ECOSYSTEMS AND THEIR LIVING COMMUNITIES

ECOSYSTEMS AND THEIR LIVING COMMUNITIES

COMMUNITY Each community is made up of populations of various organisms living in the same location at the same time. community 1 = popln 1 + popln 2 + popln 3 Each population consists of one species that may be a different species of animal. Plant, fungus, protist or microbe. Communities in different ecosystems n differ in their diversity. Diversity is not just a measure of the number of different populations (or different species) present in a community.

Community continued Ecologists measure two factors when comparing diversity of different communities: 1. the richness or number of different species present in the sample of the community, and 2. the evenness or relative abundance of the different species in the sample. Populations found in the different communities differ according to environmental conditions. Members of the populations in each community show features that equip them for survival and reproduction in the particular environmental conditions.

Community continued The community is one part of an ecosystem. Put simply, an ecosystem consists of a community, its physical surroundings and the interactions within and between them. Different levels of biological organisation A community is one part of an ecosystem Cell Organisation Population Community Ecosystem

ECOSYSTEMS Each ecosystem includes a living and a nonliving part: LIVING Community NON-LIVING Physical surroundings but there is also interactions both within the community and between the community and its non-living surroundings. Ecosystems can vary in size but must be large enough to allow the interactions necessary to maintain them.

ECOLOGICAL GROUPINGS WITHIN AN ECOSYSTEM Members of every community can be identified as belonging to one of the following ecological groups: Producers or Autotrophs: Organisms that manufacture organic compounds from inorganic compounds using sunlight as an energy source. ie. PHOTOSYNTHESIS They make chemical energy available in the form of organic compounds that are for own use and directly or indirectly Aquatic ecosystems: producers are microscopic phytoplankton, macroscopic algae and seagrasses. Terrestrial ecosystems: producers are green plants, such as trees & grasses, flowering plants, pines, ferns and mosses

Ecological groupings within an ecosystem continued Consumers and heterotrophs Members of a community that must obtain energy by eating other organisms or parts of them. Consumer organisms can be subdivided into the following groups: Herbivores that eat plants Carnivores that eat animals Omnivores that eat both plants & animals Detritivores that eat decomposing organic matter Particles of organic matter are called detritus. Detritivores use this as a source of energy. Eg. Dead leaves, faeces, rotting algae, dead organisms

Ecological groupings within an ecosystem continued Decomposers Organisms that obtain their energy and nutrients from dead organic matter. Different from other organisms because they chemically break down into simple inorganic forms. These mineral nutrients are returned to the environment and are recycled when they are taken up by producer organisms.

INTERACTIONS WITHIN ECOSYSTEMS In ecosystems, interactions are continually occurring: between the living community and its abiotic surroundings within the abiotic surroundings within the living community Interactions: between organisms and their surroundings Can affect both the surroundings and the organism Eg. Stunted tree on sea cliff

Interactions within ecosystems continued O2 INPUTS OUTPUTS WATER CO2 O2 CO2 FOOD O2 MINERALS WATER URINE

Interactions within ecosystems continued Interactions within the abiotic surroundings Examples of interactions are: - high temps and wind speed over an extended period produce an increase in the evaporation rate that causes the disappearance of surface water - a sudden storm brings a downpour causing localised flooding as creek beds fill and overflow and soil is washed away, causing erosion.

Interactions within ecosystems continued Interactions within a living community Interactions within the community of an ecosystem may involve members of the same specie, or may involve members of different species These interactions can be classified in various ways and include: - Competition - Predator-prey relationship - Parasitism - Mutualism - Commensalism

COMPETITION Intra-specific competition - competition between members of the same species for resources Eg. 1. 2. Inter-specific competition members of a population of one species competes with members of populations of other species Eg. 1. 2.

Competition continued Competition occurs when one organism or one species is more efficient than another in gaining access to a limited resource, such as light, water or territory. Competitive interactions may involve the use of chemicals. Chemical inhibition of this type is called allelopathy. An example is when pine needles fall, they release allelochemicals that prevent growth of other species

PREDATOR-PREY RELATIONSHIPS Occurs when one species (the predator) kills and eats another living animal (the prey). Carnivorous heterotrophs have structural, physiological and behavioural features that assist them to obtain food. These features are as varied as their food source. Eg. Some different ways carnivores capture and eat their living prey are grasping, ambushing, pursuing, filtering, tearing constricting,, Predators come in many different shapes, sizes and abilities, eg. Compare a lioness and a net-casting spider

Predator-prey relationship continued In the community of an ecosystem, predators are NOT always successful in obtaining their prey. Various prey species show structural, biochemical and behavioural features that reduce the chance of becoming a meal. Camouflage look like something else. Eg. Stick insect, Mimicry look like something distasteful. Eg. Hoverfly looks like a bee

Predator-prey relationship continued Behavioural features Stay still - some rodents freeze when a predator is about Keep a lookout meekats have one member act as a sentry Schooling safety in numbers, such as a school of fish where an individual has a higher chance of not being eaten than one organism that is separated from the group. Biochemical features produce repellent or distasteful chemicals. Eg. Monarch butterfly caterpillar which is brightly coloured as a warning

PARASITE-HOST RELATIONSHIPS ANIMALS One kind of organism (the parasite) lives on or in another kind (the host) and feeds on it, typically without killing it. - But the host suffers various negative effects in this relationship and only the parasite benefits Variety of animals are parasitic, including insects, worms, crustaceans, plants, fungi and microbes. It s estimated that parasites outnumber free-living species by about four to one. EXOPARASITES parasites that live ON their host Eg. Ticks, fleas, Athlete s foot, lamprey, etc ENDOPARASITES parasites that live INSIDE their host Eg. Roundworms, tapeworms, etc

Parasite-host relationships continued PLANTS There are two kinds in the Plant Kingdom: Holo-parasitism parasite is totally dependent on the host plant for all its nutrients. Hemi-parasitism parasite obtains some nutrients, such as water and minerals, from its host but makes some of its own food through photosynthesis. PARASITOIDS Kill their hosts that are usually another kind of insect A parasitoid-host relationship has a longer duration before the host dies. Eg. Small wasps and flies lay eggs on caterpillars of particular butterflies or moths. Used in agriculture for biological control

MUTUALISM Prolonged association of two different species in which both partners gain some benefit. Some examples of mutualism are: - Mistletoe birds and mistletoe plants - Fungi and algae that form lichens - Nitrogen-fixing bacteria and certain plants

COMMENSALISM One member gains benefit and the other member neither suffers harm nor gains apparent benefit. An example is the clown fish that lives among the tentacles of sea anemones for shelter and food scraps

Interactions such as parasitism, mutualism and commensalism are sometimes grouped under the general term symbiosis. SYMBIOSIS (= living together) a prolonged association in which there is benefit to at least one partner MINIMISING COMPETITION Various species in the same community differ in the use that they make of a resource, such as food or space, and show niche separation If however, two species use the same resource in similar ways, they can be said to show niche overlap the greater the niche overlap, the greater the intensity of competition between two species