Unit 1: The Living World: Ecosystems

Notes

Resource Availability

• Resource availability is one of the main factors determining the ecological dynamics of populations or species.

Species Relation

General notes

• Biotic: interactions with other organisms (intra/interspecific competition, predation, parasitism, or demographic changes)

• Abiotic: physical and climatic factors

• Population: groups of organisms of the same species

• Community: populations of different species occupy the same geographic area

• Species’ niche: total sum of a species’ use of a/biotic resources in env

• Where the species lives, what it eats, and other resources they utilize in the ecosys

• Habitat: area/env where organism lives/occurs

Competition

• When two individuals are competing for resources in the env

• Intraspecific: two individuals that are competing are the same species

• Interspecific: two individuals that are competing are the diff species

• Resources: food, air, shelter, sunlight, etc.

• Competitive exclusion

• Better adapted species wins when two different species in a region compete

• Gause’s principle: no two species can occupy the same niche at the same time; the species that is less fit will relocate, die out, or occupy a smaller niche

• Realized niche: smaller niche in the absence of competition

• Fundamental niche: niche with no competition

• Resource partitioning: different species use slightly different parts of the habitat but rely on the same resource

Interspecies interaction

• Competition: see above

• Predation: one species feeds on another

• Drives changes in population size

• Symbiotic: close, prolonged association b/t 2+ different organisms of different species that may benefit each other

• Mutualism: both species benefit

• Commensalism: one organism benefits while the other is neither helped nor hurt

• Parasitism: one species is harmed and the other benefits

Ecosystems

• Biomes: ecosys based on land

• Separated into biomes based on their climate (temp, precipitation)

• Aquatic life zones: ecosys based in aqueous env

• Categorized primarily by the salinity of their water (freshwater and saltwater ecosys fall into separate categories)

• Biomes blend into each other; they don’t have distinct boundaries

• Ecotones: transitional area where two ecosystems meet

• Ecozones: smaller regions within ecosystem that share similar physical features

• Law of tolerance

• Degree to which living organisms are capable of tolerating changes in their environment

• Living organisms exhibit a range of tolerance; individuals within a population tolerate changes to their environment differently

• Basis of natural selection, drives evolution

• Law of minimum: living organisms will continue to live, consuming available materials until the supply of these materials is exhausted

Energy

• Limiting factor: factor that controls a population’s growth

• Energy that drives biogeochemical cycles (in the biosphere) comes primarily from: (1) the sun. (2) heat energy from the mantle and core of the earth

• Law of Conservation of Matter: matter can neither be created nor destroyed

• Net Primary Productivity (NPP): amount of energy plants pass on to the community of herbivores in an ecosystem

• NPP = GPP - respiration

• Units: kcal/m2/yr

• Gross Primary Productivity (GPP): amount of sugar that the plants produce in photosynthesis; rate at which the producers are converting solar energy to chemical energy

Food chains/food webs

Producers

• Aka autotrophs

• Organisms capable of converting radiant energy or chemical energy into carbohydrates

• Plants and algae → photosynthesis

• H20 + CO2 + solar eng → CH2O + O2

• Producers in non-oxygen environments make food through CHEMOSYNTHESIS

• Carried about specialized bacteria called chemotrophs (some found in hydrothermal vents depp in the ocean)

• O2 + H2S + O2 + eng → CH2O + S + O2

Consumers

• Aka heterotrophs

• Organisms that obtain food energy from secondary sources by eating plant of animal matter

• Types of consumers

• Primary consumers: herbivores → consume only producers (plants and algae)

• Secondary consumers: consumes primary consumer

• Tertiary consumer: consumes secondary consumer

• Detritivores: consume nonliving organic matter (dead animals or fallen leaves)

• Decomposers: bacteria or fungi that absorb nutrients from nonliving organic matter such as plant material, wastes of living organisms, corpses → convert materials into inorganic forms

Food chains

• 10% rule: only 10% of energy from one trophic level is passed to the next (most is lost as heat; used for metabolism, respiration, digestion, running away)

• Bioaccumulation: accumulation of a substance in the tissues of a living organism

• Food webs represent feeding relationships in ecosystems more realistically

Biogeochemical cycles

• Involves living organisms, geological formation, and chemical substances

• Reservoir: place where a large quantity of a nutrient sits for a long period of time (ex. water cycle: ocean)

• Exchange pool: site where nutrient sits for only a short period of time; opposite of reservoir (ex. water cycle: cloud)

• Residency time: amount of time a nutrient spends in a reservoir/exchange pool (ex. water cycle: cloud- few days; ocean- thousands of years)

Water cycle

• Precipitation: water exists in atmo as gas → condenses from gaseous state to form liquid/solid → dense enough to fall to the earth bc of gravity

• Travel below ground to become GROUNDWATER

• Travel across land’s surface as RUNOFF and enter a drainage sys (streams/rivers) → deposit into body of water (lakes/oceans)

• Reservoirs: lake, ocean, snow, ice

• Water is cycled through LIVING SYSTEMS

• Ex. plants consume water (and CO2) from photosynthesis → produce carbohydrates

• Exchange pools: bc all living organisms are primarily made up of water → plants are exchange pools for water

• Evaporation: water returned to atmosphere from earth’s surface and living organisms

• Animals RESPIRE and release water vapor and additional gases to the atmosphere

• Plants TRANSPIRE and release large amounts of water into the air

• Incredibly large amounts of water continually evaporate from surfaces of lakes and oceans

Carbon cycle

• Respiration: animals and plants breathe in oxygen and give off CO2

• Photosynthesis: plants take in CO2, h4o, and energy from the sun to produce carbohydrates

• Exchange pools: living things are carbon exchange pools

• Decay of organic matter → atmosphere

• Plants are eaten by animal consumers → carbon locked in the plant carbohydrates passes to other organisms (continues food chain) → organisms die → bodies decomposed through bacteria and fungi in soil → release CO2 into atmosphere

• Fossil fuels

• Bodies of organisms buried → subjected to conditions of extreme heat and extreme pressure → organic matter eventually becomes oil, coal, gas (fossil fuels)

• When fossil fuels burned/combusted, CO2 is released into the atmosphere

• Volcanic action → atmosphere

• Reservoirs of carbon

• Oceans: CO2 is very soluble in water

• Rockes: carbonate rocks contain CO2 in the form of calcium carbonate

• Fossil fuels

Nitrogen cycle

• Atmosphere is made up of 78% N2 and 21% O2

• Most abundant element in the atmosphere

• However, atmospheric nitrogen is not in the form that can be used directly by most organisms

• Steps

• (1) nitrogen fixation

• Nitrogen must be in the form of ammonia (NH3) or nitrates (NO3-) to be used by living organisms

• Nitrogen can be fixed into NH3 or NO3- by lightning storms or certain soil bacteria

• Fixing: process that allows nitrogen to be made biologically available (like how photosynthesis makes carbon biologically available)

• Ex. Rhizobium: important nitrogen fixing soil bacteria

• Possible solution? Insert genes for nitrogen fixation into crop plants (ex. corn); decramount of fertilizer

• (2) nitrification

• Soil bacteria converts ammonium (NH4+) into one of the forms that can be used by plants, nitrate (NO3)

• (3) assimilation

• Plants absorb ammonium (NH3), ammonia ions (NH4+), and nitrate ions (NO3-) through their roots

• Heterotrophs obtain nitrogen when they consume plants’ proteins and nucleic acids

• (4) ammonification

• Decomposing bacteria convert dead organisms and other waste to ammonia (NH3) or ammonium ions (NH4+)

• Reused by plants

• (5) denitrification

• Specialized bacteria (mostly anaerobic bacteria) convert ammonia back into nitrites and nitrates and then into nitrogen gas (N2) and nitrous oxide gas (N2O)

• Gases then rise to the atmosphere

Phosphorus cycle

• Phosphorus doesn't exist in the atmosphere outside of dust particles

• Necessary for living organisms → major component of nucleic acids and other biological molecules

• Found in soil, rock, sediments

• Phosphorus is released from these rock forms through chemical weathering

• Usually released in the form of phosphate (PO43-) → soluble and can be absorbed from soil by plants

• Phosphorus is a limiting factor for plant growth

• Plants that have little phosphorus are stunted

• Lots of farmers like using phosphate fertilizers to help aid growth

• Phosphates that enter the water table and travel to the oceans can eventually be incorporated into rocks in the ocean floor

• Through geological process, ocean mixing, and upwelling → rocks from the seafloor rise up so it can once again enter the TERRESTRIAL CYCLE

• Humans

• Mining phosphorus rich rocks in order to produce fertilizers

• Fertilizes easily leach into groundwater and flow into aquatic ecosystems → eutrophication

• Eutrophication: body of water receives excess nutrients

• Abundance of nutrients causes overgrowth of algae and depletes the water of oxygen

Sulfur cycle

• Sulfur makes up proteins and vitamins → organisms need sulfur in diets

• Plants absorb sulfur when dissolved in water → take it up their roots when it’s dissolved in groundwater

• Animals obtain sulfur by consuming plants

• Sulfur is in rocks, salts, buried deep in the ocean in oceanic sediments, atmosphere

• Enters atmosphere: volcanic eruptions, certain bacterial functions, decay of organisms

• Humans: industrial process that produce sulfur dioxide (SO2) and hydrogen sulfide (H2S) gases

Freshwater

• Water that contains minimal quantities of dissolved salts (esp. sodium chloride NaCl)

• All freshwater comes from precipitation of atmospheric water vapor → reaches inland lakes, rivers, and groundwater bodies directly (or after melting of snow or ice)

• Water that doesn’t move through soil to become groundwater moves along the earth’s surface via gravity and forms small streams → forms larger streams → streams continues to increase to a river → river flows into ocean

• Watershed: land area that drains into a particular stream

• Streams carry sediment and other dissolved substances (small amounts of O2); turbulent waters are esp. laden with dissolved O2 and CO2 such as those found at the source of a stream

• Rule: the more turbulent the water, the more dissolved gases it will contain

• Moving water doesn't move in a straight line, it follows the lowest topographical path and the path of the least resistance

• Deltas: landform where rivers meet the ocean

• Rivers drop most of their sedimentary load as they meet the ocean because their velocity decreases significantly at deltas

• Estuaries: sites where the arm of the sea extends inland to meet the mouth of a river

• Rich with many different types of plant and animal species

• Freshwater in these areas usually have a high concentration of nutrients and sediments

• Water is quite shallow, fairly warm, biotic factors receive sig amounts of sunlight

• Subcategories: salt water marshes, mangrove forests, inlets, bays, river mouths

• Wetlands: ecologically diverse ecosystems along the shores of fresh bodies of waters

• Types: marshes, swamps, bogs, prairie potholes, flood plains

Vertical stratification

• In all natural bodies of water, there exist layers of water that vary significantly in their temperature, O2 content, nutrient levels (affected by season and other disturbances)

• Epilimnion: uppermost layer, thus most oxygenated

• Hypolimnion: lower, colder and denser layer

• Thermocline: demarcation line between epilimnion and hypolimnion where the temperature shifts dramatically

• Zones

• Littoral zone

• Very shallow water at the shoreline

• Plants and animals that reside here receive abundant sunlight

• Rooted plants stop growing at the end of this zone

• Limnetic zone

• Surface of open water

• Extends to the depth that sunlight can penetrate

• Organisms here are short-lived and rely on sunlight to carry out photosynthesis

• Profundal zone

• Water is too deep for sunlight to penetrate

• Aphotic zone (a zone that light cannot reach)

• Photosynthesizing plants and animals can’t live here

• Benthic zone

• Deepest layer in body of water

• Very low temperatures and low oxygen levels

Barrier islands

• Certain landforms that lie off coastal shores

• Created by buildup of deposited sediments → boundaries constantly shifting as water moves around them

• Usually the first hit by offshore storms → important buffers for the shoreline behind them

• Coral reef

• Barrier island in tropical waters

• Not formed from deposited sediments, but from community of living things

• Cnidarians that secrete a hard calciferous shell create coral reefs

• Shells provide home and shelter for many diverse species

• Extremely delicate → very vulnerable to physical stresses, changes in light intensity, water temperature, ocean depth, ocean pH

Oceans

• Zones

• Coastal zone

• Ocean water closest to land

• Between shore and end of continental shelf

• Euphotic zone

• Photic, upper layers of water

• Warmest region of ocean water → highest levels of dissolved oxygen

• Bathyal zone

• Middle region

• Zone receives insufficient light for photosynthesis

• Colder than euphotic zone

• Abyssal zone

• Deepest region of ocean

• Extremely cold temperatures and very low levels of dissolved oxygen

• Very high levels of nutrients (decaying plant and animal matter sinds down from zones above)

• Upwellings

• Freshwater and saltwater bodies experience a seasonal movement of water from the cold and nutrient rich bottom to the surface

• Provides new nutrient supply for the growth of living organisms in the photic regions

• Followed by an immediate exponential growth in the population of organisms in these zones (esp. single cell algae) which may form algal blooms

• Algae can produce toxins that may kill fish and poison the bed of filter feeders (ex. oysters and mussels)

• Ex. red tide: toxic algal bloom caused by prolif of dinoflagellates

• Water is DENSEST at 4℃

• In non-tropical regions of the earth after spring ice melt, water-surface temperature of lakes and ponds rise from 0℃ to 4℃ → dense surface water will sink to the bottom of the lake/pond → this displaces water at the bottom of the lake/pond to the surface → overturn brings oxygen to the bottom and nutrients to the top of the lake/pond and occurs during the spring and fall as ecosystem temperature changes from cold to warm (or the reverse)

• Ocean currents

• Plays a major role in modifying conditions around the earth that can affect where certain climates are located

• As the sun warms water near the equator, winds, salinity differences, and earth’s rotation sets ocean water in motion

• Ex. northern hemisphere: gulf stream carries sun-warmed water along the East Coast of the US as far as UK → warm water displaces the colder denser water in the polar regions → moves south to be rewarmed by the equatorial sun

• Ocean conveyor belt moves cold water in the depths of the Pacific Ocean while creating major upwellings in other areas of the Pacific