled using 1 m² quadrats. Calculate the number of quadrats needed to sample 2% of the overall area.
Medium
- A200 quadrats
- B180 quadrats
- C240 quadrats
- D220 quadrats
59.A student placed a 1 m² quadrat at 10 random positions in a field. The number of dandelions counted in each quadrat was: 6, 3, 8, 5, 4, 7, 2, 6, 5, 4. Calculate the mean number of dandelions per quadrat.
Medium
- A6 dandelions
- B5 dandelions
- C7 dandelions
- D4 dandelions
60.Use the mean number of dandelions per quadrat from the previous question (5) to estimate the total number of dandelions in the whole field. The field has an area of 400 m² and each quadrat is 1 m².
Medium
- A2400 dandelions
- B1800 dandelions
- C2000 dandelions
- D2200 dandelions
61.A milk sample falls by 2.4 pH units over 8 minutes. Calculate the rate of fall of pH in pH units per minute.
Medium
- A-0.7 pH units per minute
- B2.3 pH units per minute
- C0.3 pH units per minute
- D1.3 pH units per minute
62.Ten quadrats were placed in a field and the daisies in each were counted. The ten counts add up to 40 daisies in total. Calculate the mean number of daisies per quadrat.
Medium
- A4 daisies
- B6 daisies
- C5 daisies
- D3 daisies
63.Estimate the total number of daisies in the whole field.
Medium
- A1800 daisies
- B2200 daisies
- C2000 daisies
- D2400 daisies
64.A student sets up a decay experiment with milk at 25°C. The pH falls from 7.0 to 4.6 over 6 hours. Calculate the rate of fall of pH in pH units per hour.
Medium
- A0.4 pH units per hour
- B-0.6 pH units per hour
- C1.4 pH units per hour
- D2.4 pH units per hour

ஃப்ளாஷ் கார்டுகள்

What is a producer in a food chain?

A photosynthetic organism that produces its own food using energy from the Sun, making glucose by photosynthesis. Producers are always at the start of a food chain.

What do the arrows in a food chain represent?

The transfer of energy (or biomass) from one organism to the next, not simply 'eats'.

What is a primary consumer?

An organism that feeds on producers. They are herbivores or omnivores.

What is a secondary consumer?

An organism that feeds on primary consumers. They are carnivores or omnivores.

What is a tertiary consumer?

An organism that feeds on secondary consumers. They are carnivores or omnivores.

What is a quadrat?

A square frame (e.g. 0.25 m² or 1 m²) placed on the ground to sample the organisms within it. It is used to measure abundance of plants or slow-moving animals.

What is a transect?

A line (e.g. a tape measure) set up through a habitat along which quadrats are placed at regular intervals to investigate how abundance changes with a factor.

Why should quadrats be placed randomly when sampling?

To avoid bias, so the sample is representative of the whole population. Randomness can be achieved using a grid and a random number generator.

How is percentage cover estimated using a quadrat?

The approximate percentage of the quadrat area in which a species is found is recorded. A square is counted if more than half of it is covered by the species.

What is the mean?

The sum of all values divided by the number of values. It is a measure of average.

What is the median?

The middle value when all values are arranged in order. If there is an even number of values, it is the mean of the two middle values.

What is the mode?

The value that appears most frequently in a set of data.

How do you estimate total population size from quadrat data?

Calculate the mean number of individuals per quadrat, then multiply by the total area divided by the quadrat area.

What is the role of microorganisms in the carbon cycle?

Decomposers break down dead organisms and waste, returning carbon to the atmosphere as carbon dioxide during respiration, and mineral ions to the soil.

What is decomposition?

The breaking down and digestion of biological material (waste products and dead organisms) by decomposers such as bacteria and fungi.

What three factors affect the rate of decay?

Temperature, water availability, and oxygen availability.

How does temperature affect the rate of decay?

As temperature increases, the rate of decay increases (up to an optimum) because the kinetic energy and enzyme activity of decomposers increase.

How does water availability affect the rate of decay?

Decomposers require water for their biological processes; without sufficient water, decay slows down.

How does oxygen availability affect the rate of decay?

Aerobic decomposers require oxygen for respiration; without oxygen, decay is slower and anaerobic decay may occur.

What is biogas and how is it produced?

Biogas is mainly methane (and carbon dioxide) produced by anaerobic decay of biological material. It can be burned as a fuel.

What is the water cycle?

The continuous movement of water between oceans, atmosphere, and land through evaporation, transpiration, condensation, and precipitation, providing fresh water for life on land.

How does the water cycle provide fresh water?

Water evaporates from oceans and transpires from plants, condenses to form clouds, and falls as precipitation (rain, snow, sleet) onto land as fresh water.

What is the carbon cycle?

The recycling of carbon through ecosystems: carbon dioxide is taken in by photosynthesis, passed through food chains, and returned to the atmosphere by respiration and combustion.

How do predators and prey populations change over time?

Their numbers rise and fall in cycles, with the predator population peaking after the prey population because it takes time for predators to respond to changes in prey numbers.

What environmental changes can affect the distribution of species?

Changes in temperature, availability of water, and composition of atmospheric gases. These may be seasonal, geographic, or caused by human activity.

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