Ecosystem Ecology and Biomes

Ecosystem Ecology and Biomes Chapter 3

Ecosystems • Ecosystem: a particular location on Earth distinguished by a specific mix of interacting biotic and abiotic components • For Example • An example of an ecosystem is a Forest. • Its biotic components are its trees, wildflowers, birds, mammals, insects, fungi, bacteria • Its abiotic components are sunlight, temperature, soil, water, pH, and nutrients • An ecosystem’s biodiversity is represented by all of the living organisms in that ecosystem. • Each ecosystem has components that distinguish it from other ecosystems. • Biotic and abiotic components interact with one another.

Ecosystems Twin Lakes, CA Serengeti Plain of Africa

Ecosystem Ecologists • An ecosystem ecologists is a person who studies… • the biotic and abiotic components that define an ecosystem • and the processes that move energy and matter within it • Why is this an important job? • Their work provides us an understanding of how ecosystems function • and from their observations/data, ecologists are able to understand how to protect and manage a particular ecosystem

Energy flows through ecosystems • Plants absorb energy from the Sun directly • That energy is distributed: Herbivores eat plants & carnivores eat herbivores • Is all of the energy in the consumed organism transferred to the consumer? • No; some energy is lost as heat  2nd law of thermodynamics

Class work 1/8/13 • In detail, describe how energy flows through ecosystems. • Ecosystems have many trophic levels through which energy flows. • Reference pages 51-53

Photosynthesis & Respiration • Where does nearly all of the energy that powers ecosystems come from? • The Sun is the source of solar energy (a form of kinetic energy) • Producers (plants, algae, & some bacteria) make their own food • They use solar energy to produce usable forms of energy (potential energy) • How? • Photosynthesis: Producers use solar energy to convert carbon dioxide and water into glucose and the waste product oxygen. • Glucose is a usable form of energy (potential energy) for a wide range of organisms. • Producers produce the oxygen we need to breathe. • Producers use the glucose they produce to store energy and build their structures. • Consumers can eat the tissues of producers to gain energy from the chemical energy stored in those tissues. • This is done by cellular respiration: a process that unlocks the chemical energy stored in the cells of organisms • Respiration is the opposite of photosynthesis • Cells convert glucose and oxygen into energy, carbon dioxide, and water. • Releases the energy an organism needs to live, grow, and reproduce (respiration will fuel an organism’s metabolism and growth) • All organisms, including producers, perform respiration.

Photosynthesis & Respiration • Producers both produce and consume oxygen. • Overall producers photosynthesize (produce oxygen) more than they respire (consume oxygen). • Net effect: an excess of oxygen in the atmosphere and an excess of carbon stored in the producer’s tissues

Trophic Levels • Trophic Levels: are successive levels of organisms consuming one another • Producers or autotrophs • Consumers or heterotrophs • Must obtain their energy by consuming other organisms • Fall into several different categories • Herbivores or primary consumers: heterotrophs that consume producers • Examples: Zebras, grasshoppers, tadpoles are all plant- and algae-eating animals • Carnivores: heterotrophs that consume other heterotrophs • Secondary consumers: carnivores that eat primary consumers • Examples: Lions, hawks, and rattlesnakes • Tertiary consumers: carnivores that eat secondary consumers • Rarer • An example: Bald eagle

Food Chain • In a food chain, energy moves from one trophic level to the next. • A food chain is the sequence of consumption from producers through tertiary consumers. • A food chain shows how energy and matter move through the trophic levels of an ecosystem. • The problem with a food chain is that species are rarely connected in such a simple, linear way. • An example of a simple food chain: Algae  Zooplankton  Fish  Eagle • What is a more realistic type of model? ...

A Food Web • Food webs take into account the complexity of nature. • They show how all species in an ecosystem are connected to one another  An important concept of Ecology • Not all organisms fit into a single trophic level. • For example an omnivore operates at several trophic levels. • A bear eats berries and fish; therfore a bear is an omnivore.

Food Chains Food Web

Scavengers, detritivores, and decomposers • Class work 1/9 • Take cornell notes for this section.

Scavengers, detritivores, and decomposers • Dead organisms and waste products are produced at each trophic level. These dead organisms and waste products are a source of food for other organisms. • Scavengers: carnivores that consume dead animals (i.e. vultures) • Detritivores: organisms that break down dead tissues and waste products into smaller particles (dung beetles) that are further processed by decomposers • Decomposers: fungi and bacteria that recycle nutrients (from dead tissues and waste products) back into the ecosystem • Without scavengers, detritivores, and decomposers the world would fill up with dead plants and animals. There would be no way of recycling organic matter and energy.

Fungi produce the enzymes necessary to decompose chemically complex substances that are found in wood.

Ecosystem Productivity Q. What determines the productivity of an ecosystem? A. The amount of energy available in an ecosystem determines how much life the ecosystem can support. The greater the productivity of an ecosystem, the higher the number of primary consumers that can be supported. Productivity measures the rate of energy production over a span of time. Scientists compare the productivity of different ecosystems by measuring each ecosystem’s net primary productivity (NPP). NPP = GPP – respiration by producers

Energy Transfer Efficiency and Trophic Pyramids • Energy transfer between trophic levels is of low efficiency (Low ecological efficiency). • What does this mean? • It means that only a small percentage, ≈ 5-20%, of the energy at any trophic level is available to be used at the next higher trophic level. • In result: Large biomass (biomass: the total mass of all living matter in a specific area) of producers, a lower biomass of primary consumers, and an even lower biomass of secondary consumers • The distribution of biomass and energy among trophic levels can be represented in a trophic pyramid.

Trophic Pyramid • Trophic pyramids look similar across ecosystems.

Matter and energy in the biosphere • Biosphere: the combination of all ecosystems on Earth; the region of our planet where life resides (from the deepest ocean bottom to the highest mountain peak = 12 miles distance) • Energy flows through the biosphere; enters as solar energy, and is emitted into space by Earth and its atmosphere • Matter does not enter or leave the biosphere but cycles within it in a variety of forms • Earth is an open system with respect to energy • Earth is a closed system with respect to matter

Biogeochemical cycles • Matter moves within and between ecosystems (biogeochemical cycles). • Biological, geological, and chemical processes are involved in the movement of matter. • Cycles assignment • due on Wed. 1/16

The Water Cycle • What do you already know about water? • It is essential to life. • Water performs many critical biological functions. • Water is the primary agent responsible for dissolving and transporting the chemical elements necessaryfor living organisms. • Many elements are taken up by organisms in dissolved form. • Many elements are carried by water to the ocean. • Water never leaves Earth • Earth is a closed system with respect to matter. • The water cycle can be defined as the movement of water through the biosphere.

The Water Cycle • 1. Sun’s heat causes water to evaporate from oceans, lakes, and soils. • 2. Water vapor that has entered the atmosphere cools and forms clouds (condensation). • 3. These clouds produce precipitation in the form of rain, snow, and hail; some rain falls into oceans and lakes; some rain falls on land. • 4. The precipitation falling on land may take 3 routes. • Evaporation or transpiration returns water to the atmosphere • Can be absorbed by the soil and percolate down into the groundwater (infiltration) • Can move as runoff (across land and into streams, rivers, leading to the ocean)

The Carbon Cycle • What do you already know about carbon? • Carbon is the most important element in living organisms. • Carbon is the basis of the long chains of organic molecules that form the membranes and walls of cells, constitute the backbone of proteins, and store energy for later use.

The Carbon Cycle • Six processes drive the carbon cycle. • Photosynthesis • Respiration • Exchange • Sedimentation and burial • Extraction • Combustion • In-class reading, 2nd column page 56. • In the absence of human disturbance, the exchange of carbon between Earth’s surface and atmosphere is in steady state.

The Nitrogen Cycle

Homework, 1/14/13 • Provide an example of how human activities can alter the water cycle (page 56). • How have human activities since the Industrial Revolution had a major influence on carbon cycling (page 56-57)? • What is the difference between resistance and resilience in an ecosystem (page 60)? • Quiz Tuesday, 1/15, will cover material from pages 49-61.

Biogeochemical Disturbances • A disturbance results in changes in population size or a change in the composition of a community. • A disturbance is an event caused by physical, chemical, or biological agents. • Examples of natural ecosystem disturbances include hurricanes, ice storms, tsunamis, tornadoes, volcanic eruptions, and forest fires. • Anthropogenic ecosystem disturbances include human settlements, clear-cutting forests, and air pollution. • Not every disturbance is a disaster.

After the disturbance • After a disturbance has occurred, an important question follows… • Will the ecosystem disturbed recover its original condition? • To answer this question, ecosystem ecologists look at the net primary productivity of all of the producers in the ecosystem. • If the net primary productivity stays the same after a disturbance then the productivity of the ecosystem is resistant. • Example of high resistance is when a disturbance influences populations and communities, but does not affect the flow of energy and matter in an ecosystem. • Possible scenario: A fire kills some plant species; but fire-adapted species benefit from nutrients released by dead plants; result: net primary productivity remains the same • If the flows of matter and energy in an ecosystem are affected by a disturbance, then it becomes a question of how quickly and/or completely the ecosystem will recover. • Resilience is the rate at which an ecosystem returns to its original state.

Weather vs. Climate • Weather: the short term conditions of the atmosphere in a local area • Examples: temperature, humidity, clouds, precipitation, wind speed, atmospheric pressure • Time scale: a few days to a number of days • Climate: the average weather that occurs in a given region over a long period • Time Scale: Decades • Can we make general observations about global, regional, and local climate? Yes.

Earth’s Atmosphere • Many global processes take place in the Earth’s Atmosphere. • Earth’s atmosphere consists of 5 layers of gases. • Troposphere • Stratosphere • Mesosphere • Thermosphere • Exosphere

Troposphere • Troposphere: the layer closest to the Earth’s surface • Extends 10 miles above Earth • Densest layer of the atmosphere • Layer where Earth’s weather occurs • Circulation and mixing of liquids and gases (nitrogen, oxygen, water vapor)

Stratosphere • Extends 10 – 31 miles above the Earth’s surface • Less dense than the troposphere due to its greater distance from Earth’s gravitational pull • Contains stratospheric ozone layer that provides critical protection for our planet • Layer absorbs most of the sun’s UV-B radiation and all of its UV-C radiation • UV radiation can cause cancer and DNA damage in organisms

Distribution of Heat and Precipitation • The processes that effect the distribution of heat and precipitation across the globe are the… • Unequal heating of Earth by the Sun • Atmospheric convection currents • Earth’s rotation and deflection of wind • Ocean currents

Unequal heating of Earth by the Sun • The warming of the surface of Earth by the Sun does not occur evenly across the planet. • Solar radiation is greatest in the tropics and least in the polar regions. • Albedo: the % of incoming sunlight reflected from a surface • The higher the albedo of a surface, the more solar energy it reflects and the less it absorbs.

Comparing Albedo Values Tropical region Snow covered polar region 10-20% albedo values 85-90% albedo values

Atmospheric convection currents • Uneven heating drives the circulation of air in the atmosphere. • What causes a series of convection currents to form around Earth? • Rising warm air and sinking cooler air • Figure 3.12, p. 62: The formation of circulation cells

The Formation of Circulation Cells • Start @ the Equator: the Sun heats the moist tropical air causing it to rise. • The rising air experiences adiabatic cooling, which causes water vapor to condense into rain and fall back to Earth. • Condensation of water vapor produces latent heat release. Air expands and rises farther up. • Warm air rises and displaces cooler, drier air above it to the north and south. • Cool, dry air sinks and experiences adiabatic heating. Reaches Earth’s surface as warm, dry air. This warm, dry air flows back toward Equator.

Biomes • Climate, the average weather that occurs in a given region over a long period, affects the distribution of ecosystems and species around the globe. • Biomes: terrestrial geographic regions • Scientists categorize biomes by • A particular combination of average annual temperature and annual precipitation • Distinctive plant growth forms that are adapted to that climate

Biomes • Terrestrial Biomes • 3 categories • Tundra & Boreal Forest Biomes • Temperate Biomes • Tropical Biomes • Aquatic Biomes • 2 categories • Freshwater Biomes • Marine Biomes

Ecosystem Ecology and Biomes