1. Adapting to the extreme Life on the rocky shore…

2. Session outline An introduction to life on rocky shores
A look at what affects the distribution and population size of organisms living on rocky shores
A look at what lives where on the rocky shore and why

3. An introduction to the rocky shore
Changes daily (intertidal)
An ecosystem made up of many different habitats (habitats)
Whole range of biological and environmental factors affecting life
Rocky shores are intertidal ecosystems that are uncovered and covered by the tides daily. As such life that lives there has to have adaptations to living both in and outside of the water. Ask pupils if they know of any example organisms that live on rocky shores that show adaptations to living both in and out of the water. The limpet is a good one it n that it clamps down on the rocky substrate to reduce water loss when the tide is out, and when the tide is in actively grazes around on the algae growing on the shores. Anemones are also good examples in that they have tentacles which are contracted during low tide to reduce surface area for water loss and protruded during high tide to catch prey in their sticky tentacles.
Rocky shores are also not just one consistent environment. They are patchy ecosystems made up of many different types of habitats such as boulders, cracks and crevices, open bedrock and rock pools. As such, we get completely different communities of organisms from one habitat to the next because organisms that live there are adapted to living in the particular set of environmental conditions that effect that habitat.
This slideshow will discuss the range of biological and environmental factors that affect life on rocky shores. Ask pupils if they can think of any. E.g. predation, competition, temperature, salinity, oxygen concentration, sunlight etc…
The first thing this slideshow does is introduce pupils to a range of organisms commonly found on the rocky shore to give them an appreciation of the type of life that lives there You could maybe ask pupils which classification group each organism might belong to, particularly if you have previously run the classify this! Activity with the class.

4. Some Rocky Shore Inhabitants
Limpets
Herbivores
Strong muscular “foot”
- Hard shell
- Grazes the green slime (microalgae) on the rocks when the tide is in
Limpets are molluscs with a thick muscular foot called a radula and a single hard shell. They have iron teeth which help them grind away at the rock to produce a home scar – a watertight seal which helps prevent limpets from drying out during low tide. During high tide, limpets, just like terrestrial snails, raise their shells and graze on the microalgae growing on nearby rocks. Limpets can graze clean up to a meter around their home scar in one tidal cycle! Not bad for a snail!

5. Some Rocky Shore Inhabitants
Barnacles
Filter feeders
Legs modified for filter feeding
Can withdrawal into its shell
Hard shell in “plates” cemented to the rock
Barnacles are actually soft bodied crustaceans that produce a hard shell to protect themselves from predators and from drying out during low tide.
The fact at the bottom can easily be taken out but its quite an interesting one! Barnacles are sedentary organisms in that once they settle down from their larval phase they don’t move! Even though they live in dense populations with one another, barnacles may only find suitable mates are large distance away. An inflatable penis extending from a barnacles will therefore poke around the shells of neighbouring barnacles until a suitable mate is found! He will then deposit his sperm and fertilisation can begin.
Photo credits: Nick Aldred
The barnacle has the largest penis to body size ratio in the entire animal kingdom!
Did you know?

6. Some Rocky Shore Inhabitants
Marine Snails
Carnivores
Herbivores
Trap door (operculum) to close and open shell
Thick shell
Muscular foot
Top rocky shore predator!
Marine snails are represented by herbivores and carnivores on the rocky shore. The Dogwhelk is actually the top predator in the rocky shore ecosystem. It predates actively on limpets and barnacles, drilling holes into their shells with a saw like implement called the radula and digesting the soft animal inside the shell.

7. Some Rocky Shore Inhabitants
Brittle stars
Filter feeders
Legs adapted for feeding rather than movement
- Live in large colonies under rocks
- Can re-grow limbs
Photo credit: Reindert Nijland
Brittle stars are related to the starfish and are in the group echinoderm. They have hair covered legs which help them filter feed plankton for feeding. By living in large colonies they reduce the risk of predation – definitely a case of safety in numbers. They can also re-grow lost limbs which may be nipped off by passing fish. Starfish can also do the same.

8. Some Rocky Shore Inhabitants
Anemones
Carnivores
Sticky tentacles
Can withdrawal its tentacles into its body
Slimy, mucus covered body
Sticky, muscular disc to attach to rocks
Low tide
High tide
Anemones belong to the group cnidaria because of their thin-sac like bodies and sticky stinging tentacles. When the tide is out, anemones retract their tentacles reducing surface area for water loss. They also secrete a thick mucus to reduce water loss further. During high tide, anemones extend their tentacles laden with stinging cells catching passing prey. A thick muscular disk helps the anemone hold firm to the rocks in the crashing tide.

9. Some Rocky Shore Inhabitants
Crabs
Carnivores
- Hard shell (carapace)
Strong claws
Photo credits: Sara Marsham
Crabs belong to the group crustacea. Most pupils will be familiar with crabs and therefore we do not go into detail here.

10. Some Rocky Shore Inhabitants
Seaweeds
Primary producers
Thick, mucus covered fronds (leaves)
Tough and leathery
Air “bladders”
Strong holdfasts
Flexible stipes (stems)
Photo credits: Marleen Tenapel
Seaweeds are in abundance on the rocky shore.
Some seaweeds are tough and leathery with flexible stipes and a strong hold fast (root-like attachment to the rock) to avoid being washed away in the tide. Others have air bladders to help them float to the surface during high tide to carry out photosynthesis.

11. Some Rocky Shore Inhabitants
Slime (microalgae)
Primary producers
Colonies of tiny microscopic algae
Very important part of the rocky shore food web
Green microalgae form thick slippery mats on the rocky shore. However, they form the basis for seaweed succession (similar analogy to forest succession) and are a vital food source for rocky shore limpets. The above picture is an electron micrograph image of a green microalgae.

12. Some Rocky Shore Inhabitants
Starfish
Carnivores
Tube feet with suckers on
Flexible arms
Spines
Mouth on underside
Can re-grow arms
Photo credits: Malcolm Baptie
Starfish are echinoderms, echino meaning spikey and derm meaning skin. They have flexible arms and sticky tube feet which hep them stick to the rocks and avoid being washed away. A close up of the starfish tube feet are shown. (Jane maybe you want to talk about the tube feet system in realtion to hydrostatic pressure? Could be a good link to physics? Sorry I forgot how it works!)
One really interesting aspect of the starfish is the way it feeds. It literally expels its stomach from its body and digests its prey (e.g. a marine mollusc) outside of the body and sucks everything back in as a liquefied semi-digested gloop!
Starfish eject their entire stomachs in order to feed, dissolving their prey outside of their bodies, which they then suck back in as a semi-digested gloop!
Did you know?

13. Some Rocky Shore Inhabitants
Spiral worm
Filter feeders
Hard tube made of calcium carbonate
Stuck onto seaweeds and rocks
Feathery tentacles
Photo credit: Reindert Nijland
Spiral worms are annelid worms that have a hard tube of calcium carbonate to protect itself from predation. During high tide, it extends its feathery tentacles to feed on passing plankton. During low tide, the spiral worms close up their shell tightly to reduce waterloss.

14. Survival is Everything
Different habitats support different communities of organisms because the organisms that live there are adapted to their surrounding environment
Organisms can only survive in a habitat when they have all the essentials for life and reproduction
Lets learn about the range of adaptations plants and animals have on the rocky shore to deal with biological and environmental pressures
This slides focuses in on the fact that organisms can only survive where they can if they adapt to their environmental conditions, can avoid being eaten and can compete for resources.

15. Population size is determined by…
- How many predators the species has and how well it can avoid them
- How well adapted the species is to its environment
- The better adapted, the more likely it is to survive and pass its genes onto the next generation
Population
Size
1. Predation
3. Adaptation
2. Competition
Firstly though its important we understand what affects population size to give a context to what we will learn about life on the rocky shore.
Ask pupils if they can think of any before allowing each component to pop up on the slide.
Ask pupils if they understand the concept devised by Darwin of survival of the fittest. This slide very much hints towards this and there is a separate worksheet on Darwin theory that could be handed out during this slideshow or given out at a later date to consolidate pupils knowledge on the background theory to adaptation and survival.
When predation pops up, ask pupils to think about the ways organisms might avoid being eaten e.g. startle/escape responses, mucus secretion – bad taste, Hard outer shell, mutual relationships e.g. between hermit crabs and anemones. For further reference to adaptations to being an effective predator and an evasive prey in the marine environment please use the Dog eat dogfish world resource also in Module D. .
When competition pops up, ask pupils what else organisms on the rocky shore might compete for. Competition will ultimately limit the number of each species that can live in a particular habitat – Ask what the major one is for rocky shores - space
When adaptation comes up, ask pupils what an organisms environment is (i.e. their surroundings). Ask them to think of some of the environmental factors present on rocky shores organisms might have to adapt to.
- How much competition there is from other organisms for resources in short supply e.g. food, shelter.
- Stronger competitors will survive and pass their genes to the next generation