Unit 3.2 Distribution of Organisms

Question 1

Abiotic factor

Answer 1

Any non-living component that affects an organism eg. temperature, pH

Question 2

Biotic factor

Answer 2

Any living component that affects another organism eg. grazing, predation, disease or competition.

Question 3

Adaptations

Answer 3

Inherited characteristics that make an organism well suited to its environment eg. thick fur, camouflage.

Can be behavioural, structural or physiological.

Question 4

Distribution

Answer 4

Where organisms are found in a habitat. Their range or spread across the habitat.

Question 5

Predation

Answer 5

One organism (predator) eats another (prey) to obtain food.

Question 6

Grazing

Answer 6

Herbivores eat the plants (producers) in an ecosystem to obtain food.

Question 7

Interdependence

Answer 7

All living organisms in an ecosystem depend on each other eg. for pollination, nutrient cycling, food and shelter.

Question 8

Temperature probe

Answer 8

Used to measure temperature (abiotic factor).

Question 9

Light meter

Answer 9

Used to measure light levels (abiotic factor) in an ecosystem.
Avoid leaning over and casting shadows when taking readings.

Question 10

pH probe/universal indicator

Answer 10

Used to measure soil pH (abiotic factor). Wipe between readings and insert to the same depth to reduce errors.

Question 11

Moisture probe

Answer 11

Used to measure soil moisture levels (abiotic factor) in an ecosystem. Wipe between readings and insert to the same depth to reduce errors.

Question 12

Sampling

Answer 12

Used to investigate the abundance and distribution of organisms in an ecosystem.

Question 13

Abundance

Answer 13

How many organisms of a particular species are present in an ecosystem.

Question 14

Pitfall trap

Answer 14

Used to estimate the abundance of mobile, terrestrial invertebrates in an ecosystem.

Question 15

Pitfall trap - minimising errors

Answer 15

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.

Question 16

Kick sampling

Answer 16

Used to investigate the abundance of aquatic invertebrates in an ecosystem.

Question 17

Quadrat

Answer 17

Sampling square used to estimate the abundance of plants or slow-moving animals in an ecosystem.

Question 18

Quadrat limitations

Answer 18

Must be placed at random, searched to the same level of intensity and there must be adequate replication to achieve representative samples.

Question 19

Transect

Answer 19

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.

Question 20

Branched key

Answer 20

Used to identify organisms using a series of yes/no questions

Question 21

Paired statement key

Answer 21

Used to identify organisms using a series of linked questions with 2 possible answers (paired statements).

Question 22

Deforestation

Answer 22

Removal of trees for timber, fuel or to create space for agriculture or housing.

Reduces biodiversity.

Question 23

Desertification

Answer 23

Creation of deserts by over use of water by humans.

Reduces biodiversity.

Question 24

Overfishing

Answer 24

Removal of large numbers of fish by humans, reducing biodiversity and abundance of fish.

Question 25

Pollution

Answer 25

The presence of a substance that is harmful to the environment, or is unsightly.

It can affect the air, sea, land or freshwater.

Question 26

Indicator species

Answer 26

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).

Question 27

Lichen

Answer 27

An organism that is sensitive to sulfur dioxide, so indicates the level of air pollution.

Question 28

Organic pollution

Answer 28

Material from living or once living organisms.

Includes, sewage, manure and dead organisms.

Question 29

Biological oxygen demand

Answer 29

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.