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Lecture 2 Ecosystems and Ecology

April 13, 2016

Ecosystems

Ecosystems, trophic levels and how energy flows through nature.

Pages: 41-57

How does the Earth support Life?

• 4 main spherical systems: Interacting with one another to act as Earth’s life-support system

•  Atmosphere •  Hydrosphere •  Geosphere •  Biosphere

Atmosphere (Air)

•  Thin membrane of air around the planet-made up of gases

•  Troposphere (inner layer) contains the air that we breathe and is 4-11 miles above sea level

•  99% of this air consists of N and O •  1% are the greenhouse gases (water

vapor, CO2 and CH4.

•  Stratosphere (11-31 miles)-contains the ozone layer (which filters 95% of the suns harmful UV radiation).

Hydrosphere & Geosphere

•  Consists of all the water on or near the earth’s surface.

•  Found in liquid water, ice or water vapor.

•  Ice in frozen soil layers is known as Permafrost

•  Oceans=97% of the earth’s water and cover about 71% of the globe.

•  Consists of the earth’s intensely hot core (molten lava), thick mantle (made of rock), and thin outer crust

•  Upper layers contain the non- renewable fossil fuels and minerals

•  And renewable soil chemicals (nutrients)

3 factors sustain the Earth’s life

•  (1) One-way flow of high quality energy •  From the sun----living things in their feeding interactions-----into the environment as low-quality

energy-to outer space as heat.

•  Greenhouse effect-solar energy interacting with CO2 in the troposphere, hence warming the troposphere

•  (2) Cycling of nutrient •  Fixed supply of nutrients on earth-continually need to be recycled

•  (3) Gravity •  Allows the planet to hold onto its atmosphere and enables the movement and cycling of chemicals

Ecology

•  The study on how organisms interact with one another and with their nonliving environment of matter and energy

•  Ecology is only one part of the overall study of life, matter, and the universe.

Organization of Life

•  An organism is an individual living thing. •  A single species of organism is one that is similar

enough to breed and produce healthy, fertile offspring.

•  A population includes all members of a species that live in the same area at the same time.

•  The biological community is made of all populations living and interacting in one area.

•  An ecosystem includes the biological community and its surrounding physical environment. •  Nonliving factors like soil,

precipitation, etc.

•  The biosphere is the part of Earth that supports life -- all ecosystems are found here.

Biosphere (All of the above)

•  Consists of parts of the atmosphere, hydrosphere and geosphere

•  Contains all living (biotic) and non-living (abiotic) organisms

•  Goal of environmental science- understand the interactions that occur within this thin layer of air, water, soil and organisms.

•  Each organism has a particular type of environment where it can survive. This is its habitat.

•  Habitats have a range of factors that influence the community that lives there – temperature, precipitation, water, soils, etc.

•  Some organisms have a single critical factor that plays the greatest role in determining its range.

•  Critical factors have a “Goldilocks Effect”, meaning there can be too much or too little of it.

Who Lives Where?

•  When the right level of an environmental factor is present, population levels will be growing or at their peak. This is the optimal range for that factor.

•  At the zone of physiologic stress, levels of the factor are too high or too low. The population barely survives.

•  At the zone of intolerance, the population dies out.

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•  A process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. The overall equation is:

6 H2O + 6 CO2 + solar energy à C6H12O6 + 6 O2

•  Other organisms, such as animals and fungi, cannot directly absorb sunlight. •  They rely on a process called cell respiration, which breaks down the complex

molecules found in organisms they ingest as a source of energy.

C6H12O6 + 6 O2 à 6 H2O + 6 CO2 + energy

•  Photosynthesis and cell respiration complement each other, forming the basis of the flow of energy and cycling of matter that makes up living ecosystems.

Photosynthesis & Cell Respiration

•  Remember from last lecture: As energy flows through an ecosystem, it obeys two Laws of Thermodynamics.

1.) Energy cannot be created or destroyed, it only changes form. •  This is also known as the Law of Conservation of Energy.

2.) During each transformation, some energy is given off in the form of heat.

•  This energy is no longer available to do work.

Energy Flows

•  In a biological community, energy can be tracked with a diagram called a food chain.

•  Movement of energy is shown by arrows.

Food Chains

•  Each trophic level within a food chain represents an organism with a separate energy source.

•  Producers absorb energy from the sun.

•  Consumers ingest other organisms. •  Primary→ Secondary → Tertiary

•  Decomposers break down dead or decaying matter.

Trophic Levels

Food Web

A food web shows all of the food chains within a community interwoven together.

Food Chain & Food Web

Food Chain •  Sequence of organisms, each of

which serves as a source of nutrients (energy) for the next organism.

•  Direct Predator-Prey Relationship •  Organisms are assigned to trophic

levels in a food chain

Food Web

•  Series of interconnected food chains within an ecosystem

•  Organisms are also assigned to trophic levels in food webs.

Producers

Consumers

Detritivores & Decomposers

•  Decomposers (Bacteria/fungi) break down organic detritus into simpler inorganic compounds

•  Detritivores (detritus feeders) feed on the wastes or dead bodies of other organisms •  Producers, consumers, and decomposers utilize chemical energy stored in organic

molecules(glucose). In most cells, this energy is released by aerobic respiration or cell respiration (uses O2 to convert glucose back into CO2 and H2O)

Decomposers &

Detritivores at Work

To Summarize :

•  Ecosystems and the biosphere are sustained through a combination of one-way energy flow from the sun through these systems

•  Nutrient cycling of key materials within the systems

*2 Key Principles of Sustainability!

To Summarize :

•  Ecosystems and the biosphere are sustained through a combination of one-way energy flow from the sun through these systems

•  Nutrient cycling of key materials within the systems

*2 Key Principles of Sustainability!

Food Chain à Trophic Levels

Food Chain à Trophic Levels

Usable energy decreases with each link

•  Each tropic level contains a certain amount of biomass (dry weight of all organic matter contained in its organism).

•  In chains or webs-chemical energy stored in biomass is transferred from one trophic level to another.

•  This causes a decrease in the amount of high-quality chemical energy available at each succeeding feeding level

•  90% of energy is lost with each transfer.

•  As stated by the Second Law of Thermodynamics, some energy is lost with each transformation.

•  The 10% rule is an estimation of how much energy is incorporated from one level of a food chain into the next.

Energy Pyramids

Matter in an Ecosystem •  Most life on Earth could not exist without a constant input of energy from the sun. •  Matter, however, only enters the earth in miniscule amounts daily.

•  The Earth is essentially a closed system to matter. •  A series of biogeochemical cycles exist to constantly recycle the essential elements of

life from one organism to another.

•  Hydrologic •  Carbon •  Nitrogen •  Phosphorus •  Sulfur cycles

The Hydrologic Cycle collects, purifies, and distributes

•  Heat from the sun causes water to evaporate from rivers, lakes, oceans, or the soil. (liquid à gas)

•  Plant roots extract water from the soil and release some of it into the atmosphere through their leaves, a process called transpiration.

•  As the evaporated water moves up into the atmosphere, it loses heat and condenses into clouds. (gas à liquid)

•  The water then returns to the Earth as precipitation; rain, snow, or ice. •  Some of that water will form runoff, moving towards lower elevations and collecting into

another body of surface water.

•  The rest of the water soaks into the soil, a process called infiltration.

Water’s Unique Properties •  Is held together by H-bonds

•  Exists as a liquid over a wide temperature range •  Stores a large amount of heat

•  Requires a large amount of energy to be evaporated •  Dissolves a variety of compounds

•  Filter’s some of the UV rays from the sun •  Expands when freezes

•  Exists in all 3 phases on the Earth’s surface

The Water Cycle

Hydrologic Cycle

• Humans alter the water cycle in three ways: •  Withdrawing freshwater at faster rates than nature can replenish it. •  Clearing vegetation which increases runoff and decreases replenishment of

groundwater supplies.

•  Draining wetlands which interferes with flood control.

The Carbon Cycle

•  Carbon is the basic building block of carbs, fats, proteins, DNA and other organic compounds necessary for life.

•  Carbon circulates through the biosphere, hydrosphere and atmosphere •  Based on CO2 gas and is a key component in the atmosphere’s thermostat.

•  If the carbon cycle removes too much CO2 from the atmosphere it will get cooler; If it generates too much CO2 it will get warmer.

•  Even slight changes in this cycle can affect the earth’s climate and ultimately determine the types of life that can exist in various places.

•  Primary producers remove CO2 from the atmosphere or water and consumers and decomposers circulate carbon in the biosphere.

The Carbon Cycle

The Nitrogen Cycle-Bacteria in Action

•  N2 gas which makes up 78% of the atmosphere, cannot be used directly by most living organisms.

•  Nitrogen-fixing bacteria convert N2 into compounds that are useful nutrients for plants and animals.

•  Nitrite (NO2-)

•  Nitrate (NO3-) •  Ammonia (NH3)

The Nitrogen Cycle-Bacteria in Action

•  The Nitrogen Cycle includes these steps: •  Specialized bacteria convert gaseous N to ammonia in nitrogen fixation. •  Specialized bacteria convert ammonia in the soil to nitrite and nitrate ions; the latter is used

by plants as a nutrient. This process is nitrification.

•  Decomposer bacteria covert detritus into ammonia and water-soluble salts in ammonification.

•  In denitrification, anaerobic bacteria in soggy soil and bottom sediments of water areas covert NH3 and NH4 back into nitrite and nitrate ions, then into N2 gas and nitrous oxide gas, which are released into the atmosphere.

The Nitrogen Cycle-Bacteria in Action

•  Human activities have more than doubled the annual release of N from the land into the rest of the environment.

•  Most from the increased use of inorganic fertilizers to grow crops. This excessive input of nitrogen into the air and water contributes to pollution and other problems.

The Nitrogen Cycle-Bacteria

in Action

The Phosphorus Cycle

•  Phosphorus circulates through water, Earth’s crust and living organisms. It does not cycle through the atmosphere.

•  The major reserves of P on Earth are rock formations and ocean bottom sediments. •  P is transferred by food webs and is an important component of many biological

molecules.

•  P is often limiting factor in plant growth •  Human activity removes phosphate from the earth to make fertilizer and reduces

phosphate levels in tropical soils by clearing forests. Phosphate rich runoff from the land can produce huge populations of algae, which can upset chemical cycling.

The Phosphorus

Cycle

The Sulfur Cycle

•  Much of the Earth’s sulfur is stored underground in rocks and minerals •  Hydrogen sulfide (H2S) is released from volcanoes and by anaerobic decomposition of

organic matter in bogs ands swamps

•  Humans have been increasing atmospheric sulfur dioxide by burning, refining, and converting sulfur-containing fuels and mineral ores into free metals.

The Sulfur Cycle

Main Themes

•  Life is sustained by the flow of energy from the sun through the biosphere, the cycling nutrients within the biosphere and gravity.

•  Some organisms produce the nutrients they need, some survive by consuming other organisms and others recycle nutrients back to producers

•  Human activities are altering the flow of energy through food chains and webs, and the cycling of nutrients within ecosystems and the biosphere.

Chapter 4

Evolution & Biodiversity Chapter 4 (pgs. 62-68; 70-74)

•  Why do coniferous trees have such a wider range (3,5,6,7,8) than broadleaf deciduous trees (8)?

•  Why are broadleaf trees more prevalent than coniferous trees in areas where they can both survive?

Adaptations •  The range of tolerance for a species is largely defined by the presence of physical,

behavioral, or physiologic adaptations.

•  Physical adaptations are structural differences in coloration, body shape, musculature, etc. •  Behavioral adaptations include migration, or marking a territory. •  Physiologic adaptations, such as skin tanning, occur at the cell or tissue level in an

organism.

The  gorilla  is  adapted  for   living  and  feeding  on  the   ground,  while   chimpanzees  gather  food   from  trees.  

•  All of the unique adaptations found in different organisms are the result of evolution -- small, advantageous mutations that have accumulated over countless generations.

•  Natural Selection describes the process where individuals with better genes survive and reproduce more successfully, while those with weaker genes do not.

•  The primary source of this genetic variety is random mutations. These are small changes of DNA.

•  Usually these changes produce no effects or bad ones, but occasionally, they can be beneficial.

Evolution

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•  Evolutionists will cite three categories of evidence in support of the theory.

•  Physical Similarities •  Most animals have similar bones in their limbs (fins, arms,

wings).

•  These similarities can also be found between living species and fossils.

•  Comparing DNA •  Chimpanzees, bonobos, and humans share about 99% of the

same DNA.

•  Vestigial Structures •  Still exist in the body but are no longer needed •  Ex: Appendix, wisdom teeth

Natural Selection

Biological Evolution…Natural Selection •  Fossils reveal the history of life

•  Biologic evolution is the process whereby life changes over time through changes in the genes of populations in succeeding generations.

•  The theory of Evolution by natural selection is a scientific explanation of how the process of evolution takes place

•  Natural selection-is the process in which individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits.

Limits and Incorrect Ideas of Natural Selection

Limits •  Organisms can adapt to a change in

environmental conditions only if the necessary genetic traits are already present in a population’s gene pool.

•  Even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity.

Incorrect Ideas •  “Survival of the Fittest” meaning

survival of the strongest. •  Organisms develop certain traits

because they need them •  Evolution by natural selection involves

some grand plan of nature in which species become more perfectly adapted.

•  Evolution is an very slow process.

•  Current life on Earth represents billions of years of small mutations and natural selection.

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Speciation •  Over a long enough period of time, enough mutations occur that a new species emerges. •  When a population splits and become two different species, it is called divergent

speciation.

•  Chimpanzees and bonobos are very closely related primates, with only a few differences between the species.

•  They likely diverged during a severe drought millions of years ago.

Encouraging Natural Selection •  Four ecological factors will “encourage” natural selection to favor certain individuals in a

population.

•  Speciation is more likely to occur. •  Physiological stress, inappropriate levels of a critical environmental factor. •  Moisture, Light, pH

•  Predation, when one organism is hunted and killed by another. •  Competition, the result of other organisms attempting to use same resources. •  Sexual Selection occurs when the female (usually) responds to specific behaviors or

physical traits.

•  Convergent speciation can occur when natural selection favors unrelated organisms to evolve to look similar. (mimicry)

Preying  Mantis  Mantis  Fly  

Artificial Selection •  The selective breeding of organisms by humans for characteristics desirable to

them. (dogs, horses, cattle, cows, etc.)

•  Evolution has produced a tremendous amount of biodiversity on Earth. •  Biodiversity is defined as the number of different species within an ecosystem or

area.

•  The number of species is unknown. •  About 1.5 million have been identified. •  A recent study estimates 8.7 million exist currently.

Biodiversity

•  The majority of known species are insects, followed by fungi and bacteria.

The Taxonomic Naming System •  With the tremendous diversity of living organisms, a system was devised to organize

them based on their interrelatedness.

•  Domain •  Kingdom •  Phylum •  Class •  Order •  Family •  Genus •  Species

Human Classification Taxon Reason

Domain Eukarya Cells have nuclei and organelles (eukaryote).

Kingdom Animalia Multicellular. Unable to produce own food (heterotrophic).

Phylum Chordata Have a nerve cord along the back.

Class Mammalia Warm-blooded, gives birth to live young, has hair.

Order Primates Forward-facing eyes, enlarged brains, vertical posture.

Family Hominidae Capacity for language, culture, empathy.

�  The  final  two  taxa,  genus  and  species,  are  used  to  define  the  species’  scientific  name.   �  Homo  sapiens  

�  Italicized  or  underlined   �  Genus  capitalized,  species  lower-­‐case.  

•  The scientific naming system is important, as many species have multiple common names.

•  The cougar holds the Guinness world record for number of common names, with 40 in English alone! •  Cougar, catamount, painter, panther, ghost

cat, puma, shadow cat, mountain lion, deer tiger, devil cat, sneak cat, plain lion, fire cat, mountain screamer, Florida panther, silver lion……

Puma  concolor

•  Two animals with many classification levels in common are considered very closely related – they diverged recently.

•  Wolves and dogs share the same domain, kingdom, phylum, class, order, and family.

Canis lupus lupus European Wolf

Canis familiaris Domesticated dog

Major Components of

Biodiversity

Major Components of Biodiversity

•  Species diversity, or the number and variety of the species present in any biological community •  Species diversity estimates range from 8 million to 100 million.

•  Genetic diversity, which is the variety of genes found in a population or in a species. •  Ecosystem diversity-the earth’s variety of deserts, grasslands, forests,

mountains, oceans, lakes, rivers, and wetlands. •  Functional diversity-variety of processes such as energy flow and matter

cycling occurring within ecosystems

Examples of Genetic Diversity

Ecosystems Diversity

Eventually all species will become extinct

•  Biological extinction is the process by which an entire species ceases to exist •  Local extinction occurs when a population of a species becomes extinct over a large

region but not globally.

•  Endemic species are found in only one area and are thus especially vulnerable to extinction

•  Background extinction has occurred over most of the Earth’s history •  Extinction occurring at a low rate

There have been several mass extinctions of life on the Earth

•  Mass Extinction is a significant rise in extinction rates above the background level, in which large groups of species are wiped out.

•  Fossil and geological evidence indicate that there ~been five mass extinctions during the past 500 million years.

•  Mass extinctions have been followed by an increase in species diversity as new species have arisen to occupy new habitats or to exploit newly available resources.

•  There is growing evidence that we are experiencing the beginning of a new mass extinction, with much of the increase in extinctions and loss of biodiversity due to human activities.

Ecological Niche

•  An ecological niche is a species way of life in an ecosystem, everything that affects its survival and reproduction.

•  Niche is different from habitat, which is the place where an organism lives. •  Generalist species have broad niches •  They can live in many different places •  They can eat a variety of foods and tolerate a wide range of environments •  Flies, cockroaches, rats and humans are generalists.

Ecological Niche

•  Specialist species have narrow niches: •  They live only in very specific environments. •  This makes them more prone to extinction when environmental conditions

change.

•  If the environment is constant, specialists have fewer competitors. •  China’s Giant Panda is a specialist with a specialized diet of mostly bamboo.

Specialized Feeding Niches of Various Bird Species in a Coastal Wetland

Species can play 4 major roles within Ecosystems

•  Niches can be classified further in terms of specific roles that certain species play within ecosystems. A species can be described as Native, Non-native, Indicator, or Keystone.

•  Native species are those that normally live and thrive in a particular ecosystem •  Non-native species (invasive, alien, exotic) are those that migrate into, or are

deliberately or accidentally introduced into, an ecosystem

•  Nonnative species can threaten native species

Indicator species serve as biological smoke alarms

•  Indicator species provide early warnings of damage to a community or an ecosystem •  Birds are excellent biological

indicators because they are found almost everywhere and are affected quickly by environmental changes, such as loss of fragmentation of their habitats and introduction of chemical pesticides.

Many factors can affect frogs and other amphibians at various points in their life cycles

•  Habitat Loss/ Fragmentation

•  Prolonged drought •  Increases in UV

radiation

•  Parasites

•  Pollution •  Viral and fungal

diseases

•  Climate Change •  Overhunting

Keystone Species

•  Critical role in their ecosystems •  A species whose roles have a large effect on the types and abundance of

others in an ecosystem, even though they may exist in relatively limited numbers in their ecosystems.

•  Examples are the wolf, leopard, lion, shark species, and the American Alligator.

Community Interactions and Relationships

Chapter 5

(Pages:80-85)

•  How quickly populations grow and the maximum size they attain are often the result of interactions with other populations of organisms.

•  One of the most basic interactions is predator-prey, where one organism consumes the other.

Community Interactions

•  Competition, where organisms and populations compete for resources, is another common interaction.

•  Water, food, territory, mates. •  When the competition occurs within members of the same species, it is called

intraspecific.

•  When the competition occurs between different species, it is called interspecific.

•  Some organisms have developed adaptations to avoid directly competing with their own species.

•  Known as resource partitioning-occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places.

•  Plants will send their seeds far away to avoid sharing the same soil.

•  Wolves mark and occupy a territory so they have enough hunting area.

•  Adult monarch butterflies and their caterpillars each utilize a different part of plants.

•  The closest relationships of all are symbiotic. These involve a lot of close contact between two species.

•  When the relationship benefits both organisms, it is called mutualism. •  When one organism benefits while the other is unaffected, it is called

commensalism.

•  When one organism benefits at the expense of the other, it is called parasitism.

Symbiosis

•  Barnacles create homes by attaching themselves to whales. The whales are unaffected.

•  Clownfish have a mucus coating that allows them to live in sea anemones. Their presence attracts other fish for the anemone to eat.

•  As bison walk through grass, insects are disturbed and fly away. They are eaten by cowbirds.

•  Ostriches and gazelles feed next to each other. Ostriches have excellent eyesight, while gazelles have stronger senses of hearing and smell.

•  Mistletoe extracts water and nutrients from the spruce tree directly.

Main Themes

•  Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection)

•  Human activities are degrading the earths vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species

•  Each species plays a specific ecological role in the ecosystem where it is found.