Embedded Files
Population Dynamics
Population Dynamics
Inquiry question: What effect can one species have on other species in a community?
Activity 5 - Abiotic factors
Activity 5 - Abiotic factors
image of abiotic factors worksheet
On an excursion, students use a range of equipment to measure abiotic factors. They learn how to use each item of equipment to achieve validity and accuracy. They take five measurements of each factor to improve reliability.
Abiotic factors slide showVideo Transcripts
View the slide show to learn about the different abiotic factors we measure on the rock platform.
On 3 September 2021 we took measurements of abiotic factors on the rock platform at Shelly Beach, Cronulla. Measurements were taken at three locations - near low tide, at mid tide and near high tide. Five measurements of each factor were taken at each site.
Download the spreadsheet to record abiotic factors. You will be asked to make a copy. Make a copy so you can edit it in your own Google Drive.
Go through the Abiotic factors on the rock platform 360 tour below:
click on each icon in the tour to view information about an abiotic factor
then click through the images to see measurements 1-5
record the measurements in your spreadsheet
repeat for all icons
click to visit the mid platform and high platform and repeat
if your spreadsheet is complete then you have found all the measurements
continue with the activities to process your data
Abiotic factors on the rock platform
Compare the data collected on 3 September 2021 to data collected over time.
Download the spreadsheet of abiotics data. This data was collected and entered by year 11 Biology students over various excursions to the rock platform.
The students were new to measuring and recording fieldwork data and may have made errors. You may choose to exclude (ignore) data that is an outlier (e.g., so different from the other measured values that is most likely a mistake). Justify your decision to exclude data.
Process the data, for example, find averages of each factor and graph some factors over different dates.
Create your own Word or Google Doc to process and analyse abiotic factors data:
Qualitatively describe the abiotic factors at Shelly Beach, Cronulla.
Compare the data from more than one date and account for any variation in the data. Compare to the measurements from 3 September 2021.
Refer to Bureau of Meteorology data for 3 September 2021 (measurements taken at Sydney Airport). Compare to rock platform measurements from the same date and account for any variation.
Ocean water is saline with approximately 35 ppt. Compare this to measurements for water salinity in the rock pool from the spreadsheet and/or from 3 September 2021 and account for any variation.
Describe at least three ways to ensure the accuracy of abiotic data.
Describe at least three ways to ensure the validity of abiotic data.
Activity 6 - Niches
Activity 6 - Niches
Read some information about ecological niches. Write a definition of ecological niche in your own words.
Pre excursion niches activity.pptxEcological Niches PowerPoint
Download the Ecological Niches PowerPoint template or create your own presentation:
Choose one animal and one plant from the rock platform guide and complete the two slides on niches. Describe at least five roles each organism addresses in the rock platform ecosystem.
Example
Activity 7 - Measuring populations of organisms using sampling techniques
Activity 7 - Measuring populations of organisms using sampling techniques
1m quadrat on the rock platform
Quadrat sampling is used to estimate population size (the number of species in an ecosystem). Imagine counting every single black periwinkle on the rock platform... impossible, right? Instead, scientists take random samples and count the number of a species in a square (quadrat). Scientists love 1m x 1m quadrats, as the area of a
1m x 1m square = 1m2.
This makes it easier to calculate population density (see Activity 9). We use 1m x 1m quadrats on the rock platform. Would they work in a rainforest? Would they be suitable if you needed to count very small insects? How do you think having more quadrat samples will affect the validity and reliability of the data?
Read more about quadrat sampling in your textbook and on the Census of Marine Life website.
Quadrat placementYouTube | Royal National Park Environmental Education Centre (1:27min) | Transcript
Random quadrat instructions 2021.pdfRandom Quadrats instructions
It is important to place quadrats randomly to avoid bias. Watch the video and view the Random Quadrats instructions to learn how we use the Random Number Generator app on our iPads and a compass to eliminate bias.
5 x quadrats on the rock platform
Two of our teachers used the random method described above to place five random quadrats. View their locations in the photo and on the map.
Map of 5 x quadrat locations
Quadrat data.docxQuadrat data worksheet
Percentage cover rock platform.pdfPercentage Cover Guide
Use the quadrat photos to complete quadrat sampling for Black Periwinkles and Neptune's Necklace:
Download the Worksheet for quadrat data to record your results.
Download images of the five quadrats (using the buttons below).
Enlarge the images on your monitor to accurately count the number of Black Periwinkles. You may like to draw grid lines over the images and work on one section at a time.
Estimate the percentage cover of Neptune's Necklace using the Percentage Cover Guide.
Activity 8 - Estimating ecosystem area
Activity 8 - Estimating ecosystem area
Estimate the area of the rock platform at Shelly Beach, Cronulla.
The screen shots show how rock platforms appear on a satellite image:
Rock platform, Shelly Beach, Cronulla
Rock platform, Shelley Beach, Jibbon
Activity 9 - Estimating population size
Activity 9 - Estimating population size
Download the Google Sheet to view population data collected from quadrat studies on the rock platform. Choose some or all of the data to analyse. Justify your choice.
Calculate population density using quadrat data:
Population Density = total number / sample area
For example, if the data you've chosen shows a total of 300 black periwinkles in 50 quadrats, then
Density = 300 / 50 m2 = 6 black periwinkles / m2 .
Estimate total population of species on the rock platform. Use the density calculated above and the ecosystem area estimated in Activity 8.
Estimate Total Population = density x area of ecosystem
For example, if the population density of black periwinkles is 6 / m2 , and the area of the ecosystem is 1000 m2 , then
6 / m2 x 1000 m2 = 6000 black periwinkles on the rock platform at Shelly Beach.
Show all your working out in a Word or Google Doc, or by hand. Record your answer below.
Activity 10 - Distribution
Activity 10 - Distribution
Photo of transect setup
Map of transect location
A transect shows the distribution of organisms in a community. It records where species live across an environment.
On the rock platform, we set up a 30m measuring tape. We start with 0m at the water's edge and walk uphill, away from the water for 30m.
See the photo and map for the transect our teachers set up on the rock platform at Shelly Beach, Cronulla.
Read more about transect sampling in your textbook.
Walking along the transectYouTube | Royal National Park Environmental Education Centre (1:48min)
View the video as we walk from 0m to 30m along the transect. What differences do you observe? Try to write a hypothesis about where organisms live along the rock platform.
Photo along the transect
At every two meter mark, we placed a 30cm ruler on either side of the transect. To complete the transect record the distribution of up to six species (refer to the Rock Platforms page to identify species):
Neptune's Necklace
Limpet
Mulberry Whelk
Honeycomb Barnacle
Black Periwinkle
Blue Periwinkle
You need to decide which parts of the transect to count. There is no correct way, but it is important you do it the same way for every photo. For example:
mark species along the top edge of both rulers
mark species along the bottom edge of the left-hand ruler
Sample Transect
Transect.docxTransect Worksheet
Record distribution for up to 6 species.
Download the transect worksheet. Print the worksheet (or complete digitally if you prefer).
Go through the transect photos for each 2m mark (view Full Screen to see more detail). If a species appears along the ruler, then record it along the transect line using the symbols. Use the sample transect as a guide.
Transect photos
Abiotic and biotic factors affect species location. Analyse the distribution (transect) you completed.
Create your own Word or Google Doc:
Describe trends, patterns and relationships in the distribution data of plant and animal species. Consider factors such as location, zone, size and abundance.
Activity 11 - Impact of biotic factors
Activity 11 - Impact of biotic factors
Surf barnacle and algae growing on the back of a limpet
Interrelationships are everywhere on the rock platform. We're going to look at examples of the following types of relationships on the rock platform:
Predation
Competition
Symbiosis: Mutualism
Symbiosis: Commensalism
Symbiosis: Amensalism
Before we look at examples of each of these relationships, make sure you understand them. Use your textbook to learn about each of these relationships.
Predation - one organism obtains nutrition from another
Mulberry whelks prey on sea snails and barnacles. They drill holes in the shells of their prey with their rough radula (tongue-like appendage with tiny teeth). This process may be helped by acid secretions that burn a hole in the shell (shells are made of calcium carbonate which dissolves in acid). Then they chop up the soft mollusc body with their radula and suck it up through the hole to eat. They are also known as oyster borers - they are a huge problem if they prey on an oyster farm as they can ruin (eat) an entire crop!
Look at the photos to view some examples of Mulberry whelks on the rock platform.
Competition - rivalry between organisms or species for the same limited resource
Species compete with themselves and each other for space on the rock platform. Neptune's Necklace also competes for sunlight in order to photosynthesise. View some examples of competition within and between species in the photos.
Symbiosis: Mutualism - a loose association between two organisms, from which both gain benefit
Lichen often grows on the rocks above the rock platform.
Lichen is a composite organism made of an algae and a fungus, both the algae and fungus benefit from growing together. Fungus benefits from the algae’s photosynthesis; the fungus shelters and traps moisture for the algae.
Symbiosis: Commensalism - A close association between two organisms where one benefits and the other is neither harmed nor helped
Commensalism is a very common relationship on the rock platform. As organisms compete for space many 'piggy back' on other species. View the photos for specific examples of commensalism.
Upturned snails
Symbiosis: Amensalism - One species is inhibited or destroyed while another species remains unaffected
When we explore the rock platform we try hard not to impact the plants and animals. However, as the rocky shore is teeming with life it's impossible not to displace some organisms.
Trampling by humans (fisherman, surfers, students) can damage or kill periwinkles and other species. There is no nutritional gain to humans, but the snails are negatively affected.
Can you find some upturned snails in the photo?
Activity 12 - Feeding interdependencies
Activity 12 - Feeding interdependencies
Cunjevoi open under water to filter feed
There are different types of feeders on the rock platform. For example, the cunjevoi (sea squirts) in the photo are filter feeders. They may look like a plant due to the algae growing on them (commensalism!) but they are actually an animal. They are fixed to one spot, just like oysters, barnacles and other filter feeders. When they are covered by the high tide, they open and siphon water in, filtering out and feeding on plankton.
Types of feeders on the rocky shore include:
filter feeders
grazing snails
herbivores
detrivores
carnivores
Study the photos to view some examples of feeding interdependencies at Shelly Beach, Cronulla.
Read more about feeders on the rocky shore at the following sites:
Food chains summarise energy transfer through an ecosystem. All food chains begin with a producer (plant), followed by a first order consumer (herbivore or omnivore), then a second order consumer (carnivore). An arrow shows the direction of energy transfer.
A food web shows many food chains, illustrating more complex interdependencies.
Food Relationships on the Rocky Shore
Download a copy of the Food chains file:
Create 3 food chains by dragging and dropping the photos in order. Remember that food chains should start with a producer.
Now write out the three food chains you created. Don't forget the arrow that shows energy transfer, for example:
Then write out two more food chains. The food web above may help. You should have a total of 5 food chains.
Past Ecosystems
Past Ecosystems
Inquiry question: How do selection pressures within an ecosystem influence evolutionary change?
Activity 13 - Analyse evidence of past changes
Activity 13 - Analyse evidence of past changes
Use a range of secondary sources to investigate changes over time to rock platforms in the local area. Some suggestions include:
Port Hacking – Past and present of an estuarine environment, by A.D.Albani and G.Cotis. Section on ‘The Natural Environment – The Past’ pages 4-10.
The Australian Coast – Teacher notes and student activities: Download the document; refer to Chapter 7 – Sea level changes, pages 36-38 re historic changes to sea level.
Open Shire Maps: then click on ‘Go to Shire Maps’. Zoom in to the rock platform you visited and click between the aerial photos to visualise changes over time to the area.
DRAFT Royal National Park Guide (1991) – suggest sections on ‘Humans and the Land – The Aborigines’ and ‘History of the National Park’
Aboriginal Prehistory and Archaeology of Royal National Park and its Surrounding Landscapes: presentation and article
Create a Word or Google Doc. Describe three examples of evidence for past changes to rock platforms in the local area. Include images or maps showing change over time.
Future Ecosystems
Future Ecosystems
Inquiry question: How can human activity impact on an ecosystem?
Activity 14 - Human use and impact
Activity 14 - Human use and impact
Use the photos and online research to summarise human use and impact at Shelly Beach, Cronulla. Download and complete the table below or create your own.
Human use and impact.docxHuman use and impact worksheet
Aboriginal middens along the coast provide evidence of local Indigenous food resources obtained from rock platforms pre-invasion.
Some shells found in middens around Cronulla include turban shells, limpets, cart-rut shells, rock oysters and triton shells. These are denser shells that have not fully disintegrated over time unlike fish bones and abalone shells. These species still live in the rock pools and and on the rock platform.
Aboriginal cultural practices continue to include sourcing foods such as abalone, crabs, rock lobster and fish from the rock platform and the lower rock shelf.
Today there are limits placed on the size of fish and the number of shell fish that can be harvested along the coast. Intertidal protected areas and marine reserves exist to limit the impact of humans on various species and ecosystems.
Activity 15 - Management of future ecosystems
Activity 15 - Management of future ecosystems
Use a range of secondary sources to investigate:
models that humans can use to predict future impacts on biodiversity
the role of changing climate on ecosystems
practices used to restore damaged ecosystems
Suggested resources include:
Coastal Risk Australia: Search for the rock platform at Shelly Beach, Cronulla and zoom in. View current and predicted inundation by high tides.
CoastAdapt: In addition to background information, there are datasets to explore and Shoreline Explorer
Choose one model used to predict the impact of sea level rise (e.g. council’s sea level rise policy, CoastAdapt’s datasets or Coastal Risk Australia). What does the model predict for sea level change at the rock platform at Shelly Beach, Cronulla?
Referring to secondary sources, what are the impacts of climate change on rock platforms – now and in the future?
How can we manage the future of rock platforms on our coast?
Create your own Word or Google Doc.
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