Ecological Relationships

Question 1

Name the five abiotic factors

Answer 1

• Wind speed
• Water content of soils
• The pH of soils
• Light intensity
• Temperature

Question 2

Biodiversity

Answer 2

The number of different species living in a given habitat or area

Question 3

Population

Answer 3

The number of organisms of a single species living in one area

Question 3

Habitat

Answer 3

Where an organisms lives

Question 3

Environment

Answer 3

These are the surroundings in which an organism lives in and has both living and non living components

Question 4

Community

Answer 4

This includes all the living things in a specific habitat

Question 5

Ecosystem

Answer 5

A term that is used to describe the interactions of the living and non-living parts of the ecosystem

Question 6

Explain how light is used by plants

Answer 6

Light is used by plants during photosynthesis to convert into chemical energy needed for growth. It is absorbed by chlorophyll in the leaves

Question 7

How can wind speed be recorded ?

Answer 7

Wind speed can be recorded using an anemometer

Question 8

How does wind affect communities : (2)

Answer 8

• This factor can influence the types of species present for example in sand dunes and also in mountain ranges.
• The values of wind speed can indicate how exposed a certain habitat is.

Question 9

How does water affect communities ; (2)

Answer 9

• Plants need a ready supply of water to survive.

- For this reason sandy soils that don’t retain much water tend only to support a small number of highly adapted plants.

Question 10

How is the percentage water content measured ? (2)

Answer 10

• Soil samples can be collected and returned to the lab.
• Weighing the soil and then drying out (in an oven or a microwave) until the mass stays constant allows the percentage water content to be estimated.

Question 11

How does pH affect communities : (2)

Answer 11

The pH of soils can affect what types of plants grow there

- Some plants prefer acidic soils, whilst others have a preference for alkaline conditions

Question 12

How is the pH of soil determined : (1)

Answer 12

The pH of a soil can be tested chemically using a soil sample and universal indicator or simply by inserting a pH probe into the ground.

Question 13

How does light intensity affect communities

Answer 13

• Light intensity can greatly affect the distribution of plants.
• If plants are shaded by taller trees they will probably have adaptations to allow them to absorb a greater amount of the available light

Question 14

How is light intensity measured

Answer 14

Light intensity is easily measured using a light meter.

Question 15

How is temperature recorded

Answer 15

It is readily measured using a soil thermometer.

Question 16

Describe how to use Quadrats to investigate changes in the distribution and population of organisms within a sample area of a habitat (3)

Answer 16

• A quadrat is a simple frame that can be placed on the ground in order to sample a specific area of ground cover.
• The number of quadrat sampling points used is dependent on the overall size of the area being sampled.
• More commonly 20 sampling points may be selected, the data collated in a spreadsheet or table and an average value for the percentage cover of each species given.

Question 18

How do you ensure that data is reliable ?

Answer 18

Through taking results from many different sampling points (i.e. using a large number of individual samples) and then calculating an average value.

Question 20

What is a belt transect ? (3)

Answer 20

• A belt transect is a technique used when there is gradual change from one habitat to another.
• Quadrats are placed along a line end on end allowing a strip of the ground and the species growing on it to be sampled.
• As the transect progresses from one end to another the numbers of certain species will decrease whilst others will increase

Question 21

Define competition in terms of ecology

Answer 21

Competition in ecosystems refers to the need for organisms to obtain resources from the habitat in which they live.

Question 22

Name two things from plants and animals that they would compete over

Answer 22

PLANTS:
water
light

ANIMALS:
food
territory

Question 23

What is the role of green plants in the ecosystem?

Answer 23

• Plants obtain their energy from the sun during the process of photosynthesis- converting light energy from the sun into chemical energy in the form of molecules like starch.
• Plants are known as producers as they make their own food and make energy available to the rest of the organisms in the food chain.

Question 24

Which organism is always at the first trophic level ?

Answer 24

Plants, as producers, are always at the first trophic level.

Question 25

Where are animals on the trophic levels ?

Answer 25

Animals will be found at the higher trophic levels - the primary consumer at the 2nd trophic level, secondary consumers at the 3rd trophic level and tertiary consumers at the 4th trophic level.

Question 26

What do arrows represent on a food chain?

Answer 26

These represent the flow of energy and the consumption and transfer of substances (carbon and nitrogen) through the ecosystem

Question 27

Why is plants absorbing light for photosynthesis an inefficient process?

Answer 27

This process is very inefficient as only a small amount of light energy actually hitting the plants gets absorbed by chlorophyll (most is reflected or passes through the leaf

Question 28

Name the ways energy is lost: (4)

Answer 28

• Not all of the available material is eaten: the roots of plants are inaccessible and bones and fur are often not consumed by carnivores
• Much of the food is not digested - e.g. humans cannot digest cellulose and so it is egested as faeces
• The process of excretion also results in energy losses
• All organisms respire and lose energy as heat

Question 29

Why are shorter food chains more efficient?

Answer 29

Due to the energy losses at each trophic level, the longer a food chain becomes the less energy there is available. For this reason, shorter food chains are more efficient.

Question 30

Describe the difference between a pyramid of numbers and pyramids of biomass

Answer 30

• Pyramids of number display the number of each consumer from lowest to highest, producer to tertiary
• Pyramids of biomass show the mass of living tissue found at each tropic Level

Question 31

Name the disadvantage of pyramids of number (2)

Answer 31

• Pyramids of number can be misleading as they do not always take into account the size of the organisms involved
• Therefore this means a pyramid of numbers is not an accurate representation of the relationships in the community

Question 32

Give the advantage of a pyramid of biomass

Answer 32

• it is often more accurate to represent the biomass in a pyramid when looking at energy flow through a food chain

Question 33

Describe the decomposing action of saprophytic fungi and bacteria

Answer 33

• The bacteria and fungi digest materials by secreting enzymes from their cells onto the decayed material.
• These enzymes break the molecules down into a more soluble form that the bacteria and fungi then absorb.
• When this mode of digestion is used to complete the breakdown of dead material it is known as saprophytic nutrition
• Humus is the organic content of the soil formed from decomposing plant and animal material

Question 34

What are bacteria and fungi referred to as?

Answer 34

bacteria and fungi are sometimes referred to as saprophytes

Question 35

What is the digestion of materials via secreting enzymes onto decaying material, and absorption of these molecules referred to as?

Answer 35

This mode of digestion is sometimes referred to as extracellular digestion

Question 36

What is a major product of the decay and decomposition process called?

Answer 36

Humus - this material forms a large amount of the soil in which plants grow.

Question 37

What are the conditions required for effective decay? (4)

Answer 37

• Warm temperature
• moisture
• a large surface area.
  — Aerobic