6.3.1 Ecosystems Flashcards by Phoebe Kellett

Define population

All the members of a single species which live in the same area

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Define Habitat

the area in which an organism lives

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Define Community

all the populations of different species which interact together in the same habitat

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Define Ecosystem

a community of organisms and the habitat in which it lives

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Define Producer

An organism which converts light energy into organic molecules. It is the first organism in the food chain

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Define Consumer

an organism which eats other organisms to gain energy

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Define Trophic level

the stage in a food chain made up of a particular group of organisms
e.g. producers and primary consumers

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Define Decomposers

organisms which feed on, and break down, dead organisms and waste materials
important role in nutrient recyling

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Name 3 Abiotic factors

-light intensity
-temperature
-pH of soil
-wind speed
-CO2/O2 levels

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Name 3 Biotic factors

-Predation
-Disease
-Food availability
-Interspecific competition
-Intraspecific competition
-Grazing?

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What is a food chain?

Shows which organisms feed on others within an ecosystem Illustrating the flow of energy from one organism to another

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Where does the energy in a food chain originate from?

The sun

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How is light energy captured and used by plants?

Green Plants convert it into glucose during photosynthesis
Glucose is then used in respiration which helps produce ATP for growth (increase in biomass)

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What is a primary consumer?

An organism which feeds on a producer

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What is a food web?

Shows the interaction of multiple interconnected food chains within an ecocsystem

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What is interdependence in a food web?

Refers to how organisms within a food web affect each other’s population sizes and survival.

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What is the role of decomposers in a food web?

Break down dead material
Allow nutrients to be recycled

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What is biomass?

Total mass of living matter in an organism or ecosystem

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Why is energy lost in energy transfer between trophic levels? (List 3 reasons)

Light energy is not fully absorbed by plants (some is the wrong wavelength or hits non-photosynthetic parts).
Not all parts of an organism are eaten (e.g., bones, roots, beaks).
Incomplete digestion (some energy is lost in faeces and passed to decomposers).

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List 3 ways in which consumers use a large proportion of biomass

-Respiaration
-Movement
-Maintaining body temperature

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Why do food chains rarely exceed 4-5 trophic levels?

Too much energy is lost at each trophic level, so insufficent energy available to support more levels

What is the official method for measuring energy transfer between trophic levels?

The organisms are dried in an oven to remove water, weighed, and the difference in biomass between trophic levels is calculated.

What are the key steps in measuring an estimate biomass in a food chain?

Select a sample area
Dry the organisms in an oven until mass remains constant.
Multiply the mas by the total area
The difference between trophic levels = amount of biomass transfer between organisms

What is a limitation of this estimate biomass measurement method?

Assumes that each consumer only consumes one type of organism
i.e. wouldn’t work for consumers which feed on other food sources

What is net productivity?

The amount of biomass available to the next trophic level

How is net productivity calculated?

Net Productivity = Gross Productivity (GP) – Respiratory Losses (R)

What does gross productivity refer to?

all the energy consumed by the organism

How is the Efficiency of energy transfer calculated?

Net productivity Divided Total energy received x100

What can farmers do to increase energy transferred from one trophic level?

-Small cages to restrict movement -Supply animals with high-energy feed to promote growth -Give animals antibiotics to reduce energy wasted to fight infections -Herbicides kill unwanted plants, reducing competition -Insecticides so less biomass lost by pests eating crops -Fungicides to reduce fungal infections

What are the main processes that release carbon dioxide into the atmosphere?

-Respiration -Combustion of fuels -Volcanic activity

How is CO₂ removed from the atmosphere?

Photosynthesis in plants

How does carbon get stored in the ocean?

Marine organisms use dissolved CO₂ to form calcium carbonate for shells, which can later form limestone and chalk.

What happens if decomposition does not occur?

Organic carbon can be buried and, over millions of years, converted into fossil fuels (e.g. coal, oil, gas).

Why is nitrogen important for living organisms?

Needed to make amino acids, proteins, and DNA.

In what form can plants absorb nitrogen?

Nitrates (NO₃⁻) from the soil.

What is nitrogen fixation?

Process of converting nitrogen gas (N₂) into ammonium ions (NH₄⁺) or nitrates (NO₃⁻).

Which bacteria convert N₂ to NH₄⁺

Azotobacter and Rhizobium

Which bacterias are involved in nitrification to convert NH₄⁺ to nitrites and then nitrates respectively?

Nitrosomonas and Nitrobacter

What is the Haber process, and how does it relate to the nitrogen cycle?

Converts nitrogen gas into ammonia (NH₃) for fertilisers, increasing soil nitrates.

What is ammonification?

The decomposition of organic matter by saprobionts, releasing ammonia (NH₃) into the soil.

What do Denitrifying bacteria do?

Use nitrates for respiration and returns N₂ to the atmosphere

What is succession?

The change in an ecological community over time, i.e from a sparse landscape to a stable community.

What are the two types of succession?

-Primary succession: community develops in the absence of soil. -Secondary succession : community develops where soil is present but the ecosystem has been disturbed.

What is a pioneer species, and why are they important?

The first organisms to colonise an ecosystem, e.g moss or lichen They change abiotic conditions, making it less hostile for new colonising species.

What happens after the pioneer species die and decompose?

Their decomposition forms humus, creating a basic soil that supports further growth, making the environment less hostile and more water is available. Small plants and shrubs can now survive

What happens after the small plants and shrubs die during succesion?

The soil becomes deeper and thicker. Larger plants can now survive Biodiversity increases

What is a Climax Community?

The final community formed, containing all plant and animal species that have colonised the land The most stable and complex ecosystem.

What is Deflected Succession?

Human activities prevent or interrupt succession, stopping a climax community from developing.

Why would you want to prevent succesion is come cases?

-Maintain biodiversity, some species may not survive in a climax community -Save endangered species -Maintaining Specific Habitats supporting species that cannot survive in more mature ecosystems -Cultural or Economic Value

What can be done to prevent succesion for conservation purposes?

-Grazing animals temporarily -Managed burning/controlled fires