Bio Chapter 36
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Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Chapter 36: Ecosystems and Biomes The ecosystem Al communities need an original source of energy (generally the sun) They need a supply of nutrients and water (like nitrogen or phosphates) All organisms need to exchange gases with their environment (breathing) The sun’s energy makes a one-way trip through a community, ultimately transformed into heat Water and nutrients are cycled from Earth into organisms and then back into Earth Biotic: pertaining to living things Abiotic: pertaining to non-living things Ecosystem: a community of organisms and the physical environment where they interact Nutrient and Water Cycling in Ecosystems Abiotic factors in ecosystems fall into 2 categories: The resources that exist in the ecosystem, like water and nutrients The conditions in which an ecosystem exists, like its average temperature The cycling of ecosystem resources Remember an element is a substance that is “pure”; it cannot be broken down into something new by chemical means The 92 stable elements include familiar elements like gold or helium, but only 30 or so are vital to life these are called nutrients different nutrients are needed in different amounts biogeochemical cycling: the movement of water and nutrients back and forth between biotic and abiotic realms Carbon as one example of ecosystem cycling Think of Earth like a spaceship, it carries a fixed amount of resources with it Nothing much comes to Earth from the outside, and nothing leaves from Earth for the outside What we possess in terms of elements is all we will ever have Where do we have it? Ex. The build up of carbon dioxide in the atmosphere that causes global warming is increasing. This is still the fixed amount we have; it has just been transferred from one place on Earth to another From fossil fuels to the atmosphere Storage and transfer; these are fundamental concepts of biogeochemical cycing Ex. Plants take CO2 in photosynthesis they use it to make food and grow they decompose and the CO2 stored inside is released Note carbon only comes into the living world only through plants and other photosynthesizers (algae and some bacteria) Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important How much atmospheric CO2? CO2 is the living world’s medium of exchange for carbon Even though there is a lot of biomass (materials produced by living things) produced in the world, CO2 is only .035% of Earth’s atmospheric gasses The nitrogen cycle Like carbon, nitrogen is an element and cycles between biotic and abiotic domains Nitrogen makes up only a small portion of tissues in living things but is critical to life because it’s required for DNA, RNA, and all proteins How do we get it? All nitrogen that enters the living world is atmospheric nitrogen which is 78% of the atmosphere The problem is all nitrogen is formed in pairs of nitrogen atoms (N2) and have a great tendency to stay together rather than bind In result, plants have no direct access to it Nitrogen is received through bacteria Bacteria carry out the process of nitrogen fixation Nitrogen fixation: the conversion of atmospheric nitrogen into a form that can be taken and used by living things Bacterial fixation of nitrogen Basically the cycle is several types of nitrogen fixing bacteria take in atmospheric nitrogen and convert it into ammonia (NH3) This ammonia is then turned into two types of nitrogen containing compound that can assimilate (take up and use) These two nitrogen compounds are ammonia ion (NH4+) and nitrate (NO3-) Some of the nitrate that results from this process is used by another bacterium, denitrifying bacteria, which converts nitrate back to atmospheric nitrogen, completely the cycle Nitrogen as a Limiting Factor in food production Through most of our history, nitrogen was fixed solely by bacteria This sole source is a problem because nitrogen is critical to all plant growth Ex agricultural growth Lack of nitrogen is a limiting factor for food growth How energy flows through an ecosystem Producers, Consumers, and Trophic Levels Look at food and energy in terms of production and consumption Producers: any organism that makes its own food Consumers: an organism that eats other organisms rather than produce its own food Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Trophic level: a position in an ecosystem’s food chain or web with each level defined by a transfer of energy between one kind of organism to another Plants and other photosynthesizers are an ecosystems producers while the organisms that eat plants are one kind of consumer There are consumers of consumers: primary, secondary, and tertiary Ex. Zebras (primary consumer) consume plants (producers) and are then consumed by lions (secondary consumer) This is the concept of trophic levels (food chains) A list of trophic levels through four steps: First trophic level: producers- photosynthesizers Second trophic level: primary consumers – plant predators (herbivores) Third trophic level: secondary consumers – herbivore predators (carnivores) Fourth trophic level: tertiary consumers – consumers that feed on secondary consumers (carnivores) The sun’s energy is trapped in the first trophic level Note trophic levels are set in the same order We have to have primary consumers to have secondary consumers; sharks cannot exist on algae Herbivores: an animal that only eats plants or algae Carnivores: an animal that only eats meat Omnivores: an animal that eats both plants and algae and meat Not all organisms are restricted to one trophic level Most humans are primary, secondary, and tertiary consumers Detritivores Detritivore: consumers that feed on detritus (a collection of debris) In ecology, detritus is the remains of a dead organism or cast off material from a living organism Ex. A fallen branch from a living tree A worm or dung beetle would be considered a detritivore There’s also a special kind of detritivore, a decomposer Decomposer: an organism that eats dead or cast off organic material and breaks it down into its inorganic components that can be recycled through the ecosystem Think of inorganic here as building blocks Technically it means a compound that does not contain carbon bound covalently to hydrogen The most important decomposer are fungi and bacteria Nature does not produce anything it will not eventually decompose and recycle Biodegradable: capable of being decomposed by living organisms Energy flow through trophic levels Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important All natural substance may be recycled in the ecosystem, but this is not true for energy which is just passing through on its way to becoming heat Common questions are: How much of the sun’s energy does the living world collect in the first place, and how much of the collected energy makes it through each successive trophic level Energy flow model: a conceptualization of ecosystems as units in which energy is first capture by a given organism and then transferred to other organisms This concept was coined by the ecologist Raymond Lindeman in the 1940s Part of the main reason for Lindeman’s research was to figure out why big, fierce animals are rare Rare in the sense that we see things like bugs, plants, and birds all the time, but we don’t wake up to lions or bears in our yards The energy flow model answered this and other questions on ecological relationships It’s because energy is the “currency” of the natural world It usually be measured in kilocalories Ex. If we know a field mous must use 68% of the kilocalories it consumes just to function, but a weasel must use 93% of it’s kilocalories, that gives us reasonable basis for comparison between the two Kilocalories: the amount of heat it takes to raise 1 kilo of water 1 degree Celsius The capture of energy by plants 2% of the sun’s energy that falls around plants is taken for photosynthesis This emphasizes the difference between the energy that comes to an organism and what the organism does with that energy gross primary production: the amount of material a plant produces as a result of photosynthesis Remember the initial product of photosynthesis is a sugar that serves as a building block for all the material in the plant Every time a molecule of this sugar is produced in photosynthesis the plant has added to its gross primary production Plants don’t get to retain all the material they produce because plants incur energy costs just to stay alive It costs energy to photosynthesize, move sap, and also energy is lost to heat After those costs are subtracted, the plant is left with its net primary production Net primary production: the amount of material a plant accumulates as a result of photosynthesis Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important This is the material that serves to build the plant up – it’s stems, leaves, and roots Between 30-85% of the solar energy renewed by a plant is transferred into net primary production Basically at the least 30% of the solar energy a plant assimilates is transferred into material that is even potentially available to the next trophic level Earth’s Physical Environment Earth lives within an environment called the atmosphere Atmosphere: the layer of gases surrounding the planet It’s important to realize the difference between Earth’s atmosphere and space There’s something to Earth’s atmosphere (a mix of gases) and space is literally space theres almost nothing to it There are several layers to Earth’s atmosphere, but we will only focus on 2 The lowest layer is the troposphere Starts at sea level Goes up to 7.4 miles Nitrogen and oxygen make up 91% of it Other gases exist in small amounts like carbon, argon, and methane The layer after that is the stratosphere In it is a gas that reaches its greatest density about 13-21 miles above sea level Remember the oxygen we breathe comes in the form of two oxygen molecules bonded together (O2) when ultraviolet light strikes O2 in the stratosphere, it can convert into 3 oxygen molecules (O3), this gas is known as ozone the ozone layer ultimately came to protect life by blocking 99% of UV (ultraviolet) radiation the blocking allowed large life forms to move from water to land billions of years ago UV radiation can bring about cancer and immune system problems and can also damage vegetation The issue of ozone depletion The ozone layer is fragile Human made chemical compounds have the effect of destroying stratospheric ozone In 1974 atmospheric chemists Sherwood Rowland and Mario Molina discovered compounds called chlorofluorocarbons (CFCs) posed a direct threat to the ozone CFCs are not the only component that affect the ozone, others include: Methyl bromide; found in pesticides and herbicides Bromine; found in fire extinguisher chemicals Global Warming Warming and its causes Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important If you remember from earlier, one cause is the release of heat trapping gases (CO2) from fossil fuels we burn like coal and oil Another cause is from things like cattle grazing and rice growing releasing methane, another heat trapping gas A third cause is deforestation which either puts CO2 directly into the atmosphere or results in CO2 being taken out because the dead trees can no longer photosynthesize Earth’s Climate Why some areas are wet and some are dry, some are hot and some are cold Earth’s orbit is tilted at an angle of 23.5 degrees against the sun The tilt dictates a lot about Earth’s climate The circulation of some of the atmosphere and its relation to rain Variation in temperature is the most important factor in the circulation of Earth’s atmosphere Near the equator Earth gets more warmth and the warm air rises Warm air can also retain more moisture than cold air Think of when you see bead of “sweat” that form on the outside of a cold glass in the summer Moisture-laden warm air comes into cooler air immediately around the glass when cooled the air cannot hold as much moisture and releases it onto the glass this same thing happens when warm air rises on both sides of the equator due to the heat of the tropics, air is rising in quantity from the tropical oceans because this air is warm it carries a lot of moisture the air cools as it rises and then drops much of the moisture on the tropics, which is why they’re so wet the volume of air is now drier and cooler and moving toward the poles in both direction from the equator at 30˚N and 30˚S of the equator it descends warming as it drops and absorbing the moisture from the land the land will be dry at these latitudes because this is where the dry, hot air descends the air that has descended now flows in two directions from the 30˚ points at a fairly low altitude now, the air eventually picks up moisture, rises, and deposits its moisture, this time at 60˚N these same events happen at the same places in the Southern Hemisphere all this rising and falling is a set of interrelated “circulation cells” of moving air each existing all the way around the planet Mountain chains affect precipitation patterns Mountain ranges force air upwards, and this air also cools as it rises, dropping it’s moisture on the windward side of the range Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Then the air descends on the opposite side of the range, only this time it is dry air and is this picking up moisture from the ground rather than depositing it An example of this “rain shadow” effect can be seen in Southern Oregon, when the west side of the cascades are lush and green all year round while the basin below the eastern slopes is a desert I as altitude increases temperature drops The changes in climate as you move from flatland to mountain peak are similar to the changes that happen from the equator to the poles Climate: average weather conditions Earth’s biomes Biomes: large terrestrial regions of the Earth that have similar climate and hence similar vegetative formations The world can be divided into any number of biomes but six are recognized as the minimum Tundra Taiga Temperate deciduous forest Temperate grassland Tropical rainforest Polar ice caps and mountains are often recognized as separate biomes along with the savanna (a grassland variation) and chaparral (shrub dominated vegetation formation around the Mediterranean climate) The fact that two biomes are the same type does not mean they’re identical Two areas the same in climate can have significantly different life forms Tundra Along with polar ice tundra is the biome of the far north, stretching in a vast mostly frozen ring around The tundra is very inaccessible and takes up a fourth of Earth’s land surface The word tundra comes from a Finnish word that means “treeless plain” Tundra vegetation is usually small shrubs, mosses, grasses, etc. It gets 10 inches of rain a year which almost makes it a desert, but it’s marshy in the summer When the rain falls it doesn’t soak into the ground because the ground is frozen a quarter of a mile down This is permafrost: permanent ice which acts as a boundary beyond which neither water nor roots can go Because of permafrost rain will just sit on the ground making bogs and small lakes low lying tundra vegetation makes the of a short growing season (as little as 50 days) by producing a year’s worth of food through photo in only a few weeks Taiga Taiga: (boreal northern forests) has huge coniferous trees everywhere Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important It’s still dry and cold and has a short growing season but it is less severe than the tundra taiga is almost solely in the northern hemisphere this is because there is little land in the southern hemisphere at the latitude of these biomes taiga is a model of species uniformity because it only ha a few types of trees (spruce, fir, and pine) that are present in great numbers supports a lot of animals Temperate Deciduous forest These forests are forests of maple, beech, oak, and hickory Deciduous refers to trees that exhibit a pattern of loss of leaves in the gall and regrowth of them in the spring This biome is common throughout the US These forests aren’t as dense as taiga forests Woody and herbaceous plants will spring up on the floor of the forest Temperate forests grow where there is a lot of water (30-78 inches a year) Note while the tundra has no reptiles or amphibians and taiga only has a few, temperate forests are wet and warm enough to support a variety of both Temperate Grasslands We call them prairies Often lie between deserts and forests Grasslands get 10-29 inches of rain/year No trees but a sea of grass that could grow up to 10 ft Prairie soil is actually some of the most fertile on Earth It’s pretty much gone now because of agriculture Tropical savanna: a type of tropical grassland characterized by seasonal drought, small changes in generally warm temperature, and stands of naturally occurring trees African savanna Chaparral A biome dominated by evergreen shrub vegetation that is dotted with pine and scrub oak trees Found in Mediterranean climate Always on the west coast of a landmass Deserts Deserts: biomes where rainfall is less than 10 inches a year and water evaporation rates are high relative to rainfall Not defined by temperature There are temperate deserts (Mojave desert in California), cold deserts (Gobi in China), and hot deserts (Sahara in Africa) 20 major deserts cover 30% of Earth’s land surface Most of the moisture a desert gets will come in just a few days during the year Desert life has adapted to one way: collect water and conserve it Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Tropical rainforests Important for two main reasons They are the most productive biome type in the world (along with coral reefs and algae beds) meaning they produce a lot of biomass No other ecosystem has this amount of species diversity 300 species of trees 1700 types of beetle Half of all identified plants and animals are here Only 7% of Earth’s land mass 78-175 inches of rainfall Has a large group of detritivores so organic material is decomposed immediately This means soil never gets built up; it is nutrient poor and often acidic The nutrients bypass the soil Goes from plant to detritivore back to plant Aquatic Ecosystem Marine Ecosystem The ocean’s coastal zone extends from the point on the shore where the ocean waves reach high tide to a point out at sea where an ocean floor formation called the continental shelf drops Beyond this point is the open sea Then there’s the intertidal zone an area bordered on one side by the ocean’s low tide mark and on the other side by its high tide mark Pelagic zone: all water from the ocean’s surface to the floor Benthic zone: the ocean’s floor From sea level down to a depth of 330 feet, the sun can reach enough to start photosynthesis That zone of photosynthesis is called the photic zone Each of these zone mark off an area that is meaningful to life Intertidal zone Extremely productive The ocean waves bring in nutrients and carry away waste Exposes more of the surface area of photosynthesis to sunlight Ocean life is more productive in its shallower depths Once past the shelf, it’s almost as barren as a desert This is because sunlight can’t reach past 330 feet; the ocean is 1.8 miles down on average Life at deeper parts of the ocean depend on organic particles, “marine snow”, that come from above The poles In the pelagic zone there are relatively more ocean life towards the poles, this concentration decreases towards the equator This is the opposite of life on land Phytoplankton: floating microscopic photosynthesizers Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important These are the base producers for all these organisms They are consumed by tiny floating things called zooplankton Krill eat zooplankton and are a food source for animals like seals and whales Coral reefs Coral reefs: warm water ocean structures composed of the remains of coral animals Each animal is called a polyp and is a relative of sea anemones Coral polyps secret calcium carbonate (limestone), a practice they share with a type of symbiotic red algae inside them The limestone forms an external skeleton for the corals When the coral dies, the limestone remains Reefs are basically stacked remains of generations of polyp and algae Most reefs are 5,000-8,000 years old Create a rich habitat for 25% of species while taking up only 2% of the ocean floor Freshwater system Freshwater ecosystems (inland lakes, rivers, etc.) cover 2.1% of Earth’s surface Lakes and the like can be divided into bio zones like oceans The most productive zone in a lake is the shallow water along its edge, the littoral zone Littoral zone: the point at which the water is so deep that rooted plants can no longer grow Photic zone: the point in a freshwater system where sunlight cannot reach Profundal zone: the point where photosynthesis cannot occur Nutrients in lakes Lakes can be naturally eutrophic (nutrient rich) or oligotrophic (nutrient poor) Oligotrophic lakes are clear and deep Eutrophic lakes have a lot of algal cover Nutrient enrichment can be natural or man-made Man-made = artificial eutrophication Usually done to increase the yield of fish from a lake or pond However an overabundance of nutrients like nitrogen or phosphorus bring an overabundance of algae This means dead algae will fall to the floor and decomposing bacteria will flourish This leads to them using all the oxygen and suffocating the fish Estuaries and wetlands Estuary: an area where a stream or river flows into an ocean Very productive like tropical forests and reefs This is because of the constant movement of water Ocean tides and river flow constantly stir nutrients Key: Light Blue = main idea Purple = important parts of the main idea Green = examples Orange = key terms Pink = the definition of the key term Red = especially important Wetlands: lands that are wet for at least half of the year Swamps, bogs, marshes Majority are freshwater and inland but can be salt or freshwater Serve as vital habitat for birds Biosphere: collection of all the world’s ecosystems; portion of Earth that supports life