Define species
a group of organisms that have a common ancestry and shared genes, and so are capable of breeding together to produce fertile offspring
Define community
multiple populations of different species living and interacting in the same area
Define ecosystem
a complex, self-perpetuating assemblage of organisms, interacting in their biotic and abiotic environment
Give 5 biotic factors
- predation
- competition
- parasitism
- disease
- mimicry
Give eight abiotic factors
- water availability
- light intensity
- temperature
- humidity
- atmospheric composition
- pH
- salinity
- soil composition
What is biomass
the mass of living material of the organism or tissue, and the chemical energy that is stored within the organism
Give two ways that biomass can be measured in terms of
1) dry mass of an organism
2) mass of carbon an organism contains
- the mass of carbon that an organism contains is 50% of the dry mass of the sample
What is the dry mass of an organism
an organisms mass after all water has been removed
What is the role of producers
to convert light energy to chemical energy in biological molecules
Why is only a small percentage of biomass conserved across trophic levels
- not all the plant’s biomass is eaten by the primary consumer
- not all the consumer’s biomass intake is digested
- lots of chemical energy for movement and heat rather than as biomass
What is the equation for efficiency of biomass transfer
biomass transferred / biomass intake x 100
What is the role of saprobionts
- to decompose waste and dead matter via extracellular digestion, making inorganic ions available to other organisms
- carry out process of ammonification
How is plant protein converted into animal protein
- plant is consumed and digested by protease into amino acids
- protein synthesis occurs to form animal protein
How is animal protein converted to ammonium compounds in humus
- death and decomposition of animals
- ammonification takes place by saprobionts
Which bacteria converts ammonium compounds into nitrites
nitrosomonas
Which bacteria convert nitrites into nitrates
nitrobacter
How are nitrates converted into plant protein
uptake by active transport
How are nitrates converted into nitrogen gas
denitrification by denitrifying bacteria ( uses nitrates in respiration and releases nitrogen gas )
How is nitrogen gas converted into ammonium compounds
through nitrogen fixation by two bacteria
1. rhizobium in root nodules
2. azotobacter free-living in soil
Define succession
directional change in vegetation over time from no biological material to climax vegetation
Give the three types of starting seres in succession
- water - hydrosere
- rock - lithosere
- sand - xerosere
What is primary succession
primary succession occurs when newly formed / exposed land is gradually inhabited by an increasing number of species
Describe how succession occurs - lithosere
- seeds and spore that are carried by the wind land on exposed rock and begin to grow - pioneer species
- as pioneer species die and decompose, dead organic matter forms a basic soil
- small plants and grasses begin to grow and die and decompose - new soil becomes deeper and more nutrient-rich
- roots of plants forms network that prevents soil from being washed away
- larger plants and shrubs requiring deeper and nutrient rich soil can now grow - require more water stored in deeper soils
- dominant species e.g. trees can grow
- final community formed is known as climax community - very high diversity of species compared to with pioneer species
Describe how succession occurs - hydrosere
- pioneer species is algae - these photosynthesise, die and release nutrients into the water
- free floating plants being to grow e.g. duckweed - die and form sediment
- rooting aquatic plants being to grow e.g. pondweed - die and form deeper sediment
- reeds grow which dries out all remaining water
- grasses and small shrubs begin to grow and die - forming soil
- eventually climax woodland is formed
