Organisation of an Ecosystem

Define population

A species that occupy the same habitat.

Define habitat

The place in which an organism lives.

Define community

Populations of different species interacting.

Define ecosystem

The interactions between the biotic and abiotic factors in an area.

What do food chains show?

Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.

Define biomass

The total mass of living material.

What are trophic levels?

The stages in a food chain.

What do arrows in a food chain represent?

The direction of biomass transfer.

Describe a simple food chain

producer → primary consumer → secondary consumer → tertiary consumer.

What is a producer?

An organism that makes its own food.

What types of organisms are primary producers?

Photosynthetic organisms like green plants and algae that trap energy from the sun.

What is a primary consumer?

An organism that feeds on producers.

What is a secondary consumer?

An organism that feeds on primary consumers.

What is a tertiary consumer?

An organism that feeds on secondary consumers.

What is a predator?

A consumer that kills and eats other animals.

What is prey?

An animal that is killed and eaten by another animal.

Describe the pattern of predators and prey in a stable community

The numbers of predators and prey rise and fall in cycles.

Why are producers the first trophic level?

* Producers provide all biomass for the food chain (production of glucose via photosynthesis).


* The rest of the food chain involves the transfer of this biomass.

What piece of apparatus is used to measure the abundance and distribution of organisms in an area?

Quadrat

What piece of apparatus is used to study the distribution of organisms across a gradient?

Belt transect

When considering the abundance of organisms, what is meant the term “mean”?

The average number of organisms.

How is the arithmetic mean calculated?

Sum of each number of each organism/the total number of each type of organism

When considering the abundance of different organisms, what is meant by the term “mode”?

The most populous organism

When considering the abundance of organisms, what is meant by the term “median”?

The organism that represents the middle value when the numbers of each organism are arranged from lowest to highest.

Describe how materials cycle through the living and non-living components of an ecosystem

* Organisms take in elements from their surroundings e.g. soil, air.
* Elements converted to complex molecules which become biomass.
* Elements transferred along food chains.
* Elements returned to environment during excretion and decomposition of dead organisms.

Give 3 molecules which are cycled through ecosystems

Oxygen, carbon dioxide and water.

Describe the carbon cycle

* starts with carbon dioxide in the atmosphere
* Plants fix carbon dioxide into organic molecules during photosynthesis.
* The organic carbon-containing molecules are passed onto organisms that eat the plants.
* Carbon dioxide is released back into the atmosphere by respiration from animals and plants.
* Burning fossil fuels also releases carbon dioxide into the atmosphere.

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1. CO2 is removed from the atmosphere via plants & algae which use it in photosynthesis. This is used to make glucose which turns into carbs. 
2. Plants and algae also respire, so some CO2 returns back to atmosphere. 
3. These plants and algae get eaten by other animals, and some carbon becomes part of the fats and proteins in their bodies. In other words, this carbon moves through the food chain.
4. Animals also respire, so some CO2 returns back to atmosphere. 
5. When animals, plants and algae die, microorganisms and detritus feeders feed on their remains. These also respire, so CO2 back to atmosphere, 
6. Detritus feeders and MO’s also feed on waste and faecal matter. 
7. When combusting fossil fuels and wood, CO2 retunes back to atmosphere

detail carbon cycle

Carbon Dioxide in the atmosphere

plants and algae take in carbon dioxide from the atmosphere in photosynthesis

the carbon is used to make carbohydrates, fast and proteins which make up the cells of plants and algae

plants and algae respire so some of the carbon dioxide is released back to the atmosphere as carbon dioxide

plants and algae can be eaten by animals

these animals are eaten by other animals

at this point the carbon in the plant becomes part of the carbohydrates, fats and proteins in the cells

animals respire and some of the carbon is released back to the atmosphere as carbon dioxide

animals release waste products such as faeces

eventually all animals and plants die- no we have carbon in waste products and dead remains

these are broken down by decomposing microorganisms eg bacteria and fungi

when decomposers carry out respiration the carbon in the waste and dead remains is returned to the atmosphere as carbon dioxide

decomposers cannot work effectively when there is a lack of oxygen then the carbon in dead remains can slowly be converted into fossil fuels

combusting fossil fuels releases a large amount of carbon dioxide back to the atmosphere

why are decomposers important

they cycle materials through an ecosystem and return carbon to the atmposhere as carbon dioxide, they release mineral ions to soil

Why is the carbon cycle important?

Carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells.

Describe the water cycle

* Water from lakes and oceans evaporates.
* The evaporated water condenses into clouds and returns to earth as precipitation.
* The water from precipitation is useful for life on land.
* The water then returns to rivers and oceans through surface runoff.

detail water cycle

1. salt water in ocean
2. energy in sun causes water to evaporate from the surface of the sea
3. the water vapour travels into the air and oils down
4. when it cools the water vapour condenses tp form clouds
5. the water in clouds falls to the ground as precipitation (rain, snow,hail, sleet) all forms of precipitations contains fresh water
6. once the water hits the ground some of it evaporates into the atmosphere as water vapour
7. some of the water passes through rocks and forms aquifers
8. a lot of the water forms rivers or streams
9. the water in rivers and streams eventually drains back into the sea
10. plants take up water in their roots this water moves up the plant In the xylem and passes out the leaves as water vapour- transpiration
11. animals take in water through drinking and food
12. realise water in their urine, faeces and when they exhale

Why is the water cycle important?

Living organisms require water and the water cycle provides organisms on land with a continuous supply of water.

Why are microorganisms important for the cycling of materials through an ecosystem?

Microorganisms (bacteria and fungi) return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter. The decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use e.g. plants use mineral ions for growth.

What is meant by decomposition?

The breakdown of dead materials into simpler organic matter

How do decomposers break down dead matter?

Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.

What are the two types of decomposition?

Aerobic decomposition (with oxygen)

Anaerobic decomposition (without oxygen)

what is anaerobic decay

produces a mixture of gases including methane (biogas)

What factors affect the rate of decomposition?

* Oxygen availability
* Temperature
* Water content

Why is oxygen required for decomposition?

Most decomposers require oxygen for aerobic respiration.

How does the availability of oxygen affect the rate of decomposition?

* decomposers carry out aerobic respiration and this requires a good supply of oxygen
* As oxygen levels increase, the rate of decomposition increases.
* As oxygen levels decrease, the rate of decomposition decreases.

Why can decomposition still occur in the absence of oxygen?

Some decomposers respire anaerobically.\* \*However, the rate of decomposition is slower as anaerobic respiration produces less energy.

How does soil water content affect the rate of decomposition?

Decomposers require water to survive:

* In moist conditions the rate of decomposition is high becuase many of the chemical reactions in decay require water


* In waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases.

Why does decomposition require water?

Water is required for the secretion of enzymes and absorption of dissolved molecules.

How does temperature affect the rate of decomposition?

faster at warmer temperatures because decomposers use enzymes to break down plant materials ad these enzymes work faster in warm conditions

Decomposers release enzymes:

* Rate highest at 50°C (optimum temperature for enzymes).
* Lower temperatures, enzymes work too slowly, rate decreases.
* High temperatures, enzymes denature, decomposition stops.

How is the rate of change calculated when considering the decay of biological material?

Rate of change = Change in value/ Change in time

Where value is a measurable variable associated with the decay of the material

What is compost?

The nutrient-rich product of the rapid decay of waste biological material (dead plants and animal waste) in optimum conditions set by gardeners and farmers.

How is compost used?

Used as natural fertiliser to promote growth of crops or garden plants.

Describe how biogas generators work

Biogas generators provide methane gas for fuel through anaerobic decomposition that occurs in animal waste.

Describe how environmental conditions affect communities

* Environmental conditions e.g. temperature, soil pH, light intensity affect the abundance and distribution of organisms within communities.
* e.g rising global temperatures have been linked to the extinction of frog species (their thin skin makes them more vulnerable to temperature changes).

How can different temperatures be bad for certain communities?

* If the temperature is too low, growth will be slower as organisms will use more energy to stay warm


* If the temperature is too high, organisms can die and water will become limited as evaporation increases

How can changes in water levels affect ecosystems?

* Animals may have to migrate to find water.
* Melting ice caps may destroy the habitats of some animals (either animals living in icy regions or by sea level rise).

How can atmospheric gases affect ecosystems?

* Some organisms cannot survive when certain gases are present.
* Polluted water can cause illness to animals that drink it.

What detrimental impacts can sulfur dioxide have on the environment?

* Formed when fossil fuels containing impurities are burnt.
* Sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources.

What detrimental impacts can carbon monoxide have on the environment?

* Carbon monoxide is formed from the incomplete combustion of fossil fuels.
* Carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen.
* Too much exposure can cause unconsciousness and death.

Name 5 greenhouse gases

* Water vapour
* Carbon dioxide
* Nitrous oxide
* Methane
* CFCs

Give 3 human activities that contribute to greenhouse gases

* Burning fossil fuels
* Deforestation
* Large scale livestock farming

How do greenhouse gases lead to global warming?

* Greenhouse gases allow heat from the sun to enter the atmosphere.
* The gases act as a ‘blanket’ and trap the heat in the atmosphere.

State 3 negative consequences of global warming

* Sea level rise caused by melting icebergs.
* Disrupted farming and agriculture.
* Increased spread of diseases in warmer climates.