Lecture 5 Role and Function of Past and Present Ecosystems: Community Stability and Instability and disharmonious communities How Biological Communities Function: - At the simplest level, a biological community can be the interaction between one species and another. - Predator feeds on prey - Parasite feeds on a host - Plant relies on a pollinator - Associations of species: o Groups of plants or animals found together that have similar environmental requirements o Examples: alpine tundra plants, alkaline soil plants, tropical forest monkeys and ocean floor scavengers o As long as the competitive interactions are not too strong, the species are able to co-exist with one another - however this relies upon sufficient resources and to some extent survival of the fittest. - Identifiable patterns: o Some species associations occur regularly in many regions o Typified by a few characteristic species with a narrow range of ecological requirements: stenotopic species. o E.g. tropical rainforest ecosystem: plants here require moisture, warmth and a stable ecosystem - they require specific physical conditions to survive. o Stenotopic: have a short narrow range Could describe human beings as being stenotopic as are the only organisms in the world who modifies it's environment to suit our needs - in this case, to suit a tropical adaptation of 37degrees Celcius. o E.g. the ground beetle Amara alpina livesonly on arctic and alpine tundra, in cold, dry habitats. This beetle is the most-cold adapted beetle in the world and can survive 2/3 degrees C maximum summer temperatures. This beetle allows parts of it's body to freeze but ensures the lung, heart and brain continue to function. The female ground beetle must wait for up to 5/6 years before it has stored enough energy with which to produce eggs from. After one batch of eggs, this beetle will then die. Wherever you find this species, you also find other cold-adapted tundra insects, such as the rove beetles Micralymma brevilingue and Holoboreaphilus nordenskieldi. Nature of Ecological Communities: - A community is an assemblage of different species - Occur at different spatial scales. - May be limited to specific groups (a plant community, a soil microbial community, etc.) or refer to the biotic part of a whole ecosystem. - BR - would be a temperate deciduous forest Nature of Biological Guilds: - Groups of animals that all play the same role in a community are known as guilds. - Species in a guild each utilize same kinds of resources (food, nesting, or den sites) in similar manner. - Emphasis is on groups most likely to compete because of similarity in ecological niches - Guild species can be taxonomically unrelated - The term guild derives from the trade guilds : groups of people engaged in the same trade (e.g. gold smiths). Species Hunting time Group hunting Hunting method Lion Night Yes - female groups Mainly stealth, no scavenging - E.g. Predator guild of African Savannah: lion, leopard, cheetah, hyena, African hunting dog. Cheetah Day No - solitary Speed - no scavenging