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Principles of Ecology Topic 24 I. Ecological organization A. Ecology - the study of the interactions of plants and animals and their interrelationships with the physical environment B. Populations - all the members of a species living in a given area species - group of organisms capable of interbreeding among themselves C. Communities - all the plant and animal populations of a given area D. Ecosystems - a self-contained, interdependent system of living and nonliving things - must have 2 things 1. Constant source of energy 2. Continuous recycling of materials E. Biosphere - portion of the earth in which life exists - includes water, land, and air (hydrosphere, lithosphere, and atmosphere) II. Characteristics of Ecosystems A. Abiotic factors - non-living factors often known as the limiting factors because they limit the plant/animals that can be found in the ecosystem 1. Moisture 2. Temperature 3. Nutrients in soil 4. Gases B. Biotic factors - living part of the ecosystem C. Nutritional Relationships 1. Autotrophic nutrition - make their own food 2. Heterotrophic nutrition - get their own food from the environment a. saprophytes - use dead organic matter as a source of food - they are decomposers - break down the organic remains of organisms - include bacteria of decay (molds, fungi) b. herbivores - eat plants c. carnivores - eat other animals (1) predators - kill and eat other living things (2) scavengers - eat dead organisms that they have not killed themselves d. omnivores - eat both animals and plants 3. Symbiotic relationships - a relationship in which two organisms live together in a close nutritional relationship a. commensalism-one organism benefits, the other is neither harmed nor benefits b. mutualism-both organisms benefit c. parasitism- one benefits and the other is harmed Examples of symbiosis A. commensalism – one benefits and the other is not hurt or harmed (1) remora (shark sucker) and shark (2) barnacle and whale B. Mutualism – both benefit (1) (2) (3) (4) (5) bird and rhinoceros lichens – fungus and algae nitrogen-fixing bacteria and legumes protozoa and termites intestinal bacteria and humans C. Parasitism – one hurt and the other benefits (1) (2) (3) (4) (5) (6) (7) leeches ticks sea lampreys mistletoe ectoparasites – cling to exterior surface endoparasites – live within the host tapeworm - human D. Energy flow 1. Food chain - starts with a green plant or other autotroph that converts sunlight to food - this energy is then passed on to a series of animals example: grass --> grasshopper --> frog --> hawk 2. Food webs - all the food chains in a community - most organisms eat more than one type of organism a. producers - autotrophs - make own food b. consumers - feed on other organisms two types - primary eat plants directly, secondary eat organisms that fed on plants c. decomposers - break down organic wastes and remains of other organisms 3. Pyramid of energy - as energy is transferred from producer to consumer, much of the energy is lost therefore there is more energy at the producer level 4. Pyramid of biomass - the amount of living material at each level - there is more biomass at the producer level E. Material Cycles 1. Carbon-hydrogen-oxygen cycle these are cycled by the process of respiration and photosynthesis 2. Water cycle - evaporation, condensation, and precipitation 3. Nitrogen cycle a. nitrogen-fixing bacteria - convert free nitrogen into nitrates - the nitrates are absorbed by plants (legumes) b. decomposers - bacteria of decay convert nitrogenous wastes into ammonia c. nitrifying bacteria - convert ammonia into nitrates d. denitrifying bacteria - break down nitrogen compounds into free nitrogen which returns to the atmosphere III. Ecosystem Development A. Succession - the replacement of one type of community by another 1. Pioneer organisms - first plants to populate an area (lichens) 2. Changes in the environment - pioneer organisms change the environment so other organisms can survive 3. Plant successions - pioneer organisms --> grasses --> shrubs --> conifers --> deciduous trees 4. Animal successions - plants (flora) are the source of food for the animals (fauna) therefore the animals will change with the plants 5. Types of communities - determined by dominant plant species 6. Climax communities - when a community becomes stable and does not change unless a catastrophe occurs B. Types of ecological succession 1. primary - no soil present – must be formed first 2. secondary – soil is already present – occurs after something such as a forest fire or hurricane – faster than primary B. Competition - conflict between organisms for natural resources C. Niches - the role or job of a species in its ecosystem – no two organisms can occupy the same niche IV. Biomes A. Biomes - the kind of climax ecosystem that develops in a large climatic area - may be terrestrial (land) or aquatic (water) 1. Terrestrial Biomes - climate zones are determined by latitude, altitude, large bodies of water, mountains, and deserts - all modify the climate of the nearby regions climate includes the temp. range and amounts of precipitation and solar radiation received a. Kinds of Terrestrial Biomes 1. Tundra - permanently frozen subsoil (permafrost) plants - lichens, mosses, grasses animals - caribou, snowy owl 2. Taiga - long severe winters, summers with thawing subsoil plants - conifers animals - moose, black bear 3. Temperate Deciduous Forest - Moderate precipitation, cold winters, warm summers plants - deciduous trees (maple, oak, beech) animals - gray squirrel, fox, deer 4. Tropical forest - heavy rainfall, constant warmth plants - many species of broad-leaved plants animals - snake, monkey, leopard 5. Grassland - considerable variability in rainfall and temperature, strong prevailing winds plants - grasses animals - pronghorn antelope, prairie dog, bison 6. Desert - sparse rainfall, extreme daily temperature fluctuations plants - drought resistant shrubs and succulent plants animals - kangaroo rat, lizard b. Effects of latitude and altitude - with increasing distance from the equator, temp and rainfall show more variation during the year increasing altitude has the same effect on climate as increasing latitude B. Aquatic Biomes - make up the largest ecosystem on the earth - more than 70% of the earth’s surface is covered by water - the majority of living things on earth are waterdwellers more stable than terrestrial biomes - show less variation in temp because water has a great capacity to absorb and hold heat organisms are affected by dissolved oxygen, carbon dioxide, temp, light, kinds and amounts of minerals and particles Most photosynthesis takes place near the surface since the light intensity is higher there Aquatic organisms are well adapted for the removal of dissolve oxygen from water. They also have adaptations for maintenance of proper water balance in their cells which is affected by the salt concentration 1. Different types of Aquatic biomes a. marine biome - salt water biome - includes all the oceans most stable environment on earth absorbs and holds large quantities of solar heat, thereby stabilizing the earth’s temperature contains a relatively constant supply of nutrients and dissolved salts it serves as a habitat for a large number and wide variety of organisms much of the photosynthesis on earth occurs along the edges of the land masses (coastal waters) b. Freshwater Biomes - includes ponds, lakes, and rivers - vary widely in size, temp, oxygen content, carbon dioxide content, amounts of particles, current velocity, and rate of succession ponds and lakes tend to fill in over time - dead plant material accumulates on the bottom and around the banks and makes the water shallower - goes from freshwater to a terrestrial climax community V. Patterns of Population Growth A. population growth is affected by birth rate, death rate, and immigration and emigration B. J-curve or exponential growth – every generation increases in population size in an exponential manner – happens when there is a favorable new environment – cannot be maintained because of environmental limitations (diseases, resources, wastes, lack of space) C. S-curve – growth is exponential at first and then slows and levels off at the carrying capacity D. population dispersal patterns – spatial distribution of organisms 1. clumped (contagious) - most frequent type of distribution - indicating the existence of aggregations or groups in the population – flocks and herds of animals 2. random (haphazard) - implies that the individuals have been distributed by chance – free floating marine larvae 3. uniform - regularity of distance between and among the individuals of a population – trees in a forest VI. Reproductive Strategies and Population growth A. sexual reproduction – occurs in most complex multicellular organisms – helps create and maintain diversity in the gene pool of a population B. asexual reproduction – allow a population to grow very rapidly (1) benefit – reduced cost to produce organisms (2) cost – reduction of genetic variability (3) parthenogenesis – when females reproduce on their own – unfertilized egg becomes a new female – ex. bees C. Both asexual and sexual – asexual in the times of abundant resources and sexual when resources are limited D. Two different strategies that affect the number of offspring produced (1) r strategist - large number of young produced but not taken care of (2) k strategist - small number of young produced but taken care of (have a difficult time recovering from catastrophic decrease in population size E. survivorship curves 1. Type I – have a high survival rate early on in life and at middle age but death rates increase as age increases – humans 2. Type II – constant mortality rates – squirrels and birds 3. Type III – have a low survival rate early on in life, but once they survive they are able to live for a long period of time – produce lots of offspring at once - mollusks VII. Role of abiotic environment in population growth A. water – must regulate their water content and salt concentration inside and outside their cells B. sunlight (1) photic – water – area of the water that light penetrates (2) aphotic – no light – only heterotrophs and chemoautotrophic organisms C. oxygen supply – aquatic – utilize oxygen dissolved in the water – pollution lowers oxygen content and threatens aquatic life D. Substratum (soil or rock) (1) acidity (pH) – acid rain makes the soil pH too low for most plants (2) texture of soil and clay content – determine the amount of water the soil can hold (3) minerals – nitrates, phosphates, and other minerals determine the type of vegetation (4) humus quality – amount of decaying material VIII. Competion and the niche A. interspecific competion – between species – when two populations overlap in their niches – the more the niches overlap, the greater the competition B. Intraspecific competiton – between organisms of the same species IX. Marine Biomes A. intertidal zone – region exposed at low tide that undergoes variations in temp and dryness – algae, sponges, clams, snails, sea urchins, sea stars, crabs B. littoral zone – region on the continental shelf that contains the ocean area up to 600 feet deep – algae, crabs, crustacean, fish C. Pelagic Zone – typical of the open ocean – contain photic and aphotic zones – plankton, fish, sharks, whales, diatoms D. benthic zone – bottom regions of the ocean X. Humans and the Environment A. Humans alter the environment Increasing population puts strain on the environment B. Depleting Resources 1. Finite sources – there is only a set amount of the resources – once they are gone, they are gone – these are called nonrenewable – such as coal, oil and natural gas 2. Replaceable sources – these sources can be renewed over time – these are called renewable – such as corn, trees, water C. Pollution – anything added to the environment that can cause damage to any living thing 1. acid precipitation – burning fossil fuels releases sulfur oxides and nitrogen oxides that combine with water and form sulfuric acid and nitric acid – this washes nutrients out of the soil and affects aquatic organisms 2. Ozone Depletion - CFCs – destroy the ozone layer which helps to protect us from UV rays which cause cancer 3. greenhouse effect – burning of fossil fuels releases carbon dioxide which holds in heat and causes the temp. to rise - other greenhouse gases include methane and water 4. water pollution – can kill aquatic life or cause mutations – can also enter the food chain and increase in magnification – this is called biological magnification - can include lead, DDT, mercury, PCBs 5. Thermal pollution – water is used to cool industrial equipment – the hot dirty water is put directly back into the environment where it kills aquatic life 6. nuclear fuel – an energy source that does not pollute the air or water with toxic chemicals but they can cause thermal pollution and the radioactive wastes produced are a huge environmental problem 7. water usage – increased industrialization increases the use of water 8. smog – kind of air pollution that occurs when air pollutants react with sunlight 9. eutrophication – when fertilizer runoff goes into lakes and increases the amount of phosphorus the algae increases – as the algae dies bacteria increase which decreases the amount of dissolved oxygen causing the fish to die off which leads to death of the whole lake XI. Conservation of resources A. Using resources wisely 1. reduce – reduce our use of resources – for example turning off lights when not in use 2. Reuse – using an item over and over again or using it for purposes other than its original use – for example using your own cloth bag at the grocery store instead of using plastic 3. Recycle – take aluminum cans to be recycled into another material B. Renewable Resources – solar power, wind power, hydroelectric, geothermal and methane gas C. Reducing Pollution 1. water treatment plant 2. smoke stacks with scrubbers to remove particulates and sulfur dioxide 3. biological control of insects – hormones (pheromones), natural predators D. Protecting Biodiversity 1. endangered species – help protect habitat, reintroduction programs, and breeding programs