What is an abiotic factor?
Non-living components of an ecosystem that affect living organisms.
What is a biotic factor?
An environmental factor associated with living organisms in an ecosystem that affect each other, e.g. predatation
What is an ecosystem?
A community of animals, plants and bacteria interrelated with the physical and chemical environment.
What are producers?
Plants (and some other photosynthetic bacteria) which supply chemical energy to all other organisms
What are consumers?
Primary consumers are herbivores which feed on plants. Primary consumers are eaten by carnivorous secondary consumers. Secondary consumers are eaten by carnivorous tertiary consumers.
What are decomposers?
Decomposers (bacteria, fungi and some animals) feed off waste material or dead organisms.
What is a habitat?
The place where an organism lives
What is a population?
All of the organisms of one species, who live in the same place at the same time, and who can breed together.
What is a community?
All the populations of different species, who live in the same place at the same time, and who can interact with each other.
What is a niche?
The role of an organism within its habitat.
What are the 3 types of change in ecosystems that affect population size?
- Cyclic changes: changes repeat themselves in a rhythm, e.g. movement of tides, changes in day length and the way in which predator and prey species fluctuate.
- Directional changes: changes in one direction that tend to last longer than the lifetime of organisms in the ecosystem, e.g. erosion of a coastline or deposition of silt in an estuary.
- Unpredictable/ erratic changes: no rhythm and no constant direction, e.g. effect of lightening or a hurricane.
What is meant by biomass transfer?
Transfer of biomass from one trophic level to the next.
How do you calculate ecological efficiency?
(biomass at higher trophic level / biomass at lower trophic level) x 100
How do ecologists measure dry mass of an organism to draw a pyramid of biomass?
Collects the organisms, puts them in an oven at 80°C and periodically checks their mass. Once the mass stops reducing all the water has been evaporated.
How is energy lost at each trophic level?
- Energy is used in metabolic reactions, e.g. respiration
- Some parts of animals cannot be digested by consumers, e.g. bones
- Lost in dead organisms, which are then only available to decomposers
- Plants don’t use all available light energy (e.g. sunlight reflected)
- Excretion
What happens to light from the sun that is not transferred into plant biomass?
- Reflected off the leaf
- Evaporates water from the leaf
- Energy losses from chemical reactions
What is Gross Primary Productivity (GPP)?
The rate at which plants convert light energy into chemical energy through photosynthesis. (Units could be g m^-2 yr^-1 or K calm^-2 yr^-1
How do ecologists measure dry mass of an organism to draw a pyramid of biomass?
Collects the organisms, kill organisms, put them in an oven at 80°C and periodically checks their mass. Once the mass stops reducing all the water has been evaporated.
How do you calculate Net Primary Productivity?
NPP = GPP- plant respiration
How can primary productivity be increased?
- Grown under light banks so light is not a limiting factor
- Drought-resistant crops
- Greenhouses provide warmer temperatures
- Crop rotation (growing a different crop in each field on a rotation cycle) stops reduction in soil level of nutrients such as nitrate
- Spraying with pesticides to kill insects
- Spraying with herbicides to kill weeds
- Spraying with fungicides to prevent fungal infections
- Crops are planted early to provide a longer growing season to harvest more light and avoid impact of temperature
- Irrigation
What is Net Primary Productivity (NPP)?
The energy from the sun that enters the food chain.
How can secondary productivity be increased?
- Harvest animals just before adulthood as young animals use more energy to grow
- Selective breeding
- Animals treated with antibiotics to prevent loss of energy to parasites
- Zero grazing for pig & cattle farming stops them moving
What is the name given to bacteria and fungi involved in decomposition and how do they feed?
Saprotrophs because they feed saprotrophically:
1. Saprotrophs secrete enzymes onto dead and waste material
2. Enzymes digest the material into small molecules which are then absorbed into saprotrophs body
3. The absorbed molecules are stored or respired to release energy.
What is nitrogen fixation?
Nitrogen gas in the atmosphere is converted to ammonia by bacteria such as Rhizobium and Azotobacter by anaerobic respiration.
