Organisms in the Environment & Feeding Relationships Flashcards
Define biotic factors
The biological (living) factors that influence the number and distribution of organisms in an ecosystem
Define abiotic factors
The chemical and physical (non-living) factors that influence the number and distribution of organisms in an ecosystem
Define ecosystem
A distinct and self supporting system that relies on interactions with each other and the physical environment around
Define decomposers
Organisms that break down dead organic matter (detritus) into soluble substances (e.g. sugars)
Define population
All organisms of a particular type of species found in an ecosystem at a certain time
Define community
The population of all species together in an ecosystem at a certain time
Define biodiversity
The amount of variation shown by species in an ecosystem
Biodiversity is the combination of which 2 measurements?
- The number of different species present (species richness)
- The relative abundance of each species (‘evenness’ of numbers)
Define biome
Large areas of the Earth which are dominated by a specific type of vegetation (plants and tress collectively)
What is the start of all food chains?
The sun
Give 4 examples of biotic factors that might affect a species’ abundance and distribution
- Disease
- Presence of certain species
- Organic pollution
- Availability of space for habitat
Give 4 abiotic factors that might affect a species’ abundance and distribution
- Light intensity, temperature, water availability
- Hours of daylight
- Soil conditions (nitrate level, pH, water content)
- Inorganic pollution
Why is random sampling used? (2)
- To avoid bias
- To compare the abundance of an organism in two sites
Why is systematic sampling (belt or line transect) used?
In order to look at the distribution of an organism
Describe an experiment to compare the population of two plants in two different habitats (8)
- Select two different areas of study
- Generate 10 sets of coordinates using random numbers (1-10)
- Lay out two 10m tape measures at right angles to form two sides of a square on the first area
- Use the coordinates and lay the quadrat
- Count the number of plants of each species in the quadrat
- Repeat for the other 9 sets of coordinates
- Repeat the process in the second area
- Use the data to estimate the total population size of each species on the two different lawns
Define trophic levels
It describes the position of the organism in a food chain
What does a food web show?
The interactions between multiple food chains
Why is only about 10% of energy transferred from trophic level to the next? (5)
- Lost through respiration
- Some parts are not eaten
- Lost through heat from metabolic processes
- Used for movement and growth
- Not absorbed and egested with faeces
Define biomass
The measure of total mass of living material in each trophic level
What are pyramids of number? (2)
- Represents the number of organisms in each trophic level of a food chain
- Irrespective of mass
What are pyramids of biomass?
- Represents the total mass of organisms of each trophic level
- Irrespective of their numbers
What are pyramids of energy?
- Measured in kJ per m2 per year
- Represents the energy a group of organisms in a trophic level adds to their biomass per year
