Life in the Tweed (KS2/2nd level)

Rivers are incredibly important for biodiversity. Not only do many animals and plants around the world depend on their flowing water to survive, rivers also act as corridors connecting organisms with their natural habitats.

The River Tweed is no different. Work your way through this lesson to discover more about the River Tweed's ecosystem.

A habitat is a place in which animals and plants make their home.

Animals and plants are adapted to their own habitats. This means that they have special features to be best suited to the conditions in their habitat. Therefore, when the right conditions are met (such as temperature, amount of sun light, soil type and cover), the habitat is desirable and the organism can thrive. However, if the conditions are not right, then the habitat becomes unsuitable.

A community of animals, plants and microorganisms together with their habitat is called an ecosystem. For example, a river ecosystem might consist of a river (the habitat), in which there are plants growing, fish swimming, and dippers and otters feeding.

The living parts of an ecosystem (the animals, plants and microorganisms) are called the biotic factors of an ecosystem.

The non-living parts of an ecosystem (such as soil, water, sun light and oxygen) are called the abiotic factors of an ecosystem.

If one part of an ecosystem is changed (for example, there were suddenly no plants in a river) then this could have an effect on the rest of the ecosystem. This is because each part of the ecosystem is linked; the living organisms all interact with each other and their habitat.

The health of an ecosystem depends on the interactions between the different biotic and abiotic factors.

One of the ways in which the organisms in an ecosystem interact is through food chains.

Food chains show how energy is passed between the living organisms in an ecosystem.

Animals and plants get energy from their food. For example, a rabbit gets its energy from eating grass, while a fox might get its energy from eating a rabbit. The arrows in a food chain show the direction in which energy is being passed on.

Have a look at an example of a food chain in the River Tweed.

Every food chain starts with the sun.

Energy from the sun is taken in by a producer. A producer is an organism that can generate its own food. Producers are usually plants which can use the energy from the sun to generate their own food through photosynthesis.

Producers are then eaten by consumers. A consumer is an animal or plant that eats other living things. There can be more than one consumer in one food chain, with some animals eating other animals. Consumers can therefore be predators and prey.

Lets look at an example of a simple food chain from the River Tweed.

Most organisms do not just eat one thing. As an example, a fish does not just eat one type of invertebrate, it would tend to eat lots of different types of invertebrate and maybe even other fish. It would therefore be getting energy from several sources, not just the one.

When this is the case, food chains become known as food webs and, the more organisms there are in an ecosystem, the more complicated food webs tend to get.

Lets have a look at a typical food web from the River Tweed.

The River Tweed is home for many different animals and plants, all of which are part of the river's ecosystem.

Lets have a look at some of the different organisms living in the river and what their roles in the ecosystem might be.

Plants are a crucial part of any freshwater ecosystem, including the River Tweed's.

They play an important role in-river, helping to keep the water clean by absorbing nutrients and producing oxygen, while also providing great cover for the likes of invertebrates and fish.

Plants growing alongside the river also provide great benefits: their roots help to stabilize banksides, fallen leaves add nutrients to the river, they can help prevent pollution in the river, and they can also shade the river to cool the water.

The River Tweed is well known for its species-rich plant life and is a designated Special Area of Conservation (SAC) for crowfoot (Ranunculus) and flowering-rush (Butomus umbellatus).

There are lots of freshwater invertebrates that live in the Tweed and, though they are small and often go unnoticed, they are hugely important in the river.

• They are a valuable food source for lots of organisms.
• They help keep the rivers clean by feeding on the likes of algae and dead leaves.
• They are indicator species which can tell us how clean the river is.

The River Tweed is home to over 20 species of fish. They are not only an important part of the river's ecosystem, but they are also incredibly important for the Tweed's local communities.

The River Tweed is home for many different bird species. Some of these birds eat fish, like the kingfisher, while others eat invertebrates, like the dipper. They are therefore an important part of the River Tweed's ecosystem.

The River Tweed is home to several species of mammal. These include the water vole as well as the otter, both of which are often hard to see as they like to hide out of sight.