IB Biology, Option C2, Communities and Ecosystems

What do food webs show?

The full potential of food chains in an ecosystem and their trophic relationships

What do food chains show?

Flow of energy between trophic levels

What do energy pyramids show?

Transfer of energy per trophic level

How are energy pyramids limited?

Seasonal fluctuations, available prey, one level may represent many organisms

How much energy is passed down trophic levels?

10%

How much every is lost through trophic levels?

90%

How is energy lost between trophic levels?

Heat, growth, inedible parts of an organism, respiration

What does the food conversion ratio show?

How much dietary input produces a certain body mass

What is the formula for the food conversion ratio?

(Food fed / weight gained) x 100

Explain how food conversion ratios in livestock affect availability of food available for human consumption (4 points)

- the food conversion ratio shows how much dietary input produces a certain body mass

- human consumption will include that of meat, fish, eggs, milk

- the smaller the ratio needed the more food available from less resources / input. For example, it takes more grain to produce 1kg of beef than chicken or even insects

- some dietary choices are more sustainable than others

- some animals are more efficient than others

Define NPP (net primary productivity)

The amount of energy available in an ecosystem

How does high NPP affect food chains?

The higher the NPP the more energy available and therefore the more life can be sustained

How is energy transferred to the next trophic level? (2 ways)

- An organism is consumed by a primary, secondary, or tertiary consumer

- Dead organisms, faeces and organic tissue loss are passed on to decomposers

Define secondary production

The rate at which energy is used to make new organic molecules within heterotrophs

What is the formula for efficiency?

(Energy available after transfer / energy available before transfer) x 100

What two climate factors determine the type of ecosystem that can emerge?

Temperature, climate

Why is a climate's temperature important

It affects cellular respiration rate, photosynthesis and rainfall

Why is a climate's rainfall important?

All living things need water to live (metabolic reactions, transportation, the dissolving and absorbing of nutrients etc.)

What diagram shows nutrient method of storage?

Gersmehl nutrient cycle diagram

Draw a Gersmehl nutrient cycle diagram

Gain from precipitation. Gain from weathering.

⬇️ Biomass. ⬇️

↙️. ↘️

Fallout pathway Uptake pathway.

↙️. ↘️

Litter. 👉 Decay pathway. 👉 Soil.

👇. 👇

Loss by runoff. Loss by leaching

Define biomass

Total mass of living organisms / store of energy (standing crop) in an ecosystem (plant tissues per unit area)

How is biomass measured?

- Dry mass (kg / m^2)

- Ash weight

- Calories / unit area

Define litter

Organic matter in / on the soil (humus, leaf litter etc.)

Define soil

The top layer of earth (disintegrated rock, humus, water, air)

Does biomass, soil or litter have a higher ratio in rainforests, why?

Biomass, high temp and humidity allow fast rate of transfer between all stores and decomposition

Does biomass, soil or litter have a higher ratio in desert, why?

Soil, arid conditions slow litter to soil and soil to biomass transfer

Define climax community

The last species to colonise a system

Define primary succession

Plants grow where none have grown before

Define secondary succession

Plants grow where there was previous life destroyed (eg fire)

Define psammosere

Successions in a sand dune system

Define pioneer species

A species sparking primary succession in a system

Give 4 characteristics of a stereotypical pioneer species

- fast growing

- short life cycle

- providing micro habitats

- binding layers of soil for other plant colonisation and micro habitats

Outline primary succession

In bare ground there's no competition for light, space, nutrients, water

Bare ground:

- soil is mobile prone to erosion and loss

- bare soil absorbs and reflects heat so microclimates are extreme

- no plants to hold above ground moisture

- little humus to hold in ground moisture

- there are lower soil nutrient levels

Primary succession:

- intense plant competition

- plant cover provides protection from extreme climate protection

- vegetation creates a variety of microclimates

- plant cover and humus retain water

- soil nutrient levels increase

When is a community stable?

When energy usage and energy production are balanced

What is the formula for net production?

Gross production - respiration