Ecology

What is ecology? The study of interactions between organisms and their environment Remember: Cell  Tissue  Organ  Organ System  Organism (species)  Population  Community  Ecosystem  Biome  Biosphere Ecology starts with the Organism!

Levels of Organization Ecology primarily involves the study of organisms, populations, and communities within ecosystems –Population – group of like organisms (the same species which can breed) –Community – all of the different populations that live in the same place

Ecosystems Include the living and non-living things that interact in an area Biotic factors – all living things –Animals, plants, bacteria, etc. Abiotic factors – non-living parts of an organism’s environment –Air, water, soil, light, wind, climate, etc.

Ecological Niche An organism’s place in the habitat; it’s role or way of life –Sum total of all biotic and abiotic resources a species uses –Fundamental – niche potentially occupied (includes space and resources that could be used) –Realized – portion of the fundamental niche the species actually occupies

Interspecific Interactions May be positive, negative, or neutral for a given species Include competition, predation, and symbiotic relationships In all interactions, the population numbers of one member affect the numbers of the other

Competition (-/-) Occurs when organism’s use the same resources in an area –The more the resource is limited, the more competition –Can result in the reduction or extinction of some species –Keeps two species from occupying the same niche

Predation (+/-) Predator / prey relationship; one organism feeds on a another –Includes herbivory Both predator and prey have adaptations to help in survival –Camouflage, spines, claws, speed, mimicry, etc.

Symbiosis Two or more species live in direct contact –Mutualism (+/+) – both species benefit –Commensalism (+/o) – one benefits, the other is neither helped nor harmed –Parasitism (+/-) – one benefits while the other is harmed Includes parasite and host Parasite usually uses host for nutrition (endo or ecto) May lead to coevolution – change in one leads to a change in the other

Energy in an Ecosystem Living systems require a constant input of energy……..the sun! Energy must be captured and used by organisms in order to function and carry out necessary activities Creates trophic structure – feeding relationships –Trophic levels – links or steps in a food chain or web determined by how organisms obtain energy

Trophic Levels Producers/Autotrophs – make their own food –Most carry out photosynthesis to convert light energy to food (glucose) –Some carry out chemosynthesis to convert chemical energy into carbohydrates Several types of bacteria The basis of food webs and essentially determine the success of the ecosystem

Heterotrophs – rely on other organisms for energy and food; must “eat” Includes consumers: –Primary – eat producers Herbivores and omnivores –Secondary – eat primary consumer Carnivores and omnivores –Tertiary – eat secondary consumer Carnivores and omnivores Detritivores and scavengers are also consumers

Decomposers – get energy by breaking down remains of organisms and organic matter –Also heterotrophs –Include fungi and bacteria

Keystone Species Exert control on community structure by important ecological niches –May be recognized by removal –May keep other species in check Examples: starfish in the intertidal zone; sea otters in the kelp forest Removal or loss of keystone species can be detrimental to ecosystem –Other species take over and deplete resources

Energy Flow Energy flows in one direction: sun (or chemicals)  autotrophs  heterotrophs Flow represented by models/diagrams: –Food Chain – basic series of steps in which energy is transferred from one organism to another (Grass  Mouse  Snake  Hawk) –Food Web – network of complex food chains representative of an ecosystem

Kelp Forest Food Web

Energy Transfer Producers use most of the energy they make for themselves. Energy not used is passed to the primary consumer which uses some and stores some. This can be transferred to the secondary consumer and so on…

Energy Loss As a food chain progresses, there is a loss of energy in the form of heat. Only about 10% of the energy available within one trophic level is transferred to organisms at the next trophic level Energy pyramids represent this change in energy The higher the consumer, the more it has to eat because there is less energy in its food! This is why food chains rarely go beyond 5 levels

Biodiversity Diversity of species in a community –Includes species richness (variety) and relative abundance of each species –Also includes genetic diversity (alleles) and ecosystem diversity Related to size and geographic location –Generally lower, the farther from the equator

Threats to Biodiversity HUMANS!!! –Habitat destruction –Introduced species – can overtake ecosystems and lead to extinction of native species (become invasive) Lack competitors and predators –Overexploitation –Disruption of food chains Natural disasters and climate change Geological and meteorological change

Ecosystem Stability Typically, the more diverse the ecosystem, the more stable Greater diversity = greater resilience to change However, ecosystems are affected by many disturbances

Disturbances Events such as storms, fires, floods, droughts, overgrazing, or human activities that impact dynamic homeostasis of the ecosystem Any change in free energy can also affect populations in the ecosystem Lead to changes in community composition and structure –Called ecological succession

Ecological Succession Primary succession – development of a lifeless area without soil –Volcanic island Secondary succession – occurs in an existing community that has been cleared but still has intact soil –Forest fire

Succession Pioneer species – the first to inhabit an area –Often lichens - symbiotic fungi and algae Can grow in harsh conditions and help to create soil Pioneer species followed by grasses, small plants, softwood trees and hardwood trees End result = Climax community – a stable, flourishing ecosystem