Chapter 15 – Interactions Within Ecosystems 15.1 – Groups of Living Things Interact 15.2 – Organisms Interact Differently 15.3 – Ecosystems Are Always Changing Source: McDougal Littell – 6th Grade Science 15.1 Groups of Living Things Interact … • Organisms occupy specific living areas • The smallest grouping is a species (animals that can reproduce and whose offspring can reproduce) • Population = a group of organisms (plant or animal) of the same species that occupy a particular area (ex: cacti, scorpions, rattlesnakes) • The boundary of an area defines a population. (Ex: cacti do not live in the same area as crabs, nor crabs with iguanas, but all 3 populations live on the Galapagos Islands) 15.1 Habitats & Niches • Habitat = Physical location where plants and animals live • Physical characteristics of a habitat = – Rainfall, temperature, soil quality – Determine which plants/animals live there – Determine which role/niche a plant or animal occupies – No two species fill the same niche – Niche is more than plant/animals role in food web. • (Ex: Plants provide nesting as well as produce food) 15.1 Communities • A biological community is a group of populations that live in a particular area and interact with each other. • The environment can be organized into 5 levels: – Biome, Ecosystem, Community, Population (of Species) & Organism 15.1 Ecosystem’s 5 levels • Biome = largest; describes in general terms the climate and types of plants/animals found in similar places. May contain several ecosystems within it. • Ecosystem = The living & non-living factors that interact to form a stable system. (smaller than a biome & includes only organisms and their local environment). • Community = living components of the ecosystem that interact with each other • Population = group of organisms of same species living in an area. • Organism = single individual (plant/animal) 15.1 Environment’s 5 levels Biome Ecosystems Communities Population of same species Organism 15.1 Population Patterns • Populations may be crowded together (schools/herds), spread apart, live in community groups, rise & fall with seasons, etc. • The distribution of animals/plants in a habitat is determined by how they meet their needs for food, water, shelter, nest space • Patterns in time = seasonal migrations of species (immigration into population/area or emigration from a population/area), spring births, winter deaths, etc. 15.2 Different Ways Organism Interact • Survival of one species might depend on another species (producers & consumers) – Symbiosis = relationship between individuals of two different species who live in close relationships • Competition – struggles between organisms (same species) or populations (different species) for limited resources – Predator-Prey (predator benefits; prey harmed) • Ex: Hawk & mouse; Strangler fig & tree – Parasite-Host (parasite benefits; host species harmed) 15.2 Cooperation Interactions – Not all animals of a species compete to survive. Some species cooperate to survive • Ex: bees, ants, wolves, whales – Commensalism (one benefits; the other is not affected) • Ex: Remora & shark; Clown fish & anemone – Mutualism (both species benefit) • Ex: Cattle egret & cow; bees/birds & flowers 15.2 Symbiotic Relationships • An ecosystem is more than just a collection of biotic & abiotic factors… • There are 3 types of symbiotic relationships which may overlap within any ecosystem and one species may be involved in more than one type of symbiotic relationship – Mutualism (both species helped) – Commensalism (one species helped; one unaffected) – Parasitism (one species helped; host species harmed) 15.3 Ecosystems Change • Populations change over time due to a variety of reasons: competition, predation, drought, etc. • Any factor(s) that limits growth of a species = a limiting factor – Too much/too little of any abiotic/biotic factor – Ex: poor soil; too many predators • Carrying capacity (cc`) = maximum number of individuals an ecosystem can support – CC is different for each population in an ecosystem • Ex: A river can support more turtles than alligators; more moose (herbivore) than wolves (apex predator) 15.3 Succession Changes • Succession = the gradual change in an ecosystem in which one biological community is replaced by another: Ex: Grassland becoming forest • Primary Succession = No prior species existed before new biological community becomes established (Ex: barren rock on lava flow. )Very slow process. • Secondary Succession = Takes place after major disturbance in an established ecosystem (Ex: forest fire burns forest, but soil remains). Happens more rapidly due to remains (soil, seeds, etc) of prior ecosystem 15.3 Primary Succession • No prior life exits (Ex: new lava flow, or glacier) • Takes a long time for pioneer species to move in and soil to be established (they stabilize soil, shade soil, add nutrients when they die/decay) • Pioneer species = the first living things to more into a barren (no life exists)ecosystem. – Ex: Pioneer Species = Mosses, lichens cling to rocks and begin soil formation on a lava flow. – After soil is formed, seeds for small plants & shrubs can take root, small animals appear – Finally large shrubs & trees appear, more animals appear 15.3 Secondary Succession • Comes after a major disturbance to an established/existing ecosystem (Ex: fire, flood, human habitat destruction like clearing forest for farmland). • Happens much faster as soil is already formed & residue of prior life exists (seeds, underground roots, etc) – Ex: Fire destroys forest; soil remains – Some trees regenerate from surviving roots/seeds as do grasses, shrubs. Small animals return – Large hardwood/deciduous trees return over time; more animals return 15.3 Patterns of Change • • All types of ecosystems have succession changes: grasslands, wetlands, river systems, forests, oceans, etc. Pattern always remains the same: 1. 2. 3. 4. First - producer species is established Second – decomposers & consumers arrive More producers decomposers, larger consumers Can happen over tens (secondary succession) or hundreds/thousands of years (primary succession)