ECOLOGY Biotic and abiotic factors Food chain and food web Energy transfer Ecological pyramids

What is ECOLOGY? The study of the distribution patterns of organisms, their numbers, their interactions with one another, and their relationships to their environment The study of how organisms interact with their physical and biological environments Interactions are necessary because there is only one source of energy (the sun) All living organisms depend on the flow and harvesting of life-supporting solar energy through photosynthesis

Ecological Terms POPULATION: a group of interbreeding organisms of the same species, all occupying a defined area at the same time. COMMUNITY: all the different species or all the populations of plants, animals and microorganisms that live and interact in a particular area. HABITAT: the place where an organism lives, i.e. where it obtains its food and shelter, and where it reproduces. ENVIRONMENT: everything in the surroundings of an organism that could possibly influence it.

Ecological Terms Environment Abiotic (non-living) or physical environment Light, temperature, water, oxygen, salinity of water, pH of water and soil Biotic (living) environment All species of plants, animals, microorganisms that interact with each other

Ecological Terms NICHE: refers to where and how an organism lives within its habitat. Includes an organism’s behaviour, interactions with its living (biotic) and non-living (abiotic) environments, and the role it plays in its habitat ECOSYSTEM: a community of organisms, interacting with one another and their abiotic environment to form a more or less balanced, self-supporting unit with its own characteristic pattern of energy flow and nutrient cycling.

Ecological Terms Energy from the sun enters an ecosystem and flows through it in a linear or non-cyclic manner. Inorganic nutrients are obtained from the physical (abiotic) environment and flows through the ecosystem in a cyclic manner.

Feeding relationships of an ecosystem TROPHIC LEVEL: refers to the position or stage at which organisms obtain their food CONSTITUENTS OF TROPHIC LEVELS Producers or autotrophs Consumers or heterotrophs Decomposers or detritivores

Feeding relationships of an ecosystem Producers or autotrophs Mainly green plants and photosynthetic bacteria that can convert light energy from the sun into chemical energy Stored in their organic food substances during photosynthesis Manufacture complex organic food substances from raw inorganic materials Trophic level that ultimately supports all others

Feeding relationships of an ecosystem Consumers or heterotrophs Obtain energy from other organisms on which they feed Require continued supplies of organic compounds as food Primary consumers or herbivores feed directly on plants (producers) Secondary consumers or carnivores feed on herbivores (primary consumers) A predator is a carnivore that kills and eats its prey A scavenger is a carnivore that eats the dead remains of animals

Feeding relationships of an ecosystem Decomposers or detritivores Extracellular enzymes from decomposers (bacteria and fungi) break down complex organic materials in waste and decaying material Simple, soluble organic material (glucose) diffuses into the bodies of decomposers Glucose is used for respiration of decomposers, releasing carbon dioxide into the atmosphere

Food Chain Linear transfer of energy from plants through a series of organisms Each stage is known as a trophic level Not more than 3-5 links due to energy loss at each trophic level

Food Web Web-like feeding relationship between organisms of interlocking and inteconnecting food chains

Pyramid of Numbers A bar diagram indicating the relative numbers of organisms at each trophic level at any one time in a given unit area in a food chain Characteristics of a typical pyramid of numbers: Ecosystems are populated by a large number of small animals and a progressively smaller number of larger animals Predators are larger than prey Small creatures reproduce faster than larger creatures

Pyramid of Numbers Disadvantage: inverted pyramid of numbers

Pyramid of Biomass Represents the total biomass at each trophic level at any one time in a given unit area Biomass = number of individuals per unit area  dry mass of each individual Inverted pyramid of biomass When biomass of phytoplankton is less than biomass of zooplankton

Pyramid of Energy Amount of energy at each trophic level per unit area over a given period of time About 90% of energy is lost when transferred from one trophic level to the next as heat energy during respiration at every trophic level through faeces (undigested food material) egested by consumers through excretory product, eg urea, from consumers The total energy decreases progressively along the food chain, thus the pyramid of energy is always broad at the base and narrow towards the apex (upright shape)

Non-cyclic energy flow in an ecosystem Ultimate source of energy is the sun Flow of energy is non-cyclic Eventually all energy that entered ecosystem is lost as heat energy

Useful websites Definitions of ecological terms, food chains, pyramids Click on Ecology Feeding relationships, energy loss and ecological pyramids ngrelationshipsrev2.shtml The physical (abiotic) environment Adaptations of plants living in dry and wet habitats (xerophytes and hydrophytes) Website 1: Click on xerophytic adaptations to show marram grass, a xerophytic plant Website 2: Click on Nymphaea leaf c.s. (hydrophytic leaf)