Monthly Archives: January 2014

Hitchhiking, back-scratching and other inter-species favours

It’s not always such a savage world out there. Different species don’t only interact on a predator-and-prey level. Two species can provide a mutually useful service for each other (also called symbiosis). There are many examples of this:

  • Sea anemones hitchhike on the backs of hermit crabs, enabling them to travel further and eat the crab’s leftover food. But the crab also gains something too. Having these tentacled creatures on their backs fend off octopuses and other predators who might otherwise eat the hermit crab. Watch this guy moving his anemone friend from an old shell to a new.
  • African oxpeckers eat ticks off the backs of zebras and elephants. This enables the birds to eat but also does the bigger animals the service of removing parasites off their backs.
  • The classic example of symbiosis is often easily forgotten: simple insect pollination. The bees uses the flower’s pollen to make honey, while spreading the pollen further, enabling the plant to reproduce.

If your pupils are interested in learning more about different species, our brand new app Sorting for Early Science can introduce them to the foundation science vocabulary to get them started!

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Predator, prey, frogs and food chains

Most animals in a habitat can be classified as predators, prey or both. A predator is an animal which kills another animal (the prey) for food. For example, a snake is a predator because it eats frogs (prey). However, the frog is also a predator (however unintimidating it seems!) because it eats grasshoppers. With so many animals having differing diets, even a small environment can produce a food web such as this one.

ImageBecause the grass eats no other species, only consuming nutrients from the soil, we call it a producer. The fox and snake are called top consumers because no other species eats them within this habitat. But in certain habitats, large birds of prey eat snakes.

Food webs can be affected by even the most subtle increase or decrease in the number of any species. If, for example, the population of frogs increased in the above food chain, then several changes might take place:

1)       The number of grasshoppers would decrease because there are more frogs to eat them.

2)       More snakes would come to the habitat and prosper because there are more frogs to eat.

3)       Because there are more snakes, the number of rabbits will deplete as they will be eaten by the higher population of snakes.

Consider what might happen if:

a)       The population of mice increased

b)       The population of rabbits decreased

c)       A drought led to a poor crop of grass

Whether their population increases or decreases, each species within a habitat will be affected by changes in population to some degree.

If your class is interested in getting to grips with food chains, our app Pairing for Early Science introduces them with the foundation science vocabulary to get them started!

Below: predator extraordinaire, office cat, aka Mr Worthington

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