The Forestry Commission have planted lots of trees in Scotland, often in quite wet and boggy countryside. These trees are mainly Sitka spruce, which are evergreen and are planted close together. Which of the following might explain why there are not many plants growing on the forest floor?

Organisms are well adapted to survive in their normal environment. Population size depends on a variety of factors including competition, predation, disease and human influences. Both plants and animals compete for the resources in their habitat. There are two types of competition; inter-species (different types of animal competing for the same resources) and intra-species (animals of the same type competing for resources). Animals compete for food, water, territory and (intra-species only) mates. Natural selection reduces inter-species competition to a degree as it reinforces behavioral... Show more

Organisms are well adapted to survive in their normal environment. Population size depends on a variety of factors including competition, predation, disease and human influences. Both plants and animals compete for the resources in their habitat. There are two types of competition; inter-species (different types of animal competing for the same resources) and intra-species (animals of the same type competing for resources).

Animals compete for food, water, territory and (intra-species only) mates. Natural selection reduces inter-species competition to a degree as it reinforces behavioral adaptations like feeding at different times of day, eating different types of food or feeding at different heights where there are trees. This means that two or more species can occupy the same territory and competition will only be for water.

Plants make their own food by the process of photosynthesis. This happens in the chloroplasts where chlorophyll turns water and carbon dioxide into sugars. These sugars are either stored as starches or used for respiration to keep the plant alive. So plants don't need to compete for food. But they still need water and light for the process of photosynthesis and must compete for those. They also need mineral salts that are found dissolved in the water in the soil which is one reason they compete for space to grow as well.

Every habitat has its own unique set of organisms living there. These are the ones who compete successfully for the resources. If something changes in the environment, population numbers will change and a species that can no longer compete will disappear from the habitat.

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