Populations and Ecosystems

Objectives To define the terms abiotic, biotic, biosphere, habitat, niche, population, community and ecosystem and to be able to state examples.

Ecology Individualpopulationscommunities organisms How individualsPresence/absencecomposition/ Are affected byabundance/raritystructure/ Their biotic andtrends/fluctuationsfunctioning of Abioticcommunities environment

Definitions Abiotic the non-living components of the environment. Biotic the living components of the environment. Biosphere the life supporting layer of land, air and water that surrounds the Earth.

Definitions A habitat is a place where an organism lives (It’s address). A niche is its role in the ecosystem (it’s profession) ALL THE CONDITIONS AND RESOURCES REQUIRED FOR AN ORGANISM TO SURVIVE and maintain a viable population. A population is a group of individuals of the same species found in the same habitat, that can interbreed with each other.

Community refers to all the organisms, of all the different species, living in a habitat. An ecosystem - ‘the living world and its habitat’ Sir Arthur Tansley (1935). This includes the organisms (biotic) and the physical and chemical factors (abiotic). Difficult to find the boundaries! Consider scale!

Food chains Nutrients stay in a biological system and are recycled continually. Energy is transferred in a system from one organism to another. The organisms involved make up a food chain. At the bottom of the food chain are the photosynthetic producers which range from single- celled bacteria to redwood trees. Next come the primary consumers who are eaten by the secondary consumers who are eaten by… you get the idea.

Food webs

Key Words HabitatNiche PopulationCommunity EcosystemTrophic level Primary consumerSecondary consumer Food chain Food webProducer SpeciesEnvironment

In the following passage state the word that best replaces each of the numbers in the brackets. The study of the inter-relationships between organisms and their environment is called (1). An ecosystem is more or less self-contained made up of all the living or (2) features and non- living or (3) features in a specific area. Within each ecosystem are different groups of interbreeding organisms, called a (4), in a particular place at the same time.

Mnemiopsis leidyi