Unit 3.2 Distribution of Organisms Flashcards
Abiotic factor
Any non-living component that affects an organism eg. temperature, pH
Biotic factor
Any living component that affects another organism eg. grazing, predation, disease or competition.
Adaptations
Inherited characteristics that make an organism well suited to its environment eg. thick fur, camouflage.
Can be behavioural, structural or physiological.
Distribution
Where organisms are found in a habitat. Their range or spread across the habitat.
Predation
One organism (predator) eats another (prey) to obtain food.
Grazing
Herbivores eat the plants (producers) in an ecosystem to obtain food.
Interdependence
All living organisms in an ecosystem depend on each other eg. for pollination, nutrient cycling, food and shelter.
Temperature probe
Used to measure temperature (abiotic factor).
Light meter
Used to measure light levels (abiotic factor) in an ecosystem.
Avoid leaning over and casting shadows when taking readings.
pH probe/universal indicator
Used to measure soil pH (abiotic factor). Wipe between readings and insert to the same depth to reduce errors.
Moisture probe
Used to measure soil moisture levels (abiotic factor) in an ecosystem. Wipe between readings and insert to the same depth to reduce errors.
Sampling
Used to investigate the abundance and distribution of organisms in an ecosystem.
Abundance
How many organisms of a particular species are present in an ecosystem.
Pitfall trap
Used to estimate the abundance of mobile, terrestrial invertebrates in an ecosystem.
Pitfall trap - minimising errors
Must have a cover to disguise the entrance; holes in the bottom for drainage and must be level with the soil so invertebrates fall in.
Kick sampling
Used to investigate the abundance of aquatic invertebrates in an ecosystem.
Quadrat
Sampling square used to estimate the abundance of plants or slow-moving animals in an ecosystem.
Quadrat limitations
Must be placed at random, searched to the same level of intensity and there must be adequate replication to achieve representative samples.
Transect
A tape laid along the ground.
Quadrat samples are taken at regular intervals along it, to study the effect of changing abiotic factors on the distribution of species.
Branched key
Used to identify organisms using a series of yes/no questions
Paired statement key
Used to identify organisms using a series of linked questions with 2 possible answers (paired statements).
Deforestation
Removal of trees for timber, fuel or to create space for agriculture or housing.
Reduces biodiversity.
Desertification
Creation of deserts by over use of water by humans.
Reduces biodiversity.
Overfishing
Removal of large numbers of fish by humans, reducing biodiversity and abundance of fish.
Pollution
The presence of a substance that is harmful to the environment, or is unsightly.
It can affect the air, sea, land or freshwater.
Indicator species
An organism that indicates the level of pollution by their presence or absence.
eg lichen (sulfur dioxide in air) ; freshwater invertebrates such as mayfly and stonefly larvae, bloodworms (levels of dissolved oxygen in water).
Lichen
An organism that is sensitive to sulfur dioxide, so indicates the level of air pollution.
Organic pollution
Material from living or once living organisms.
Includes, sewage, manure and dead organisms.
Biological oxygen demand
How much dissolved oxygen is removed from the water.
Bacteria feeding on sewage have a high BOD, rapidly reducing the level of oxygen in the water.
