organisation of an ecosystem

Question 1

boimass

definition

Answer 1

The dry mass of an organism.

Question 2

decompose

definition

Answer 2

If a substance decomposes, it breaks down into simpler compounds or elements.

Question 3

decomposer

definition

Answer 3

An organism which eats dead organisms, fallen leaves, animal droppings, etc, and breaks them down into simpler materials.

Question 4

ecosystem

definition

Answer 4

The living organisms in a particular area, together with the non-living components of the environment.

Question 5

endangered species

definition

Answer 5

Animals that are close to extinction because of their low numbers.

Question 6

faeces

definition

Answer 6

Waste matter from the bowels.

Question 7

food web

definition

Answer 7

A network of food chains, showing how they all link together.

Question 8

primary consumer

definition

Answer 8

The name given to an organism that eats a producer. A herbivore.

Question 9

producer

definition

Answer 9

Plants that begin food chains by making energy from carbon dioxide and water.

Question 10

quadrat

definition

Answer 10

A square frame of known area used for sampling the abundance and distribution of slow or non-moving organisms.

Question 11

secondary consumer

definition

Answer 11

An organism that obtains its energy by eating the primary consumer.

Question 12

sampling

definition

Answer 12

The selection of subjects included in a study.

Question 13

species

definition

Answer 13

A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully.

Question 14

transect

definition

Answer 14

A line created, for instance, with a tape measure, along which sampling occurs.

Question 15

trophic level

definition

Answer 15

The position of an organism in a food chain, food web or pyramid.

Question 16

zonation

definition

Answer 16

Growing of plants in distinction regions.

Question 17

Ecosystem

Answer 17

An ecosystem is the interaction between a community of living organisms and their environment. A community is two or more populations of organisms. An ecosystem is the interaction of two or more populations of organisms in their environment.

Question 18

Producers and consumers

feeding relationships

Answer 18

Feeding relationships show what organisms eat or are eaten by others and through this the levels of organisation in an ecosystem. These can be shown in food chains, which add together to make food webs for a habitat.

Question 19

Producers

Answer 19

At the base of almost every food chain is a producer. These are plants or algae, which photosynthesise. This means they convert energy from the sun into glucose during photosynthesis produces biomass. It is this which feeds the rest of the food chain.

Question 20

Levels of organisation

Answer 20

All animals above the producer are called consumers. The first is the primary consumer, the next is the secondary consumer. Animals that hunt and kill others are called predators, and those that are hunted and killed are called prey. The top animal in the feeding relationship is called the apex predator.

Question 21

Decomposers

Answer 21

Decomposers are bacteria and fungi, which break down dead organisms in a process called decomposition or rotting. They do this by releasing enzymes onto the dead matter and afterwards, consume the broken down substances. They form a vital role in the recycling of matter. When organisms die and decompose plants absorb the broken down nutrients through their roots.

Question 22

Sampling

why?

Answer 22

It is important to estimate the number of organisms in a population to better understand the relationships in a community. This information is useful for monitoring the impact of conservation projects that aim to conserve endangered species or habitats. It is almost always impossible to count all of the organisms in a population. So we look at a small section of a population to draw conclusions about the rest. This process is called sampling and the area or part of population looked at is called a sample.

Question 23

What is sampling?

Answer 23

When sampling a population, the numbers of organisms are counted within a sample site, and then the results multiplied to estimate the total number in the entire habitat. Large animals and plants can often simply be counted. However, many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.

Question 24

Sampling

pitfalls

Answer 24

Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.

Pitfall traps are small traps dug into the ground, which often has food inside to attract small mammals. The sides of these traps are smooth to stop the mammals escaping.

Question 25

Sampling

kick-sampling

Answer 25

Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.

A method is to use large nets to sweep through grasses or leaves of trees in a process called sweep netting. To catch aquatic organism nets are often held downstream of an area of river bed which is then gently disturbed by the person doing the sampling. The small animals float into the net. This is called kick-sampling.

Question 26

Sampling

pooter

Answer 26

Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.

Pooters are small devices used when sampling to suck up small insects safely without them going into your mouth.

Question 27

What are quadrats?

How are they used?

Answer 27

Quadrats are square frames of wire usually 0.25 m2. These are placed on the ground to look at the plants or slow-moving animals within them.

Question 28

When looking at plants in a quadrat the following sampling can be used:

Answer 28

• Number of individual species
• Species richness
• Percentage cover

Question 29

Using quadrats

When looking at plants in a quadrat the following sampling can be used:
Number of individual species

Answer 29

Number of an individual species: the total number of individuals of one species (eg daisies) is recorded.

Question 30

Using quadrats

When looking at plants in a quadrat the following sampling can be used:
Species richness

Answer 30

Species richness: the number of different plant or animal species is recorded but not the number of individuals within a species.

Question 31

Using quadrats

When looking at plants in a quadrat the following sampling can be used:
Percentage cover

Answer 31

Percentage cover: the percentage of the quadrat area that is covered by one species (eg grass). This is easier to estimate if a quadrat has wires making smaller sections. Percentage cover rather than number of individuals is used when estimating plant frequencies if it is difficult to identify individual plants, such as grasses or moss.

Question 32

Random sampling

Answer 32

Random sampling using a quadrat involves the placing of quadrats at random coordinates. Regardless of whether you are investigating the number of individual species, the species diversity or the percentage cover in different areas you would use random sampling.

Question 33

systematic sampling

Answer 33

Most sampling is random, but systematic sampling can be used if there is a trend or pattern across the habitat, such as distance up a beach, or altitude on a hillside. If you are using the wrong kind of sampling method for your experiment, this can lead to biased results.

Question 34

What are we sampling for?

Answer 34

Sometimes we want to see if the number of species or percentage cover changes within an area. This is often as a result of a change in an abiotic factor.

An example of this is an investigation into whether the growth of seaweed depends upon the distance it is found on the seashore from the tide. As we are looking to link a linear change (in this case the number of hours the seaweed is covered by the tide) we would use systematic sampling.

A quadrat could be placed at regular distances, for example every five metres, along an imaginary line called a transect, which would run down the shore. Systematic sampling would be used along the transect to link changes in species to abiotic factors, such as immersion by water, temperature fluctuations, light intensity, all of which are influenced by the tide.

The results from transects can be drawn into kite diagrams. The width of the bar from the middle at any distance shows how many individuals were observed at that point.

Question 35

Zonation

Answer 35

A change in the distribution of species across a habitat is called zonation. It can happen because of a change in an abiotic factor.

Question 36

Mean

Answer 36

The mean is the most common type of average we use. To calculate the mean you add all the values together and divide by the total number of values.

Question 37

Median

Answer 37

To calculate the median, a set of numbers are placed in increasing order of size. The median is the middle number in the list. The two students took an even number of readings, and they calculated the median as the mean of the two middle numbers.

Question 38

Mode

Answer 38

The mode is the value that appears the most often. In the shade, the mode is four because there are three values of four. In the sun, it is five because there are three values of five.

Question 39

The second trophic level in all food chains is a what?

Answer 39

The second trophic level in all food chains is an herbivore or omnivore called a primary consumer.

Question 40

The third trophic level is a what?

Answer 40

The third stage is a carnivore or omnivore which eats the primary consumer. This is called the secondary consumer

Question 41

The final trophic level is what?

Answer 41

The final level is perch, which is a carnivore and is often called the top or apex predator. Organisms at the tops of food chains have no predators.

Question 42

What are producers?

Answer 42

Green plants - they make glucose during photosynthesis.

Question 43

What are primary consumers?

Answer 43

Usually eat plant material - they are herbivores. For example rabbits, caterpillars, cows and sheep.

Question 44

What are secondary consumers?

Answer 44

Eat animal material - they are omnivores or carnivores. For example cats, dogs and lions.

Question 45

What are predators?

Answer 45

Kill for food. They are either secondary or tertiary consumers.

Question 46

What are prey?

Answer 46

The animals that predators feed on.

Question 47

What are decomposers?

Answer 47

Feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces.

Question 48

Biomass

Answer 48

Biomass is living or recently dead tissues. The mass of your body is biomass because you are alive. Wood is considered biomass because it was recently a plant. Fossil fuels are not considered biomass because they are the remains of organisms that died millions of years ago and have been chemically changed from the original living tissue.

Question 49

Pyramids of biomass

Answer 49

The amount of biomass can be measured at different trophic levels in a food chain. The total biomass of each trophic level is often represented as a modified bar chart called a pyramid of biomass. In a food chain from a healthy ecosystem the biomass at each trophic level must reduce.

Pyramids of biomass are always perfectly shaped. If this is not the case, then the ecosystem is likely to be unhealthy and in danger.

Question 50

Pyramids of biomass must be drawn with the:

Answer 50

• bars equally spaced around the midpoint
• bars touching
• bar for the producer at the bottom
• length of each bar is proportional to the amount of biomass available at each trophic level

Question 51

Calculating efficiency of biomass transfers

Answer 51

The efficiency of biomass transfer is a measure of the proportion of biomass transferred from a lower trophic level to a higher one. Usually around 10% of biomass is transferred between trophic levels in a healthy ecosystem and the remaining 90% is used by the organisms during life processes.

Question 52

Q. This is an example of a food chain:

phytoplankton → zooplankton → herring → sea lion

The total biomass within the phytoplankton is 14.6 kg. The total biomass within the zooplankton is 1.3 kg. What is the efficiency of this transfer?

Answer 52

To complete this calculation, divide the amount from the higher trophic level by the amount from the lower trophic level and multiply by one hundred. That is, divide the smaller number by the bigger one (and multiply by one hundred).

percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100

percentage efficiency transfer = (1.3kg/14.6) x 100 = 8.9%

Question 53

Percentage efficiency transfer equation

Answer 53

percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100

Question 54

What is used for estimating the number of plants?

Answer 54

Quadrat

Question 55

What is the name of the sampling square used in fieldwork?

Answer 55

Quadrat

Question 56

A 0.25 m^2 quadrat was placed in a 100 m^2 field. Five daisy plants were counted in the quadrat. What is the estimated number of daisies in the field?

Answer 56

(5/0.25) x 100 = 2000 daisies in the field.

Question 57

Energy for all food chains comes from what source?

Answer 57

Sun

Question 58

Producers are usually what?

Answer 58

Plants

Question 59

How is energy in food chains lost?

Answer 59

Respiration and heat

Question 60

What happens to the biomass at each stage in a food chain?

Answer 60

Decreases

Question 61

How do decomposers break materials down?

Answer 61

Using enzymes