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Unit 2, Chapter 4 Ecology, Ecosystems, and Food Webs
4-1 Ecology and Life • Ecology- study of relationships between organisms and their environment • Ecology examines how organisms interact with their nonliving (abiotic) environment such as sunlight, temperature, moisture, and vital nutrients • Biotic interaction among organisms, populations, communities, ecosystems, and the ecosphere
Characteristics of Life • Organisms are composed of cells that have highly organized internal structure; • Cells of organisms contain deoxyribonucleic acid (DNA), which form the basis of heredity; • Organisms capture & transform matter & energy from their environment to supply needs for growth, survival, & reproduction; • Organisms maintain favorable internal conditions, despite changes in their environment, through homeostasis; • Organisms perpetuate themselves through reproduction; • Organisms adapt to changes in environmental conditions through evolution.
Organisms organism: any form of life. organisms are classified into species. species: groups of organisms that resemble each other, &, in cases of sexually reproducing organisms, can potentially interbreed. estimates of 5 to 100 million species, most are insects & microorganisms; so far only about 1.8 million named; each species result of long evolutionary history. wild species: population that exists in its natural habitat (= native species). domesticated or introduced species: population introduced by humans (= non–native species).
Distinction between Species • Wild species- one that exists as a population of individuals in a natural habitat, ideally similar to the one in which its ancestors evolved • Domesticated species- animals such as cows, sheep, food crops, animals in zoos
Vocabulary • Population • Group of interacting individuals of the same species that occupy a specific area at the same time • Genetic Diversity • Populations that are dynamic groups that change in size, age distribution, density, and genetic composition as a result of changes in environmental conditions
Habitat • Place where a population or individual organism naturally lives • Community • Complex interacting network of plants, animals, and microorganisms • Ecosystem • Community of different species interacting with one another and with their nonliving environment of matter and energy • Ecosphere or Biosphere • All earth's ecosystems
What is Life? • All life shares a set of basic characteristics • Made of cells that have highly organized internal structure and functions • Characteristic types of deoxyribonucleic acid (DNA) molecules in each cell
Living Organisms • Capture and transform matter and energy from their environment to supply their needs for survival, growth, and reproduction • Maintain favorable internal conditions, despite changes in their external environment through homeostasis, if not overstressed
Living Organisms • Perpetuate themselves through reproduction • Adapt to changes in environmental conditions through the process of evolution
Biomes & Life Zones biome: large regions characterized by a distinct climate & specific life–forms, especially vegetation, adapted to the region. major biomes: temperate grassland, temperate deciduous forest, desert, tropical rain forest, tropical deciduous forest, tropical savannah, coniferous forest, tundra aquatic life zone: major marine or freshwater areas containing numerous ecosystems. major aquatic life zones: lakes, streams, estuaries, coastlines, coral reefs, & the deep ocean
Biomes– Large regions characterized by distinct climate, and specific life-forms Climate– Long-term weather; main factor determining what type of life will be in a certain area.
The Earth contains several layers or concentric spheres • Lithosphere • Crust and upper mantle • Crust • Outermost, thin silicate zone, eight elements make up 98.5% of the weight of the earth’s crust 4-2 Geosphere
Core • Innermost zone, mostly iron, solid inner part, surrounded by a liquid core of molten material • Inner Core is hotter than surface of the Sun • Mantle • Surrounded by a thick, solid zone, largest zone, rich with iron, silicon, oxygen, and magnesium, very hot 4-2 Geosphere
4-2 Atmosphere • Thin envelope of air around the planet • Troposphere • extends about 17 kilometers above sea level, contains nitrogen (78%), oxygen(21%), and is where weather occurs • Stratosphere • 17-48 kilometers above sea level, lower portions contains enough ozone (O3) to filter out most of the sun’s ultraviolet radiation
4-2 Hydrosphere Consists of the earth’s liquid water, ice, and water vapor in the atmosphere
What Sustains Life on Earth? • Life on the earth depends on three interconnected factors • One-way flow of high-quality energy from the sun • Cycling of matter or nutrients (all atoms, ions, or molecules needed for survival by living organisms), through all parts of the ecosphere • Gravity, which allows the planet to hold onto its atmosphere and causes the downward movement of chemicals in the matter cycles
Sun • Fireball of hydrogen (72%) and helium (28%) • Nuclear fusion • Sun has existed for 6 billion years • Sun will stay for another 6.5 billion years • Visible light that reaches troposphere is the ultraviolet ray which is not absorbed in ozone
Solar Energy • 72% of solar energy warms the lands • 0.023% of solar energy is captured by green plants and bacteria • Powers the cycling of matter and weather system • Distributes heat and fresh water
Energy Flow The ultimate source of energy in most ecosystems is the sun.
Energy Flow & Nutrient Cycling Life on Earth depends upon one–way flow of high–quality energy from sun & cycling of crucial elements.
Type of Nutrients • nutrient: any atom, ion, or molecule an organism needs to live, grow, or reproduce. • macronutrients needed in relatively large amountse.g., C, O, H, N, P, S, K, Ca, Mg, Fe • micronutrients needed in relatively small amountse.g., Na, Zn, Cu, Cl, I • nutrient cycles (= biogeochemical cycles) involve continual flow of nutrients from nonliving (air, water, soil, rock) to living organisms (biota) & back again. • nutrient cycles driven directly or indirectly by solar radiation & gravity. • Major cycles: hydrologic (water), carbon, oxygen, nitrogen, phosphorus, & sulfur.
Open vs. Closed Systems • Closed System: a system in which energy, but not matter, is exchanged between the system & its environment. • earth is a closed system, in that matter is neither lost nor gained (except negligible cosmic dust & meteorites) while energy flows through; • Open System: a system in which both energy & matter are exchanged between the system & its environment. • organisms are open systems because both matter & energy are exchanged with the environment.
Ecosphere Separation • The Ecosphere and it’s ecosystem can be separated into two parts • Abiotic- nonliving, components • Ex: air, water, solar energy • Physical and chemical factors that influence living organisms • Biotic- living, components • Ex: plants and animals
Range of Tolerance The survival, growth, & reproduction of organisms is determined, in part, by maximum & minimum tolerance limits for physical conditions such as temperature. Fig. 4–12
Limiting Factors limiting factor: an environmental factor that is more important than other factors in regulating survival, growth, or reproduction. law of tolerance: the existence, abundance, & distribution of a species in an ecosystem is determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species. limiting factor principle: too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.
Dissolved Oxygen Content • Amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure. • Limiting factor of aquatic ecosystem
Salinity • amount of salt dissolved in given volume of water
Major Living Components • Two main categories: • 1) producers (also called autotrophs = "self–feeders") make their own food from compounds obtained in the environment. • most capture sunlight to make sugars & other organic compounds in a process called photosynthesis, e.g., green plants. • a few, mostly bacteria, convert simple compounds into complex nutrient compounds without sunlight, e.g., bacteria of thermal vents that use hydrogen sulfide (H2S) & carbon dioxide. • 2) consumers (also called heterotrophs "other–feeders") get their energy & nutrients by feeding on other organisms or their remains. • Includes herbivores, carnivores, decomposers, etc.
Photosynthesis & Respiration • photosynthesis: complex chemical reaction in plants, in which solar radiation is captured by chlorophyll (& other pigments) & used to combine carbon dioxide & water to produce carbohydrates (e.g., glucose), other organic compounds, & oxygen. • carbon dioxide + water + solar energy glucose + oxygen • 6 CO2 + 6 H2O + solar energy C6H12O6+ O2 • aerobic respiration: complex process that occurs in the cells of organisms, in which organic molecules (e.g., glucose) are combined with oxygen to produce carbon dioxide, water, & energy. • glucose + oxygen carbon dioxide + water + energy • C6H12O6+ O2 6 CO2 + 6 H2O + energy
Chemosynthesis- • Bacteria can convert simple compounds from their environment into more complex nutrient compound without sunlight • Ex: becomes consumed by tubeworms, clams, crabs • Bacteria can survive in great amount of heat
Consumers • major kinds of consumers (= heterotrophs) • primary consumers: (=herbivores) feed directly on producers; • secondary consumers: (=carnivores) feed on primary consumers; • tertiary consumers: feed only on carnivores; • omnivores: consumers that feed on both plants & animals; • scavengers: feed on dead organisms; • decomposers: consumers that complete the breakdown & recycling of organic materials from the remains & wastes of other organisms; • detritivores: feed on detritus (partially decomposed organic matter, such as leaf litter & animal dung).
Consumers or Heterotrophs • Obtain energy and nutrients by feeding on other organisms or their remains
Consumers • Herbivores (plant-eaters) or primary consumers • Feed directly on producers • Deer, goats, rabbits http://www.holidays.net/easter/bunny1.htm
Consumers • Carnivores (meat eater) or secondary consumers • Feed only on primary consumer • Lion, Tiger
Consumers • Tertiary (higher-level) consumer • Feed only on other carnivores • Wolf
Consumers • Omnivores- consumers that eat both plants and animals • Ex: pigs, humans, bears
Consumers • Scavengers- feed on dead organisms • Vultures, flies, crows, shark
Detritus Feeders vs. Decomposers Fig. 4–13
Consumers • Detritivores- live off detritus • Detritus parts of dead organisms and wastes of living organisms. • Detritus feeders- extract nutrients from partly decomposed organic matter plant debris, and animal dung.
Consumers • Decomposers - Fungi and bacteria break down and recycle organic materials from organisms’ wastes and from dead organisms • Food sources for worms and insects • Biodegradable - can be broken down by decomposers
Respiration • Aerobic Respiration • Uses oxygen to convert organic nutrients back into carbon dioxide and water • Glucose + oxygen Carbon dioxide + water + energy • Anaerobic Respiration or Fermentation • Breakdown of glucose in absence of oxygen
Summary of Ecosystem Structure Fig. 4–15
Food Chain • Food Chain-Series of organisms in which each eats or decomposes the preceding one • Decomposers complete the cycle of matter by breaking down organic waste, dead animal. Plant litter and garbage. • Whether dead or alive organisms are potential (standard) sources of food for other organisms.
Second Law of Energy • Organisms need high quality chemical energy to move, grow and reproduce, and this energy is converted into low-quality heat that flows into environment • Trophic levels or feeding levels- Producer is a first trophic level, primary consumer is second trophic level, secondary consumer is third. • Decomposers process detritus from all trophic levels.
Food Webs & Energy Flow Food chains involve a sequence of organisms, each of which is the food for the next. Fig. 4–16
Food Web • Complex network of interconnected food chains • Food web and chains • One-way flow of energy • Cycling of nutrients through ecosystem