Ecosystems

Biomass

The total mass of living material in a specific area at a given time. Usually measured in gm-2. Fresh mass is quite easy to assess

Calorimetry

The chemical energy store in a dry mass can be estimated using this technique. When a sample of dry material is weighed and then burnt in pure oxygen within a sealed container (bomb). The bomb is surrounded by a water bath and the heat of combustion causes a temperature rise. This can be used to work out the energy released from the mass of burnt biomass.

Producer

Photosynthetic organism that manufacture organic substances using light energy

Consumer

An organism that obtains its energy by feeding on (consuming) other organisms. Primary consumers eat producers. Secondary consumers eat primary consumers. Tertiary consumers eat secondary consumers

Extracellular digestion

When saprobionts release enzymes externally which break down large biological molecules into smaller ones which are then absorbed by digestion or active transport.

Trophic level

Each stage in a food chain

GPP

Gross primary production which is the total quantity of the chemical energy store in plant biomass

NPP

Gross primary production – respiratory losses. The chemical energy store which is left when these losses to respiration have been taken into account. This is available for plant growth and reproduction and available to other trophic levels in the ecosystem (such as consumers and decomposers).

Respiratory losses

Taken away from GPP to calculate NPP.

Food chain

Describes a feeding relationship in which the producers are eaten by primary consumers

Food web

How food chains link together in a habitat to form a food web.

Pyramid of number

A pyramid drawn with bar lengths proportional to the numbers of organisms present

Pyramid of biomass

A pyramid drawn with bar lengths proportional to the mass of plants/animals

Pyramid of energy

A pyramid drawn with bar lengths proportional to the energy stored in organisms

Productivity

The rate of generation of biomass in an ecosystem. Usually measured in units of mass per area put unit time (gm-2y-1). Farming practices try to improve this by increasing yields by increasing the efficiency of energy transfer along the food chains which produce our food.

Intensive farming

A type of farming which uses processes

Percentage efficiecy

Can be calculated by dividing the energy available after the transfer by energy available before the transfer x 100.

Energy transfer

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

Biological control

Controlling pests by introducing predators

Selective breeding

Breeding of organisms by human selection of parents for certain characteristics

Ecosystem

Self-contained unit made up of the biotic and abiotic factors in an area

Population

A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.

Community

The organisms of all species that live in the same area

Habitat

The place where an organism normally lives

Niche

All the conditions and resources required for an organism to survive and reproduce (its ‘role’)

Random sampling

Sampling a population to eliminate bias e.g. grid square and co-ordinates

Systematic sampling

Regular sampling across an area e.g. along a straight line transect

Mark-Release-Recapture

Method of estimating population size of animals (number in first sample x number in second sample) / marked animals in second sample

Abiotic factors

Concerned with the non-living part of the environment

Biotic factors

Concerned with the living organisms in the environment

Interspecific competition

Competition between organisms of different species

Intraspecific competition

Competition between organisms of the same species

Succession

The changes in an ecosystem

Pioneer species

A species that can colonise bare rock or ground

Climax community

The stable

Conservation

Management of the Earth’s natural resources in such a way that maximum use can be made of them in the future

Ecosystem

All the living and non-living components of a particular area.

Saprobiontic microorganism

Also known as saprophyte – an organism that obtains its food from the dead or decaying remains (detritus) of other organisms.

Detritrivores

Organisms that help saprophytes do their job. They feed on pieces of dead and decaying material and finely break it up increasing its surface area.

Decomposer

Any organism which breaks down organic matter. Include saprophytes and detritivores.

Nitrogen cycle

Four main stages: ammonification

Nitrogen fixation

Conversion of nitrogen gas into nitrogen-containing compounds. Carried out by free-living nitrogen fixing bacteria and mutualistic nitrogen-fixing bacteria which live in nodules on the roots of plants such as peas and beans. It can also be carried out industrially and occurs naturally when lightning passes through the atmosphere.

Nitrogen fixing bacteria

Carry out the process of nitrogen fixation. Can be free-living or mutualistic bacteria.

Ammonification

Production of ammonia from organic nitrogen-containing compounds e.g. urea and proteins. Saprobiontic microorganisms feed on faeces and dead organisms materials

Nitrification

Carried out by free-living nitrifying bacteria. Some convert ammonia into nitrites and some convert nitrites into nitrates using oxidation reactions which release energy. Good drainage and ploughing prevents air spaces from being filled with water and allows nitrification to continue.

Denitrification

Carried out by anaerobic denitrifying bacteria which convert of soil nitrates into nitrogen gas.

Phosphorous cycle

Enables the cycling of phosphorous which is an important biological element as it is a component of ATP

Phosphate

PO43- ions are how phosphorous exists mostly in the form of sedimentary rock deposits.

Weathering

How rocks are worn away - how phosphate ions in wastes and remains e.g. guano

Mycorrhizae

Mutualistic association between certain types of fungi and the vast majority of plants. The fungi act like extensions of the plant’s root system and increase the surface area for absorption of water and minerals. The fungi receives organic compounds such as sugars and amino acids from the plant. The mycorrhiza act like a sponge and so holds water and minerals in the neighbourhood of the roots

guano

The excrement of seabirds and bats.

Symbiotic

When two species live in close proximity. Mutualistic is a type of symbiotic relationship where the relationship is mutually beneficial for two organisms.

Fertiliser

Using these replenishes mineral ions

Inorganic

Type of fertiliser which are mined from rocks and deposits and then converted into different forms and blended together to give the appropriate balance of minerals for a particular crop. Contain nitrogen

Organic

Type of fertiliser which consist of the dead and decaying remains of plants and animals as well as animal wastes such as manure

Leaching

Process by which nutrients are washed from the soil into watercourses. Rainwater will dissolve any soluble nutrients

Eutrophication

Consequence of an increase in nutrient concentrations in watercourses that leads to an algal bloom

Greenhouse gases

Gases such as methane and CO2 which trap more heat energy