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Transcript
Organismal and Community Ecology Ecology (from the Greek oikos meaning "house" or "dwelling", and logos meaning "discourse") is the study of the interactions of organisms with each other and their environment. Definitions: • species – a group of similar organisms that can interbreed in nature to produce fertile, viable offspring • population – all the members of the same species living in the same, defined area • community – all the various populations living in the same, defined area. • ecosystem – the living (biotic) community plus the non-living (abiotic) components of the environment • biosphere – all the earth’s ecosystems, considered collectively • Levels of ecological study: • organismal ecology - the study of individual organisms' behavior, physiology, morphology, etc. in response to environmental challenges. • population ecology - the study of factors that affect and change the size and genetic composition of populations of organisms. • community ecology - the study of how community structure and organization are changed by interactions among living organisms • ecosystem ecology - the study of entire ecosystems, including the responses and changes in the community in response to the abiotic components of the ecosystem. This field is concerned with such large-scale topics as energy and nutrient cycling. • landscape ecology - the study of the exchanges of energy, materials, organisms, etc. between ecosystems. • global ecology - the study of the effects of regional changes in energy and matter exchange on the function and distribution of organisms across the biosphere. It's The Big Picture. Organismal Ecology An organism's ability to survive extremes of its environment reflect its evolutionary history. Homeostasis is the process of an organism maintaining a stable internal environment (with respect to temperature, salt balance, etc.). • regulators use metabolic means to maintain homeostasis in response to environmental changes. examples • endotherm - obtain heat by producing it internally, via metabolic reactions • homeotherm - regulate a constant body temperature by spending metabolic energy • note: the terms endotherm and homeotherm are more accurate, scientific ways to express the idea of an organism being "warm blooded" • conformers are less able to metabolically maintain homeostasis. Their internal environment is governed primarily by the external environment. examples • ectotherm - obtain heat from the external environment • poikilotherm - body temperature is regulated by the external environment • note: the terms ectotherm and poikilotherm are more accurate, scientific ways to express the idea of an organism being "cold blooded" Another example: osmoregulation - regulation of internal salt/water balance • anadromous (fish that migrate from a primary salt water home to a freshwater habitats, such as salmon) and catadromous (fish that migrate from freshwater to marine habitats, such as European eels) maintain constant salt balance in their tissues via their excretory systems (kidneys), even when their environments vary. They are regulators • Echinoderms, (starfish, sea urchins, sand dollars, etc.) have no excretory system, so are strictly limited to marine environments. Their tissues have the same salinity as sea water. They are conformers Community Ecology The study of inter-species interactions in a particular ecosystem is known as community ecology. Biological coevolution is the evolutionary change of one species triggered by interaction with another species. Example: Wolves hunt caribou, chasing them down to capture them. The slower caribou are more likely to be preyed upon, leaving the faster individuals to reproduce. The resulting faster offspring will be even more difficult for the wolves to catch, and only the fastest wolves (or perhaps the wolves who are genetically capable of devising strategies to hunt very fast prey) will get enough food to survive. An evolutionary “Cold War” ensues. Example: Flowers compete for pollinators. The plants that produce flowers (with colors, shapes and scents specific to particular pollinators) that attract the most effective pollinators will set the most seed and have the most offspring. The various species in an ecosystem have evolved over the millennia in response to pressures from both the environment and from other species with which they live and interact. The result is often a complex interaction between the two species, symbiosis. Symbiosis In Greek, sym means “together” and bios means life. Symbiosis is living together. This term refers to members of two different species (i.e., two populations) that have coevolved to have some type of ecological interaction that affects both populations. Here are some of the theoretical types of interactions that can evolve over many generations. In the table below, you will find a list of all the potential types of symbiotic interactions between two species/populations. Each relationship is an result of COEVOLUTION--species being molded by natural selection in response to INTERACTION WITH THE OTHER SPECIES. The Different Types of Symbiosis The table below shows all the possible different types of symbiotic interactions. "+" means that the population benefits from the interaction "-" means that the population is harmed by the interaction "0" means that the population is not affected by the interaction type of interaction obligate mutualism EXAMPLES: pop'n A pop'n B nature of effect + + obligatory; both populations benefit protocooperation EXAMPLES: + + NOT obligatory; both pop'ns benefit competition EXAMPLES: - - populations inhibit one another neutralism EXAMPLES: 0 0 populations do not affect one another predation EXAMPLES: + - predator (A) kills & consumes prey (B) parasitism + - parasite (A) exploits the host (B), but does not kill it outright + - parasitoid (A) lives within, and eventually kills host (B) at point of metamorphosis from one life cycle stage to another. + 0 commensal (A) benefits; host (B) not affected 0 - A unaffected; B inhibited EXAMPLES: parasitoidism EXAMPLES: commensalism EXAMPLES: amensalism EXAMPLES: Terminology for Interacting Species Ecological niche - Defined by the species, this is everything that an organism eats, where it nests, sleeps, forages, etc. In short, everything that defines its natural history. Two species can never occupy exactly the same ecological niche, or one will eventually become extinct. However, the niches of different species may overlap to some degree. When this happens, interspecific (i.e., between species) competition occurs. Keystone species - species on which many other populations ultimately depend for survival. Indicator species – a species whose population density indicates the overall health of an ecosystem. Native species - a species found in the place where it naturally evolved. Native populations often have complex and delicately-balanced interactions with one another that can be disrupted by the introduction of exotic species. Exotic species - a species living in a place where it did not originally evolved. Some exotic species introduced into new environments are much better able than native species to compete for resources, and they can sometimes displace native species. This can have profound effects on the other native species that once relied on a native species driven extinct (or to great scarcity) by an invasive exotic species. Results of Predation: Camouflage and Warning Coloration Crypsis/cryptic coloration - camouflage Aposematism/aposematic coloration - warning coloration (distasteful or dangerous species) Mimicry - a species has evolved the superficial appearance of something else Batesian Mimicry - a harmless mimic looks like a poisonous model. Examples: Harmless Viceroy butterfly mimics poisonous Monarch butterfly. Non-venomous Kingsnake mimics venomous coral snake Mullerian Mimicry - several poisonous/distasteful species resemble one another. Examples: Several species of poisonous Ithomiid butterflies resemble each other. Many species of venomous, stinging hymenopterans (bees, wasps, etc.) have yellow bodies with black stripes. Know the difference: poisonous – toxic when eaten or touched venomous – delivers toxin with an apparatus such as a fang or stinger