This experiment was made to investigate the animals that live in the ecosystem of a pond. Mainly looking at the distribution and abundance of the animals and the possible explanations behind. Although many animals were studied we focused on three animals that would give a good idea of the distribution and the reasons for their distribution as one was taken from each of the three trophic levels of the pond.
The Water hoglouse was chosen as it is a detritivore, which means it, only feeds on dead matter such as plant and animal remains. By studying this creature it will give us some idea of the distribution of most detritivores in a pond ecosystem. (D)
The Mayfly Nymph is a herbivore, and a primary consumer. It is different although on the same kind of trophic level as the detritivores. This animals will give us an idea of the behaviour of herbivores in the pond. (C1)
The Damselfly nymph is a carnivore and is a secondary consumer. This should give us an idea of the abundance and distribution of secondary consumers in the pond. (C2)
Two predictions were made one about the distribution of the animals in the pond and one about the abundance of the animals according to their trophic level. Basically the whereabouts of the animals and how many we thought there would be compared to the others.
Water Hoglouse – I predict most of these will be found at the bottom of the pond because they feed on dead matter, which would sink to the bottom of the pond
Mayfly Nymph – I predict that most of these will be found in the middle of the pond depth but at the top and bottom as well. Most will be found in the middle because they are herbivores and most of the plant life in the pond would be around the middle.
Damselfly Nymph – I predict that most of these will be found at the top level of the pond but also all around because they are carnivores and feed on other animals wherever they are. They will be on the top level more thought because that is where much of their prey would be found like pond surface creatures.
I predict that there will be less secondary consumers (damselfly nymphs) that primary consumers (Mayfly nymphs and hoglouses). In any ecosystem there are less secondary consumers that primary because of the energy flow in the ecosystem. As the primary consumers eat from the producers they use up some of the energy that they eat by moving and keeping warm etc. As this energy is used it cannot be passed on to the secondary consumers so therefore there cannot be as many because there is only enough energy for the C2s because there are more C1s to pass on the energy.
I predict that the total biomass of the primary consumers and the secondary consumers will be about the same. I think this because from the sheet we were given generally the secondary consumers are bigger and have a larger biomass than the primary consumers. But as I explained above there will be more primary consumers that secondary so it will work out that they will have the same total biomass.
1.3 small buckets to collect samples from each of the three areas of the pond; bottom middle and top layers.
2.A tray to put the samples in from the net before they are put into the buckets.
3.A net to collect the samples from the pond.
1. We gathered the apparatus needed for the experiment.
2. We took the tray and put some water in it so that when we collected animals from the pond they could survive.
3. We took three sweeps from the top layer of the pond and added each sample to the tray an then added it to the bucket assigned for the top layer samples.
4. We repeated the same thing with the middle and bottom layers of the pond.
We took our sample buckets back to the field centre and poured some out into the tray again.
5. With a plastic spoon we scooped out animals into smaller tubs to identify them and count them. We recorded the results in a table.
6. We did the same again until we had counted everything in the bucket. We then did the same with the other two buckets.
7. We put the whole classes results into a big table to give a better view of the whole pond.
8. From the results we made graphs of distribution and pyramids of the abundance of the animals in the pond.
9. We made a pyramid of the number of animals in the pond and another using the figures of the total biomass of the animals from each group in the pond. (C1 + D and C2s). We were given a sheet with the dry mass of the insects we found so using the total numbers we totalled the mass of the animals by multiplying each total number of the animal by its mass and adding all the primary consumers masses together and the secondary consumers masses together, so we could make a two part biomass pyramid.
We can deduce various things from the graphs plotted and the pyramids of abundance and the pyramid of biomass. From the bar graph we saw the distributions of the animals. This is explained in the analysis section. The graph included total numbers of animals along with the totals from each area of the pond. The distribution shown by the graph is due to the animal’s way of survival. Which trophic level they belong to (primary of secondary consumers) and therefore what they eat (plants, dead matter, other animals).
From the first pyramid, the pyramid of numbers it shows the totals of all the primary consumers (on the bottom due to them being lower down the food chain) and the secondary consumers (on the top). The graph shows that there were more primary consumers than secondary consumers as the bottom level is bigger than the top. This pyramid was made from the class results we merged. The totals of every primary and secondary consumer were added up into two groups. These results are similar to what we predicted. This does not show very realistic results as I am sure that there should have been far more primary consumers compared to the secondary to give the amount of biomass needed to supply the secondary consumers with enough energy.
The second pyramid is the pyramid of biomass. This was made from the totals of each of the animals in the pond, multiplied by the dry mass of that animal to show the exact mass of that animal we found as a class in the pond. Then we added the total masses of all the primary consumers and the total mass of all the secondary consumers to give the results. The pyramid shows there being a huge amount larger mass of secondary consumers. Unfortunately this cannot be a reliable, let aloine accurate biomass pyramid. Taking into account the energy flow in the pond the results cannot be right. The mass of primary consumers should be about the same if not quite a lot more than the mass of all the secondary consumers. This is because the primary consumers get the energy they need from the producers. They eat all of the food and process it into energy. However not all of the energy they have taken in can be passed onto the next trophic level because in the time between them eating and them being eaten they have used up a lot of the energy by moving.
When the creature is eaten only a small amount of the energy it has taken in is passed onto the secondary consumer. This means that there would have to be a lot more primary consumers than secondary consumers to supply the secondary consumers with enough energy. Secondary consumers are a lot bigger than primary consumers so for the biomass of primary consumers to be bigger than that of secondary consumers there would have to be a lot more of them for there to be a large enough biomass of primary consumers to support the secondary consumers. So the results taken were wrong, they were not counted well enough and not enough small animals were counted. The energy flow in an ecosystem means that there are always fewer in each trophic level as it goes up because each level loses energy by moving and living so there have to be more to pass on enough energy, the amount that would be passed on if none were lost. So the trophic level below in this case the primary consumers have to have a larger biomass to provide energy for the higher trophic level, the secondary consumers.
The graphs I predicted were similar to what was produced apart from the pyramid of biomass. The pyramid of numbers was almost right, just not in large enough proportions as it should have been. The bar graph was just a representation of results and some it supported my prediction. The pyramid of biomass was very different to what I had predicted. I think that most of the results taken were not wrong but just that we looked over a lot of potential results. Problems arose in the bottom layer as it was too murky and a lot of smaller primary consumers were looked over and not counted which produced such a small biomass of primary consumers.
The water hoglouse appeared most in the middle area of the pond which was surprising as it is a detritivore and I predicted it to live mostly at the bottom of the pond, as it feeds on dead plant and animal matter which would sink to the bottom. Not that many were found overall. This is shown in the bar graph plotted. Possibly the hoglouses were disguised in the mud in the samples from the bottom of the pond.
Damselfly nymphs appeared mostly in the middle but with more at the top than at the bottom this agrees with my prediction a bit as more appeared at the top than the bottom and I said they could be anywhere to catch their prey. 123 of these were found which compared to the 16 hoglouses is slightly unbelievable proportions, maybe it wasn’t hoglouse season.
The mayfly nymphs distribution agreed with my prediction with there being the most in the middle of the pond where most of the plant life grows, as it is a herbivore. About 58 of these were found. This was the only one that matched our predictions completely.
The results of the graph generally didn’t agree with my predictions. I predicted that most hoglice would be found at the bottom of the pond because they feed on dead matter, which would sink to the bottom, but more were found in the middle area. I also predicted that most damselfly nymphs would be found at the top because they feed on other animals and there would be lots of easy prey on the surface. The results agreed to an extent with my prediction in the fact that there were more at the top than in the bottom, but most were in the middle. I predicted that most mayfly nymphs would be found in the middle because they are herbivores and there would be plants in the middle. My prediction matched the results.
I predicted there to be more primary consumers than secondary consumers. The results agreed but not that much I expected there to be much more of a difference between the totals. I predicted that the biomasses of the secondary and primary consumers would be about equal. My results did not confirm this. The pyramid I drew showed a huge mass of secondary consumers compared to the biomass of the primary consumers. Often my prediction didn’t match the results I think because they weren’t counted well enough.